MOLECULAR DYNAMICS SIMULATION OF PLASTIC DEFORMATION DURING NANOINDENTATION
纳米压痕形变过程的分子动力学模拟

The plastic deformation process during nanoindentation of Ni tip into Al substrate, including loading, unloading and stress relaxation has been studied by using molecular dynamics simulation with EAM potential. Results showed that a connective neck between the indenter and the substrate will be formed when the indenter approaches and leaves the substrate surface. During nanoindentation, the first dislocation is emitted at a critical shear stress TS= 1.9 MPa, and shear bands appear at partial shear stress Td=6.4 MPa. When the indenter moves upwards, a reverse tensile stress appears and results in reverse yield of the substrate and continuous change in dislocation configuration. When the indentation tip is retracted and passed through its initial indentation position, it connects to the substrate by necking, and when the tip broke away from the substrate finally, there still exist some substrate atoms on the tip. Stress relaxation has been observed on the nanoscale, which attributes to heat activated dislocation emission and motion.