Why do cracks avoid each other?

Melin, Solveig

doi:10.1007/bf00020156

Cited by 160 publications

(60 citation statements)

References 4 publications

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“…It has also been shown that two collinear approaching cracks (submitted to a uniaxial stress in mode I) can repel each other instead of merging tip to tip [21], resulting in a curved, "hookshaped" path. Such cracks have been observed for a wide range of scales in nature, from 25 cm quartz-feldspar veins in granite to 25 km-long oceanic ridges [18], as well as in laboratory experiments on glass [22], Polymethylmethacrylate plates [21,23] or more recently in paper [24] and gelatin sheets [25]. Theoretical studies have tried to explain this truly nonintuitive behavior.…”

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confidence: 96%

“…Theoretical studies have tried to explain this truly nonintuitive behavior. First, Melin [23] showed that the collinear crack configuration is unstable. Then, Kachanov [26] noticed that the slightest disturbances in the initial symmetric configuration will give rise to a mixed mode interaction (traction and shear stresses).…”

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confidence: 99%

“…The fact that the cracks are observed to deviate instead of going straight to minimize shear stresses led him to suggest that the cracks might actually follow a path that maximizes the energy release rate, instead of the path following the principle of local symmetry [27,28]. Numerical simulations [29][30][31] can only reproduce qualitatively the shapes observed, and most of experiments have been performed only on the final post-mortem path (usually obtained in a fast dynamic fracture regime [23,24]). Finally, very few works have studied in detail, or even simply ignore the repulsive part of the fracture trajectory [25], and especially the amount of deviation, for which no clear predictions are established.…”

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confidence: 99%

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Repulsion and Attraction between a Pair of Cracks in a Plastic Sheet

et al. 2015

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Repulsion and Attraction between a Pair of Cracks in a Plastic Sheet

et al. 2015

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“…Thus unlike the opening mode crack problems, the lengthening of the LVRSs appears to have inherent limitation. Also, it is well known that originally collinear mode I crack tips would avoid each other before coalescence and thus tip-to-tip coalescence would not take place [Melin, 1983]. However, our simulation results, based on the volumetric plastic strain distributions around PSSs' tips, appear to show that two neighboring collinear or echelon PSSs are able to link directly from tip to tip if their closer tips distance is relatively small.…”

Section: Interpretation and Discussionmentioning

confidence: 63%

Mechanics of pressure solution seam growth and evolution

Zhou

Aydin

2010

J. Geophys. Res.

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[1] Pressure solution seams (PSSs) can be idealized as localized volume reduction structures (LVRSs) in terms of their mechanics. Previous mechanical analyses of LVRSs, including compaction bands, showed that the normal stresses at the tips of LVRSs are compressive and significantly amplified with respect to the remote stresses, whereas on the flanks they are slightly reduced. These results can be used to rationalize the in-plane growth of PSSs for a certain distance, however, based on these stress conditions alone, it is not possible to explain the widening and transverse coalescence of PSSs. In this study, based on laboratory and field observations that the PSS surfaces are extremely rough, we introduced asperities with triangular, semicircular, and rectangular geometries on the flanks of the LVRSs into our mechanical model to see if these asperities can raise stresses in these locations, which may rationalize the transverse growth of PSSs. It is found that these asperities can produce strong stress perturbations on the LVRS flanks thereby inducing a significant increase in the compressive normal stresses. In addition, to account for the rate factor of the pressure solution process, a creep law was adopted to simulate growth and coalescence of the LVRSs. Using the calculated normal compressive stresses and volumetric plastic strains as proxy for the growth, we show that (1) a single LVRS is able to grow both laterally and transversely for a short distance and (2) two in-plane aligned neighboring LVRSs with a short distance between the adjacent tips and two parallel echelon and overlapped LVRSs with a small spacing may be able to link and coalesce to form a longer and wider LVRS, respectively. The influences of the LVRS geometric configurations, the material properties within the LVRSs, and the distance and spacing of the aligned in-plane, echelon, and overlapping neighboring parallel LVRSs on the growth and coalescence of the LVRSs are investigated and their implications specifically for the PSSs are also discussed.

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“…on a branched crack on an aircraft wheel rim made of 2014-T6 aluminum alloy [4]. Some analytical solutions have been obtained for the SIF of kinked and branched cracks, but it is generally recognized that it is very difficult to develop accurate analytical solutions to their complex propagation behavior [5][6][7][8][9]. Therefore, numerical methods such as Finite Elements (FE) and Boundary Elements (BE) are the only practical means to predict the propagation behavior of branched cracks [10].…”

Section: Introductionmentioning

confidence: 99%

Propagation Path and Fatigue Life Predictions of Branched Cracks Under Plane Strain Conditions

Meggiolaro

Miranda

Castro

et al.

Fracture of Nano and Engineering Materials and Structures

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Fatigue cracks can significantly deviate from their Mode I growth direction due to the influence of overloads, multi-axial stresses, micro structural inhomogeneities such as grain boundaries and interfaces, or environmental effects, generating crack kinking or branching [1]. The stress intensity factors (SIF) associated to branched fatigue cracks can be considerably smaller than that of a straight crack with the same projected length, causing crack growth retardation or even arrest. This mechanism can quantitatively explain retardation effects even when plasticity induced crack closure cannot be applied, e.g. in high R-ratio fatigue problems under plane strain conditions. Analytical solutions have been obtained for the SIF of some branched cracks, however numerical methods are the only means to predict the subsequent curved propagation behaviour. In this work, a specialized Finite Element program is used to calculate the propagation path and associated SIF of bifurcated cracks. The numerical calculations are validated through experiments on 4340 steel ESE(T) specimens. A total of 6,250 FE calculations are used to fit empirical equations to the process zone size and crack retardation factor along the curved crack branches. The bifurcation simulations include several combinations of bifurcation angles, branch asymmetry ratios, crack growth exponents, and even considers interaction between crack branching and other retardation mechanisms such as crack closure, assuming the crack opening level is well known.

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Why do cracks avoid each other?

Cited by 160 publications

References 4 publications

Repulsion and Attraction between a Pair of Cracks in a Plastic Sheet

Repulsion and Attraction between a Pair of Cracks in a Plastic Sheet

Mechanics of pressure solution seam growth and evolution

Propagation Path and Fatigue Life Predictions of Branched Cracks Under Plane Strain Conditions

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