Dynamic implosion of submerged cylindrical shell under the combined hydrostatic and shock loading

Thin-walled cylindrical shells are commonly used in designing underwater structures. When subjected to the combination of hydrostatic pressure and underwater explosive loading, these cylindrical shells are prone to implosion failure. In this work the dynamic stability of submerged cylindrical shells subjected to underwater explosion was investigated through both numerical simulations and theoretical modeling. In particular, the effects of initial hydrostatic pressure and fluid–structure interaction on the dynamic stability of metallic cylindrical shells are revealed. The transient responses of cylindrical shells have been simulated using Abaqus/Explicit with the water domain discreted by acoustic elements. The simulation results show that the existence of initial hydrostatic pressure reduces the structure stiffness, and the structural response to the pressure wave loading primarily consists of initial axisymmetric vibrations and subsequent mode 2vibrations. There exists one critical threshold value for the initial hydrostatic pressure, below which these vibrations are stable and above which these vibration will trigger the implosion of the cylindrical shells. These threshold values are obtained via both numerical simulations and theoretical modeling. The analytic model considering the added mass effect of surrounding water and the effect of initial stress of the shell due to hydrostatic pressure shows good accuracy comparing with the numerical and experimental results. The dependence of the dynamic buckling strength of the metallic cylindrical shells on the material choice for either constant static buckling strength or constant weight is then discussed.