Fatigue Crack Growth Rate Behavior in Titanium Alloy Ti-5111 Weld Metal PDF Download
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Author:
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Category :
Languages : en
Pages : 24
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Book Description
Fatigue crack growth rate (FCGR) tests were conducted on Titanium Alloy Ti-5111 weld metal in air, artificial seawater, and artificial seawater with an applied cathodic potential. The results indicated a minor effect of seawater in increasing FCGR of Ti-5111 weld metal. However, the application of a cathodic potential of 0.987 V versus Ag/AgCl reference electrode showed crack growth rates similar to FCGR in air. Additionally, comparisons are made regarding the FCGR behavior of Ti-5111 plate, Ti-100 (Ti-621-0.8Mo) plate, and Ti-5111 weld metal in both air and seawater. These results indicated that both high strength titanium alloy grades, including the base and weld metal, performed similarly in all test environments.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 24
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Book Description
Fatigue crack growth rate (FCGR) tests were conducted on Titanium Alloy Ti-5111 weld metal in air, artificial seawater, and artificial seawater with an applied cathodic potential. The results indicated a minor effect of seawater in increasing FCGR of Ti-5111 weld metal. However, the application of a cathodic potential of 0.987 V versus Ag/AgCl reference electrode showed crack growth rates similar to FCGR in air. Additionally, comparisons are made regarding the FCGR behavior of Ti-5111 plate, Ti-100 (Ti-621-0.8Mo) plate, and Ti-5111 weld metal in both air and seawater. These results indicated that both high strength titanium alloy grades, including the base and weld metal, performed similarly in all test environments.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781720523284
Category :
Languages : en
Pages : 74
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Book Description
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
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ISBN:
Category :
Languages : en
Pages : 76
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Author: Todd P. Albertson
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ISBN:
Category : Aluminum alloys
Languages : en
Pages : 214
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Author: Y. Pardhi
Publisher:
ISBN:
Category : Fatigue crack propagation
Languages : en
Pages : 19
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Book Description
The inertia friction welding process is being extensively investigated for the joining of high strength titanium alloys for aerospace applications. Although it offers solid state joining, the thermal cycle and deformation involved results in microstructural inhomogeneity across the weld interface. In this paper, the fatigue crack propagation behavior in an inertia welded microstructure in a high strength, high temperature ?/? titanium alloy is considered. The fatigue crack propagation behavior in corner notched weld specimens at varying stress ratios is studied at room and elevated temperatures and compared with that of the parent material. Fatigue crack growth rates at lower stress intensity ranges are comparable with those in the parent material. However, in weld specimens tested at room temperature, unstable crack growth occurs at lower stress intensity range values compared to that at high temperature. Fracture surface observations show that this difference is related to a change in fracture mode from transgranular to intergranular/mixed mode during room temperature tests. This change in fatigue crack growth mechanism is deduced to be due to low ductility intergranular failure of grain boundary ? in the refined transformed beta microstructure across the weld interface.
Author: James M. Larsen
Publisher:
ISBN:
Category : Aluminum alloys
Languages : en
Pages : 286
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Book Description
An investigation was performed to study the effects of slip character and crack closure on the propagation of small fatigue cracks in titanium- aluminum alloys. The materials examined were solution-treated Ti-4Al and Ti-8Al, as well as aged Ti-8Al. The propagation of naturally initiated surface cracks of depths as small as 25 micrometers was compared with the behavior of large through-thickness cracks. An extensometer was used to monitor crack closure throughout the large crack tests, and the closure behavior of the small cracks was measured using a computerized laser interferometric displacement gage having a displacement resolution of 0.01 micrometer. The measurements of crack closure were used to compute an effective stress intensity factor range. In all three alloys and for all test conditions, which included a range of stress levels and stress ratios, small cracks propagated faster than large cracks subjected to an equivalent Delta K, and the small cracks propagated under conditions that were significantly below the large-crack threshold, Delta K(th). Although the character and distribution of slip in Ti-Al alloys may have a dramatic influence on fatigue crack initiation and on the propagation of large cracks, this effect was minimal for small cracks.
Author:
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Category :
Languages : en
Pages : 11
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Book Description
The effects of weld microstructure and weld speed on the fatigue crack growth kinetics of friction stir welded Ti-5111 were investigated. The FSW welds in Ti-5111 consist of very fine recrystallized grains, in contrast to coarse basketweave grains in the base plate. Fatigue crack growth rates are significantly lower and fatigue crack growth thresholds are significantly higher through the weld than those in the base plate. As the weld speed increases, the fatigue crack growth rates are progressively higher and fatigue crack growth thresholds lower through the weld. However, after stress-relief annealing, such differences in fatigue crack growth kinetics among different weld speeds no longer exist. Fatigue crack growth rates through post stress-relieved welds are higher than those in the base metal. The observed fatigue crack growth responses are discussed in terms of differences in crack tip microstructure, compressive residual stresses, crack closure, and crack deflection.
Author: C. M. Hudson
Publisher:
ISBN:
Category : Materials at high temperatures
Languages : en
Pages : 40
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Author: TP. Albertson
Publisher:
ISBN:
Category : Crack closure
Languages : en
Pages : 22
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Book Description
This paper provides fatigue crack growth information at low crack growth rates for two sheet titanium alloys: ?-21S, a ? alloy, and Ti-62222, an ? + ? alloy. Room (25°C) and elevated temperature (175°C) fatigue crack growth tests at two different stress ratios, R = 0.1 and 0.5, were performed. Effects of temperature and stress ratio were evaluated in order to study the complex interaction between fatigue, environment, and loading conditions. Crack-opening load was measured throughout the test from automated compliance measurements and was used to adjust fatigue crack growth data for crack closure. For ?-21S, fatigue crack growth rates were similar at 175 and 25°C at a stress ratio of 0.1, while crack growth rates were lower at 175 versus 25°C at a stress ratio of 0.5 for the same nominal ?K. Concepts associated with crack closure accounted for this as crack growth rates were found to be higher at 175°C than 25°C for both stress ratios when plotted as a function of ?Keff, showing a temperature dependency on crack growth rate. For Ti-62222, fatigue crack growth rates were comparable between 25 and 175°C for R = 0.5, but were different at R = 0.1 where crack closure was observed at 175°C. Fatigue crack growth behavior of these two titanium alloys was comparable for all loading and temperature conditions.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721017546
Category :
Languages : en
Pages : 32
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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
