Numerical study of implosion of shell structures

Abstract

To better understand the implosion and the resultant shock wave, a series of numerical modeling and simulations were undertaken for the buckling and collapse of spherical and cylindrical shell structures. The shells were assumed to be made of steel, aluminum, and laminated fibrous composites, respectively. First, the buckling was examined for the shell structures subjected to external pressure loading without any contact with fluid media. Both static and dynamic buckling was studied. For the dynamic buckling, the speed of collapse was controlled to investigate its effect on the buckling characteristics such as buckling mode. This was achieved by decreasing the internal pressure at different rates as the structures were subjected to a constant external pressure. Then, the full implosion process associated with the collapse of shell structures was modelled and studied to understand the shock wave propagation radiated from the collapsing shell structures. The structures were initially subjected to an external water pressure equivalent to a specified water depth. Then, the collapse speed of the shells was controlled, too. Finally, the effect of an initial defect on the buckling and implosion of cylindrical shells was examined. The numerical study compared the implosion characteristics resulting from spherical and cylindrical shells, different material properties, and various controlled collapse speeds. The results suggested that there were optimal parameters which generate the maximum peak pressure during the implosion process.