Torsional Strength for Induction Hardened Shafts Applied in Homocinetic Half Shafts

The homocinetic half shaft is an automotive component whose function is to transmit torque from the engine to the wheels allowing its steering and the suspension system displacement. Besides the homocinetic joints, there is an interconnecting (IC) shaft which is the rigid element that links both of them. Whenever static torsion tests are realized with these half shafts, the IC shaft is a critical component that deserves a deeper approach. When a circular shaft is torsionally loaded, the shear stress is maximum at the component surface and zero at the center. So, these shafts are submitted to an induction hardening process that enables only this superficial case to have its properties changed, remaining the core with its material original characteristics. This paper aims to determine the static torsion strength for induction hardened shafts, and compare these results to experimental tests in order to confirm the approach. Finally, it intends to evidence the important function of this heat treatment to torsionally loaded shafts and to verify its influence on the mechanical resistance of the component.