A study on mechanics of collapse of combined geometry metallic shells

The combinations of shell structures give discontinuity to their load path and hence play major role in force-displacement behaviour of shell structures subjected to different types of loadings. In this paper thin aluminium shells having combination of shell geometries are tested to study their modes of collapse and associated force-displacement variations occurred during their large plastic deformation. The study is conducted on four categories of shell structures which are obtained through the combination of simple cylinder, frusta and hemisphere. The four categories are; Category 1 is simple cylinder as control shape, Category 2 is Cylinder with frusta, Category 3 is Cylinder with frusta with hemisphere and Category 4 is Cylinder with two frusta. The large plastic deformation was obtained by axially compressing these combined geometry shells between two flat plates experimentally using Instron machine and computationally using LSDYNA Finite Element code. The combined geometry shells behaviour during their large plastic deformation was understood with the help of force-displacement graphs for different geometrical changes. The associated change in mode of collapse is also presented and discussed. It was found that change in geometry influences large plastic deformation process and as a result force-displacement variation and associated modes of collapse.