Table of Contents
Definition
If a body gets deformed under the action of an external force, then at each section of the body an internal force of reaction is set up which tends to restore the body into its original state. The internal restoring force set up per unit area of cross-section of the deformed body is called stress. As the restoring force is equal and opposite to the external deforming force, therefore
Stress = Force / Area
The SI unit of stress is Nm-2 and the CGS unit is dyne cm-2. The dimensional formula of stress is [ML-1T-2].
Types of stress:
(i) Tensile stress:
It is the restoring force set up per unit cross-sectional area of a body when the length of the body increases in the direction of the deforming force. It is also known as longitudinal stress.
(ii) Compressional stress:
It is the restoring force set up per unit cross-sectional area of a body when its length decreases under a deforming force.
(iii) Hydrostatic stress:
If a body is subjected to a uniform force from all sides, then the corresponding stress is called hydrostatic stress.
(iv) Tangential or Shearing stress:
When a deforming force acts tangentially to the surface of a body, it produces a change in the shape of the body. The tangential force applied per unit area is equal to the tangential stress.