Journal ArticleDOI
Environmental fatigue crack propagation of aluminum alloys at low stress intensity levels
John A. Feeney,J. Corey Mcmillan,Robert P. Wei +2 more
- Vol. 1, Iss: 6, pp 1741-1757
TLDR
In this paper, both wedge force loading and remote loading techniques were employed to achieve the desired ΔK levels, and preliminary experiments were designed to test their compatibility, and the observed crack growth rates compared with those in desiccated air.Abstract:
Environmental fatigue crack propagation in 2024-T3, 7075-T6, and 7178-T6 has been studied at low levels of cyclic amplitude of stress intensity, ΔK. Both wedge force loading and remote loading techniques were employed to achieve the desired ΔK levels, and preliminary experiments were designed to test their compatibility. Testing was carried out in humid air, distilled water, and 3.5 pct sodium chloride solution, and the observed crack growth rates compared with those in desiccated air. Later studies were also conducted in an inert reference environment with a total water content of less than 2 ppm. When the data are plotted as log ΔK vs log d2a /dN, alloy 2024-T3 exhibits a marked slope transition, alloy 7075-T6 a slight slope transition, and alloy 7178-T6 a rectilinear behavior throughout the whole range of ΔK studied. The basic shape of these curves is discussed in terms of state-of-stress conditions at the crack tip, frequency effects, environmental effects, strain rate sensitivity, and metallurgical structure. An attempt is also made to correlate the rate of fatigue crack propagation in a particular environment and at a particular ΔK level with the fracture topography.read more
Citations
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Journal ArticleDOI
Influence of microstructure on near-threshold fatigue-crack propagation in ultra-high strength steel
TL;DR: In this paper, the authors investigated the influence of microstructure on fatigue fracture behavior near the threshold stress intensity, ∆K 0 below which crack growth cannot be detected, and showed that near-threshold crack -growth resistance can be improved by cyclic softening, coarsening the prior austenite grain size, and (iii)...
Journal ArticleDOI
Mechanisms of Slow Fatigue Crack Growth in High Strength Aluminum Alloys: Role of Microstructure and Environment
TL;DR: In this article, the role of microstructure and environment in influencing ultra-low fatigue crack propagation rates has been investigated in 7075 aluminum alloy heat-treated to underaged, peak-aged, and overaged conditions and tested over a range of load ratios.
Book ChapterDOI
The Role of Metallurgical Variables in Hydrogen-Assisted Environmental Fracture
TL;DR: In this paper, two kinds of environmental fracture, stress corrosion cracking (SCC) and hydrogen embrittlement, and the role in such failures of a number of metallurgical variables are discussed.
Bibliography of information on mechanics of structural failure (hydrogen embrittlement, protective coatings, composite materials, NDE)
TL;DR: In this paper, the authors present a bibliography consisting of approximately 1,600 reference citations related to four problem areas in the mechanics of failure in aerospace structures: hydrogen embrittlement, protective coatings, composite materials, and non-destructive evaluation.
Journal ArticleDOI
Fatigue crack growth characteristics at low stress intensities of metals and alloys
TL;DR: In this paper, the fatigue-crack growth (fcg) behavior of metals and alloys at low stress intensities is considered in terms of load ratio, microstructure, and environment.
References
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Journal ArticleDOI
Fatigue crack propagation—an analysis
TL;DR: In this paper, the basic laws governing fatigue are derived theoretically for failure in both the high and low stress regions, and the material parameters controlling crack propagation determined, and a simple theory is developed to assess quantitatively the mechanism of fatigue crack propagation in metals.
Journal ArticleDOI
Fatigue damage and crack growth in aluminium alloys
TL;DR: In this article, the authors present evidence for microstructural changes that can occur in aluminium alloys when subjected to fatigue stress, and make distinctions between the various forms of fracture striation that are encountered.
Journal ArticleDOI
The propagation of fatigue cracks in sheet specimens
N.E. Frost,D.S. Dugdale +1 more
TL;DR: In this article, the growth of the fatigue cracks initiated by the slit were made as the test proceeded, and it was found that the rate of growth was proportional to the current crack length.
Journal ArticleDOI
Crack extension by alternating shear
TL;DR: In this article, a comparison of the slip line flow field at the tip of a sharp crack and of a blunted crack is made, and it is shown that fatigue crack propagation is the result of repeated cyclic crack extension by alternating shear.