Effect of radial clearance and holes as crush initiators on the crashworthiness performance of bi-tubular profiles

Abstract

The use of bi-tubular structures has gained importance in the design of energy absorption systems for protection of passengers in train collisions. Therefore, it is critical to improve the crashworthiness performance of bi-tubular profiles. For this purpose, the effect of cross-section, bi-tubular clearance and holes as crush initiators is evaluated using finite element simulations. To get reliable outcomes, special emphasis was set on the progressive damage modelling of aluminum 6063-T5 by a Johnson-Cook (J-C) failure model. During the cross-section study, bi-tubular arrangements based on polygonal and circular cross-section were evaluated by quasi-static compression loads. The results indicate that the circular shapes showed better crashworthiness performance or crush force efficiency (CFE) up to 12.28% respect to a square base structure. A 10.72% improvement in CFE was obtained when the non-dimensionalized clearance between profiles is increased from λ=20 to λ=40. The effect of holes on crashworthiness performance was evaluated by drilling holes at different locations both in the inner and outer profiles. The results show that the use of holes increased the crush force efficiency and energy absorption (Ea) capability even more than the effect of clearance alone. Improvements in the order of 2.50% and 12.96% for Ea and CFE respectively were computed when holes were placed at the top end of a BC-3 profile with a non-dimensional clearance of λ=40. Considering all effects simultaneously, an increase of 24.6% and 26.31% for Ea and CFE respectively was calculated. Finally, an application to a crash buffer in a railway transport system is considered. Likewise, its improved crashworthiness behavior is presented.