镍单晶薄膜纳米压痕的准连续介质模拟

QUASICONTINUUM SIMULATION OF NANOINDENTION OF NICKEL FILM

用准连续介质方法模拟了大规模原子的镍薄膜在纳米压痕下发生初始塑性变形的行为.主要得到了:(1)载荷-位移响应.在载荷位移曲线上除了反应晶体弹性性质的直线外还有数次的载荷突然下降过程.(2)位错形核现象.与载荷-位移曲线上的载荷突然下降相对应的在受压的晶体上发现了位错形核现象,说明载荷的下降是因为位错形核引起的.(3)位错的发射机制.用Peierls-Nabarro位错模型以及能量法分析了位错的发射机制,理论值与计算值吻合较好.(4)几何必需位错密度.用一个简单的模型计算了几何必须位错密度.此外还考虑了边界条件对模拟结果的影响.

A large-scale atom simulation of nanoindentation into a thin nickel film using the quasicontinuum method was performed. The initial stages of the plastic deformation of nickel were studied. Several useful results were obtained. （1） The response of the load versus indentation depth. On the load versus indentation depth curve, besides the straight parts corresponding with the elastic property of nickel, the sudden drop of the load occurred several times. （2） The phenomena of dislocation nucleation. The dislocation nucleation appeared when the load descended. This makes it clear that dislocation nucleation leads to the drop of the load. （3） The mechanism of the dislocation emission. The Peierls-Nabarro dislocation model and an energetic criterion were used to analyze the dislocation emission. And the computational value was in good agreement with the predict value. （4） The density of geometrically necessary dislocations. A simple model was used to obtain the density of geometrically necessary dislocations beneath the indenter. Furthermore, the influence of the boundary conditions on the simulation results was discussed.