The influence of inertia and strain-rate on large deformation of plate-structures under impact loading

The static and dynamic behaviour of plate-structures subjected to in-plane axial and compressive impact loading is investigated using the finite eleme nt method (FEM). The material model is linear elastic with nonlinear isotro pic work hardening characteristics with strain-rate dependence, inertia (vi a a consistent mass matrix) and geometrical nonlinearities are retained. Th e FEM results are in very close agreement with those obtained from experime nts but the main advantage of the method is that it clarifies the time hist ory behaviour of the model. The previous theoretical work has identified tw o distinct phases of deformation. Phase one is the compression of the plate , following the inelastic collision, until the structure becomes plastic. T his is followed by a second phase of continuous plastic work dissipation in rotation about the hinges formed. The FEM results indicate the nature of t he collision strain rate intensity and the differences that exist between s tatic and dynamic modes of deformation response. The numerical modelling al so reveals four phases in the deformation process. A phase of stress wave p ropagation is identified during elastic loading and the build up of high in itial axial forces in the specimen. This is followed by a squashing phase, hinge rotation and elastic recovery (or, when the impact energy is high eno ugh, structural closure) before the striker rebounds. The closure phase res embles a severe forming process followed by elastic recovery of the specime n and rebound of the striker. The differences between the various treatment s are discussed and analysed in some detail. (C) 2001 Elsevier Science Ltd. All rights reserved.