NUMERICAL-ANALYSIS OF SUBSURFACE CRACK FAILURE BENEATH THE PITCH LINE OF A GEAR TOOTH DURING ENGAGEMENT

This study focuses on the behaviour of subsurface cracks beneath gear teeth with a view to developing a fundamental understanding of the mechanisms of pitting/spalling fatigue. To this end a number of two-dimensional small cracks, parallel to the tangent plane, beneath the pitch line of a gear tooth were modelled using the finite element method. potential modes of crack propagation and failure were then analyzed. As a result of this analysis it was found that the values of the stress intensity factors (SIFs) of the subsurface crack(s) were beneath the critical STF, K-c. Consequently, it was hypothesised that final failure is owing to ligament collapse rather than by brittle fracture. The possible separation of the plane of the crack to form a ''pit'' or ''spall'' is also discussed and the numerical results compared with experimental values.