scholarly journals Quantitative Evaluation of Fatigue Limit of a Metal with an Arbitrary Crack under a Stress Controlled Condition. 1st Report. Stress Ratio=-1.

2002 ◽  
Vol 68 (673) ◽  
pp. 1352-1359 ◽  
Author(s):  
Tatsujiro MIYAZAKI ◽  
Hiroshi NOGUCHI ◽  
Keisaku OGI
Keyword(s):  
Fatigue Limit ◽  
Quantitative Evaluation ◽  
Stress Ratio

scholarly journals Effect of micro-notches on fatigue strength of electrodeposited nanocrystalline nickel thin films

2018 ◽  
Vol 165 ◽  
pp. 04011
Author(s):  
Keisuke Tanaka ◽  
Yuta Murase ◽  
Hirohisa Kimachi
Keyword(s):  
Thin Films ◽  
Fatigue Strength ◽  
Fatigue Limit ◽  
Stress Ratio ◽  
Fatigue Crack Initiation ◽  
Fatigue Tests ◽  
Fine Grained ◽  
Nickel Thin Films ◽  
Nano Crystalline ◽  
Fictitious Crack

The effect of micro-notches on the fatigue strength of nickel thin films was studied. Two types of thin films with 10 μm thickness were produced by electrodeposition using sulfamate solution without and with brightener: ultra-fine grained film (UFG) with the grain size of 384 nm and nano-crystalline grained film (NCG) with that of 17 nm. Micro-sized notches introduced by FIB had the width of 2 μm and various depths from 8 to 150μm. Fatigue tests were conducted under the stress ratio of 0.1. The fatigue strength decreased with increasing depth of notches. NCG had much higher strength than UFG compared at the same notch depth. Notches as small as 8μm did reduce the fatigue strength of both UFG and NCG. The fatigue limit was controlled by the initiation of cracks and no non-propagating crack was observed in specimens fatigued below the fatigue limit. A model of fictitious crack successfully predicted the reduction of the fatigue limit due to micro-notches. The characteristic crack length of NCG was much smaller than the UFG, while the fatigue strength of defect-free NCG was larger than that of UFG. SEM observation of fracture surfaces was conducted to reveal micromechanisms of fatigue crack initiation.

Estimation for fatigue limit reliability of a metal with inhomogeneities under stress ratio

2005 ◽  
Vol 47 (2) ◽  
pp. 230-250 ◽  
Author(s):  
Tatsujiro Miyazaki ◽  
Hiroshi Noguchi ◽  
Masaharu Kage ◽  
Ryoichi Imai
Keyword(s):  
Fatigue Limit ◽  
Stress Ratio

Effects of Residual Stresses on the High Cycle Fatigue Behavior of Ti-6Al-4V

2010 ◽  
Author(s):  
Yu-Jia Li ◽  
Fu-Zhen Xuan ◽  
Zheng-Dong Wang ◽  
Shan-Tung Tu
Keyword(s):  
Residual Stress ◽  
Fatigue Limit ◽  
Stress Ratio ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
X Ray Diffraction ◽  
Surface Residual Stress ◽  
Manufacturing Techniques ◽  
Stress Ratios ◽  
Effect Of Surface

Axial force-controlled fatigue tests are conducted at various stress ratios (R) on Ti-6Al-4V specimens prepared by two different manufacturing techniques (hard turning plus polishing with and without vacuum stress relieve anneal carried out after polishing). Residual stress is measured by using X-ray diffraction. Results indicate that the surface compressive residual stress lead to an increase of fatigue limit at a given life and stress ratio. This effect decreases with increasing stress ratio R. At R = 0.6, the effect of surface residual stress on fatigue limit fades away. In addition, the location of crack initiation shifts from surface to interior when the stress ratio changes from −1 to 0.6.

The Experimental Study of 15CrMo Steel Fatigue Performance

2013 ◽  
Vol 716 ◽  
pp. 214-217
Author(s):  
Meng Yuan Gu ◽  
Xiao Yang Li ◽  
Hui Ping Yu
Keyword(s):  
Fatigue Limit ◽  
Stress Ratio ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Axial Loading ◽  
Fatigue Performance ◽  
Analysis Method ◽  
Limit Theory ◽  
Theoretical Support ◽  
Limit Analysis Method

15CrMo steel is widely used in engineering. In order to evaluate the fatigue performance of 15CrMo, axial loading for 15CrMo specimen has applied by high frequency fatigue testing machine under stress ratio R=0.1 at room temperature, the linear S-N relationship has obtained by grouping fatigue test, the fatigue limit has obtained and compared by two different fatigue limit analysis method. The consequences of this test could provide a theoretical support for the use of 15CrMo in engineering and the research of fatigue limit theory.

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.

Evaluation of Conventional Al 2024 Fatigue Limit in Fatigue Test Using Thermographic Measurement: Effect of Frequency

2014 ◽  
Vol 891-892 ◽  
pp. 1308-1313
Author(s):  
Stanislav Seitl ◽  
Jan Klusák ◽  
Fernández Pelayo ◽  
Alfonso Canteli
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Limit ◽  
Fatigue Test ◽  
Stress Ratio ◽  
Load Control ◽  
Practical Applications ◽  
Thermographic Measurement ◽  
Al 2024

The reliability of the conventional fatigue limit estimation of aluminum alloy Al 2024 provided by thermographic measurements according to the Risitano method is investigated in order to check their validity for practical applications. With this aim, an experimental fatigue program on Al 2024 specimens under load control using a stress ratio R = 0.1 is performed at three different frequencies. The fatigue limit methodologies is first determined according to the methodologies proposed by Risitano et al. and Canteli et al., and then compared with that resulting from the conventional Wöhler curve.

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