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MECHANICAL THEORY

31 Mechanical properties of Materials that every Mechanical engineer must know-Interview

Mechanical properties of materials:If you are a design engineer from the field of Mechanical Engineering then you should has to know about mechanical properties of Materials so that those can be taken into consideration while designing.because you are the one,who can knows about the need and according to that need,what type of material can be taken was dependent on you.
That’s the basic consideration every design engineer must follow in picking upon the best material depending upon the Mechanical properties of materials.Considering this fact,I will be explaining about 31 Mechanical properties of materials that every Mechanical engineer must know in this article in a detailed manner.Read this article completely so that it can be used in Interviews also.

31 Mechanical properties of Materials that every Mechanical engineer must know-Interview
31 Mechanical properties of Materials that every Mechanical engineer must know-Interview

31 Mechanical properties of materials that every Mechanical engineer must know-Interview

31 Mechanical properties of materials:

The 31 Mechanical properties of materials that every Mechanical engineer must know was explained below.
1.Strength:
Ability of a material that can withstand to Mechanical load is called Strength of that particular material.
• Strength of the material depends upon the directions in which it is loaded
• Ex:Tensile Test
• From Tensile Test,we get Tensile Strength,ductility,fracture toughness,resilience,yield stress etc.

2.Ductility:
Ability of a material that can undergo plastic deformation before failure is called as Ductility.
Ductility (D)= % of Elongation in length or % of Reduction in Cross section at breaking point.
Note: Ductility is always reported in % of elongation in length but not in % of reduction in c/s area because reduction in c/s section area is small and difficult to measure during testing.
% of elongation at different Temperatures:
If you can see the % of elongation of a metal w.r.t.Low temperature(L.T),Room temperature(R.T) and High temperature(H.T) was
D(L.T)<D(R.T)<D(H.T)
3.Fracture Toughness:
Ability of a material that can absorb energy at the time of failure against fracture is called as Fracture Toughness.
• By calculating the area under stress v/s strain curve upto the failure point,the fracture toughness of the material is determined.
• A material possess high fracture toughness means it has higher capability to absorb more strain energy against failure.
• A brittle material possess lower the fracture toughness(F.T) compared to a ductile material because area under the curve
A Ductile > A Brittle
F.T Ductile > F.T Brittle
Considering area of Stress v/s Strain curve at different temperatures is noted as follows.
A H.T > A R.T > A L.T
That implies

F.T H.T > F.TR.T > F.T L.T
If a material is tested at high temperature,the displacement of atomic planes is easy,implies it can produce more plastic strain,implies area under the curve will be more,implies Fracture Toughness is high.

4.Hardness:
Resistance offered by the material against mechanical deformation is called as hardness.

5.Brittleness:
Ability of a material that can withstand to mechanical load without plastic deformation is called as Brittleness.

6.Stiffness:
Ability of a material that can resist mechanical deformation under stress is called stiffness.

7.Creep:
Time v/s Strain behavior of a material under Constant mechanical load is called as Creep.

8.Fatigue:
Stress v/s no. of load cycles of behavior of metal under changing mechanical load with Time is called as Fatigue.
• Fatigue is danger than Creep
• Therefore,more FOS is given for Fatigue loading.

9.Malleability:
It is a capability of being extended or shaped by beating with a hammer or by the external pressure of rollers so that the output is in the form of thin sheets called as Malleability.

10.Plasticity:
The quality of being easily shaped or molded called as Plasticity.

11.Elasticity:
The ability of an object or material to resume or regain its normal shape or original shape after being stretched or compressed called as Elasticity.

12.Toughness:
It is the state of being strong enough in order to withstand adverse conditions or rough handling called as Toughness.
or
It is also defined as the Area under P.(Delta) curve up to Failure is called as Toughness.

13.Tensile strength:
The resistance of a material to breaking under tension called as Tensile Strength.

14.Compressive strength:
The resistance of a material to breaking under Compression is called as Compressive strength.

15.Resilience:
Ability of a material that can absorb energy without undergoing any shape change called as Resilience.
Ex:Steel
• By calculating the area under Stress v/s Strain curve upto elastic point,resilience(elastic resilience) of the material will be determined.
These are the 15 Mechanical properties of materials that are explained in a detailed manner

16.Hardenability:

The hardenability of a metal alloy is the depth up to which a material is hardened after putting through a heat treatment process called as hardenability.

17.Machinability:

It is a process of removing the layer from the surface of workpiece so as to get good surface finish on the outer surface of the material called as Machinability.

In the most general case good machinability means that material is cut with good surface finish, long tool life, low force,power requirements and low cost.

18.Stress:

When a material is loaded with a force, it produces a stress which then causes a material to deform.

or

Stress is defined as “force per unit area” – the ratio of applied force F to cross section area is called as stress.

19.Strain:

It is defined as the ratio of change in dimension to its original dimensions called as strain.

  • It is denoted by “Ɛ”
  • It is a Dimensionless parameter
  • Strainis the response of a system to an applied stress.

20.Youngs Modulus:

Young’s modulus is the ability of a material to withstand changes in length when under lengthwise tension or compression.

  • It is denoted by E.
  • It is also defined as the ratio of stress to strain.

21.Elastic deformation:

It is a change in the shape of a material at low stress that is recoverable after the stress is removed called as Elastic deformation of a material.

or

A temporary shape change that is self-reversing after the force is removed, so that the object returns to its original shape called as elastic deformation

22.Plastic deformation:

Plastic deformation is a process in which permanent deformation is caused by a sufficient load. It produces a permanent change in the shape or size of a solid body without fracture, resulting from the application of sustained stress beyond the elastic limit.

After plastic deformation, no elastic recovery takes place.

23.Factor of safety:

It is the load carrying capacity of a system beyond the expected or actual loads. or

factor of safety is how much stronger the system is than it usually needs to be for an intended load.

Factor of safety is different for brittle and ductile materials.

24.Elastic Recovery:

It is the measure of the ability of an elastomer to return to its original shape when a compression load or external load is removed called as Elastic Recovery.

25.Engineering stress:

Engineering stress is the applied load divided by the original cross-sectional area of a material. It is also called as nominal stress.

26.True stress:

True stress is the applied load divided by the actual cross-sectional area (the changing area with respect to time) of the specimen at that load.

27.Poissons Ratio:

Poisson’s ratio is the ratio of transverse contraction strain or Lateral strain to the longitudinal extension strain(Linear strain).

28.Bulk Modulus:

It is the relative change in the volume of a body produced by a unit tensile or compressive stress acting uniformly over its surface.

29.Rigidity Modulus:

It is also known as shear modulus

It is the defined as the ratio of shear stress to the shear strain.

This is the detailed explanation of Mechanical properties of materials. Hope,this information is helpful to you.

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One Comment

  1. I didn’t realize that plastic deformation referred to a permanent change to a metal due to weight or pressure. Doing some kinds of testing to see how strong a metal is would probably be pretty important. That way you know just how much it can hold before it starts to break or change.
    http://www.labinc.com/mech.htm

    Reply

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