Tensile stress and tensile strain

Consider a vertical bar of length ‘L’ and cross sectional area ‘A’ fixed at its top as shown in above image. Let a downward axial load, P is applied at its bottom (free end). The support at top now offers an upward reaction equal to the applied load, P to keep the bar in its position. The applied load now tends the bar to elongate by an amount ‘delta L’. This load which causes elongation of the member is termed as a tensile load. The member which is subjected to a tensile load is said to be a tie member.

          Now the internal stress developed in the bar (P/A) due to the tensile force is called the ‘tensile stress’ and the corresponding strain in the bar is called the tensile strain.

          The applied load at the free end and the reaction at the support are two forces which are equal in magnitude but opposite in direction. Therefore it should be remembered that tensile stress and tensile strain are developed in a member when two equal and opposite axial force act on it, outwards away from the center of gravity of the member.