晶体位错尺寸效应的多尺度分析

Multiscale Analysis of Size Effect in Crystalline Solid Dislocation

本文采用准连续介质多尺度方法,分析了面心立方(fcc)晶体铝阶梯孪晶界在不同尺寸情况下(试件尺寸长高比从1∶1到8∶1)受剪切作用的晶界变形。了解在不同尺寸下,晶界结构位错的成核过程,得到了大试件比值与小试件比值下作用力与应变的关系曲线及不同试件尺寸下应变能的变化曲线。其中随着试件比值的增加,作用力在应变比较小的时候变化情况相似,但当应变达到3%以后,呈现出明显的不同;应变能随试件长高比的增大而减小,各个试件在各自不同的加载阶段,应变能变化趋势同作用力变化趋势相一致。本计算揭示了不同尺寸下阶梯孪晶界在剪切作用下的微观机理,证实其尺寸效应性质。

The quasi-continuum method is used to analyze the action of two fcc AI crystals with a stepped twin boundary in a specimen under uniform shear strain. The length height ratio of the specimen is chosen from 1 ： 1 to 8 ： 1 to find the size effect. The progress of the nucleation of partial dislocations was examined, and the schematic variations of the applied force and the strain energy with shear strain in the specimens with different aspect ratio were obtained. The results show that the applied forces of all four specimens have a similar variety as the strain of specimens is small, but the forces are applied differently after the strain arrived at 3%. The strain energy will decrease with the increase of specimen＇s aspect ratio, and the variations of strain energy consist with the variations of applied forces at different load step. The calculation elucidate the plausible microscopic mechanisms for the nucleation of dislocations under shear and the size effect is in evidence.