An analytical life prediction model for the crack propagation occurring in contact fatigue failure

This analysis develops a three-dimensional analytical model for the crack propagation phase of the surface pitting failure process. An initiated pre-pitting crack is simulated as a semi-circular inclined planar surface crack in a half-space. The cyclic contact fatigue loading is approximated by a repetitious Hertzian line loading moving quasi-statically across the half-space surface with both normal and shear components. Three-dimensional fracture mechanics is utilized to determine the three modes of stress intensity factors around the crack front. A mixed mode fatigue crack growth law is employed to estimate both crack growth geometry and crack propagation life. Numerical results are presented for a 45 degree inclined crack and for the 20 to 30 degree shallow crack angle which is experimentally observed. Life estimates from the present calculations are in line with previous experimental measurements.