Indentation behavior of polycrystalline copper under fatigue-peak overloading

The indentation behavior of polycrystalline copper at room temperature was investigated with a flat cylindrical indenter applied to fatigue-peak overloading. The experimental results showed that fatigue-peak overloading can retard the indentation depth (d) propagation rate. After the period of overloading, the d propagation rate arrived at a new steady-state value again. The greater the amplitude of the peak overloading, the more the number of cycles that were needed to remove the effect of overloading. The observations of indentation cross-sectional microstructures revealed that the mechanism of d propagation was the nucleation, formation, and propagation of cracks around the indentation. The experimental results and their interpretation implied that there were some similarities between the indentation fatigue-depth propagation and the conventional fatigue-crack propagation under fatigue-peak overloading.