Prediction of fretting crack propagation based on a short crack methodology

Fretting tests have been conducted to determine the maximum crack extension under partial slip conditions, as a function of the applied tangential force amplitude. An analytical elastic model representing a fretting-induced slant crack has been implemented and combined with the Kitagawa-Takahashi short crack methodology. This approach provides reasonable qualitative agreement between experimental and predicted maximum fretting crack lengths as long as the global response of the interface remains elastic. It confirms the stability of the crack arrest approach to predict the fretting fatigue endurance. It is, however, observed that the model is systematically conservative when significant plastic deformations are generated in the interface. A discussion of the appropriate fundamental parameters when dealing with steep stress gradients such as those present in fretting, and which are difficult to interpret in the context of the Kitagawa-Takahashi method, is presented. It is also shown that the maximum crack length evolution under plain fretting wear test conditions can be used to calibrate fretting fatigue predictions.