scholarly journals Improvement in Fatigue Limit By Shot Peening for High-strength Steel Containing Crack-like Surface Defect － Influence of Stress Ratio －

2015 ◽  
Vol 2015 (60) ◽  
pp. 7-13
Author(s):  
Koji TAKAHASHI ◽  
Jun YASUDA ◽  
Hitonobu KOIKE ◽  
Hideki OKADA
Keyword(s):  
Fatigue Limit ◽  
Shot Peening ◽  
High Strength Steel ◽  
Surface Defect ◽  
Stress Ratio ◽  
High Strength

Improvement of Fatigue Limit by Shot Peening for High-Strength Steel Containing a Crack-Like Surface Defect: Influence of Stress Ratio

2012 ◽  
Author(s):  
Jun Yasuda ◽  
Koji Takahashi
Keyword(s):  
Fatigue Limit ◽  
Shot Peening ◽  
High Strength Steel ◽  
Stress Ratio ◽  
Structural Integrity ◽  
Fatigue Cracks ◽  
High Strength ◽  
Crack Size ◽  
Pressure Vessels ◽  
Circular Slit

It is well known that shot peening (SP) prevents the initiation and propagation of fatigue cracks and improves the fatigue limit of metals. It was recently reported that a surface crack can be rendered harmless by SP. Actual pressure vessels are generally operated under a positive stress ratio (R > 0). However, the effects of SP on the improvement of fatigue limits under R > 0 remain unclear. If these effects were clarified, the structural integrity of pressure vessels could be advanced. Thus, in this study, we investigated the influence of SP on fatigue limits and on the crack size that could be rendered harmless by SP under R > 0. High-strength steel specimens containing a semi-circular slit were subjected to SP. Bending fatigue tests were carried out under R = 0.4. The fatigue limits of the SP specimens increased 50∼100% compared with Non-SP specimens. Slits under 0.2 mm in depth were successfully rendered harmless by SP. The increasing ratios of the fatigue limit under R = 0.4 were lower than those under R = 0. However, the size of semi-circular slit that can be rendered harmless by SP remained the same. The size of the slit that can be rendered harmless can be predicted by calculating stress intensity factors.

Improvement of fatigue limit by shot peening for high-strength steel containing a crack-like surface defect

2014 ◽  
Vol 5 (1) ◽  
pp. 45-59 ◽  
Author(s):  
Jun Yasuda ◽  
Koji Takahashi ◽  
Hideki Okada
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fatigue Limit ◽  
High Strength Steel ◽  
Surface Defect ◽  
Stress Ratio ◽  
High Strength ◽  
Content Type ◽  
Circular Slit

Purpose – The purpose of this study is to clarify the influence of stress ratio (R) on the effects of shot peening (SP) on the fatigue limit of high-strength steel containing an artificial small defect. Design/methodology/approach – SP was subjected on the specimens with a semi-circular slit with a depth of a=0.1, 0.2 and 0.3 mm. Then, bending fatigue tests were carried out under R=0.4. Findings – The fatigue limits of specimens with a semi-circular slit were improved by SP under R=0.4. The fatigue limits of the SP specimens with a semi-circular slit under a=0.2 mm fractured outside the slit, and they had considerably high fatigue limits equal to specimens without a slit. Therefore, a semi-circular slit with a depth of under a=0.2 mm could be rendered harmless by SP under R=0.4. Compared to the results of R=0, the increasing ratios of fatigue limits under R=0.4 were lower than those under R=0. However, the size of semi-circular slit that could be rendered harmless by SP was same. In addition, it was found that whether the semi-circular slit is rendered harmless or not is decided by the relationship between the stress intensity factor range of semi-circular cracks and the threshold stress intensity factor regardless of stress ratio. Practical implications – The proposed method can be applied to mechanical parts used in vehicles, aircraft and trains. Originality/value – This is the first paper to investigate the fatigue limits after SP in materials containing a surface defect under positive stress ratio. In this study, the authors investigated the influence of stress ratio on the effects of SP on the fatigue limit containing a surface defects.

scholarly journals Improvement of Fatigue Limit by Shot Peening for High Strength Steel Specimens Containing a Crack-like Surface Defect

2009 ◽  
Vol 58 (12) ◽  
pp. 1030-1036 ◽  
Author(s):  
Koji TAKAHASHI ◽  
Toshihiko AMANO ◽  
Kazuya HANAORI ◽  
Kotoji ANDO ◽  
Fumio TAKAHASHI
Keyword(s):  
Fatigue Limit ◽  
Shot Peening ◽  
High Strength Steel ◽  
Surface Defect ◽  
High Strength

PS6 Effect of shot peening condition on acceptable surface defect size for high-strength steel

2010 ◽  
Vol 2010 (0) ◽  
pp. 15-17
Author(s):  
Daiki ITO ◽  
Koji TAKAHASHI ◽  
Kotoji ANDO ◽  
Hideki OKADA ◽  
Fumio TAKAHASHI
Keyword(s):  
Shot Peening ◽  
High Strength Steel ◽  
Surface Defect ◽  
High Strength ◽  
Defect Size
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