A fracture mechanics model for the wear of gear flanks by pitting

A new model for determination the pitting resistance of gear teeth flanks is presented. The theory of short cracks is utilised for computational simulation of the fatigue process leading to pitting. The stress field in the contact area of meshing spur gears and functional relationship between the stress intensity factor and the crack length are determined by the finite element method using an equivalent model of two cylinders. The equivalent cylinders have the same radii as the curvature radii of gear teeth flanks in the inner point of a single teeth pair engagement, which represents the worst loading case. Based on computational results and with consideration of some particular material parameters the service life of gear flanks can then be determined from a number of stress cycles required for crack propagation from the initial to the critical crack length, when surface pitting can be expected. The model is applied to a real spur gear pair, which is also experimentally tested. The comparison of numerical and experimental results shows a good agreement. Further theoretical and experimental investigations are necessary to develop a reliable method for the estimation of gear life with a fracture mechanic model. (C) Elsevier Science S.A.