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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^o. 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^o and 23^o 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.
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