Whenever a load is applied on a deformable solid, to find out whether the load will cause failure or not is decided by stress. Strength of the material is the stress the material can take up to failure. To understand the strength of the material concept of stress should be clear
Stress plays a vital role in deciding whether the load applied on the component causes failure or not. If stress value is higher than the strength of the material it will fail. Stress is the internal resistive force produced in the material per unit area of cross section due to he applied load. For this internal resistive force to be produced the material should be in equilibrium. Hence equilibrium is necessary for the material to experience stress.