PLANE STRESS AND STRAIN (1)

A REVIEW ON FORCE:

A force exerted on a body can cause a change in either the shape or the motion of the body. The unit of force is the newton*, N. No solid body is perfectly rigid and when forces are applied to it, changes in dimensions occur. Such changes are not always perceptible to the human eye since they are so small.

The three main types of mechanical force that can act on a body are:

(i) tensile

(ii) compressive and;

(iii) shear

Tensile is a force that tends to stretch a material.A tensile force, i.e. one producing tension, increases the length of the material on which it acts.

Compression is a force that tends to squeeze or crush a material.A compressive force, i.e. one producing compression, will decrease the length of the material on which it acts.

Shear is a force that tends to slide one face of the material over an adjacent face. A shear force can cause a material to bend,slide or twist.