Axial Deformation of Shells at Higher Strain Rates using Buckling Initiators

Deformation mode of cylindrical shells and their peak load reduction is of prime importance in impact damage mechanics. In this study, numerical investigation is carried out for triggering mechanism induced in the thin-walled axially compressed short stubby shells, considering the damage occurred in vehicle crash or in any other protective equipment. The shells are studied for their initial buckling response under varying impact velocities for two different triggering configurations. Explicit simulation is carried out using ABAQUS/Explicit® to study the initial buckling of the shells by modelling Split Hopkinson Pressure Bar (SHPB) test setup. Initially, numerical scheme is validated using previously available study. Present analysis is carried out using diamond shaped triggering notches and these are configured in such a way that the shell will deform in particular buckling mode, under the impact of three different velocities i.e. 9 m/s, 20 m/s and 40 m/s. Effect of these notches and their pattern of arrangement on reduction in peak load and energy absorption characteristics are studied. Moreover, comparison is made between commonly used circular hole and diamond notch type cut-outs, in order to study the effect of above said parameters along with the energy absorbed, energy efficiency and specific energy absorption for the shells considered herein. By numerically impacting the shells in SHPB, it is observed that peak load reduction is higher in diamond notched shells as compared to circular hole shells. This was due to the geometry and size of the cut-outs considered in this study. Parameters like peak collapse load, energy absorbed, energy efficiency along with stress concentration around the notch are also observed and studied in this work in order to observe and compare the two shapes of cut-outs.