Comparison and optimization of impact behavior of triangular tubes

Crashworthiness technology strives to protect occupants by maintaining the structural integrity and by converting the kinetic energy into other forms; and at the same time, the lower crashing force the occupants are being undertaken, the more safety the occupants would obtain. The paper has compared different tubes with the same volume under the same impacting condition and found out that triangular tube possesses the lowest crushing mean force. Load difference parameter (LD) is defined as the difference between maximum peak force and dynamic mean force in the paper. In order to reach the lowest LD parameter, response surface method (RSM) is used to identify the optimal shape of triangular tube using explicit finite element code Ls-Dyna as a simulation tool. The study has also shown that the circular cross-section tube has the highest dynamic mean force, followed by the hexagonal cross-section tube, then the rectangular cross-section tube, and lastly, the triangular cross-section tube, under the same supporting capacity and impact environment. Applying RSM to identify the best triangular shape to reach the minimum LD parameter as objective function, the central composite design is applied for design of experiment. The second-order model and third-order model have been used to compare the results in order to show the influence of regression methods. Two impacting condition are applied for optimization, namely fixed tube and moving tube. The final results show that the minimum LD value convergences at the equal lateral triangle for both impacting cases. The coefficient of multiple determinations R² for both impacting case are all over 0.9 for third-order model. Also, the normality of residual, the deformation modes, crushing force are presented and discussed for optimal triangular tubes.