Chapter 8 - Torsion

Abstract

This chapter discusses simple torsion theory, polar second moment of area, shear stress and shear strain in shafts and section modulus. Torsional rigidity is discussed and the torsion of hollow shafts and thin-walled tubes is highlighted. The chapter also discusses composite shafts-series connection, composite shafts-parallel connection, principal stresses, and power transmitted by shafts. When a uniform circular shaft is subjected to a torque, every section of the shaft is subjected to a state of pure shear, the moment of resistance developed by the shear stresses being equal everywhere to the magnitude and opposite in sense, to the applied torque. For the purposes of deriving a simple theory to describe the behavior of shafts subjected to torque, it is necessary to make the following basic assumptions, such as the material is homogeneous—that is, of uniform elastic properties throughout; or the material is elastic, following Hooke's law with shear stress proportional to shear strain. The chapter explains angle of twist, various stresses, and polar second moment of area with respect to the torsion theory.