Author: JM. Larsen
Publisher:
ISBN:
Category : Crack closure
Languages : en
Pages : 13
Book Description
An experimental investigation of load interaction effects in Ti-6Al-2Sn-4Zn-2Mo is presented. Simple variable amplitude loading spectra were applied to test samples, and the crack propagation stress intensity factor, KPR, was subsequently measured. The data were condensed to two equations ("master curves") that describe the influence of an unloading cycle after constant amplitude loading and a single overload cycle, respectively. The results suggest that load interaction effects are caused by residual compressive stresses ahead of the crack front, whereas the influence of crack closure is minor.
Fatigue Crack Propagation and Load Interaction Effects in a Titanium Alloy
Load Interaction Effects on Fatigue Crack Growth in Ti-6Al-4V Alloy
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 38
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 38
Book Description
Fatigue Crack Growth Under Spectrum Loads
Author: Ralph Ivan Stephens
Publisher: ASTM International
ISBN:
Category : Alloys
Languages : en
Pages : 345
Book Description
Publisher: ASTM International
ISBN:
Category : Alloys
Languages : en
Pages : 345
Book Description
Variable Amplitude Fatigue Crack Growth in Titanium Alloy Ti-4Al-4Mo-2Sn-0.5Si (IMI 550).
Author: C. M. Ward-Close
Publisher:
ISBN:
Category : Metallurgy
Languages : en
Pages : 9
Book Description
A study has been made of fatigue crack growth behaviour in the titanium alloy (Ti-4Al-4Mo-2Sn-0.5Si) (IMI 550)), subject to single tensile overloads and the FALSTAFF flight simulation loading spectrum. Fatigue overloads were found to produce crack growth rate acceleration, followed by delayed retardation. The transient changes in crack growth rates were associated with large changes in crack closure immediately behind the crack tip. For both single overloads and flight simulation loading, the greatest load-interaction effects were at the lowest load amplitudes. Microstructure had only a slight influence on load-interaction effects associated with single tensile overloads. Great Britain. (jes).
Publisher:
ISBN:
Category : Metallurgy
Languages : en
Pages : 9
Book Description
A study has been made of fatigue crack growth behaviour in the titanium alloy (Ti-4Al-4Mo-2Sn-0.5Si) (IMI 550)), subject to single tensile overloads and the FALSTAFF flight simulation loading spectrum. Fatigue overloads were found to produce crack growth rate acceleration, followed by delayed retardation. The transient changes in crack growth rates were associated with large changes in crack closure immediately behind the crack tip. For both single overloads and flight simulation loading, the greatest load-interaction effects were at the lowest load amplitudes. Microstructure had only a slight influence on load-interaction effects associated with single tensile overloads. Great Britain. (jes).
Fatigue-crack Propagation in Several Titanium and Stainless-steel Alloys and One Superalloy
Author: C. M. Hudson
Publisher:
ISBN:
Category : Materials at high temperatures
Languages : en
Pages : 40
Book Description
Publisher:
ISBN:
Category : Materials at high temperatures
Languages : en
Pages : 40
Book Description
The Effect of Load Excursions on Fatigue Crack Growth in a Titanium Alloy
Author: David Eugene Lemm
Publisher:
ISBN:
Category :
Languages : en
Pages : 296
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 296
Book Description
On the Role of Crack Closure Mechanisms in Influencing Fatigue Crack Growth Following Tensile Overloads in a Titanium Alloy
Author: CM. Ward-Close
Publisher:
ISBN:
Category : Crack (fracturing)
Languages : en
Pages : 19
Book Description
A comparative study has been made of the transient fatigue crack growth rate behavior following tensile overloads at low (near-threshold) and high stress intensity ranges in an ?/?-type titanium alloy IMI 550, with specific emphasis of the role of crack closure mechanisms. After tensile overloads, fatigue cracks in both coarse-grained ?-annealed and fine-grained ?/? microstructures were observed initially to accelerate, followed by significant retardation, before growth rates returned to their baseline levels. The initial acceleration was attributed to an immediate reduction in near-tip closure, as indicated by metallographic sectioning, and a slight decrease in far-field closure, as measured by back-face compliance methods. Subsequent retardation was not associated with marked changes in far-field closure, although there were indications on compliance curves of a second "closure point" at a higher load, suggesting an approximate 50% increase in near-tip closure. Load interaction effects were found to be most severe where specific mechanisms of crack closure were prominant. Thus, the maximum post-overload retardations were seen in the coarse-grained ? microstructure, and when baseline stress intensity ranges were close to the threshold ?KTH, or when the maximum overload stress intensities approached the fracture toughness.
Publisher:
ISBN:
Category : Crack (fracturing)
Languages : en
Pages : 19
Book Description
A comparative study has been made of the transient fatigue crack growth rate behavior following tensile overloads at low (near-threshold) and high stress intensity ranges in an ?/?-type titanium alloy IMI 550, with specific emphasis of the role of crack closure mechanisms. After tensile overloads, fatigue cracks in both coarse-grained ?-annealed and fine-grained ?/? microstructures were observed initially to accelerate, followed by significant retardation, before growth rates returned to their baseline levels. The initial acceleration was attributed to an immediate reduction in near-tip closure, as indicated by metallographic sectioning, and a slight decrease in far-field closure, as measured by back-face compliance methods. Subsequent retardation was not associated with marked changes in far-field closure, although there were indications on compliance curves of a second "closure point" at a higher load, suggesting an approximate 50% increase in near-tip closure. Load interaction effects were found to be most severe where specific mechanisms of crack closure were prominant. Thus, the maximum post-overload retardations were seen in the coarse-grained ? microstructure, and when baseline stress intensity ranges were close to the threshold ?KTH, or when the maximum overload stress intensities approached the fracture toughness.
The Effects of an Aqueous Environment on the Fatigue Crack Propagation Characteristics of Titanium Alloys
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).
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).
The Effects of Slip Character and Crack Closure on the Growth of Small Fatigue Cracks in Titanium-aluminium Alloys
Author: James M. Larsen
Publisher:
ISBN:
Category : Aluminum alloys
Languages : en
Pages : 286
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.
Publisher:
ISBN:
Category : Aluminum alloys
Languages : en
Pages : 286
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.
Fatigue Crack Growth of Two Advanced Titanium Alloys at Room and Elevated Temperature
Author: TP. Albertson
Publisher:
ISBN:
Category : Crack closure
Languages : en
Pages : 22
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.
Publisher:
ISBN:
Category : Crack closure
Languages : en
Pages : 22
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.