Molecular dynamics simulation of stress distribution and microstructure evolution ahead of a growing crack in single crystal nickel

摘要

The microstructure evolution and stress distribution characteristics of a pre-cracked single crystal nickel at different temperatures are studied by molecular dynamics (MD) simulation. The simulation results indicate that the crack propagation process and stress distribution characteristics are closely related to the change of temperature inducing the microstructure evolution ahead of a growing crack in single crystal nickel. At 0. K, the crack propagates rapidly without inducing microstructure evolution, the stress concentration is always at the crack tip of a growing crack throughout the crack propagation process. The crack propagation becomes slow and accompanies with microstructure evolution at elevated temperature, firstly crack tip blunting occurs at a certain distance ahead of crack tip due to the dislocation emission, then void nucleation and growth as well as the generation of slip bands. The microstructure evolution ahead of crack tip induces the change of stress distribution, the high stress value occurs at the site of the microstructure evolution (dislocation emission, void nucleation and the generation of slip bands), and a rather large plastic deformation range ahead of crack tip is necessary for the generation of slip bands. The failure process of single crystal nickel show the different crack propagation dynamics and plastic behavior, which are linked to the void nucleation and generation of slip bands ahead of the crack tip at elevated temperature.