Improving the crashworthiness characteristics of cylindrical tubes subjected to axial compression by cutting wide grooves from their outer surface

This paper investigates a new and efficient design method to encourage axisymmetric collapsing mode in tubes with higher length than the critical length to collapse in concertina mode when subjected to axial compression. In this innovative design method, wide circumferential grooves are cut from the outer surface of the tube at some determined areas along tube length. When this structure is subjected to axial compression, folds are shaped within the space of these grooves. In fact, this method divides a long tube without the potential of collapsing in axisymmetric mode into several tubes of shorter length, being assembled together coaxially, with the potential to collapse in axisymmetric mode. In the present study, several numerical simulations using LS-DYNA finite element explicit code are performed to study the energy absorption characteristics of this structure under quasi-static compression and to determine the effect of various geometric parameters on its collapsing modes of deformation. In order to verify these numerical results, some experimental tests are performed. An analytical model to predict mean crush force of the new shock absorber is also developed in the present study. Through experimental, numerical and analytical studies, major parameters in design are identified, and typical modes of deformation that may occur during axial compression of tubes with wide external grooves are characterised. Also, load–displacement history and deformation mechanism of the structure under axial compression are described. It has been shown that with consideration of design parameters, characterised in this paper, cutting wide external grooves along circular metal tube length can significantly improve their energy absorption characteristics.