Discontinuous crack fronts of three-dimensional fractures

Tanaka, Yoshikazu; Fukao, Koji; Miyamoto, Yoshihisa; Sekimoto, Ken

doi:10.1209/epl/i1998-00485-9

Cited by 2 publications

(3 citation statements)

References 18 publications

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“…4(c)) is steep near this point and becomes shallower as we move away from it. As noted in previous studies 6,7 , these observations indicate that the crack front is separated into two discontinuous segments that overlap at a step to form a continuous fracture surface, with the curved segment lagging behind the flat segment. The overlap is responsible for the formation of the hidden surface.…”

supporting

confidence: 79%

“…Plausibly, steps grow following nucleation due to branching repulsion and are later stabilized by the long-range restoring shear stresses that act along the front 10 . The non-trivial topology of step-forming crack fronts, then, prevents them from decaying to a flat state; crack faces cannot be continuously deformed to a flat configuration, the hallmark of a topological defect 6,7 .…”

mentioning

confidence: 99%

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Topological defects govern crack front motion and facet formation on broken surfaces

2017

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Cracks develop intricate patterns on the surfaces that they create. As faceted fracture surfaces are commonly formed by slow tensile cracks in both crystalline and amorphous materials, facet formation and structure cannot reflect microscopic order. Although fracture mechanics predict that slow crack fronts should be straight and form mirror-like surfaces, facet-forming fronts propagate simultaneously within different planes separated by steps. Here we show that these steps are topological defects of crack fronts and that crack front separation into disconnected overlapping segments provides the condition for step stability. Real-time imaging of propagating crack fronts combined with surface measurements shows that crack dynamics are governed by localized steps that drift at a constant angle to the local front propagation direction while their increased dissipation couples to long-ranged elasticity to determine front shapes. We study how three-dimensional topology couples to two-dimensional fracture dynamics to provide a fundamental picture of how patterned surfaces are generated.

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supporting

confidence: 79%

mentioning

confidence: 99%

Topological defects govern crack front motion and facet formation on broken surfaces

2017

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“…A small mode III component is sufficient to cause simple cracks to break up into discrete segments separated by sharp propagating steps. As these cracks propagate across a crack front, they leave in their wake segmented, faceted fracture surfaces (Tanaka et al, 1998;Lazarus et al, 2008;Baumberger et al, 2008;Pham and Ravi-Chandar, 2014). Phase-field modeling has shown that a planar crack can indeed become faceted (Pons and Karma, 2010), when K III /K I crosses a materialdependent threshold (Leblond et al, 2011).…”

Section: Simple and Not So Simple Cracksmentioning

confidence: 99%

How hidden 3D structure within crack fronts reveals energy balance

Wang,

Adda-Bedia,

Kolinski

et al. 2022

Preprint

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Griffith's energetic criterion, or 'energy balance', has for a century formed the basis for fracture mechanics; the energy flowing into a crack front is precisely balanced by the dissipation (fracture energy) at the front. If the crack front structure is not properly accounted for, energy balance will either appear to fail or lead to unrealistic results. Here, we study the influence of the secondary structure of low-speed crack propagation in hydrogels under tensile loading conditions. We first show that these cracks are bistable; either simple (cracks having no secondary structure) or faceted crack states (formed by steps propagating along crack fronts) can be generated under identical loading conditions. The selection of either crack state is determined by the form of the initial 'seed' crack; perfect seed cracks generate simple cracks while a small local mode III component generates crack fronts having multiple steps.Step coarsening eventually leads to single steps that propagate along crack fronts. As they evolve, steps locally change the instantaneous structure and motion of the crack front, breaking transverse translational invariance. In contrast to simple cracks, faceted cracks can, therefore, no longer be considered as existing in a quasi-2D system. For both simple and faceted cracks we simultaneously measure the energy flux and local dissipation along these crack fronts over velocities, v, spanning 0 < v < 0.2c R (c R is the Rayleigh *

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Discontinuous crack fronts of three-dimensional fractures

Cited by 2 publications

References 18 publications

Topological defects govern crack front motion and facet formation on broken surfaces

Topological defects govern crack front motion and facet formation on broken surfaces

How hidden 3D structure within crack fronts reveals energy balance

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