Fatigue crack closure under cyclic tension
TL;DR: In this article, an analysis of the stress distribution acting on the fracture surfaces shows that the local compressive stress maxima may exceed the yield stress of the material and that crack closure may influence the shape of the striation pattern.
About: This article is published in Engineering Fracture Mechanics.The article was published on 1970-07-01. It has received 1876 citations till now. The article focuses on the topics: Crack closure & Stress concentration.
Citations
More filters
TL;DR: A comprehensive review of cumulative fatigue damage theories for metals and their alloys, emphasizing the approaches developed between the early 1970s to the early 1990s, can be found in this paper, where the authors grouped these theories into six categories: linear damage rules, nonlinear damage curve and two-stage linearization approaches; life curve modification methods; approaches based on crack growth concepts; continuum damage mechanics models; and energy-based theories.
1,123 citations
TL;DR: In this paper, the authors review the current state of the art as CT transforms from a qualitative diagnostic tool to a quantitative one, including the use of iterative reconstruction strategies suited to specific segmentation tasks and emerging methods that provide more insight than conventional attenuation based tomography.
Abstract: X-ray computer tomography (CT) is fast becoming an accepted tool within the materials science community for the acquisition of 3D images. Here the authors review the current state of the art as CT transforms from a qualitative diagnostic tool to a quantitative one. Our review considers first the image acquisition process, including the use of iterative reconstruction strategies suited to specific segmentation tasks and emerging methods that provide more insight (e.g. fast and high resolution imaging, crystallite (grain) imaging) than conventional attenuation based tomography. Methods and shortcomings of CT are examined for the quantification of 3D volumetric data to extract key topological parameters such as phase fractions, phase contiguity, and damage levels as well as density variations. As a non-destructive technique, CT is an ideal means of following structural development over time via time lapse sequences of 3D images (sometimes called 3D movies or 4D imaging). This includes information nee...
1,009 citations
Cites background from "Fatigue crack closure under cyclic ..."
...So-called crack closure is an important mechanism in retarding fatigue crack growth.(297) It has been studied by CT as long ago as 1995(298) revealing how the topology of the fracture surface of Al–Li alloy determines the onset and extent of closure during unloading from the maximum load....
[...]
TL;DR: In this article, the authors examined the mechanisms of fatigue-crack propagation with particular emphasis on the similarities and differences between cyclic crack growth in ductile materials such as metals, and corresponding behavior in brittle materials, such as intermetallics and ceramics.
Abstract: The mechanisms of fatigue-crack propagation are examined with particular emphasis on the similarities and differences between cyclic crack growth in ductile materials, such as metals, and corresponding behavior in brittle materials, such as intermetallics and ceramics. This is achieved by considering the process of fatigue-crack growth as a mutual competition between intrinsic mechanisms of crack advance ahead of the crack tip (e.g., alternating crack-tip blunting and resharpening), which promote crack growth, and extrinsic mechanisms of crack-tip shielding behind the tip (e.g., crack closure and bridging), which impede it. The widely differing nature of these mechanisms in ductile and brittle materials and their specific dependence upon the alternating and maximum driving forces (e.g., ΔK andK
max) provide a useful distinction of the process of fatigue-crack propagation in different classes of materials; moreover, it provides a rationalization for the effect of such factors as load ratio and crack size. Finally, the differing susceptibility of ductile and brittle materials to cyclic degradation has broad implications for their potential structural application; this is briefly discussed with reference to lifetime prediction.
803 citations
Cites background from "Fatigue crack closure under cyclic ..."
...Elber (1970) originally proposed that closure arises from the constraint of surrounding elastic material on the residual stretch in material elements previously plastically strained at the tip (plasticity-induced closure)....
[...]
01 Aug 1988-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the authors examined the effect of crack tip shielding on fatigue crack propagation behavior in metals, composites and ceramics, and showed that, whereas crack-tip shielding can provide a potent means of enhancing resistance to crack growth, such extrinsic toughening mechanisms can result in the apparently anomalous behavior of small cracks and to the susceptibility of brittle materials to fatigue failure.
Abstract: Crack tip shielding phenomena, whereby the “effective crack-driving force” actually experienced at the crack tip is locally reduced, are examined with reference to fatigue crack propagation behavior in metals, composites and ceramics. Sources of shielding are briefly described in terms of mechanisms relying on the production of elastically constrained zones which envelop the crack (zone shielding), on the generation of wedging, bridging or sliding forces between the crack surfaces (contact shielding) and on crack path deflection and meandering. Examples are taken from the fatigue behavior of high strength lithium-containing aluminum alloys, aluminum alloy-aramid fiber-epoxy laminate composites, and zirconia ceramics. It is shown that, whereas crack tip shielding can provide a potent means of enhancing “resistance” to crack growth, such extrinsic toughening mechanisms can result in the apparently anomalous behavior of “small cracks” and to the susceptibility of brittle materials to fatigue failure.
731 citations
TL;DR: In this paper, the influence of casting defects on the room temperature fatigue performance of a Sr-modified A356-T6 casting alloy has been studied using unnotched polished cylindrical specimens.
510 citations
References
More filters
01 Jan 1967
633 citations