Effects of Closure on the Fatigue Crack Growth of Small Surface Cracks in a High-Strength Titanium Alloy PDF Download
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Author: Jira, JR. Publisher: ISBN: Category : Crack closure Languages : en Pages : 19
Book Description
Fatigue crack growth experiments were conducted on surface flaws in a high-strength titanium alloy. Surface crack lengths in the range 50-?m to 8 mm were investigated under both increasing and decreasing ?K conditions. Crack length and closure loads were determined from load-displacement data obtained with the aid of a laser interferometric displacement gage, which has resolution capability at 0.01 ?m. Stress ratios of 0.1, 0.5, and -1.0 and net-section stress levels from 0.2 to 0.9 of yield stress were utilized. The applied stress intensity factor range, ?K, correlated crack-growth-rate data for R = 0.1 and R = -1, but all R = 0.5 data fell along a separate band. The effective stress intensity factor range ?Keff determined from closure data, consolidated most of the data into a single band, but some small-crack data fell outside the band. Fracture surface roughness and plasticity were concluded to be the primary features contributing to crack closure.
Author: Jira, JR. Publisher: ISBN: Category : Crack closure Languages : en Pages : 19
Book Description
Fatigue crack growth experiments were conducted on surface flaws in a high-strength titanium alloy. Surface crack lengths in the range 50-?m to 8 mm were investigated under both increasing and decreasing ?K conditions. Crack length and closure loads were determined from load-displacement data obtained with the aid of a laser interferometric displacement gage, which has resolution capability at 0.01 ?m. Stress ratios of 0.1, 0.5, and -1.0 and net-section stress levels from 0.2 to 0.9 of yield stress were utilized. The applied stress intensity factor range, ?K, correlated crack-growth-rate data for R = 0.1 and R = -1, but all R = 0.5 data fell along a separate band. The effective stress intensity factor range ?Keff determined from closure data, consolidated most of the data into a single band, but some small-crack data fell outside the band. Fracture surface roughness and plasticity were concluded to be the primary features contributing to crack closure.
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.
Author: James M. Larsen Publisher: ASTM International ISBN: 0803114699 Category : Elasticity Languages : en Pages : 228
Book Description
Reviews the most recent methods for testing small cracks in a variety of materials, providing detailed quantitative information on necessary procedures for data acquisition. Emphasizes the characterization of small, three-dimensional fatigue cracks, initiated either naturally or artificially. The ei
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.
Author: Walter G. Reuter Publisher: ASTM International ISBN: 080311284X Category : Fracture mechanics Languages : en Pages : 428
Book Description
From the symposium (on title) held in Sparks, Nevada, April 1988. Twenty-two peer-reviewed papers are divided into sections on models and experiments (monotonic loading), and fatigue crack growth. Areas addressed include the differences in constraint for 2-D through-thickness cracks and 3-D surface
Author: Andrea Carpinteri Publisher: Elsevier Publishing Company ISBN: Category : Technology & Engineering Languages : en Pages : 980
Book Description
Hardbound. The purpose of this Handbook is to provide a review of the knowledge and experiences in the field of fatigue fracture mechanics. It is well-known that engineering structures can fail due to cyclic loading. For instance, a cyclically time-varying loading reduces the structure strength and can provoke a fatigue failure consisting of three stages: (a) crack initiation (b) crack propagation and (c) catastrophic failure. Since last century many scientists have tried to understand the reasons for the above-mentioned failures and how to prevent them. This Handbook contains valuable contributions from leading experts within the international scientific community and covers many of the important problems associated with the fatigue phenomena in civil, mechanical and nuclear engineering.
Author: Jira, JR.
Author: Jira, JR.
Author: James M. Larsen
Author: Wolf Elber
Author: 
Author: James M. Larsen
Author: James M. Larsen
Author: Stephen W. Smith
Author: CM. Ward-Close
Author: Walter G. Reuter
Author: Andrea Carpinteri