Ⅰ-Ⅱ复合型裂纹脆性断裂的最小J_2准则

实际工程的结构中,裂纹多处于复合型状态,因此复合型裂纹断裂的理论研究有着更为重要的理论意义和实用价值。本文以Ⅰ-Ⅱ复合型裂纹为研究对象,将偏应力张量的第二不变量2J作为判定依据,预测了裂纹起裂的角度以及开裂荷载,并与一些实验数据进行了比较,符合得也较好。计算结果进一步表明了在裂纹起裂引起的应变能转化过程中,起主要作用的是形状改变比能这一事实,由此得出了另一个结论是在裂纹尖端,平行于裂纹方向的应力级数展开式中非奇异项对裂纹的开裂角度以及开裂荷载是有影响的。

THE MINIMUM J2 CRITERION FOR I-II MIXED MODE BRITTLE FRACTURE

In practical engineering, mixed-mode fractures of material are commonplace. So the analysis of mixed-mode crack is of both theoretical importance and practical value. J2, the second invariant of stress deviator tensor, is considered here to predict the I-II mode crack initiation angle and critical load. The results are in good agreement with experimental data, which confirms the fact that the distortion energy plays a major role during the strain energy transformation caused by crack initiation. It is also found that the non-singular term in the series expansion of the stress parallel to the crack around the crack tip, has an effect on the crack initiation angle and the critical load.