Definition of Stress:
While a load is applied to metal then the atomic structure itself is strained, being compressed, warped or extended within the procedure. The atoms comprising a metal are arranged inside a certain geometric pattern and specific for that particular metal or alloy, and are maintained in which pattern through interatomic forces. When so arranged, the atoms are in their state of minimum energy and tend to remain in which arrangement. Work must be complete on the metal (which is, energy have to be added) to distort the atomic pattern. (Work is equivalent to force times the distance the force moves.)
Stress is the internal resistance, or counterfource, of a material to the distorting effects of an external force or load. Those counterforces tend to return the atoms to their general positions. A total resistance established is equal to the external load. This resistance is called as stress.
While it is impossible to measure the intensity of this stress, the external load and the area to that it is applied can be measured. Stress (σ) could be equated to the load per unit area or the force (F) applied per cross-sectional area (A) perpendicular to the force as display in Equation (2-1).
Stress = σ = F/A (2-1)
where:
σ= stress (psi or lbs of force per in.2)
F = applied force (lbs of force per in.2)
A = cross-sectional area (in.2)