广布损伤的试验研究与有限元分析

 通过对无钉载3排平行孔平板和无钉载3排交错孔平板从无裂纹开始的疲劳试验，发现应力大小对是否出现广布损伤(MSD)有重要影响，首裂孔和断裂排位不总是一一对应。在试验中观察到了MSD的竞争现象，证实了群发小裂纹也是MSD中一种重要的破坏形式。采用FRANC2D/L建立了对生裂纹、非对生裂纹和单裂纹3种开裂模式的有限元模型。计算结果表明:短裂纹扩展过程中，裂纹间干涉效应不明显，3种模式的应力强度因子增长趋势相近；而对于长裂纹，试验和有限元计算都证明了裂纹间的干涉显著地加快了裂纹的扩展。

Test Research and Finite Element Analysis on Multiple Site Damage

Crack-free panels with three parallel and alternate rows of holes are tested under cyclic loads. The results show that stress level has a significant impact on the appearance of multiple site damage (MSD) and the specimens do not always fail at those rows which comprise the first broken holes. In the tests, competition of the MSD is observed, and group-occurring small cracks are also proved to be an important kind of failure mode. Three finite element cracking models are built by FRANC2D/L, including those for neighboring cracks, non-adjacent cracks and single cracks. The analysis results indicate that the interaction effect between cracks is not obvious during short crack propagation. For the three models, the increasing trends of stress intensity factors are similar; while for long cracks, both the test results and finite element analysis reveal the fact that crack interaction can significantly speed up the expansion of cracks.