Fretting occurs when two contacting bodies experience oscillating shear tractions and small relative slip amplitudes. Wear is the progressive loss of material from the surface of a solid body when in contact with another body.​ Wear affects fretting fatigue, and accurate modeling of wear is required to acccurately predict fretting fatigue life. The evolving interface geometry due to wear affects the stress-strain distribution locally. Material wear smoothens the interface and enhances life span of the mating components [1].

For most practical problems, fretting fatigue happens over millions of cycles. To accurately predict life span accounting for wear, a simulation must include at least hundreds of cycles since the effect of wear in each cycle is quite small. The stress-strain history calculated over a few hundred cycles including the effect of wear can be used to predict the fretting fatigue life. This poses a challenge as simulating so many cycles is computationally prohibitive. Automatic wear scaling is used to solve this problem. Auto-scaling of the wear increment speeds up wear simulation by assuming that the wear rate over a certain physical time interval is constant. The overall simulation time for calculating the physical life span speeds up as well. A finite element (FE) model is solved for a few simulation cycles, each of which represents hundreds of physical cycles. For each simulation cycle, the number of repeats can be calculated by comparing the physical and simulation time period of the cycle. The linear/nonlinear cumulative damage law can be used to calculate damage for simulation cycles.

Postprocessing of the fretting fatigue life calculation with wear uses nCode DesignLife. For the load mapping, a Duty cycle load provider with a Time Step loading event is chosen which requires the load history of each simulation cycle. The number of repeat counts is calculated as the ratio of the physical and simulation time period that corresponds to each simulation cycle. Independent Event processing is chosen for the cumulative damage calculation, where sequence of loading is not important. The loading sequence is captured in the FE analysis. The fretting wear damage is calculated using Signed Shear criterion with the Smith-Watson-Topper (SWT) mean stress correction. The model is validated by comparison with experimental results from the literature [2]. The effect of wear on the fretting fatigue life captures the experimentally observed trend.