Through-the-thickness Fatigue Crack Closure Behavior in an Aluminum Alloy PDF Download
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Author:
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Category :
Languages : en
Pages : 12
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Book Description
Author:
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ISBN:
Category :
Languages : en
Pages : 12
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Book Description
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: AF. Blom
Publisher:
ISBN:
Category : Aluminum alloys
Languages : en
Pages : 17
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Book Description
The development of crack closure during the extension of long and short fatigue cracks has been investigated in a 2124 aluminum alloy using both experimental and numerical procedures. Specifically, the growth rate and closure behavior of long (~17 to 38 mm) cracks in compact C(T) specimens and through-thickness physically-short (~50 to 40 ?m) cracks in single-edge-notched SEN(B) bend specimens have been examined experimentally from threshold levels to instability (over the range ~10-12 to 10-7 m/cycle), and results compared with those predicted numerically using an elastic-plastic finite-element analysis of fatigue crack advance in plane strain. It is shown that the numerical analysis consistently underpredicts the magnitude of crack closure for both long and short cracks, particularly at near-threshold levels; an observation attributed to the fact that the numerical procedures can only model contributions to closure from cyclic plasticity, whereas, in reality, significant additional closure arises from the wedging action of fracture surface asperities and corrosion debris. Such closure is shown to provide the predominant mechanism for rationalizing differences in the growth rate behavior between long and physically short cracks, although other factors, such as the nature of the singularity and the extent of local plasticity, are deemed potentially to be important.
Author:
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Category :
Languages : en
Pages : 36
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Author: KK. Chan
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Category : Aluminum forging
Languages : en
Pages : 19
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Book Description
The crack-opening stress was measured using a strain gage technique on 7050 aluminum alloy, under constant amplitude and repeated overload. The behavior of crack-opening stress predicted by Newman's FASTRAN-II is consistent with the experimental results for repeated overload. It is also found that the FASTRAN-II program is capable of predicting crack growth on the 7050-T76 aluminum plate and 7050-T7452 aluminum hand forging under complex simulated flight loading which contains a significant number of compression cycles.
Author: Ralph Anthony Daiuto
Publisher:
ISBN:
Category :
Languages : en
Pages : 216
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Author: CD. Carman
Publisher:
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Category : Crack closure
Languages : en
Pages : 8
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Book Description
Fatigue crack delay behavior at high stress ratio caused by single peak overloads was investigated in two thicknesses of 7475-T731 aluminum alloy. Crack closure was measured in middle crack tension specimens with a crack-tip opening displacement gage located one-half of the specimen thickness behind the crack tip. Five overload ratios from 1.23 to 1.5 were investigated. The stress ratio was 0.7. Closure measurements indicated no closure occurred before or throughout the overload plastic zone following the overload. This was further substantiated by comparing the specimen compliance following the overload with the compliance of a low R ratio test when the crack was fully open. Scanning electron microscope studies revealed that crack tunneling and possibly reinitiation of the crack occurred, most likely a result of crack-tip blunting. The number of delay cycles was greater for the thinner mixed mode stress state specimen than for the thicker plane strain stress state specimen, which is similar to low R ratio test results and may be due to a larger plastic zone for the mixed mode case.
Author: John A. Newman
Publisher:
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Category : Fracture mechanics
Languages : en
Pages : 34
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Author: Anthony George Keslinke
Publisher:
ISBN:
Category :
Languages : en
Pages : 170
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Book Description
Author: K.S. Ravichandran
Publisher: Elsevier
ISBN: 0080569706
Category : Technology & Engineering
Languages : en
Pages : 511
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Book Description
This book contains the fully peer-reviewed papers presented at the Third Engineering Foundation Conference on Small Fatigue Cracks, held under the chairmanship of K.S. Ravichandran and Y. Murakami during December 6-11, 1998, at the Turtle Bay Hilton, Oahu, Hawaii. This book presents a state-of-the-art description of the mechanics, mechanisms and applications of small fatigue cracks by most of the world's leading experts in this field. Topics ranging from the mechanisms of crack initiation, small crack behavior in metallic, intermetallic, ceramic and composite materials, experimental measurement, mechanistic and theoretical models, to the role of small cracks in fretting fatigue and the application of small crack results to the aging aircraft and high-cycle fatigue problems, are covered.
