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RISS 인기검색어
- 검색키워드
- 저자 : Mitsuru Handa (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Effects of Ultrasonic Peening on Fatigue Strength of Out-of-plane Gusset Joints
Koji Kinoshita,Akito Imamura,Yoshihiro Watanabe,Mitsuru Handa 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.4
Effect of high frequency peening treatment with a small radius tip pin, which is less than 3mm radius tip pin, still remainsunclear, although the effect of ultrasonic impact treatment on fatigue strength has been investigated. The objective of this studyis to investigate the effect of ultrasonic peening with a 1.5mm radius tip pin on fatigue strength of out-of-plane gusset weldedjoints. Plate bending fatigue tests of those joints carried out. The results show that the peening can improve fatigue strength,when mean stress does not change or already changes before the peening is carried out. It also shows that the effect of theultrasonic impact peening become less with increasing mean stress after the ultrasonic peening was carried out, and when theultrasonic peening is not sufficient for the weld toe.
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Fatigue Strength Improvement of Welded Joints of Existing Steel Bridges by Shot-Peening
Koji Kinoshita,Yuki Banno,Yuki Ono,Shohey Yamada,Mitsuru Handa 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.2
Shot-peening recently can be applied to existing steel bridges due to the development of new vacuuming techniques of shots after peening in the construction site. This study experimentally investigates eff ects of fatigue strength improvement of shot-peening on welded joints. Bending fatigue tests using out-of-plane gusset welded joints specimens were carried out and three type specimens were compared: as-welded, grit-blasted, and shot-peened. In addition, this paper examines diff erences of fatigue strength improvement eff ects in case of applying shot-peening to inside of scallop where shots might be diffi cult to hit perpendicularly to weld toe of welded joints because of narrow space, and the residual stress measurement in order to clarify introducing compressive residual stress were carried out. As a result, it may be concluded that shot-peening can improve fatigue strength of welded joints and its mechanism was identifi ed as extension of crack initiation life and delay crack propagation due to benefi cial compressive residual stress in the vicinity of surface layer.
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Koji Kinoshita,Yuki Banno,Yuki Ono,Shohey Yamada,Mitsuru Handa 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.3
This study experimentally investigates eff ect of fatigue strength improvement of the Portable Pneumatic Needle-Peening treatment (PPP treatment) as a needle peening on out-of-plane gusset welded joints by using plate bending fatigue tests. This study also examined eff ect of the travel speed and the number of treatment passes of the PPP treatment with regards to its fatigue strength improvement. After the fatigue tests, the observation of the fracture surface with Scanning Electron Microscope was carried out in order to clarify the crack initiation. From those test results, it may be concluded that the eff ect of fatigue strength improvement might be governed by treatment passes with suffi cient travel speed. In addition, this study carried out additional fatigue tests that focus on fatigue crack closer by using the PPP treatment. As a result of additional fatigue tests for fatigue crack closure, it might be said that the eff ect of fatigue crack closure is eff ective when the distance between fatigue cracks and treatment area is less than 2.0 mm.
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Evaluation of fatigue limit and harmless crack size of needle peened offshore structure steel F690
Min-Heon Kim,Won-Gu Lee,김철수,Koji Takahashi,Mitsuru Handa,Ki Woo Nam 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.9
In this study, a 0.4-1.6 mm deep semicircular crack was machined in DNV F690 offshore structural steel with an aspect ratio (As) of 1.0. After needle peening (NP), four-point bending fatigue tests were conducted. The fatigue limit estimated using the equation proposed by Ando et al. decreased with increasing crack size, but agreed with that obtained in the fourpoint bending fatigue test. The compressive residual stress increased the fatigue limit of the NP smooth and crack specimens. The fatigue limit of the NP crack specimen with a crack depth a = 0.8 mm was over 95 % of that of the smooth specimen. Semicircular cracks with crack depths up to a = 0.8 mm could be rendered harmless by NP, however, this was not the case for the NP crack specimen having a = 1.2 mm. It was estimated that the harmless crack depth of the NP crack specimen was a = 1.14 mm.
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