Central and Minimum Elastohydrodynamic Film Thickness at High Contact Pressure

1997 ◽  
Vol 119 (2) ◽  
pp. 291-296 ◽  
Author(s):  
M. Smeeth ◽  
H. A. Spikes
Keyword(s):  
High Pressure ◽  
Film Thickness ◽  
Contact Pressure ◽  
Applied Load ◽  
Optical Technique ◽  
Test Rig ◽  
Minimum Film Thickness ◽  
Elastohydrodynamic Film Thickness ◽  
Contact Pressures ◽  
High Contact Pressure

A new optical technique has been developed which is able to obtain accurate film thickness profiles across elastohydrodynamic (EHD) contacts. This has been used in conjunction with a high pressure EHD test rig to obtain both central and minimum EHD film thicknesses at high contact pressures up to 3.5 GPa. The results have been compared with the classical film thickness equations of Hamrock and Dowson and also with recent high pressure computations due to Venner. It is found that minimum film thickness falls more rapidly with applied load at high than at low contact pressures, with a film thickness/load exponent of −0.3. This confirms the findings of recent high pressure computational EHD modeling.

Influence of Contact Pressure on Central and Minimum Film Thickness Within Ultrathin Film Lubricated Contacts

2005 ◽  
Vol 127 (4) ◽  
pp. 890-892 ◽  
Author(s):  
I. Křupka ◽  
M. Hartl ◽  
M. Liška
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Nonlinear Behavior ◽  
Test Rig ◽  
Lubricated Contacts ◽  
Optical Test ◽  
Minimum Film Thickness ◽  
Lubricant Films ◽  
The Relationship ◽  
Contact Pressures

Recent numerical results have indicated that the relationship between the film thickness and the speed may not always follow the simple power law, especially under severe conditions. This paper is aimed at obtaining experimental results at high contact stresses and low speeds to study the thin film behavior. Ultrathin lubricant films were observed at maximum Hertz pressures of 0.52, 1.01, and 1.54 GPa by using an optical test rig. Central and minimum film thickness values were obtained with thin film colorimetric interferometry from chromatic interferograms. The nonlinear behavior of both central and minimum film thicknesses in log-log coordinates was observed as rolling speed and thereby film thickness decreased. This tendency became more obvious at higher contact pressures.

Use of a Micro-Contact Model to Optimize SI Engine’s 3-Piece Oil Ring Profiles Regarding Wear and Lubrication

2002 ◽  
Author(s):  
Eduardo Tomanik ◽  
Andre´ Ferrarese
Keyword(s):  
Film Thickness ◽  
Contact Pressure ◽  
Wear Behavior ◽  
Bench Test ◽  
Asperity Contact ◽  
Oil Consumption ◽  
Tangential Load ◽  
Oil Film ◽  
Operation Temperature ◽  
Contact Pressures

A computer model that addresses the wear behavior by calculating hydrodynamic and asperity contact pressures was used to optimize the running face of three-piece oil control rings. The model incorporates Reynolds equation to calculate the oil film thickness for two sliding surfaces under a given condition (profile and topography of the surfaces, load, speed, lubricant viscosity grade and operation temperature). Prediction of the resultant asperity contact pressures is made by Greenwood-Williamson model. More scraping ring rail profiles are better for oil control, but present more wear due to higher asperity contact pressures. This higher wear can lead to less scraping profile, increasing ring end gap and lower ring tangential load, which deteriorates long term oil consumption control, hence engine durability. In the present work, a relatively simple computer program was used to predict lube oil film thickness and wear for different rail running profiles. Ring wear was assumed to be proportional to the calculated asperity contact pressure. Different rail profiles where the running profiles had a flat portion varying from less than 0.10 mm to higher than 0.20 mm were simulated and then tested in a bench test consisting in an electrical motored engine. Except for the combustion absence, all other engine characteristics were preserved (e.g., stroke, piston-ring pack, lubrication system) in the bench test. The measured oil control ring wear correlated very well with the predicted one. The model allowed the numerical optimization of the running profile of ring rail, which has lower asperity contact pressure, hence wear, but still has a good scraping capability. Two actual ICE tests were also realized. The predicted lower wear of the optimized profile was experimentally confirmed and no differences on LOC were found.

Elastohydrodynamie Lubrication of Big-End Bearings Part 2: Ratification

1991 ◽  
Vol 205 (2) ◽  
pp. 107-119 ◽  
Author(s):  
M B Aitken ◽  
H McCallion
Keyword(s):  
Film Thickness ◽  
Close Correlation ◽  
Connecting Rod ◽  
Test Rig ◽  
Collapse Mechanisms ◽  
Minimum Film Thickness ◽  
Inertial Loading ◽  
Film Collapse ◽  
Thickness Measurements

The elastohydrodynamic analysis developed in Part 1 of this work is ratified against previous Ruston and Hornsby big-end studies. Sufficiently close correlation with published in situ film-thickness measurements allows big-end bearing performance to be determined with some confidence; significant new insight was obtained. Elasticity body forces from connecting-rod motion were found to be an integral component of the big-end representation; it is a prevalent misconception that these forces can be neglected from theoretical as well as experimental test-rig works. Film collapse mechanisms, likened to vapour cavitation, were observed in the dynamically loaded elastic bearing; these were not detected in equivalent rigid bearing simulations. Cyclic minimum film thickness was observed during inertial loading, irrespective of gas force loading. Two separate minimum-film conditions were identified: one in the connecting-rod's neck and a second, at higher load, in the rod's cap. The second condition is critical from a design standpoint; significantly thinner films are predicted than by rigid bearing theory.

Analysis of elastohydrodynamic lubrication in a novel metal-on-metal hip joint replacement

2002 ◽  
Vol 216 (3) ◽  
pp. 185-193 ◽  
Author(s):  
M Jagatia ◽  
Z M Jin
Keyword(s):  
Finite Element ◽  
Film Thickness ◽  
Pressure Distribution ◽  
Contact Pressure ◽  
Elastohydrodynamic Lubrication ◽  
Metal On Metal ◽  
Minimum Film Thickness ◽  
Acetabular Components ◽  
Cobalt Chrome Alloy ◽  
Cobalt Chrome

Elastohydrodynamic lubrication (EHL) analysis was carried out in this study for a novel metal-on-metal hip prosthesis, which consists of a cobalt-chrome alloy femoral head articulating against a cobalt-chrome alloy acetabular insert connected to a titanium fixation shell through a taper. Finite element models were developed to investigate the effect of the pelvic bone and the load on the predicted contact pressure distribution between the two bearing surfaces under dry conditions. The finite element method was used to develop elasticity models for both the femoral and the acetabular components; it was found that the elastic deformation of the acetabular insert was mainly dependent on the load, rather than the detailed pressure distribution. A modified solution methodology was accordingly developed to couple the elasticity models for both the femoral and the acetabular surfaces with the Reynolds equation and to solve these numerically by the finite difference method. It was found that a load increase from 500 to 2500 N had a negligible effect on the predicted maximum contact pressure and the minimum film thickness, due to the relatively flexible and accommodating structure of the acetabular insert. Furthermore, the predicted minimum film thickness was shown to be significantly greater than the simple estimation based on the assumption of semi-infinite solids (mono-block design) using the Hamrock and Dowson formula. The effects of the viscosity of the lubricant and the radial clearance between the femoral and the acetabular components on the predicted lubricating film thickness were investigated under both in vitro simulator testing and in vivo walking conditions.

scholarly journals Assessment of Contact Pressures between a Mandibular Overdenture and the Prosthodontic Area

2021 ◽  
Vol 11 (10) ◽  
pp. 4339
Author(s):  
Małgorzata Idzior-Haufa ◽  
Agnieszka A. Pilarska ◽  
Tomasz Gajewski ◽  
Krzysztof Szajek ◽  
Łukasz Faściszewski ◽  
...  
Keyword(s):  
Contact Pressure ◽  
Applied Load ◽  
Critical Case ◽  
Matrix Stiffness ◽  
3D Scanner ◽  
Edentulous Mandible ◽  
Polypropylene Matrix ◽  
Mandibular Overdenture ◽  
Maximum Contact ◽  
Contact Pressures

In this paper, we assess the pressure between the overdenture located in the mandible and supported by a bar retained on two implants and the prosthodontic area. For testing, a model of an edentulous mandible was created using a mold by FRASACO with two implants and a “rider” bar inserted. A complete mandibular denture with polypropylene matrices was made. Three types of matrices of various stiffness were applied. The mandible and overdenture geometry was mapped using a digital image obtained with a Steinbichler Comet L3D 3D scanner. Finite element method calculations were performed in the Abaqus FEA software. The results demonstrate that the maximum contact pressure is observed when the loads are associated with canines. A critical case for the lower posterior is chewing performed by the molars. The pressure zone is the largest for POM-1 with Young’s modulus of 1.5 GPa and is reduced by 5.0% and 7.8% for POM-2 (E = 2.5 GPa) and POM-3 (E = 3.5 GPa), respectively. The stress distribution under the prosthesis mostly depends on the region loaded onto it. The applied load produces a slight contact pressure between the denture and the prosthodontic area in the anterior zone. A change in polypropylene matrix stiffness does not affect contact pressures.

scholarly journals A New Compression-Torsion-Tribometer with Scalable Contact Pressure for Characterization of Tool Wear during Plastic Deformation

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Marco Teller ◽  
Simon Seuren ◽  
Markus Bambach ◽  
Gerhard Hirt
Keyword(s):  
Yield Stress ◽  
Contact Pressure ◽  
Friction And Wear ◽  
Wear Behaviour ◽  
Cold Extrusion ◽  
Workpiece Material ◽  
Contact Pressures ◽  
High Contact Pressure ◽  
Multiple Load

A contact pressure which reaches up to ten times the yield stress of the workpiece material is characteristic for cold extrusion processes. Common tests for friction and wear are limited to rather low contact pressures. Thus, the aim of this paper is to present a new compression-torsion-tribometer which is able to scale the contact pressure to a multiple of the yield stress of the workpiece. In order to enable a contact pressure that greatly exceeds the yield stress of the workpiece material, the workpiece specimen is encapsulated laterally. As main parameters, contact pressure, glide length, and relative velocity can be adjusted independently, thus allowing for multiple load cycles. The resulting torque is measured continuously as an indicator for wear. Afterwards wear can be also quantified by examination of surfaces. Hence, the developed setup enables a comparison of tool surfaces and coatings and a characterization of wear behaviour under high contact pressure.

Occurrence of a Noncentral Dimple in Squeezing EHL Contacts

2006 ◽  
Vol 128 (3) ◽  
pp. 632-640 ◽  
Author(s):  
F. Guo ◽  
M. Kaneta ◽  
J. Wang ◽  
H. Nishikawa ◽  
P. Yang
Keyword(s):  
Film Thickness ◽  
Impact Velocity ◽  
Central Region ◽  
Applied Load ◽  
Elastohydrodynamic Lubrication ◽  
The Other ◽  
Second Step ◽  
Minimum Film Thickness ◽  
Squeeze Effect ◽  
Film Profile

Previous studies about pure squeeze elastohydrodynamic lubrication (EHL) have disclosed a film profile with a central dimple. Two problems about pure squeeze EHL are numerically solved in this paper. One is for a very small initial impact gap, and the other is the response of a squeezed EHL conjunction under stepwise loads. None of them result in the familiar film with a central dimple, which can be attributed to the local squeeze effect generated in the periphery region. In the first problem, it has been found that when there is adequate oil present on the plate, with a decrease in the initial impact gap, a shallow circumferential dimple occurs at the periphery of the conjunction instead of the primary central dimple presented in previous studies. Correspondingly the minimum film thickness occurs at the central region. The effect of the initial impact velocity on the periphery dimple is also investigated. In the second problem, the response of a conjunction subjected to a prescribed stepwise load is studied. When the first step load is applied, a central dimple film is produced. When the applied load is increased with a second step load, a periphery dimple appears, similar to that in the first problem. The local squeeze effect for the present numerical periphery dimple has been observed in previous experiments under similar conditions.

Elastohydrodynamic Lubrication of Soft, Highly Deformed Contacts

1972 ◽  
Vol 14 (1) ◽  
pp. 34-48 ◽  
Author(s):  
C. J. Hooke ◽  
J. P. O'Donoghue
Keyword(s):  
Film Thickness ◽  
Contact Pressure ◽  
Journal Bearing ◽  
Elastohydrodynamic Lubrication ◽  
Theoretical Solution ◽  
Minimum Film Thickness ◽  
Ring Seal ◽  
The Relationship ◽  
Maximum Contact

Part 1 presents a theoretical solution to the problem of lubrication of soft, highly deformed surfaces. It is argued that with this type of contact the inlet and outlet regions can be separated and analysed independently. This approach leads to a single value of non-dimensional film thickness at the point of maximum contact pressure and to a non-dimensional minimum film thickness dependent on the relationship between the inlet and outlet parameters. In Part 2, these results are applied to the problems of a cylinder sliding on an elastomer lined surface, an elastomer lined journal bearing and a sliding O-ring seal.

Numerical and Experimental Research of the Slurry Film in Chemical Mechanical Polishing (CMP)

2010 ◽  
Vol 102-104 ◽  
pp. 669-674
Author(s):  
Fei Yan Lou ◽  
Qian Fa Deng ◽  
Ju Long Yuan
Keyword(s):  
Film Thickness ◽  
Chemical Mechanical Polishing ◽  
Applied Load ◽  
Reynolds Equation ◽  
Rotation Speed ◽  
Hydrodynamic Lubrication ◽  
Three Dimensional ◽  
Mechanical Polishing ◽  
Film Pressure ◽  
Minimum Film Thickness

A three-dimensional hydrodynamic lubrication model for chemical-mechanical polishing is presented based on the Reynolds equation and Reynolds boundary condition. By solving the Reynolds equation, the slurry film pressure distribution has been obtained. The effects of minimum film thickness and the wafer tile angle on the film pressure are analyzed, and the influence of the polishing applied load and rotation speed on slurry film thickness and tilt angle are discussed. At last, by experiment, it is found that the simulation results are similar to experiment results which film thickness is increasing with the increasing of rotation speed, decreasing of the applied load. It is proved that the simulation is reliable.

scholarly journals Misalignment-Induced Micro-Elastohydrodynamic Lubrication in Rotary Lip Seals

Lubricants ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 19 ◽  
Author(s):  
F. Xavier Borras ◽  
Matthijn B. de Rooij ◽  
Dik J. Schipper
Keyword(s):  
Film Thickness ◽  
Contact Pressure ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Thickness Variation ◽  
Hydrodynamic Action ◽  
Static Contact ◽  
Model Predictions ◽  
Minimum Film Thickness ◽  
Lip Seals

In literature the lubrication of rotary lip seals is explained by hydrodynamic action on a microscopic scale. This theory assumes perfect concentricity between the seal and the shaft which in reality seldomly occurs. Focusing on the stern tube seals application, an analysis is performed on the phenomena distorting the axisymmetric operation of rotary lip seals. Radial and angular shaft misalignments together with pressure and temperature gradients have been modelled. The model predictions are validated using a dedicated setup. Additionally, applying the soft-EHL film thickness expressions at the asperity level, an equivalent film thickness along the circumferential direction is estimated. The Reynolds PDE is solved to predict the misalignment-induced hydrodynamic pressure build-up. The film thickness variation derived and accompanying non-uniform contact pressure distribution was shown to be sufficient for hydrodynamic action and, depending on the minimum film thickness, the hydrodynamic pressure build-up can exceed the static contact pressure. Additionally, significant differences were observed between the radial and angular misalignment configurations.

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