Stress and strain
When a body is subjected to a system of external forces, it undergoes a deformation. At the same time, by virtue of its strength, it offers a resistance against this deformation. This internal resistance offered by the body to counteract the applied load is called stress.
The resistance per unit cross sectional are is called stress. The deformation in unit original dimension is termed as stain.
Types of stresses and strains
When an external force produces elongation of the body in its direction, it is termed as tensile force.
P= External tensile load
R= Resistane induced in the material of the body
A=Cross sectional area
Tensile stress =Tensile load / Cross sectional are of the body
Tensile strain =Increase in length/ Original length
When an external force causes shortening of the body in the direction of force, it is termed as a compressive force. The stress developed in the body due to a compressive force is called as compressive stress.
P= External compressive load
R=Resistance induced in the material of the body
A=Cross sectional area of the body
Compressive Stress = compressive load/ cross sectional area of the body
Compressive strain = decrease in length/ Original length
When a body is subjected to two equal and opposite forces acting tangentially across the resisting section, as a result of which the body tends to shear off across the section, then this tangential force is termed as shear force and the stress induced is called shear stress.
Shear stress = Shear force/ Shear area
Shear strain =Transverse displacement/ Distance from the fixed base
The change in volume of an elastic body due to external force in unit original volume is called as the volumetric strain
Volumetric strain = dv/V
When a material is subjected to uni-axial stress within the elastic limit, it deforms not only longitudinally but also laterally. Under tension the lateral dimensions diminish and under compression they increase. The lateral deformation per unit original lateral dimension is called lateral strain.