The Fatigue Crack Propagation Characteristics of Titanium and Two Titanium Alloys PDF Download

Author: Norman Edward Frost
Publisher:
ISBN:
Category :
Languages : en
Pages : 14

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Author: T. W. Crooker
Publisher:
ISBN:
Category :
Languages : en
Pages : 19

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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: C. M. Hudson
Publisher:
ISBN:
Category : Materials at high temperatures
Languages : en
Pages : 40

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Author: National Aeronautics and Space Adm Nasa
Publisher: Independently Published
ISBN: 9781723951589
Category : Science
Languages : en
Pages : 76

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Fatigue crack growth rates of Ti 6-2-2-2-2 as a function of stress ratio, temperature (24 or 177 C), tensile orientation and environment (laboratory air or ultrahigh vacuum) are presented. Fatigue crack growth rates of Ti 6-2-2-2-2 are also compared with two more widely used titanium alloys (Timetal 21S and Ti 6Al-4V). The fatigue crack growth rate (da/dN) of Ti 6-2-2-2-2 in laboratory air is dependent upon stress ratio (R), particularly in the near-threshold and lower-Paris regimes. For low R (less than approximately 0.5), da/dN is influenced by crack closure behavior. At higher R (> 0.5), a maximum stress-intensity factor (K(sub max)) dependence is observed. Fatigue crack growth behavior is affected by test temperature between 24 and 177 C. For moderate to high applied cyclic-stress-intensity factors (delta-K), the slope of the log da/dN versus log delta-K curve is lower in 177 C laboratory air than 24 C laboratory air. The difference in slope results in lower values of da/dN for exposure to 177 C laboratory air compared to room temperature laboratory air. The onset of this temperature effect is dependent upon the applied R. This temperature effect has not been observed in ultrahigh vacuum. Specimen orientation has been shown to affect the slope of the log da/dN versus log delta-K curve in the Paris regime.Smith, Stephen W. and Piascik, Robert S.Langley Research CenterCRACK PROPAGATION; FATIGUE (MATERIALS); TITANIUM ALLOYS; CORROSION; STRESS RATIO; TEMPERATURE EFFECTS; CRACK CLOSURE; STRESS INTENSITY FACTORS

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 76

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Author: Paul J. Bania
Publisher:
ISBN:
Category :
Languages : en
Pages : 34

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Tests were conducted on three recently developed deep-hardenable grade titanium alloys in order to assess their crack propagation and stress corrosion behavior. The alloy compositions are as follows: Alloy no. 334 (Ti-10Mo-6Cr-2.5Al); alloy no. 227 (Ti-7Mo-4Cr-2.5Al); and Alloy no. 253 (Ti-10Mo-8V-2.5Al). Compact tension specimens were cut from 6-inch diameter forging billets in three orientations. Each orientation was subsequently tested for fatigue crack growth rate and stress corrosion susceptibility. While all three alloys exhibited similar fatigue crack propagation characteristics, the chromium containing alloys appeared to be more susceptible to stress corrosion cracking. Scanning electron microscopy of the fracture surfaces revealed the presence of an apparently brittle rod-like phase. While the composition of the rods could not be directly determined, indirect evidence indicated that the rods were titanium borides. These rods were judged to have a significant effect on the fracture toughness and a lesser effect on the crack propagation properties of the alloys.

Author: R. G. Broadwell
Publisher: ASTM International
ISBN: 9780803105911
Category : Technology & Engineering
Languages : en
Pages : 306

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Author: N.E. Frost
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: J. C. Chesnutt
Publisher:
ISBN:
Category :
Languages : en
Pages : 423

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Research was conducted on two alpha-beta titanium alloys, Ti-6Al-4V and Ti-6Al-2Sn 4Zr-6Mo, as a function of alloy composition microstructure and strength level, environment, and fatigue loading conditions. A wide range of microstructural conditions, seven for Ti-6Al-4V and three for Ti-6Al-2Sn-4Zr-6Mo, was chosen to provide a full range of constituent types and morphologies and a range of mechanical properties. All the material for the program was obtained in the form of pancake forgings which were uniformly and weakly textured. The initial portion of the program consisted of material characterization and base line fatigue crack propagation (FCP) testing. Characterization included a full description of microstructures, as well as mechanical property testing, fracture toughness tests, S-N curve determination and measurement of other properties such as modulus and texture. Base line FCP testing in dry air at two stress ratios (R) of 0.1 and 0.3; and in a 3.5% NaCl solution at 1 and 20 Hz was conducted in this portion of the program. Results of this study included the determination that transformed beta microstructures generally exhibit the greatest fatigue crack propagation resistance and that increasing the load ration, R, can lead to significant increases in crack growth rate; the behavior in both cases was rationalized in terms of crack tip interaction with microstructural constituents.

Author: TW. Crooker
Publisher:
ISBN:
Category : Aqueous environment
Languages : en
Pages : 17

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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.