On a Model for the Prediction of the Friction Coefficient in Mixed Lubrication Based on a Load-Sharing Concept with Measured Surface Roughness

Akchurin, Aydar; Bosman, Rob; Lugt, Piet M.; Drogen, Mark van

doi:10.1007/s11249-015-0536-z

Cited by 36 publications

(38 citation statements)

References 34 publications

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“…To simulate contact of two opposing surfaces resulting from lithostatic pressure in Geo‐energy reservoirs (represented by σ 3 ′ in the experiments), a half space‐based, dry contact model from Tribonet was used (Akchurin et al, 2015; Lubrecht & Ioannides, 1991; Tribonet n.d.). The model uses the artificially generated surfaces discretized to either 2,048 × 682 (for model calibration) or 768 × 256 nodes (for parametric analysis).…”

Section: Numerical Modeling Of Fracture Transmissivity (Under Normal mentioning

confidence: 99%

Hydraulic Transport Through Calcite Bearing Faults With Customized Roughness: Effects of Normal and Shear Loading

2020

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Understanding fluid flow in rough fractures is of high importance to large scale geologic processes and to most anthropogenic geo‐energy activities. Here we conducted fluid transport experiments on Carrara marble fractures with a novel customized surface topography. Transmissivity measurements were conducted under mechanical loading conditions representative of deep geothermal reservoirs (normal stresses from 20 to 70 MPa and shear stresses from 0 to 30 MPa). A numerical procedure simulating normal contact and fluid flow through fractures with complex geometries was validated toward experiments. Using it, we isolated the effects of roughness parameters on fracture fluid flow. Under normal loading, we find that (i) the transmissivity decreases with normal loading and is strongly dependent on fault surface geometry and (ii) the standard deviation of heights (hRMS) and macroscopic wavelength of the surface asperities control fracture transmissivity. Transmissivity evolution is nonmonotonic, with more than 4 orders of magnitude difference for small variations of macroscopic wavelength and hRMS roughness. Reversible elastic shear loading has little effect on transmissivity; it can increase or decrease depending on contact geometry and overall stress state on the fault. Irreversible shear displacement (up to 1 mm offset) slightly decreases transmissivity and its variation with irreversible shear displacements can be predicted numerically and geometrically at low normal stress only. Finally, irreversible changes in surface roughness (plasticity and wear) due to shear displacement result in a permanent decrease of transmissivity when decreasing differential stress. Generally, reduction of a carbonate fault's effective stress increases its transmissivity while inducing small shear displacements does not.

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Section: Numerical Modeling Of Fracture Transmissivity (Under Normal mentioning

confidence: 99%

Hydraulic Transport Through Calcite Bearing Faults With Customized Roughness: Effects of Normal and Shear Loading

2020

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“…Spikes presented the basics of elastohydrodynamic lubrication and its practical applications. Previously, a number of studies have been reported to model the EHL/mixed‐EHL regime in concentrated contacts under rolling/sliding conditions . In those papers, a load‐sharing concept originally developed by Johnson et al was employed, and a variation of the friction coefficient was shown for the various experimental conditions (very high to low load, the effect of surface roughness, etc.…”

Section: Introductionmentioning

confidence: 99%

Effect of topography parameter, load, and surface roughness on friction coefficient in mixed lubrication regime

Prajapati

Tiwari

2019

Lubrication Science

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Surface topography parameters significantly control physical processes which have asperity‐to‐asperity contacts in tribological components undergoing friction and wear. In this study, the effect of correlation length, maximum contact load, and surface roughness on friction coefficient and load distribution is studied. The load‐sharing concept is employed to determine friction coefficient and load distribution in the mixed‐lubrication regime. Results clearly demonstrate the effect of correlation length on friction coefficient and load distribution. It is found that the lower value of the coefficient of friction may be achieved even at low velocity for the smooth surface as compared with rough surfaces having higher surface roughness. For a particular value of velocity, the coefficient of friction decreases with an increase in maximum contact load. This work will help in predicting the coefficient of friction in the mixed‐lubrication regime for the engineering surfaces produced by processes like grinding, which is the result of an abrasive action.

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“…In fact, the separation distance h s has the same shape as the film thickness h but with a constant offset ε so that volume conservation is preserved (see Akchurin et al. 30 for more details), as can be inferred from Figure 3. The offset ε is obtained iteratively in the asperity contact model, by satisfying the following equation where A is the total area and A∼ is the lubricated area.…”

Section: Mathematical Model: Mixed Lubricationmentioning

confidence: 95%

“…In fact, for the normal contact pressures p a calculation the elastic-perfectly plastic contact model of Akchurin et al 30 is employed. For the tangential contact problem, the model of Bazrafshan et al 31 is employed.…”

Section: Asperity Contact Componentmentioning

confidence: 99%

The influence of stick–slip transitions in mixed-friction predictions of heavily loaded cam–roller contacts

Alakhramsing

Rooij

Drogen

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part J:

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A load-sharing-based mixed lubrication model, applicable to cam-roller contacts, is developed. Roller slippage is taken into account by means of a roller friction model. Roughness effects in the dry asperity contact component of the mixed lubrication model are taken into account by measuring the real surface topography. The proportion of normal and tangential load due to asperity interaction is obtained from a dry contact stick-slip solver. Lubrication conditions in a cam-roller follower unit, as part of the fuel injection equipment in a heavy-duty diesel engine, are analyzed. Main findings are that stick-slip transitions (or variable asperity contact friction coefficient) are of crucial importance in regions of the cam where the acting contact forces are very high. The contact forces are directly related to the sliding velocity/roller slippage at the cam-roller contact and thus also to the static friction mechanism of asperity interactions. Assuming a constant asperity contact friction coefficient (or assuming that gross sliding has already occurred) in highly loaded regions may lead to large overestimation in the minimal required cam-roller contact friction coefficient in order to keep the roller rolling. The importance of including stick-slip transitions into the mixed lubrication model for the cam-roller contact is amplified with decreasing cam rotational velocity.

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On a Model for the Prediction of the Friction Coefficient in Mixed Lubrication Based on a Load-Sharing Concept with Measured Surface Roughness

Cited by 36 publications

References 34 publications

Hydraulic Transport Through Calcite Bearing Faults With Customized Roughness: Effects of Normal and Shear Loading

Hydraulic Transport Through Calcite Bearing Faults With Customized Roughness: Effects of Normal and Shear Loading

Effect of topography parameter, load, and surface roughness on friction coefficient in mixed lubrication regime

The influence of stick–slip transitions in mixed-friction predictions of heavily loaded cam–roller contacts

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