Experimental and numerical studies on the folding response of annular-rolled Al tube

It is important to increase energy absorption of a tube under axial loading without using any reinforcement material. Also, such a process results directly in an increase of specific energy absorbing (SEA) capability of the tube. Based on this consideration, applicability of annular rolling process to thin-walled aluminium 6063-T5 tubes (D/t = 58/1.5) has been investigated experimentally and numerically. The study was conducted with two groups of tubular specimens. After determining the appropriate restricted fold length (RFL) value from short length tubes, the data were applied to long tubes. From the experimental studies of long-length annular-rolled tube, folding initiates within the RFL, and it enhances not only maximum folding, but also upper and lower force peaks in force-displacement curve. Thus, 23% improvement in SEA was obtained. Moreover, annular rolled tubes exhibited more outward folding with respect to that of the base tube, and this folding behaviour was used to explain results of the finite element (FE) analyses. It is concluded that annular rolling process is promising for thin-walled circular tubes for enhancing their energy absorption capabilities.