The residual strength of a ship after an internal explosion

Abstract

An internal airblast from a missile explosion produces tearing, holing and dishing of ship's structural plating. In order to analyze the residual strength of a ship after an internal explosion, a typical ship compartment was considered to be composed of flat square plates subjected to uniaxial compression, and the damage effects were examined independently. The holing was considered to be a centrally located circle. Plastic limit load analysis of a flat plate indicates that ultimate strength decreases in proportion to increasing hole size. Elastic-Plastic analysis indicates that ultimate strength is little affected by hole size until the holing reaches half the plate width, and is essentially equal to the ultimate load described by the effective width concept. An extension of the concept of small imperfections to dished plates suggests that the ultimate strength is reduced by roughly 10 percent from that of a flat plate. The extensional collapse mode analysis describes folding and strength beyond peak load. Fully plastic crack propagation was examined, but its limiting effect can not be precisely described. A small program of experimentation was developed to gain qualitative insights into the interaction and cumulative effect of the various damage modes. Seven mild steel boxes were constructed of four square side plates with length-to-thickness ratios of 90 and two stiffened end plates to model different damage effects