When a body is subjected to external loads, it is important to examine the resultant forces and moment acting within it. If we consider the internal resultant loadings at a particular plane in a body under loading, we cannot just examine the magnitude of the load to determine if the body has sufficient strength. We need to consider the loading RELATIVE to the area over which it is acting.
In order to consider the STRENGTH of a material, you need to consider its ability to resist levels of STRESS.
STRESS is a quantity that describes the intensity of the internal force per unit area acting on a specific plane (area) passing through a point.
A point within a body under loading can be subjected to FOUR possible types of stresses:
· NORMAL STRESS,
· SHEAR STRESS,
· TORSIONAL STRESS and
· BENDING STRESS
The magnitude of these stresses is dependent on the loading conditions of the body of interest.