56(a)Dendriticpattern(b)Polycrystalline (c)Cell structure(d)Grain refinementContentContent：Mostengineeringmaterialsconsistofcomplicatedmicrostructures Most engineering materials consist of complicated andtheystronglyaffectthemacroscopicmaterialproperties.microstructures and they strongly affect the macroscopic material properties. Therefore, precise evaluation of the Therefore,preciseevaluationofthemicrostructureisrequired.Inourmicrostructure is required. In our research group, various researchgroup,variouscomputationalmethodshavebeendevelopedcomputational methods have been developed using molecular usingmoleculardynamics,phase-fieldmodel,andcontinuumdynamics, phase-field model, and continuum mechanics. Our mechanics.Ourultimategoalistoconstructamulti-scalemechanicsultimate goal is to construct a multi-scale mechanics predicting predictingthemacroscopicmaterialstrengthbasedonthethe macroscopic material strength based on the microstructure. All the figures in the left-side box are our simulation results; (a) microstructure.Allthefiguresintheleft-sideboxareoursimulationdendritic structure and (b) polycrystalline formation, both of results;(a)dendriticstructureand(b)polycrystallineformation,bothwhich are simulated using phase-field model. Figure (c) represents ofwhicharesimulatedusingphase-fieldmodel.Figure(c)representsa numerically modelled cell structure, which can be applied to anumericallymodelledcellstructure,whichcanbeappliedtovarious materials such as porous materials. Figure (d) shows grain refining process under severe compressive deformation variousmaterialssuchasporousmaterials.Figure(d)showsgrainobtained by molecular dynamics simulation. We also apply finite-refiningprocessunderseverecompressivedeformationobtainedbyelement simulations to predict deformation and residual stress moleculardynamicssimulation.Wealsoapplyfinite-elementdistribution during heat treatment such as quenching of steel. simulationstopredictdeformationandresidualstressdistributionduringheattreatmentsuchasquenchingofsteel.Special objectivesAppealingpoint： We are trying to totally simulate complete material processing Wearetryingtototallysimulatecompletematerialprocessingtoto predict deformation and strength of materials based on predictdeformationandstrengthofmaterialsbasedonmicroscopicmicroscopic properties, leading to improvement of engineering properties,leadingtoimprovementofengineeringproducts.products. Content Conventional mechanics of materials does not account for intrinsic material length scales. When similarities exist in geometric dimensions and load conditions in two problems, the conventional theory gives the same stress and strain solutions regardless of the assumed dimensions. In reality, peculiar material behavior is observed at the micrometer scale, i.e., the size effect exists. In the present study, a theory of microscale plasticity is pursued, incorporating knowledge of accumulations and movements of dislocations. Using this theory, strengthening mechanisms of metallic materials, which have not yet been understood completely, are investigated. The phenomenon “smaller is stronger” generally is observed. But, its physical cause is not known completely. The developed theory is expected to be utilized in designing and developing new high-strength/high-ductility materials.Special objectives Regardless of the long history that human beings developed the modern society with effective use of metals, we have a lot of unresolved problems about them. This study aims at theoretical modeling of mechanical behavior of metals, which enable us to simulate the phenomena from deformation to fracture in a digital computer.(a)(b)(c)(d)Yamagata University Graduate School of Science and Engineering Research InterestMechanics of MaterialsE-mail ・ kuroda@yz.yamagata-u.ac.jpTel ・ +81-238-26-3211Fax ・ +81-238-26-3205HP・http://kuroda.yz.yamagata-u.ac.jpYamagata UniversityGraduate School of Science and Engineering Yamagata University Graduate School of Science and Engineering Research Interest:Computational mechanics, Research InterestSolid mechanics, Materials scienceComputational mechanics, Solid mechanics, Materials scienceE-mail : uehara@yz.yamagata-u.ac.jpE-mail ・ uehara@yz.yamagata-u.ac.jpTel ：+81-238-26-3285Tel ・ +81-238-26-3285Fax：+81-238-26-3285Fax ・ +81-238-26-3285HP ：http://uhlab.yz.yamagata-u.ac.jp/index.htmlHP・http://uhlab.yz.yamagata-u.ac.jp/index.htmlProfessor Mitsutoshi KurodaProfessor Takuya UeharaComputer Simulation of Microstructure Formation in MaterialsComputer Simulation of Microstructure Formation in MaterialsMechanical Behavior of Metals and Its Mathematical ModelingProfessor Takuya Uehara
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