裂纹尖端塑性区和无位错区的微观模拟

MICRO-SIMULATION OF CRACK TIP PLASTIC ZONE AND DISLOCATION-FREE ZONE

用细观断裂力学研究了刃型位错从Ⅰ型、Ⅱ型及Ⅰ+Ⅱ复合型裂纹尖端沿多个滑移面的发射以及裂纹周围无位错区和塑性区的形状和大小,结果表明,Ⅱ型裂纹塑性区形状和宏观断裂力学算出的塑性区形状有所不同,而Ⅰ型裂纹塑性区形状则类似;当外载荷相同时,Ⅱ型裂纹的塑性区比Ⅰ型裂纹的塑性区要大得多;复合型裂纹的塑性区形状和大小更接近Ⅱ型裂纹,各种裂纹尖端周围均存在无位错区,其形状与相应的塑性区相似。

Edge dislocation emissions from Mode 1, Mode 11 and mixed-mode crack tips along multiple inclined slip planes are simulated, and plastic zones as well as dislocation-free zones are obtained. It is found that the shape of the Mode 11 plastic zone is quite different from that obtained based on von Mises yielding criterion and consists of three parts in which the biggest one locates in front of the crack tip. For Mode I crack, however, a similar plastic zone is obtained. Under the same magnitudes of applied stress, the plastic zone of Mode 11 crack is much larger than that of Mode I crack, and the plastic zone of a, mixed-mode crack is mainly affected by the Mode 11 component. Dislocation-free zones exist around all types of crack tips, which have similar shapes as the corresponding plastic zones.