The Influence of Cold-Forming Residual Stresses on Crashworthiness Efficiency of Thin-Walled Structures

Abstract This study investigates the behavior of thin-walled column energy absorbers made from 6063-T6 alloy, incorporating spherical crush initiators. Such absorbers are widely used in automotive and aerospace applications due to their high energy absorption efficiency under axial impact. Experimental and numerical analyses revealed the presence of residual stresses resulting from the embossing process used to form the spherical triggers. Detailed examination of the embossed zones using X-ray diffractometer confirmed localized structural changes. To assess the effect of thermal stress relief, specimens were furnace annealed at four temperatures: 100 °C, 150 °C, 200 °C, and 250 °C. Subsequently, they were dynamically crushed using an Instron Ceast 9350 HES system. The crushing process was recorded with a Phantom Miro M310 high-speed camera to capture the real-time initiation and propagation of deformation. Comparative analysis of the structure, energy absorption indicators ( e.g. , peak crushing force, crush force efficiency), and failure modes demonstrated that annealing significantly influenced the crushing behavior. These findings emphasize the critical role of manufacturing parameters and thermal post-processing in the performance of thin-walled energy-absorbing structures.