Experience with Automated Fatigue Crack Growth Experiments

2008 ◽  
pp. 132-132-16 ◽  
Author(s):  
WA Van Der Sluys ◽  
RJ Futato
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Experiments

Development of Fatigue Crack Growth Thresholds for Austenitic Stainless Steels Exposed to Air Environment for ASME Code Section XI

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Kunio Hasegawa ◽  
Saburo Usami
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Stainless Steels ◽  
Stress Ratio ◽  
Austenitic Stainless Steels ◽  
Stress Intensity Factor Range ◽  
Asme Code ◽  
American Society ◽  
Growth Experiments

Fatigue crack growth thresholds ΔKth define stress intensity factor range below which cracks will not grow. The thresholds ΔKth are useful in industries to determine durability lifetime. Although massive fatigue crack growth experiments for stainless steels in air environment had been reported, the thresholds ΔKth are not codified at the American Society of Mechanical Engineers (ASME) Code Section XI, as well as other fitness-for-service (FFS) codes and standards. Based on the investigation of a few FFS codes and review of literature survey of experimental data, the thresholds ΔKth exposed to air environment have been developed for the ASME Code Section XI. A guidance of the thresholds ΔKth for austenitic stainless steels in air at room and high temperatures can be developed as a function of stress ratio R.

The Effect of a Dwell Period on Fatigue Crack Growth Rates in Filled SBR and NR

2007 ◽  
Vol 80 (5) ◽  
pp. 838-853 ◽  
Author(s):  
Ryan J. Harbour ◽  
Ali Fatemi ◽  
Will V. Mars
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Growth Rates ◽  
Material Characterization ◽  
Loading Conditions ◽  
Constant Amplitude ◽  
Crack Growth Rates ◽  
Growth Experiments ◽  
Dwell Period

Abstract Loading conditions for rubber components are often more complex than the constant amplitude signals used in material characterization. During a series of uniaxial fatigue crack growth experiments on filled SBR under variable amplitude loading conditions, test signals that included a dwell period produced higher crack growth rates than corresponding constant amplitude test signals without a dwell period. These test signals alternated periods of cyclic loading with dwell periods ranging from 1 to 100 seconds at a near zero stress level. Dwell period tests produced average experimental crack growth rates up to 30 times greater than constant amplitude crack growth rates in filled SBR. The length of dwell time and the number of applied cycles between dwell periods were the most significant influences on the crack growth results. An empirical model was developed that captured the dwell effect based on these parameters. Dwell periods also produced increased crack growth rates in natural rubber, but the effect was less significant. It is proposed that the effect is caused by the time-dependent recovery in the rubber microstructure at the crack tip producing a localized and temporary elevated stress-state during loading events immediately following a dwell period. Current fatigue prediction methods do not account for the dwell effect.

An Experiment of Fatigue Crack Growth under Different R-Ratio for 2024-T4 Aluminum Alloy

2011 ◽  
Vol 66-68 ◽  
pp. 1477-1482 ◽  
Author(s):  
Guang Yang ◽  
Zeng Liang Gao ◽  
Feng Xu ◽  
Xiao Gui Wang
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Great Influence ◽  
Ambient Air ◽  
Compact Tension ◽  
Growth Region ◽  
Paris Law ◽  
Growth Experiments

The fatigue crack growth tests of compact tension (CT) specimens of 2024-T4 aluminum alloy were conducted under constant amplitude loading with differentR-ratios, 0.05, 0.1, 0.5, 0.75, respectively. The thickness of the specimen is 3.8mm. All the fatigue crack growth experiments were carried out in ambient air without a pre-crack. The early crack growth region reflects the influence of the notch. An optical reading micrometer with a magnification of 40 was used to measure the crack length. The size of the notch together with the loading conditions has a great influence on the early crack growth within the notch influenced region. Beyond the notch influenced zone, the stable fatigue crack growth is reached and can be characterized by the Paris law. The experimental results indicate that fatigue crack growth rate increases with theR-ratio for a given stress intensity factor amplitude.

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