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.
