# Torsion Formula | Strength of Material ME

Real Life Application Torsion occurs in the machine elements of shafts like drive shafts, power shafts of automobiles etc. It also occurs in many other applications where rotatory components are present. This topic helps us to understand to keep the stresses induced to be in safe limits.

Explanation To understand the concept with clarity it’s important to have basic idea of stress, normal stress, shear stress and analysis of stress. Torsion occurs in the members when a longitudinal moment acts at a cross section. Torsion causes shear stress inside the material. The magnitude of shear stress, angle of twist, torque acting, polar sectional modulus are related with the torsional equation. For the sign convention is concerned counter clockwise torques are taken as positive and clockwise torques are taken as negative. When the shafts are in series we have to find the individual torques on the individual shafts and the angle of twist at the free end is equal to algebraic sum angle of twists of the shafts. For statically indeterminate numericals the compatibility condition will be that the angle of twist is same in both the parts. It is same in shafts in parallel as well. In the comparison of hollow shafts and solids of same mass and length, the polar sectional modulus of the hollow shaft is greater than solid shaft hence stress induced is lesser and torque carrying capacity is higher for the hollow shaft . Hence it is preferred over solid shaft.