In this article, we will learn about 13 Basic Mechanical Properties Of Material. These properties are widely used for material selection depend upon application nature.

Introduction

 

Mechanical properties of the material are related to the behaviour under load or stress in tension, compression and shear.

Mechanical properties are determined by engineering tests under appropriate conditions. Commonly determined mechanical properties are tensile strength, yield point, elastic limit, creep strength, stress rupture, fatigue, elongation (ductility), impact strength (toughness and brittleness), harness, and modulus of elasticity(ratio of stress to elastic strain-rigidity). The strain may be elastic (present only during stressing) or plastic (permanent) deformation.

Mechanical properties are helpful to understand the desired shape obtained from the material. Also, helpful to understand the material resistance to the anticipated mechanical forces

The words mechanical and physical are often erroneously used interchangeably. The above are mechanical properties. Sometimes modulus of elasticity considered to be a physical property of material because it is an inherent property that cannot be changed substantially by practical means such as heat treatment or cold-working.

Mechanical Properties

Strength

The ability of a material to resist the externally applied forces without breaking or yielding. The internal resistance offered by a part to an externally applied force is called stress.

Stiffness

Stiffness refers to the ability of a material to resist deformation under stress. Modulus of elasticity measure the stiffness of the material.

Elasticity

The property of a material to regain its original shape after deformation, when the external forces are removed. This property has desirable for materials used in tools and machines.

It may be noted that steel is more elastic than rubber.

Plasticity

Plastic property of a material refers to the deformation material under load permanently. This property of the material necessary for forgings, in stamping images on coins and in ornamental work.

Ductility

Ductility property of material enables to drawn into the wire with the application of a tensile force. A ductile material must be both strong and plastic. The ductility usually measured by the terms, percentage elongation and percentage reduction in area. The ductile material commonly used in engineering practice are mild steel, copper, aluminium, nickel, zinc, tin and lead.

Brittleness

The property of breaking of a material with little permanent distortion. Brittleness of material opposite to ductility property.

Brittle materials withstand compression load. When subjected to tensile loads snap off without giving any sensible elongation. Cast iron is the brittle material.

Malleability

It’s a special case of ductility which permits materials to rolled or hammered into thin sheets, making wire. A malleable material should be plastic but it’s not essential to be so strong. The malleable materials commonly used in engineering practice are lead, soft steel, wrought iron, copper and aluminium.

Toughness

It’s a property of a material to resist fracture due to high impact. The amount of energy that a unit volume of the material has absorbed after being stressed up to the point of fracture.

This property has desirable in parts subjected to shock and impact loads. Normally the toughness of the material decreases when subjected to heat.

This property plays a major role in the design of the hammer and Press machine.

Machinability

It’s the property of a material which refers to the relative ease with which a material can be cut. The machinability of a material measured as follows

• Comparing the tool life for cutting different materials
• Thrust required to remove the material at some given rate
• The energy required to remove a unit volume of the material.

For example, brass can be easily machined than steel, that means the machinability property of brass higher than steel.

Resilience

It is the property of a material to absorb energy and to resist shock and impact loads. Resilience measures the amount of energy absorbed per unit volume within the elastic limit. This property plays a major role in the design of spring materials.

Creep

When material subjected to constant stress at high temperature for a long period of time, it will undergo a slow and permanent deformation called creep.

This property plays a major role in the design of internal combustion engines, boilers and turbines.

Fatigue

Fatigue is the repeated loading and unloading of metal due to direct load variation, eccentricity in a rotating shaft, or differential thermal expansion of a structure. Even substantially below the yield point (elastic limit) of a metal or alloy this repeated loading can lead to failure, usually measured in terms of

the number of cycles (repeated load applications) to failure.

Some studies have suggested that well over 80% of all mechanical failures of metal are attributable to fatigue.

This property plays a major role in the design of shafts, connecting rods, springs, gears etc.

Hardness

It is a very important property of metal and has a wide variety of meanings. It embraces many different properties such as resistance to wear, scratching, deformation and machinability etc.

Hardness, the ability of materials to resist being permanent deformed when a load applied (ie., bent, broken or shape change). The greater the hardness, greater resistance to deformation.

It also means the ability of a metal to cut another metal. The hardness usually expressed in numbers which are dependent on the method of making the test.

The below-listed tests to determine the material hardness

• Brinell hardness test
• Rockwell hardness test
• Vickers hardness (also called Diamond Pyramid) test
• Shore scleroscope.

Other properties of materials

These include density or specific gravity ( needed to calculate corrosion rates) fluidity or castability, formability, thermal, electrical, optical, acoustic and magnetic properties.

Conclusion

By understanding these 13 Basic Mechanical Properties Of Material one can able to select a correct material for the specific application.