Fretting fatigue predictions in a complex coupling

The fretting fatigue behaviour of a representative high-performance aero-engine spline coupling is studied under complex non-symmetrical and variable amplitude loads, consisting of major cycle torque and axial load, combined with minor cycle rotating bending moment and fluctuating torque. The objective of the study is to evaluate the effectiveness of finite element based predictions of: (i) a widely-used fretting fatigue damage parameter, namely a critical-plane Smith-Watson-Topper (SWT) parameter, and (ii) the fretting-fatigue-specific Ruiz criterion, for complex coupling geometries. The approach employs a high-resolution finite element model with localised mesh refinement to achieve detailed fretting fatigue results while maintaining an acceptable node count. The predictions are compared with corresponding laboratory test results and observations. Methods for overcoming the shortcomings of the SWT parameter, in the context of fretting fatigue, are discussed and a modified SWT parameter, which includes the effect of slip, is presented.