부산대학교 도서관

This study investigated the elastic recovery phenomenon with elapsed time and heat treatment after the plastic deformationof automotive steel sheets. A conventional uniaxial loading–unloading-loading test was modified to include the elapsed timeand heat treatment conditions. The elastic behaviors of five automotive steel sheets, MART1500, TRIP1180, EDDQ, DP980,and BH340, were characterized after applying various pre-strains, specific elapsed time conditions, and heat treatments. Theelastic behaviors were quantitatively analyzed using the conventional chord modulus definition and a new elastic modulusdefinition representing the initial elastic characteristics. It was observed that the elastic behavior of BH steel was the mostsensitive to elapsed time and heat treatment in terms of recovery owing to the bake-hardening effect. The elastic moduli of theMART1500 and TRIP1180 steel recovered somewhat after heat treatment, whereas no recoveries of EDDQ and DP980 steelswere observed. Phenomenological modeling of the recovery process was also performed. The Yoshida–Uemori modulusmodel was applied to the experimental results for elastic degradation. This model was then extended to consider the elapsedtime and heat treatment, and the elastic recovery behaviors of the different steels were captured successfully.