2012 Volume 53 Issue 5 Pages 812-819
In order to numerically evaluate hydroformed DP-steel tubes on crash performance while considering weld-heat effects, finite element simulations of the crash were performed for hydroformed tubes with and without considering heat treatment effects. Also, finite element simulations were carried out for sequential procedures of bending and hydro-forming of tubes in order to evaluate formability and spring-back for process parameters: boost condition and axial feeding. As for the constitutive law, the isotropic hardening law was used along with non-quadratic anisotropic yield functions Yld2000-2d. Forming limit diagrams were calculated based on Hill’s bifurcation theory and the M–K theory. In order to characterize the material properties of the base material (BM) sheet, tensile tests were performed with various strain rates. Tensile tests were conducted also for tensile specimens that were cut out from tubes for the measurement of material properties of the base material (BM) tube and electric resistance weld (ERW) zone. The mechanical properties of the metal inert gas (MAG) arc-weld zone as well as those of the heat affected zone (HAZ) were also obtained by using the continuous indentation method. Based on the determined material characteristics, crash performance evaluations were then numerically carried out for the tube, formed with optimized process parameters, with and without welding heat effects. With this work, numerical methods to properly implement the welding heat effects on the tube crash performance were established, which will be useful to evaluate the welding heat effects on the tube crash performance under realistic crash conditions.