Numerical Investigation into the 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 conditions. 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—that is, cylindrical on flat and flat on flat—along with different contact span widths were analyzed. In addition, the effects of different contact spans on stress distribution at the 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 agreed with experimental observations. In terms of crack propagation for different contact spans, the fretting fatigue life for a two-based cylindrical pad was shorter than that for a two-based flat pad. By increasing the contact span width for both flat and cylindrical pads, the crack propagation lifetime increased. A comparison between the experimental and numerical results demonstrated a difference of about 18% in crack propagation lifetime.