A model to predict initiation and propagation of micro-pitting on tooth flanks of spur gears

Micro-pitting is an early-stage failure mode commonly found in gears. It leads to macro-pitting, spalling, and even tooth fracture failure, which cause destructive damage to gearboxes. A simulation model to predict the initiation and propagation of micro-pitting on tooth flanks of spur gears is presented. The model simulates the actual gear meshing process, considering the time-varying tooth profile. The contact pressure distribution, sliding velocities, rolling velocities, film thicknesses, and shear stresses along the contact line are accurately calculated. A new crack criterion is proposed to predict the initial crack position. A novel wear rate model was developed by considering the influence of crack density to predict the propagation of micro-pitting and the removal of material from the tooth flank. The results of experiments carried out for gear pairs with different tooth tip reliefs and surface roughness showed good agreement with the simulation results. This verified the model validity.