Estimation of fretting fatigue lifetime in heterogeneous material based on microstructure characterization and multi-scale homogenization

Abstract

Fretting fatigue is a complex phenomenon that is affected by multiaxial stress and contact problems. In the contact surface, due to the cyclic load, a relatively small displacement is generated, and the stress concentration is established as well. To assess the fretting fatigue endurance complimentary to experimental efforts, the Finite Element Method (FEM) has become a useful tool combined with theoretical approaches. Meanwhile, most (if not all) of commercially available structural materials can be regarded as heterogeneous materials due to the existence of secondary phases and some fabrication defects and porosity. Therefore, to further understand the mechanism of fretting fatigue, knowledge of the material’s microstructure is important. In this study, several microstructure characterization techniques are applied to characterize precipitates and micro-voids in aluminium alloy AA2024-T3. These techniques are Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS). To account for the precipitates, the homogenization method is adopted in this study. Additionally, a 3D structure non-destructive reconstruction technique is applied to obtain accurate information on micro-voids. The fretting fatigue lifetime is estimated by using the critical plane approach combined with the theory of critical distance. The numerical results are compared with experimental data showing a good agreement. The influence of micro-voids on the fretting fatigue endurance is studied and discussed as well.