Numerical investigation into effect of contact geometry on fretting fatigue crack propagation lifetime

Fretting fatigue is a phenomenon, in which two contact surfaces undergo a small relative oscillatory motion due to cyclic loading. There is a need to analyze the effects of contact geometry on crack propagation under fretting fatigue condition. In this investigation, a finite element modeling method was used to study the effects of different contact geometries along with crack-contact interaction on crack propagation lifetime. Different contacts geometries, i.e. cylindrical on flat and flat on flat along with different contact-span width were analyzed. Also effects of different contact-span on stress distribution at contact interface were investigated. The computed crack propagation life was compared with experimental results. It was found that the crack initiated near the contact trailing edge for all contact geometries, which completely matches with experimental observations. In terms of crack propagation for different contact-spans, it was realized that fretting fatigue life for two based cylindrical pad was shorter than that for two-based flat pad. Also by increasing contact-span width for both flat and cylindrical pads, crack propagation lifetime increases. A comparison between the experimental and numerical results demonstrates a difference of about 18% in crack propagation lifetime