Determination Method of Reference Lattice Constants to Improve Accuracy of Neutron Stress Measurement

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K04185
• 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: Tokyo City University
• Principal Investigator: Akita Koichi 東京都市大学, 理工学部, 教授 (10231820)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 中性子回折 / 残留応力測定 / 基準格子定数 / 応力解放

Outline of Final Research Achievements

When measuring the stress state of crystalline structural materials using neutron diffraction, it is required to determine the reference lattice spacing (d0) under stress-free conditions for the measured sample. However, there is currently no standardized method for determining d0. In this study, various factors influencing the experimental value of d0 were investigated. As a result, it was clarified through experiments and analyses that wire electrical discharge machining is suitable for the fabrication of comb-shaped test specimens used for d0 measurements. Additionally, it was determined that the appropriate width of the tooth width of the comb sample for stress relief direction should be 3 mm or less. These findings provide important insights towards standardizing the preparation of d0 measurement specimens.

Free Research Field

材料強度

Academic Significance and Societal Importance of the Research Achievements

産業界において中性子による残留応力測定ニーズが特に高い溶接部では、溶接時の原子拡散のために基準格子定数が空間的に分布するため、応力除去焼きなましを施しても無応力状態が得られない。この対策として試料に細かい切り込みを導入することで応力を解放させたいわゆる櫛状試験片が用いられている。しかし、この試験片の適切な準備方法が確立されていないという問題があった。本研究では、d0測定における種々の影響因子を実験及び数値解析的に明らかにし、応力解放させる方向の切り込み幅（櫛の歯幅）は3㎜以下が適切であることなどを明らかにし、d0測定用試料の標準化に向けた重要な知見を得た。