Investigation of Effect of Multiple Stepping and Curvature on Metallic Tubes for Crashworthiness Parameters and Energy Absorption Applications

Abstract

Crashworthiness of the structure is the most crucial concern in modern day automobile and aerospace industry, in order to protect the occupants, payload, sensitive equipment and the environment in case of any fatal crash situation. Light weight, cost effective and efficient thinwalled energy absorbing structures are the optimal choice to serve the purpose with enhanced crashworthiness characteristics while under dynamic crushing. The characteristics of energy absorption are size, cross-sectional geometry, material and boundary condition dependent for thin-walled structures. Thin metallic tubes proved themselves as efficient energy absorbers and have been in extensive use for many aerospace and automotive applications to improve the structure crashworthiness. Crashworthiness parameters may be improved through multi-cells arrangement, multiple cross-sectional features, functional gradient characteristics, addition of triggers and foam or honeycomb filling. Stepping in tube’s structure can provide energy absorption with progressive failure as per a design’s specific requirement; however, geometry parameters may influence their performance capabilities. Another important parameter is curvature of the surfaces or corners which may increase the critical buckling load and may guide buckling initiation and propagation. In this study, stepped tubes sensitivity with geometric variation and curvature effects are investigated on energy absorption characteristics of metallic tubes for circular and square tubes; with and without addition of curvature for square tubes and also with curved multi-cells stiffeners along the radial and axial direction and unconventional arrangements of bi-tubular arrangements with and without curvature. A number of geometry arrangements are studied and the effects of adding stepping and curvature are studied for their deformation and energy absorption characteristics. Different parameters such as mean crushing force, peak crushing force and specific energy absorption are determined and discussed for all of the proposed configurations. The proposed arrangements show a relatively stable crushing behavior and high crush force efficiency. In the final part, a robust decision making technique; the COmplex PRoportional ASsessment (COPRAS) is applied to the proposed configurations for determination of curvature effects in order to find the best configuration which is based on the amount of energy absorbed, low crushing force and high crush force efficiency.