内压对多场诱发表面扩散下微裂纹演化的影响

根据表面扩散控制下物质迁移机制，建立力、电、热和内压共同作用下的有限单元法，详细讨论了多场诱发表面扩散下金属材料内部微裂纹的演化过程。结果表明：对于形态比为 的微裂纹，存在一临界电场值 。当 时，微裂纹逐渐圆柱化；当 时，微裂纹分节为上下或左右两个较小的微裂纹。随着内压的增大，微裂纹圆柱化时间增长，而分节时间显著减小，且内压有助于微裂纹分节。对于 的微裂纹，当 、 和 一定时存在一临界内压值 。当 时，随着电场和内压的增大会率先在裂纹的上下两端发生裂纹扩展。对于 的微裂纹，当 MPa时，内压对临界值 的影响较小。

The effects of the internal pressure on the evolution of microcracks by multi-physical fields induced surface diffusion

Based on the theory of surface diffusion, a finite element method is developed to simulate shape evolutions of intragranular microcracks in metal materials due to internal pressure, stress field, electric field and thermal gradient induced surface diffusion. The results show that there is a critical value for a given aspect ratio . When , the microcrack will evolve into a cylinder directly. When , the microcrack will be divided into two right-and-left or lower-and-upper microcracks. The cylinderization time of the microcrack increases with the internal pressure increasing, while the splitting time decreases. Besides, the internal pressure is conducive to the microcrack splitting. There is a critical value of pressure for when , and are given. If , the microcrack propagation firstly appears at its lower-and-upper side with the increasing of and . The internal pressure has little influence on critical value when MPa.