Elasto-Hydrodynamic Theory

Dowson, D.; Higginson, G. R.

doi:10.1016/b978-0-08-021302-6.50012-6

Cited by 249 publications

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“…Typical solution curves of pressure and gap thickness for both positive-and negativegap regimes are displayed in figures 9 and 10. These are well-known results in elastohydrodynamic lubrication (Dowson & Higginson 1966); they illustrate that the effect of the compliant layer is to change the gap width near X =0fromparabolic to locally linear with the slope tending to zero as the gap becomes increasingly negative (or the load increases). The variation of flow rateλ and meniscus locationx m with …”

Section: Equilibrium Flow: Lubricated Contacts With An Incompressiblementioning

confidence: 99%

“…Elastohydrodynamic lubrication (EHL) has its origins in tribology with the work of Dowson & Higginson (1966). In 'soft EHL', where pressures are low and viscosity is assumed constant, Herrebrugh (1968), Hooke & O'Donoghue (1972) and Hall &S avage (1988b)i n vestigated contacts in which the deformable bodies can be regarded as a half-space.…”

Section: Compliant Layermentioning

confidence: 99%

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A model for deformable roll coating with negative gaps and incompressible compliant layers

et al. 2003

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A soft elastohydrodynamic lubrication model is formulated for deformable roll coating involving two contra-rotating rolls, one rigid and the other covered with a compliant layer. Included is a finite-strip model (FSM) for the deformation of the layer and a lubrication model with suitable boundary conditions for the motion of the fluid. The scope of the analysis is restricted to Newtonian fluids, linear elasticity/viscoelasticity and equal roll speeds, with application to the industrially relevant highly loaded or ‘negative gap’ regime. Predictions are presented for coated film thickness, inter-roll thickness, meniscus location, pressure and layer deformation as the control parameters – load (gap), elasticity, layer thickness and capillary number, $\hbox{\it Ca}$ – are varied. There are four main results: Hookean spring models are shown to be unable to model effectively the deformation of a compliant layer when Poisson's ratio $\nu\rightarrow 0.5$. In particular, they fail to predict the swelling of the layer at the edge of the contact region which increases as $\nu\rightarrow 0.5$; they also fail to locate accurately the position of the meniscus, $X_M$, and to identify the presence, close to the meniscus, of a ‘nib’ (constriction in gap thickness) and associated magnification of the sub-ambient pressure loop.Scaling arguments suggest that layer thickness and elasticity may have similar effects on the field variables. It is shown that for positive gaps this is true, whereas for negative gaps they have similar effects on the pressure profile and flow rate yet quite different effects on layer swelling (deformation at the edge of the contact region) and different effects on $X_M$.For negative gaps and $\hbox{\it Ca}\,{\sim}\,O(1)$, the effect of varying either viscosity or speed and hence $\hbox{\it Ca}$ is to significantly alter both the coating thickness and $X_M$. This is contrary to the case of fixed-gap rigid roll coating.Comparison between theoretical predictions and experimental data shows quantitive agreement in the case of $X_M$ and qualitive agreement for flow rate. It is shown that this difference in the latter case may be due to viscoelastic effects in the compliant layer.

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Section: Equilibrium Flow: Lubricated Contacts With An Incompressiblementioning

confidence: 99%

Section: Compliant Layermentioning

confidence: 99%

A model for deformable roll coating with negative gaps and incompressible compliant layers

et al. 2003

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“…In most cases, both the density ρ and dynamic viscosity η decrease with with increasing temperature and increase with increasing pressure [32,33]. However, for the current study, the lubricant's behaviour is chosen independent of pressure since the contact under investigation experiences low loads, which lead to hydrodynamic pressures whose scale is sufficiently small to allow the neglect of the pressure effect.…”

Section: Governing Equationsmentioning

confidence: 99%

“…Besides the dependency on temperature and pressure, lubricants are also dependent on the shear-rate [33,[35][36][37]. This especially holds for conventional multi-grade oils.…”

Section: Governing Equationsmentioning

confidence: 99%

Evaluation of Wear Phenomena of Journal Bearings by Close to Component Testing and Application of a Numerical Wear Assessment

et al. 2018

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Hydrodynamic journal bearings are subjected to progressively rough loading conditions leading to an increased share of operation in mixed and boundary lubrication. This results in increased frictional losses, additional wear and a higher chance of failure, which calls for the understanding of wear processes and the necessity of a numerical assessment. We conducted wear investigations of journal bearings by making use of a close-to-component test setting, and the progress of wear could be linked to the introduced frictional energy and in combination with a comprehensive surface analysis tribological effects could be resolved in detail. Achieved wear coefficients were implemented in a novelly developed numerical framework, which allows for the dynamic numerical evaluation of operation in the fluid and mixed lubrication regime and simultaneously occurring wear processes. By comparing numerical and experimental results, we evaluated the numerical framework's capability to conduct holistic simulations including aspects like dynamically changing operation conditions, fluid and mixed lubrication as well as wear.

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“…Dowson and Higginson [10] completed the range of lubrication mechanisms by demonstrating that under extreme loading between contacts, such as in a rolling element bearing between the roller or ball and its cage, the very high pressures generated within the contact caused a plastic deformation of the contact materials together with a pressure-induced enhanced viscosity of the lubricant. This is elastohydrodynamic lubrication, or EHL, which has been of immense value in understanding and predicting the behaviour of thin films in highly loaded contacts.…”

Section: Prefacementioning

confidence: 99%

Chemistry and Technology of Lubricants

2010

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this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work.Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) PrefaceThe third edition of this book reflects how the chemistry and technology of lubricants have developed since the first edition was published in 1992. Refinery processes have become more precise in defining the physical and chemical properties of higher quality mineral base oils, Part I, Chapters 1 and 2, beneficial with the move away from Gp.I mineral base oils towards Gps.II and III, synthetic base oils such as poly-α-olefins (PAOs), the esters and others. New and existing additives have improved performance through enhanced understanding of their action, Part II, Chapters 3-7. Applications have become more rigorous, Part III, Chapters 8-14. The performance, specification and testing of lubricants has become more focused on higher level requirements, Part IV, Chapters 15-17. The acceleration of performance development in the past 35 years has been as significant as in the previous century. The performance and life between service changes of lubricants have extended dramatically and are expected to extend more, Chapters 9 and 10. Yet more performance will still be required but it will also include the lubricant's ability to 'stay in grade' for efficiency savings and withstand the conditions arising from the use of advanced environmental emission controls, such as for Euro 5 and 6 engines and their North American equivalents.The physical benefits of having a lubricant film between surfaces in relative motion have been known for several millennia. Dowson [1] found an Egyptian hieroglyph of a large stone block hauled by many slaves. Close inspection shows fluid, presumably water, being poured into the immediate path of the block. Moderately refined vegetable oils and fats were increasingly used to lubricate machines and carriage/wagon bearings; the benefits of reducing the force needed to operate them were a widely received wisdom up to the end of the middle ages, ∼1450 AD. Increasing industrialisation after 1600 AD, accelerated during the First Industrial Revolution in Britain after 1760 AD, soon followed by other developed countries, recognised the important contribution that lubricants made in reducing the work required to overcome friction and in extending the working life of machines. The crude technology existed and was effective for its time but it was not understood.Leonado da Vinci was the first person recorded to investigate the resistance to motion of two 'smooth' loaded bodies in contact. He set out the Laws of Friction as we now essentially know them [2] but they were not appreciated and nor applied at the ti...

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Elasto-Hydrodynamic Theory

Cited by 249 publications

References 0 publications

A model for deformable roll coating with negative gaps and incompressible compliant layers

A model for deformable roll coating with negative gaps and incompressible compliant layers

Evaluation of Wear Phenomena of Journal Bearings by Close to Component Testing and Application of a Numerical Wear Assessment

Chemistry and Technology of Lubricants

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