Parallel Computing of Multi‐scale Finite Element Sheet Forming Analyses Based on Crystallographic Homogenization Method
Since the multi-scale finite element analysis (FEA) requires large computation time, development of the parallel computing technique for the multi-scale analysis is inevitable. A parallel elastic/crystalline viscoplastic FEA code based on a crystallographic homogenization method has been developed using PC cluster. The homogenization scheme is introduced to compute macro-continuum plastic deformations and material properties by considering a poly- crystal texture. Since the dynamic explicit method is applied to this method, the analysis using micro crystal structures computes the homogenized stresses in parallel based on domain partitioning of macro-continuum without solving simultaneous linear equations. The micro-structure is defined by the Scanning Electron Microscope (SEM) and the Electron Back Scan Diffraction (EBSD) measurement based crystal orientations. In order to improve parallel performance of elastoplasticity analysis, which dynamically and partially increases computational costs during the analysis, a dynamic workload balancing technique is introduced to the parallel analysis. The technique, which is an automatic task distribution method, is realized by adaptation of subdomain size for macro-continuum to maintain the computational load balancing among cluster nodes. The analysis code is applied to estimate the polycrystalline sheet metal formability.
Asymmetrie rolling process simulations by using dynamic explicit crystallographic homogenized elasto/viscoplastic finite element method
Recently, the asymmetric rolling (ASR) was applied to the material process of aluminum alloy sheet generation to control the micro-crystal structure and the texture in order to improve the mechanical properties, such as the strength and the formability. Until now, many experimental studies aimed to the high formability sheet generation have been carried out, but a numerical scheme to predict the deformation induced texture evolution of the asymmetrically rolled sheet metal have not been accomplished. In this study, the crystallographic homogenized elasto/viscoplastic finite element (FE) code is developed and applied to analyze the asymmetrical rolling process. The textures of ASR sheet metals are measured by the electron backscatter diffraction (EBSD) method, and are compared with these ASR rolling FE simulation results. This multi-scale FEM code shows a comprehensive tool to predict the plastic induced texture evolution.
Study of Texture Effect on Sheet Failure in a Limit Dome Height Test by Using Elastic/Crystalline Viscoplastic Finite Element Analysis
By combining the crystalline orientation distribution with a hardening evolution equation, a new elastic/crystalline viscoplastic material model is established. We focus our discussion on looking primarily at the texture effects on the strain localization of limit dome height (LDH) tests which are simulated using our Dynamic-Explicit finite element code. Three crystalline models in addition to the classical plastic potential and associated flow law model (J 2 F) are employed. The results demonstrate that, according to our failure criterion, the random orientation model shows the earliest indication of failure. The better formability is obtained for aluminum alloy 6111-T4 and cube texture models than the random crystalline orientation model. The J 2 F model shows no signs of strain localization. A comparison between numerical results also confirms that the strain localization region and crystalline rotation are different, due to the crystalline orientation distribution, which is initially set.