Modelling kinetics of phase transformation for the indirect hot stamping process to focus on car body parts with tailored properties

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• 作者：Paul Hippchen^a ; ^{paul.hippchen@bmw.de" class="auth_mail" title="E-mail the corresponding author} ; Arnulf Lipp^a ; ^{arnulf.la.lipp@bmw.de" class="auth_mail" title="E-mail the corresponding author} ; Hannes Grass^a ; ^{hannes.grass@bmw.de" class="auth_mail" title="E-mail the corresponding author} ; Philipp Craighero^a ; ^{philipp.craighero@bmw.de" class="auth_mail" title="E-mail the corresponding author} ; Michael Fleischer^a ; ^{michael.ma.fleischer@bmw.de" class="auth_mail" title="E-mail the corresponding author} ; Marion Merklein^b ; ^{marion.merklein@fau.de" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Indirect hot stamping process ; Material modelling ; Kinetics of phase transformation
• 刊名：Journal of Materials Processing Technology
• 出版年：2016
• 出版时间：February 2016
• 年：2016
• 卷：228
• 期：Complete
• 页码：59-67
• 全文大小：1844 K

文摘

To design the indirect hot stamping process, a finite element method (FEM) based prediction of the part geometry and the mechanical properties is required. In case of indirect hot stamping processes, producing car body parts with tailored properties, cooling paths occur causing diffusionless and diffusion controlled phase transformations. The volume expansion caused by the phase transformation of face-centred cubic (fcc) into body-centred cubic (bcc) and the martensitic formation of body-centred tetragonal (bct) leads to transformation induced strains that are important for the calculation of overall stresses in hot stamped car body parts. To calculate the strain and stress state correctly, it is necessary to model the diffusionless and diffusion controlled phase transformation phenomena, taking into account the boundary conditions of indirect hot stamping processes. The existing material models are analysed and extended in order to improve their prediction accuracy in calculating the amount and distribution of ferrite, perlite, bainite and martensite during the whole process of annealing. For industrial use the new approaches are implemented in the FE-code LS-DYNA 971 (Livermore Software Technology Corporation, 2006).