力、电作用下沿晶微裂纹系统演化的仿真分析

Simulation and Analysis of the Evolution of Transgranular Microcracks System Induced by Stress and Electric Field

基于表面扩散的经典理论及其弱解描述,对应力迁移、电迁移诱发表面扩散下金属材料内部沿晶微裂纹的演化进行了有限元分析。详细讨论了沿晶微裂纹初始形态、电场和应力大小对沿晶微裂纹演化的影响。仿真结果表明:对于形态比为β的沿晶微裂纹,存在一临界电场值χc。当χ<χc时,微裂纹逐渐圆柱化;当χ>χc时,微裂纹分节为左右两个小裂纹。随β的增大,χc值逐渐减小。应力场的存在将导致微裂纹整体漂移速度减慢,减缓微裂纹的圆柱化;并加快裂腔分节,且使右端分节出的较小裂纹更加狭长。导体宽度越窄,γb/γs(晶界能/表面能)的值越大,微裂纹的分节时间越短。

Based on the classical theory of surface diffusion and its weak statement, a finite element analysis of the evolution of transgranular microcracks in metal materials due to stress-and electro- migration induced surface diffusion is conducted. The effects of the aspect ratio, the magnitude of the stress and the electric field on the evolution of transgranular microcracks are investigated in detail. The results of simulation show that there exists a critical value of electric filed χe for a given aspect ratio ft. When χ〈χc, the microcrack will evolve into a cylinder directly. When χ〉χc, the microcrack will be divided into two right-and-left microcracks. Asβ increases,χc decreases. The exits of stress field can slow down the drift speed of microcrack and delay the microcrack envolving into a cylinder. Besides, the stress field can accelerate the splitting speed of microcrack, and the smaller microcrack on the right sides will be more long and narrow. The narrower of the width of the conductor or the higher of the value of γb/γs, the shorter of he splitting time of the microcrack will be.