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在载荷作用下,位错一个个地从模式Ⅱ或模式Ⅲ的裂纹尖端放出。放射过程发生在局部应力强度因子达到临界值时,放射出来的位错以一定速度离开,运动速度与大于晶格摩擦力的有效剪应力的三次方成正比。本研究发现饱和所需的时间与晶格摩擦力的关系至大,与施加应力关系较小,几乎与放射位错的临界应力强度因子无关。无位错区的大小随着位错放出数目增加而加大,大的临界应力强度因子其值也大,但与晶格摩擦力的大小没什么影响。卸载时,某些位错回至裂纹内而消失,此时无位错区的大小依卸除的载荷而增加。位错的动态分布与静态分布不同,仅仅在饱和时二者才接近一致。
Under load, dislocations are released one by one from the crack tip of mode II or mode III. The radiation process occurs when the local stress intensity factor reaches a critical value, and the dislocations that are emitted leave at a certain speed, and the speed is proportional to the cubic power of the effective shear stress greater than the lattice friction force. This study found that the relationship between the time required for saturation and the lattice friction force is large, and the relationship with the applied stress is small, and it is almost independent of the critical stress intensity factor of the radial dislocation. The size of the dislocation-free zone increases as the number of dislocations increases, and the large critical stress intensity factor also has a large value, but it has no effect on the size of the lattice friction force. During unloading, some of the dislocations disappear back into the crack and disappear, and the size of the dislocation-free zone increases with the unloaded load. The dynamic distribution of dislocations is different from the static distribution, and they are only close to the same when they are saturated.