Relative merits of conical tubes with graded thickness subjected to oblique impact loads

The energy absorption characteristics of a type of conical tubes with graded thickness (CTGT) under oblique impact loads were investigated in this paper. The influences of load angle, structure layout, strain rate effect, inertia effect and forming effects on the responses of CTGT were analyzed numerically by using finite element model validated by experiments. The reverse layout of CTGTs showed very much better performance against oblique loads than the original straight circular tubes employed to fabricate it. The thickness variation and material hardening during fabrication delayed the switch from progressive to global budding for reverse layout of CTGT and enabled it to preserve most of the axial crush resistance when subjected to oblique loads with load angle up to 20 degrees. The increase in the extent of forming effects was not always found to be beneficial and moderate extent of forming was suggested in applications against oblique loads. The outcomes of this study will facilitate the crashworthiness design of CTGT structures with better performance when subjected to oblique loads. (C) 2015 Elsevier Ltd. All rights reserved.