Dynamic response characteristics of metal cylindrical shell driven by explosive charge with waveform regulator

Abstract

Waveform regulator in charge is a method that can realize multi-source detonation wave superposition through a single point detonation. The method does not need to weaken the strength of shell, and relies on the high stress generated by superposition to cut shell into regular fragments. Additionally, it can be combined with different initiation methods to alter the fragmentation outcomes. In this study, aiming at the fracture strain of metal cylindrical shell driven by explosive charge with waveform regulator, theoretical analysis was first adopted to obtain the prediction model of the fracture strain of cylindrical shell with waveform regulator and the model of the axial distribution of the stress concentration factor. On this basis, both theoretical analysis and numerical models were utilized to investigate the effect of waveform regulator on the initial velocity of fragments. Finally, experiments were conducted to validate the fracture strain prediction model for cylindrical shell with waveform regulator. The research results show that the collision angles of the detonation waves at different axial positions are different, which leads to the stress concentration factor on the shell presenting a trend of gradually decreasing, then sharply increasing, and then rapidly decreasing along the axial direction. Additionally, the changes in the slot spacing and the thickness of outer charge will also affect the stress concentration factor, and the influence of outer charge thickness is relatively large. The smaller the ratio of charge volume to waveform regulator volume, the larger the axial sparse wave intensity and the more the fragment initial velocity decrease. From the initiation end to the non-initiation end, the failure modes of the shell sequentially change from pure shear, to mixed tensile-shear, and finally to pure tensile failure. The experimental results are in good agreement with the calculated results of the fracture strain model, and the maximum relative error is less than 10%, which indicates that the fracture strain prediction model of the cylindrical shell with waveform regulator established in this paper by considering the increase of elastic energy per unit volume caused by stress concentration on the shell is reliable.