2022 Fiscal Year Final Research Report
Disclination-based crystal plasticity model and mess-free analysis at large deformation for strengthening of LPSO/Mg alloys
| Project/Area Number |
20K04165
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 18010:Mechanics of materials and materials-related
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| Research Institution | Keio University |
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Principal Investigator |
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | LPSO型Mg二相合金 / 有限変形理論 / 結晶塑性Cosseratモデル / キンク帯 / 回位密度 / 転位密度 / 強度発現機構 / 寸法効果 |
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| Outline of Final Research Achievements |
The mechanical properties of Mg dual-phase alloys with long-period stacking ordered (LPSO) phase are significantly enhanced by the formation of fine kink bands. In this study, to clarify the strengthening mechanism owing to the kink bands, the Cosserat model was formulated in the framework of crystal plasticity based on finite deformation theory and a new material model was developed, in which the accumulation of dislocations and the generation of disclinations were simultaneously considered. Using the obtained model, a mesh-free analysis was performed for a strip-shaped tri-crystal. As a result, it was showed that when a kink band is formed by compressive loading and then reverse loading is applied, if ridge-shaped kinks tend to occur, local orientation differences and accumulated dislocations remain more, and the terminal strength is higher. In addition, the smaller the average grain size of the α-Mg phase becomes, the higher the terminal strength after reverse loading reaches.
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| Free Research Field |
計算材料科学
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| Academic Significance and Societal Importance of the Research Achievements |
構造材料の軽量化と強化の立場から脱炭素社会実現に寄与する以下のような知見を得た．有限変形理論の範疇では，GN転位密度はすべりこう配のみならず回位密度にも依存する．また，試験片端部の回転を拘束できる本モデルでは，試験片寸法によらずキンク帯を再現できる．さらに，微視回転と巨視回転を独立変数としつつペナルティ法で一致させれば，C0級要素を用いたFEM解析によってメッシュフリー法と同程度の精度で計算コストを低減させ得る．加えて，底面系を荷重軸にほぼ平行に配置するとともに初期方位の不均一性を増大させ，α-Mg相を微細化すれば，圧縮後に逆負荷を加えた際，終端強度を1～3割程度増加させ得る．
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