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Crack closure

About: Crack closure is a research topic. Over the lifetime, 28157 publications have been published within this topic receiving 588158 citations.


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Journal ArticleDOI
TL;DR: In this paper, hydrogen embrittlement in AISI type 316 austenitic stainless steel has been investigated by in situ straining in a highvoltage electron microscope (HVEM) equipped with an environmental cell.
Abstract: The mechanisms of hydrogen embrittlement in AISI type 316 austenitic stainless steel have been investigated by in situ straining in a high-voltage electron microscope (HVEM) equipped with an environmental cell. Hydrogen effects on strain-induced phase transformations, the generation rate and velocity of dislocation, and crack propagation rates were studied. The salient features of the fracture were similar for cracks propagating in vacuum and in hydrogen gas. In each case, e and α′ martensite formed at the crack; the e phase extended ahead of the crack while the α′ phase was restricted to high stress regions near the crack tip. The principal effect of hydrogen was to decrease the stress required for dislocation motion, for phase transformation of the austenite, and for crack propagation.

138 citations

Journal ArticleDOI
TL;DR: In this article, the atomic structures that form at the tips of atomically sharp cracks in aluminum single crystals under loading were modeled using the quasicontinuum method, and it was found that deformation twinning does occur at aluminum crack tips in agreement with experimental observation.

138 citations

Journal ArticleDOI
TL;DR: In this paper, the early development of fatigue cracking along the wavy toe of manual fillet welds between structural steel plates was investigated using miniature strain gauges installed along the toe apex, in combination with beach marking.
Abstract: — An experimental study within the Canadian Offshore Corrosion Fatigue Research Programme was performed on the early development of fatigue cracking along the wavy toe of manual fillet welds between structural steel plates. Stress relieved and as-welded cruciform joints were tested under R =−1 and R= 0 loading at different stress amplitudes. The depth and the opening level of cracks as small as 10–20 μm were monitored using miniature strain gauges installed along the toe apex, in combination with beach marking. Most of the “initiation life” (25% to 50% of total life), conventionally defined by a crack depth of 0.5 mm, is consumed in short crack propagation. Three types of short crack development for different combinations of local mean stress and stress range are identified and analyzed. Growth rates in as-welded specimens are faster than in stress relieved specimens, which results in shorter “initiation lives”. This is associated with a higher effective stress range, particularly under R = - 1 loading where cracks are open over nearly the full stress range. The V-notch stress intensity factor is a promising parameter to rationalize the crack “initiation life”. It takes into account the thickness effect experimentally observed. Under R = - 1 loading of as-welded joints, using R = 0 data and taking the whole stress range gives a reasonably conservative approximation of the crack “initiation life”.

138 citations

Journal ArticleDOI
TL;DR: In this paper, the unstable growth of a crack in a large viscoelastic plate is considered, within the framework of continuum mechanics, and a non-linear, first order differential equation is found to describe the time history of the crack size if the stress applied far from the crack is constant.
Abstract: The unstable growth of a crack in a large viscoelastic plate is considered, within the framework of continuum mechanics. Starting from the local stress and deformation fields at the tip of the crack, a non-linear, first order differential equation is found to describe the time history of the crack size if the stress applied far from the crack is constant. The differential equation contains the creep compliance and the intrinsic surface energy of the material. The surface energy concept for viscoelastic materials is clarified. Inertial effects are not considered, but the influence of temperature is included for thermorheologically simple materials. Initial crack velocities are given as a function of applied load in closed form, as well as a comparison of calculated crack growth history with experiments. Above a certain high stress, crack propagation ensues at high speeds controlled by material inertia while at a lower limit infinite time is required to produce crack growth. Thus an upper and lower limit criterion of the Griffith type exists. For rate insensitive (elastic) materials the two limits coalesce and only the brittle fracture criterion of Griffith exists. The implications of these results for creep fracture in metals and inorganic glasses are examined.

138 citations

Journal ArticleDOI
Alexei Vinogradov1, S Nagasaki1, V. Patlan1, Kazuo Kitagawa1, M Kawazoe 
TL;DR: In this paper, the fatigue behavior of the fine-grain 5056 Al-alloy processed by equal-channel angular pressing (ECAP) is explored, and it is shown that the fine structure achieved during processing is unstable and tends to relax with cycling.

138 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023219
2022536
2021143
2020154
2019172
2018244