Investigation of secondary fracture mechanism at sheared edge of sheet metal through microstructure evaluation and FEM analysis

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H01757
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 26050:Material processing and microstructure control-related
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Takamura Masato 国立研究開発法人理化学研究所, 光量子工学研究センター, 上級研究員 (00525595)
• Co-Investigator(Kenkyū-buntansha): 松野 崇 鳥取大学, 工学研究科, 准教授 (30781687) ; 浜 孝之 京都大学, エネルギー科学研究科, 准教授 (10386633) ; 箱山 智之 岐阜大学, 工学部, 助教 (20799720) ; 北條 智彦 東北大学, 金属材料研究所, 助教 (50442463) ; 池田 義雅 国立研究開発法人理化学研究所, 光量子工学研究センター, 特別研究員 (80612142)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 高張力鋼板 / せん断加工 / 残留応力 / 遅れ破壊 / 陰極チャージ / 中性子回折 / 小型中性子源 / 飛行時間法

Outline of Final Research Achievements

Secondary fractures such as fatigue fracture or delayed fracture occurring in punched surface of sheet metals are becoming serious problems that should be under control. In this study, in-plane bending tests with the specimen with hydrogen concentrated by cathodic charging were conducted and the relationship between delayed fracture resistance and applied tensile stress was clarified.
In order to analyze the mechanisms of secondary fracture generation, newly developed FEM method for punching process was adopted.
Furthermore, measurement methods for texture and residual stress of the punched surface by neutron diffraction were developed by using a compact neutron source, which enable us to perform the on-site neutron diffraction at metal forming research site with the accuracy comparable to those with large neutron facilities.

Free Research Field

塑性加工学，金属組織学，中性子回折

Academic Significance and Societal Importance of the Research Achievements

自動車等の軽量化に欠かせない高張力鋼板を適用する上で，遅れ破壊や疲労破壊の問題は，車両の安全性を確保するために避けて通れない．本研究成果により，これら2次的破壊を引き起こすメカニズムを解明するための実験手法，解析手法，測定手法が確立された．すなわち，2次的破壊の問題を打ち抜き加工条件と関連付けて解明するための道具立てが整い，車両の安全性を確保しながら軽量化，低炭素化を進める技術的基盤づくりに寄与できた．