Crack nucleation threshold under fretting loading by a thermal method

• Experimental setup combining an IR camera and a markers tracking method is proposed.
• Temperature evolution of a specimen can be decomposed into several harmonics.
• To separately analyze each harmonics a method of sliding–smoothing is applied.
• A thermal method to determine crack initiation thresholds is developed.
• Differences between thermal method and the destructive one are less than 10%.

The aim of this study is to develop a new, non-destructive, experimental method, based on the thermal response of materials, to determine crack nucleation threshold during a fretting test in a cylinder on flat contact configuration. The temperature evolution during a fretting test with constant loading showed that the latter can be decomposed into three parts: an overall thermal drift and two periodic signals at fL and 2fL; where fL is the loading frequency. The results showed that the stabilized value of the drift and the periodic signals' amplitudes can be empirically related to the crack nucleation threshold; with result differences of less than 10% from those determined by destructive methods.