复合型裂纹扩展的形状改变比能准则

为了预测金属材料裂纹在小范围屈服时的延性断裂，以复合型裂纹为研究对象，将裂纹前缘塑性屈服区内的总形状改变比能用于建立复合型裂纹的断裂准则。该准则表明了金属材料裂纹在扩展过程中，起决定作用的是形状改变比能，而不是整个应变能。能成功地预测了复合型裂纹的启裂角度以及临界荷载，将其结果与Sih的S准则和实验数据结果进行了比较。结果表明，复合型裂纹扩展的形状改变比能准则，在预测裂纹启裂角方面优于S准则，并且预测的临界荷载偏保守。在工程上，将其应用于复合型裂纹断裂判定是安全的。

Distortion Energy Criterion for Mixed Mode Crack Propagation

In order to predict the ductile fracture of metallic materials crack under the small-scale yielding situation, the mixed-mode crack was considered as research object.The sum of the distortion energy in the plastic zone of the crack tip can be used to construct a fracture criterion of mixed-mode crack propagation. The criterion showes that the distortion energy plays a major role during the crack propagation in metallic materials, while the whole strain energy does not. It predicts successfully crack initiation angle and critical load for several mixed-mode crack problems. Compared will Sih's S-criterion and experimental data, the results gained by present approach match well with experimental data and superior to S-criterion in predicting crack initiation angles, meanwhile, the critical load from the present approach is more conservative in engineering problems.