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.
Impacts of the 2011 tsunami on the subtidal polychaete assemblage and the following recolonization in Onagawa Bay, northeastern Japan.
The ecological impacts of the 2011 Great East Japan Earthquake and tsunami and the following recolonization of the subtidal benthic polychaete community were examined by monthly pre- and post-quake field surveys that were conducted in Onagawa Bay from 2007 to 2013. Before the tsunami, the species composition in this benthic community was constant and was dominated by cirratulid and magelonid polychaetes. The density and biomass of benthic polychaetes drastically decreased after the tsunami, and the polychaete community fluctuated during the 2 years after the natural disaster. Spionid and capitellid polychaetes were dominant at this period. In June 2013, the community entered a new constant stage dominated by maldanids, which is different from the pre-quake community. Ecological impacts due to chemical pollution were suggested in addition to the tsunami disturbance. These overlapping effects and physical, chemical and biological factors affected the recovery and recolonization of the polychaete community after the natural disaster.