Shear-induced crystallization of an amorphous system

Мокшин, А. В.; Barrat, Jean‐Louis

doi:10.1103/physreve.77.021505

Cited by 49 publications

(56 citation statements)

References 35 publications

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“…Inhomogeneous shear has also been observed for heterogeneous fluids [9][10][11] shear rates comparable to EHL [13,53] and in molecular dynamics simulations of 5 amorphous systems [54]. They have also been suggested for the EHL condition [7].…”

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confidence: 70%

Through-Thickness Velocity Profile Measurements in an Elastohydrodynamic Contact

2013

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7594 8991This work presents for the first time through-thickness velocity profiles obtained in an EHL contact by photobleached imaging. The velocity profile was inferred by following the evolution of the shape of a photobleached plug formed through the thickness of the fluorescently-doped lubricant, oligomer polybutene (PB), in the contact when shear was applied. The proposed methodology was validated by successfully obtaining the expected linear profile with PB experiencing Couette flow. The methodology was then applied to PB in an EHL contact. The variation of the profiles within the contact area was also investigated.The velocity profile of PB in an EHL contact severely deviates from the common linear assumption and exhibits inhomogeneous shear: three regions of varying shear rate have been observed. The phenomenon is shown to be neither due to thermal nor diffusion effects. PB also shows significant slip at the glass-liquid interface. The amount of slip varies with position in the contact. Possible causes, such as pressure induced viscosity enhancement, as well as the significance of the findings and the benefits of the technique are discussed.The linear velocity profile in an EHL contact is usually assumed for both the film thickness and friction predictions. The profile has however never been measured experimentally until now. This work enables the validation of conventional assumptions and the study of flow heterogeneity of lubricants in a contact. This facilitates an improved understanding of the rheology of confined lubricant and hence more accurate predictions of tribological properties.

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confidence: 70%

Through-Thickness Velocity Profile Measurements in an Elastohydrodynamic Contact

2013

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“…The shear deformations are introduced by moving one wall in the shear direction 68 . We find that both energetic and structural properties of the system depend strongly on the shear velocity and the imposed strain, as well as the temperature at which the deformations are applied.…”

Section: Discussionmentioning

confidence: 99%

Amorphous silicon under mechanical shear deformations: Shear velocity and temperature effects

2011

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Mechanical shear deformations lead, in some cases, to effects similar to those resulting from ion irradiation. Here we characterize the effects of shear velocity and temperature on amorphous silicon (a-Si) modelled using classical molecular dynamics simulations based on the empirical Environment Dependent Inter-atomic Potential (EDIP). With increasing shear velocity at low temperature, we find a systematic increase in the internal strain leading to the rapid appearance of structural defects (5-fold coordinated atoms). The impacts of externally applied strain can be almost fully compensated by increasing the temperature, allowing the system to respond more rapidly to the deformation. In particular, we find opposite power-law relations between the temperature and the shear velocity and the deformation energy. The spatial distribution of defects is also found to strongly depend on temperature and strain velocity. For low temperature or high shear velocity, defects are concentrated in a few atomic layers near the center of the cell while, with increasing temperature or decreasing shear velocity, they spread slowly throughout the full simulation cell. This complex behavior can be related to the structure of the energy landscape and the existence of a continuous energy-barrier distribution.

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“…Crystallization is promoted by a low fluid complexity, a high degree of molecular ordering at the walls and an initially crystallized fluid [22,[26][27][28]. Regarding fluid complexity, it can be noted here that previous studies have mainly concerned simple Lennard-Jones fluids, which are monatomic systems [22,23,29,30]. Only a few authors have considered a binary mixture model [23,31,32], which was originally designed to frustrate crystallization in supercooled liquids.…”

Section: Regimes Experienced By the Lubricantmentioning

confidence: 99%

Lubrication at Extreme Conditions: A Discussion About the Limiting Shear Stress Concept

Martinie

Vergne

2016

Tribol Lett

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Although limiting shear stress is a common behavior that is observed in many highly loaded lubricated contacts, its physical origins are still a matter of debate. Several scenarios are proposed in the literature to explain the macroscopic manifestations of the shearing response of a thin film of highly pressurized lubricant. Experimental measurements have been taken to capture these scenarios. However, limiting shear stress has never been simultaneously measured to validate any of them. Over the last decade, more and more molecular dynamics simulations have been performed to go further into details that are experimentally unattainable. This paper aims at comparing both approaches to studying the limiting shear stress, and more specifically at experimentally validating a lubricant phase diagram derived from molecular dynamics simulations. It suggests that the physical mechanism that initiates limiting shear stress is shear localization.

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Shear-induced crystallization of an amorphous system

Cited by 49 publications

References 35 publications

Through-Thickness Velocity Profile Measurements in an Elastohydrodynamic Contact

Through-Thickness Velocity Profile Measurements in an Elastohydrodynamic Contact

Amorphous silicon under mechanical shear deformations: Shear velocity and temperature effects

Lubrication at Extreme Conditions: A Discussion About the Limiting Shear Stress Concept

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