Deformation Behaviors of Aluminum Pipes Compressed in the Direction of Pipe Axis

Recently there are strong demands for reduction of carbon dioxide exhausted from cars on the viewpoint of global warming prevention. And, improvement in safety of cars is needed with increase of its speed. The main method to satisfy the former demand is to reduce the mass of cars, and main procedure to solve the latter subjects is to protect lives of crews in the head-on collision of automobiles. Lightweight members to absorb the energy at the collision have been installed in the engine room in order to satisfy abovementioned both demands. The purpose of this study is to optimize cross sectional size and shape of the aluminum pipe as the lightweight members for energy absorption.(1)(2)(3) In this report, the specimens are aluminum pipes whose shapes are hexagon and octagon. And ribs that connect one corner to opposite corner of the specimens in order to increase the energy absorption at the collision are installed inside the hexagonal and octagonal pipes. We also prepared the other specimens where the ribs are removed from the pipes. These specimens are compressed in the direction of the pipe axis, and deformation behaviors are observed. We investigate the effect of cross sectional shape on the performance of energy absorption, being measured from the force-displacement diagram obtained by compressive test. The results are as follows. (1) The plastic deformation by compressive test of the aluminum pipes starts from initiations machined at the vicinity of the pipe end then the folds results one after another in the pipes. (2) When we start to compress the pipe from which the ribs are removed, compressive force reaches at its maximum value, thereafter the force rapidly and greatly drops with large plastic deformation. And the force moves repeatedly up and down at its lower values with the progress of folds. (3) When we start to compress the pipes in which the ribs are installed, the drop of the force is smaller than that of the pipes without ribs and the force moves repeatedly up and down at its higher values. (4) The amounts of energy absorption at the octagonal pipe are bigger than those of the hexagonal pipe. And, the amounts of energy absorption of the pipes in which the ribs are installed are bigger than those of the pipes from which the ribs are removed.Copyright © 2004 by ASME