Analysis of collapse behaviour of combined geometry metallic shells under axial impact

Collapse behaviour of aluminium thin conical frusta with shallow spherical caps (shells of combined geometry) is studied both experimentally and numerically. These shells were of four different thicknesses and were subjected to axial compression between two rigid platens under both quasi-static and impact loading. The R/t values of the spherical portion of the shells were varied between 27 and 218, and for the conical frusta portion, mean diameter-to-thickness (Dm/t) values were varied between 79 and 190. Quasi-static tests were performed on a UTM of 100 T capacity with digital recording facility. Impact experiments were carried out on a drop mass set-up. A three-dimensional non-linear finite element analysis was carried out using LS-DYNA. Numerical results thus obtained were validated with the experimental results. Typical time histories of the specimen deformation and load compression curves were obtained. The behaviour of these shells of combined geometry is compared with the response of the shells of spherical or conical geometries. A discussion on their deformation behaviour, mean buckling load and energy absorbed is presented, and influence thereon of various parameters is discussed.