Lateral crushing of circular and non-circular tube systems under quasi-static conditions

In the study of impact attenuation devices, rings/tabes have received a large amount of research due to their adaptability, i.e. they are low in cost and are readily available for selection in the design process. They also exhibit desirable force-deflection responses which is important in the design of energy absorbing devices. The function of such a device is to bring a moving mass to a controlled stop and ideally cause the occupant ride down deceleration to be within acceptable limits so as to avoid injuries or to protect delicate structures. An energy absorbing device may consist of a system of rings/tubes that are compressed laterally which absorbs the kinetic energy upon impact and dissipating it as plastic work. In this work, the quasi-static analysis of nested circular and elliptical (non-circular) type energy absorbers is examined using experimental and numerical techniques. Although these devices are usually exposed to much higher velocities, it is common to analyse the quasi-static response first, since the same pre-dominant geometrical effects will also occur under dynamic loading conditions. Nested systems consist of circular tubes or elliptical shaped tubes of different diameters which are placed within each other and their axes being parallel. Compression of these systems is achieved via two rigid flat platens, one placed above and below the absorber to be analysed. Discussion is made on how the circular tubes were formed into elliptical shapes and how such a modified shape can exhibit greater crush efficiencies than their circular shaped counterparts. A numerical technique via the finite element method is used to simulate the loading and response of such devices and hence, comparison of numerical and experimental force-deflection response is presented. (C) 2007 Published by Elsevier B.V.