| Project/Area Number |
18K04778
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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 26050:Material processing and microstructure control-related
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| Research Institution | Hiroshima University |
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Principal Investigator |
Hino Ryutaro 広島大学, 先進理工系科学研究科(工), 准教授 (10283160)
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| Project Period (FY) |
2018-04-01 – 2022-03-31
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| Project Status |
Completed (Fiscal Year 2021)
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| Budget Amount *help |
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2020: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2019: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2018: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
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| Keywords | 高張力鋼板 / 伸びフランジ変形 / 成形限界ひずみ / 面内引張曲げ試験 / 穴広げ試験 / ひずみ勾配 / 有限要素解析 / 成形限界 / 破断クライテリオン / プレス成形 |
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| Outline of Final Research Achievements |
In-plane stretch bending test was proposed as a new stretch flangeability testing method. Evaluation and prediction of the stretch flangeability for several high-strength steel sheets having strength levels ranging from 590 MPa to 980 MPa were conducted.
It was clarified that there are two types of fracture, i.e. edge cracking from the outside edge of the bent sheet and internal cracking starting from a position apart from the edge. Effects of the stretching force, strength of the steel sheet, and sheet edge condition on the fracture type and stretch flangeability have been revealed. Relationship between strain gradient around the sheet edge and the forming limit in stretch flanging was also clarified, and the stretch flangeability in the in-plane stretch bending was found to be higher than that of hole expansion, under the same strain gradient condition. Numerical prediction of the forming limit in the in-plane stretch bending was successful when the sheet edge condition was good.
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| Academic Significance and Societal Importance of the Research Achievements |
新たに提案した面内引張曲げ試験という伸びフランジ成形性評価試験により，板縁が凹型となる従来の穴広げ試験で得られた伸びフランジ成形限界のデータは板縁が凸型となる面内引張曲げ変形には適用できないことが示された．一方で面内引張曲げ試験においても従来の穴広げ試験と同様に縁割れ・縁割れの2種の破断形態があること，ひずみ勾配の増大に伴い伸びフランジ成形限界ひずみが増大すること，材料強度の上昇に伴い伸びフランジ成形限界ひずみが低下することなどが示された．これらの知見はプレス成形の現場における縁割れ評価法の改善，縁割れ予測精度の向上に寄与するものと考える．
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