The effect of surface roughness and microstructure on fretting fatigue properties of TC21 based on hierarchical multiscale modeling

In the aviation industry, structures made from high-strength titanium alloy TC21 frequently suffer from fretting fatigue (FF), resulting in shortened service life. FF is significantly influenced by the surface integrity (SI) parameters. This study aims to investigate the effect of SI parameters, including microstructure and surface roughness, on the FF properties of TC21. It is implemented by introducing the crystal plasticity finite element method (CPFEM). The CPFEM parameters of single grain of α-Ti in TC21 were obtained by fitting the experimental and simulation data of nanoindentation test. On this basis, the FF of TC21 is studied by means of multiscale modeling method, which couples a global model with a CPFEM sub-model composed of hierarchical microstructure. In the global model, surface roughness was considered. While in the CPFEM sub-model, microstructure was incorporated as well. The FF sub-model shows that the stress was unevenly distributed due to the inconsistency in mechanical behavior of TC21. Both the maximum von Mises stress and the maximum Fatemi-Socie (FS) parameter occurred at the grain boundaries in the subsurface layer. The prismatic slip system (1‾010)[1‾21‾0] is highly sensitive to FF. For the orientation of <100>∥X-axis, the lowest FS value of 1.137 × e⁻² was obtained at the surface roughness of 0.8 μm, meaning the smallest damage. While the orientation of <110>∥X-axis and random orientation are most sensitive to FF, their FS values reaching 2.019 × e⁻² and 2.090 × e⁻², respectively.