Abstract
In the previous report, the various factors that affect the endurance limit of induction hardened steel were examined. It was found that the microstrain and particle size are more influential than the residual stress on the endurance limit of both induction hardened smooth and notched specimens.
The present paper describes an experimental study conducted on the surface hardness, residual stress, microstrain and particle size of smooth specimens tempered at various temperature in order to clarify the influence of tempering temperatures upon the fatigue strength.
It has been found that a linear relation exists between the integral width of a diffraction pattern and the endurance limit. The physical meaning of this relation has been examined according to the diffraction profile analysis of Williamson and Hall. A linear relation also exists among the endurance limit, microstrain and particle size of induction hardened steel specimens tempered at various temperatures, which is a better relation than the one involving surface hardness and microstructure. Based on these results the significance of microstrain and particle size as strength-determining factors has been clarified.
