1 Material Workshop

8/18/2019 1 Material Workshop

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Science

• Science (Latin scientia , meaning "knowledge) is asystematic enterprise that builds andorganizes knowledge in the form of testable explanations and predictions aboutthe universe.


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Art• Art is the product or process of deliberatelyarranging items (often with symbolic

significance) in a way that influences andaffects one or more of the senses, emotions,

and intellect.• It encompasses a diverse range of human

activities, creations, and modes of expressions,including music, literature, film,photography, sculpture, and paintings.


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Engineering

• Engineering is the discipline, art, skill andprofession of acquiring andapplying scientific, mathematical, economic, social,and practical knowledge , in order to design and buildstructures, machines, devices, systems, materialsand processes .


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Mechanical Engineering

• It is the branch of engineering that involves theproduction and usage of heat and mechanicalpower for the design, production, and

operation of machines and tools .• It uses the principles of physics and materialsscience for analysis, design, manufacturing,and maintenance of mechanical systems.


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Mechatronics

• Mechatronics is an area of engineering thatcombines mechanical and electrical/electronicsengineering and computer science.

• A typical mechatronic system picks up signalsfrom the environment, processes them togenerate output signals, transforming them forexample into forces, motions and actions.


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Mechatronics

It is the extension and the completion of mechanical systemswith sensors and microcomputers which is the most importantaspect.

The system picks up changes in its environment by sensors, and

reacts to their signals using the appropriate informationprocessing, makes it different from conventional machines.

Examples :Mechatronic systems are robots, digitally controlledcombustion engines, machine tools with self-adaptive tools,contact-free magnetic bearings, automated guided vehicles, etc


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Workshop Technology• Workshop technology deals with different

processes by which component of a machine orequipments are made.


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Workshop• A workshop may be a room or building which provides

both the area and tools (or machinery) that may berequired for the manufacture or repairof manufactured goods. Apart from the larger factories,workshops were the only places of production in thedays before industrialization.


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ContentsSl.No Unit Contents

1.Unit 1: Engineering Materials, its classification ,their Properties &

Heat Treatment.

2Unit 2 Hot and Cold working:

Forging Shop

3Unit 3 Foundry Shop – Pattern making, mould making, Furnaces,

Ladles & Special Castings

4Unit 4 Welding Shop – Fusion welding, pressure welding, Energy

beam welding & Solid state welding, Equipments and tools.

5Unit 5 Fitting Shop – Tools , Measuring Instruments, Drills, Threads,

Bolts, screws nuts, Rivets

6Unit 6 Sheet metal Shop – Tools, equipments, Forming processes,

Pattern developments.

7Unit 7 Carpentry Shop – Wood & their defects, seasoning, joints,

Plywood,Tools and Machines used.

8Unit 8 Machine shop- Lathe machine components, accessories,

Turning operations, taper turning.


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Unit 1Engineering Materials


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MATERIALS


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MATERIALS

WITHOUT MATERIAL, THERE IS NOENGINEERING.


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MATERIAL CLASSIFICATION

Material

Metal

Ferous

Steel

PlainCarbon

Steel

LowCarbon

Sttel

MediumCarbon

Steel

HighCarbon

Steel

Alloy Sttel

StainlessSteel

Cast Iron

Grey White Ductile Malleable

Non Ferous

Ceramics Polymers


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Non-Ferrous Metals

• Copper - Soft, easy to form, good conductor• Aluminum - Soft, easy to form, good

conductor


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High Temperature Alloys

• Iron Based• Nickel Based - Hastelloy

• Cobalt Based - Thermospan


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Ferrous Metals: Applications

• Structural: building structures, concretereinforcement

• Automotive: chassis, engine parts, drive train,body parts

• Marine: ship hulls, structure, engines

• Defense: tanks, weapons• Consumer Products: appliances, recreational

vehicles, toys, utensils and tools


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Nonferrous Metals: Applications

• Architectural: aluminum windows anddoors

• Automotive: aluminum engine blocks,copper wiring, mag wheels

• Marine: brass/bronze fittings, bearings,propellers

• Defense: brass shell casings

• Consumer Products: electrical wiring,utensils, jewelry, electronics


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Properties of Materials

Mechanical Properties : strength, toughness(the waymaterial reacts under sudden impact), ductility,hardness, elasticity, fatigue(failure under cyclic loading),creep (time dependent failure).

Behavior Under Loading : tension, compression,bending, torsion, shear.

Physical Properties : density, specific heat, thermalexpansion, thermal conductivity, melting point, electricaland magnetic properties.

Chemical Properties : oxidation, corrosion,degradation, toxicity, flammability.


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General Stress Strain Diagram

stress

strain

1. True elastic limit2. Proportionality Limit3. Elastic limit4. Off set Yield Point


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Stress Strain Relationship


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Stress Strain Diagram for Ductile Material

stress

strain


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Stress Strain Diagram for brittle Material

stress

strain


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P :Proportionality LimitE:Elastic limit

Yu: Upper Yield PointY l :Lower Yield PointS:Ultimate StrengthB:Breaking Point


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Mechanical Properties

• Hardness(resistence to indentation) tests -Rockwell, Brinell

• Toughness - Charpy impact• Tensile(ability to sustained the tensile load)

strength• Ductility

• Elasticity (The property of returning to aninitial form or state after removal ofexternal force)


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Mechanical Properties

• Plastic deformation - Doesn’t return tooriginal shape.

• Ductility - Elongation less than 5% isbrittle, More than 5% is Ductile.


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Plastics (Polymers)

• Compared to metals, plastics have lowerdensity, strength, elastic modulus, and thermaland electrical conductivity, and a higher

coefficient of thermal expansion

• The design of plastic parts should includeconsiderations of their low strength andstiffness, and high thermal expansion and lowresistance to temperature.


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Plastics: Applications

• Architectural: electrical and thermal insulation,weather seals, carpets, wall coverings, paint .

• Aerospace: electrical and thermal insulation,instrument panels, seals .

• Automotive: body panels, instrument panels,electrical and thermal insulation, seals, hoses, tires .

• Consumer Products: toys, sporting goods,appliances, tools, utensils, clothing, shoes, packaging.


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Manufacturing a Product:General Considerations

• Material Selection

• Processing Methods

• Final Shape and Appearance• Dimensional and Surface Finish

• Economics of Tooling

• Design Requirements• Safety and Environmental Concerns


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HEAT TREATMENT


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HEAT TREATMENT PROCESS

Water

Oil Air

InFurna

ce

Quenching Normalizing Annealing

T e m p e r a t u r e

C

Time

Temp x Time

Atmosphere

Carburizing, Decarburizing

Deoxidation, oxidation

Cooling


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Effect of Cooling rate on Structure


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Annealing Process• To soften a metal• Grain refinement for improving mechanical

properties• Relieving internal stresses after hot and cold

work • To modify other mechanical and physical

properties

• To remove gases trapped in the metal duringinitial casting


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Normalizing (Air Quenching)• Heating the steel 30-50 degree C above its

upper critical temperature (for hypo-eutectoidsteel) or Acm line. It is held at this temperaturefor about fifteen minutes and then to cooldown in still air/even in furnace

• To refine the grain structure of steel to improvemachinability, tensile strength

• To remove strain cause by hot and coldworking

Diff b t A li g d


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Difference between Annealing andNormalising

• Annealing (softening): to attain bettermachinability, softening and greater removal ofinternal stresses

• Normalising: to improve mechanical properties• Normalising is carried out at relatively higher

temperature than annealing process


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Hardening Process• Surface or case hardening process• Carburizing : Carbon is used to increase

surface strength• Cyaniding: Cyanide is used • Flamed: Flame is used • Nitriding: Nitrogen gas is used

• Similar other effects


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Effect of Alloying Elements

• Tungsten: High temperature, wearresistance.

• Chromium: Increases wear resistance,corrosion resistance and toughness.

• Vanadium: increase the toughness andstrength of the steel

• High speed steel or tool steel : 18%Tungsten+4% Chromium+1% Vanadium in0.7% carbon


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• Nickel: increases toughness and hardenability• Vanadium: To increase hardenability• Cobalt: Improves strength at high temperatures

and magnetic permeability.• Titanium: In conjunction with Boron, increases

the effectiveness of the Boron in thehardenability of steel.

• Molybdenum: Increases the hardness penetration of steel and high temperaturetensile strength.



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• Silicon: added in steel 0.05-0.3% to prevent porosity.• Sulphur: Improves machinability.

• Manganese: To remove undesirous ironsulphide• Phosphorus: Phosphorus, in small amounts,

aids strength and corrosion resistance



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Homework

• Why are alloys so popular?

• Because the addition of alloy provides themechanical properties needed for strength,corrosion resistance and ductility.


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Homework

• Discuss the concept of plasticity in terms ofa material’s ability to withstand changes inits shape when being formed under

pressure.

• A material that can be formed underpressure (forged) must have Plasticity. Forexample Aluminum can be formed underpressure but cast iron can’t.


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Homework

• How do Plasticity and Ductility differ?• Plasticity is the propensity of a material to

undergo permanent deformation under load.

• Ductility is a measure of how much strain amaterial can take before rupturing. A materialwith high ductility will be able to be drawn intolong, thin wires without breaking. A material

with low ductility is instead brittle, and thoughit may be strong, once it deforms enough, itwill simply rupture


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Homework

• List some products made with Refractorymetals. How are the metals made?

• Light bulb filaments, electrodes, gasturbines, crucibles. These metals are pureelements.


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Appendix


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Strength

• Measure of the material property to resistdeformation and to maintain its shape

• It is quantified in terms of yield stress orultimate tensile strength.

• High carbon steels and metal alloys have

higher strength than pure metals.• Ceramic also exhibit high strength

characteristics.


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Hardness

• Measure of the material property to resistindentation, abrasion and wear.

• It is quantified by hardness scale such asRockwell, Vickers and Brinell hardnessscale.

• Hardness and Strength correlate wellbecause both properties are related to in-molecular bonding.


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Ductility

• Measure of the material property to deform beforefailure.

• It is quantified by reading the value of strain atthe fracture point on the stress strain curve.

• Example of ductile material : – low carbon steel – Aluminum

• It may be expressed by either


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Ductility (contd)


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Brittleness

• Measure of the material’s inability todeform before failure.

• The opposite of ductility.• Example of brittle material

– glass, – high carbon steel, – Ceramics


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T h


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Toughness

• The ability of a metal to deform plastically and to absorb energy in the process before fracture is termed toughness.

• Toughness is the area under thestress-strain curve, and is a measureof the total energy absorbed untilfailure.

• There are several variables that havea profound influence on the toughness

of a material. These variables are: – Strain rate (rate of loading) – Temperature – Notch Effect


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Toughness (contd)

• A metal may possess satisfactory toughness under static loadsbut may fail under dynamic loads or impact. – As a rule ductility and, therefore, toughness decrease as the rate of

loading increases.

• Temperature is the second variable to have a major influenceon its toughness. – As temperature is lowered, the ductility and toughness also decrease.

• The third variable is termed notch effect, this is mainly related

to the distribution of stress. – A material might display good toughness when the applied stress is

uniaxial; but when a multiaxial stress state is produced due to the presence of a notch, the material might not withstand the simultaneouselastic and plastic deformation in the various directions.


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Toughness (contd)• Impact toughness can be measured by Charpy

V-Notch Test – The potential energy of the pendulum

before and after impact can be calculatedform the initial and final location of thependulum.

– The potential energy difference is theenergy it took to break the material.absorbed during the impact.

– At low temperature, where the material isbrittle and not strong, little energy isrequired to fracture the material.

– At high temperature, where the material ismore ductile and stronger, greater energyis required to fracture the material

– The transition temperature is the boundarybetween brittle and ductile behavior.

– The transition temperature is an extremelyimportant parameter in material selection.


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Few Definitions(1/2)

• Nitriding is a heat treating processthat diffuses nitrogen into the surface of a metal tocreate a case hardened surface.

• Carburizing or carburising (British English) isa heat treatment process inwhich iron or steel absorbs carbon liberated whenthe metal is heated in the presence of a carbon

bearing material, such as charcoal or carbonmonoxide, with the intent of making the metalharder.


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Few Definitions(2/2)

• Annealing: This term is used to define a heattreatment process that produces some softening of the structure. True annealing involves heating thesteel austenite and hold for some time to create astable structure. The steel is then cooled very slowlyto room temperature. This produces very softstructure, but also creates very large grains whichare seldom desirable because of poor toughness.

• Normalizing: Return the structure back to normal.

The steel is heated until it just starts to formaustenite, it is cooled in air. This moderately rapidtransformation creates relatively fine grains withuniform pearlite


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