The effect of geometrical parameters on the energy absorption characteristics of thin-walled structures under axial impact loading

Abstract

In this study, the crush behaviour of thin-walled straight and conical shell structures was systematically determined for various absorber designs and investigated comparatively under axial impact loading. The main parameters in the design of these structures are cross-section geometry, wall thickness and semi-apical angle. Several cross sections have been studied: circular, square and hexagonal. In the finite element simulations, these designs were fixed at one end and impacted by a rigid wall from the other with specified mass and velocity giving the required impact energy according to the European regulation ECE R29 by using explicit finite element code LS-Dyna. After crash simulations, energy absorption characteristics and crush forces were obtained for each crush element having different cross sections, wall thicknesses and semi-apical angles. Peak crush force, mean crush force, crush force efficiency and specific energy absorption (SEA) were calculated for a deformation length of 100 mm. In all cases it was found that tubes were crushed progressively. The results of the simulations showed that the square cross-sectioned energy absorber has the lowest crush force efficiency among three cross-section geometries. The crush force efficiency was found to be the highest for the circular absorber which has a semi-apical angle of 12.5° and a wall thickness of 2 mm. Finally, the peak crush forces were lowered by creating blanks and corrugations.

Keywords:

• energy absorption
• conical tubes
• crashworthiness
• axial impact
• LS-Dyna

Acknowledgements

This study is funded by the Turkish Ministry of Industry and Trade and TEMSA AR-GE VE TEKNOLOJİ A.Ş. within the scope of the SAN-TEZ project 00236.STZ.2008-1. Authors would like to thank Drs. Ulrich Stelzmann of CADFEM and Erdem Acar for their contributions to this study.