Effects of lubricant rheology and impact speed on EHL film thickness at pure squeeze action

Fryza, Josef; Šperka, Petr; Kaneta, M.; Křupka, Ivan; Hartl, Martin

doi:10.1016/j.triboint.2016.10.023

Cited by 15 publications

(10 citation statements)

References 45 publications

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“…The predictions showed good agreement with the observations made by Safa and Gohar [52]. Wang et al [54] solved an impact EHL analysis under transient conditions for a range of different contact ellipticities, while Fryza et al [55] experimentally studied EHL contacts created under impact with a range of kinematics and different types of lubricants.…”

Section: Introductionsupporting

confidence: 78%

Transient Analysis of Isothermal Elastohydrodynamic Point Contacts under Complex Kinematics of Combined Rolling, Spinning and Normal Approach

2020

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This paper presents a brief review of elastohydrodynamic analysis in commemoration of the immense contributions of Duncan Dowson. This paper also presents an elastohydrodynamic analysis of the elliptical point contact problem under steady state as well as transient conditions. The overall methodology is validated against numerical predictions and experimental observations of acknowledged historical sources. The validated methodology is used to make original contributions in the elastohydrodynamics of elliptical point contact subjected to complex combined contact kinematics, including rolling/sliding, mutual convergence and separation (squeeze film motion) of contacting pairs, when subjected to reciprocating and spinning motions. This combined complex contact kinematics under transient conditions has not hitherto been reported in the literature. This paper shows the critical role of squeeze film motion upon lubricant film thickness. The results also show that the influence of spin motion is only significant at fairly high values of angular velocity and in the absence of a rolling/sliding motion.

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Section: Introductionsupporting

confidence: 78%

Transient Analysis of Isothermal Elastohydrodynamic Point Contacts under Complex Kinematics of Combined Rolling, Spinning and Normal Approach

2020

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“…Although it has also been proposed that the liquid might undergo a glass transition during the initial impact ( 15 – 17 ), experimental evidence for this glass transition is very scarce. Our measurements show that the extremely slow squeezing out of the thin lubricant film from the contact under pressure ( 6 ) and the transition between different lubrication regimes ( 12 ) have the same origin, which is the viscosity increase of the liquid up to the point of the glass transition, with a viscosity increase of many orders of magnitude.…”

Section: Introductionmentioning

confidence: 81%

“…The implicit dependence of film thickness on the properties of the system comes from hydrodynamics and is only understood for smooth surfaces in the EHL regime ( 6 ). In practice, surfaces are not ideally smooth, and lubrication will only be effective if the lubrication film thickness is comparable to or larger than the roughness of the sliding surfaces.…”

Section: Introductionmentioning

confidence: 99%

Fluorescence microscopy visualization of the roughness-induced transition between lubrication regimes

et al. 2019

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We investigate the transition between different regimes of lubrication and directly observe the thickness of nanometric lubrication films with a sensitivity of a single molecular layer at a multi-asperity interface through fluorescence microscopy. We redefine specific film thickness as the ratio of the lubricant film thickness and the surface roughness measured only at those regions of the interface where the gap is “minimal.” This novel definition of specific film thickness successfully captures the transition from full elastohydrodynamic lubrication to mixed and boundary lubrication. The transition can be triggered by increasing the surface roughness and is accurately predicted by using the new film thickness definition. We find that when the liquid carries part of the load, its apparent viscosity is greatly increased by confinement, and show how the transition between different lubrication regimes is well described by the viscosity increase and subsequent glass transition in the film.

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“…Roshan et al [81] studied the impact of lubricant ingredients and properties on the formation of boundary lubrication conditions. Fryza et al [82] investigated the squeeze film action when EHL was subjected to an impact loading or abrupt change of motion experimentally; they found that entrapped film shape was mainly determined by the loading speed and the thickness of the central film by the approaching speed and viscosity.…”

Section: Fluids Types and Other Factorsmentioning

confidence: 99%

State of the art of friction modelling at interfaces subjected to elastohydrodynamic lubrication (EHL)

Mueller

Zhang

2020

Friction

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Elastohydrodynamic lubrication (EHL) is a type of fluid-film lubrication where hydrodynamic behaviors at contact surfaces are affected by both elastic deformation of surfaces and lubricant viscosity. Modelling of contact interfaces under EHL is challenging due to high nonlinearity, complexity, and the multi-disciplinary nature. This paper aims to understand the state of the art of computational modelling of EHL by (1) examining the literature on modeling of contact surfaces under boundary and mixed lubricated conditions, (2) emphasizing the methods on the friction prediction occurring to contact surfaces, and (3) exploring the feasibility of using commercially available software tools (especially, Simulia/Abaqus) to predict the friction and wear at contact surfaces of objects with relative reciprocating motions.

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Effects of lubricant rheology and impact speed on EHL film thickness at pure squeeze action

Cited by 15 publications

References 45 publications

Transient Analysis of Isothermal Elastohydrodynamic Point Contacts under Complex Kinematics of Combined Rolling, Spinning and Normal Approach

Transient Analysis of Isothermal Elastohydrodynamic Point Contacts under Complex Kinematics of Combined Rolling, Spinning and Normal Approach

Fluorescence microscopy visualization of the roughness-induced transition between lubrication regimes

State of the art of friction modelling at interfaces subjected to elastohydrodynamic lubrication (EHL)

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