| 号数 | ばね論文集 65 号（ 2020 年） |
| ページ数 | pp.21-25 |
| 種類 | 論文 |
| 論文名 | 超音波ショットピーニングによる高強度鋼の疲労特性の改善と無害化 |
| Title | Improvement of Fatigue Properties and Making Surface Defect Harmless for High Strength Steel by Ultrasonic Shot Peening |
| 著者 | 岡田秀樹1)，高橋宏治2) |
| Author | Hideki OKADA1), Koji TAKAHASHI2) |
| 抄録 | ショットピーニング（SP）による高強度鋼(SUP9A)の表面欠陥の無害化に対する圧縮残留応力深さの影響を調査するために，より深い圧縮残留応力が導入できる超音波ピーニング（UP）を行った．これまで半円スリットの深さが0.2mm以下のSP材の疲労限度はSPを施した無欠陥材の疲労限度と同等の値にまで向上した．そこでSPの無害化可能欠陥寸法0.2mmよりも大きくできるかどうか表面き裂を模擬した深さ0.2,0.3.0.4mmの半円スリットを有する試験片を用いて応力比R=0の条件で平面曲げ疲労試験を行った．その結果，UPの無害化可能欠陥寸法は0.4mmまで向上した．本実験結果と応力拡大係数を用いた無害化可能欠陥寸法の予測値は整合した． |
| Abstract | It has been reported that the fatigue limit of shot peened high strength steels with a semicircular slit of 0.2 mm or less in depth was improved to the same value as that of defect-free shot peened specimens. In this study ultrasonic shot peening （UP） which can introduce deeper compressive residual stress was noticed in order to investigate the effect of the depth of compressive residual stress on the size of surface defect that can be rendered harmless by peening. After UP was applied to the specimens of spring steel （SUP9A） with semicircular slits of 0.2, 0.3 and 0.4 mm in depth, plane bending fatigue tests were carried out under the condition of stress ratio R = 0. As the result, it was clari ed that the defect size that can be rendered harmless by UP was at least 0.4 mm. In other words, it was found that increasing the depth of compressive residual stress is effective in increasing the size of defect that can be rendered harmless. In addition, the predicted size of the defect rendered harmless by UP based on the stress intensity factor was consistent with the experimental results. |
| 著者の所属 | 1)日本発条株式会社 2)横浜国立大学大学院 |
| Belonging | 1)NHK SPRING Co., Ltd. 2)Yokohama National University |
| Key Words | Ultrasonic shot peening, Surface defect, Bending fatigue strength, Fracture mechanics, Residual stress |