Crack Front Dynamics: The Interplay of Singular Geometry and Crack Instabilities

Kolvin, Itamar; Cohen, Gil; Fineberg, Jay

doi:10.1103/physrevlett.114.175501

Cited by 26 publications

(29 citation statements)

References 32 publications

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“…This slight slowdown of the crack front prior to branching has also been observed in [20]. As described in [25], the release of the crack front from the branch arrest leads to an increase of crack velocity and apparent fracture energy ahead of the first event and eventually forms a new branching event along FIG. 3.…”

mentioning

confidence: 71%

“…4). By recording these quantities for many patterns exhibiting this quasi-periodic regime we show, first, that L branch and ∆x are positively correlated, suggesting that the nucleation of the next branching event is directly related to the death of the previous one as proposed in [25]. Moreover, the plate width W seems to have no influence on selecting the microbranch length scale contrary to l 0 .…”

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confidence: 92%

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Microbranching instability in phase-field modelling of dynamic brittle fracture

Bleyer

Molinari

2017

Applied Physics Letters

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The microbranching instability occurring for rapidly propagating cracks in brittle materials has been described in various experiments as an intrinsically three-dimensional phenomenon. Using a variational phase-field model, we show that the microbranching process is, indeed, a threedimensional instability which exhibits a strong dependence on the sample width and can be suppressed for very thin samples. We show that the phase-field internal length scale is the decisive variable governing the branching pattern, which can be either localized in the transverse direction as observed in glass for example, or, on the contrary, almost translational invariant with quasiperiodic structures, as observed in PMMA.

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confidence: 71%

mentioning

confidence: 92%

Microbranching instability in phase-field modelling of dynamic brittle fracture

Bleyer

Molinari

2017

Applied Physics Letters

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“…This "frustrated curved section" is what we identify as a micro-branch beneath the fracture surface. Such a pinch-off scenario been recently observed experimentally by direct visualization of crack fronts in the xz plane as micro-branching takes place [110]. The micro-branch locally delays the crack front causing local crack front curvature within the xz (fracture) plane.…”

Section: Three-dimensional Tensile Cracks: Micro-branching Front mentioning

confidence: 92%

“…The experimentally observed propagative modes were different from the theoretically predicted in-plane front waves in two important aspects: (i) They featured an out-of-plane component, which left marks on the fracture surfaces and, in fact, enabled post-mortem measurements of crack front waves (in-plane perturbations do not leave any post-mortem fractographic signature) (ii) They were clearly nonlinear, exhibiting soliton-like properties [25]. While similar fracture surface markings can be generated by the interaction of shear waves with moving crack fronts [126][127][128], recent measurements in both brittle gels [53,110] and the rapid fracture of rock [28,129] have strengthened the evidence for the existence of front waves in dynamic fracture.…”

Section: Three-dimensional Tensile Cracks: Micro-branching Front mentioning

confidence: 99%

Recent developments in dynamic fracture: some perspectives

Fineberg

Bouchbinder

2015

Int J Fract

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We briefly review a number of important recent experimental and theoretical developments in the field of dynamic fracture. Topics include experimental validation of the equations of motion for straight tensile cracks (in both infinite media and strip geometries), validation of a new theoretical description of the near-tip fields of dynamic cracks incorporating weak elastic nonlinearities, a new understanding of dynamic instabilities of tensile cracks in both 2D and 3D, crack front dynamics, and the relation between frictional motion and dynamic shear cracks. Related future research directions are briefly discussed.

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“…In polyacrylamide gels [6] cracks exhibit a transition between facet formation and micro-branching at v ∼ 0.05 − 0.1c R . The transition is not sharp, and both types of structures may coexist in the transition region.…”

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confidence: 99%

Nonlinear Focusing in Dynamic Crack Fronts and the Microbranching Transition

2017

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Cracks in brittle materials produce two types of generic surface structures: facets at low velocities and micro-branches at higher ones. Here we observe a transition from faceting to micro-branching in polyacrylamide gels that is characterized by nonlinear dynamic localization of crack fronts. To better understand this process we derive a first-principles nonlinear equation of motion for crack fronts in the context of scalar elasticity. Its solution shows that nonlinear focusing coupled to rate-dependence of dissipation governs the transition to micro-branching.Fracture is typically an irregular process. Cracks show a strong tendency for instability, creating non-smooth surfaces with rich structure. Crack instabilities and their associated structure exhibit a strong dependence on crack velocity: slow tensile cracks (v c R , where c R is the Rayleigh wave speed) are prone to nucleate steps which drift along the crack front and divide the fracture surface into facets [1-6]; faster tensile cracks are unstable to the formation of micro-branches -microscopic cracks that branch off the main crack front [7][8][9][10][11]. Linear perturbation theory, however, predicts that any initial disturbance to a tensile crack front should either decay as the crack progresses [12][13][14] or disperse as outgoing waves [15,16]. Current linear theories are therefore incapable of reproducing the observed fracture surfaces.In recent non-perturbative approaches to fracture, such as lattice models [17,18] and phase-field models [19][20][21], localized crack branching arises naturally, regardless of the specific dissipative process. Both approaches predict that micro-branching is governed by the microscopic dissipation length-scale and that instability initiates at v c ∼ 0.7c R . This critical velocity is significantly higher than that observed in experiments, and predicted from energy considerations in the theory of 2D branching [22,23]. In addition, micro-branch dimensions typically exceed the process zone size by a few orders of magnitude. It therefore remains unclear what component or mechanism is missing in the existing models.In polyacrylamide gels [6] cracks exhibit a transition between facet formation and micro-branching at v ∼ 0.05 − 0.1c R . The transition is not sharp, and both types of structures may coexist in the transition region. A typical fracture surface (for v ∼ 0.06c R ) shown in Fig.

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Crack Front Dynamics: The Interplay of Singular Geometry and Crack Instabilities

Cited by 26 publications

References 32 publications

Microbranching instability in phase-field modelling of dynamic brittle fracture

Microbranching instability in phase-field modelling of dynamic brittle fracture

Recent developments in dynamic fracture: some perspectives

Nonlinear Focusing in Dynamic Crack Fronts and the Microbranching Transition

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