Subcritical implosion of fully confined metallic shells subjected to external stimuli

The dynamically initiated subcritical collapse of a cylindrical shell confined within an acrylic pressure vessel was experimentally investigated, where the transient load was provided by an underwater explosive charge placed exterior to the vessel. Analytical expressions for the transmissivity of the vessel to traveling waves were compared to recorded dynamic pressure histories and showed favorable agreement for a rigid, classically acoustically transparent case. An analytical approach for estimation of the threshold subcritical hydrostatic pressure at which dynamic collapse initiation occurs was developed using the solution of a coupled system of radial equations of motion and the shell’s radial imperfection sensitivity to hydrostatic collapse. Radial flexural vibrations excited by the dynamic load may be thought of as an additional imperfection which may lead to subcritical collapse as a function of the shell’s imperfection sensitivity. For the cases experimentally investigated, this approach showed good agreement, with trials just under the threshold pressure surviving the initial shock loading and trials just above the threshold pressure collapsing readily upon impingement of the load.