Surface Mechanics Design Using Laser Cavitation and Its Practical Application for 3D Additive Manufacturing Material

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H03138
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Materials/Mechanics of materials
• Research Institution: Tohoku University
• Principal Investigator: Soyama Hitoshi 東北大学, 工学研究科, 教授 (90211995)
• Co-Investigator(Kenkyū-buntansha): 伊賀 由佳 東北大学, 流体科学研究所, 教授 (50375119)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 機械的表面改質 / キャビテーション / レーザ / ３次元積層造形材 / 表面力学設計 / ピーニング

Outline of Final Research Achievements

When the surface of a metallic material placed in water was irradiated with a pulsed laser, ablation and bubble, i.e., laser cavitation were generated. In present study, laser cavitation was investigated and it was utilized for mechanical surface modification utilizing the impact force generated at bubble collapse. In normal underwater laser peening, the impact force by ablation is used. In this study, the impact force at laser cavitation collapse was enhanced by optimizing the processing conditions, and it was applied to a titanium alloy by additive manufacturing, and the fatigue strength of the titanium alloy improved 2 times. It was also demonstrated that this mechanical surface modification can improve fatigue strength to the same level or more with less than half the energy of conventional water film laser peening and less than half the pulse density.

Free Research Field

表面力学設計

Academic Significance and Societal Importance of the Research Achievements

学術的意義としては，独自に開発した荷重制御型平面曲げ式疲労試験機により，機械的表面改質による疲労強度向上における疲労亀裂の発生と疲労亀裂進展の影響を明らかにした。
社会的意義としては，金属製3次元積層造形材は，CADデータから直接造形できる，リードタイムが少ない，材料のロスが少ない，トポロジ最適化の形状を創成できるなどの利点があり，生体用インプラントや航空機部品への適用が期待されているが，疲労強度がバルク材よりも極端に小さいとの弱点がある。本機械的表面改質により，バルク材と同程度に疲労強度を向上できるので，本研究は金属製3次元積層造形材の実用化に貢献できる。