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Mean Stress And Environmental Effects On Near Threshold Fatigue Crack Propagation On A Ti6246 Alloy At Room Temperature And 500c
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Book Synopsis Mean Stress and Environmental Effects on Near-Threshold Fatigue Crack Propagation on a Ti6246 Alloy at Room Temperature and 500°C by : C. Sarrazin-Baudoux
Download or read book Mean Stress and Environmental Effects on Near-Threshold Fatigue Crack Propagation on a Ti6246 Alloy at Room Temperature and 500°C written by C. Sarrazin-Baudoux and published by . This book was released on 2000 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: The cracking behavior of a Ti6246 alloy under cyclic loading superimposed to different levels of mean stress is studied, with special attention to the near-threshold fatigue crack propagation regime, and to possible coupled effects of corrosion and creep. Tests were conducted at room temperature and 500°C in selected environmental conditions (high vacuum, controlled atmospheric leak low pressure, controlled partial pressure of water vapor in pure argon) and at different frequencies. The near-threshold crack propagation at low Kmax (i.e. low R ratio) is shown to be highly sensitive to the environment, and a predominant detrimental influence of water vapor is observed, even under very low partial pressure. Conditions for the occurrence of an abnormal behavior consisting in the disappearance of the threshold for sufficiently high Kmax level, are discussed from tests performed at various constant Kmax levels in ambient air, high vacuum and humidified argon. This effect is observed in air and in vacuum for Kmax higher than 52 MPa?m, and is related to an intrinsic creep damage process which appears more efficient at room temperature than at 500°C and more accentuated in air than in vacuum. The origin of this abnormal near-threshold behavior is discussed in comparison with a similar behavior described in the literature at room temperature on another type of Ti6246 alloy and at 120°C on an IMI834. Additional experiments conducted at 500°C in humidified argon have shown a critical Kmax level reduced to 22 MPa?m. This behavior is suspected to be related to a contribution of stress corrosion cracking induced by water vapor when some conditions favoring a localization of the deformation and the attainment of a critical embrittlement are fulfilled.
Book Synopsis Mean Stress and Environmental Effects on Near Threshold Fatigue Crack Growth by : J. Mautz
Download or read book Mean Stress and Environmental Effects on Near Threshold Fatigue Crack Growth written by J. Mautz and published by . This book was released on 1976 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of mean stress and environment on the threshold and near threshold fatigue crack propagation behavior has been studied for D6ac steel and for 7050-T73651 aluminum. Fatigue crack propagation experiments were conducted in the range of 10-7 to 10-9 in./cycle (2.5 x 10-9 to 2.5 x 10-11 m/cycle) at 375 Hz.
Book Synopsis International Aerospace Abstracts by :
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 682 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Environmentally Affected Near-Threshold Fatigue Crack Growth in Steels by : S. Suresh
Download or read book Environmentally Affected Near-Threshold Fatigue Crack Growth in Steels written by S. Suresh and published by . This book was released on 1983 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: Environmentally affected fatigue crack propagation in steels is described for ultralow growth rates (below 10-6 mm/cycle) in terms of the role of crack surface corrosion debris in promoting crack closure. It is shown that the reported effects of gaseous and aqueous environments (air, water, hydrogen, helium, etc.) on near-threshold crack growth in lower strength steels are consistent primarily with an oxide-induced crack closure mechanism. Moist atmospheres, such as humid air and water, are shown to promote the formation of oxide deposits within the crack, which at low load ratios are thickened by fretting-assisted oxidation to maximum thicknesses comparable with cracktip opening displacements. Using ultrasonic techniques, this is shown to increase closure loads and to lower effective alternating stress intensities at the crack tip. Observations that near-threshold growth in dry helium is similar to that in dry hydrogen gas and faster than in air, are shown to be consistent with such concepts since both environments provide a dry atmosphere limiting oxide formation. Extensive data on near-threshold corrosion-fatigue crack growth in ultrahigh-strength (300-M) and lower-strength (21⁄4Cr-1Mo and SA516) steels are examined in the context of this mechanism, and it is found that the threshold for no crack growth (?Ko) is consistent with a maximum excess oxide thickness approximately equal to the pulsating crack-tip displacement (?CTOD). The implications of this and other microscopic mechanisms of closure are discussed in the light of microstructural and environmental influences on near-threshold fatigue.
Book Synopsis Environment Enhanced Fatigue Crack Propagation in Metals: Inputs to Fracture Mechanics Life Prediction Models by : Richard P. Gangloff
Download or read book Environment Enhanced Fatigue Crack Propagation in Metals: Inputs to Fracture Mechanics Life Prediction Models written by Richard P. Gangloff and published by . This book was released on 1993 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effect of Low Temperature on Apparent Fatigue Threshold Stress Intensity Factors by : KA. Esaklul
Download or read book Effect of Low Temperature on Apparent Fatigue Threshold Stress Intensity Factors written by KA. Esaklul and published by . This book was released on 1985 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Near-threshold fatigue crack growth in high-strength low-alloy (HSLA) steel, Fe, and Fe-Si alloys was found to depend on test temperature from room temperature down to 123 K. Near-threshold crack growth rates were lowered and threshold stress intensity factors increased with decreasing temperature. A "prominent" closure was observed for all test temperatures and materials and was further confirmed by the examination of fracture surfaces. The magnitude of closure increased with decreasing temperature, suggesting a dependence on yield strength and fracture morphology. The effects of R ratio were found to be closure-related for the same fracture processes. However, a change in the fracture process, (e.g., to cyclic cleavage) may lead to a ?Kth(eff) dependence on load ratio even at very high R values. Hence mean stress may affect threshold independently of any closure-related phenomena. A reasonable correlation was obtained with a theoretical model for closure that could account for both geometrical and reversed plasticity phenomena.
Author :National Aeronautics and Space Administration (NASA) Publisher :Createspace Independent Publishing Platform ISBN 13 :9781721587025 Total Pages :28 pages Book Rating :4.5/5 (87 download)
Book Synopsis Near-Threshold Fatigue Crack Growth Behavior of Fine-Grain Nickel-Based Alloys by : National Aeronautics and Space Administration (NASA)
Download or read book Near-Threshold Fatigue Crack Growth Behavior of Fine-Grain Nickel-Based Alloys written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-20 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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
Book Synopsis A Review of Fatigue Crack Growth in Metallics at Low Stress Intensities by : C. J. Beevers
Download or read book A Review of Fatigue Crack Growth in Metallics at Low Stress Intensities written by C. J. Beevers and published by . This book was released on 1983 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: This review is concerned with the fatigue crack growth response of metallics at low stress intensities. In particular the fatigue threshold e.g. the stress intensity at which cracks can arrest is considered in detail. The fatigue crack growth rates and the fatigue threshold stress intensity delta K/th are considered in relation to the following variables, mean stress, yield stress, test temperature, test frequency, fatigue crack closure, microstructure, environment and crack length. The mechanisms, models and formulations derived to represent fatigue crack growth at low stress intensities and the fatigue threshold are also reviewed. The measurement of fatigue crack growth rates and fatigue thresholds is outlined and the desirability of obtaining delta K/eff data is highlighted. The main characteristics of aluminum alloys, steels and titanium alloys with respect to fatigue crack growth and fatigue thresholds are presented. A conservative view of the fog resistance of metals and alloys is developed which allows the identification of the minimum fatigue threshold and maximum fog rates that can be experienced for a particular set of test conditions. (Author).
Author :National Aeronautics and Space Adm Nasa Publisher :Independently Published ISBN 13 :9781724083333 Total Pages :26 pages Book Rating :4.0/5 (833 download)
Book Synopsis Accelerated Near-Threshold Fatigue Crack Growth Behavior of an Aluminum Powder Metallurgy Alloy by : National Aeronautics and Space Adm Nasa
Download or read book Accelerated Near-Threshold Fatigue Crack Growth Behavior of an Aluminum Powder Metallurgy Alloy written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-09-27 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue crack growth (FCG) research conducted in the near threshold regime has identified a room temperature creep crack growth damage mechanism for a fine grain powder metallurgy (PM) aluminum alloy (8009). At very low DK, an abrupt acceleration in room temperature FCG rate occurs at high stress ratio (R = Kmin/Kmax). The near threshold accelerated FCG rates are exacerbated by increased levels of Kmax (Kmax less than 0.4 KIC). Detailed fractographic analysis correlates accelerated FCG with the formation of crack-tip process zone micro-void damage. Experimental results show that the near threshold and Kmax influenced accelerated crack growth is time and temperature dependent. Piascik, Robert S. and Newman, John A. Langley Research Center NASA/TM-2002-211676, L-18180, NAS 1.15:211676, ARL-TR-2728
Book Synopsis Accelerated Near-Threshold Fatigue Crack Growth Behavior of an Aluminum Powder Metallurgy Alloy by :
Download or read book Accelerated Near-Threshold Fatigue Crack Growth Behavior of an Aluminum Powder Metallurgy Alloy written by and published by . This book was released on 2002 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effects of Strength and Grain Size on Near-threshold Fatigue Crack Growth in Ultra-high Strength Steel by :
Download or read book Effects of Strength and Grain Size on Near-threshold Fatigue Crack Growth in Ultra-high Strength Steel written by and published by . This book was released on 1976 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue tests were performed on ultra-high strength steels to assess (i) the influence of strength at constant grain size, and (ii) the influence of grain size at constant strength, on threshold stress intensity and near-threshold crack propagation rates. The results constitute part of a larger program of research to characterize the microstructural influences on fatigue crack propagation at growth rates less than 10−5 mm/cycle in an attempt to provide a basis for the design of alloys resistant to low growth rate fatigue failure.
Book Synopsis Fatigue-crack Propagation in Several Titanium and Stainless-steel Alloys and One Superalloy by : C. M. Hudson
Download or read book Fatigue-crack Propagation in Several Titanium and Stainless-steel Alloys and One Superalloy written by C. M. Hudson and published by . This book was released on 1964 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fatigue Crack Propagation in Titanium Alloys by : A. J. McEvily
Download or read book Fatigue Crack Propagation in Titanium Alloys written by A. J. McEvily and published by . This book was released on 1975 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Influence of Crack Closure and Stress Ratio on Near-Threshold Fatigue Crack Growth Behavior in Ti-1100 by : T. Nicholas
Download or read book Influence of Crack Closure and Stress Ratio on Near-Threshold Fatigue Crack Growth Behavior in Ti-1100 written by T. Nicholas and published by . This book was released on 1994 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the present study, the fatigue crack growth behavior of a near-?, ?-processed titanium alloy, Ti-1100, was investigated with the objective of assessing the influence of crack closure and stress ratio on fatigue threshold. Measurement of the crack-opening load in single-edge tension [SE(T)] specimens was made by near-tip strain gage and DCPD methods. Fatigue threshold stress intensity ranges, ?Kth, determined under constant stress ratio and constant maximum stress intensity, variable stress ratio conditions indicate almost identical values for R above 0.5. It is postulated that while crack closure in the wake of the crack tip is responsible for the no-growth condition in the former case, lack of sufficient damage accumulation at the crack tip as a consequence of the formation of an insignificant reversed plastic zone and large planar slip band formations surrounding the crack tip appears to be responsible for no growth in the latter case. The use of an effective stress intensity based on closure data consolidates most of the threshold data, indicating the independence of the fatigue crack growth data to mean stress or R.
Book Synopsis Sourcebook on Fatigue Crack Propagation by : David Taylor
Download or read book Sourcebook on Fatigue Crack Propagation written by David Taylor and published by . This book was released on 1993 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Elevated Temperature Effects on Fatigue and Fracture by : Robert S. Piascik
Download or read book Elevated Temperature Effects on Fatigue and Fracture written by Robert S. Piascik and published by ASTM International. This book was released on 1997 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Elevated Temperature, Near-threshold Fatigue Crack Propagation in Aluminum Alloys by : Mark Leo Renauld
Download or read book Elevated Temperature, Near-threshold Fatigue Crack Propagation in Aluminum Alloys written by Mark Leo Renauld and published by . This book was released on 1993 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt:
