NONLINEAR TRANSIENT ANALYSIS OF SUBMERGED CIRCULAR PLATES SUBJECTED TO UNDERWATER EXPLOSIONS

A new coupled finite element and boundary integral formulation is deve loped for non-linear transient analysis of submerged thin circular pla tes subjected to underwater explosions. In this new formulation, the g overning equations of motion of the structure are completely decoupled from those of wave propagation by applying Kirchhoff's integral equat ion on the wet surface of the structure, thereby eliminating the need for modelling the surrounding fluid. Using Kirchhoff thin plate theory , an axisymmetric ring plate element is formulated, which lakes into a ccount both geometric and material non-linearities as well as strain-r ate effects. The scattered pressure field due to the fluid-structural interaction is calculated by solving the surface integral equation in the context of element discretization method. The effects of water cav itation on structural response are included by using an appropriate pr essure criterion. The time-dependent solution of the coupled fluid-str ucture system is then solved by applying a staggered solution algorith m at each time step in a direct time-integration procedure. The propos ed formulation has been tested for a number of applications and the re sults obtained are compared with experiments. It is observed that the new formulation can provide reasonable solutions to both near- and far -field interaction problems for underwater shock response analysis.