LARGE-DEFORMATION OF THIN PLATES UNDER LOCALIZED IMPULSIVE LOADING

The response of thin clamped plates to a localised impulsive load impa rted over a central circular region is investigated experimentally and theoretically to determine the location of tearing failure and the cr itical impulse to failure. Over 40 tests were performed with four diff erent loading radii and increasing values of the applied impulse. Typi cal dish like deflection profiles were produced and measured. It was o bserved that smaller loading radii led to a more localised bulging nea r the plate centre. The resulting plate failure took the form of a dis c. A more distributed load produced tearing failure at the clamped bou ndary. In the theoretical development, the plate was modelled as a rig id-plastic membrane. The resulting initial-boundary value problem for the wave equation in the polar co-ordinate system was solved by the ei genfunction expansion method up to the point of first unloading. An ap proximate closed-form solution was also obtained by combining the wave form solution for early motion with the mode solution for late motion . A good correlation was obtained between the predicted and measured n ormalised deflection profile. The analysis of the theoretical solution gave strong indication that the initial velocity profile must have a form of a continuous and smooth function near the edge of the burning zone. Precise determination of the deflected shape is a necessary step for strain calculations and the prediction of the onset of tensile ne cking and failure of plates. Copyright (C) 1996 Elsevier Science Ltd.