Nonmonotonicity of the Frictional Bimaterial Effect

Aldam, Michael; Xu, Shiqing; Brener, Efim A.; Ben‐Zion, Yehuda; Bouchbinder, Eran

doi:10.1002/2017jb014665

Cited by 6 publications

(6 citation statements)

References 93 publications

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“…This excellent correspondence with measured strains might be surprising in light of our neglect of the coupling of frictional strength to σ yy . The analytic and numerical solutions at the interface, however, reveal that magnitudes of Δσ yy for slow velocities are relatively small (16,29). A(x, t) measurements, reflecting Δσ yy (x, y = 0, t), are consistent with these predictions, having no significant variation behind the rupture tip.…”

Section: Resultsmentioning

confidence: 58%

The onset of the frictional motion of dissimilar materials

Shlomai

Kammer

Adda-Bedia

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Frictional motion between contacting bodies is governed by propagating rupture fronts that are essentially earthquakes. These fronts break the contacts composing the interface separating the bodies to enable their relative motion. The most general type of frictional motion takes place when the two bodies are not identical. Within these so-called bimaterial interfaces, the onset of frictional motion is often mediated by highly localized rupture fronts, called slip pulses. Here, we show how this unique rupture mode develops, evolves, and changes the character of the interface’s behavior. Bimaterial slip pulses initiate as “subshear” cracks (slower than shear waves) that transition to developed slip pulses where normal stresses almost vanish at their leading edge. The observed slip pulses propagate solely within a narrow range of “transonic” velocities, bounded between the shear wave velocity of the softer material and a limiting velocity. We derive analytic solutions for both subshear cracks and the leading edge of slip pulses. These solutions both provide an excellent description of our experimental measurements and quantitatively explain slip pulses’ limiting velocities. We furthermore find that frictional coupling between local normal stress variations and frictional resistance actually promotes the interface separation that is critical for slip-pulse localization. These results provide a full picture of slip-pulse formation and structure that is important for our fundamental understanding of both earthquake motion and the most general types of frictional processes.

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Section: Resultsmentioning

confidence: 58%

The onset of the frictional motion of dissimilar materials

Shlomai

Kammer

Adda-Bedia

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…The linear stability results for the elastic bimaterial problem [36,38] are mathematically identical to those describing the undrained poroelastic problem (where…”

Section: Correspondence Between Undrained Poroelastic and Elastic Bimaterials Problemsmentioning

confidence: 85%

“…Slip localization to the boundary of the core thus gives rise to an asymmetry that favors propagation in one direction, with the favorable direction determined by which boundary of the core hosts the slip surface. A related bimaterial effect altering normal stress occurs during sliding between elastically dissimilar solids [24,36,37,38]. The strong sense of directionality in both the poroelastic and elastic bimaterial problems is a characteristic property of slip pulses (Fig.…”

Section: Fault Structure Poroelastic Effects and Coupling To Fault Strengthmentioning

confidence: 99%

Poroelastic effects destabilize mildly rate-strengthening friction to generate stable slow slip pulses

Heimisson

Dunham

Almquist

2019

Journal of the Mechanics and Physics of Solids

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Slow slip events on tectonic faults, sliding instabilities that never accelerate to inertially limited ruptures or earthquakes, are one of the most enigmatic phenomena in frictional sliding. While observations of slow slip events continue to mount, a plausible mechanism that permits instability while simultaneously limiting slip speed remains elusive. Rate-andstate friction has been successful in describing most aspects of rock friction, faulting, and earthquakes; current explanations of slow slip events appeal to rate-weakening friction to induce instabilities, which are then stalled by additional stabilizing processes like dilatancy or a transition to rate-strengthening friction at high slip rates. However, the temperatures and/or clay-rich compositions at slow slip locations are almost ubiquitously associated with rate-strengthening friction. In this study, we propose a fundamentally different instability mechanism that may reconcile this contradiction, demonstrating how slow slip events can nucleate with mildly rate-strengthening friction. We identify two destabilizing mechanisms, both reducing frictional shear strength through reductions in effective normal stress, that counteract the stabilizing effects of rate-strengthening friction. The instability develops into slow slip pulses. We quantify parameter controls on pulse length, propagation speed, and other characteristics, and demonstrate broad consistency with observations of tectonic slow slip events as well as laboratory tribology experiments.

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“… μ ∗ is a universal function of the rupture speed and the material contrast as well as other material parameters (Ranjith & Rice, 2001; Rice et al., 2001) and can be analytically calculated. μ ∗ may also depend on sample geometry (Aldam et al., 2016, 2017). The coupling in Equation 1 between the local slip and the local normal stress variations along bimaterial interfaces is called bimaterial coupling .…”

Section: Introductionmentioning

confidence: 99%

Supershear Frictional Ruptures Along Bimaterial Interfaces

et al. 2020

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We experimentally and analytically explore supershear ruptures that are excited at the onset of frictional motion within “bimaterial interfaces,” frictional interfaces formed by contacting bodies having different elastic (or geometric) properties. Our experiments on PMMA blocks sliding on polycarbonate show that the structure, transition sequence, and range of existence of such supershear ruptures are highly dependent on their propagation direction relative to the slip direction in the softer of the two materials. These properties are characterized for both the positive (parallel) and negative (antiparallel) propagation directions. An analytic, fracture‐mechanics based description of supershear ruptures is derived. The theory quantitatively predicts both supershear structure and the allowed propagation range of supershear ruptures. The latter compares well with both the experimentally observed supershear ruptures in the negative direction as well as localized slip pulses in the positive direction, whose propagation speed lies between the shear velocities of both materials. Supershear ruptures in the positive direction, which are composed of trains of propagating slip pulses, evade this theoretical description.

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Nonmonotonicity of the Frictional Bimaterial Effect

Cited by 6 publications

References 93 publications

The onset of the frictional motion of dissimilar materials

The onset of the frictional motion of dissimilar materials

Poroelastic effects destabilize mildly rate-strengthening friction to generate stable slow slip pulses

Supershear Frictional Ruptures Along Bimaterial Interfaces

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