scholarly journals Tribochemistry of Ionic Liquid Lubricant on Magnetic Media

2012 ◽  
Vol 2012 ◽  
pp. 1-20 ◽  
Author(s):  
Hirofumi Kondo
Keyword(s):  
Ionic Liquid ◽  
Ammonium Salt ◽  
Terminal Group ◽  
Friction Reduction ◽  
Magnetic Media ◽  
Stick Slip ◽  
Quarter Century ◽  
Liquid Lubricant ◽  
Frictional Properties ◽  
Stick Slip Motion

The newly synthesized perfluoropolyether (PFPE) ionic liquid whose terminal group is an ammonium salt with a carboxylic acid has better frictional properties when compared to the conventional PFPEs. Stick-slip motion was not observed even for the smooth surface for the modified PFPE tape. The friction is almost independent of the PFPE structure, but depends on the amine structures. The ammonium salt being tightly anchored to the rubbing surface covers uniformly, which leads to better lubricity. The higher dispersive interaction of the hydrophobic group of the amine is endowed with a compensating friction reduction. Steric hindrance of the hydrophilic group causes a high friction. Based on these findings, a saturated long chain ammonium salt is the best selection. Moreover, the modified PFPEs are dissolved in alcohol and hexane, which makes practical use convenient without any environmental problems. These ionic lubricants invented around 1987 have been used for magnetic tapes for about a quarter century because of their good lubricity and are reviewed in this paper.

Steady Sliding of Two Elastic Half-Spaces With Friction Reduction due to Interface Stick-Slip

1998 ◽  
Vol 65 (2) ◽  
pp. 470-475 ◽  
Author(s):  
G. G. Adams
Keyword(s):  
Friction Coefficient ◽  
Coefficient Of Friction ◽  
Dynamic Instability ◽  
Steady Motion ◽  
Friction Reduction ◽  
Stick Slip ◽  
Interface Friction ◽  
Stick Slip Motion ◽  
Frictional Slip ◽  
Slip Motion

The sliding of two perfectly flat elastic half-spaces with a constant interfacial coefficient of friction is investigated. Previous work has demonstrated that this configuration is dynamically unstable due to the destabilization of frictional slip waves. It was speculated that this dynamic instability could lead to stick-slip motion at the sliding interface. It is shown here that stick-slip motion at the interface can exist with a speed-independent interface coefficient of friction. Steady motion persists sufficiently far from the interface and thus gives the impression of uniform sliding. This type of stick-slip motion is due to interfacial slip waves and allows the bodies to slide with an apparent coefficient of friction which is less than the interface coefficient of friction. Furthermore it is shown that the apparent friction coefficient decreases with increasing speed even if the interface friction coefficient is speed-independent. Finally, it is shown that the presence of slip waves may make it possible for two frictional bodies to slide without a resisting shear stress and without any interface separation. No distinction is made between static and kinetic friction.

Drag-Reduction and Resonance Problems of a Jointed Drillstring in the Presence of an Axial Excitation Tool

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Xueying Wang ◽  
Hongjian Ni ◽  
Ruihe Wang ◽  
Lei Zhang ◽  
Peng Wang
Keyword(s):  
Drag Reduction ◽  
Friction Reduction ◽  
Drill Bit ◽  
Frictional Drag ◽  
Stick Slip ◽  
Axial Excitation ◽  
Weight On Bit ◽  
Vibration Responses ◽  
Stick Slip Motion ◽  
Slip Motion

Axial excitation tools (AETs) have the ability to improve slide-drilling efficiency by reducing the friction between the drillstring and the wellbore wall. However, drag-reduction effects are not always satisfactory, and excessive vibration may cause failures of downhole tools in some cases. Thus, a mathematical model was proposed to simulate the vibration responses of a drillstring. In the model, velocity-dependent friction is adopted to calculate the friction-reduction effect. The effect of drillstring joints on the weight on bit (WOB) was first investigated. The simulation results indicate that the joints intensify the stick-slip motion of the drillstring system. The effect of the location of an AET was then examined. The results show that it is better to place an AET near the drill bit rather than near the rear of a build section. Because the frictional drag acting on the lower portion of the drillstring dominates the axial stick-slip motion of a drill bit. Finally, the resonance responses were examined in terms of the drillstring system acceleration. The results show that resonance moderately increases the accelerations of a long horizontal drillstring system in a heavy-damping environment but that the growth of the exciting force can profoundly increase the accelerations.

Towards a Microscopic Description of Friction

2000 ◽  
Vol 651 ◽  
Author(s):  
Markus Porto ◽  
Veaceslav Zaloj ◽  
Michael Urbakh ◽  
Joseph Klafter
Keyword(s):  
Embedded System ◽  
Collective Modes ◽  
Spatial And Temporal Patterns ◽  
Microscopic Description ◽  
Stick Slip ◽  
Frictional Properties ◽  
Driven System ◽  
The Embedded System ◽  
Stick Slip Motion ◽  
Slip Motion

AbstractWe investigate the response of an embedded system subject to an external drive using a microscopic model. The shear is shown to excite “shearons”, which are collective modes of the embedded system with well defined spatial and temporal patterns that dominate the frictional properties of the driven system. We demonstrate that the slip relaxation in stick-slip motion and memory effects are well described in terms of the creation and/or annihilation of shearons.

Effects of Fabric Structure on Frictional Properties

1992 ◽  
Vol 62 (2) ◽  
pp. 87-93 ◽  
Author(s):  
Joseph O. Ajayi
Keyword(s):  
Linear Relation ◽  
Frictional Resistance ◽  
Woven Fabrics ◽  
Woven Fabric ◽  
Stick Slip ◽  
Frictional Properties ◽  
Fabric Structure ◽  
Pile Type ◽  
Stick Slip Motion ◽  
Slip Motion

When the yarn sett of a woven fabric is systematically increased, there is also a systematic increase in the frictional resistance to motion, and it is greater for weft-over-weft motion than for warp-over-warp. The greater warp crimp producing a “knuckle effect” could be the explanation, although the diminishing spaces between the weft threads could also be a factor. In another case involving a series of pile-type woven fabrics, an increase in the height of fiber tufts produces an increase in the resistance to motion and also the amplitude of the stick-slip motion. A good linear relation exists between the number of peaks and number of cords. The size of cords and the degree of spacing between them may enhance interlocking and intermeshing of fiber pile.

scholarly journals A model of processive walking and slipping of kinesin-8 molecular motors

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ping Xie
Keyword(s):  
Single Molecule ◽  
Molecular Motors ◽  
External Load ◽  
Molecular Motor ◽  
Velocity Versus ◽  
Stick Slip ◽  
Load Dependence ◽  
Chemomechanical Coupling ◽  
Similarities And Differences ◽  
Stick Slip Motion

AbstractKinesin-8 molecular motor can move with superprocessivity on microtubules towards the plus end by hydrolyzing ATP molecules, depolymerizing microtubules. The available single molecule data for yeast kinesin-8 (Kip3) motor showed that its superprocessive movement is frequently interrupted by brief stick–slip motion. Here, a model is presented for the chemomechanical coupling of the kinesin-8 motor. On the basis of the model, the dynamics of Kip3 motor is studied analytically. The analytical results reproduce quantitatively the available single molecule data on velocity without including the slip and that with including the slip versus external load at saturating ATP as well as slipping velocity versus external load at saturating ADP and no ATP. Predicted results on load dependence of stepping ratio at saturating ATP and load dependence of velocity at non-saturating ATP are provided. Similarities and differences between dynamics of kinesin-8 and that of kinesin-1 are discussed.

scholarly journals Effect of water on the electroresponsive structuring and friction in dilute and concentrated ionic liquid lubricant mixtures

2020 ◽  
Vol 22 (48) ◽  
pp. 28191-28201
Author(s):  
Georgia A. Pilkington ◽  
Rebecca Welbourn ◽  
Anna Oleshkevych ◽  
Seiya Watanabe ◽  
Patricia Pedraz ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Ionic Liquid ◽  
Neutron Reflectivity ◽  
Force Microscopy ◽  
Liquid Lubricant ◽  
Effect Of Water ◽  
Atomic Force ◽  
Ambient Levels

The influence of ambient levels of water on the electroresponsive interfacial structuring and nanofriction of ionic liquid lubricant mixtures has been investigated by neutron reflectivity and atomic force microscopy.

Dynamics of stick–slip motion, Whillans Ice Stream, Antarctica

2011 ◽  
Vol 305 (3-4) ◽  
pp. 283-289 ◽  
Author(s):  
J. Paul Winberry ◽  
Sridhar Anandakrishnan ◽  
Douglas A. Wiens ◽  
Richard B. Alley ◽  
Knut Christianson
Keyword(s):  
Stick Slip ◽  
Ice Stream ◽  
Whillans Ice Stream ◽  
Stick Slip Motion ◽  
Slip Motion

GRANULAR FAILURE: THE ORIGIN OF EARTHQUAKES?

2009 ◽  
Vol 23 (28n29) ◽  
pp. 5374-5382 ◽  
Author(s):  
MASSIMO PICA CIAMARRA ◽  
LUCILLA DE ARCANGELIS ◽  
EUGENIO LIPPIELLO ◽  
CATALDO GODANO
Keyword(s):  
Confining Pressure ◽  
Stick Slip ◽  
Slip Regime ◽  
Constant Rate ◽  
Large Fluctuations ◽  
System Flow ◽  
System Phase Diagram ◽  
Dynamics Simulations ◽  
Stick Slip Motion ◽  
System Phase

Via Molecular Dynamics simulations, we investigate the stick-slip motion in a model of fault, where two surfaces subject to a constant confining pressure P, and enclosing granular particles, are subject a shear stress σ. When the system sticks, the stress increases with a constant rate [Formula: see text], while the stress decreases when the system flow. We dermine the system 'phase diagram' in the pressure P load velocity [Formula: see text] plane, locating the transition form the continuos flow regime to the stick-slip regimes, and show that the transition between these two regimes is characterized by the presence of large fluctuations. In the stick-slip regime, the system reproduces the behaviour of a segment of a fault of fixed lenght.

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