Abstract: In this paper, the interaction among multiple cracks propagation in some complex engineering structures with multi load-path is studied by varying the local flexibility. A method to calculate the variation of local flexibility and to make a sequence of reanalyzing of stress distribution during crack propagation is provided, and a special designing fatigue experiment using a two hole plate specimen with four hole-edge cracks is carried out. The experimental and calculating results are in good agreement, and some useful conclusions about the interaction among multiple cracks propagation are obtained through this special experiment. Finally, this method is used to predict the total life of a complex joint with multi-fastener and multi-layer. The comparison between predicting and experimental results shows further that this method is suitable for engineering practice.

Key words: complex structure, multiple cracks, total life, crying the local flexibility