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Author: T. W. Crooker Publisher: ISBN: Category : Languages : en Pages : 19
Book Description
Fatigue crack propagation was studied in Ti-6Al-4V, Ti-7Al-2Cb-1Ta, Ti-6Al-6V-2Sn-1Cu-0.5Fe, Ti-6Al-3V-1Mo, and Ti-7Al-2.5Mo alloys. These materials possess yield strengths in excess of 100 ksi, combined with favorable levels of fracture toughness, and they are currently under evaluation for application in large welded structures. Where an application involves repetitive loading, a knowledge of fatigue crack propagation characteristics is required for failure-safe design against fracture. Fabrication and non-destructive testing procedures cannot guarantee that cracklike defects, which can grow to a critical size, will not be present in plate-thickness sections containing welded joints. In addition, the role of an aggressive environment, such as salt water, in this failure mechanism is of the utmost importance. Fatigue crack propagation data were taken in both ambient room air and 3.5% salt-water environments. Surface-notched plate bend specimens were cycled in full-reverse (tension-to-compression) sinusoidal loading. The fatigue crack was observed optically, and the crack growth rate was described as an empirical power-law function of the total (elastic-plus-plastic) strain range. Fatigue crack growth rate relationships were first developed in an air environment and then employed as baselines for establishing the effect of the salt-water environment. Comparisons were made among the fatigue crack propagation characteristics of the several titanium alloys and among a broad spectrum of high-strength structural alloys, both ferrous and nonferrous, previously studied. (Author).
Author: T. W. Crooker Publisher: ISBN: Category : Languages : en Pages : 19
Book Description
Fatigue crack propagation was studied in Ti-6Al-4V, Ti-7Al-2Cb-1Ta, Ti-6Al-6V-2Sn-1Cu-0.5Fe, Ti-6Al-3V-1Mo, and Ti-7Al-2.5Mo alloys. These materials possess yield strengths in excess of 100 ksi, combined with favorable levels of fracture toughness, and they are currently under evaluation for application in large welded structures. Where an application involves repetitive loading, a knowledge of fatigue crack propagation characteristics is required for failure-safe design against fracture. Fabrication and non-destructive testing procedures cannot guarantee that cracklike defects, which can grow to a critical size, will not be present in plate-thickness sections containing welded joints. In addition, the role of an aggressive environment, such as salt water, in this failure mechanism is of the utmost importance. Fatigue crack propagation data were taken in both ambient room air and 3.5% salt-water environments. Surface-notched plate bend specimens were cycled in full-reverse (tension-to-compression) sinusoidal loading. The fatigue crack was observed optically, and the crack growth rate was described as an empirical power-law function of the total (elastic-plus-plastic) strain range. Fatigue crack growth rate relationships were first developed in an air environment and then employed as baselines for establishing the effect of the salt-water environment. Comparisons were made among the fatigue crack propagation characteristics of the several titanium alloys and among a broad spectrum of high-strength structural alloys, both ferrous and nonferrous, previously studied. (Author).
Author: TW. Crooker Publisher: ISBN: Category : Aqueous environment Languages : en Pages : 17
Book Description
Fatigue crack propagation studies were conducted on Ti-6Al-4V, Ti-7Al-2Cb-1Ta, Ti-6Al-6V-2Sn-1Cu-0.5Fe, Ti-6Al-3V-1Mo, and Ti-7Al-2.5Mo alloys. These materials possess yield strengths in excess of 100 ksi, combined with favorable levels of fracture toughness, and they are currently under evaluation for application in large welded structures. Where an application involves repetitive loading, a knowledge of fatigue crack propagation characteristics is required for failure-safe design against fracture. Fabrication and nondestructive testing procedures cannot guarantee that crack-like defects which can grow to a critical size will not be present in plate-thickness sections containing welded joints. In addition, the role of an aggressive environment, such as salt water, in this failure mechanism is of the utmost importance. This paper reports on fatigue crack propagation data taken in both ambient room air and 3.5 per cent salt water environments. Surface-notched plate bend specimens were cycled in full-reverse (tension-to-compression) sinusoidal loading. The fatigue crack was observed optically, and the crack growth rate is described as an empirical power-law function of the total (elastic plus plastic) strain range. Fatigue crack growth rate relationships are first developed in an air environment and then employed as baselines for establishing the effect of the salt water environment. Comparisons are made among the fatigue crack propagation characteristics of the several titanium alloys described in this paper and among a broad spectrum of high-strength structural alloys, both ferrous and nonferrous, previously studied.
Author: H. W. Rosenberg Publisher: ISBN: Category : Clear air turbulence Languages : en Pages : 15
Book Description
The laboratory conditions under which hot-salt cracking can occur in titanium alloys are reviewed and orders of merit among the alloys established. The large differences among alloys give promise of new alloys immune to the phenomenon. Hot-salt cracking is a case of classical stress corrosion. Alloy research and development disclose a system of titanium alloys that is immune to hot-salt cracking. One promising composition, Ti-2Al-4Zr-4Mo, is shown to have excellent combinations of mechanical properties. The fracture toughness of commercial titanium alloys in salt water is also examined. In the presence of fatigue cracks actively extending under applied loads, salt water can have the effect of reducing the crack propagation resistance of several titanium alloys. Because salt water has no effects on titanium alloys in the absence of cracks, its environmental effect is not classical stress corrosion. The problem can be largely eliminated in Ti-8Al-1Mo-1V sheet by creating microstructures consisting of a continuous matrix of transformed beta.
Author: National Aeronautics and Space Administration (NASA) Publisher: Createspace Independent Publishing Platform ISBN: 9781721017546 Category : Languages : en Pages : 32
Book Description
To study the effects of atmospheric species on the fatigue crack growth behavior of an a+B titanium alloy (Ti 6-2-2-2-2) at room temperature and 177 C, fatigue tests were performed in laboratory air, ultrahigh vacuum, and high purity water vapor, oxygen, nitrogen and helium at various partial pressures. Accelerated fatigue crack growth rates in laboratory air compared to ultrahigh vacuum are linked to the damaging effects of both water vapor and oxygen. Observations of the fatigue crack growth behavior in ultrahigh purity environments, along with surface film analysis using X-ray photoelectron spectroscopy (XPS), suggest that multiple crack-tip processes govern the damaging effects of air. Three possible mechanisms are proposed: 1) at low pressure (less than 10(exp -1) Pa), accelerated da/dN is likely due to monolayer adsorption on crack-tip surfaces presumably resulting in decreased bond strengths at the fatigue crack tip, 2) for pressures greater than 10(exp -1) Pa, accelerated da/dN in oxygen may result from oxidation at the crack tip limiting reversible slip, and 3) in water vapor, absorption of atomic hydrogen at the reactive crack tip resulting in process zone embrittlement.Smith, Stephen W. and Piascik, Robert S.Langley Research CenterFATIGUE TESTS; FATIGUE (MATERIALS); CRACK PROPAGATION; TITANIUM ALLOYS; EMBRITTLEMENT; ATMOSPHERIC COMPOSITION; X RAY SPECTROSCOPY; WATER VAPOR; ULTRAHIGH VACUUM; PHOTOELECTRON SPECTROSCOPY
Author: T. W. Crooker
Author: T. W. Crooker
Author: TW. Crooker
Author: H. W. Rosenberg
Author: National Aeronautics and Space Administration (NASA)
Author: 
Author: 
Author: I. E. Figge
Author: Conrad H.
Author: Naval Research Laboratory (U.S.)
Author: C. M. Hudson