In this article, we learn the mechanical properties of materials.
Properties of Materials
Material is that, out of which anything is made. It relates itself to matter.
The knowledge of materials and their properties is of great significance for a design engineer.
The machine elements should be made from a material that has properties suitable for the operating conditions.
The property of a material is a factor that influences qualitatively or quantitatively the response of a given material under the action of forces, temperatures, pressures, etc.
The property indicates that, whether a material is suitable or unsuitable for a particular use in an industry.
The material property is independent of the dimension or shape of the material.
The various material properties are divided into the following groups:
- Mechanical properties of Materials
- Thermal properties of Materials
- Electrical properties of Materials
Mechanical Properties of Materials
Mechanical properties include those characteristics of the material that describe its behavior under the action of external forces.
The knowledge of the mechanical properties of materials is very essential in order to construct a mechanically fool-proof structure.
Some of the important mechanical properties are as follows:
1. Elasticity
It is the property of the material to regain its original shape after deformation when the external forces are removed.
This property is required for materials used in tools and machines.
It is important to note that, steel is more elastic than rubber.
2. Plasticity
The property of a material that retains the deformation produced under the load permanently is called plasticity.
This property is essential in stamping, press work, forgings, ornamental work, etc.
3. Toughness
Toughness is the total amount of energy absorbed by the material before its failure.
It is the complete area under the stress-strain curve i.e. summation of the elastic and plastic regions.
This property is essential in parts subjected to shock and impact loads.
4. Resilience
The resilience of a material is defined as the total amount of energy absorbed by the material during its elastic deformation.
This property is essential for springs, shock absorbers, etc.
The area under stress-strain curve in the elastic region indicates resilience.
5. Strength
It is the ability of a material to resist externally applied forces without failure.
It is measured in kg/mm’ or 11/m.m2.
6. Stiffness
It is the ability of a material to resist deformation under stress.
It is also defined as the force or load per unit deflection. It is measured in N/mm.
7. Ductility
It is defined as the ability of a material to undergo plastic deformation under tensile loading, before its fracture.
Also, ductility is the property of a material by which it can be drawn into fine wires. For example rubber.
8. Malleability
It is defined as the ability of a material to be formed by hammering or rolling.
It is the capacity of a material to withstand deformation under compression without failure.
The main difference between ductility and malleability is that ductility is considered as tensile property and malleability is considered as compressive property.
9. Brittleness
It is the property of breaking material with little permanent distortion.
The brittleness of material is opposite to ductility. For example glass, concrete blocks, etc.
10. Hardness
It is an important property of metals.
It is defined as the resistance of metal to plastic deformation usually by indentation.
It is also defined as resistance to scratch, abrasion, or cutting.
11. Fatigue
When a material is subjected to repeated stresses or loading, it fails at stresses below the yield point stress. Such a type of failure of material is called fatigue.
Fatigue failure is caused by means of progressive crack formations which are generally of microscopic size.
It is considered while designing shafts, gears, springs, etc.
12. Creep
When a material is subjected to constant stresses at high temperatures for a. long period of time, it will undergo a slow and permanent deformation which is called creep.
It is considered while designing of boilers, I.C. engines, pumps, turbines, etc.
MCQ
Q.1 Define the mechanical properties of materials?
Q.2 Describe any six mechanical properties of materials?
Q.3 Define the following mechanical properties of materials:
a) Malleability b) Resilience c) Toughness d) Hardness