Characteristics of Inversion Tubes under Axial Loading

Abstract

A thin wall tube, when axially compressed over a radiused die, either inverts, or buckles or tears. The phenomena associated with the external or internal inversion of tubes of aluminium, copper, mild steel and brass are described and load-tube shortening curves are presented for speeds of compression between 0·05 in/min and 20 in/min; some results for high speed compression using a drop hammer are also described. Thickness changes during inversion are reported and experiments to establish the effect of die angle and die radius on the inversion load are given. For the inside-out inversion of tube, a simple theoretical analysis to predict the steady inverting load and the optimum die radius for a strain hardening material is given, the basic assumption being that no change in the wall thickness takes place.