Effect of punch angle on energy absorbing characteristics of tube-type crash elements

As a crash energy absorber, a tube-type crash element (expansion tube) dissipates kinetic energy through the internal deformation energy of the tube and through frictional energy. In this paper, the effects of the variation of punch angles on the energy-absorbing characteristics of expansion tubes were studied by quasi-static tests using three punch angles (15A degrees, 30A degrees, and 45A degrees). A finite element analysis of the tube expanding process (m = tau (max) /K) was performed using a shear friction model to confirm the variation of the shear friction factor with respect to punch angles using the inverse method. Additional analyses were performed using angles of 20A degrees, 25A degrees, 35A degrees, and 40A degrees to study the effect of the punch angles on the internal deformation energy, frictional energy, and expansion ratio of the tubes. The results of the experiment and finite element analysis showed that the shear friction factor was inversely proportional to the punch angles, and a specific punch angle existed at which the absorbed energy and expansion ratio remained constant.