Development of fatigue damage evaluation in the early stage using X-ray diffraction

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K14848
• 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: Tokyo City University
• Principal Investigator: Kumagai Masayoshi 東京都市大学, 理工学部, 准教授 (20582498)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 低サイクル疲労 / 疲労損傷 / 転位組織 / X線回折 / 中性子回折 / ラインプロファイル解析

Outline of Final Research Achievements

Neutron diffraction was used to study dislocation structure in austenitic stainless steel exposed to low cycle fatigue. Dislocation character and arrangement parameter, as well as dislocation density, were determined to show morphological aspects of dislocation structure that changed with cyclic loading. Its morphology can be predicted by combining those parameters. Furthermore, even though the material was work hardened in macroscopically, it was work softened after work hardening in the austenite. In the latter stage, deformation-induced-transformation formed martensite and the phase shared stress. Overall, it has been demonstrated that X-rays and neutron diffraction are useful techniques for assessing fatigue damage.

Free Research Field

材料強度評価

Academic Significance and Societal Importance of the Research Achievements

機械構造物を設計する際にはその疲労寿命を予測し、使用期間中に破壊に至らない様に設計されるが、実使用環境においては予想外の負荷が加わるなど必ずしも予測通りの寿命とはならない。そのため、実際の部材の状態を評価し、安全性を担保することが欠かせない。そのため疲労損傷評価・余寿命予測などが行われるが既存の検査・評価手法は使用中の部材の疲労損傷評価はき裂の検出などによる方法がほとんどである。本研究で用いたX線や中性子回折を用いた材料の微視組織評価にもとづく方法が実用化されれば、き裂発生前段階の疲労損傷評価法として経済性安全性の観点から社会に貢献が期待できる。