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Author :
Publisher :
ISBN 13 :
Total Pages : 142 pages
Book Rating : 4.:/5 (317 download)
Download or read book Study of Near-threshold Fatigue Crack Propagation in Pipeline Steels in High Pressure Environments written by and published by . This book was released on 1981 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Charles Michael Moss
Publisher :
ISBN 13 :
Total Pages : 158 pages
Book Rating : 4.:/5 (74 download)
Download or read book Near-threshold Fatigue Crack Propagation in Pressure Vessel Steels written by Charles Michael Moss and published by . This book was released on 1979 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Comparison of Environmentally-influenced Near-threshold Fatigue-crack-growth Behavior in High- and Lower-strength Steels at Conventional Frequencies written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent studies in a wide variety of steels, of yield strengths ranging from 290 to 1740 MPa, have indicated that environmental influences on corrosion fatigue crack propagation at near-threshold levels (growth rates below approx. 10/sup -6/ mm/cycle), may be markedly different from those at higher growth rates. In this paper, the effect of such environments, specifically dry gaseous hydrogen and moist room air, on near-threshold cyclic crack growth is reviewed and comparisons made between behavior in high and lower strength steels. It is shown that, in lower strength steels (yield strength less than or equal to 700 MPa), near-threshold growth rates in dry hydrogen exceed those in moist air by up to two orders of magnitude at low load ratios only, whereas for steels of strength levels above approx. 700 MPa, the presence of hydrogen results in lower near-threshold growth rates compared to moist air regardless of load ratio. Such behavior is rationalized in terms of the competing effects of hydrogen embrittlement and oxide-induced crack closure mechanisms.
Author : W. H. Cullen
Publisher :
ISBN 13 :
Total Pages : 134 pages
Book Rating : 4.3/5 (91 download)
Download or read book A Review of Fatigue Crack Growth of Pressure Vessel and Piping Steels in High-temperature, Pressurized Reactor-grade Water written by W. H. Cullen and published by . This book was released on 1980 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue crack growth data sets, for pressure vessel and piping steels, in reactor-grade water environment have appeared in various reports and publications since about 1972. All of the results which have been published from 1972 through 1979 have been plotted and are presented in this report. Beginning with a discussion of the need for these data, and an explanation of the laboratory facilities which are required for this research, this report goes on to describe the overall trends which have evolved through consideration of the data sets and the conditions under which they were generated. A model for hydrogen assisted fatigue crack growth is described and applied to the pressurized water reactor type of environment. A complete listing of references is included in the report. (Author).
Author : J. Mautz
Publisher :
ISBN 13 :
Total Pages : 15 pages
Book Rating : 4.:/5 (125 download)
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.
Author : C. Sarrazin-Baudoux
Publisher :
ISBN 13 :
Total Pages : 20 pages
Book Rating : 4.:/5 (125 download)
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.
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ISBN 13 :
Total Pages : 964 pages
Book Rating : 4.:/5 (31 download)
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1988 with total page 964 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
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.
Author : Mengshan Yu
Publisher :
ISBN 13 :
Total Pages : 266 pages
Book Rating : 4.:/5 (959 download)
Download or read book Crack Growth Behavior of Pipeline Steels Under Variable Pressure Fluctuations in a Near-neutral PH Environment written by Mengshan Yu and published by . This book was released on 2015 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research aims at understanding the crack propagation behavior of pipeline steels under variable pressure fluctuations in a near-neutral pH environment. Although pressure fluctuations have been recognized as the driving force for crack growth for more than two decades, the mechanisms governing their effects on crack growth have yet to be determined. Existing crack growth models that consider the effect of pressure fluctuations are established primarily by assuming a fatigue loading with constant stress amplitudes. This often yields a predicted life that well exceeds the service lifetime observed in the field. We believe that the significant discrepancies between laboratory findings and field observations could be bridged by modeling crack growth through a consideration of variable amplitude fatigue loadings, which are the conditions in the field. This investigation has focused on the evaluation of a variable amplitude fatigue waveform consisting of cycles with higher R ratios (minimum stress/maximum stress), termed as minor cycles, and periodic underload cycles with lower R ratios. Such a waveform is typical for the pressure fluctuations in pipeline discharge sections, which was performed both in air and in near-neutral pH solution. Compared with the corresponding constant amplitude loadings, the variable amplitude waveform significantly enhanced fatigue crack growth. The waveform was varied to study the effects of various contributing factors, including loading frequency, maximum stress intensity factor, number of minor cycles, and amplitudes of underload and minor cycles. By comparing results in near-neutral pH solution with that in air, the role of hydrogen and corrosion in crack growth was characterized and clearly defined. The obtained results agree with various failure scenarios found in the field, including the high frequency of failures found at the discharge sections of pipelines, and the different crack growth characteristics between oil pipelines and gas pipelines. Based on these findings, practical strategies were proposed for avoiding accelerated crack growth.
Author : S. Suresh
Publisher :
ISBN 13 :
Total Pages : 19 pages
Book Rating : 4.:/5 (125 download)
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.
Download or read book Influences of Gaseous Environment on Low Growth-rate Fatigue Crack Propagation in Steels. Annual Report No. 1, January 1980. Report No. FPL/R/80/1030 written by and published by . This book was released on 1980 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The influence of gaseous environment is examined on fatigue crack propagation behavior in steels. Specifically, a fully martensitic 300-M ultrahigh strength steel and a fully bainitic 2-1/4Cr-1Mo lower strength steel are investigated in environments of ambient temperature moist air and low pressure dehumidified hydrogen and argon gases over a wide range of growth rates from 10−8 to 10−2 mm/cycle, with particular emphasis given to behavior near the crack propagation threshold .delta.K0. It is found that two distinct growth rate regimes exist where hydrogen can markedly accelerate crack propagation rates compared to air, (1) at near-threshold levels below (5 x 10−6 mm/cycle) and (2) at higher growth rates, typically around 10−5 mm/cycle above a critical maximum stress intensity K/sub max//sup T/. Hydrogen-assisted crack propagation at higher growth rates is attributed to a hydrogen embrittlement mechanism, with K/sub max//sup T/ nominally equal to K/sub Iscc/ (the sustained load stress corrosion threshold) in high strength steels, and far below K/sub Iscc/ in the strain-rate sensitive lower strength steels. Hydrogen-assisted crack propagation at near-threshold levels is attributed to a new mechanism involving fretting-oxide-induced crack closure generated in moist (or oxygenated) environments. The absence of hydrogen embrittlement mechanisms at near-threshold levels is supported by tests showing that .delta.K0 values in dry gaseous argon are similar to .delta.K0 values in hydrogen. The potential ramifications of these results are examined in detail.
Author : Michael K. Schaper
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ISBN 13 :
Total Pages : 23 pages
Book Rating : 4.:/5 (125 download)
Download or read book Fatigue Crack Closure at Near-Threshold Growth Rates in Steels, Effects of Microstructure, Load Sequence and Environment written by Michael K. Schaper and published by . This book was released on 2012 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper summarizes long-term research on fatigue crack closure in several labs of the author. Various experimental techniques were used in different combinations. Primarily, a sophisticated dynamic compliance technique based on highly sensitive resonance vibration measurements and crack tip diffracted ultrasonic wave analysis is applied. Whereas the first method reflects the global through thickness behavior, the second method enables spatial resolution, which is achieved with a reduction of sensitivity yet has the advantage that the signal generation is independent on the stress state ahead of the crack tip. The results allow a coherent view into the effects of the stress state, material plasticity, fracture surface roughness, and oxidation tendency on the closure behavior and, therefore, on both the threshold stress intensity and near-threshold crack propagation. Specifically, the different load ratio, load sequence, and the environmental effects on the threshold values of ferritic, martensitic, and austenitic steels are addressed.
Author : W. H. Cullen
Publisher :
ISBN 13 :
Total Pages : 80 pages
Book Rating : 4.3/5 (91 download)
Download or read book Fatigue Crack Growth Rates in Pressure Vessel and Piping Steels in LWR Environments written by W. H. Cullen and published by . This book was released on 1987 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : A. H. Priest
Publisher :
ISBN 13 : 9789282536094
Total Pages : 47 pages
Book Rating : 4.5/5 (36 download)
Download or read book Fatigue Crack Growth and Fracture Resistance of Steels in High-pressure Hydrogen Environments written by A. H. Priest and published by . This book was released on 1983 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 660 pages
Book Rating : 4.0/5 ( download)
Download or read book Energy Research Abstracts written by and published by . This book was released on 1989 with total page 660 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
Author : Thomas Charles Babcock
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ISBN 13 :
Total Pages : 166 pages
Book Rating : 4.E/5 ( download)
Download or read book Fatigue-environmental Crack Propagation in a High Strength Steel written by Thomas Charles Babcock and published by . This book was released on 1969 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jingjun Yang
Publisher :
ISBN 13 :
Total Pages : 274 pages
Book Rating : 4.:/5 (344 download)
Download or read book Experimental and Theoretical Characterization of Near-threshold Fatigue Crack Growth for High Strength Steels in Seawater written by Jingjun Yang and published by . This book was released on 1995 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:
