To reveal the enhanced initiation effect and mechanism of covered explosive by multi-fragment coupled impact, based on the shock initiation and detonation of heterogeneous explosives, a theoretical model of impacting covered explosive with one single fragment, double fragments simultaneously and double fragments simultaneously and sequentially was established. Combined with finite element modelling, effect of fragment number, fragment space and impact sequence were analyzed. The shock wave interaction principle and enhanced effect under double fragments simultaneously and sequentially impacting covered explosive were obtained and the mechanism was revealed. The results show that threshold velocity of covered explosive decreases with the increase of fragment number.
With the increase of fragment space, the degree of superposition of shock wave decreases, and threshold velocity increases and approaches the threshold velocity of single fragment. Initial detonation wave deviates from the position of the central axis when the sequence of the fragments impacting covered explosive is different. This deviation is caused by the different states of the medium before and after the shock wave in explosive.