A study on axial compression of tubular metallic shells having combined tube–cone geometry

Abstract

The present paper deals with the experimental and computational study of collapse of the metallic shells having combined tube–cone geometry subjected to axial compression between two parallel plates. The aim is to study the influence of the shell thickness and cone angle on its mode of deformation. Shells were having top one third length as tube and remaining bottom two third length as truncated cone having semi-apical angle about 23°. The other geometrical dimensions were almost same. Shells were tested in an INSTRON universal testing machine, to identify their modes of collapse and associated energy absorption capacity. In experiments it was found that the collapse process of all shells was initiated by development of an axisymmetric fold followed by a plastic zone of increasing length.An axisymmetric Finite Element computational model of collapse process is presented and analysed, using a non-linear FE code FORGE2 [13]. Six noded triangular elements were used to descretize the domain. The material of the shells was idealised as rigid visco-plastic. Experimental and computed results of the deformed shapes and their corresponding load-compression and energy–compression curves were compared to validate the computational model. Typical computed variations of nodal velocity distribution, equivalent strain rate, equivalent strain, hoop stress and principal stress are presented to help in predicting the mode of collapse. On the basis of the experiments and computed results development of the axisymmetric mode of collapse has been presented, analysed and discussed. Further the computational model is used to simulate the mode of collapse of specimens having lower semi-apical angles between 19° and 23° of the conical portion. It was found that the mode of collapse of combined geometry specimens mainly governed by the semi-apical angle of the truncated cone portion.