纳米压痕过程的多尺度模拟与Rice-Thomson位错模型分析

Multiscale Simulation and Rice-Thomson Dislocation Model Analysis of Nanoindentation

采用多尺度准连续介质法(简称QC方法)对单晶Ag薄膜纳米压痕过程进行模拟,研究压头宽度对纳米压痕过程中接触应力分布、位错形核临界载荷以及纳米硬度的影响,并用Rice-Thomson位错模型(简称R-T位错模型)进行分析。结果表明,纳米压痕获得的载荷-位移曲线呈现出的不连续性与位错之间的协同作用密切相关;压头尺寸对纳米压痕过程中接触应力分布、位错形核临界载荷以及纳米硬度具有明显的影响:随着压头宽度的增加,法向和切向接触应力以及纳米硬度值递减,呈现出明显的压头尺寸效应;而压头下方薄膜内位错形核临界载荷却递增,且与压头半宽度的平方根成正比。模拟结果与相应实验结果以及R-T位错模型计算结果吻合。

The nanoindentation in single crystal Ag thin film was simulated by a multiscale quasicontinuum (QC) method. The influences of the indenter width on the contact stress distribution, the load necessary for first dislocation emission and the nanohardness were investigated in the nanoindentation deformation process. In addition, all results of the simulation were analyzed with Rice-Thomson (R-T) dislocation model. Results show that the sharp drops of the load-displacement curves are due to the collective dislocation activities. The indenter width can greatly influence the contact stress distribution, the load necessary for first dislocation emission and the nanohardness. Normal contact stress, shear contact stress and nanohardness are decreased as the indenter width is increased, indication an obvious indenter size effect in nanoindentation of single crystal Ag thin film; whereas the load necessary for first dislocation emission is increased as the indenter width is increased, an is in direct proportion to the square root of the indenter half-width. The simulation results are in good agreement with experimental results and R-T dislocation model.