On the inextensional axial collapse of thin PVC conical shells

Abstract

Inextensional collapse mechanisms are presented for the axial crumpling of thin-walled circular cones and frusta (truncated circular cones). Shortening of the (thin) shell height is achieved by folding in a non-symmetric diamond mode about stationary circumferential and inclined plastic hinges; collapse proceeds progressively from the narrower end of the conical shell during the passage of a travelling hinge. Expressions for the various mean crushing loads, when collapsing frusta of rigid-perfectly-plastic material, are developed. Theoretical collapse modes and predicted loads are compared with those obtained experimentally by collapsing rigid PVC conical shells of constant axial length, of various wall-thicknesses and semi-apical angles, as well as metal (aluminium alloy and low-carbon steel) conical shells of similar geometry; agreement is found to be good.