Linking the relationship between dislocation-plastic deformation-crack through multi-scale observation of fatigue damage

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K14853
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 18010:Mechanics of materials and materials-related
• Research Institution: National Institute for Materials Science
• Principal Investigator: YOSHINAKA Fumiyoshi 国立研究開発法人物質・材料研究機構, 構造材料研究拠点, 主任研究員 (00825341)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 金属疲労 / 疲労寿命 / 疲労き裂 / 合金設計 / マルテンサイト変態 / 疲労破面解析

Outline of Final Research Achievements

The relationship between dislocation-plastic deformation-crack in high Mn steel was investigated. As a result, the fatigue life is maximized when a bidirectional γ→ε→γ transformation (B-TRIP) occurs between γ austenite and ε martensite as a plastic deformation mechanism. This indicates that high deformation reversibility can improve the fatigue life. Additionally, the practical B-TRIP steel with high fatigue durability and weldability was developed. Furthermore, this research demonstrated the importance of suppressing α' martensite transformation as a condition to maximize the improvement in fatigue durability through B-TRIP. A new steel was developed so as to meet this condition and exhibits twice the fatigue life compared to existing B-TRIP steel.

Free Research Field

金属疲労

Academic Significance and Societal Importance of the Research Achievements

本研究では材料の塑性変形を制御し変形可逆性を高めるという発想に基づき耐疲労鋼材の合金設計指針を確立した。低サイクル疲労の考慮を要する有限寿命設計が適用される場合について、本研究が可能とした疲労寿命の改善は部材・施設の長寿命化に寄与する。また、疲労耐久性に加え、構造体化に重要な溶接適合性を改善した合金を開発したことは、研究成果を社会に還元するための取り組みとして意義深い。本研究成果は構造用金属材料の長寿命化の実現により、公共施設等の老朽化対策においてライフタイムコストの削減に寄与しうるものである。