Improving reliability of high‐strength steel designed against fatigue limit using surface crack nondamaging technology by shot peening

2021 ◽  
Vol 44 (6) ◽  
pp. 1602-1610
Author(s):  
Ki‐Woo Nam ◽  
Kotoji Ando ◽  
Min‐Heon Kim ◽  
Koji Takahashi
Keyword(s):  
Fatigue Limit ◽  
Surface Crack ◽  
Shot Peening ◽  
High Strength Steel ◽  
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.

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

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

2013 ◽  
Author(s):  
Makiko Nakagawa ◽  
Koji Takahashi ◽  
Toshio Osada
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Aspect Ratio ◽  
Intensity Factor ◽  
Fatigue Limit ◽  
Shot Peening ◽  
High Strength Steel ◽  
High Strength ◽  
Bending Fatigue ◽  
Aspect Ratios

The effect of shot peening (SP) on the bending fatigue limit of high-strength steel (SUP9A) containing a semi-elliptical surface slit was investigated. SP was conducted on specimens containing a semi-elliptical surface slit with an aspect ratio (a/c) of 0.4, where a was the crack depth (a = 0.1, 0.2, and 0.3 mm) and c was half the surface length of the crack. Bending fatigue tests were carried out under a stress ratio R equal to 0. The results showed that the fatigue limit of the shot-peened specimens with slits having a depth of less than 0.2 mm was almost the same as that of the shot-peened specimens without slits. Meanwhile, some of the specimens fractured at the surface in areas other than the slit. Thus, the maximum depth of the slit that could be rendered harmless by SP was 0.2 mm. The maximum depths of cracks with various aspect ratios that could be rendered harmless by SP were predicted, assuming that the cracks were arrested when the apparent stress intensity factor at the slit tip was less than the threshold stress intensity factor of the material. The estimated values were in good agreement with the experimental values. A harmless crack assessment diagram was proposed based on this estimation method.

Increasing the fatigue strength of high-strength steel parts by repeated treatment with shot peening

2020 ◽  
pp. 79-82
Author(s):  
G.N. Kravchenko ◽  
K.G. Kravchenko
Keyword(s):  
Fatigue Strength ◽  
Shot Peening ◽  
High Strength Steel ◽  
High Strength ◽  
Resource Recovery ◽  
Repeated Treatment ◽  
Multiple Processing

The effectiveness of multiple hardening by shot peening of samples made of «30ХГСН2А» high-strength steel to increase their fatigue strength is experimentally established. Repeated hardenings allow not only to restore the original durability and even significantly increase it. Keywords fatigue strength, durability, resource recovery, multiple processing by shot peening, repeated hardening, high-strength steel. [email protected]

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