面心立方铝剪切变形的准连续介质模拟

QUASICONTINUUM SIMULATION ON THE PLASTIC DEFORMATION IN FCC AL

采用准连续介质多尺度方法模拟了纳米尺度单晶铝的剪切变形.分别采用三种不同晶体取向(分别为x[1-10],y[001],z[-1-10];x[-1-12],y[111],z[-110];x[-110],y[-1-12],z[111])和三种不同长宽比的几何模型(分别为1∶1,2∶1,4∶1)进行模拟,得出各模型应力-应变响应曲线.加载过程中,对晶体内部变形比较剧烈的部分画出原子图,并从微观角度分析了产生剧烈变形的原因;讨论了三种晶体取向下的尺寸效应:单晶铝的剪切屈服应力随模型几何尺寸的增加而降低,并且随晶体取向的不同变化很大.最后,使用指数法则来描述模型的尺寸效应,提出了针对不同取向的指数法则参数,表明了晶体不同取向对剪切屈服应力的大小有影响.

The quasi-continuum multi-scale method is used to simulate the processes of the simple shear deformation in FCC A1. In the computation, we have used three different orientations of the metals,i. e. ,（x[1-10],y[001],z[-1-10];x[-1～12],y[111],z[-110];x[-110],y[-1-12],z[111]）, and three different specimen sizes for each orientation,i, e. , 1 ： 1,2 ： 1 and 4 ： 1. The schematic variations of the shear stress versus the shear strain in the specimens are obtained. The dislocation nucleation events are observed in the simulation from the atomistic profiles,and the mechanisms of the dislocation nucleation are analyzed. The size effects of the three crystal orientations are discussed in detail,and it is found that. the yield stress is very different for different orientation,which decreases with increasing specimen size. Finally,according to the results of the simulations and the power law, a few parameters have been put forward for different orientations to find the effects of the orientations on the critical stress.