A study on mode of collapse of varying wall thickness metallic frusta subjected to axial compression

Abstract

The present paper deals with experimental and computational analysis of deformation behavior of the aluminum thin-walled frusta subjected to axial compression between two parallel platens. The frustas were having different wall thickness through out their height. The frustas were having semi-apical angles between 7 and 9 with D/ t values ranging between 26 and 49. Experiments were performed on a universal testing machine INSTRON. The frusta were tested to identify their modes of collapse and to study the associated energy absorption capacity. In experiments, all the frusta were found to collapse with the formation of an axisymmetric mode of collapse due to development of the associated plastic hinges. A Finite Element computational model of development of the axisymmetric mode of collapse is presented and analyzed, using a non-linear Finite Element code FORGE2. The material of the frustas was idealized as rigid visco-plastic. Experimental and computed results of the deformed shapes and their corresponding load- and energy-compression curves were presented and compared to validate the computational model. Typical contours of equivalent strain, equivalent strain rate, nodal velocity distribution, hoop stress and principal stress are presented to help in predicting the mode of collapse. On the basis of the obtained results development of the axisymmetric mode of collapse has been presented, analyzed and discussed.