2022 Fiscal Year Final Research Report
Microstructural modification and fatigue reliability improvement of flame-retardant Mg alloy FSW joints by shock waves generated by a pulsed laser
| Project/Area Number |
20K05109
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 26030:Composite materials and interfaces-related
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| Research Institution | Saitama Institute of Technology (2022)
Okinawa National College of Technology (2020-2021) |
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Principal Investigator |
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | 摩擦攪拌接合 / 難燃性マグネシウム / レーザピーニング / 表面改質処理 / 疲労特性評価 / ショットピーニング |
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| Outline of Final Research Achievements |
To use flame retardant magnesium alloys for mechanical structural components, it is essential to improve the fatigue strength at joint part. In this study, friction stir welding (FSW) was focused on and dry laser peening (Dry-LP) treatment was performed to the joints. Dry-LP is one of the surface modification techniques that uses a pulsed laser with a femtosecond pulse width. As the results of plane bending fatigue test, fatigue strength was improved by Dry-LP treatment. As investigation results of changes in microstructural properties, it was found that Dry-LP treatment could be improved the fatigue strength without significantly increasing of hardness. This tendency is different from one of conventional shot peening treatment which uses physical impact of shot media. This difference suggests the possibility that there is a new factor other than the general peening effect (compressive residual stress, hardness improvement) as a fatigue property improvement factor by Dry-LP treatment.
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| Free Research Field |
材料力学
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| Academic Significance and Societal Importance of the Research Achievements |
水を必要としないDry-LP処理によって，難燃性Mg合金のFSW継手の疲労特性改善が達成されたことは，難燃性Mg合金の幅広い機械構造部材への適用へとつながり，輸送機器の軽量化，省エネルギー化へとつながる．さらには，Dry-LP処理が従来のSP処理と比較してもクリーンな処理であるため，脱炭素社会の達成に大きく貢献する．また，Dry-LP処理では顕著な組織硬さの向上を伴うことなく，従来のSP処理以上の疲労特性改善効果が確認された．パルスレーザのパルス幅とピーニング効果の相関に関する学術的な調査は行われたことが無く，今後のLP処理研究に関する一つの大きな方針を示す研究成果となった．
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