Comprehensive understanding of the mechanisms of hydrogen-assisted fatigue crack propagation in BCC steels based on hydrogen-dislocation interactions

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K23503
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0301:Mechanics of materials, production engineering, design engineering, fluid engineering, thermal engineering, mechanical dynamics, robotics, aerospace engineering, marine and maritime engineering, and related fields
• Research Institution: Kyushu University
• Principal Investigator: Ogawa Yuhei 九州大学, 工学研究院, 助教 (30847207)
• Project Period (FY): 2019-08-30 – 2021-03-31
• Keywords: 水素エネルギー / 水素脆化 / 鉄鋼材料 / 疲労き裂伝播 / 変形・破壊

Outline of Final Research Achievements

For the reliable design of pressure vessels and pipelines used for the storage and transportation of high-pressure gaseous hydrogen, mechanism-based understanding of the hydrogen-assisted acceleration of fatigue crack propagation in structural steels is required. In order to tackle this problem, systematic fatigue crack growth tests of a pure iron, as a model material, were performed under hydrogen gas environment with various pressure and temperature. By utilizing electron microscopy characterizations and crack growth retardation phenomenon after overloading, the roles of hydrogen on the deformation and fracture processes in the plastic-zone ahead of the crack-tip as well as on the plastic-zone size were elucidated.

Free Research Field

材料力学

Academic Significance and Societal Importance of the Research Achievements

水素エネルギー関連機器の普及拡大には高圧水素環境で使用される構造用金属の低コスト化が不可欠であり，そのために，現行材料であるオーステナイト系ステンレス鋼に対して安価な体心立方構造（BCC）鋼（炭素鋼，低合金鋼など）の積極的利用に期待が集まっている．BCC鋼の利用に向け，その水素脆化機構に関する学術基盤の構築が急がれているが，本研究ではその一環として疲労き裂進展加速現象に着目し，新たな重要知見を得ることに成功した．