Crack Initiation and Crack Growth Behavior of Carbon and Low-alloy Steels PDF Download
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Languages : en
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Section III of the ASME Boiler and Pressure Vessel Code specifies fatigue design curves for structural materials. These curves were based on tests of smooth polished specimens at room temperature in air. The effects of reactor coolant environments are not explicitly addressed by the Code design curves, but recent test data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of carbon and low-alloy steels. Under certain loading and environmental conditions, fatigue lives of test specimens may be a factor of[approx]70 shorter than in air. Results of fatigue tests that examine the influence of reactor environment on crack imitation and crack growth of carbon and low-alloy steels are presented. Crack lengths as a function of fatigue cycles were determined in air by a surface replication technique, and in water by block loading that leaves marks on the fracture surface. Decreases in fatigue life of low-alloy steels in high-dissolved-oxygen (DO) water are primarily caused by the effects of environment during early stages of fatigue damage, i.e., growth of short cracks100[micro]m in depth. For crack sizes of100[micro]m, crack growth rates in high-DO water are higher than in air by one order of magnitude. The effects of LWR environments on growth of short cracks are discussed.
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Languages : en
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Book Description
Section III of the ASME Boiler and Pressure Vessel Code specifies fatigue design curves for structural materials. These curves were based on tests of smooth polished specimens at room temperature in air. The effects of reactor coolant environments are not explicitly addressed by the Code design curves, but recent test data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of carbon and low-alloy steels. Under certain loading and environmental conditions, fatigue lives of test specimens may be a factor of[approx]70 shorter than in air. Results of fatigue tests that examine the influence of reactor environment on crack imitation and crack growth of carbon and low-alloy steels are presented. Crack lengths as a function of fatigue cycles were determined in air by a surface replication technique, and in water by block loading that leaves marks on the fracture surface. Decreases in fatigue life of low-alloy steels in high-dissolved-oxygen (DO) water are primarily caused by the effects of environment during early stages of fatigue damage, i.e., growth of short cracks100[micro]m in depth. For crack sizes of100[micro]m, crack growth rates in high-DO water are higher than in air by one order of magnitude. The effects of LWR environments on growth of short cracks are discussed.
Author: William Alan Van der Sluys
Publisher: ASTM International
ISBN: 0803124082
Category : Metals
Languages : en
Pages : 304
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Author:
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Category :
Languages : en
Pages : 34
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The effect of elevated temperature aqueous environments upon the initiation and propagation of fatigue cracks in low-alloy steels is discussed in terms of the several parameters which influence such behavior. These parameters include water chemistry, impurities within the steels themselves, as well as factors such as the water flow rate, loading waveform and loading rates. Some of these parameters have similar effects upon both crack initiation and propagation, while others exhibit different effects in the two stages of cracking. In the case of environmentally-assisted crack (EAC) growth, the most important impurities within the steel are metallurgical sulfide inclusions which dissolve upon contact with the water. A ''critical'' concentration of sulfide ions at the crack tip can then induce environmentally-assisted cracking which proceeds at significantly increased crack growth rates over those observed in air. The occurrence, or non-occurrence, of EAC is governed by the mass-transport of sulfide ions to and from the crack-tip region, and the mass-transport is discussed in terms of diffusion, ion migration, and convection induced within the crack enclave. Examples are given of convective mass-transport within the crack enclave resulting from external free stream flow. The initiation of fatigue cracks in elevated temperature aqueous environments, as measured by the S-N fatigue lifetimes, is also strongly influenced by the parameters identified above. The influence of sulfide inclusions does not appear to be as strong on the crack initiation process as it is on crack propagation. The oxygen content of the environment appears to be the dominant factor, although loading frequency (strain rate) and temperature are also important factors.
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Category :
Languages : en
Pages : 23
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Book Description
Section 111 of the ASME Boiler and Pressure Vessel Code specifies fatigue design curves for structural materials. The effects of reactor coolant environments are not explicitly addressed by the Code design curves. Recent test data illustrate potentially significant effects of light water reactor (LWR) coolant environments on the fatigue resistance of carbon and low-alloy steels. Under certain loading and environmental conditions, fatigue lives of test specimens may be shorter than those in air by a factor of H"0. The crack initiation and crack growth characteristics of carbon and low-alloy steels in LWR environments are presented. Decreases in fatigue life of these steels in high-dissolved-oxygen water are caused primarily by the effect of environment on growth of short cracks
Author: A. Fatemi
Publisher:
ISBN:
Category : Crack growth
Languages : en
Pages : 20
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Book Description
Five common cast steels were subjected to SAE transmission history at room temperature and three low climatic temperatures using an as-drilled keyhole notched compact specimen. The three low temperatures were -34, -45, and -60°C. These temperatures were both above and below nil ductility transition temperatures. Three fatigue criteria were specifically monitored: crack initiation defined by the first visible surface crack ?a equal to 0.25 mm, ?a equal to 2.5 mm, and final fracture. All low-temperature total fatigue lives were equal to or better than at room temperature for four of the five cast steels. All steels exhibited crack initiation lives at low temperatures equal to or better than at room temperature. Fatigue crack growth life tended to increase as the temperature was lowered, and then this trend reversed. Scanning electron fractographic analysis showed all ductile type fatigue crack growth mechanisms above or below the nil ductility transition temperature.
Author: Saurindranath Majumdar
Publisher:
ISBN:
Category : Steel
Languages : en
Pages : 58
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Book Description
In a previous report, a fatigue crack propagation model was analyzed by considering fatigue crack propagation as a sequence of fatigue crack initiation events. This permitted correlation to be made between the fatigue crack growth resistance and low cycle fatigue properties of metals. Four steels were tested for low cycle fatigue behavior at the University of Illinois. Good correlation was obtained between the theoretically predicted crack propagation rate based on the measured low cycle fatigue properties of the four metals and experimentally observed crack propagation rates that were reported in the literature. Further, good estimates of crack propagation rates can be obtained on the basis of static tensile properties of the metals alone where cyclic properties are not available. (Author).
Author:
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ISBN:
Category :
Languages : en
Pages :
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Author: T. A. Auten
Publisher:
ISBN:
Category : Steel, Structural
Languages : en
Pages : 28
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Book Description
Author: M. A. Meyers
Publisher: Elsevier
ISBN: 0080537235
Category : Technology & Engineering
Languages : en
Pages : 317
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Book Description
The importance of the nanoscale effects has been recognized in materials research for over fifty years, but it is only recently that advanced characterization and fabrication methods are enabling scientists to build structures atom-by-atom or molecule-by molecule. The understanding and control of the nanostructure has been, to a large extent, made possible by new atomistic analysis and characterization methods pioneered by transmission electron microscopy. Nano and Microstructural Design of Advanced Materials focuses on the effective use of such advanced analysis and characterization techniques in the design of materials. - Teaches effective use of advanced analysis and characterization methods at an atomistic level - Contains many supporting examples of materials in which such design concepts have been successfully applied
Author: BL. Braglia
Publisher:
ISBN:
Category : Block loading
Languages : en
Pages : 13
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Book Description
The fatigue crack initiation behavior of a high-strength low-alloy steel, VAN-80, has been investigated. Crack initiation was defined, for the purposes of the study, as the existence of a 0.25-mm long crack on either surface of a modified compact tension specimen.
