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.