Shot peening is a well established process for the surface enhancement of gearing. Gearing is a primary example of a high cycle fatigue application that can benefit from residual stress enhancement. Designing shot peening parameters to specific gear geometry based on material, heat treatment, and surface finish is a more precise way to achieve better performance outcomes. One of the best tools to assist in the optimal shot peening is x-ray diffraction (XRD) and its ability to measure small differences that can result in significant performance outcomes. XRD residual stress measurements are a direct measurement of elastic strain. The diffraction peak width is an indication of plastic strain and is also proportional to the hardness of steels. Together, the elastic and plastic strain information provides tremendous insight into the condition of a shot peened gear. This paper will review a wide variety of gear geometry and their various heat treatments and surface finishes. The discussion will encompass how the shot peen parameters can be modified based on the physical characteristics of the gear and also the failure mode. X-ray diffraction results will be provided to supplement the discussion.
Breuer et al. (Wed,) studied this question.