In this paper, the effect of explosive treatment on the behaviour of fatigue crack propagation in the welded joint was investigated. Using the stress releasing method, the author has measured the redistribution of residual stress after the crack was initiated from the regions of variant stress condition (without external working load). The results present that the redistribution of residual stress is mainly related to the stress condition of initial crack end. In the second part of this paper, the rule of (CTOD)r and (ICTCD)r changed with the crack propagation was measured. The results show that (CTOD)r and (ICTCD)r first ascend to the pick value and then descent with crack propagation, but their sign is unchanged. In terms of facts above, the superposition model of crack tip displacement was proposed to explain the effect of residual stress on FCP rate. This part presents that the Paris power is related to the change of (CTOD)r and (ICTCD)r. At last, the behaviour of FCP in the explosive region was investigated, and that the change of microstructure can decrease FCP rate was concluded.
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