NEW ENGINEERING WORKS.,located in Patna,India,was established in
1990 and is specialized in Manufacturing quality spare parts for projectile
looms. We are the largest and most well-known manufacturer of Sulzer
Projectile Weaving Machines Replacement Parts for Model PU, TW-11, P-
7100,P-7200 & P-7300. Our main profile is the manufacturing and export in
spare parts for Sulzer Projectile Weaving Machines Which includes Picking
Shoes, Picking lever, Projectile Returners, R.H slide piece, and many
more.
Over 23 years of Experience in this field we can offer a product range of
Unique and Patented manufacture to give textile manufactures reliable
quality components at a cost effective price. Whether through continuous
improvement in product quality or management, our motto is
to "Continuously Strive to Be the Best."
We Have Been Adhering To The Principle Of “Continuously Strive To Be
The Best”
Our Parts Have Been Marketed to india as well as Exported To Global
Markets like South africa, Indonesia,Sri lanka, Bangladesh, Nepal, Europe,
Middel - east etc.
We have built long term, good relationship with many customers From India
and Abroad and We Get The Reputation For Our Top Quality and adhering
to promises and reasonable after sale service as well. As A Result, Our
Sales Volumes Have Steadily Risen Over The Past Several Years . Our
Parts Are Equilant to Original Parts and a real alternative to expensive
original parts.
New Engineering Works Prides Itself For Having Experienced Employees
Who Manage The Design And Manufacturing Process Of The Highest
Quality Spare Parts.
Uniqueness Of Our Company Is That We Are Manufacturing Most Critical
Parts Of Sulzer Projectile Looms. And We Are Using High Grade Materials
and Best Metal treatments To Achieve Quality Differences Among The
Other Suppliers. We Rely On Sufficient Techincal Force, Advace
Production Technology.
Our philosophy is to strive continuously for innovation and therefore the
company today can manufacture any mechanical component according to
technical details / sample.
We Are Looking Forward To Cooperating With You, It Would Be
Appreceiated To Hear From You.
Our Engineering Division was established to provide custom designed
products for industrial applications, service and maintenance of products,
and supply parts for all our products.
ASW is capable of developing ad hoc solutions to meet individual customer
requirements. Our technical experts are experienced in designing and
manufacturingtailor-made products, and proposing innovative
improvements and solutions for all applications. We work with you to
develop the optimum solution.
In addition, we will assist in the commissioning of your plant equipment,
and continue to provide top class service and support, whenever you need
it. All our projects are completed professionally, timeously, and within
budget.
Machining Workshop
Turning
Milling
Surface Grinding
Small Quantity Machining
Production Run Machining
Precision Machining
Mechanical and Electrical Workshops
We repair various types of pumps including the following:
Centrifugal Pumps
Dosing Pumps
Peristaltic Pumps
Canned Motor Pumps
Progressive Cavity Pumps
Magnetic Drive Pumps
Compressors Gearboxes
Hydrostatic Drives
We also Repair Hydraulic Equipment Including:
Cylinders
Valves
Pumps
Lubrication Equipment
Motors
Hydraulic Control Stations
Power-Packs
Our Service Department:
On Site Installations
On Site Repairs
Service Contracts
Refurbishments
Upgrades
Commissioning
Fabrication Workshop
All welding done according to API 1104
Workshop Facilities
Machine Shop floor area 300sq.m
Fitting Shop floor area 180sq.m
Stockholding floor area 260sq.m
Welding Bay 60sq.m
Fabrication Shop 260sq.m
APPLIED MECHANICS
Applied mechanics is a branch of the physical sciences and the practical
application of mechanics. Applied mechanics describes the response of
bodies (solids and fluids) or systems of bodies to external forces. Some
examples of mechanical systems include the flow of
a liquid under pressure, the fracture of a solid from an applied force, or the
vibration of an ear in response to sound. A practitioner of the discipline is
known as a mechanician.
Engineering mechanics may be defined as branch of science that
describes the behavior of a body, in either a beginning state of rest or of
motion, subjected to the action of forces.
Applied mechanics, as its name suggests, bridges the gap between
physical theory and its application to technology. As such, applied
mechanics is used in many fields of engineering, especially mechanical
engineering. In this context, it is commonly referred to as engineering
mechanics. Much of modern engineering mechanics is based on Isaac
Newton's laws of motion while the modern practice of their application can
be traced back to Stephen Timoshenko, who is said to be the father of
modern engineering mechanics.
Within the theoretical sciences, applied mechanics is useful in formulating
new ideas and theories, discovering and interpreting phenomena, and
developing experimental and computational tools. In the application of
the natural sciences, mechanics was said to be complemented
by thermodynamics, the study of heat and more generally energy,
andelectromechanics, the study of electricity and magnetism
The advances and research in Applied Mechanics has wide application in
many fields of study. Some of the specialties that put the subject into
practice are Civil Engineering, Mechanical Engineering, Construction
Engineering, Materials Science and Engineering, Aerospace
Engineering, Chemical Engineering, Electrical Engineering, Nuclear
Engineering, Structural engineering and Bioengineering Prof. S. Marichamy
said that "Mechanics is the study of bodies which are in motion or rest
condition under the action of Forces"
Major Topics of applied mechanics
Acoustics
Analytical mechanics
Computational mechanics
Contact mechanics
Continuum mechanics
Dynamics (mechanics)
Elasticity (physics)
Experimental mechanics
Fatigue (material)
Finite element method
Fluid mechanics
Fracture mechanics
Mechanics of materials
Mechanics of structures
Rotordynamics
Solid mechanics
Soil mechanics
Stress waves
Viscoelasticity
Examples of applications
Civil engineering
Mechanical Engineering
THERMAL ENGINEERING
Thermal engineering deals with the conversion of heat energy between
mediums and into other usable forms of energy. Most of the energy from
thermal sources is converted into chemical, mechanical or electrical
energy. In order to achieve this, thermal engineers are experts in heat
transfer. Some areas a thermal engineer may specialise in include solar
heating, boiler design or HVAC (heating, ventilation and air conditioning).
Common industries that employ thermal engineers include power
companies, the automotive industry and commercial construction. Travel is
usually involved to factory locations or to the site of their current projects.
Heating or cooling of processes, equipment, or enclosed environments are
within the purview of thermal engineering.
One or more of the following disciplines may be involved in solving a
particular thermal engineering problem:
Thermodynamics
Fluid mechanics
Heat transfer
Mass transfer
Thermal engineering may be practiced by mechanical
engineers and chemical engineers.
One branch of knowledge used frequently in thermal engineering is that
of thermofluids.
Application
Engineering : HVAC
Cooling of computer chips
Boiler design
Solar heating
In design of combustion engines
Thermal power plants
Thermodynamics: The branch of science that deals with the study of
different forms of energy and the quantitative relationships between them.
System: Quantity of matter or a region of space which is under
consideration in the analysis of a problem.
Surroundings: Anything outside the thermodynamic system is called the
surroundings. The system is separated from the surroundings by the
boundary. The boundary may be either fixed or moving.
Closed system: There is no mass transfer across the system boundary.
Energy transfer may be there.
Open system: There may be both matter and energy transfer across the
boundary of the system.
Isolated system: There is neither matter nor energy transfer across the
boundary of the system.
State of the system and state variable: The state of a system means the
conditions of the system. It is described in terms of certain observable
properties which are called the state variables, for example, temperature
(t), pressure (p), and volume (v).
State function: A physical quantity is a state function in the change in its
value during the process depends only upon the initial state and final state
of the system and does not depend on the path by which the change has
been brought about.
Macroscopic system and its properties: If as system contains a large
number of chemical species such as atoms, ions, and molecules, it is
called macroscopic system. Extensive properties: These properties depend
upon the quantity of matter contained in the system. Examples are; mass,
volume, heat capacity, internal energy, enthalpy, entropy, Gibb's free
energy. Intensive properties: These properties depend only upon the
amount of the substance present in the system, for example, temperature,
refractive index, density, surface tension, specific heat, freezing point, and
boiling point.
Types of thermodynamic processes: We say that a thermodynamic
process has occurred when the system changes from one state (initial) to
another state (final).
Isothermal process: When the temperature of a system remains constant
during a process, we call it isothermal. Heat may flow in or out of the
system during an isothermal process.
Adiabatic process: No heat can flow from the system to the surroundings
or vice versa.
Isochoric process: It is a process during which the volume of the system
is kept constant.
Isobaric process: It is a process during which the pressure of the system
is kept constant.
Reversible processes: A process which is carried out infinitesimally
slowly so that all changes occurring in the direct process can be exactly
reversed and the system remains almost in a state of equilibrium with the
surroundings at every stage of the process.
STUDY OF TWO STROKE I.C.ENGINES
In this engine, the working cycle is completed in two strokes of the piston or
one revolution of the crank shaft.
In case of two strokes engine, the valves are replaced by ports. Two rows
of ports at different levels are cut in the cylinder walls as shown in fig.
These are known as exhaust ports and transfer ports. In the case of single
cylinder engines, a third row of ports is provided below the first two and
these are known as inlet ports.
A specific shape is given to the piston crown as shown in fig Which helps to
prevent loss of incoming fresh charge entering into the engine cylinder
through the transfer port and helps in exhausting only burnt gases.
The charging of cylinder with air fuel mixture in case of petrol engine or with
air in case of diesel engine, compression of the mixture or air, expansion of
gases and exhausting of the burnt gases from the cylinder are carried out
in two strokes. This can be done by using the following two methods.
By using closed crank case compression. In this method crank case works
as an air pump as the piston moves up and down. The charge or air to be
admitted in the cylinder is compressed in crank case, by the pumping
action of underside of piston. This method is known as three channel
system & used for single cylinder small power engines like scooters &
motorcycles.
A separate pump outside the cylinder is provided to compress the charge
or air before forcing it into the cylinder. This pump is an integral part of an
engine & driven by engine it self. This method of charging is used for large
capacity multi-cylinder engines.
WORKING OF TWO STROKE PETROL ENGINE:
It will be easier to describe the cycle beginning at the point when the piston
has reached to TDC completing the compression stroke.
The position of the piston at the end of compression as shown in fig.( ). The
spark is produced by spark plug as the piston reaches the TDC (Top Dead
Centre). The pressure and temperature of the gases increases and the
gases push the piston downwards producing power stroke, when the piston
downwards producing power stroke. When the piston uncovers (opens) the
exhaust port as shown in fig ( ) during downward stroke, the expanded
burnt gases leave the cylinder through the exhaust port. A little later, the
piston uncovers (opens) the transfer port also as shown in (a). In this
condition the crank case is directly connected to cylinder through port.
During the downward stroke of piston, the charge in crank case is
compressed by the underside of the piston to a pressure of 1-4bar. At this
position, as shown in fig.( ), the compressed charge (fuel & air) is
transferred through the transfer port to the upper port of the cylinder. The
exhaust gases are swept out with the help of fresh charge (scavenging).
The piston crown shape helps in this sweeping action as well as it prevents
the loss of fresh charge carried with the exhaust gases. This is continued
until the piston reaches BDC position. During this stroke of piston
(downward stroke) the following processes are completed.
Power is developed by the downward movement of piston.
The exhaust gases are removed completely from the cylinder by
scavenging.
The charge is compressed in the crank case with the help of
underside of the piston.
As the piston moves upward, it covers transfer ports stopping flow of fresh
charge into the cylinder. A little later, the piston covers exhaust ports and
actual compression of charge begins. This position of piston is shown in fig.
The upward motion of the piston during this stroke lowers the pressure in
the crank case below atmosphere, therefore, a fresh charge is
admitted/induced in the crank case through the inlet port as they are
uncovered by the piston.
The compression of charge is continued until the piston reaches its original
position (TDC) and the cycle is completed.
In this stroke of the piston, the following processes are completed.
Partly scavenging takes place as the piston moves.
The fresh charge is sucked in the crank case through the Carburettor.
Compression of charge is completed as the piston moves.
The cycle of engine is completed within two strokes of the piston.
WORKING OF TWO STROKE DIESEL ENGINE:
As the piston moves down on the power stroke, it first uncovers the
exhaust port, and the cylinder pressure drops to atmospheric pressure as
the products of combustion come out from the cylinder. Further downward
movement of the piston uncovers the transfer port (TP) and slightly
compressed air enters the engine cylinder from the crank case. Due to
deflector on the top of the piston, the air will move up to the top of the
cylinder and expels out the remaining exhaust gases through the exhaust
port (EP).
During the upward movement of the piston, first the transfer port and then
the exhaust port closes. As soon as the exhaust port closes the
compression of the air starts. As the piston moves up, the pressure in the
crank case decreases so that the fresh air is drawn into the crank case
through the open inlet port as shown in fig. Just before the end of
compression stroke the fuel is forced under pressure in the form of fine
spray into the engine cylinder through the nozzle into this hot air. At this
moment the temperature of the compressed air is high enough to ignite the
fuel. It suddenly increases the pressure and temperature of the products of
combustion. The rate of fuel injection is such as to maintain the gas
pressure constant during the combustion period. Due to increased pressure
the piston is pushed down with a great force. Then the hot products of
combustion expand. During expansion some of the heat energy produced
is transformed into mechanical work. When the piston is near the bottom of
the stroke it uncovers exhaust port which permits the gases to flow out of
the cylinder. This completes the cycle and the engine cylinder is ready to
suck the air once again.
SPHERE LAB
building your own VMware vSphere lab
Part 1: Lab Overview (TechHead) and vinf,net Lab Series Overview
Part 2: Lab Hardware Configuration (TechHead) – Coming Soon!
Part 3: ESXi Installation & Configuration (TechHead) – Coming Soon!
Part 4: Shared Storage Installation & Configuration
– EMC Celerra (TechHead) – Coming Soon!
– HP LefHand (TechHead) – Coming Soon!
– StarWind iSCSI SAN (TechHead) – Coming Soon!
Part 5: Networking Configuration: VLAN’ing & Jumbo Frames (TechHead)
– Coming Soon!
Part 6: VM’ed ESXi (vinf.net) – Coming Soon!
Part 7: VM’d vCenter; auto start-up of VMs (vinf.net) – Coming Soon!
Part 8: VM’d FT and FT’ing vCenter VMs (vinf.net) – Coming Soon!
Part 9: FT on the ML115 series – benchmarking Exchange VMs (vinf.net) –
Coming Soon!
Part 10: VM’d Lab Manager farm environment on a pair of ML’s (vinf.net) –
Coming Soon!
Part 11: VM’d View 4 farm environment on a pair on ML’s (vinf.net) –
Coming Soon!
Part 12: Backing up your ESXi lab (Both) – Coming Soon!
Why build a virtualization lab?
Building your own virtualization lab either for home or work can serve many
purposes from providing an ideal test bed for those of you training for an
exam, wanting to test a new application or utility or just wanting to become
more familiar with building and running your own mini server infrastructure.
Gone are the days where running a multiple server lab environment meant
having a number of physical server whirring away creating costly electricity
bills, taking up plenty of space and not evening mentioning the noise and
heat generated. As you no doubt know the beauty of server virtualization is
that you can now run multiple VM server instances on a single piece of
server hardware greatly reducing many of the negative points mentioned
above.
From this single server you are able to run multiple operating systems
(OS), virtual appliance (VA) firewalls and network switches and even
nested instances of the hypervisor itself (ie: VMware ESX).
With the significant processing power found in modern processors and the
reduced cost of high capacity memory there has never been a better time
to build your own lab with as little as one server or decent desktop PC.
On with the show…
So hopefully I’ve now sold you on the virtues of running your own
virtualized server lab and have sparked your interest to find out how to
create your own.
Here’s an overview of the hardware and software that will be used in this
vSphere lab series:
Hypervisor
For these postings we will be using the latest
version of VMware ESX available at the time of
writing, this being ESXi 4.0 Update 1 (U1) along
with other components of the VMware vSphere
suite. One of the reasons ESXi was chosen over the full-fat ESX version
was that only ESXi can be installed onto a USB pen drive allowing us to
use 100% of the internal disk space of the servers as shared storage for
the VMs. Also as the service console portion of ESX is going to be
replaced in a future version of ESX now is a good time to familiarise
yourself with the remote command line (RCL).
Server:
For those of you that have read TechHead before already know that I
favour the HP Proliant ML110 and/or ML115 entry level servers for use in
my own virtualization test lab. My reasons for this are:
Reliability: I like HP kit as it has proven to be very reliable in
my years of being in IT. I have been running two ML110’s
and two ML115’s over the last 18 months both of which
have never had a hardware failure despite me working
them hard at times. I have only heard of one, what I’d call
serious hardware failure on them this being on Simon
Gallagher’s ML115 where he had a motherboard failure – though this was
resolved after HP had shipped him a new replacement board.
Cost: This is probably the most important factor for many in the server
selection process. The ML110 and ML115’s have fluctuated in price, at
least here in the UK, from a low bargain price of £80 each about 18 months
ago through to their current price of around £190 – which offers pretty good
value for money when you look at the specification of the server. I’ve found
that the prices from the various online vendors are usually pretty much the
same though have warmed to using ServersPlus as they have consistently
proven to provide the most competitive pricing and good pre and after sales
support. As a result I recommend them to others and have arranged a free
delivery deal for TechHead readers – as any savings in this current climate
has got to be a good thing. Check out my‘Hot Deals’ section for decent
offers that I am told about or see – I try and keep this updated regularly.
The HP ML115 has also proven to be cheap to run with an average load
consuming between 80-95 Watts of power – at least it does in my current
VMware lab.
Compatibility: On the whole the ML110/ML115 although never being on
the VMware ESX hardware compatibility list (HCL) has proven to be on the
whole almost fully compatible with VMware ESX. In the early ESX 3.5 days
there were issues with some of the onboard network controllers though in
later 3.5 releases this was no longer an issue. The largest bug-bear, as
you’d likely expect, has been around the storage controller compatibility
though across both models of server things have been pretty stable since
the ESX 3.5 U4 release. With the release of VMware vSphere and ESX 4.0
both G5 models of the ML110 and ML115 now work 100% – although they
are not officially on the HCL which may be a consideration from a VMware
support perspective if you were thinking of putting these servers into a live
production environment.
Here’s a video I put together that gives you a brief overview of the HP
ML115 G5:
Portability? Just add wheels!
Also with the relatively small form factor of the ML115 you can also
transport it much easier than a full sized enterprise level server. An
example of which can be seen with vinf’s vTARDIS.
Other options: Another popular method is to build your own ESX white
box. You can actually end up building quite a powerful and cheap ESX
host if you can put together the correct ESX compatible parts. There are
some good sources out on the web that maintain active lists of what
motherboards, disk controllers and network cards have been proven to
work with the different versions of ESX. Here are some of these sites that
you may want to take a look at if considering building an ESX white box
solution.
Ultimate ESX WhiteBox
VMware Communities Maintained List
VM-Help WhiteBox Compatibility List
Others such as vinf.net have looked towards a desktop white box solution
such as the HP D530 for hosting their ESX environment.
Networking:
For my networking hardware in my virtualization home
lab I use a pair of eight port Linksys SLM2008 gigabit
switches. The reason I use two is that I need this many
ports if running most of my ML110 and ML115’s with
shared iSCSI storage and wanting to have dedicated network connections
for vMotion and FT traffic, etc. I also have a main PC from which I manage
my environment which also requires a port or two. As I postedhere I have
found the Linksys SLM2008 switches to offer great bang for buck for use in
a lab type environment. It has the necessary features such as VLAN
tagging and Jumbo Frames which do come in useful when you start
wanting to implement the more enterprise level features with your
ESX/ESXi hosts.
Storage:
To use many of the useful features within VMware ESX such
as DRS, HA and FT you’ll need shared storage. For the purposes of this
series I have decided to walk onto the storage vendor parking lot and kick a
few tyres. The three vendors (EMC, HP and StarWind) I have chosen all
have storage products suitable for virtualised environments that I have
wanted to take a more in depth look at for sometime now.
All three of these storage vendors offer products that can be run as a virtual
appliance which will either pool and share the local disk of the ML115’s or
share out the local disk to ESX and then replicate it between both of the
ESX nodes (ie: ML115’s). These are a couple of different methods for
presenting shared storage so it’s going to be fun to go into more depth with
them in the lab.
Here’s a summary of the storage virtual appliances I will be reviewing and
using:
EMC Celerra VSA
HP LeftHand VSA
StarWind iSCSI SAN Virtual Appliance
The good news is that if you are following this ‘build your own vSphere lab’
series by constructing your own home or work lab you can download fully
working evaluation copies of all of these products to which I will be
providing the links.
Strength of materials, also called mechanics of materials, is a subject which
deals with the behavior of solid objects subject to stresses and strains. The
complete theory began with the consideration of the behavior of one and
two dimensional members of structures, whose states of stress can be
approximated as two dimensional, and was then generalized to three
dimensions to develop a more complete theory of the elastic and plastic
behavior of materials. An important founding pioneer in mechanics of
materials was Stephen Timoshenko.
The study of strength of materials often refers to various methods of
calculating the stresses and strains in structural members, such as beams,
columns, and shafts. The methods employed to predict the response of a
structure under loading and its susceptibility to various failure modes takes
into account the properties of the materials such as its yield
strength, ultimate strength, Young's modulus, andPoisson's ratio; in
addition the mechanical element's macroscopic properties (geometric
properties), such as its length, width, thickness, boundary constraints and
abrupt changes in geometry such as holes are considered.
Types of loadings
Transverse loading - Forces applied perpendicular to the longitudinal axis
of a member. Transverse loading causes the member to bend and deflect
from its original position, with internal tensile and compressive strains
accompanying the change in curvature of the member.[1] Transverse
loading also induces shear forces that cause shear deformation of the
material and increase the transverse deflection of the member.
Axial loading - The applied forces are collinear with the longitudinal axis of
the member. The forces cause the member to either stretch or shorten.[2]
Torsional loading - Twisting action caused by a pair of externally applied
equal and oppositely directed force couples acting on parallel planes or by
a single external couple applied to a member that has one end fixed
against rotation.
Design Terms
Ultimate strength is an attribute related to a material, rather than just a
specific specimen made of the material, and as such it is quoted as the
force per unit of cross section area (N/m2). The ultimate strength is the
maximum stress that a material can withstand before it breaks or weakens.
[12] For example, the ultimate tensile strength (UTS) of AISI 1018 Steel is
440MN/m2. In general, the SI unit of stress is the pascal, where 1 Pa = 1
N/m2. In Imperial units, the unit of stress is given as lbf/in² or pounds-force
per square inch. This unit is often abbreviated as psi. One thousand psi is
abbreviated ksi.
A Factor of safety is a design criteria that an engineered component or
structure must achieve. , where FS: the factor of safety, R: The
applied stress, and UTS: ultimate stress (psi or N/m2) [13]
Margin of Safety is also sometimes used to as design criteria. It is defined
MS = Failure Load/(Factor of Safety * Predicted Load) - 1
For example to achieve a factor of safety of 4, the allowable stress in an
AISI 1018 steel component can be calculated to be = 440/4 = 110
MPa, or = 110×106 N/m2. Such allowable stresses are also known
as "design stresses" or "working stresses."
Design stresses that have been determined from the ultimate or yield point
values of the materials give safe and reliable results only for the case of
static loading. Many machine parts fail when subjected to a non steady and
continuously varying loads even though the developed stresses are below
the yield point. Such failures are called fatigue failure. The failure is by a
fracture that appears to be brittle with little or no visible evidence of
yielding. However, when the stress is kept below "fatigue stress" or
"endurance limit stress", the part will endure indefinitely. A purely reversing
or cyclic stress is one that alternates between equal positive and negative
peak stresses during each cycle of operation. In a purely cyclic stress, the
average stress is zero. When a part is subjected to a cyclic stress, also
known as stress range (Sr), it has been observed that the failure of the part
occurs after a number of stress reversals (N) even if the magnitude of the
stress range is below the material’s yield strength. Generally, higher the
range stress, the fewer the number of reversals needed for failure.
Failure theories
here are four important failure theories: maximum shear stress theory,
maximum normal stress theory, maximum strain energy theory, and
maximum distortion energy theory. Out of these four theories of failure, the
maximum normal stress theory is only applicable for brittle materials, and
the remaining three theories are applicable for ductile materials. Of the
latter three, the distortion energy theory provides most accurate results in
majority of the stress conditions. The strain energy theory needs the value
of Poisson’s ratio of the part material, which is often not readily available.
The maximum shear stress theory is conservative. For simple unidirectional
normal stresses all theories are equivalent, which means all theories will
give the same result.
Maximum Shear stress Theory- This theory postulates that failure will occur
if the magnitude of the maximum shear stress in the part exceeds the shear
strength of the material determined from uniaxial testing.
Maximum normal stress theory - This theory postulates that failure will
occur if the maximum normal stress in the part exceeds the ultimate tensile
stress of the material as determined from uniaxial testing. This theory deals
with brittle materials only. The maximum tensile stress should be less than
or equal to ultimate tensile stress divided by factor of safety. The
magnitude of the maximum compressive stress should be less than
ultimate compressive stress divided by factor of safety.
Maximum strain energy theory - This theory postulates that failure will
occur when the strain energy per unit volume due to the applied stresses in
a part equals the strain energy per unit volume at the yield point in uniaxial
testing.
Maximum distortion energy theory - This theory is also known as shear
energy theory or von Mises-Hencky theory. This theory postulates that
failure will occur when the distortion energy per unit volume due to the
applied stresses in a part equals the distortion energy per unit volume at
the yield point in uniaxial testing. The total elastic energy due to strain can
be divided into two parts: one part causes change in volume, and the other
part causes change in shape. Distortion energy is the amount of energy
that is needed to change the shape.
Fracture mechanics was established by Alan Arnold Griffith and George
Rankine Irwin. This important theory is also known as numeric conversion
of toughness of material in the case of crack existence.
Fractology was proposed by Takeo Yokobori because each fracture laws
including creep rupture criterion must be combined nonlinearly.
Microstructure
A material's strength is dependent on its microstructure. The engineering
processes to which a material is subjected can alter this microstructure.
The variety of strengthening mechanisms that alter the strength of a
material includes work hardening, solid solution strengthening, precipitation
hardening and grain boundary strengthening and can be quantitatively and
qualitatively explained. Strengthening mechanisms are accompanied by the
caveat that some other mechanical properties of the material may
degenerate in an attempt to make the material stronger. For example, in
grain boundary strengthening, although yield strength is maximized with
decreasing grain size, ultimately, very small grain sizes make the material
brittle. In general, the yield strength of a material is an adequate indicator of
the material's mechanical strength. Considered in tandem with the fact that
the yield strength is the parameter that predicts plastic deformation in the
material, one can make informed decisions on how to increase the strength
of a material depending its microstructural properties and the desired end
effect. Strength is expressed in terms of the limiting values of
the compressive stress, tensile stress, andshear stresses that would cause
failure. The effects of dynamic loading are probably the most important
practical consideration of the strength of materials, especially the problem
of fatigue. Repeated loading often initiates brittle cracks, which grow until
failure occurs. The cracks always start at stress concentrations, especially
changes in cross-section of the product, near holes and corners at nominal
stress levels far lower than those quoted for the strength of the material.
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