应力诱发表面扩散下晶内微裂纹演化的有限元分析

A finite element analysis of the evolution of intragranular microcracks due to surface diffusion induced by stress migration

基于物质表面扩散和蒸发-凝结的经典理论,对金属材料内部晶内微裂纹在应力诱发下不稳定外形演化进行了有限元模拟。结果表明,在拉压载荷下,椭圆形晶内微裂纹演化分叉存在临界形态比βc,当β<βc时,微裂纹逐渐圆柱化;当β≥βc时,微裂纹分节为三个裂腔。微裂纹分节时间随形态比增大成近似线性减小,随着拉压应力的增大,微裂纹发生分节的临界形态比和分节时间都将减小。

Based on the classical theory of surface diffusion and evaporation-condensation,a finite element program is developed for simulating the shape instability of intragranular microcracks due to surface dif- fusion induced by stress migration. The results show that there exists a critical value of aspect ratio βc for the intragranular microcracks under the compressive and tensile stress. When β〈βc, the microcrack will directly evolve into a cylinder. When β≥βc,it will split into three small microcracks. The splitting time of microcrack decreases linearly with the aspect ratio increasing. As the stress increases, both the critical value of aspect ratio and the splitting time increase continuously.