Abstract
In order to evaluate the influence of materials and methods of case hardening on the bending fatigue strength of full size gears, induction hardened, carburized and quench-tempered gears made of various plain carbon and low alloy steels are subjected to pulsating bending stress. The gears used for the test are of 20° pressure angle with 34 teeth and 8 module.
The strengths at the root of gears are raised more than twice by case hardening due to the induced compressive residual stress and the increased hardness. The effects of these factors are evaluated by a regression analysis. The anlyasis indicates that, regardless of the materials used, the contribution of the residual stress to the increase in fatigue strength is about 68% in the case of induction hardening and about 55% in the case of carburizing, and the remainder contribution is due to the increased hardness.
