Fatigue life evaluation method based on small fatigue crack opening closing behavior at notch root

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K04082
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 18010:Mechanics of materials and materials-related
• Research Institution: National Institute for Materials Science
• Principal Investigator: NISHIKAWA Hideaki 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 (20771843)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 金属疲労 / 微小疲労き裂 / 応力集中部 / 画像相関法

Outline of Final Research Achievements

Metal fatigue occurs due to repetition of loading and which is one of the major cause of industrial accidents. Although the fatigue crack usually initiate at the stress concentration area such as notch root, it was difficult to measure microscopic fatigue crack growth behavior of narrow notch root. This study presents evaluation method of such microscopic fatigue crack by using microscope system and digital image correlation (DIC) technique. This method enables us to measure small fatigue crack growth behavior includes its opening closing characteristics by evaluating crack opening displacement. This evaluation method was validated from the fatigue tests with notched fatigue specimen.

Free Research Field

材料力学

Academic Significance and Societal Importance of the Research Achievements

本研究によって考案した手法によって、応力集中部におけるミクロな疲労き裂の成長挙動と、き裂開口点の実測が可能となった。さらに、これらの実測データにより検証が可能になったことで、破壊力学による疲労き裂の成長解析によって、応力集中部の疲労破壊寿命の予測が可能となる目処が得られつつある。様々な部材の疲労寿命を高精度に予測するために必要となる、重要な知見が得られたと考えられる。