Experimental investigation on crack propagation paths in spur gears

Abstract

Spur gears subjected to bending fatigue may nucleate cracks at the tooth root fillet. In thin rim gears these cracks may propagate in a safe way (through the tooth) or in catastrophic way (through the rim). Crack propagation direction is mainly influenced by both wheel geometry parameters and crack initiation point, as already pointed out by theoretical and numerical results available in literature. Aim of this work is to set up an experimental activity in order to verify the onset of the bending crack and its propagation path in spur gears with different geometries. In particular, a special device connected to a standard fatigue machine was realized to perform bending tests for both standard and thin rim gears. During bending tests, an IR thermocamera was utilized to monitor the surface thermal profile in the tooth root fillet zone.

DIC analysis of gears in bending condition

“…Gears are made of C45 steel without thermal treatments. Technical drawings of both the tested gears (standard and thin-rim), as depicted in [9], are shown in Figure 1.…”

“…This aspect was widely investigated from the numerical point of view, traditional 2D and 3D finite elements (FEM) and extended finite elements (XFEM) simulations were run, focusing on both crack initiation point and corresponding propagation direction. An experimental activity was recently carried on by the authors in order to verify the onset of the bending crack and its propagation path in spur gears with different geometries by an IR thermocamera [9]. In this work, an experimental analysis was performed in order to evaluate how light weight gears geometry may influence the strain field in lightweight gears.…”