Dynamics of squeeze-out: Theory and experiments

Zilberman, S.; Becker, Thomas; Mugele, Friedrich Gunther; Persson, B. N. J.; Nitzan, Abraham

doi:10.1063/1.1574790

Cited by 12 publications

(11 citation statements)

References 29 publications

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“…5,6 The contact surrounded by a liquid condensate is similar to the surface contact in the bulk liquid. However, the hydrostatic pressure in the condensate is lower than that in the bulk liquid by the value of the Laplace pressure, 32 and the pressure difference increases with decreasing rvp. According to the results, the capillary force between the surfaces dominates the pull-off force in the cyclohexane vapor close to saturation.…”

Section: Discussionmentioning

confidence: 96%

“…The second and determining mechanism for stable stick-slip, which would account for the stick-slip observed at high rvp, may be the process of shear-induced melting and freezing of molecular thin films , or energy dissipation at the molecular layer interface, , as has been suggested in explaining the observed friction between mica surfaces in bulk cyclohexane liquid. , The contact surrounded by a liquid condensate is similar to the surface contact in the bulk liquid. However, the hydrostatic pressure in the condensate is lower than that in the bulk liquid by the value of the Laplace pressure, and the pressure difference increases with decreasing rvp. According to the results, the capillary force between the surfaces dominates the pull-off force in the cyclohexane vapor close to saturation.…”

Section: Discussionmentioning

confidence: 96%

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Influence of Cyclohexane Vapor on Stick-Slip Friction between Mica Surfaces

et al. 2007

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Stick-slip friction between mica surfaces under cyclohexane vapor has been investigated with the Surface Force Apparatus. The dynamic shear stress decreased from 60 to 10 MPa with increasing relative vapor pressure (rvp) from 5% to 50%. Between a rvp of 50% and 80%, the shear stress remained at approximately 10 MPa, with a slight decrease on increasing the rvp. At a rvp greater than 80%, the values of shear stress were below 5 MPa. The stick-slip behavior was observed in the rvp range of 20% to saturation. When the rvp reached 20%, stick-slip appeared but faded out with sliding time. At a rvp greater than 50%, the stick-slip pattern was stable without fading. By taking into account the size of the meniscus formed by capillary condensation of the liquid around the contact area and the Laplace pressure, the dependence of shear stress and the stick-slip modulation on rvp suggests that the origin of the stick-slip observed in cyclohexane vapor is as follows: At a rvp greater than 50%, where stable sick-slip is observed, the stick-slip caused by the cyclohexane layering in the contact area is of essentially the same origin as that observed with mica surfaces sliding in bulk cyclohexane liquid. As with the bulk liquid experiment, decreasing the layer thickness (or the number of the layers) between the surfaces increases the shear stress at the onset of slip. In the vapor phase experiments, the stick-slip is enhanced by the increase of the negative Laplace pressure in the capillary condensed liquid, thereby forcing the surfaces toward each other more strongly with decreasing rvp. In the rvp range between 20% and 50%, where the fading stick-slip is observed, the condensate liquid seeps into the contact area under the influence of the applied tangential force and thus triggers the slip motion. Due to the small condensation volume, the liquid condensed around the contact area is exhausted in the process of repeating stick-slip. As the slip length is limited to the meniscus size, the stick-slip amplitude becomes smaller, and eventually the surfaces start sliding without stick-slip.

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Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 96%

Influence of Cyclohexane Vapor on Stick-Slip Friction between Mica Surfaces

et al. 2007

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“…The contact surrounded by a liquid condensate is similar to the surface contact in the bulk liquid. However, the hydrostatic pressure in the condensate is lower than that in the bulk liquid by the value of the Laplace pressure [13], and the pressure difference increases with decreasing rvp.…”

Section: Resultsmentioning

confidence: 96%

Friction and Capillary Forces at the Nanometer Scale

Ohnishi

2009

e-J. Surf. Sci. Nanotechnol.

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Frictional behaviors between mica surfaces have been investigated with the Surface Force Apparatus under various relative vapor pressures (rvp) of both water and cyclohexane. Stick-slip frictional behaviors were observed only under cyclohexane vapor. At rvp of 20%, stick-slip appeared but faded out with sliding time. At a rvp greater than 50%, the stick-slip pattern was stable without fading. Dependence of sliding velocity and applied load on stick-slip motions indicated that the mechanism of the stick-slips in the high rvp (stable stick-slip) region differs from that of the region of fading stick-slip. In the rvp range between 20% and 50%, where the fading stick-slip is observed, the condensate liquid seeps into the contact area under the influence of the applied tangential force and thus triggers the slip motion. Due to the small condensation volume, the liquid condensed around the contact area is exhausted in the process of repeating stick-slip. At a rvp greater than 50%, where stable sick-slip is observed, the stick-slip caused by essentially the same origin as that observed with mica surfaces sliding in bulk cyclohexane liquid. In vapor, the stick-slip is enhanced by the increase of the negative Laplace pressure in the capillary condensed liquid, thereby forcing the surfaces toward each other more strongly with decreasing rvp.

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“…1 Full understanding of this phenomenon demands for a comprehensive characterization of junctions' properties down to their nanoscale features; this emerges especially through surface force apparatus experiments, 2-7 analytical theories, 8,9 and molecular dynamics ͑MD͒ simulations, [10][11][12][13] attesting a significant dependence of lubricant thinning and shear dynamics on intermolecular forces, atomic-scale roughness, and contaminants. Such complexity seriously affects our predictive capabilities and often limits reproducibility of experimental results.…”

Section: Introductionmentioning

confidence: 99%

Friction laws for lubricated nanocontacts

Buzio

Boragno

Valbusa

2006

The Journal of Chemical Physics

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We have used friction force microscopy to probe friction laws for nanoasperities sliding on atomically flat substrates under controlled atmosphere and liquid environment, respectively. A power law relates friction force and normal load in dry air, whereas a linear relationship, i.e., Amontons' law, is observed for junctions fully immersed in model lubricants, namely, octamethylciclotetrasiloxane and squalane. Lubricated contacts display a remarkable friction reduction, with liquid and substrate specific friction coefficients. Comparison with molecular dynamics simulations suggests that load-bearing boundary layers at junction entrance cause the appearance of Amontons' law and impart atomic-scale character to the sliding process; continuum friction models are on the contrary of limited predictive power when applied to lubrication effects. An attempt is done to define general working conditions leading to the manifestation of nanoscale lubricity due to adsorbed boundary layers.

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Dynamics of squeeze-out: Theory and experiments

Cited by 12 publications

References 29 publications

Influence of Cyclohexane Vapor on Stick-Slip Friction between Mica Surfaces

Influence of Cyclohexane Vapor on Stick-Slip Friction between Mica Surfaces

Friction and Capillary Forces at the Nanometer Scale

Friction laws for lubricated nanocontacts

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