Numerical investigations on the large deformation behaviour of ring stiffened cylindrical shell subjected to underwater explosion

Abstract

Ring stiffened cylindrical shells find wide applications in marine vehicles such as submersibles, submarine, autonomous underwater vehicles (AUV) and torpedoes. The structures used for military applications are susceptible to shock loadings from an underwater explosion. It is imperative to understand the shock damage mechanism of such structures to design for survivability. The problem is quite complex involving explosive-fluid interaction, fluid-structure interaction, material, geometric nonlinearity and strain rate effects. In this paper, an attempt has been made to study the shock response of a ring stiffened cylindrical shell of length 1000 mm, diameter 600 mm and thickness 6 mm shock tested using small explosive charge of 70 gm PEK I. The numerical study is performed using LS-DYNA finite element code considering the fluid-structure interaction, strain rate effects, geometric and material nonlinearity. The stiffened cylinder under consideration is modelled using Belytschko-Tsay shell element and the fluid and explosive using Eulerian solid element. The explosive is modelled using JWL equation of state, the fluid using Gruneisen equation of state and the stiffened cylinder fluid interaction using ALE coupling. The permanent deformation obtained from the numerical study compares well with experimental results within 5% accuracy. Subsequently, parametric investigation has been carried out for various charge weights with different cylindrical shell thickness and the results of permanent deformation, effective plastic strain are presented.