Fatigue Crack Growth Threshold Concept and Test Results for Al- and Ti-Alloys PDF Download
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Author: G. Marci Publisher: ISBN: Category : Fatigue crack propagation Languages : en Pages : 15
Book Description
The fact that fatigue crack propagation (FCP) rates approach zero asymptotically as the fracture mechanics loading parameter ?K decreases toward certain limiting values is the reason for the scientific interest in these so-called 'threshold' values. In respect to the practical use of these 'limiting values', the author divides them into two groups, namely in 'non-propagation conditions' ?Kth and in a material property 'FCP-threshold' ?KT. It is shown that ?KT must be an integral part in the functional correlation between FCP-rates and the cyclic loading conditions expressed in ?Keff. The experimental determination of ?Kth on six Al-alloys and four Ti-compressor disk alloys show that ?KT exists for all the alloys investigated. The effect of temperature on ?KT was investigated on one Ti 6Al 4V- and one Ti 8Al 1V 1Mo disk material at room temperature (RT) and 260°C and at RT, 260°C and 360°C, respectively. No temperature effect on ?KT was found for the temperature range investigated.
Author: G. Marci Publisher: ISBN: Category : Fatigue crack propagation Languages : en Pages : 15
Book Description
The fact that fatigue crack propagation (FCP) rates approach zero asymptotically as the fracture mechanics loading parameter ?K decreases toward certain limiting values is the reason for the scientific interest in these so-called 'threshold' values. In respect to the practical use of these 'limiting values', the author divides them into two groups, namely in 'non-propagation conditions' ?Kth and in a material property 'FCP-threshold' ?KT. It is shown that ?KT must be an integral part in the functional correlation between FCP-rates and the cyclic loading conditions expressed in ?Keff. The experimental determination of ?Kth on six Al-alloys and four Ti-compressor disk alloys show that ?KT exists for all the alloys investigated. The effect of temperature on ?KT was investigated on one Ti 6Al 4V- and one Ti 8Al 1V 1Mo disk material at room temperature (RT) and 260°C and at RT, 260°C and 360°C, respectively. No temperature effect on ?KT was found for the temperature range investigated.
Author: J. C. Newman Publisher: ASTM International ISBN: 0803126247 Category : Fatigue Languages : en Pages : 436
Book Description
Annotation Contains 24 papers from the November, 1998 symposium of the same name, sponsored by the ASTM Committee E8 on Fatigue and Fracture, and presented by Newman and Piascik (both of the NASA Langley Research Center). The papers focus on such areas as fatigue-crack growth threshold mechanisms, loading and specimen-type effects, analyses of fatigue-crack-growth-threshold behavior, and applications of threshold concepts and endurance limits to aerospace and structural materials. Annotation copyrighted by Book News, Inc., Portland, OR.
Author: David L. Davidson Publisher: Society for Mining Metallurgy & Exploration ISBN: 9780895204752 Category : Technology & Engineering Languages : en Pages : 584
Author: John J. Ruschau Publisher: ISBN: Category : Aluminum Languages : en Pages : 15
Book Description
The scope of this paper is to determine the fatigue-crack growth rates in the near-threshold regime for both an aluminum and titanium alloy using the compression precracking constant-amplitude (CPCA) test method on compact specimens. Tests were conducted over a wide range of stress ratios (R=Pmin/Pmax=0.1 to 0.9). Results were compared with threshold and near-threshold data generated on the same materials using the ASTM E647, "Standard Test Method for Measurement of Fatigue Crack Growth Rates," load-shedding test procedure. On the 7075-T651 alloy, very little difference was observed in threshold values between the load-shedding and CPCA test methods. In contrast, the titanium alloy (Ti-6Al-4V) showed very large differences between the CPCA and load-shedding test results in the near-threshold and threshold regimes for the low stress ratios. Results under high R conditions (R>=0.7) agreed well between the two-threshold test methods for both materials. On the titanium alloy, the load-shedding test method also produced a specimen width effect on near-threshold behavior, whereas the CPCA test method produced results that were independent of specimen width and produced "steady-state" constant-amplitude data in the near-threshold regime, after the crack had grown several compressive plastic-zone sizes.
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781721587025 Category : Languages : en Pages : 28
Book Description
Constant-Kmax fatigue crack growth tests were performed on two finegrain nickel-base alloys Inconel 718 (DA) and Ren 95 to determine if these alloys exhibit near-threshold time-dependent crack growth behavior observed for fine-grain aluminum alloys in room-temperature laboratory air. Test results showed that increases in K(sub max) values resulted in increased crack growth rates, but no evidence of time-dependent crack growth was observed for either nickel-base alloy at room temperature. Newman, John A. and Piascik, Robert S. Langley Research Center NASA/TM-2003-212443, NAS 1.15:212443, L-18314, ARL-TR-3021
Author: A. J. McEvily Publisher: ISBN: Category : Languages : en Pages : 13
Book Description
The report summarizes the research accomplishments in the first year's program of a study of fatigue crack growth in Ti-6Al-4V alloys. Fatigue crack growth rates have been determined in the mean threshold regions, and data for the effect of mean stress on the threshold level indicate that the dependency may be interpretable in terms of a constrant crack opening criterion. Additional work on high cycle fatigue indicates that there are two regions for the Coffin-Manson relation and that cyclically developed residual stresses may be responsible for this behavior.
Author: G. Marci
Author: G. Marci
Author: J. C. Newman
Author: David L. Davidson
Author: John J. Ruschau
Author: National Aeronautics and Space Administration (NASA)
Author: David Taylor
Author: A. J. McEvily
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