Variation of kinetic friction coefficient with respect to impact velocity in tube type energy absorbers

The expansion tube used as a crash element dissipates crash energy through internal deformation energy of the tube and frictional energy. In this paper, in order to study the effects of impact velocity on the characteristics of energy absorption of an expansion tube, friction quasi-static and dynamic experiments were carried out and an inverse method using finite element analysis and the least square method was introduced to calculate the friction coefficient at each impact velocity. The results of the experiments and the finite element analyses show that an increase of the impact velocity increased the strain rate of the tube. Energy absorbed into tube was increased due to the strain rate effect. The friction coefficient in the quasi-static state was higher than that in the dynamic state. The results of a comparison of mean forces and absorbed energies with experimental results indicate that the least square method is appropriate to calculate the friction coefficient in the case of an expansion tube.

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