Study of nonlinear guided wave scattering by closed defects and its application to nondestructive evaluation

2021 Fiscal Year Final Research Report

• Project/Area Number: 19H02026
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 18010:Mechanics of materials and materials-related
• Research Institution: Kyoto University
• Principal Investigator: Biwa Shiro 京都大学, 工学研究科, 教授 (90273466)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 機械材料・材料力学 / 超音波 / 非破壊評価 / 密着欠陥 / ガイド波 / 高調波 / 周波数ミキシング

Outline of Final Research Achievements

The nonlinear scattering of ultrasonic guided waves by closed defects has been studied theoretically and experimentally with the aim to obtain basic insights into a novel principle of the nondestructive evaluation. Specifically, the harmonic generation of Lamb waves at a closed crack has been analyzed numerically, and it has been shown that the local resonance of the crack has significant influence on the harmonic generation behavior. Furthermore, the harmonic generation and the frequency mixing (generation of the sum and difference frequency components) of Lamb waves at a contacting interface and a fatigue crack of plates have been measured experimentally. It has been shown that the dispersive nature of Lamb waves is advantageous to discriminate the defect-induced nonlinear signals, and that it is possible to identify the presence and location of defects based on the mixed frequency signals measured by scanning the crossing zone of Lamb waves.

Free Research Field

固体力学

Academic Significance and Societal Importance of the Research Achievements

閉口き裂におけるラム波高調波発生に及ぼすき裂部共振の影響を詳細に明らかにしたこと、平板の突合せ接触部と疲労き裂に対してラム波高調波発生や周波数ミキシングを実験的に調べたことなど、まだ未解明の部分が多い密着欠陥によるガイド波非線形散乱挙動に関して理論的、実験的に興味深い結果を得たことに学術的意義がある。本研究の成果は、健全性の確保が社会的に重要な航空機や各種プラントで用いられる平板やシェルなどの薄肉部材に生じる欠陥を非破壊的かつ高感度に検出、評価する方法を充実させるための基礎的知見と位置付けられる。