Influence of inclusion interfaces on surface pitting
A new model is described for the simulation of the surface fatigue process in the contact area of spur gears. The model considers the conditions required for subsurface fatigue crack initiation and allows for proper simulation of fatigue crack propagation under contact loading. The theory of dislocation motion along inclusion interfaces is studied in some detail and is used to describe the process of fatigue crack initiation, where the microstructure of a material plays a crucial role. The theory of short crack growth is then used for the simulation of the fatigue crack growth. The stress field in the contact area and the functional relationship between the stress intensity factor and crack length are determined by the finite element method. The 2-dimensional equivalent model of two cylinders is used in the numerical simulations of crack initiation and crack propagation in the contact area, which reduces the required computation time significantly. On the basis of computational results, and with consideration of some particular material parameters, the service life of gear teeth with regard to pitting is estimated. The model developed is applied to a real spur gear pair, which also is tested experimentally. A comparison of numerical and experimental results reveals good agreement, and it may be concluded that the model developed is appropriate for determining the pitting resistance of gear teeth.