A crystal plasticity model for sliding frictional thermal contact of gradient nanostructures

The objective of this work is to investigate the thermomechanical response of gradient nanostructures (GNS) under sliding frictional contact using a crystal plasticity model incorporating dislocation density evolution. The variation in grain size along the depth direction of GNS is considered, and its effect on the mechanical response is assessed. The influence of frictional heat-induced temperature rise on the dislocation density and critical resolved shear stress is included in the formulation. A homogenization approach is adopted to link the microscale characteristics of the structure to the macroscopic response during contact. Material parameters are calibrated using uniaxial tensile and nanoindentation experimental data. Comparative simulations are performed for homogeneous grain structures (HGS) and GNS, and the influences of grain size gradient, heat generation, gradient form, and friction coefficient on the thermomechanical fields are analyzed. The results indicate that GNS exhibit lower contact tensile stress, reduced plastic strain accumulation, and a slower rate of dislocation density evolution compared to HGS. These findings support the effectiveness of GNS in enhancing surface performance and mitigating contact-induced damage.