An analysis of axi-symmetric axial collapse of round tubes

Different size tubes of aluminium and mild steel were subjected to axial compression in an Instron machine. The tubes chosen were such that they collapsed in axi-symmetric concertina mode. Typical load-compression curves and deformed shapes of the collapsed tubes are presented. These reveal that the axi-symmetric folds formed in the deforming specimens extend both inside and outside of the line of original tube radius, and the ratio of the inside to outside fold lengths depends on the tube dimensions.

Considering the tube collapse mechanism as observed experimentally, an analysis is presented in an attempt to predict the mean collapse load and the post collapse load-compression curve. The computed values of the mean collapse load and the load-compression curve during a load oscillation, are presented and compared with the experiments, as well as with some existing theoretical results.