In-Situ Image-based Crack Measurement Methodology for Gear Single Tooth Bending Fatigue Testing

Abstract

Gear teeth undergo cyclic forces as they travel through the mesh zone. The resultant contact and bending stresses produce fatigue damage, which can lead to failure through contact surface degradation and tooth breakage through the root fillet. The fatigue process is not instantaneous, and damage accumulates at different rates throughout the fatigue life. Many proposed diagnostics and health monitoring techniques to detect the onset of gear failure are based on changes in mechanical properties due to crack growth. Moreover, theoretical studies to predict fatigue crack growth rate rely on only a few experimental measurements for their validation with little extension to gears which typically have a gradient in material properties between a hardened case and a soft core. The focus of this study is to develop an image-based system for measuring surface crack length in gear tooth bending fatigue of a spur gear. A gear single tooth bending test methodology is utilized in conjunction with a high-speed camera setup to image the tooth during every loading cycle. An image processing technique is developed and used to compute crack length during each load cycle to obtain cyclic crack growth rate.

Topics & Concepts