Concepts in Engineering

8/3/2019 Concepts in Engineering

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ABSORBENT

A material which, due to an affinity for certain substances, extracts one or more such

substances from a liquid or gaseous medium with which it contacts and which changes

physically or chemically, or both, during the process. Calcium chloride is an example of a

solid absorbent, while solutions of lithium chloride, lithium bromide, and ethylene glycols are

liquid absorbents.

ACID CONDITION IN SYSTEM

Condition in which refrigerant or oil in a system, is mixed with vapor and fluids that areacidic in nature.

ACID RAIN

Atmospheric precipitation with an pH below 5.6 to 5.7.

ACIDIFIED

The addition of an acid (usually nitric or sulfuric) to a sample to lower the pH below 2.0. The

purpose of the acidification is to "fix" a sample so it will not change until it is analyzed.

ACTUATOR

The portion of a regulating valve, which converts mechanical, fluid, thermal, or electrical

energy; into mechanical motion to open or close the valve seats or other such devices.

What is resilience?

The total strain energy stored in the body is generally known as resilience.

State proof resilience

The maximum strain energy that can be stored in a material within elastic limit is known as

proof resilience.

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Define modulus of resilience

It is the proof resilience of the material per unit volume Modulus of resilience = Proof

resilience / Volume of the body

Airfoils And Airflow Phenomena

The character of airflow basically depends on the shape of the airfoil section and on the phenomena

occurring at the boundary layer, which is the thin layer of air adjacent to a solid surface such as an

airfoil over which air is flowing and which is distinguished from the main airflow by distinctive flowcharacteristics of its own set up by friction. The flow in the boundary layer (Fig.1) where the

thickness of the layer is shown greatly exaggerated may be laminar or turbulent. In laminar flow the

velocity distribution in the layer shows a steady increase from zero at the surface of the airfoil: more

particularly, the wing of an aircraft: to a maximum corresponding to the velocity of the main airflow.

An airfoil is a device which gets a necessary reaction from air moving over its surface. When an

airfoil is moved through the air, it is capable of producing lift. For e.g.: Wings, horizontal tail

surfaces, vertical tails surfaces, and propellers. The flow is relatively smooth and moves in layers

parallel to the surface; hence the term laminar. In turbulent flow, the fairly regular motion of the

laminar boundary layer is destroyed. The boundary layer undergoes transition; it becomes thicker

and is characterized by large random motions (turbulence). These effects may give rise to separation,

a term which denotes that the flow in the boundary layer detaches itself from the surface of the wing

at the separation point and that immediately adjacent to the surface, flow even occurs in a direction

opposite to the direction of the main flow (Fig.2).

The airflow around the wing occurs at the stagnation point and is laminar up to the transition point,

where turbulence sets in the latter point is located near the point of minimum pressure,

approximately where the wing has its greatest thickness. Normally the turbulent boundary layer

separates itself from the trailing edge of the wing, where eddies develop. If this separation occurs too

far forward toward the leading edge, there is serious loss of lift and an increase in drag.

This is liable to happen when the angle of attack exceeds the critical value known as the stalling

angle or when the airspeed becomes too low. Some aircraft, especially sports planes, are equippedwith a stall-warning device which may consist of a short triangular plate or a length of wire fitted to

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the leading edge of the wing (Fig.3). When the angle of attack becomes dangerously large, separation

of the airflow commences at this plate or wire. There is an immediate loss of lift, which warns the

pilot that he is approaching the stalling angle.

Regions of the wing where laminar separation is liable to occur may be provided with device for

producing turbulence (Fig.4). The resulting turbulent flow adheres better to the surface than the

laminar flow and premature separation is thus prevented. Such devices may, for example, take the

form of small projecting plates which break up the laminar flow. Swept wings are provided with so-

called fences, which are plates or vanes placed parallel to the main airflow and prevent flow (and

separation) in the direction from wing root to tip, this subsidiary flow being promoted by the sweep

of the wing.

A similar effect is obtained by forming the leading edge of the wings with sawtooth notches (Fig.6).

At the tail of the aircraft, interference of the boundary layers of the horizontal and the vertical

stabilizers produces interference drag. To diminish this, the so-called T tail has been developed, in

which the horizontal surfaces are placed at the top of the vertical fin (Fig.7), while the junction of

these components is provided with a fairing i.e., a streamlined casting designed to reduce drag.

Steering an aircraft in three directions is effected by means of: the rudder, which guides the aircraftin the horizontal plane, the elevator, which controls the pitch i.e., makes the tail go up or down, and

the ailerons which control the rolling motion of the aircraft by their differential rotation. The rudder

is attached to a vertical stabilizer, while the ailerons are set at the trailing edges of the wings (Fig.5).

Sometimes the horizontal and vertical stabilizers are not provided with separately movable

attachments i.e. elevator and rudder, but can each be moved as a whole so as to alter the angle of

attack. The trailing edge of the rudder may be provided with a small subsidiary rudder called a

trimming tab (Fig.7) by means of which the pilot adjusts the trim of the aircraft i.e., the condition of

static balance in pitch during rectilinear flight, with the main control surfaces seeking their neutral

positions.

Further adjustments are achieved by means of flaps, these being control surfaces which serve to

control the speed by increasing the drag and thus acting as a brake or to increase the lift or aid in

recovery from a dive. The slat (Fig.8) is a movable auxiliary airfoil running along the leading edge of

a wing; in a normal flight it is contact with the latter, but it can be lifted away to form a slot at certain

angles of attack, so that air flows through the slot and reenergizes the boundary layer on the low-

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pressure upper surface of the wing. The plain wing flap (Fig.9) increases the curvature of the wing,

with the result that the lift is improved and the angle of attack at which separation occurs is

increased, so that the airspeed can be reduced without stalling.

This is important in connection with the take off and landing of high-speed aircraft. An improved

form is the slotted flap (Fig.8); the flow of air through the slot between the flap and the wing gives a

further increase in lift without separation of the boundary layer. In contrast with other types of flap

mentioned, the split flap (Fig.10) serves to reduce the pressure on the suction face of the wing,

whereby an increase in the lift is likewise achieved. Landing flaps (Fig.9) serve primarily to slow

down the aircraft for landing; they breakdown the airflow around the aircraft and thus function as

brakes. Such flaps are sometimes called spoilers, more particularly when installed on the underside

of the wing.

A special dynamic device for boundary-layer control is the jet flap which consists of a flat jet of air

expelled at high velocity from a narrow slot at the trailing edge of the wing and which exercises an

action similar to that of an ordinary flap. The same principle is embodied in the blown flap (Fig.11),

an ordinary trailing edge flap in which separation from the upper surface is delayed by blowing. This

principle is also applied to elevators (Fig.12). Another modern control method, still in progress stage,

consists in keeping the airflow laminar by sucking in air from the boundary layer through numerous

small holes.

Aerosols

An aerosol is a system consisting of very finely divided liquid or solid articles of

dispersed in and filled by gas. In recent years aerosols have become well known products

discharged from spray dispensers, and the term aerosol has, in popular speech also come

to means the dispenser itself i.e. a pressurized container made of metal or glass and

provided with a discharge valve, which may be a spray valve or a foam valve. It is filled

with the product to be sprayed and the propellant gas under pressure.

The aerosol can was invented in 1926 by Erik Rotheim. He invented the first aerosol can

and valve that could hold and dispense products and propellant systems. This was the

forerunner of the modern aerosol can and valve. The patent was sold to a US company for

100,000 Norwegian kroners, but it wasn't until 1941 that it was first put to good use byAmericans Lyle Goodhue and William Sullivan. They turned it into an instrument for the

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US military to fight the malaria mosquito in the Pacific during World War II. Aerosol

spray products have three major parts; the can, the valve and the actuator or button.

The term aerosol derives from the fact that matter floating in air is a suspension i.e. a

mixture in which solid or liquid or combined solid-liquid particles are suspended in a

fluid. To differentiate suspensions from true solutions, the term sol evolved originally

meant to cover dispersions of tiny particles in a liquid. With studies of dispersions in air,

the term aerosol evolved and now embraces liquid droplets, solid particles, and

combinations of these. An aerosol may come from sources as various as a volcano or an

aerosol can.

The product to be dispersed as an aerosol may have the liquefied propellant mixed with it

in the form of a solution (Fig.1). Alternatively, the propellant may be present as a separategaseous phase in the dispenser, in which it does not mingle with the product (two-phase

system: Fig.2).

An example of the first type is afforded by hair spray. The spray or lacquer, usually

dissolved in alcohol, is completely miscible with the liquefied propellant. When the valve

button on the dispenser is pressed, the propellant vaporizes immediately, and its pressure

forces the liquid out of the nozzle. The liquid i.e., the lacquer solution is discharged as a

fine mist. The most commonly employed propellants are chlorinated hydrocarbons,

butane, propane, isobutane, vinyl chloride and nitrogen. Nitrogen is used particularly for

products that on no account be contaminated in flavor or smell e.g., toothpaste packaged

in aerosol dispensers.Aerosol toothpaste is an example of the second category of aerosol systems particularly,

the two-phase system in which the propellant gas forms a separate layer over the product

to be discharged. The dispenser is half milled with nitrogen or some other suitable gas and

half with the product. The pressure in the dispenser is about 6 to 8 atm. (90 to 120 lb./in2). Nitrogen can also be used as the propellant for foods packaged in aerosol form e.g.,

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cheese spreads, malt extracts, vitamin preparations, syrups, pudding sauces, whipped

cream.

Filling an aerosol dispenser at the factory is a simple operation (Fig.3: stages 1 to 5). First

the product is introduced into the dispenser. This is done by a pneumatic filling machine.Then the aerosol valve is placed on the dispenser. In the next stage the valve is force-

fitted under high pressure into the neck of the dispenser, so that a strong gastight seal is

formed between the latter and the valve unit. The propellant gas is now forced into the

dispenser. Finally, the dispenser is immersed in water to test it for possible leakage, which

is manifested by escaping bubbles of gas.

Aerosols are coming into increasingly widespread use in industry. They are used for the

disinfection of milk tanks. For this purpose a spraying device is used which draws thedisinfectant solution by suction from a container and disperses it as an aerosol by means

of two atomizing discs. These discs rotate, and their centrifugal action sets up a suction

which draws the disinfectant forward through the hollow shaft of the motor.

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To make the aerosol mist flow in the desired direction, a second air stream is needed. A

turbine is installed behind the motor sucks in air, which flows along the motor and

emerges from the annular aperture around the atomizing discs. This stream of air carriesalong the aerosol particles of disinfectant (Fig.5).

Anaesthetic Apparatus

Anaesthesia means loss of feeling or sensation, so that no pain is felt. In surgery this

result is obtained by using an anaesthetic. A distinction is to be made between general

anaesthesia i.e. total unconsciousness and local anaesthesia i.e. only one area of the body

is deprived sensation.

The beginnings of modern anesthetic equipment date back to Morton's inhalation flagon

in 1846. The numerous devices developed and introduced subsequently can be divided

into four groups. Simple ether and chloroform masks for open inhalation anesthesia, from

Simpson (1847) to Brown (1928). Vapour inhalators according to the draw over principle

of Snow (1847) up to the Oxford vaporizer (1941). Closed or half-closed inhalation

equipment for ether or chloroform with to and fro breathing, from Clover (1877) to

Ombredanne (1908).

Equipment for anaesthesia with nitrous oxide. From 1868 onwards this led to the

incorporation of gas bottles in anaesthetic equipment and between 1885 and 1890 to the

construction of mixing-valves for nitrous oxide and oxygen. In addition, reducing valves,

flow meters and vaporizers were developed. The first anaesthetic apparatus with circle

system and CO2-absorber was constructed in 1925 by the Drager factory in Lubeck.Sudeck and Schmidt introduced this technique of anaesthesia in the university hospital of

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Hamburg-Eppendorf between 1920 and 1925.

General anaesthesia can be produced in separate ways, including intravenous injection

with thiopental sodium or other agents. The older and still most widely used method,

however is by inhalation of a gaseous or volatile anaesthetic. Early anaesthetics were

either, nitrous oxide and chloroform.

At the present time a range of other agents are available. In modern surgery, especially for

major operations, a combination of two or more anaesthetic agents may be employed, the

gaseous or volatile anaesthetic being administered by means of a special apparatus, which

enables the various agents to be accurately proportioned and controlled, so as to minimize

the risk of overdosing.

Also includes in the circuit are a breathing bag, an inlet attachment for supplying fresh air,

an evaporator for volatile anaesthetic agents e.g., diethyl ether should these be used, and a

cartridge containing an absorbent for the carbon dioxide contained in the exhaled air. This

air may be recycled through the breathing circuit or may, in other varieties of anaesthetic

apparatus, be discharged from the apparatus.

The anaesthetic is managed to the patient either through a face mask or through a tube

introduced into the trachea (windpipe), the latter method now being considered more safer

and more effective. In apparatus mentioned, the anaesthetic is nitrous oxide gas used in

conjunction with the vapour of a volatile anaesthetic. Before having this mixture

administered to him by inhalation the patient is usually given a preliminary anaesthetic by

intravenous administration.

Centrifugal Casting

Centrifugal casting consists of a number of processes in which the centrifugal force set up

by the rotation of a part of the casting installation is utilized to shape the casting, fill the

mold, and help solidify and strengthen the metal. There is a difference between Vertical

centrifugal casting (Fig.1) and horizontal centrifugal casting. The first mentioned processis essentially a pressure-casting technique employing rotation about a vertical axis. It

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produces good filling of the mold, high dimensional accuracy, and a high strength dense

structure of the casting metal. This method is used for casting of components that are too

difficult to produce satisfactorily by static casting methods because their sections are too

thin or for other reasons: e.g., gears, piston rings, impellers, propellers, bushings andrailway wheels. Horizontal centrifugal casting is used mainly for making long hollow

castings, such as pipes, gun barrels, sleeves, etc.

The mold rotates at high speed about a horizontal axis, the molten metal being fed into the

interior of the mold and distributed around it by centrifugal action. Rotation is continued

until solidification is complete. The external diameter of the casting corresponds to the

internal diameter of the mold. The internal diameter of the casting can, however, be varied

by appropriately proportioning the amount and feed rate of the casting metal. Anadvantage of the centrifugal process is that it produces a sounder and more uniform

casting than static means. The mold is usually made of steel or cast iron. Non-metallic

linings may be used.

An important application of horizontal centrifugal casting is the manufacture of pipes,

especially cast-iron pipes. It provides an economical method capable of an advanced

degree of mechanization. The two main methods of centrifugal casting are : In a water-

cooled mold by the Briede-de Lavaud process (Fig.2) and in a sand lined mold by

Moore’s process (Fig.3). For the manufacture of spigot pipes, a sand core is inserted at the

end of the mold and is subsequently destroyed when the pipe is demolded. The first

mentioned method employs a slightly inclined mold which can move longitudinally.

The molten iron is introduced into the mold through a long duct from a tilting ladle

containing the correct amount of casting metal to form the pipe. When the mold has

reached a certain speed of rotation, the molten iron is admitted to it, and mold is moved

slowly forwards (Fig.2) while the feed duct remains stationary, so that uniform

distribution of the metal along the mold is achieved. Moore’s method uses a rotating mold

with a sand lining, which protects the metal shell of the mold so that water cooling is not

necessary. The sand itself is applied to the mold wall and compacted by centrifugal

action. The inlet duct is short because, with a sand lining, solidification of the casting

takes a relatively long time (no rapid cooling); proper filling of the mold is thus ensured.

This process has the advantage of not requiring a wide range of molds of different

diameters, since any desired pipe diameter can be produced simply by varying the

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thickness of the sand lining.

Centrifugal methods are also used for the production of composite castings. Centrifugal

casting as are categorized into Centrifugal Casting, Semi-Centrifugal Casting andCentrifuging. In centrifugal casting, a permanent mold is rotated about its axis at high

speeds (300 to 3000 rpm) as the molten metal is poured. The molten metal is centrifugally

thrown towards the inside mold wall, where it solidifies after cooling. The casting is

usually a fine grain casting with a very fine-grained outer diameter, which is resistant to

atmospheric corrosion, a typical situation with pipes. The inside diameter has more

impurities and inclusions, which can be machined away. Only cylindrical shapes can be

produced with this process. Size limits are upto 3 m (10 feet) diameter and 15 m (50 feet)length. Wall thickness can be 2.5 mm to 125 mm (0.1 - 5.0 in). The tolerances that can be

held on the outer diameter can be as good as 2.5 mm (0.1 in) and on the ID can be 3.8 mm

(0.15 in). The surface finish ranges from 2.5 mm to 12.5 mm (0.1 - 0.5 in) rms. Typical

materials that can be cast with this process are iron, steel, stainless steels, and alloys of

aluminum, copper and nickel.

Two materials can be cast by introducing a second material during the process. Typical

parts made by this process are pipes, boilers, pressure vessels, flywheels, cylinder linersand other parts that are axi-symmetric. In Semi-Centrifugal Casting, the molds used can

be permanent or expendable, can be stacked as necessary. The rotational speeds are lower

than those used in centrifugal casting. The center axis of the part has inclusion defects as

well as porosity and thus is suitable only for parts where this can be machined away. This

process is used for making wheels, nozzles and similar parts where the axis of the part is

removed by subsequent machining. Centrifuging is used for forcing metal from a central

axis of the equipment into individual mold cavities that are placed on the circumference.This provides a means of increasing the filling pressure within each mold and allows for

reproduction of intricate details. This method is often used for the pouring of investment

casting pattern.

Composite Casting

Composite Casting refers to a large number of processes in which molten metal is cast on

to a solid metal component, so that the two subsequently form one integral unit. In this

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way the favorable mechanical or other technological properties of one metal can be

combined with those of another. For example, bearings may be made from an outer shell

of strong metal with a lining of special low-friction metal cast inside it, or a metal

possessing high strength may be given cast-on covering of corrosion-resistant metal, or anexpensive metal may be combined with a cheaper metal for economy.

The mechanical connection of the two metals can be made by means of interlocking

devices such as dovetailing, grooves, recesses, etc., which form a physical key, or by

shrink fitting or by bond established as a result of diffusion at the interface of the two

metals so that local interpenetration occurs. The bond may be further strengthened by heat

treatment (annealing) or by the interposition of special bonding layers of metal at the

junction.

Cutting and Machining of Metals

Some metal shaping processes are forging, rolling, extrusion, etc., that do not involve the

removal of metal by means of cutting tools. Many important shaping processes are based

on cutting and similar operations. The tools used are made of special steels (tool steels),

hard metals (Cemented carbide alloys), oxide ceramic materials, and diamonds.

The principles of the various methods are briefly outlined, without detailed descriptions of

the machines used for performing the shaping operations. For each of these methods a

whole range of tools has been developed, each type of tool being employed for a

particular purpose. In chiseling (Fig.1), the cutting edge of the tool is driven into the

surface of the workpiece by the action of blows. To ensure even and regular removal of

the chips it is essential to hold the chisel correctly and take care that it does not slip on the

metal surface or dig too deeply into it. Chiseling is used chiefly for cutting off and for theremoval of edges, burrs, fins, etc.

Machining operations like planing, shaping and slotting (Fig.2) are comparable to

chiseling, characterized by the removal of the chips in one direction, the tool being moved

to and fro or up and down in relation to the workpiece. In sawing (Fig.3) the removal of

metal is effected by a series of saw teeth. With power-driven band saws and circular saws,

cutting can be performed in continuous operation.

The shape, spacing and number of teeth vary greatly for different saws. Large diameter

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circular saws may have interchangeable teeth or interchangeable segments comprising a

number of teeth. Sawing is used mainly for cutting off and for cutting plate material of not

too great a thickness. Thick pieces of metal can, while still hot from the furnace, be cut

with hot sawing machines or with cutting discs. The latter achieve very high cutting rates,cutting being effected by melting of the metal due to frictional heating. Band-type cutting

devices are based on the same principle of heat generated at the cutting surface.

Filing is another important basic process (Fig.4). By using suitably shaped files it is

possible to cut metal to any desired shape. The actual cutting is performed by the teeth of

the file. Roughing out the shape is first done by means of coarse files, followed by

finishing with finer files. Files are available in great variety of shapes, sizes and grades.

They are classified and named according to sectional shape (e.g., half-round, square,triangular, round), length, and the relative fineness of cut of the teeth. With regard to

fineness, the following classes of file are distinguished: bastard, second-cut, smooth, dead

smooth. If there is only one series of parallel teeth, the file is known as a single-cut file. If

the first series is intersected by a second and finer series, so as to form diamond shaped

teeth, the file can also be called as double-cut.A broach (Fig.5) is a tapered tool provided with a series of cutting teeth which are lower

at one end of the tool than they are at the other. Broaching is mainly employed for

machining out holes or other internal surfaces, but can also be used for external surfaces

and for burnishing already-formed holes. The cut starts with the smaller teeth, which enter

the hole, and finishes with the larger teeth, which bring the hole to the finished size. Fig.5

shows an internal broach. Its cross-sectional shape may be round, rectangular, etc.,

depending on the desired shape of the hole. The broaching operation is performed by a

machine that pulls or pushes the broach through the workpiece.

Turning (Fig.6) is one of the most important machining processes. It is the process of reducing the diameter of material held in a lathe. The workpiece is attached to a driven

spindle and, while rotating, is brought into contact with a cutting tool. The position of the

tool in relation to the axis of rotation can be varied so as to cut the workpiece to the

desired shape. In longitudinal turning, the tool is moved parallel to the axis of the rotation,

so that cylindrical shapes are obtained.

A screw thread can be cut by a tool forming a spiral groove. In transverse turning, also

known as facing, and in forming, the tool is moved at right angles to the axis. Workpieces

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of any desired tapered or other axially symmetrical shape can be produced by suitable

combinations of longitudinal and transverse tool movements.

Turning tools are available in a wide range of shapes and types. The cheapest are made of

high carbon steel, hardened and tempered. Alloys known as high speed steels are used for

tools that can be operated at much higher cutting speeds. In tipped tools the cutting tip is

made of a special hard material. E.g., a cemented carbide, particularly tungsten carbide.

Drilling (Fig.7) is a rotary cutting operation for producing holes. The tool most widely

used for the purpose is the twist drill, provided with helical cutting edges, which rotates

and is fed forward into the material under pressure. The combination of rotary and feed

motion cuts away chips of the material, which are removed from the hole. For drilling a

hole in a solid workpiece, it is necessary first to make an indentation for the center of the

drill to revolve in. A tool called center punch is used for the purpose. It is advisable first

to use a smaller drill and then follow up with a drill of larger diameter.

Counterboring (Fig.8) is a process related to drilling and is employed to form a cylindrical

hole of large diameter at the end of an existing hole. E.g., to receive the head of a screw or

bolt. If the enlarged hole is formed with tapered sides, the process is called

countersinking.

Milling (Fig.9) is another important machining process, in which the workpiece is shaped

by means of a rotating cutter provided with a number of teeth. Usually the work is fed

against the teeth, the work-feed direction (in relation to the cutter) being longitudinal,

transverse or vertical. Milling machines are very versatile and can be used for a great

variety of work, including screw-thread cutting. In circular milling the cutter and the

workpiece are both rotated; in straight milling the cutter rotates while the workpiece

performs a straight feed motion

Grinding (Fig.10) is the operation in which an abrasive wheel or disc is used to remove

metal. It is employed as a finishing treatment to give parts already machined the necessary

precision by the removal of excess material. It is also employed as a machining process in

its own right – e.g., for roughly forged or cast parts or for the shaping of hard materials.

Centerless grinding is used for small cylindrical parts and is performed between two

grinding wheels. Grinding wheels are made from artificial abrasives, usually of the

aluminum oxide or the silicon carbide type, embedded in suitable bonding agents. Wheels

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are available in a vast number of different combinations of abrasive, grain size, type of

bond, hardness of bond, and structure.

Cam Mechanism

The transformation of one of the simple motions, such as rotation, into any other motions

is often conveniently accomplished by means of a cam mechanism. A cam mechanism

usually consists of two moving elements, the cam and the follower, mounted on a fixed

frame. Cam devices are versatile, and almost any arbitrarily-specified motion can be

obtained. In some instances, they offer the simplest and most compact way to transform

motions.

A cam may be defined as a machine element having a curved outline or a curved groove,

which, by its oscillation or rotation motion, gives a predetermined specified motion to

another element called the follower. The cam has a very important function in the

operation of many classes of machines, especially those of the automatic type, such as

printing presses, shoe machinery, textile machinery, gear-cutting machines, and screw

machines. In any class of machinery in which automatic control and accurate timing are

paramount, the cam is an indispensable part of mechanism.

A cam is a specially shaped component that serves to guide the motion of a component

called a follower. The cam has a rotary or linear motion. The most important advantage of

cam principle is that it is quite conveniently possible to introduce pauses of any desired

length into the motion. This advantage is widely used in machinery of all kinds, such as

packaging machines and many others. Using cams it is possible to perform simple sliding

movements or oscillatory. It can also precisely controlled movements of elaborate shape

Clutches

A clutch is any coupling that allows shafts or other rotating parts to be connected or

disconnected at will i.e., without the removal or refitting of any components. Clutches are

useful in devices that have two rotating shafts. In these devices, one shaft is typically

driven by a motor or pulley, and the other shaft drives another device. In a drill, for

instance, one shaft is driven by a motor, and the other drives a drill chuck. In the claw

clutch (Fig.1) one half of the clutch can slide on its shaft, so that the claws can be engaged

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or disengaged. This type of clutch can be engaged only when the shafts are stationary or

rotating at low speed.

The geared clutch (Fig.2) is widely used in machine tools and motor vehicles. The two

clutch bosses are each supported with external teeth which can mesh with a sleeve that

has corresponding internal teeth and can be slid over both bosses so as to establish a

positive connection between the two shafts. To permit engagement of the clutch while the

shafts are rotating, the sleeve and the shaft end to be coupled are respectively provided

with friction surfaces which are brought into contact with each other and thus equalize the

speed of the rotating parts before the teeth on the shaft and inside the sleeve are brought

into mesh. Friction clothes transmit power through contact friction surfaces on the two

halves to be connected.

Different types of friction clutch are illustrated in Fig.3. In the disc clutch (or plate

clutch), the cone clutch, the boss of the movable part slides in longitudinal grooves in the

shaft on which it is mounted. The movements for engaging and disengaging the clutch are

performed by the action of a lever whose forked ends fit into a circumferential recess in

the boss of the clutch plate or cone. The internal-expanding shoe-type clutch comprises an

outer shell attached to one shaft and two semicircular shoes which are mounted on arms

attached to a sliding sleeve on the other shaft and which can be brought internally into

contact with the shell. The forks of the clutch-operating lever engage with a recess on the

sliding sleeve.

A type of friction clutch commonly used in machine tools and other motor vehicles is the

multiple-disc clutch (Fig.4). It is based on the principle that a series of discs or plates

alternately connected to the driving and the driven shaft will increase the power-

transmitting capacity in proportion to the number of pairs of contact surfaces. In the form

of clutch illustrated in Fig.4 the boss mounted on the driving shaft is provided with

external teeth with which the internal teeth on a series of thin steel plates engage.

The outer shell of the clutch is mounted on the driven shaft and has internal teeth with

which the external teeth of a second series of plates (alternating with those of the first

series) likewise engage. When the clutch lever shifts a collar to the left, the plates are

pressed together and thus transmit power by friction. Multiple-disc clutches in machine

tools usually operate immersed in oil; those in motor vehicles are usually of the dry type.A magnetic clutch is a friction-disc clutch that is engaged by the energizing of a magnet

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coil, which attracts a set of steel friction discs and thus establishes the connection.A double-acting clutch based on this principle is illustrated in Fig.5. When the coil a is

energized, the discs b is compressed together by magnetic attraction, thereby connecting

the gear c to the shaft d. When the coil e is energized, the discs f is pressed together, so

that now power is transmitted from the shaft “d” to the gear g.

An automatic clutch is often installed between the driving shaft of a motor and the

machinery it drives. It does not allow the shaft to reach a predetermined speed before

engagement is effected and is especially useful in a case where the driven machinery

requires a high starting torque.

For such purposes a centrifugal clutch (Fig.1) may suitably be utilized. It comprises two

or more shoes which, when the driving shaft on which they are mounted has reached a

certain speed, overcome the pressure of restraining springs by the action of centrifugal

force and move outwards to press against the inner surface of the rim mounted on the

driven shaft. In this way the transmission of power to the driven shaft is gradually and

automatically increased, so that smooth engagement is effected.

The speed at which engagement takes place can be increased by fitting the clutch with

more power-restraining springs. When the shafts are not rotating, the shoes are retracted

and not in contact with the rim. Various other types of automatic clutch are likewise based

on the centrifugal principle. Freewheeling clutches drive in one direction only and permit

free movement when the speed of the driven shaft exceeds that of the driving shaft. In the

grip-roller type of freewheeling clutch (Fig.2) each roller is gripped, i.e., jammed, in the

wedge-shaped space as soon as the movement of the outer race in relation to the inner

race causes the roller to move into the shallower part of this space.

The friction produced at these faces will depend on the contact pressure exerted by thesprings. If the pressure is low, the friction will also be low, so that slip in the clutch will

occur at a low value of the torque. By means of a screw it is possible to increase the

spring pressure and therefore the friction, so that the clutch will be able to transmit a

greater torque without slipping. The torque can thus be adjusted to a predetermined value,

and the clutch can serve as a safety device against overloading of the driven machinery. A

simpler safety device for this purpose is the shear-bolt coupling (Fig.4). It comprises two

flanges connected by bolts that are designed to fail in shear (i.e., to break off) when the

torque exceeds a predetermined value.

16



Couplings

A Coupling is a device that makes relations with two shafts end to end, while a clutch is a

coupling provided with some form of sliding or other arrangement whereby the shafts can

be connected and disconnected at will. Couplings generally differentiate into (a) rigid

couplings and (b) flexible couplings. The rigid type is used where accurate lineal

alignment of the shafts is ensured. Where accurate alignment is not possible, a flexible

coupling is used; it allows for a certain amount of misalignment, besides acting as a shock

absorber for vibrations and jerks in the torque transmission.A universal coupling is applied for the connection of two shafts that are set at an angle to

each other and whose angle can be varied while the shafts are rotating. An arrangement

whereby two shafts are interconnected by an intermediate shaft with a universal coupling

at each end is referred to as a universal shaft (Fig.1). This principle is in use, for example,

in propeller shafts of motor vehicles.

The universal coupling may take a more elaborate form, permitting greater amounts of

angular movement, as in Fig.2, where each half of the coupling comprises two swivel pins

which so engage with appropriate sockets in a ring that the pins of one half are set at 90

degrees in relation to those of the other half. Essentially the same principle is applied in

the ball joint (Fig.3): the ball is provided with four holes which engage with two pins on

each half of the coupling.

The flanged coupling (Fig.1) is one of the simplest types, contains two halves, each

holding a flange mounted on the end of a shaft. The boss of each flange is keyed to its

shaft, and the flanges are bolted together, thus connecting the two shafts. The split-type

muff coupling (Fig.2) is easier to install and remove because the two halves can be fittedaround the aligned shaft ends and clamped by bolting. The muff is keyed to the shafts. A

more elaborate form of construction is the serrated coupling (Fig.3), comprising contact

surfaces with interlocking teeth that are held meshed together by bolts.

Doppler Effect

When a vibrating source of waves is approaching an observer, the frequency observed is

higher than the frequency emitted by the source. When the source is receding, theobserved frequency is lower than that emitted. This is known as the Doppler effect, or

17



Doppler’s principle, and is named after an Austrian physicist who lived in the first half of

the 19th century.

When a whistling locomotive (or any other sound source) approaches a stationery

observer (Fig.1), more density concentrations reach his ear than when both the sound

source and the observer are stationary.

As the pitch depends on the frequency (number of vibrations per second), the sound from

the approaching locomotive’s whistle has a higher pitch than the sound coming from the

same whistle when the locomotive is stationary in relation to the observer.

When the locomotive is receding, its whistle sounds with a lower note. At the instant

when the locomotive passes the observer, the note of the whistle is heard to change to alower pitch. The same effect is observed when we are passed by a fast-moving hooting

car in the street, or when the observer is moving fast in relation to a stationary sound

source.

Dry Ice

Dry ice is the name sometimes applied to compressed carbon dioxide snow i.e. solid

carbon dioxide with a temperature of -79°c. Under normal condition carbon dioxide is a

colorless and odorless gas with a density about 1 ½ times as high as that of air. Like

water, it can occur in the gaseous, liquid or solid state, depending on the physical

conditions. In addition carbon dioxide possesses the property of sublimation i.e. it can

pass directly from the solid to the gaseous state without becoming liquid.To make carbon dioxide snow, carbon dioxide is cooled at high pressure and liquefies

in consequences. Further cooling takes the carbon dioxide to the triple point. Now the

compressed liquid carbon dioxide is suddenly expanded by spraying and turns intosnow. This happens because the evaporation of part of the liquid causes intensive

cooling of the rest. To achieve this result, the carbon dioxide gas is liquefied by

means of three or four stage compressors with intermediate and final cooling, the

liquid carbon dioxide then being expanded in a tower. About one third of the liquid Is

thereby transformed into snow; the other tow thirds turn in gas, which is removed by

suction, recompressed and returned to the process. The snow is pressed into blocks

weighting 50-250 lb.

18



19



variety of adjustments and modifications, from the routine adjustment of the carburetor and

ignition system to significant engine overhauls. At the other end of the scale, performance

tuning of an engine can involve revisiting some of the design decisions taken at quite an

early stage in the development of the engine.Electric Generator (Dynamo)

Generators are machines used for the large-scale production of electrical energy. In

electricity generation, an electrical generator is a device that converts mechanical energy to

electrical energy. The generator is based on the principle of electromagnetic induction

discovered in 1831 by Michael Faraday. Faraday discovered that if an electric conductor, like

a copper wire, is moved through a magnetic field, electric current will flow in the conductor.

So the mechanical energy of the moving wire is converted into the electric energy of thecurrent that flows in the wire. Generators were earlier called dynamos, a shortened form of

the term dynamoelectric.

The size of large generators is usually measured in kilowatts. One kilowatt equals 1,000

watts. A giant generator can produce more than 1 million kilowatts of electric power. There

are two main types of generators. Direct-current (DC) generators produce electric current that

always flows in the same direction. Alternating-current (AC) generators, or alternators,

produce electric current that reverses direction many times every second.

Their operation is based on principle of electrical induction, whereby a periodic flow of

electricity is produced in a loop-type conductor as a result of the periodic variation of the

flux of the magnetic lines of force passing through this loop. In order to implement this, we

can either cause the loop to rotate in a constant magnetic field or, alternatively the loop can

be kept stationary and the magnetic field rotated.

In above mentioned arrangement loop is formed by the armature windings on the rotor whichrevolves between the fixed magnetic poles of the stator. In the latter arrangement the

armature is stationery, and the magnetic poles on magnet wheel revolve instead; the stator

consists of an iron ring with induction coils mounted on the inside; the magnetic poles on the

rotor move past the ends of these coils at a very short distance from them (Figs 1 and 3).

In this case the current produced by the generator is taken direct from the stator, without the

aid of special current collectors (brushes). Due to this reason this form of construction is

particularly suitable for the generation of high-voltage alternating current. The reverse

20



conversion of electrical energy into mechanical energy is done by a motor, and motors and

generators have many similarities. A generator forces electric charges to move through an

external electrical circuit, but it does not create electricity or charge, which is already present

in the wire of its windings.The sparking that occurs at high voltages i.e. around 20,000 volts in large generators would

destroy the brushes. The relatively low output of direct current needed for producing the

rotating magnetic field is fed to the rotor by means of slip-rings and carbon or copper-mesh

brushes (Fig.3). The successive coils in Fig.1 are wound in alternate directions, which ensure

that the generated current always flows in the same direction.

The source of mechanical energy may be a reciprocating or turbine steam engine, water

falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a handcrank, the sun or solar energy, compressed air or any other source of mechanical energy.

High-duty generators are usually coupled directly on the same shaft to steam or water

turbines.

A small direct current dynamo for producing the magnetic field is also mounted on the driving

shaft (Fig.2). In the older type of power station with reciprocating steam engines, the rotor of

the generator is generally constructed as a flywheel with the magnetic pole windings round its

rim. Fig.3 shows a smaller generator which likewise operates on the principle described above

(rotating magnetic field, stationery armature winding). In this case the magnet wheel is in the

form of a two-part T-rotor.

Electrostatics I

Matter is composed of neutral atoms. The electrical neutrality of the atoms is due to the

fact that the positive charge of the nucleus of the atom is compensated by the negative

charge of the electrons that surround it. The outermost electron may either be only loosely

connected to the rest of the atom (Fig.1a) or be more firmly embedded in it (Fig.1b).

Atoms of the first type tend to part with electrons to adjacent atoms, while those of the

second type tend to tear electrons away from adjacent atoms. It is because of this

phenomenon that, for e.g., glass becomes positively charged when it is rubbed with a silk

cloth (Fig.2a), whereas ebonite acquires a negative charge on being rubbed with a woolen

cloth (Fig 2b).

21



Electrostatic phenomena arise from the forces that electric charges carry out on each

other. Such forces are described by Coulomb's law. Even though electrostatically induced

forces seem to be rather weak, the electrostatic force between e.g., an electron and a

proton, that together make up a hydrogen atom, is about 40 orders of magnitute stronger than the gravitational force acting between them.

The power output from this electrostatic generator is not very large, for the charge

accumulated by this method cannot sustain a current of any significant magnitude. On the

other hand, very high voltages can be obtained of the order of some millions of volts. The

voltage can be further increased by installing the generator in an enclosed space in which

the air pressure is increased above the normal atmospheric pressure, so that the spark-over

voltage to earthed components is increased.

The amount of electric charge that can be stored up in a body is called the capacity of that

body. A condenser or capacitor is a device specifically intended to store up an electric

charge. Its capacity is determined mainly by the action of electrostatic induction. It has

essentially of two conducting surfaces which are insulated from each other (Fig.2a). In the

case of a variable condenser the area (F) of these surfaces and/or their distance apart (d 1,

d2) can be varied..

Obviously, the quantity of electricity that can be stored up by induction will be greater

according as F is larger and the gap d between the condenser plates is smaller. The

capacity of a plate condenser is therefore proportional to F and inversely proportional to

d. High capacity condensers are composed of plates consisting of rolled-up thin metal

foils separated by sheets of paper as the insulating medium. The capacity of a condenser

may be compared with the cubic capacity of a tank, which depends on the area of the

bottom and on the height (Fig.2b).If a small ball pendulum is attached to a conductor and the latter is charged with

electricity, the pendulum will acquire a deflection due to electrical repulsion which is

proportional to the magnitude of the charge (Fig.3a). there is an analogy with the pressure

of water in a tank, which pressure can be measured by means of a mercury manometer or

pressure gauge (Fig.3b).

The pressure of the water corresponds to the electric potential or voltage (the unit of

measurement being the volt.) The voltage (U) is associated with the electric charge Q and

the capacity C of a conductor (measured in farads) by the following relation: U = Q / C. In

23



the space which surrounds an electrically charged body an electric potential occurs which

is proportional to the charge Q and inversely proportional to the distance r from the center

of the body (U = Q / r).

The electrical condition produced in a space by the presence of electrically charged bodies

is called an electric field (Fig.4) points which all have the same potential (voltage) are

located on equipotential surfaces. Forces always act in the direction of the potential

gradient. The electric force which is exerted upon a charge of unit magnitude in an

electric field is called the field strength. It is always directed perpendicularly to the

equipotential surfaces.

The lines of force in an electric field represent the direction of the force at any point on

their length. The properties of an electric field can be described in terms of equipotential

surfaces and lines of force. The lines of force are conceived as emerging from positive

charges and disappearing into negative charges.

Fusion Welding

Fusion welding can be applied to processes in which metals are heated to the temperature

at which they melt and are then joined without hammering or the application of pressure.The joint can be formed without the use of a filler metal, but usually a filler metal in the

form of a wire or rod is employed to fill the joint.

The filler metal has the same composition as the parent metal, but may contain alloying

metals to improve its fluidity in the molten condition or to produce a fine grained weld

structure. The wire or rod of filler metal may be sheathed in a special coating. Such

coatings perform one or more of various functions : serve as a flux, remove oxides or

other disturbing substances that may be present, improve the wettability of the material

surface, protect the weld against external influences, prevent excessively rapid cooling,

and stabilize the arc.

The composition of the coating depends more particularly on the material to be welded

and on the welding method. Mixtures of oxides of iron, manganese and titanium, alkaline

earth carbonates, fluorite, and organic compounds are used for coatings. Sources of heat

employed in fusion welding are gas, electricity, chemical reactions, etc. Gas welding

(Fig.1) uses a flame produced by the burning in oxygen of acetylene (oxyacetylene

24



welding) or sometimes another fuel gas (e.g., propane, butane, hydrogen) to heat and

liquefy the metal at the joint to be welded. This is a very widely employed method of

welding iron, steel, cast iron, and copper. The flame is applied to the edges of the joint

and to a wire of the appropriate filler metal, which is melted and runs into the joint.

A fairly recent development is the electroslag process (Fig.2) in which the metal at the

joint is melted in an electrically conducting (ionized) molten-slag bath whose temperature

is above the melting temperature of the metal. The welds are executed as vertical welds;

with this method it is, for instance, possible to form butt welds in very thick plates quickly

and economically.

The current is supplied to the slag bath through bare metallic electrodes, which melt away

and provide the filler metal. The molten filler metal sinks in the slag, fills the gap of the

joint and slowly solidifies in it, from the bottom upwards. The gap is bridged by water-

cooled copper shoes which, together with the faces of the joint, form a mold for the

molten metal. The shoes move upwards along the joint during welding.

The most important and most widely used fusion-welding technique is arc welding, which

employs an electric arc to melt the parent metal and the filler metal. The latter may be

provided in the form of an electrode which melts away or it may be melted thermally i.e.,without carrying the welding current.

The general technique can be subdivided into three categories : open-arc welding, covered

arc welding, and gas-shielded-arc welding. Open-arc welding by Benardo’s method

(Fig.3a) employs direct current, the arc being formed between the parent metal and a

carbon electrode.In Zerener’s method (Fig 3b) the arc is formed between two carbon electrodes; the heat of

the arc is concentrated on the workpiece by the action of a magnetic coil. The methodnow most widely used was originated by Slavjanov (Fig.3c): the arc is formed between a

metallic electrode, which gradually melts away to supply the filler metal, and the

workpiece.

The process known as firecracker welding (Fig.4) is an example of a covered-arc method.

A heavily coated electrode is laid horizontally on the joint to be welded and is covered

with an insulating layer of paper and a covering bar of copper or some other metal. The

workpiece is connected to one pole and the electrode is connected to the other pole of a

25



current source. An arc is struck between the end of the electrode and the joint, and burns

along the length of the electrode

Another form of covered-arc welding is submerged-arc welding (Fig.5). The flux is

supplied separately in the form of powder which blankets the arc. The powder melts and

protects the molten filler metal from atmospheric contamination. Any powder not melted

is recovered by suction and reused. When cool, the fused powder forms a slag, which

peels off the weld.

Shielded-arc welding is based on the principle of protecting the molten filler metal by an

envelope of chemically inert gas, which may be helium (heliarc process), argon (argonarc

process) or carbon dioxide. In atomic-hydrogen welding (Fig.6a) the heat liberated by

monatomic hydrogen when recombining into molecules is used to fuse the metal.

An alternating-current arc is maintained across two tungsten electrodes. A stream of

hydrogen gas is passed through the arc, in which the hydrogen molecules are split up into

atoms. Outside the actual arc these atoms recombine into molecules. This produces great

heat, which melts the parts to be welded and unites them, with or without the addition of a

filler metal. The inert-gas tungsten-arc process (Fig.6b) and the inert-gas metal-arc

process (Fig.6c) are two shielded-arc welding processes that are used both for manualtechniques and for automatic welding by mechanized equipment.

Thermit welding (Fig.7) has already been referred to in connection with pressure welding.

It is also used as a fusion-welding process, more particularly for iron and steel castings

and forgings. The source of heat is not electricity or gas but a chemical reaction that

produces intense heat (3000oC): the combustion of a mixture of aluminum powder and

iron oxide by which the aluminum is converted into aluminum oxide and the iron oxide is

reduced to molten iron (or steel). The parts to be joined are surrounded by a sand-lined

mold. The powder mixture is packed in a conical crucible and ignited. The molten iron

flows in and around the joint, where it fuses with the preheated parent metal.

Friction drive

26



A Lambert automobile from 1906 with the friction drive revealed.

A friction Drive or friction engine is a type of transmission that, instead of a chain and

sprockets, uses 2 wheels in the transmission to transfer power to the driving wheels. This

kind of transmission is often used on scooters , mainly go-peds, in place of a chain.

An example of this system is in an early Turicum automobile. The Turicum's friction drive

consisted of a flat steel disc coupled directly to the engine. This primary disc subsequently

drove a smaller leather covered wheel oriented normal to its surface. Assuming a constant

rotational velocity on the primary wheel, the angular velocity on the disc's surface will

increase proportionally to the distance from the center of rotation. Therefore, positioning the

smaller wheel at different points along the larger wheel's surface varies the gear ratio.

Furthermore, since there are no limitations beyond the minimum and maximum positions, the

gear ratios are infinitely adjustable.

The problem with this type of drive system is that they are not very efficient. Since the output

wheel (leather covered wheel) has width, the area of contact is spread across various radii on

the primary disc. Consequently, since the angular velocity varies as radius varies, the system

must overcome these variances. The compromise is slippage of the leather to metal contact

area which creates friction, which in turn converts much of the energy transfer of this system

into heat. Heat generation also requires a cooling system to keep the transmission working

effectively.

27

http://en.wikipedia.org/wiki/Lambert_(automobile)

http://en.wikipedia.org/wiki/Transmission_(mechanics)

http://en.wikipedia.org/wiki/Chain

http://en.wikipedia.org/wiki/Wheel

http://en.wikipedia.org/wiki/Scooter_(motorcycle)

http://en.wikipedia.org/wiki/Turicum

http://en.wikipedia.org/wiki/Leather

http://en.wikipedia.org/wiki/Gear_ratio

http://en.wikipedia.org/wiki/File:1906_Lambert_2-cylinder_chassis.png

http://en.wikipedia.org/wiki/File:1906_Lambert_2-cylinder_chassis.png

http://en.wikipedia.org/wiki/Lambert_(automobile)

http://en.wikipedia.org/wiki/Transmission_(mechanics)

http://en.wikipedia.org/wiki/Chain


http://en.wikipedia.org/wiki/Scooter_(motorcycle)

http://en.wikipedia.org/wiki/Turicum

http://en.wikipedia.org/wiki/Leather

http://en.wikipedia.org/wiki/Gear_ratio



Fluorescent Lamp

The fluorescent lamp is a gas discharge tube whose output of light is so increased by

special tools that it can be used for lighting purposes. The inner surface of the wall of the

tube is coated with a light-emitting substance-usually fluorescent or phosphorescent

metallic salts (calcium tungstate, zinc sulphide, zinc silicate). The tube is filled with

mercury vapour at extremely low pressure. The electrons ejected from the incandescent

electrodes collide with the mercury atoms and cause these to emit radiation which consists

for the most part of ultraviolet rays, which are invisible.

The visible portion of the mercury vapour rays is located in the green and blue range of

the spectrum and gives a pale light. The ultra violet light strikes the fluorescent substance

with which the wall of the tube is coated and causes this substance to emit radiation with a

longer wavelength in the visible range of the spectrum i.e., the coating transforms the

invisible rays into visible light. By suitable choice of the fluorescent substance, this light

can be given any desired colour.

Fuel Injection and Supercharging

Instead of a carburetor, a fuel-injection system may be applied for introducing fuel

(gasoline, petrol) into the cylinder. It is basically similar to the system employed in a

diesel engine, except that with gasoline as the fuel the ignition is initiated by an electric

spark. A somewhat higher effective pressure better output can be achieved by injection as

compared with a carburetor system. On other hand, the injection equipment is more

expensive. In practical life, this method of introducing the fuel is therefore confined to

high-output or racing engines.

With the help of injection, the inlet pipe for each cylinder can be designed to give great

performance as an individual Oscillation tube. Since the fuel is injected straight into the

cylinder, the need to heat the inlet pipe (to prevent condensation of gasoline vapor) is

obviated. Consequently, cooler and therefore denser air is drawn into the cylinder, thus

improving the volumetric efficiency.

Injection of gasoline starts during the suction stroke. On entering the cylinder, the

gasoline vaporizes, and the heat for evaporation is extracted from the air, so that this cools

28



and decreases in volume, thus causing more air to be drawn in and thereby improving the

volumetric efficiency.

Fig.1 shows an arrangement in which the injection nozzle is aimed at the hot exhaust

valve, which is cooled by the gasoline. During the compression stroke the piston sweeps

past the outlet of the nozzle and thus protects it from the high pressure that develops at the

instant of combustion i.e. initiated by spark ignition. A different arrangement is shown in

Fig.2, in which the injection nozzle is located outside the cylinder, protected from high

pressure and temperature. It injects the fuel through the inlet port on to the opened inlet

valve and thus into the cylinder.

The measure to improve volumetric efficiency that have been described in the foregoing

relate to four-stroke internal-combustion engines which draw in the fuel-and-air mixture

by the natural suction developed in the cylinder. Another means of increasing the power

output is provided by supercharging. The supercharger is a compressor or blower which

supplies air, or a combustion mixture of fuel and air, to the cylinders at a pressure greater

than atmospheric. Because of this higher pressure, the air supplied to the cylinders has a

higher density and absorbs more gasoline vapor.

This increases the power output, but the gas consumption per horsepower is higher than ina suction-induced-charge engine, and wear and tear becomes more severe. Fig.3 is a

partial section through an American V8 engine equipped with a Roots supercharger with

three-lobed rotors. The supercharger is usually driven from the crankshaft.Foam Plastics

One of the basic features of foam-type materials is the structural configuration of the

cells. Absorbent cotton (cotton wool), felt and glass wool, for example, do not belong to

this category of materials; sponges and cork, on the other hand, do. A difference can bemade between true and false foams. In true foam the individual cells are not mere

relatively thick-walled cavities or pores, but are separated only by thin partitions and are

interdependent for their stability (Fig.1).

29



The mechanical strength is the highest in the case of foams with closed

(nonintercommunicating) cells. Since no convection is possible in such materials, they

possess good thermal insulating capacity. With open (intercommunicating) cells the

mechanical strength and thermal insulation are lower; while, these materials have a highsound-absorbing capacity and are therefore good acoustic insulators.

Artificial foam materials, including more particularly foam plastics, can be manufactured

by three different methods: by churning (Fig.2), by expansion with chemical agents(Fig.4) and by physical methods (Fig.3). The initial materials that can suitably be

processed into foams include polyvinyl chloride (PVC), polystyrene, urea and

formaldehyde condensation products, and natural synthetic rubber. In the churning

process of producing foam rubber, latex to which fillers, vulcanization accelerators and

foaming agents i.e. surface-active substances have been added is stirred with air to form

foam, which sets and is then vulcanized with hot air (Dunlop process).

30



Urea-formaldehyde foams are made by foaming a soap solution with an incompletely

condensed water-soluble resin resolution and air in an impeller-type high-speed mixer.

Further condensation is brought about by the addition of acid. In the process based on

physical methods, the foaming (expanding) action is produced by gases such as nitrogen,

carbon dioxide, or pentane. Gas dissolved in the material under pressure is liberated from

the solution and thus forms bubbles in the material when the pressure is reduced; this is

the foaming action.

For example, PVC pastes are processed with carbon dioxide at a pressure of about 20 atm.

(300 lb. /in 2) and a temperature between –5oC and 0oC. The fluid mass is passed into the

heating zone of the installation. Here the dissolved CO2 escapes and thus foams the

material. The foam sets at a temperature of 150 oC and is solidified by cooling.

Polystyrene is foamed with pentane, which is added at the polymerization stage e.g., inthe manufacture of styropor.

Chemical foaming methods are based on the fact that certain substances will, on being

heated, decompose and liberate gas, which forms small bubbles i.e. foam cells. Azo

compounds, N-nitroso compounds and azides are employed as foaming agents. What all

these compounds have in common is that they liberate nitrogen when they decompose.

For the manufacture of polyurethane foam plastics e.g., the German product named

Moltopren, compounds containing hydroxyl groups of high molecular weight are mixed

31



with disocyanates and water.

The foam plastic is formed according to the equation

HO.R1.OH + OCN.R2.NCO ->… CO2.R1CO2.NH.R2NH.CO2.R1.CO2…

Surplus isocyanate groups react with the added water and CO2 is evolved, which acts as a

foaming agent: R-NCO + H2O -> R-NH2 +CO2 Isocyanate amine

The reaction mixture is cast in molds in which both the foaming and the hardening

process take place. Blocks of foam are cut up into slabs or sheets by cutting machines.

In the building industry foam plastics have achieved importance as heat and sound

insulating materials. They are also used for a number of other purposes e.g., as paddings,

packing materials, materials for the manufacture of sponges and bath mats.

Galvanizing

Zinc plays a very important part among various metallic coatings applied to iron and steel

to provide protection against corrosion. This process of applying the zinc coatings is

called galvanizing.

It is very much useful for all types of articles and utensils, e.g.: buckets, washtub, bar,

tube, wire etc. Hot-dip galvanizing is one of the most commonly applied zinc coatings. In

this process zinc coating is obtained by immersion of the materials or articles in a bath of

molten zinc. The zinc combines with the iron, so that iron-and-zinc alloy crystals are

formed which provide a firmly adhering coating. The characteristic crystalline surface

patterns presented by hot-dip coatings are known as spangles; their size and shape are

influenced by the surface condition of the steel, the impurities present in the bath, the rate

of cooling, etc. Other types of Zinc-coating process are electrogalvanizing, metal spraying

& sherardizing. These coatings are less in use compare to Hot-dip galvanizing.

For successful completion of hot-dip galvanizing first of all the steel must be free of oil,

grease, dirt, scale, and corrosion products. Preparatory treatment includes all of the

following: degreasing with a suitable solvent, pickling with acid, rinsing, treatment with a

flux, and drying. The object of pickling is to remove any oxide film by the action of

hydrochloric or sulphuric acid. Castings to which molding sand still adheres may have to

be subjected to mechanical cleaning treatments such as grit blasting or tumbling, the latter

32



being an operation in which small articles are mixed with an abrasive and rotated in a

cylindrical drum. The flux, usually a mixture of zinc chloride and ammonium chloride,

serves to remove any remaining traces of impurities and increases the wettability of the

steel surface. Certain metals such as tin and aluminum may be added to the bath, they promote fluidity, and tin imparts brightness to the coated material.

Sherardizing is a process for forming intermetallic compounds of iron and zinc on a steel

surface. This is formed by heating it in the presence of zinc dust below the melting of the

zinc. This process is more often used for small articles such as bolts, nuts, chains, valves

etc.

Improving Volumetric Efficiency

Another method of improving the engine performance by increasing the mean effective

pressure consists in improving the so-called volumetric efficiency i.e., the efficiency with

which the cylinders are charged with the fuel-and-air mixture. The quantity of mixture

drawn into the cylinder during the suction stroke determines the mean effective pressure

and therefore the power output.

This quantity should theoretically be equal to the working volume of the cylinder = pistonarea x stroke. In reality the quantity of mixture drawn into the cylinder is less. The ratio of

the actual to the theoretical quantity is known as the volumetric efficiency. It depends on

the size and shape of the inlet and exhaust ducts and ports, the shape of the combustion

chamber, and the method whereby the fuel is introduced into the cylinder.

There are several standard ways to improve volumetric efficiency. A common approach

for manufacturers is to use larger valves or multiple valves. Larger valves increase flow

but weigh more. Multi-valve engines combine two or more smaller valves with areas

greater than a single, large valve while having less weight. Carefully streamlining the

ports increases flow capability. This is referred to as Porting and is done with the aid of an

air flow bench for testing.

Improving the Engine’s Mechanical Efficiency

A major portion of the power developed by the expansion of the gas in the cylinders is

used for overcoming friction between piston and cylinder and in the bearings of the

33



connecting rod and crankshaft and for driving the water-circulation pump, oil pump,

dynamo, camshaft and valves (Fig.1). Hence only a certain proportion of the theoretical

power output is available as effective output. This proportion is termed the mechanical

efficiency of the engine. Depending on the type and design of the engine and on its stateof maintenance, the mechanical efficiency is usually between 0.75 and 0.85.

More than half the loss of power is due to friction of the pistons and bearings. The piston

friction depends on the pressure developed in the cylinder and on the piston speed, which

is determined by the stroke and speed of rotation. Generally speaking, the rotational speed

should be as high as possible. Therefore the only possible means of reducing the friction

is to shorten the piston stroke. The friction developed at the piston rings depends on the

number of rings per piston. To reduce the loss of gas, it is necessary always to have twocompression rings; in addition, each piston has an oil-scraper ring (Fig.2).

Friction in the crankshaft bearings can be reduced by the use of lighter connecting rods.

This also reduces the lubricant requirement of the bearings, so that the oil-pump power

input is lessened. A crankshaft rotating at high speed causes frictional losses due to

turbulence and foaming of oil in the sump. For this reason high-speed engines have dry-

sump lubrication (Fig.3). In this system, oil entering the crankcase is immediately

extracted by suction and is returned through a filter and a cooler to the oil tank. A second

pump delivers the oil from the tank to the bearings.

For E.g. A water cooled engine is usually equipped with a fan. The fan is necessary only

when the cooling-water temperature is high. For a substantial proportion of the engine’s

running time the fan is absorbing power without performing any useful function. For this

reason fans have been developed that are switched on and off automatically, controlled by

the temperature of the cooling water or air.

The factor which has the greatest effect on mechanical efficiency is friction within the

engine. The friction between moving parts in an engine remains practically constant

throughout the engine’s speed range. Therefore, the mechanical efficiency of an engine

will be highest when the engine is running at the speed at which maximum bhp is

developed. Since power output is bhp, and the maximum horsepower available is ihp.

When an engine is operating under part load, it has a lower mechanical efficiency than

when operating at full load. The explanation for this is that most mechanical losses are

34



almost independent of the load, and therefore, when load decreases, ihp decreases

relatively less than bhp. Mechanical efficiency becomes zero when an engine operates at

no load because then bhp = 0, but ihp is not zero. In fact, if bhp is zero and the expression

for fhp is used, ihp is equal to fhp.

Improving Engine Speed

The higher the speed, the higher will be the output of an engine. The formula for the

output also contains the factor n, the rotational speed of the engine. This theoretical

consideration cannot be fully translated into practical terms. With increasing engine

speed, the piston speed increases and the fractional losses become higher. At the same

time, the mean effective pressure diminishes because of the higher resistance encountered

in the inlet and exhaust system i.e. throttling effect on the gas flow.

This in turn reduces the volumetric efficiency. Besides, the inertial forces developed by

the reciprocating parts of the crank and valve mechanisms are not allowed to exceed

certain values, otherwise damage is liable to occur. When the cubic capacity for a new

engine design has been determined, the influences of high speed that adversely affect

power output and engine life can be largely obviated by a suitable choice of the number of

cylinders, the stroke-bore ratio, and the piston speed.

The engines used in ordinary present-day cars have rotational speeds of between 5000 and

6000 rpm a range that only a few years ago was reserved for sports-car engines. Racing

engines have meanwhile moved up into the 11,000-14,000 rpm range, though this result

has been achieved only with considerable effort and cost.

The total cubic capacity i.e., the total piston-swept working volume VH of an engine

should be divided over the largest possible number of cylinders, to ensure that thereciprocating masses of the individual pistons and connecting rods will be small. The

lighter these components are, the easier and less power-consuming will be their

acceleration and deceleration at the ends of the piston stroke. For a given cubic capacity,

the capacity of the individual cylinder is reduced, the bore and stroke are likewise

reduced, and the piston speed is lower.

However, an increase in the number of cylinders also has its drawbacks. For one thing,

there are now more bearings in which friction occurs. In addition, the cost of manufacture

35



goes up because of the more numerous components that have to be made, machined and

assembled. For reasons of economy, the cubic capacity of a cylinder of an ordinary car

engine is normally between 250 and 500 cc. A racing car engine usually has many

relatively small cylinders ranging from, for e.g. 62cc (Honda) to about 200cc.

In addition to dividing the total cubic capacity among a large number of cylinders each of

relatively small capacity, other measures to reduce the reciprocating masses of the pistons

and crank mechanism consist in the use of light-alloy pistons and connecting rods made

from titanium, a metal not unlike steel, but lighter.

When the capacity of the individual cylinder has been determined, the stroke s and the

bore d can be determined from the stroke-bore ratio (s/d) that has been chosen. As a rule

this ratio is somewhere between 0.7 and 1.0. It should be as low as possible for high-

speed engines, so that the cylinder bore is larger than the stroke; i.e., the cylinder is

relatively wide, making possible the use of large valves. Besides, the piston speed is then

also lower, so that the frictional and throttling losses during the suction stroke are less.At high speeds the crankshaft functions under severe stress conditions because at each

power stroke it is subjected to sudden impactlike torsional loading. The crankshaft must

therefore be of very rigid construction; it must not deflect. Better resistance to deflection

is obtained by closer positioning of the crankshaft bearings (usually called the main bearings).

Efficient design of the valve mechanism is of major importance in high-speed engines

because accurate valve timing at all rotational speeds is essential. This calls for rigid and

vibration-free construction. The valve is opened against the closing action of a spring; the

force developed by the spring should be sufficiently powerful to ensure that all speeds the

valve motion accurately conform to the shape of the cam.

At high speeds there is only very little time available in which closure of the valve can be

affected, a mere fraction of a second. To keep the spring force needed for this within

reasonable limits, the weight of the reciprocating valve parts in a high-speed engine

should be reduced to a minimum. There are various methods of achieving this. Dividing

the total cubic capacity among a large number of cylinders permits the use of

correspondingly smaller and lighter valves.

The high speeds of present-day engines have been attained partly as a result of using

36



overhead camshafts, thereby eliminating transmission elements which make the valve

mechanism slower and more cumbersome. For high-speed engines the arrangement in

Fig.1a is preferable to that in Fig.1b because the moving masses in the former are smaller.

Sports-car and racing-car engines have hemispherical combustion chambers, so that thevalves have to be inclined.

For this reason each row of valves is provided with its own camshaft. This solution is too

expensive for the engines of ordinary cars. Alternatively, two rows of inclined valves can

be actuated by one camshaft (Fig.2), though in this arrangement the rockers constitute a

larger moving mass. Fig.3 shows a different overhead camshaft arrangement embodying a

tappet.

In ordinary car engines, the overhead camshaft is usually driven by a chain from the

crankshaft and at half the speed of the latter. To avoid objectionable noise arising from

wear and thermal expansion, the chain is kept under uniform tension by a tensioning

device. In some instances a silent valve drive in the form of a toothed plastic belt

(reinforced with steel wire) is used instead of a metal chain. The camshaft drive systems

illustrated in Figs.1 and 2 are suitable for engine speeds up to 7000rpm.

In racing engines which operate at considerably higher speeds, the overhead camshafts aredriven though the agency of gear systems or bevel-geared shafts. Such systems are

preferable to chain drives because they are free of vibration and backlash effects. They are

of course, also more expensive.

Another means of reducing the weight of the valves consists in using valves with hollow

stems. To improve the heat conduction and cooling of the exhaust valves, which becomes

very hot, their stems are partly filled with sodium. At the high working temperatures the

sodium is molten and its movements help to conduct heat from the valve head to the

cooler parts of the stem, thus cooling the head (Fig.4).

As an alternative to one large and heavy valve it is possible to employ two smaller, lighter

valves. Thus the cylinders of some racing engines are each provided with two inlet valves

and one exhaust valve. This is a very expensive form of construction and therefore

unsuitable for ordinary engines. Various types of valve embodying positive actuation, as

distinct from the spring-controlled reciprocating action of the usual poppet (or mushroom)

valve envisaged here, have been devised, including more particularly the rotary valve, but

37



have never achieved much practical significance.

Natural Petrol (Gasoline)

A distinction is made between synthetic petrol, which is produced from coal and other

raw materials by chemical processes, and natural petrol, most of which are obtained as a

substance already present in petroleum denotes a mixture of liquid, volatile hydrocarbons

or to be more precise, a mixture of alkenes, naphthenic and aromatic compounds with

boiling points between 40° and 180°C.

Hydrocarbons is a general designation for chemical compounds which consist solely of the elements hydrogen and carbon and which readily burn to produce carbon dioxide and

water if they are mixed with a sufficient quantity of air and then ignited. Petrol for use as

a fuel for internal combustion engines is produced by following process:

The petroleum is pumped from the well though pipelines to storage tanks at the port of

shipment, where the crude oil undergoes a preliminary purification treatments. Tankers

convey the crude oil to other ports, where it is discharged into storage. From here it is

distributed to the refineries e.g. through pipelines.

At the refinery the petroleum is preheated in heat exchanges, and then passed to the tube

stills, where heated to a high temperature in special steel tubes. These stills are fired with

oil which is likewise obtained from the crude oil. The crude oil, heated to a temperature of

several hundred degrees, expands in the distilling column, where it is separated into

fractions: power gas, light petrol and petrolThe remaining of the original quantity is again passed through the still, is reheated to a

high temperature, and is passed to a distilling column in which a vacuum is applied;

because the distillation temperature can be kept considerable lower when the vacuum is

employed. In this second column 20% of the original quantity of crude oil is split into

petrol, 15% into fuel oils and 20% of the original oil. The residue, about 27% provides

tar, pitch and coke or undergoes for processing whereby in some cases, more petrol is

produced.

However, such petrol is more properly to be regarded as synthetic petrol. The various

petrol factions are mixed and refined : the composition of the mixture depends on the time

38



of year, in the winter the proportion of liquid petrol in the mixture is higher than in the

summer.

Refinement involves various processing treatments whereby the quality of compounds,

anti-knock agents, anti-oxidants etc. the result must be volatile fuel which must, among

other properties, have a minimum octane number of 80 to 90, ignites easily does not

gasify at room temperature, does not develop gumming, does not smell objectionably, and

burns without residue. Such a mixture of substances is of extremely complex composition

comprising two hundred individual constituents.

Powder Metallurgy

The technology of powdered metals can be used in the production and utilization of

metallic powders for fabricating massive materials and shaped objects.

This process in which articles and components are produced by agglomeration of fine

metallic powder, is employed in cases where other methods of shaping such as casting,

forging and machining are impracticable or where special material properties have to be

achieved.

The materials used in powder metallurgy,metallic posers or, for some purposes, mixtures

of metallic and nonmetallic powders are shaped by cold pressing at room temperature

between steel dies, which produces initial adhesion of the particles. This is followed by

heating of the compacts in a nonoxidizing atmosphere (sintering) to obtain final cohesion.

The dies usually consist of two parts thrusting against each other, and each part may be

subdivided to produce the required shape (Fig 4). Another technique is isostatic pressing:

the powder is pressed in a closed flexible container rubber plastic under liquid pressure.

The function of the sintering treatment is to bond the powder particles of the compact into

a coherent mass. As a rule, the sintering temperature is somewhat below the melting point

of the powder, or the temperature may be so controlled that fusion of certain constituents

of the powder mixture is achieved. Sintering as a subsequent separate treatment may be

dispensed with by pressing of the powder at elevated temperature or by subjection of

cold-pressed compacts to hot shaping e.g., by drop forging, rolling or extrusion. In certain

cases, it is advantageous to process the powder in a protective metal envelope which

provides mechanical strength and/or protection against oxidation (Fig.2c). To prevent

39



oxidation, hot pressing or sintering is usually carried out under the protection of a

shielding gas or in a reducing atmosphere.

Shaping of the powder is generally done by the application of pressure. However, in slip

casting process, a technique adopted from the ceramics industry (Fig.1), the powder is

mixed with a suitable liquid suspension medium to form a slip (a thick suspension), which

is put into a mold (a, Fig.1). The liquid is absorbed by the walls of the mold, usually

consisting of gypsum plaster (b). Then the shaped component is removed from the mold,

dried and sintered (c). The powders used in powder metallurgy are produced by

comminution of solid materials, by atomizing of molten materials in a stream of gas or

water (Fig.3), or by chemical processing. It is essential to obtain particles that are suitably

graded in size and are of regular shape and surface condition, so that they interlock andadhere properly when compressed.

Plastics Processing

The properties of plastics and the many different requirements depending on finished products

made from them have led to the development of a number of methods for shaping and

molding these materials. From the manufacturers who synthetically produce plastics for

industrial use the fabricating industry obtains the specified initial materials, i.e., the

appropriate polymers with or without the requisite additives.

In the latter case the user will have to add auxiliary materials such as plasticizers, stabiliziers,

pigments and fillers. Batch mixing of powdered ingredients is performed in agitators or

mixing drums. Alternatively, kneaders or mixing rolls (Fig.1) are used for plastifiable

materials. The last mentioned device comprises a pair of rollers which revolve in opposite

directions and which can be heated or cooled as required.

40



The material entering the gap between the rollers is squeezed and mixed. On completion of

this treatment the so-called rough sheet is stripped from the rollers (Fig.1) and passed to a

further stage of processing. Continuous mixing is performed in extruders, which offer the

additional advantage of filtering the plastics before they undergo further processing (Fig.4).

The shaping of plastic articles and components without the application of pressure is effected

by casting. The simplest method of shaping in conjunction with pressure is by molding

(Fig.2), which is suitable for both thermosetting and thermoplastic compositions.

Thermoplastics can be softened by the application of heat; thermo setting plastics undergo

chemical change under the action of heat and are thereby converted to infusible masses which

cannot be softened by subsequent heating.

The Plastic Processing programme has been drawn up by the Finnish plastics industry, the

41



universities and Tekes with the aim of improving the competitiveness of companies

developing injection moulding, and manufacturing and using injection-moulded components.

The programme is finished.

The aim of the entire programme was to improve the competitiveness of the companies in the

business chain. This was achieved by speeding up the product development process, the

mould manufacturing process and making them more efficient and by controlling the

production process considerably better than at present. An additional goal was to improve

mould performance, speed up start-up times for production processes and minimize

environmental impacts.

Another method of producing molded articles is by injection molding (Fig.5), which has the

advantage over ordinary molding that preheating, plasticizing, and shaping are done by the

same machine. The only materials suitable for injection molding are thermoplatics of high

fluidity. The granules are introduced through a hopper into the cylinder, in which they are

heated-by means of a heating jacket- to above their softening point. A moving piston

plasticizes the material and forces it through a nozzle into the mold. The plasticizing action

can be enhanced by the use of a screw instead of a piston (Fig.6).Articles or components can also be shaped by the machining of semifinished products films,

sheets, rods or tubes. Machining is more particularly employed in cases where the articles are

of complex shape or where only a small number are required. Whereas thermosetting plastics

can be shaped only by machining (milling, turning, cutting, drilling) once they have hardened,semifinshed thermoplastic materials can be shaped by heating and joined by welding. Hot

shaping of thick sheets can be effected by bending or drawing (Fig.3). In the drawing process

the material to be shaped is gripped, heated and deformed to the desired shape. If the wall

thickness must remain constant, the sheet must be resiliently gripped; with so-called stretch

forming a reduction in wall thickness occurs.

In recent years shaping by the vacuum process has gained importance. In the female-mold

method or negative mold method, the heated plastic sheet is laid on a concave mold and

42



subjected to further heating. Air is extracted through holes in the mold, so that the sheet is

drawn by suction into the mold. For the molding of complex components the plate is

prestretched before the actual negative molding operation begins.

Alternatively, a convex master model may be used, in which case the process is known as the

male-mold method or positive-mold method. The preheated sheet is placed over the master

model and preformed. When the air is evacuated, the desired shape is obtained. The molding

techniques are schematically illustrated in Figs.8 and 9.

Endless products such as sections, sheet, strip and thin are produced by extruders (Figs. 4 and

6). Extrusion consists in forcing a plastic material through a suitably shaped die to produce the

desired cross-section shape. The extruding force may be exerted by a piston or ram (ram

extrusion) or by a rotating screw (screw extrusion) which operates within a cylinder in which

the material is heated and plasticized and from which it is then extruded through the die in a

continuous flow.

Different kinds of die are used to produce different products e.g., blown film formed by blow

head for blown extrusions, sheet and strip slot dies and hollow and solid sections i.e. circular

dies. Wires and cables can be sheathed with plastics extruded form oblique heads. The

extruded material is cooled and is taken off by means of suitable devices which are sodesigned as to prevent any subsequent deformation.

For the manufacture of large quantities of film or thin sheet, the sheeting calender is employed

(Fig.7). The rough sheet from the two-roll mill is fed into the gap of the calender, a machine

comprising a number of heatable parallel cylindrical rollers which rotate in opposite directions

and spread out the plastics and stretch the material to the required thickness.

The last roller smoothes the sheet or film thus produced. If the sheet is required to have a

textured surface e.g., to resemble wood graining, the final roller is provided with an

appropriate embossing pattern; alternatively, the sheet may be reheated and then passed

through an embossing calender. The calender is followed by one or more cooling drums.

Finally the finished sheet or film is reeled up.

Another field of application consists in coating a supporting material e.g., textile fabrics,

paper, cardboard, metals, various building materials with plastics for the purpose of electrical

insulation, protection against corrosion, protection against the action of moisture or chemicals, providing impermeability to gases and liquids, or increasing the mechanical strength. Coatings

43



are applied to textiles, foil and other sheet materials by continuously operating spread-coating

machines (Fig.10).

A coating knife, also known as doctor knife ensures uniform spreading of the coating

materials in the form of solutions, emulsions or dispersions in water or an organic medium on

the supporting material, which is moved along by rollers. The coating is then dried.

Alternatively, the coating applied to the supporting material may take the form of film of

plastic, in which case the process is called laminating.

Metal articles of complex shape can be coated with plastics by means of whirl sintering

process. The articles, heated to above the melting point of the plastics, are introduced into a

fluidized bed of powdered plastics a rising stream of air in which the powder particles are held

in suspension, whereby a firmly adhering coating is deposited on the metal by sintering.

Resonance And Echo

Resonance is a phenomenon that structures capable of oscillation will oscillate insympathy with relatively feeble external forces which act periodically and whose

oscillation period coincides with that of the resonating structure. While it is resonating,

the structure stores up energy.

The oscillations do not, however, go on increasing indefinitely, but are limited by energy

losses in this case more particularly by losses due to friction of the liquid on the wall of the

tube. Resonance of a magnetically polarised steel spring can be induced by the fluctuating

magnetic field of an electromagnet energized by an alternating current (Fig.2a). This

resonance effect is, for example, utilized in frequency meters.The conception of resonance had its origin in the science of acoustics. Fig.2b illustrates an

acoustic resonator, a device known as Kundt’s tube which is used for measuring the

wavelength of sound waves. Projecting into the glass tube is one end of a metal rod which is

held gripped in the middle. Longitudinal vibrations are set up in this rod by rubbing it with a

cloth sprinkled with powdered rosin. The end of the rod in the tube is provided with a disc

which in turn transmits the vibrations to the air in the tube.

44



Under certain circumstances the amount of energy stored up in this way may become so

great that it brings about the destruction or collapse of the structure. A simple example of

a resonating structure is a child’s swing (Fig 1a). It is a pendulum, which is given a push

or a thrust in the swinging direction each time it reaches its maximum deflection. Itsenergy build up i.e., its resonance, is directly evident from the increasing amplitude of the

deflection of the swing. Another example is a liquid in a U-shaped tube (Fig.1b). The

liquid can be set in motion by blowing into one end of the tube, and by blowing it

periodically at the appropriate instant, the amplitude of its oscillations is progressively

increased.

The effective length of the tube can be varied by means of an adjustable disc at the other

end. The vibrations i.e sound waves are reflected by this disc, and on suitably adjusting its position, a stationery wave will be produced in the tube, and resonance occurs.

This happens when the distance between the two discs is equal to an odd multiple of one-

quarter of the wavelength of the sound waves set up in the tube, and vibration nodes and

antinodes are formed. These can be indicated by introducing a small quantity of some

suitably light powder e.g., lycopodium powder, into the tube. The powder congregates in

a heap at each node. The nodes are thus made Visible, and the distance between them can

be measured. The distance between two successive nodes is equal to half the wavelength

of the sound waves set up in the tube.Resonance effects are also observed in connection with electromagnetic phenomena. The

most well known and important example is the excitation of an electromagnetic

oscillatory circuit, comprising a self-inductance L and capacity C by an alternating

voltage (Fig.3) In the circuit the energy oscillate between its electrical state in the

condenser (Fig.3a) and its magnetic state in the magnetic field of self-induction (Fig.3b) If

the natural period of vibration and therefore the frequency of the oscillatory circuitcorresponds to that of the alternating voltage, resonance will occur.

The circuit will in that case absorb the maximum amount of energy from the source of

energy that produces the excitation. Radio transmitters and receivers are turned with the

aid of this resonance effect. To prevent the energy attaining disastrously high values,

resistances are included in the circuit; these cause energy losses in the form of heat.

Another phenomenon that acoustic and electric vibrations have in common is echo, i.e.,

the reflection of sound waves or electromagnetic waves from obstacles they encounter

45



Resonance and Engine Efficiency

In addition to the measures explained in the foregoing, an inlet-and-exhaust system of

favorable design with regard to oscillation condition of the gas does much to improve the

intake and exhaust efficiency of the engine. The pulsating intake of the fuel-and-air

mixture and discharge of the exhaust gases initiates oscillation in the system. At the end

of the suction stroke the fuel-and-air mixture in the inlet duct flows at high velocity to the

inlet valve, which is in the process of closing.

No engine design should ignore the potentially destructive and energy wasting effects of

resonance, but very little anti-resonance development has been applied since the ICengine was first introduced. The closure slows down the rush of the mixture, which

impinges on the valve and causes a buildup of pressure in front of it.

As a result, the fuel mixture continues to flow into the cylinder even after the piston has

passed through bottom dead center and is rising again to start the compression stroke. But

the inlet valve now closes completely and deflects the mixture back along the inlet duct.

This is what initiates the oscillation in the duct.

At the open end of the duct the fuel mixture is again deflected, and the cycle is repeated.

If in case when the inlet valve opens again, the pressure wave in the inlet duct is moving

toward the valve, the mixture will immediately enter the cylinder. The system is now in a

state of resonance. As the inlet valve opens wider and the piston moves downwards, the

pressure in the inlet duct drops, while the velocity rises to its maximum. Toward the end

of the suction stroke the inlet valve begins to close again, so that the flow is again

retarded, the pressure builds up, and the oscillation phenomena are repeated.

Optimum charging of the cylinder with the fuel mixture is achieved when the frequency

of oscillation coincides with the opening and closing frequency of the valve so as to

produce resonance, as envisaged above when the inrush of fuel mixture finds the valve

just opening to let it into the cylinder. Evidently this will occur only at one particular

engine speed. At other speeds the volumetric efficiency will be lower. Long inlet ducts

provide good charging at high speeds, whereas short ones are better at relatively low

speeds.

46



The development of oscillation and resonance is counteracted by the flow resistance in the

inlet duct, the constriction and turbulence at the throttle valve (in the carburetor), and the

damping effect occurring at the open intake end of the duct. Figs 1 and 2 show the

oscillation system in a four cylinder engine: the inlet pipes all emerge from a singleconnection at the carburetor, so that damping occurs there. The charging is therefore

poorer than in the case of the inlet system of a fuel-injection spark-ignition engine as

illustrated in Figs 3 and 4.

Synthetic petrol is also manufactured from water and coal by a process in which carbon

monoxide and hydrogen are produced form coke, raw brown coal or brown coal

briquettes and, after careful cleaning, are passed over catalysts at low pressure. Solid

hydrocarbons, in addition to petrol and other products are formed in this process. In amore recently developed process, gases containing carbon monoxide are conducted,

together with water over suitable catalysts.

The resulting reactions produce petrol, as well as acids, alcohols and other substances.

Also, petrol is produced from unsaturated hydrocarbon gases with aid of catalysts.

However, since such synthetic petrol are more expensive to produce than petrol from

petroleum in western Europe synthetic petrol is nowadays importance only as a additive

for natural petrol so as to adjust their properties to meet the exacting requirements of

modern internal combustion engines. For purpose, synthetic petrol have a high octane

number are particularly valuable.

Sulphuric Acid

Although sulfuric acid is now one of the most commonly used chemicals, it was probably

little known before the 16th cent. It was prepared by Johann Van Helmont (c.1600) by

destructive distillation of green vitriol (ferrous sulfate) and by burning sulfur. The first

major industrial demand for sulfuric acid was the Leblanc process for making sodium

carbonate (developed c.1790). Sulfuric acid was produced at Nordhausen from green

vitriol but was expensive.

A process for its synthesis by burning sulfur with saltpeter (potassium nitrate) was first

used by Johann Glauber in the 17th cent. and developed commercially by Joshua Ward inEngland c.1740. It was soon superseded by the lead chamber process, invented by John

47



Roebuck in 1746 and since improved by many others. The contact process was originally

developed c.1830 by Peregrine Phillips in England; it was little used until a need for

concentrated acid arose, particularly for the manufacture of synthetic organic dyes.

In the pure state, sulphuric acid is a clear, colorless, oily liquid. One-hundred percent

H2SO4 has its melting point at 10°C; when heated, it gives off SO 3 until the concentration

of the acid has fallen to 98.5%, and it then boils at a constant temperature of 338°C.

Considerable evolution of heat occurs when concentrated sulphuric acid is diluted with

water. Substantial amounts of SO3 can dissolve in the acid. The resulting solution is

known commercially as fuming sulphuric acid.

Sulphuric acid does not occur as a free acid in nature. It is found only in the form of its

salts (sulphates): gypsum (CaSO 4.2H 2O), Epsom salts (MgSO 4.7H 2O), barite (BaSO 4) and

Glauber’s salt (Na 2SO 4.1OH 2O). Up to about the eighteenth century, sulphuric acid was

made by heating alum (aluminum potassium sulphate) or iron vitriol (hydrous ferrous

sulphate).

This method was superseded by the burning of natural sulphur with saltpeter, which

eventually evolved into the so-called lead-chamber process, which has the advantage that

the acid can be obtained in any desired concentration, whereas the highest attainable

48



concentration with the lead chamber process is 78%.

The contact process is as follows, Sulphur dioxide (SO 2) is obtained by roasting iron

pyrites (FeS 2) in a rotary kiln, shelved roasting kiln or fluidized bed kiln. Which of these

kiln types is employed depends on the particle size and nature of the pyrites to be

processed. When the gases from the roasting process have cooled in gas ducts, by

radiation of heat from 1000 oC to about 400°C -500°C, the dust they contain is removed

in electrostatic precipitators (electric fitters). Next, the SO2 gas is passed through a washing tower, where constituents that are present

in vapor form mainly compounds of arsenic, selenium and chlorine are removed with

sulphuric acid serving as the washing liquid. Remaining traces of impurities present as

very fine suspended droplets (fog) are removed in an irrigated electrostatic precipitator (wet Precipitator). Then the gas is dried by being brought into contact with concentrated

(98%) sulphuric acid.

A blower draws in the cold dried SO2 gas and delivers it into the converter, which is a

tank or tower in which a suitable catalyst e.g., vanadium pentoxide (V2O5) is placed in

layers on shelves or arranged in some other appropriate manner to ensure through contact

with the gas. The reaction whereby SO2 is converted to SO3 by oxidation (2SO2+O2->

2SO3) takes place at 430°C to 550°C. A heat exchanger installed before the converter serves to cool the gas discharged from the converter and at the same time preheats the

incoming gas flowing to the converter.

Sulfuric acid is one of the most important industrial chemicals. More of it is made each

year than is made of any other manufactured chemical; more than 40 million tons of it

were produced in the United States in 1990. It has widely combined uses and plays some

part in the production of nearly all manufactured goods.

The major use of sulfuric acid is in the production of fertilizers, e.g., superphosphate of

lime and ammonium sulfate. It is widely used in the manufacture of chemicals, e.g., in

making hydrochloric acid, nitric acid, sulfate salts, synthetic detergents, dyes and

pigments, explosives, and drugs.

It is used in petroleum refining to wash impurities out of gasoline and other refinery

products. Sulfuric acid is used in processing metals, e.g., in pickling (cleaning) iron and

steel before plating them with tin or zinc. Rayon is made with sulfuric acid. It serves as

49



the electrolyte in the lead-acid storage battery commonly used in motor vehicles acid for

this use, containing about 33% H2SO4 and with specific gravity about 1.25, is often

called battery acid.

Ship Stabilizing

A ship at sea does rolling and pitching movements about its longitudinal and its transverse

axis respectively (Fig.1). Rolling in particular is disagreeable to crew and passengers

because of its relatively large amplitude, besides presenting problems with regard to the

storage of the cargo.

The rolling motion depends on various factors: the wave movement according to the stateof the sea, the vessel’s moment of inertia with respect to the rolling axis, the damping

moment due to friction between the hull and the water, and the stability moment,

determined by the horizontal distance between center of gravity and center of buoyancy.

Ship stabilizers are fins mounted beneath the waterline and emerging laterally. In

contemporary vessels, they may be gyroscopically controlled active fins, which have the

capacity to change their angle of attack to counteract roll caused by wind or waves acting

on the ship.

Different kinds of devices, known as stabilizers, have been developed for the purpose of

reducing the rolling motion of ships. In general these appliances are of the passive or of

the active type. The action of a passive stabilizer can be obtained by the rolling itself, i.e.,

such a device responds to the motion and takes corrective action. On the other hand, an

active stabilizer has present control whereby the corrective action in the form of a

counteracting movement is programmed to take place simultaneously with the occurrence

of the disturbing movement that causes the rolling of the ship.

The wave movements, in particular, are never quite regular, but it is nevertheless possible,

by means of appropriately designed active stabilizers, to reduce rolling by at least 75%.

The greatest effect is obtained when the stabilizer operates at the natural frequency of the

ship, but with a phase difference of 90 degrees in relation to the ship’s motion.

The simplest stabilizing device is the bilge keel (Fig.2), this is one such keel which is

fitted on each side and extending about 30-50% of the ship’s length. Bilge keels develop

50



considerable resistance to the rolling motion and thus reduce it. The stabilizing effect

achieved by these keels depends to a great extent on the speed of the ship. They have the

drawback that they present a not inconsiderable resistance and thus slow down the vessel.

Instead of being a continuous keel, the stabilizing device may take the form of a series of short fins having a streamlined shape in section so as to reduce the resistance.

Absorption refrigerator

An absorption refrigerator is a refrigerator that uses a heat source (e.g., solar , kerosene-

fueled flame, waste heat from factories or district heating systems) to provide the energy

needed to drive the cooling system. Absorption refrigerators are a popular alternative to

regular compressor refrigerators where electricity is unreliable, costly, or unavailable, where

noise from the compressor is problematic, or where surplus heat is available (e.g., from

turbine exhausts or industrial processes, or from solar plants).

For example, absorption refrigerators powered by heat from the combustion of liquefied

petroleum gas are often used for food storage in recreational vehicles . Absorptive

refrigeration can also be used to air-condition buildings using the waste heat from a gas

turbine or water heater . This use is very efficient, since the gas turbine produces electricity, hot water and air-conditioning (called trigeneration ).

Both absorption and compressor refrigerators use a refrigerant with a very low boiling point

(less than 0 °F/−18 °C). In both types, when this refrigerant evaporates (boils), it takes some

heat away with it, providing the cooling effect. The main difference between the two types is

the way the refrigerant is changed from a gas back into a liquid so that the cycle can repeat.

An absorption refrigerator changes the gas back into a liquid using a different method that

needs only heat, and has no moving parts [1]. The other difference between the two types is the

refrigerant used. Compressor refrigerators typically use an HCFC or HFC , while absorption

refrigerators typically use ammonia or water .

Principles

Absorptive refrigeration uses a source of heat to provide the energy needed to drive the

cooling process.

51

http://en.wikipedia.org/wiki/Refrigerator

http://en.wikipedia.org/wiki/Solar_thermal_energy

http://en.wikipedia.org/wiki/Vapor-compression_refrigeration

http://en.wikipedia.org/wiki/Combustion

http://en.wikipedia.org/wiki/Liquefied_petroleum_gas


http://en.wikipedia.org/wiki/Recreational_vehicle

http://en.wikipedia.org/wiki/Air_conditioning

http://en.wikipedia.org/wiki/Gas_turbine


http://en.wikipedia.org/wiki/Water_heater

http://en.wikipedia.org/wiki/Electricity

http://en.wikipedia.org/wiki/Trigeneration

http://en.wikipedia.org/wiki/Boiling_point

http://en.wikipedia.org/wiki/Absorption_refrigerator#cite_note-0


http://en.wikipedia.org/wiki/Chlorofluorocarbon

http://en.wikipedia.org/wiki/Organofluorine_chemistry#Hydrofluorocarbons

http://en.wikipedia.org/wiki/Ammonia

http://en.wikipedia.org/wiki/Water

http://en.wikipedia.org/wiki/Heat

http://en.wikipedia.org/wiki/Refrigerator

http://en.wikipedia.org/wiki/Solar_thermal_energy

http://en.wikipedia.org/wiki/Vapor-compression_refrigeration

http://en.wikipedia.org/wiki/Combustion



http://en.wikipedia.org/wiki/Recreational_vehicle

http://en.wikipedia.org/wiki/Air_conditioning



http://en.wikipedia.org/wiki/Water_heater

http://en.wikipedia.org/wiki/Electricity

http://en.wikipedia.org/wiki/Trigeneration



http://en.wikipedia.org/wiki/Chlorofluorocarbon

http://en.wikipedia.org/wiki/Organofluorine_chemistry#Hydrofluorocarbons



http://en.wikipedia.org/wiki/Heat



Absorption

The absorption cooling cycle can be described in three phases:

1. Evaporation: A liquid refrigerant evaporates in a low partial pressure environment,

thus extracting heat from its surroundings – the refrigerator.

2. Absorption: The gaseous refrigerant is absorbed – dissolved into another liquid -

reducing its partial pressure in the evaporator and allowing more liquid to evaporate.

3. Regeneration: The refrigerant-laden liquid is heated, causing the refrigerant to

evaporate out. It is then condensed through a heat exchanger to replenish the supply

of liquid refrigerant in the evaporator.

[edit ] Simple salt and water system

A simple absorption refrigeration system common in large commercial plants uses a solution

of lithium bromide salt and water. Water under low pressure is evaporated from the coils that

are being chilled. The water is absorbed by a lithium bromide/water solution. The water is

driven off the lithium bromide solution using heat. [3]

[edit ] Water spray absorption refrigeration

Water Spray Absorption Refrigeration

Another variant, depicted to the right, uses air, water, and a salt water solution. The intake of

warm, moist air is passed through a sprayed solution of salt water. The spray lowers thehumidity but does not significantly change the temperature. The less humid, warm air is then

52

http://en.wikipedia.org/wiki/Partial_pressure

http://en.wikipedia.org/w/index.php?title=Absorption_refrigerator&action=edit&section=2

http://en.wikipedia.org/wiki/Lithium_bromide



http://en.wikipedia.org/wiki/File:Absorptive_refrigeration.svg

http://en.wikipedia.org/wiki/File:Absorptive_refrigeration.svg

http://en.wikipedia.org/wiki/File:Absorbtion.png

http://en.wikipedia.org/wiki/File:Absorbtion.png



http://en.wikipedia.org/wiki/Lithium_bromide





passed through an evaporative cooler , consisting of a spray of fresh water, which cools and

re-humidifies the air. Humidity is removed from the cooled air with another spray of salt

solution, providing the outlet of cool, dry air.

The salt solution is regenerated by heating it under low pressure, causing water to evaporate.

The water evaporated from the salt solution is re-condensed, and rerouted back to the

evaporativecooler.

[edit ] Single pressure absorption refrigeration

Labeled photo of a domestic absorption refrigerator.

A single-pressure absorption refrigerator uses three substances: ammonia , hydrogen gas, and

water . At standard atmospheric conditions, ammonia is a gas with a boiling point of -33°C,

but a single-pressure absorption refrigerator is pressurised to the point where the ammonia is

a liquid. The cycle is closed, with all hydrogen, water and ammonia collected and endlessly

reused.

The cooling cycle starts with liquefied ammonia entering the evaporator at room temperature.

The ammonia is mixed in the evaporator with hydrogen. The partial pressure of the hydrogen

is used to regulate the total pressure, which in turn regulates the vapour pressure and thus the

boiling point of the ammonia. The ammonia boils in the evaporator, providing the cooling

required.

53

http://en.wikipedia.org/wiki/Evaporative_cooler



http://en.wikipedia.org/wiki/Hydrogen



http://en.wikipedia.org/wiki/Vapour_pressure


http://en.wikipedia.org/wiki/File:Absorption_fridge.jpg

http://en.wikipedia.org/wiki/File:Absorption_fridge.jpg

http://en.wikipedia.org/wiki/Evaporative_cooler



http://en.wikipedia.org/wiki/Hydrogen



http://en.wikipedia.org/wiki/Vapour_pressure




The next three steps exist to separate the gaseous ammonia and the hydrogen. First, in the

absorber, the mixture of gasses enters the bottom of an uphill series of tubes, into which

water is added at the top. The ammonia dissolves in the water, producing a mixture of

ammonia solution and hydrogen. The hydrogen is collected at the top of the absorber, with

the ammonia solution collected at the bottom.

The second step is to separate the ammonia and water. In the generator, heat is applied to the

solution, to distill the ammonia from the water. Some water remains with the ammonia, in the

form of vapour and bubbles. This is dried in the final separation step, called the separator, by

passing it through an uphill series of twisted pipes with minor obstacles to pop the bubbles,

allowing the collected water to drain back to the generator.

Finally the pure ammonia gas enters the condenser. In this heat exchanger , the hot ammonia

gas is cooled to room temperature and hence condenses to a liquid, allowing the cycle to

restart.

Miller cycle

In engineering , the Miller cycle is a combustion process used in a type of four-stroke internal

combustion engine . The Miller cycle was patented by Ralph Miller, an American engineer, in

the 1940s.

[edit ] Overview

This type of engine was first used in ships and stationary power-generating plants, but was

adapted by Mazda for their KJ-ZEM V6, used in the Millenia sedan, and in their Eunos 800

sedan (Australia) luxury cars. More recently, Subaru has combined a Miller cycle flat-4 with

a hybrid driveline for their concept "Turbo Parallel Hybrid" car, known as the Subaru B5-

TPH .

A traditional Otto cycle engine uses four "strokes", of which two can be considered "high

power" — the compression stroke (high power consumption) and power stroke (high power

54

http://en.wikipedia.org/wiki/Solution

http://en.wikipedia.org/wiki/Distillation

http://en.wikipedia.org/wiki/Heat_exchanger

http://en.wikipedia.org/wiki/Engineering

http://en.wikipedia.org/wiki/Four-stroke_cycle

http://en.wikipedia.org/wiki/Internal_combustion_engine


http://en.wikipedia.org/w/index.php?title=Ralph_Miller_(engineer)&action=edit&redlink=1

http://en.wikipedia.org/wiki/United_States

http://en.wikipedia.org/w/index.php?title=Miller_cycle&action=edit&section=1

http://en.wikipedia.org/wiki/Mazda

http://en.wikipedia.org/wiki/Mazda_K_engine#KJ-ZEM


http://en.wikipedia.org/wiki/V6

http://en.wikipedia.org/wiki/Mazda_Millenia

http://en.wikipedia.org/wiki/Subaru

http://en.wikipedia.org/wiki/Flat-4

http://en.wikipedia.org/wiki/Hybrid_car

http://en.wikipedia.org/wiki/Subaru#Concept_cars



http://en.wikipedia.org/wiki/Solution

http://en.wikipedia.org/wiki/Distillation

http://en.wikipedia.org/wiki/Heat_exchanger





http://en.wikipedia.org/w/index.php?title=Ralph_Miller_(engineer)&action=edit&redlink=1

http://en.wikipedia.org/wiki/United_States

http://en.wikipedia.org/w/index.php?title=Miller_cycle&action=edit&section=1

http://en.wikipedia.org/wiki/Mazda


http://en.wikipedia.org/wiki/V6

http://en.wikipedia.org/wiki/Mazda_Millenia

http://en.wikipedia.org/wiki/Subaru

http://en.wikipedia.org/wiki/Flat-4

http://en.wikipedia.org/wiki/Hybrid_car






production). Much of the internal power loss of an engine is due to the energy needed to

compress the charge during the compression stroke, so systems that reduce this power

consumption can lead to greater efficiency.

In the Miller cycle, the intake valve is left open longer than it would be in an Otto cycle

engine. In effect, the compression stroke is two discrete cycles: the initial portion when the

intake valve is open and final portion when the intake valve is closed. This two-stage intake

stroke creates the so called "fifth" stroke that the Miller cycle introduces. As the piston

initially moves upwards in what is traditionally the compression stroke, the charge is partially

expelled back out the still-open intake valve. Typically this loss of charge air would result in

a loss of power. However, in the Miller cycle, this is compensated for by the use of a

supercharger . The supercharger typically will need to be of the positive displacement ( Roots

or Screw) type due to its ability to produce boost at relatively low engine speeds. Otherwise,

low-rpm torque will suffer.

A key aspect of the Miller cycle is that the compression stroke actually starts only after the

piston has pushed out this "extra" charge and the intake valve closes. This happens at around

20% to 30% into the compression stroke. In other words, the actual compression occurs in the

latter 70% to 80% of the compression stroke.

In a typical spark ignition engine, the Miller cycle yields an additional benefit. The intake air

is first compressed by the supercharger and then cooled by an intercooler . This lower intake

charge temperature, combined with the lower compression of the intake stroke, yields a lower

final charge temperature than would be obtained by simply increasing the compression of the

piston. This allows ignition timing to be advanced beyond what is normally allowed before

the onset of detonation, thus increasing the overall efficiency still further.

An additional advantage of the lower final charge temperature is that the emission of NOx in

diesel engines is decreased, which is an important design parameter in large diesel engines on

board ships and power plants.

Efficiency is increased by raising the compression ratio . In a typical gasoline engine, the

compression ratio is limited due to self-ignition (detonation) of the compressed, and therefore

hot, air/fuel mixture. Due to the reduced compression stroke of a Miller cycle engine, a

55

http://en.wikipedia.org/wiki/Supercharger

http://en.wikipedia.org/wiki/Roots_blower

http://en.wikipedia.org/wiki/Intercooler

http://en.wikipedia.org/wiki/Compression_ratio

http://en.wikipedia.org/wiki/Supercharger

http://en.wikipedia.org/wiki/Roots_blower

http://en.wikipedia.org/wiki/Intercooler

http://en.wikipedia.org/wiki/Compression_ratio



higher overall cylinder pressure (supercharger pressure plus mechanical compression) is

possible, and therefore a Miller cycle engine has better efficiency.

The benefits of utilizing positive displacement superchargers come with a cost. 15% to 20%

of the power generated by a supercharged engine is usually required to do the work of driving

the supercharger, which compresses the intake charge (also known as boost).

A similar delayed-valve closing method is used in some modern versions of Atkinson cycle

engines, but without the supercharging. These engines are generally found on hybrid electric

vehicles, where efficiency is the goal, and the power lost compared to the Miller cycle is

made up through the use of electric motors

Lenoir cycle

The Lenoir cycle is an idealized thermodynamic cycle often used to model a pulse jet engine.

It is based on the operation of an engine patented by Jean Joseph Etienne Lenoir in 1860.

This engine is often thought of as the first commercially produced internal combustion

engine. The absence of any compression process in the design leads to lower thermal

efficiencies than the more well known Otto cycle and Diesel cycle .

In the cycle, an ideal gas undergoes

1-2: Constant volume ( isochoric ) heat addition;

2-3: Isentropic expansion;

3-1: Constant pressure ( isobaric ) heat rejection—compression to the volume at the

start of the cycle.

The expansion process is isentropic and hence involves no heat interaction.

Energy is absorbed as heat during the isochoric heating and rejected as work

during the isentropic expansion. Waste heat is rejected during the isobaric

cooling which consumes some work.

Turbocharger for two wheelers

This mechanical engineering project deals with turbocharging a two wheeler .

56

http://en.wikipedia.org/wiki/Atkinson_cycle

http://en.wikipedia.org/wiki/Hybrid_electric

http://en.wikipedia.org/wiki/Thermodynamic_cycle

http://en.wikipedia.org/wiki/Pulse_jet_engine

http://en.wikipedia.org/wiki/Jean_Joseph_Etienne_Lenoir

http://en.wikipedia.org/wiki/Otto_cycle

http://en.wikipedia.org/wiki/Diesel_cycle

http://en.wikipedia.org/wiki/Ideal_gas

http://en.wikipedia.org/wiki/Isochoric

http://en.wikipedia.org/wiki/Isentropic_process

http://en.wikipedia.org/wiki/Isobaric_process


http://www.mechanicalengineeringprojects.net/turbocharger-for-two-wheelers/2010/

http://en.wikipedia.org/wiki/Atkinson_cycle

http://en.wikipedia.org/wiki/Hybrid_electric

http://en.wikipedia.org/wiki/Thermodynamic_cycle

http://en.wikipedia.org/wiki/Pulse_jet_engine

http://en.wikipedia.org/wiki/Jean_Joseph_Etienne_Lenoir

http://en.wikipedia.org/wiki/Otto_cycle

http://en.wikipedia.org/wiki/Diesel_cycle

http://en.wikipedia.org/wiki/Ideal_gas

http://en.wikipedia.org/wiki/Isochoric


http://en.wikipedia.org/wiki/Isobaric_process


http://www.mechanicalengineeringprojects.net/turbocharger-for-two-wheelers/2010/



Turbocharging is usually carried out in diesel engines. This is because turbocharges work

using the pressure from the exhaust gas (For diesel engines the compression ratio is high and

hence the pressure.). But it can be used in petrol engines also if the engine is 4 cylindered or

more.

Turbocharging a bike is possible only if it is a 4 cylinder one. Usually only performance

bikes are turbocharged. It is also possible to improve the performance of a bike using nitro

injection, bigger carburettors etc, but the advantage of turbocharging its stock engine is that

you save a lot of money and at the same time obtain better performance.

ALLOWANCE – The intentional or desired difference between the maximum limits of

mating parts to provide a certain class of fit.ACHME THREAD – A screw thread having an included angle of 29° and largely used for

feed screws on machine tools.

ANNULUS – A figure bounded by concentric circles or cylinders ( e.g., a washer, ring, sleeve

etc.).

BEVEL - Any surface not at right angle to the rest of the workpiece. If a bevel is at a 45°

angle, it is frequently called a MITER.

BIMETALLIC STRIP - A strip of metal consisting of one metal (or alloy) in the top portion

bonded to a different metal in the bottom portion.A straight strip becomes curved when

heated.

BRUSH - Pieces of carbon or copper that make a sliding contact against the commutator or

slip rings.

CAM - A plate or cylinder which transmits variable motion to a part of a machine by means

of a follower.

CHAMFER – To bevel or remove the sharp edge of a machined part.

CHECK VALVE – A valve which permits flow in one direction only.

CIRCULAR PITCH – The distance from the center of one gear tooth to the center of the

next gear tooth measured on the pitch line.

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COMMUTATOR – A number of copper bars connected to the armature windings but

insulated from each other and from the armature.

CONVOLUTION – One full turn of screw.

ECCENTRIC – A circle or cylinder having a different center from another coinciding circle

or cylinder. Also, a device for converting rotary motion to reciprocating motion.

FEATHER – A sliding key, sometimes called splint. Used to prevent a pulley, gear or other

part from turning on a shaft but allows it to move lengthwise. The feather is usually fastened

to the sliding piece.

FILLET – A concave surface connecting the two surfaces meeting at an angle

.

FLANGE – A metal part which is spread out like a rim, the action of working

a piece or part to spread out.

FLANK (Side of thread) – The straight part of the thread which connects

the crest with the root.

FLARE – To open or spread outwardly.

FULCRUM – The pivot point of a lever.

FLUSH – When the surfaces of different parts are on the same level, they are said to be

flush.

FLUTE – A straight or helical groove of angular or radial form machined in a cutting tool to

provide cutting edges and to permit chips to escape and the cutting fluid to reach the cutting

edges.

GATE VALVE – A common type of manually operated valve in which a sliding gate is used

to obstruct the flow of fluid.

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GEAR – A general term applied to types of toothed wheels, valve motion, pump works,

lifting tackle and ropes.

GEARING – A train of gears or an arrangement of gears for transmitting motion in a

machinery.

GIB – An angular or wedge like strip of metal placed between two machine parts, usually

sliding bearings, to ensure a proper fit and provide adjustment for wear.

GLAND – A device to prevent the leakage of gas or liquid past a joint.

HAND WHEEL – Any of the various wheels found on machine tools for moving or

positioning parts of the machine by hand feed, as the tailstock handwheel on a lathe.

HALF MOON KEY – A fastening device in a shape somewhat similar to a semicircle.

HELICAL GEAR – A gear in which the teeth are cut at some angle other than a right angle

across the gear face.

HELICOIL – A thread insert used to repair worn or damaged threads. It is installed in a

retapped hole to bring the screw thread down to original size.

HELIX – The curve formed by a line drawn or wrapped around a cylinder which advances

uniformly along the axis for each revolution, as the thread on a screw or the flute on a twist

drill. A helix is often called a spiral in the shop.

HELIX ANGLE OF A THREAD – The angle made by the helix of the thread at the pitch

diameter line with a line at right angle to the axis.

HEXAGONAL NUT – A nut having six sides and shaped like a hexagon.

INVOLUTE GEAR TOOTH – A curved tooth generated by unwinding a string from a

cylinder to form the curve.

59



JOURNAL – The part of a shaft or axle that has been machined or finished to fit into a

bearing.

KEYS – Metal pieces of various designs that fit into a slot in a shaft and project above the

shaft to fit into a mating slot in the center hole of a gear or pulley to provide a positive drive

between the shaft and the gear or pulley.

KEYSEAT – The slot or recessed groove either in the shaft or gear, which is made to receive

the key. Also, it is called a KEYWAY.

KNURL – A uniform roughened or checked surface of either a diamond, a straight or other

pattern.

LAND – The top surface of a tooth of cutting tools, such as taps, reamers and milling cutters.

LEAD ANGLE – The angle of the helix of a screw thread or worm thread. It is the measure

of the inclination of a screw thread from a plane perpendicular to the axis of the screw.

LEAD HOLE – A small hole drilled in a workpiece to reduce the feed pressure, aid in

obtaining greater accuracy, and guide a large drill. Sometimes called PILOT HOLE.

LEAD OF THREAD – On a single threaded screw the distance the screw or nut advances in

one complete revolution.

PEEN – The end of the head of a hammer opposite the face, such as ball, straight or cross

peen, and used for peening or riveting.

PILOT – A guide at the end of the counter bore which fits freely into the drilled hole and

align the body of the counterbore while cutting takes place.

PILOT SHAFT – A shaft positioned in or through a hole of a component as a means of

aligning the components.

PILOT VALVE – A valve used to control the operation of another valve.

60



PINION – The smaller of the pair of gears regardless of the size or type.

PITCH – In screw threads, the distance from a point on one thread to a corresponding point

on the next thread measured parallel to the axis. In the case of spur gears, indicates the size of

the gear teeth and is correctly called diametral pitch.

PITCH DIAMETER – For screw threads, the diameter of an imaginary cylinder, the surface

of which would pass through the threads at such points that would make the width of the

groove and width of the land equal to one half the pitch.

RACK – A straight metal strip having teeth that mesh with those of a gear to convert rotary

into reciprocating motion or just the opposite.

RATCHET – A gear with triangular shaped teeth to be engaged by a pawl which gives it

intermittent motion or locks it against backward movement.

RIGHT HAND THREAD – A screw thread which advances into the mating part when

turned clockwise or to the right.

RIVET – A one piece fastener consisting of a head and a body and used for fastening two or

more pieces together by passing the body through a hole in each piece and then forming a

second head on the body end. It cannot be removed except by taking off the head.

SCREW – A helix formed or cut on a cylindrical surface which may advance along the axis

to the right or left. The helix may be single or multiple.

SCREW THREAD – A ridge of uniform section or shape in the form of a helix on the

external or internal surface of a cylinder, or in the form of a conical spiral on the external or

internal surface of a cone.

SPUR GEAR – A toothed wheel having external radial teeth.

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SQUARE THREAD – A form of screw thread in which the cross–section of the thread

forms a square, making the width of the thread equal to the space between the threads.

STUD – A rod having thread on both ends.

STUFFING BOX – A chamber having manual adjustment device for sealing.

TAPER – A shaft or hole that gets gradually smaller toward one end.

TAPER PINS – Steel pins used for locating and holding the machine parts in position on a

shaft.

TEMPLATE – A flat pattern or guide plate usually made from sheet metal and used as a

gauge or guide when laying out, drilling, forming in a machine or filing irregular shapes on

metal pieces.

VALVE – Any device or arrangement used to open or close an opening to permit or restrict

the flow of a liquid, gas or vapour.

V-BLOCKS – Square or rectangular shaped blocks of steel that are usually hardened and

accurately ground. These have 90° V groove through the center and are provided with clamps

for holding round workpiece for laying out, drilling, milling etc.

VISE – A mechanical device of many designs and sizes in which work pieces are clamped

for hand or machine operations.

V-WAYS – The top of the bed of a lathe, planer or other machine tool which acts as bearing

surface for aligning and guiding the moving parts such as the carriage of a lathe.

WORM – A threaded cylinder which meshes with and drives a worm gear, the thread being

specially designed to mate with the teeth in the worm gear.

WORM GEARS – Gears with teeth cut at an angle to be driven by a worm. The teeth areusually cut out with a hob to fit the worm.

62



ABRASIVE – A natural or artificial material such as sand stone, emery, aluminium oxide or

silicon carbide.

ACID – A chemical term to define a material which gives an acid reaction.

ADDITIVES – Chemicals added to oil or fuel to increase its effectiveness and obtain

desirable qualities.

ADHESIVES – Materials or compositions that enable two surfaces to join together. An

adhesive is not necessarily a glue, which is considered to be a sticky substance, since many

adhesives are not sticky.

AGGREGATE – Small particles such as powders that are used for powder metallurgy, that

are loosely combined to form a whole, also sand and rock as used in concrete.

ALLOTROPIC METALS – Metals which exist in one lattice form over a range of

temperature, but at a certain temperature the lattice form changes to another type which is

stable over another temperature range.

ALNICOS – Alnicos materials are composed mainly of aluminium, nickel, cobalt and iron.

Some include additions of copper and titanium. They are high-coercive force, high magnetic

energy alloys.

ALOXITE – Artificial abrasive material used in the manufacture of grinding wheels.

Essentially it consists of alumina, or aluminium oxide, the chemical symbol for which is

Al2O3·

ALUMEL – A nickel base alloy containing about 2.5% Mn, 2% AI, and 1 % Si, used chiefly

as a component of pyrometric thermocouples.

ANTIFREEZE – A chemical added to the coolant in order to lower its freezing point.

63



ANTIFRICTION BEARINGS – Ball, roller and needle bearings exhibit very low friction

and are suitable for very high speeds, and high loading.

ANTIMONY – Brittle, bluish white metallic element designated Sb. Melting point 630°C.

Used as a constituent in some alloys, for instance, bearings and storage battery plates.

BABBITT METAL – White metal bearing alloy, suitable for bearings

subjected to moderate pressures, contains tin 59.5% min, copper 2.25-

3.75%, antimony 9.5-11.5%, lead 26% min, iron 0.08% max, bismuth

0.08% max.

BACKING SAND – Foundry sand placed next to the facing sand after the

latter is in place. It forms the bulk of sand used to complete the mould.

BAINITE – A structure in steel named after E.G. Bain that forms between

481° C and the M’s temperature. At the higher temperatures, it is known

as upper or feathery bainite. At the lower temperatures it is known as

lower or a acicular bainite and resembles martensite.

BAKELITE – Trade name for one of the first used thermo-setting synthetic

resins. It is derived from the name of the inventor Dr. L.H. Backeland,

and its formation is the result of a chemical action between formaldehyde

and phenol.

BARK – The decarborized layer just beneath the scale that results from heating

steel in an oxidizing atmosphere.

BASE METAL – Metal present in the alloy in largest proportion.

BEARING METALS – Metals (alloys) used for that part of a bearing which

is in contact with the journal e.g. , bronze or white metal, used on account

of their low coefficient of friction when used with a steel shaft.

BELL METAL – High tin bronze, used in the casting of bells, which is

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composed of up to 30% tin, together with some zinc and lead.

BESSEMER STEEL – Steel manufactured in a Bessemer converter, and

sometimes referred to as mild steel.

BILLET – A solid semifinished round or square product that has been hot

worked by forging, rolling or extrusion.

BLUE VITRIOL – A chemical mixture of copper sulphate, water and

sulphuric acid. Applied to polished metal for layout purposes, it turns

to copper colour.

BOND – In grinding wheels and other relatively rigid abrasive products, the

material that holds the abrasive grains together. In welding, the junction

of joined parts.

BORON CARBIDE – An abrasive used in cutting tools, a compound whose

chemical formula is B4 C and obtained from borontrioxide (B2O3) and

coke at a temperature of 2500°C. Fine powder as hard as diamond.

BRASS – A range of copper zinc alloys, usually those containing 55-80%

copper. Alloys containing not less than 63% of copper are called ALPHA

BRASSES. When less than 63% of copper is present, the alloy is called

ALPHA-BETA alloy.

BRAZING ALLOY – Copper zinc alloy, which sometimes includes small

percentages of tin, and lead, used for brazing, the melting point of

which is governed by the percentage of zinc.

BRINE – Water that has been saturated or nearly saturated with salt.

CAPPED STEEL – Semiskilled steel cast in a bottle top mould and covered

with a cap fitting into the neck of the mould. The cap causes the topmetal to solidify. Pressure is build up in the sealed in molten metal and

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results in a surface condition much like that of RIMMED STEEL

CARBON STEEL – Steel containing carbon up to about 2% and only

residual quantities of other elements except those added for deoxidation,

with silicon usually limited to 0.60% and manganese to about 1.65%.

Also termed PLAIN CARBON STEEL.

CARBORUNDUM – Artificially manufactured abrasive, trade name for a

carbide of silicon (SiC) which is prepared by heating sand with coke in

an electric furnace.

CARTRIDGE BRASS – Alloy containing about 70% copper and 30% zinc,

in which impurities are kept to a minimum, and it possesses a high

degree of strength, combined with good ductility

CEMENTED CARBIDE – A solid and coherent mass made by pressing and

sintering a mixture of powders of one or more metallic carbides, and a

much smaller amount of a metal, such as cobalt, to serve as a binder.

CEMENTITE – Hard, brittle, crystalline iron carbide (compound of iron

and carbon Fe3C) found in steels having a high carbon content. It is

characterized by an orthorhombic crystal structure. When it occurs as a

phase in steel, the chemical composition will be altered by the presence

of manganese and other carbide forming elements.

CERAMIC – Metallic oxides of metals such as silicon and aluminium.

CERAMIC MATERIALS – The materials that demonstrate great hardness and

resistance to heat and are used to make cutting tools, coatings on tools,

parts subjected to very hot conditions, abrasives and mechanical parts

CESIUM 13T – A radioisotope, recovered as a fission product from nuclear

reactors, with a half-life of 33 years and a dominant characteristic gammaradiation of 0.66 mev. It is suitable as a gamma radiation source,

66



especially in radiography and therapy

CHILL – (1) A metal insert embedded in the surface of a sand mould or core

or placed in a mould cavity to increase cooling rate at that point. (2)

White iron occurring on a gray iron casting such as the chill in the

wedge test.

CHROMEL – (1) 90% Ni, 10% Cr alloy used in thermocouples. (2) A

series of Nickel chromium alloys, some with iron, used for heat resistant

applications.

CHROMIUM – Grayish white metallic element obtained from chromite,

chemical symbol is Cr and melting point 1830°C, used in alloying

steels and corrosion resisting plating.

CLAD METAL – A composite material containing two or three layers that

have been bonded together. The bonding may have been accomplished

by rolling, welding, casting, heavy chemical deposition or heavy

electroplating.

COAL TAR – Also called crude oil, when subjected to fractional distillation

and purification, yields a variety of useful products-neutral, acidic, and

base oils.

COBALT-60 – A radio isotope with a half-life of 5.2 years and dominant

characteristic gamma radiation energies of 1.17 and 1.33 MeV. It is

used as a gamma radiation source in industrial radiography and therapy.

COLD FINISHED STEEL – Steel bar which has been cold drawn/cold

rolled, centerless ground or turned smooth to improve surface finish,

accuracy or mechanical properties.

COLD ROLLED STEEL – Steel which has been passed through rollers atthe steel mill to size it accurately and smoothly.

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COLLOIDS – Finely divided material, less than 0.5 micron in size, gelatinous,

highly absorbent and sticky when moistened.

COLUMNAR STRUCTURE – A coarse structure of parallel columns of

grains having the long axis perpendicular to the casting surface.

COMPOSITE FIBRES – The strands of material used as reinforcement

extending through a resin or other matrix in a composite material. An

example is carbon fibres in an epoxy matrix. Loads applied to the

structure are carried by the fibres.

COMPOSITE MATERIAL – Materials exhibiting a much higher strength

than the matrix or base material because of reinforcement fibres.

CONDUCTORS (electrical) – Materials in which an electromotive force

causes appreciable drift of electrons, called CURRENT.

CONSTANTAN – A group of copper nickel alloys containing 45-60%

copper with minor amounts of iron and manganese and characterized

by relatively constant electrical resistivity irrespective of temperature

used in resistors and thermocouples.

CONVERSION COATING – A coating consists of a compound of the surface

metal produced by chemical or electro-chemical treatments of the metal.

CORUNDUM – Natural abrasive of the aluminium oxide type that has

higher purity than emery

CRUCIBLE – A vessel or pot, made of refractory substance or of a metal

with a high melting point, used for melting metals or other substances.

CRUCIBLE STEEL – A high grade steel made by melting iron in a crucible

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and adding charcoal, pig iron and some substance rich in carbon so that the resulting metal

will contain from 0.75-1.5% carbon. This steel is

used for tools, dies and better grades of cutlery.

CRYSTALLOID – A substance that forms a true solution and is capable of

being crystallized.

CURIE – The quantity of a radioactive nuclide in which the number of

disintegrations per second is 3. 700 × 10 to the power of ten.

CUTTING FLUID – A fluid, usually a liquid, used in metal cutting to

improve finish, tool life or dimensional accuracy.

DEGASIFIER – A material employed for removing gases from metals and

alloys.

DELTA IRON – An allotropic (polymorphic) form of iron, stable above

1390oC, crystallizing in the body centered cubic lattice.

DENDRITE – A crystal that has tree like branching pattern, being most

evident in cast metals slowly cooled through the solidification range.

Dendrite generally grow inward from the surface of a mould.

DEOXIDIZER – A substance that is used to remove either free or combined

oxygen from molten metals, for example, ferrosilicon in steel making.

DIAMAGNETIC SUBSTANCES – Actually set up fields that oppose

applied fields.

DIAMOND – Allotropic form (crystalline form) of carbon (the hardest

known mineral) which when very strongly heated, changes to graphite.

Used as a cutting tool, and a grinding tool and to dress grinding wheels.

DROSS – The scum that forms on the surface of molten metals largely

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because of oxidation but sometimes because of the rising of impurities

to the surface.

DURALUMIN – Aluminium alloy containing copper, manganese and

magnesium, which can be cast, forged or stamped, and is widely used

for sheets, tubes, forgings, rivets, nuts, bolts and similar parts.

DYE PENETRANT – Penetrant with a dye added to make it more readily

visible under normal lighting conditions.

ELASTOMER – Any of various elastic substances resembling rubber.

ELECTRIC STEEL – Special alloy steel, tool steel, and steel for castings,

melted in electric furnaces that permit very close control and the addition

of alloying elements directly into the furnaces.

ELECTRICAL SHEETS – It is the trade name for iron and steel sheets used

in the manufacture of punchings for laminated magnetic circuits and

usually refers to silicon steel sheets.

ELECTROLYTE – A non-metallic conductor, usually a fluid, in which

electric current is carried by the movement of ions.

ELECTROMAGNET – A magnet of variable strength produced by passing

current through conductors around a soft iron core.

ELEKTRON – Magnesium base alloy supplied in the form of tubes, sheets,

extruded sections, forgings and castings

EMERY – An abrasive material which, like corundum or aluminium oxide

type, is a natural abrasive.

EMULSIFIER – (1) A material that increases the stability of dispersion of one liquid in another. (2) In penetrant inspection, a material that is

70



added to some penetrants after the penetrant is applied to make a water

washable mixture.

ENAMEL – Type of paint that dries to a smooth, glossy finish.

FIBRE GLASS – A resin matrix reinforced with glass fibres for strength. A

reinforced plastic manufacturing material with many applications.

FILTER – In radiography a device, usually, a thin metallic layer inserted into

a beam of radiation so as to modify the transmitted spectrum of

radiation. It may be used to enhance or reduce contrast or minimize

undesirable scattered radiation.

FIRE BRICK – Brick made of refractory clay or other material which resists

high temperatures.

FIRE CLAY – A type of clay which is resistant to high temperatures.

FLUX – A solid, liquid or gaseous material that is applied to solid or molten

metal in order to clean and remove oxides.

FOAM RUBBER – It is also called sponge. Foam rubbers are formed by the

inclusion of chemicals in rubber compounding which form gases during

vulcanization.

FREE CARBON – The part of the total carbon in steel or cast iron that is

present in the elemental form as graphite or temper carbon.

HIGH CARBON STEEL – Steel that has more than 0.6% carbon.

HIGH SPEED STEEL – Alloy steel (alloying elements being tungsten,

chromium, vanadium, cobalt and molybdenum) which retains its

strength and hardness at red heat, and is thus suitable for cutting tools

which reach high temperatures in use.

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HINDU MINIUM – A high strength aluminium alloy containing, in addition

to aluminium, magnesium, iron, titanium, copper, nickel and silicon,

which after heat treatment has a strength exceeding that of mild steel.

HOT ROLLED STEEL – Steel rolled to shape while being heated to the

plastic condition.

HOYT METAL – Commercial grade of white metal used for bearing purpose.

HYPER EUTECTIC ALLOY – Any binary alloy whose composition lies to

the right of the EUTECTIC on an equilibrium diagram and which

contains some eutectic structure.

HYPO EUTECTIC ALLOY – Any binary alloy whose composition lies to

the left of the EUTECTIC on an equilibrium diagram and which

contains some eutectic structure.

IMPURITIES – Elements or compounds whose presence in a material is

undesired.

INCONEL – Nickel alloy highly resistant to heat and corrosion, with good

mechanical properties, consisting of 80% nickel, 12-14% chromium,

the balance being iron.

INERT GAS – A gas that may be used as a shield in welding or heat treatment

to prevent oxidation or scaling.

INGOT – A large block of metal that is usually cast in a metal mould and

forms the basic material for further rolling and processing

INVAR – Nickel iron alloy (35-36% nickel, 0.5% carbon and 0.5%

manganese, the remainder being iron) having a very low coefficient of

thermal expansion at ordinary temperatures

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KILLED STEEL – Steel that has been deoxidized with agents such as silicon

or aluminium to reduce the oxygen content to such a level that no

reaction occurs between carbon and oxygen during solidification. This

prevents gases from evolving during solidification.

LAMINATE – (1) A composite metal, usually in the form of sheet or bar,

composed of two or more metal layers so bonded that the composite

metal forms a structural member. (2) To form a metallic product of

two or more bonded layers.

LAMINATIONS – Metal defects with separation or weakness generally

aligned parallel to the worked surface of the metal.

LASER – Light Amplification by Simulated Emission of Radiation. A device

in which heat is derived from the intense coherent beam of laser light

energy. This intense, narrow beam of light is used in some welding and

machining operations.

LEAD – Heavy, bluish grey, soft, ductile metal, which has a specific gravity

of 11.3 and a melting point of 327°C, extensively used alone, and as

the basis of many antifriction alloys.

LEAD SCREEN – In radiography, a screen is used (1) to filter out soft wave

or scattered radiation and (2) to reduce the intensity of the remaining

radiation so that the exposure time can be decreased.

LEDEBURITE – The eutectic of the iron carbon system, the constituents

being austenite and cementite. The austenite decomposes into ferrite

and cementite on cooling below the transformation temperature.

LIGNIN – A substance that is related to cellulose, that with cellulose forms

the woody cell walls of plants and the material that cements them

together. Methyl alcohol is derived from lignin in the destructive

distillation of wood.

LOAM – Clayey sand mixture having the consistency of slime, and used in

73



the making of moulds and cores for heavy castings.

LOW CARBON STEEL – Steel containing less than 0.3% carbon.

LUTE – Fine adhesive composition of substances such as clay, sharp sand,

plumbago and horsedung tempered with water. Used for sealing joints

in moulds and cores, for the purpose of making them air or metal

MAGNETICALLY HARD ALLOY – A ferromagnetic alloy capable of being

magnetized permanently because of its ability to retain induced

magnetization and magnetic poles after the removal of externally applied

fields, an alloy with high coercive force.

MAGNETICALLY SOFT ALLOY – A ferromagnetic alloy that becomes

magnetized readily upon the application of a field and that return to

practically a non-magnetic condition when the field is removed, an

alloy with the properties of high magnetic permeability, low coercive

force, and low magnetic hysterisis loss

MALLEABLE CAST IRON – A cast iron made by a prolonged anneal of

WHITE CAST IRON in which decarbonization or graphitization, or

both, takes place to eliminate some or all of the CEMENTITE. The

graphite is in the form of temper carbon. This is less brittle than gray

cast iron.

MANGANESE BRONZE – A group of special alloys, not really bronzes at

all, containing about 1% manganese , 60% copper, 40% zinc and small

traces of iron, tin, lead or aluminium, the total percentage of these not

exceeding 5%.

MARTENSITE – An unstable constituent that is formed by heating and

quenching steel. It is formed without diffusion and only below a certain

temperature known as M’s temperature. Martensite is the hardest of the transformation products of austenite, having an acicular or needle

74



like microstructure

MEDIUM CARBON STEEL – Steel with a carbon content of 0.3-0.6%

METALLOID – A non-metal that exhibits some, but not all, of the properties

of a metal. Examples are sulphur, silicon, carbon, phosphorous and arsenic.

MILD STEEL – Carbon steel with a maximum of about 0.25% carbon.

MUNTZ METAL – Alloy of brass family containing 60% copper and 40%

zinc used for manufacturing condenser tubes.

MUSIC WIRE – A high carbon steel wire of the highest quality used for

making mechanical springs.

NAVAL BRASS – Alloy containing from 57.5-59.5% copper, 0.6-1.0% tin

and not more than 0.75% of impurities, the balance being zinc

(addition of tin improves the resistance of the alloy to corrosion by sea

water). Used for under-water fittings of marine craft.

NICHROME – Alloy of nickel and chromium which is practically noncorrosive,

can withstand high temperature without oxidation and is

used for furnace components.

NICKEL BRONZE – Bronze alloy of which there are two main series (1)

low nickel bronze (nickel below 5%) used, for bronze castings, and (2)

high nickel bronze (nickel over 10%) resistant to heat, and to corrosive

attack from chemical liquors.

NICKEL SILVER – Also called GERMAN SILVER. Alloy with composition

copper 60%, zinc 20%, and nickel 20%. Class of alloys used in the

manufacture of electrical resistance coils and elements, decorative articles

for which its lustrous colour (which increases in whiteness with nickelcontent) make it very suitable, or for heavy duty works such as high

75



pressure steam fittings.

NICROSILAL – A nickel-chromium alloy cast iron having a composition

1.7% carbon, 4.5% silicon, 0.8% manganese, 18.0% nickel, and 2%

chromium, the balance is iron.

NIRESIST IRON – Alloy cast iron (typical composition 14% nickel, 1.5%

silicon, 1 % manganese, and 3% carbon and remainder iron) which

possesses exceptional resistance to heat and corrosion.

NODULAR CAST IRON – A cast iron that has been treated while molten

with a master alloy containing an element such as magnesium or cerium

to give primary graphite in the spherulitic form.

NODULAR GRAPHITE – Graphite or carbon in the form of spheroids.

NUCLEUS – (1) The first structurally stable particle capable of initiating

recrystallization of a phase or the growth of a new phase and possessing

an interface with the parent matrix. (2) The heavy central core of an

atom in which most of the mass and the total positive electric charge

are concentrated.

NYLON – A group of plastics of nitrogenous structure known as polyamides

which are crystalline in nature and can be so processed as to orient the

crystals axially thus making the tensile strength of fibres extremely high.

OIL STONE – An abrasive stone that is oiled and used to sharpen cutting

tools.

OSMIUM – Osmium is the heaviest of all metals (sp gr. 22. 48), which

melts at 4900°F and is harder than glass and quartz.

PARAMAGNETIC MATERIALS – These materials are only feeblymagnetic.

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PARTING SAND – Fine sand used for dusting on sand mould surfaces that

are to be separated.

PHOSPHOR BRONZE – Alloy containing 78.5-81.5% copper, 9-11 %

tin, 9-11 % lead, 0.05-0.25% phosphorous and 0.75% zinc, has

excellent antifriction properties. Used as bearing material

PITCH – Usually coal tar pitch obtained in the manufacture of coke and distilled off at about

175°C.

PLASMA – An ionized gas of extremely high temperature achieved by passing

an inert gas through an electric arc. Plasma arcs are used in welding,

cutting and machining processes.

PLASTIC ELASTOMERS – Plastic elastomers are materials which exhibit

the characteristics of rubber, but are of a basic chemical structure that is

decidedly different from that of natural rubber.

PLATINUM – It is a silver-white heavy metal, unaffected by acids, air, or a

great variety of chemical agents. It is extensively used, either solid or

clad, for chemical equipment

PORCELAIN – Porcelain is a ceramic product made up of clays, quartz, and

feldspar used as high voltage insulator.

POWDER METALLURGY – Forming parts out of powdered metal by

compacting the powder into a mould under great pressure and heating

it.

PRECIOUS METAL – One of the relatively scarce and valuable metals–

gold, silver and platinum group of metals.

PRUSSIAN BLUE – A blue pigment, obtainable in tubes which is used to

77



find hot spots in a bearing.

QUICK SILVER – Metallic mercury.

RADIUM – A radio active element. It is found in nature as radium 226,

which has a half-life of 1620 years

RIMMED STEEL – A low carbon steel (insufficiently deoxized) that during

solidification releases considerable quantities of gases (mainly carbon

monoxide). When the mould top is not capped, a side and bottom rim

of several centimeters forms. The solidified ingot has got scattered blow

holes and porosity in the center but a relatively thick skin free from

blow holes

RUST – A corrosion product containing hydrated oxide of iron. Applied

only to ferrous alloys

SILICA – Silicon dioxide, SiO2 occurring in nature as quartz, opal etc.

SILICON – Non-metallic element which can be added to steel, cast iron

and non-ferrous alloys. It acts as a DEOXIDIZER, and also tends to

form graphite by throwing the carbon out of solution and thereby

increases the impact resistance of the steel, and, up to a silicon content

of 1.75%, the elastic limit is increased also

SLAG – The more or less completely fused and vitrified matter separated

during the reduction of a metal from its ore.

SLURRY – A watery mixture of insoluble material such as mud, lime or

plaster of paris.

SMOG – The irritating haze resulting from the sun’s effect on certain

pollutants in the air, notably those from automobile exhaust. Also amixture of fog and smoke.

78



SMOKE – Solid or liquid particles under 1 micron in diameter. Particles

suspended in air after incomplete combustion of materials containing

carbon. The matter in the exhaust emission which obscures the

transmission of light.

SODIUM SILICATE – Na2SiO3-Also called water gas.

SOLDERING ALLOY – Fusible alloy used to join together two metallic

surfaces with the aid of heat. Soft solder is an alloy of lead and tin, in

which the proportions of the two constituents may vary from almost

pure lead to almost pure tin.

SOLDERING FLUID – Liquid flux used when soldering.

SOLID SOLUTIONS – Solid solutions are alloys containing alloying

elements that are relatively soluble in the base metal in the solid state.

SORBITE – Structure consisting of evenly distributed carbide of iron particles

in a mass of ferrite, formed when a fully hardened steel is tempered at

between 550 and 650°C.

TROOSTITE – Structure in steel (consisting of very finely divided iron

carbide in what is known as “alpha iron”) produced either by tempering

a martensitic steel at between 250° and 450°C or by quenching steel at

a speed sufficient to suppress the thermal change point fully.

SPHEROIDITE – It is the structure in steel, in which cementite takes the

form of rounded particles, or spheroids, instead of plates.

STAINLESS STEEL – Steel which resists corrosion by the atmosphere and

the attack of acids and which does not scale when subjected to high

temperature. Alloy steels containing iron, atleast 11 % chromium, nickel,molybdenum and 0.1-1 % carbon.

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STELLITE – Non-ferrous alloy containing 35-80% cobalt, 10-40%

chromium, 0-25% tungsten and 0-10% molybdenum

TERNARY ALLOY – An alloy that contains three principal elements.

THERMIT – Powdered form of finely divided iron oxide and aluminium

which burns intensely to produce superheated liquid steel at a

temperature of about 30.35°C, used for welding wrought iron and

steel forgings and castings.

VANADIUM – A rare metal used as an alloying element in steel to improve

shock resistance and forgeability.

VULCANATES – Vulcanates are materials which reduce plasticity of the

rubber compound, while maintaining its elasticity.

WHITE IRON – An extremely hard cast iron that results from pouring the

hot metal into a mould with a chill plate in it.

WROUGHT IRON – Contains 1-2% slag, which is distributed through

the iron as threads and fibres imparting a tough fibrous structure. Usually

contains less than 0.1 % carbon. It is tough, malleable, and relatively

soft.

WROUGHT METALS – These are metals furnished in the shapes resulting

from the operations such as rolling, forging, drawing and extrusion.

YELLOW BRASS – An alloy of about 70% copper and 30% zinc.

MATERIAL PROPERTIES

ACICULAR STRUCTURE – A microstructure characterized by needleshaped constituents.

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ALLOTROPY – Ability of a material to exist in several crystalline forms.

AMORPHOUS – Non-crystalline, a random orientation of the atomic

structure.

ANISTROPY – A material that has specific physical properties in different

directions. Rolled steel is strongest in the direction of rolling.

CHLORINATION – A refining or degasification process, wherein dry

chlorine gas is passed through molten aluminium base and magnesium

base alloys to remove entrapped oxides and dissolved gases.

CLEAVAGE – Splitting (fracture) of a crystal in a crystallographic plane of

low index.

CLEAVAGE FRACTURE – A fracture, usually of a polycrystalline metal, in

which most of the grains have failed by cleavage, resulting in bright

reflecting facets. It is one type of crystalline fracture.

CLEAVAGE PLANE – A characteristic crystallographic plane or set of planes

on which cleavage fracture easily occurs.

COALESCENCE – The union of particles of a dispersed phase into larger

units, usually effected at temperatures below fusion point.

COHESIVE STRENGTH – (1) The hypothetical stress in an unnotched

bar causing tensile fracture without plastic deformation. (2) The stress

corresponding to the forces between atoms

COLUMNAR STRUCTURE – A coarse structure of parallel columns of

grains having the long axis perpendicular to the casting surface.

COMPLETE FUSION – Fusion which has occured over the entire base

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metal surfaces exposed for welding.

COOLING STRESSES – Residual stresses resulting from nonuniform

distribution of temperature during cooling.

CORROSION – The destructive chemical or electro-chemical reaction of a

material and its environment, usually associated only with metals in

contact with liquids.

CORROSION EMBRITTLEMENT – The severe loss of ductility of a

metal resulting from corrosive attack, usually intergranular and often

not visually apparent.

CORROSION FATIGUE – Effect of the application of repeated or

fluctuating stresses in a corrosive environment characterized by shorterlife than would be

encountred as a result of either the repeated or

fluctuating stresses alone or the corrosive environment alone.

COUPON – A piece of metal from which a test specimen is to be prepared,

often an extra piece as on a casting or forging.

COVALENT BOND – A bond between two or more atoms resulting from

the completion of shells by the sharing of electrons.

CRAZING – Minute surface cracks on the surface of materials often caused

by thermal shock.

CREEP – Slow plastic deformation in steel and most structural metals caused

by prolonged stress under the yield point at elevated temperatures.

CREEP LIMIT – (1) The maximum stress that will cause less than a specified

quantity of creep in a given time. (2) The maximum nominal stress

under which the creep strain rate decreases continuously with the timeunder constant load and at constant temperature. Sometimes called

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CREEP STRENGTH.

CRITICAL POINT – The temperature or pressure at which a change in

crystal structure, phase, or physical properties occur.

CRYSTALLIZATION – Act or process of forming crystals or bodies formed

by elements or compounds solidifying so that they are bounded by

plane surfaces.

Magneto

A magneto is an electrical generator that uses permanent magnets to produce alternating

current.

Hand-cranked magneto generators were used to provide ringing current in early telephone

systems.

Magnetos adapted to produce pulses of high voltage are used in the ignition systems of some

gasoline-powered internal combustion engines to provide power to the spark plugs .[1] The

magneto is now confined mainly to engines where there is no available electrical supply, for

example in lawnmowers and chainsaws. It is also universally used in aviation piston engines

even though an electrical supply is usually available. This is because a magneto ignition

system is more reliable than a battery-coil system.

Magnetos were rarely used for power generation , although they were for a few specialised

uses .

83

http://en.wikipedia.org/wiki/Electrical_generator

http://en.wikipedia.org/wiki/Magnet

http://en.wikipedia.org/wiki/Telephone

http://en.wikipedia.org/wiki/High_voltage

http://en.wikipedia.org/wiki/Ignition_system


http://en.wikipedia.org/wiki/Spark_plug

http://en.wikipedia.org/wiki/Magneto#cite_note-0


http://en.wikipedia.org/wiki/Lawnmower

http://en.wikipedia.org/wiki/Chainsaw

http://en.wikipedia.org/wiki/Aviation

http://en.wikipedia.org/wiki/Ignition_coil

http://en.wikipedia.org/wiki/Power_generation

http://en.wikipedia.org/wiki/Magneto_(generator)


http://en.wikipedia.org/wiki/File:Magnet_(PSF).png

http://en.wikipedia.org/wiki/File:Magnet_(PSF).png

http://en.wikipedia.org/wiki/Electrical_generator

http://en.wikipedia.org/wiki/Magnet

http://en.wikipedia.org/wiki/Telephone

http://en.wikipedia.org/wiki/High_voltage

http://en.wikipedia.org/wiki/Ignition_system


http://en.wikipedia.org/wiki/Spark_plug


http://en.wikipedia.org/wiki/Lawnmower

http://en.wikipedia.org/wiki/Chainsaw

http://en.wikipedia.org/wiki/Aviation

http://en.wikipedia.org/wiki/Ignition_coil

http://en.wikipedia.org/wiki/Power_generation





Rotary engine

The rotary engine was an early type of internal-combustion engine , usually designed with an

odd number of cylinders per row in a radial configuration , in which the crankshaft remained

stationary and the entire cylinder block rotated around it. Its main application was in aviation,

although it also saw use in a few early motorcycles and cars .

This type of engine was widely used as an alternative to conventional in-line or V engines

during World War I and the years immediately preceding that conflict, and has been

described as "a very efficient solution to the problems of power output, weight, and

reliability". [1]

By the early 1920s, however, the

inherent limitations of this type of

engine had rendered it obsolete,

with the power output increasingly

going into overcoming the air-

resistance of the spinning engine

itself. The rotating mass of the

engine also had a significant

gyroscopic precession : depending

on the type of aircraft, this produced

stability and control problems,

especially for inexperienced pilots.

Another factor in the demise of the

rotary was the fundamentally

inefficient use of fuel and

lubricating oil caused in part by the need for the fuel/air mixture to be aspirated through the

hollow crankshaft and crankcase.

Starter motor

A starter motor (also starting motor or starter ) is an electric motor for rotating an internal-

combustion engine so as to initiate the engine's operation under its own power.

84

An 80 horsepower rated Le Rhône 9C , a typical rotary

engine of WWI. The copper pipes carry the fuel-air

mixture from the crankcase to the cylinder heads.

http://en.wikipedia.org/wiki/Internal-combustion_engine

http://en.wikipedia.org/wiki/Radial_engine

http://en.wikipedia.org/wiki/Crankshaft

http://en.wikipedia.org/wiki/Cylinder_block

http://en.wikipedia.org/wiki/Motorcycle

http://en.wikipedia.org/wiki/Automobile

http://en.wikipedia.org/wiki/Straight_engine

http://en.wikipedia.org/wiki/V_engine

http://en.wikipedia.org/wiki/World_War_I

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http://en.wikipedia.org/wiki/Gyroscopic_precession

http://en.wikipedia.org/wiki/Electric_motor



http://en.wikipedia.org/wiki/File:Le_Rhone_9C.jpg


http://en.wikipedia.org/wiki/Radial_engine

http://en.wikipedia.org/wiki/Crankshaft

http://en.wikipedia.org/wiki/Cylinder_block

http://en.wikipedia.org/wiki/Motorcycle

http://en.wikipedia.org/wiki/Automobile

http://en.wikipedia.org/wiki/Straight_engine

http://en.wikipedia.org/wiki/V_engine

http://en.wikipedia.org/wiki/World_War_I

http://en.wikipedia.org/wiki/Rotary_engine#cite_note-nahum-0

http://en.wikipedia.org/wiki/Gyroscopic_precession

http://en.wikipedia.org/wiki/Electric_motor





An automobile starter motor

Auxiliary power unit

An auxiliary power unit (APU ) is a device on a vehicle that provides energy for functions

other than propulsion. They are commonly found on large aircraft, as well as some large land

vehicles.

The APU exhaust at the tail end of an Airbus A380

flange coupling

a driving coupling between rotating shafts that consists of flanges (or half couplings ) one

of which is fixed at the end of each shaft, the two flanges being bolted together with a ring of

bolts to complete the drive

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http://en.wikipedia.org/wiki/Airbus_A380



Flange

A flange is an external or internal ridge, or rim (lip), for strength, as the flange of an iron

beam such as an I-beam or a T-beam ; or for attachment to another object, as the flange on the

end of a pipe, steam cylinder, etc., or on the lens mount of a camera ; or for a flange of a rail

car or tram wheel. Thus flanged wheels are wheels with a flange on one side to keep the

wheels from running off the rails. The term "flange" is also used for a kind of tool used to

form flanges. Pipes with flanges can be assembled and disassembled easily.

Flanged railway wheel

Mechanical joint

A mechanical joint is a part of machine which are used to connect the other mechanical part

or mechanism. Mechanical joints may be temporary or permanent. Most types are designed to

be disassemble when required

Types Of Mechanical Joints

1.Knuckle Joints

2.Turnbuckle Joints

3.Pin Joints

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http://en.wikipedia.org/wiki/I-beam

http://en.wikipedia.org/wiki/T-beam

http://en.wikipedia.org/wiki/Lens_mount

http://en.wikipedia.org/wiki/Camera

http://en.wikipedia.org/wiki/Rail_car


http://en.wikipedia.org/wiki/Tram


http://en.wikipedia.org/wiki/Rail_profile

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http://en.wikipedia.org/wiki/Ridge_(disambiguation)

http://en.wikipedia.org/wiki/Rim_(wheel)

http://en.wikipedia.org/wiki/Shear_strength

http://en.wikipedia.org/wiki/Iron

http://en.wikipedia.org/wiki/Beam_(structure)

http://en.wikipedia.org/wiki/I-beam

http://en.wikipedia.org/wiki/T-beam

http://en.wikipedia.org/wiki/Lens_mount

http://en.wikipedia.org/wiki/Camera



http://en.wikipedia.org/wiki/Tram


http://en.wikipedia.org/wiki/Rail_profile

http://en.wikipedia.org/wiki/Pipe_(fluid_conveyance)

http://en.wikipedia.org/wiki/Machine



4.Cotter Joints

5.Bolted joints

6.Screw Joints

7.Welded Joints

Knuckle Joints

Knuckle joint

A knuckle joint is used to connect the two rods which are under the tensile load, when there

is requirement of small amount of flexibility or angular moment is necessary. There is always

axial or linear line of action of load.

The knuckle joint assembly consist of following major components :

1.Single eye.

2.Double eye or fork.

3.Knuckle pin.

At one end of the rod the single eye is formed and double eye is formed at the other end of

the rod.Both, single and double eye are connected by a pin inserted through eye.The pin has a

head at one end and at other end there is a taper pin or split pin. For gripping purpose the

ends of the rod are of octagonal forms.Now, when the two eyes are pulled apart, the pin holds

them together .The solid rod portion of the joint in this case is much stronger than the portion

through which the pin passes. [3]

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Application of knuckle joint in tractor

The modes of failure are :

1.Shear failure of pin (single shear).

2.Crushing of pin against rod.

3.Tensile failure of flat end bar.

Application :

1.Tie rod joint of roof truss.

2.Tension link in bridge structure.

3.Link of roller chain.

4.Tie rod joint of jib crane.

5.The knuckle joint is also used in tractor.

COTTER JOINT

cotter joint is used to connect the two member which are subjected to the various stress.[1]

The end of the bar has a hole in it and it is called a lug. The hole carries a shaft. This shaft is

locked in place by a smaller pin that passes through the side of the lug and partly or

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completely through the shaft itself. This locking pin is named a cotter, which sometimes is

also applied to the whole joint.so this joint is called as a cotter joint.[2]. A cotter joints is a

flat wedge link piece of steel of rectangular cross section which is inserted through the rods at

high angle to their axes .It is uniform in thickness but tapering in width , generally on one

side only. Usually the taper is 1 in 30. when a special arrangement like a set-screw is

provided for keeping the cotter from slackening ,its taper may be as large as 1 in 7. the end of

the cotter are made narrow to facilitate the hammering for fixing and removing.cotter joins

are generally use to fasten rigidly two rod s which is subjected to tensile or compressive

stress along their axes. this joint is used to connect two circular rods.This joint in not suitable

where the member are subjected under rotation.Thus they differ from key joints which are

used to fasten shaft and hubs subjected to tensional stress.[3]

APPLICATIONS OF COTTER :

1.Connection of the piston rod with the cross heads 2.Joining of tail rod with piston rod of a

wet air pump 3.Foundation bolt 4.Connecting two halves of fly wheel (cotter and dowel

arrangement) COMPARISON BETWEEN KEY AND COTTER

1.Key is usually driven parallel to the axis of the shaft which is subjected to torsional or

twisting stress. Whereas cotter is normally driven at right angles to the axis of the connected

part which is subjected to tensile or compressive stress along its axis. 2.A key resists shear

over a longitudinal section whereas a cotter resist shear over two transverse section.

DIFFERENT TYPES OF COTTER JOINTS

1.Socket and spigot cotter joint 2.Sleeve and cotter joint 3.Gib and cotter joint

Go/no go gauge

A Go-NoGo gauge (or Go/no go ) refers to an inspection tool used to check a workpiece

against its allowed tolerances . Its name derives from its use: the gauge has two tests; the

check involves the workpiece having to pass one test ( Go) and fail the other ( No Go ).

It is an integral part of the quality process that is used in the manufacturing industry to ensure

interchangeability of parts between processes, or even between different manufacturers.

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A Go NoGo gauge is a measuring tool that does not return a size in the conventional sense,

but instead returns a state . The state is either acceptable (the part is within tolerance and may

be used) or it is unacceptable (and must be rejected).

They are well suited for use in the production area of the factory as they require little skill or

interpretation to use effectively and have few, if any, moving parts to be damaged in the often

hostile production environm

Plug gauge

Hardened and ground plug gauge

Replaceable thread and plug gauges

These gauges are referred to as plug gauges; they are used in the manner of a plug . They are

generally assembled from standard parts where the gauge portion is interchangeable with

other gauge pieces (obtained from a set of pin type gauge blocks ) and a body that uses the

collet principle to hold the gauges firmly. To use this style of gauge, one end is inserted into

the part first and depending on the result of that test, the other end is tried.

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A set of pin type gauge blocks from 1.550 - 6.725 mm

In the right hand image, the top gauge is a thread gauge that is screwed into the part to be

tested, the labeled GO end will enter into the part fully, the NOT GO end should not. The

lower image is a plain plug gauge used to check the size of a hole, the green end is the GO ,

red is the NO GO . The tolerance of the part this gauge checks is 0.30mm where the lower size

of the hole is 12.60mm and the upper size is 12.90mm, every size outside this range is out of

tolerance . This may be initially expressed on the parts drawing in a number of styles, three

possibilities may be:

• 12.75mm +/- 0.15mm

•

12.60mm +0.30 -0.00• 12.90mm +0.00 -0.30

GAUGE

In engineering , a gauge or gage , is used to make measurements. A wide variety of tools exist

which serve such funtions, ranging from simple pieces of material against which sizes can be

measured to complex pieces of machinery. Various types of gauges include:

• A bore gauge , a device used for

measuring holes.

• A caliper , a device used to measure the

distance between two opposing sides of an

object.

• Center gauges and fishtail gauges are

engineering gauges used in lathe work for

checking the angles when grinding the

• A micrometer , sometimes known as a

"micrometer screw gauge", is a device

incorporating a calibrated screw used

widely for precise measurement of small

distances in mechanical engineering and

machining as well as most mechanical

trades, along with other metrological

instruments such as dial , vernier , and

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http://en.wikipedia.org/wiki/Lathe_(metal)

http://en.wikipedia.org/wiki/Micrometer

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http://en.wikipedia.org/wiki/Machining

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http://en.wikipedia.org/wiki/Caliper#Dial_caliper

http://en.wikipedia.org/wiki/Caliper#Vernier_caliper



profiles of single-point screw-cutting tool

bits and centers .

• A dial indicator , also known as a dial

test indicator, dial gauge, or probe

indicator, is an instrument used to

accurately measure small linear distances.

• A feeler gauge is a simple tool used to

measure gap widths.

• A gauge block , (also known as a gage

block, Johansson gauge, slip gauge, or Jo

block) is a precision ground and lapped

length measuring standard. It is used as a

reference for the setting of measuring

equipment used in machine shops, such as

micrometers, sine bars , calipers , and dial

indicators (when used in an inspection

role ).

• A gauge pin is similar to a gauge

block. It is a precision ground cylindrical

bar for use in Go/no go gauges or similar

applications.

• A Go/no go gauge is an inspection tool

used to check a workpiece against its

allowed tolerances. Its name derives from

its use: the gauge has two tests; the check

involves the workpiece having to pass one

test ( Go ) and fail the other ( No Go ).

• A load cell is a transducer that is used

to convert a force into electrical signal .

This conversion is indirect and happens in

two stages. Through a mechanical

arrangement, the force being sensed

deforms a strain gauge. The strain gaugeconverts the deformation ( strain ) to

digital calipers . Micrometers are often, but

not always, in the form of calipers .

• A pressure gauge or vacuum gauge is

used for pressure measurement .

• A profile gauge or contour gauge is a

tool for recording the cross-sectional

shape of a surface.

• A radius gauge , also known as a fillet

gauge, is a tool used to measure the radius

of an object. Radius gauges require a

bright light behind the object to be

measured. The gauge is placed against the

edge to be checked and any light leakage

between the blade and edge indicates a

mismatch that requires correction.

• A ring gauge is a cylindrical ring of

steel whose inside diameter is finished to

gauge tolerance and is used for checking

the external diameter of a cylindrical

object.

• Strain gauge is a device used to

measure the strain of an object.

• A stream gauge is a site along a stream

where measurements of water surface

elevation ("stage") and/or volumetric

discharge (flow) are made.• A thermometer or temperature gauge

is a device that measures temperature or

temperature gradient using a variety of

different principles.

• A thread pitch gauge , also called a

threading gauge, pitch gauge, or screw

gauge, is used to measure the pitch or leadof screw threads.

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http://en.wikipedia.org/wiki/Sine_bar

http://en.wikipedia.org/wiki/Calipers

http://en.wikipedia.org/wiki/Dial_gauge


http://en.wikipedia.org/wiki/Quality_control


http://en.wikipedia.org/wiki/Gauge_pin

http://en.wikipedia.org/wiki/Go/no_go_gauge


http://en.wikipedia.org/wiki/Load_cell

http://en.wikipedia.org/wiki/Transducer

http://en.wikipedia.org/wiki/Force

http://en.wikipedia.org/wiki/Electrical_signal

http://en.wikipedia.org/wiki/Strain_gauge

http://en.wikipedia.org/wiki/Strain_(materials_science)

http://en.wikipedia.org/wiki/Caliper#Digital_caliper


http://en.wikipedia.org/wiki/Pressure_measurement

http://en.wikipedia.org/wiki/Profile_gauge

http://en.wikipedia.org/wiki/Radius_gauge

http://en.wikipedia.org/wiki/Ring_gauge

http://en.wikipedia.org/wiki/Diameter

http://en.wikipedia.org/wiki/Engineering_tolerance


http://en.wikipedia.org/wiki/Deformation_(mechanics)#Strain

http://en.wikipedia.org/wiki/Stream_gauge

http://en.wikipedia.org/wiki/Thermometer

http://en.wikipedia.org/wiki/Temperature_gauge

http://en.wikipedia.org/wiki/Temperature

http://en.wikipedia.org/wiki/Temperature_gradient

http://en.wikipedia.org/wiki/Thread_pitch_gauge

http://en.wikipedia.org/wiki/Screw_thread#Thread_cutting



http://en.wikipedia.org/wiki/Lathe_center

http://en.wikipedia.org/wiki/Dial_indicator

http://en.wikipedia.org/wiki/Feeler_gauge

http://en.wikipedia.org/wiki/Gauge_block

http://en.wikipedia.org/wiki/Lapping

http://en.wikipedia.org/wiki/Machine_shop

http://en.wikipedia.org/wiki/Micrometer_(device)

http://en.wikipedia.org/wiki/Sine_bar

http://en.wikipedia.org/wiki/Calipers





http://en.wikipedia.org/wiki/Gauge_pin



http://en.wikipedia.org/wiki/Load_cell

http://en.wikipedia.org/wiki/Transducer

http://en.wikipedia.org/wiki/Force

http://en.wikipedia.org/wiki/Electrical_signal


http://en.wikipedia.org/wiki/Strain_(materials_science)

http://en.wikipedia.org/wiki/Caliper#Digital_caliper


http://en.wikipedia.org/wiki/Pressure_measurement

http://en.wikipedia.org/wiki/Profile_gauge

http://en.wikipedia.org/wiki/Radius_gauge

http://en.wikipedia.org/wiki/Ring_gauge

http://en.wikipedia.org/wiki/Diameter

http://en.wikipedia.org/wiki/Engineering_tolerance


http://en.wikipedia.org/wiki/Deformation_(mechanics)#Strain

http://en.wikipedia.org/wiki/Stream_gauge

http://en.wikipedia.org/wiki/Thermometer

http://en.wikipedia.org/wiki/Temperature_gauge

http://en.wikipedia.org/wiki/Temperature

http://en.wikipedia.org/wiki/Temperature_gradient

http://en.wikipedia.org/wiki/Thread_pitch_gauge



electrical signals. A load cell usually

consists of four strain gauges in a

Wheatstone bridge configuration. Load

cells of one strain gauge (quarter bridge)

or two strain gauges (half bridge) are also

available. The electrical signal output is

typically in the order of a few millivolts

and requires amplification by an

instrumentation amplifier before it can be

used. The output of the transducer is

plugged into an algorithm to calculate the

force applied to the transducer.

• The linear variable differential

transformer (LVDT) is a type of electrical

transformer used for measuring linear

displacement. The transformer has three

solenoidal coils placed end-to-end around

a tube. The center coil is the primary, andthe two outer coils are the secondaries. A

cylindrical ferromagnetic core, attached to

the object whose position is to be

measured, slides along the axis of the tube.

• A tide gauge is a device for measuring

sea level and detecting tsunamis .

• Vernier height gauge is a measuring

device used either for determining the

height of something, or for repetitious

marking of items to be worked on. The

former type of height gauge is often used

in doctor's surgeries to find the height of

people.

• A wire gauge measuring tool

determines the thickness of a wire .

(Master Gauge) A thread-plug gauge which represents the physical dimensions of the

nominal or basic size of the part. It clearly establishes the minimum size of the threaded hole

and the maximum size of the screw at the point at which interference between mating parts

begin.

accumulated error The collected inaccuracy in measurement that can

occur when multiple elements are combined.

accuracy The difference between a measurement reading and

the true value of that measurement.

air gage A variable, non-contact pneumatic instrument that

uses pressurized air to inspect the ID of holes.air regulator The part of a pneumatic inspection system by which

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pressurized air is controlled.

backflow pressure Movement of pressurized air in the direction

opposite to which it was pushed out of the device. In

an air gage, backflow pressure is caused byresistance from the sides of the hole.

bore gage A hole inspection gage that makes three points of

contact within the hole. Bore gages are handheld,

mechanical or electronic contact instruments with

variable measuring systems.

borescope A non-contact optical inspection device consisting of

a rigid or flexible tube with an eyepiece at one endand a magnifying lens at the other. Borescopes

provide a view of hole interiors that are otherwise

difficult or impossible to see.

caliper A handheld, variable contact instrument that

functions as a precision slide ruler. The indicators on

the top of the instrument expand to measure internal

diameters.capable A gage's predictable range of ability, even when

under the influence of natural variation due to

common causes.

comparison device A measuring instrument that adjusts to assume the

size of a feature.

concavity A curved surface condition like the inside of a ball.

contact instrument A measuring device that actually touches the part inorder to obtain its measured value.

contact probe The main measuring member on a coordinate

measuring machine that communicates its position

on a workpiece to the CMMs control panel or

computer. A probe often has a sphere of ruby at its

tip.

continuous scanning An inspection method used by a coordinatemeasuring machine in which the probe slides along

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the surface of the workpiece to collect seamless data

in the form of a series of numerous points.

coordinate measuring machine A sophisticated electronic measuring instrument

with a flat polished table that inspects parts in three-dimensional space using either a contact or a non-

contact probe. All CMMs are variable devices.

dial indicator A measuring instrument with a contact point

attached to a spindle and gears that move a pointer

on the dial. Dial indicators have graduations that

allow you to read different measurement values.

digital readout An indicator on a measuring device that presentsdata through a numerical display.

electronic instruments Inspection devices that use electrical impulses to

report either position changes or contact between the

inspection device and the part.

extension A piece that is added to the head of an inside

micrometer to expand it to the width of the hole.

eyepiece The part of a boroscope through which the inspectorviews the interior of the workpiece.

flowmeter tube A cylindrical indicating device on a pneumatic

measuring instrument that looks similar to a

thermometer.

gaging instrument An inspection device of a standard size that

determines fit but does not determine actual

measurement value.go-no go gage An instrument that determines whether a part

feature simply passes or fails inspection. No effort is

made to determine the exact degree of error.

indicator A device, often numerical, that displays a

measurement. An indicator may be a dial with a

needle or a digital readout.

inner diameter ID. The interior surface of a hole in a workpiece.

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inside micrometer A mechanical or electronic, variable, handheld

contact instrument, usually cylindrically shaped,

used to measure the inside diameter of larger holes.

laser system A non-contact, variable, optical inspection methodthat uses light to examine the inside diameter of

holes. Laser systems send out a single light wave on a

straight line that is detected by sensors and

converted into an electrical signal.

light wave A form of visible energy used by lasers.

linear scale A series of parallel lines that represent a

measurement standard. A ruler contains a linearscale.

linearity The amount of error change throughout an

instrument's measurement range. Linearity is also

the amount of deviation from an instrument's ideal

straight-line performance.

lobing A condition in which the manufacturing process

creates a rounded projection out from what wouldotherwise be a circular hole. A hole may have more

than one lobe.

master gage A measuring device of a standard size that is used to

calibrate other measuring instruments.

mechanical device A measuring instrument that must be physically

manipulated by the inspector. Mechanical devices

may be go-no go or variable.micrometer head The main component of an inside micrometer that

includes the scale and indicating device. Extensions

are added to the micrometer head.

non-contact instrument A measuring device that is able to obtain the

measured value of the part without making physical

contact. An air gage is an example of a non-contact

instrument.

optical comparator A sophisticated measuring instrument that projects

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an image of a part onto a screen to compare the

shape, size, and location of its features. Optical

comparators are non-contact, variable, optical

inspection devices.optical instruments Inspection devices that use light and lenses to inspect

parts. The part may be viewed directly through the

lense or displayed on a screen.

outside micrometer A handheld device consisting of an anvil, a shaft, and

an indicator that is used to measure outside

diameters.

ovality A condition in which a hole that should be round hastwo opposing lobes, resulting in an egg shape.

pin gage A cylindrically shaped length of metal of a specific

diameter used as a gaging inspection device. A pin

gage is a handheld mechanical contact instrument.

plug gage A hardened, cylindrical gage used as a handheld

mechanical contact instrument to inspect the size of

a hole. Plug gages are available in standarddiameters and are often two-sided, with a "go" side

and a "no go" side.

pneumatic instrument A measuring device that uses a pressurized gas, such

as air, to function.

precision The degree to which an instrument will repeat the

same measurement over a period of time.

probe cable The portion of a laser system that transmitsinformation and power to and from the tip of the

device and the computer.

ring gage A circular measuring device of a standard size that is

used to calibrate other instruments or inspect

cylindrical parts.

rotary laser An inspection device that projects a light wave on

the surface of the part's internal diameter as it turns.scale A standard of measurement that is often displayed as

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a series of lines.

setting gage A measuring device of a standard size that is used to

check or prepare a working gage for use. Bore gages

often come with matching setting ring gages.split-ball gage A cylindrical device with an expanding, flat-ended

ball on one end and a locking device on the other. A

split-ball gage is a handheld, mechanical contact

instrument that is used for comparison

measurement. It is also called a small-hole gage.

taper A gradual narrowing of an inside or outside surface.

telescoping gage A T-shaped measuring device that has two spring-loaded measuring arms and a lock in the base. A

telescoping gage is a handheld, mechanical contact

instrument used for comparison measurement.

thimble A ring or cylinder that fits around the spindle of a

micrometer. To advance the spindle, you turn the

thimble.

tolerance The acceptable variation from a specified dimension.tolerance range The expected range of measurements produced by a

given operation. It is also known as a tolerance zone.

variable instrument An inspection device calibrated in standard

measurement units. Variable inspection reveals the

degree of variation from a given standard.

video borescope A borescope that contains a video camera rather

than an eyepiece.working gage A measuring device of a standard size that is used to

inspect parts.

Reaming:

Reaming is a process which slightly enlarges a pre-existing hole to a tightly toleranced

diameter. A reamer is similar to a mill bit in that it has several cutting edges arranged around a

central shaft, as shown below. Because of the delicate nature of the operation and since little

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material is removed, reaming can be done by hand. Reaming is most accurate for axially

symmetric parts produced and reamed on a lathe.

Counter Bore/Sink

• Counter-sinking is often done to accommodate heads of flat head screws. However as

can be seen from the figure, there is a sideways component of the thrust which couldsplit the countersink due to the generated hoop stresses

• Counter-boring is done to accomodate pan-head, fillister-head or round-head screws or

other screws with flat-bottomed undersides.

Drilling , tapping , counterboring , and countersinking are the usual operations done in sheet

metals.

Drilling : Drilling is done in sheet metal only when piercing cannot deliver the accuracy

required. For example, on a formed part, when holes on different features need to be coaxial,

the accuracy obtained by machining may be required.

Tapping : Tapping can be done using cut threads or formed threads. Formed threads (thread

rolling) is preferable for the following reasons:

• Thread rolling is faster than cutting.

• Fewer burrs are generated, so no clean up is required or risk of future hazards such as

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shorting with electronic components.

• Larger sized holes are required for thread rolling vs. tapping, resulting in improved tap

life.

• Rolled threads are stronger due to cold working. Typically, rolled threads are 20%

stronger than cut threads.

• For very thin stock, either threaded fasteners such as clinch nuts, or forming thread in

extruded holes is recommended.

OR

• The material is upset in the sheet metal hole to form one thread pitch.

Counterboring : Counterboring is often done to provide clearance and a bearing surface for the

fastener's head.

Countersinking : Countersinking allows for flush mounting of flat head fasteners.

Countersinking cannot always be done for very thin stock or for very large fasteners.

Introduction to Injection Molding

Injection molding is considered one of the most common plastic part manufacturing

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processes. It can be used for producing parts from both thermoplastic and thermoset polymers.

The process usually begins with taking the polymers in the form of pellets or granules and

heating them to the molten state. The melt is then injected/forced into a chamber formed by a

split-die mold. The melt remains in the mold and is either chilled down to solidify

(thermoplastics) or heated up to cure (thermosets). The mold is then opened and the part is

ejected.

A Typical Injection Molding Process

In spite of the relatively expensive tooling cost, injection molding remains the most popular manufacturing process for plastic materials in mass production, thanks to its low operational

cost, high throughput, and the flexibility to make parts with complex shapes.

Polymers commonly used for injection molding include

Polystyrene (PS)

Acrylonitrile Butadiene Styrene (ABS)

Polyamide (PA)Polypropylene (PP)

Polyethylene (PE)

Polyvinylchloride (PVC)

Other short fiber reinforced plastics

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• Counter-bored screws exert only force in the axial direction, thus operate mostly under

compression, with no sideward component to the applied force vector. Such design is

inherently more robust than counter-sinking.Metal Inert Gas (MIG) Welding : An arc is struck between a consumable electrode and the

sheet metal to be welded. The consumable electrode is in the form of continuous filler metal.

An inert gas surrounds the arc and shields it from the ambient to prevent oxidation.

Carbon steels, low alloy steels, stainless steels, most aluminum alloys, zinc based copper alloys

can be welded using this process.

Tungsten Inert Gas (TIG) Welding : An arc is truck between a tungsten electrode (non-

consumable) and the sheet metal to be welded. An inert gas shields the arc from the ambient to

prevent oxidation. A filler material is optional

102



Carbon steels, low alloy steels, stainless steels, most aluminum alloys, zinc based copper alloys

can be welded using this process. TIG is quite suitable for welding dissimilar materials, but

usual cautions of galvanic corrosion still apply.

The TIG process is a slower process compared to the MIG process, but the quality of weld is

cosmetically better. There is no weld spatter, and the quality of welds is higher than MIG

welding.

Oxy Acetylene Gas Welding : Acetylene or some combustible gas is combined with Oxygen

and the flame heats the sheet metal to be welded. A filler metal rod supplies the molten metal

for the joint.

This method is readily available, but the heat can cause distortion in sheet metal. Due to this,

this method is being displaced by other methods such as MIG and TIG welding.

Types of Weld Joints

• Butt, T, corner, lap, and T joints are the common types of joints used in sheet metal

welding. These can all be used with MIG and TIG welding.

• Corner joints are used frequently in sheet metal cabinet construction.

103



• Types of welds are often confused with the types of joints. The basic types of welds are

fillet, square, and grooved.

Stress-Based Criteria

The purpose of failure criteria is to predict or estimate the failure/yield of machine parts and

structural members.

A considerable number of theories have been proposed. However, only the most common and

well-tested theories applicable to isotropic materials are discussed here. These theories,

dependent on the nature of the material in question (i.e. brittle or ductile), are listed in the

following table:

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Material

TypeFailure Theories

Ductile Maximum shear stress criterion , von Mises criterion

Brittle Maximum normal stress criterion , Mohr's theory

All four criteria are presented in terms of principal stresses. Therefore, all stresses should be

transformed to the principal stresses before applying these failure criteria.

ball indenter A spherical indenter used in the Brinell test and certain

Rockwell tests. Ball indenters are made from hardened steelor tungsten carbide and must be checked periodically for

wear.

brale A conical diamond indenter used in Rockwell hardness tests.

Brinell hardness test A hardness test that measures the diameter of a circle formed

by the penetration of a 10 mm steel ball under a fixed load

pressure.

case hardened Heated within a carbon-rich environment to increase carbonlevels on the metal surface. Case hardening creates a hardened

exterior shell.

casting A workpiece formed by pouring molten metal into a mold and

cooling it into a solid shape. Castings are formed near their

finished shape.

cemented carbide A compound developed by the combination of carbon with

tungsten, titanium, or tantalum. It is used in metal cuttingtools for its hardness and wear resistance.

cold working The shaping of metal at temperatures much lower than the

metal's molten state, often at room temperature. Cold working

adds certain properties to the metal, such as increased strength

and improved surface finish.

diamond pyramid

hardness test

A hardness test that forces a pyramid-shaped diamond against

a material for a standard dwell time to create an indentation.

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The size of the indentation determines the hardness value.

Also known as the Vickers hardness test.

durometer The testing instrument of the Shore hardness test. The

durometer is used to test elastic materials.durometer hardness The hardness value determined by a durometer during a Shore

hardness test.

dwell time An intentional time delay during which an indenter is held

against a material under load during a hardness test. Dwell

time is used to ensure accurate hardness ratings.

elastic modulus The relative force required to elongate a material. The

International Rubber Hardness Degrees Test indicates theelastic modulus of test materials.

elastic penetration Metal penetration that is temporary. If a material is penetrated

beyond its elasticity, the material experiences plastic

penetration.

elastic recovery A period of slight rebound in a material after a load has been

removed.

forging A workpiece that has been made by forming bulk solid metalinto a specific shape at elevated temperatures.

hardness The ability of a material to resist scratching, abrasion,

indentation, or cutting. Hardness is generally measured by the

depth or area of penetration under a fixed load using a

diamond indenter.

hardness testing Standardized experiments designed to determine how a

material responds to external forces that attempt to scratch, penetrate, or indent the material.

hardness value A number from a hardness testing scale that indicates the

ability of a material to resist scratching and penetration.

heat treatment The controlled heating and cooling processes used to change

the structure of a material and alter its physical and

mechanical properties. Heat treating is often used to adjust a

material's hardness.

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indentation test A type of hardness test in which a hardened indenter is forced

against a material under a fixed load. The size of the

indentation indicates the hardness of the material.

indenter A device used in a hardness test that is pressed into the testmaterial.

indicator A device that displays a measurement. An indicator may be a

dial with a needle or a digital readout.

international rubber

hardness degrees test

A hardness test that uses minor and major loads to measure

the elastic modulus of rubber test materials.

Knoop hardness test A microhardness test that uses a small pyramid-shaped

diamond indenter and relatively light loads between 10 g and1 kilogram. The Knoop indenter has a long diagonal that is

perpendicular to and 7 times the length of the short diagonal.

Leeb test A portable hardness test that measures the rebound of a

hammer mechanism. Unlike the scleroscope, the Leeb test can

be administered from any angle regardless of gravity.

load The overall force applied to an object by external objects.

macrohardness test The hardness testing of normal-sized materials with standardloads, indenters, and dwells.

major load The second and largest static load delivered during a hardness

test.

mechanical properties The properties that describe the way a material responds to

forces that attempt to bend, break, twist, dent, or scratch it.

microhardness testing Hardness testing that involves very small or brittle test

materials and very light loads. Also known asmicroindentation testing.

microindentation testing Hardness testing that involves very small or brittle test

materials and very light loads. Also known as microhardness

testing.

microstructure The shape and alignment of the microscopic components of a

metal. A material's microstructure often determines its

hardness, toughness, and other properties.

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minor load The first and smallest static load delivered during a hardness

test.

nonferrous material A metal that does not contain iron as a main ingredient.

Common nonferrous metals include aluminum, titanium,copper, and nickel.

ocular scale A scale built into a microscope that makes it possible to view

magnified images and measure very small features.

physical properties The way that a material reacts to forces other than mechanical

forces. Melting, freezing, thermal conductivity, and electrical

conductivity are all physical properties.

plastic penetration Metal penetration that is permanent. During hardness testing, plastic penetration is measured to determine hardness.

polishing An abrasive finishing process used to improve the surface of a

part.

properties The characteristics of a material that distinguish it from other

materials.

Rockwell hardness test A hardness test that measures the degree of penetration into a

metal caused by a diamond or ball indenter that is appliedunder a fixed load.

scale A hardness testing measurement standard based on several

factors including the indenter, the type of material being

tested, and the size of the test loads.

scleroscope A hardness test that measures the rebound of a hammer

dropped from a fixed height. The higher the rebound, the

higher the hardness.Shore hardness test A hardness test designed for elastic materials such as rubbers.

The Shore tester is called a durometer.

static load An external force that is applied and held in a fixed position

for a specific amount of time. Static loads are an important

component of standardized hardness tests.

Superficial Rockwell

hardness test

A Rockwell test designed for thin test materials. The

Superifical Rockwell test is identical to the Rockwell test,

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except the minor load is 3 kg and the major load is either 15,

30, or 45 kilograms.

tungsten carbide The original carbide tool material that offers excellent

hardness and wear resistance.ultrasonic

microhardness test

A microhardness test that vibrates a Vickers diamond against

a workpiece under a specific load. The change in frequency

determines the material's hardness value.

Vickers hardness test A hardness test that forces a pyramid-shaped diamond against

a material for a standard dwell time to create an indentation.

The size of the indentation determines the hardness value.

Also known as the diamond pyramid hardness test.

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Concepts in Engineering

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