scholarly journals Fast Approach for Calculating Film Thicknesses and Pressures in Elastohydrodynamically Lubricated Contacts at High Loads

1986 ◽  
Vol 108 (3) ◽  
pp. 411-419 ◽  
Author(s):  
L. G. Houpert ◽  
B. J. Hamrock
Keyword(s):  
High Pressure ◽  
Film Thickness ◽  
Line Contact ◽  
Elastic Deformations ◽  
New Approach ◽  
Lubricated Contacts ◽  
Fast Approach ◽  
Pressure Spike

The film thicknesses and pressures in elastohydrodynamically lubricated contacts have been calculated for a line contact by using an improved version of Okamura’s approach. The new approach allows for lubricant compressibility, the use of Roelands viscosity, a general mesh (nonconstant step), and accurate calculations of the elastic deformations. The new approach is described, and the effects on film thickness, pressure, and pressure spike of each of the improvements are discussed. Successful runs have been obtained at high pressure (to 4.8 GPa) with low CPU times.

scholarly journals Effect of an Improved Yasutomi Pressure-Viscosity Relationship on the Elastohydrodynamic Line Contact Problem

2013 ◽  
Vol 2013 ◽  
pp. 1-7
Author(s):  
Vincenzo Petrone ◽  
Adolfo Senatore ◽  
Vincenzo D'Agostino
Keyword(s):  
High Pressure ◽  
Film Thickness ◽  
Free Volume ◽  
Experimental Studies ◽  
Line Contact ◽  
Volume Model ◽  
Free Volume Model ◽  
Pressure Area ◽  
New Formulation ◽  
Lubricant Viscosity

This paper presents the application of an improved Yasutomi correlation for lubricant viscosity at high pressure in a Newtonian elastohydrodynamic line contact simulation. According to recent experimental studies using high pressure viscometers, the Yasutomi pressure-viscosity relationship derived from the free-volume model closely represents the real lubricant piezoviscous behavior for the high pressure typically encountered in elastohydrodynamic applications. However, the original Yasutomi correlation suffers from the appearance of a zero in the function describing the pressure dependence of the relative free volume thermal expansivity. In order to overcome this drawback, a new formulation of the Yasutomi relation was recently developed by Bair et al. This new function removes these concerns and provides improved precision without the need for an equation of state. Numerical simulations have been performed using the improved Yasutomi model to predict the lubricant pressure-viscosity, the pressure distribution, and the film thickness behavior in a Newtonian EHL simulation of a squalane-lubricated line contact. This work also shows that this model yields a higher viscosity at the low-pressure area, which results in a larger central film thickness compared with the previous piezoviscous relations.

Occurrence of High Pressure Spike in Unidirectional Start–Stop–Start Point Contacts

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
P. Sperka ◽  
J. Wang ◽  
I. Krupka ◽  
M. Hartl ◽  
M. Kaneta
Keyword(s):  
High Pressure ◽  
Film Thickness ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Contact ◽  
Point Contacts ◽  
Pressure Distributions ◽  
Machine Element ◽  
Pressure Spike

The transient film thickness and pressure distributions in point elastohydrodynamic lubrication (EHL) contacts during start–stop–start motion are discussed based on experimental and numerical analyses. When the machine element starts to move after the stopping, where the oil is entrapped between two surfaces, the pressure at the exit area increases very much. The pressure increase depends markedly on the overall film thickness before the stopping of the motion, but is hardly controlled by the acceleration after the stopping. It can be considered that this phenomenon affects the rolling contact fatigue damage.

The line contact problem of elastohydrodynamic lubrication - I. Asymptotic structure for low speeds

1989 ◽  
Vol 424 (1867) ◽  
pp. 393-407 ◽  
Keyword(s):  
Asymptotic Solution ◽  
Contact Problem ◽  
Film Thickness ◽  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Thin Layers ◽  
Line Contact ◽  
Asymptotic Regime ◽  
Lubricating Film ◽  
Pressure Spike

This paper reports the first formal asymptotic solution to the line contact problem of elastohydrodynamic lubrication (EHL), a fundamental problem describing the elastic deformation of lubricated rolling elements such as roller bearings, gear teeth and other contacts of similar geometry. The asymptotic régime considered is that of small λ , a dimensionless parameter proportional to rolling speed, viscosity and the elastic modulus. The solution is shown to possess four regions: a zone where the lubricating film is both thin and slowly narrowing and which is closely related to the contact area that occurs in the absence of lubricant, an upstream inlet zone of low pressure, and two thin layers on either side of the contact zone. The solutions in the first two just-mentioned zones are given by simple analytical expressions. The solutions in the two thin layers are obtained from two universal functions obtained by Bissett & Spence ( Proc. R. Soc. Lond . A 424, 409 (1989)). Although these two functions, related to the local film thickness, are obtained by numerical techniques by Bissett & Spence, it should be emphasized that all cases in the asymptotic régime considered are hereby solved definitively without recourse to further computation. Although some features of this structure have been suggested by other solution approaches, generally, these are numerical or ad hoc approximations. See the texts by Johnson ( Contact Mechanics , pp. 328 (1985)) and Dowson & Higginson ( Elasto-hydrodynamic lubrication (1977)), this work provides a formal mathematical basis for understanding most of the principal features of EHL. The solution provides a simple formula for minimum film thickness and displays the sharp narrowing of the lubricating film in the thin layer near the exit. In the basic asymptotic solution provided here, the dimensionless pressure-viscosity coefficient, α , is assumed to be O (1), and in this parameter régime, no pressure spike will occur. By comparing with the work of Hooke ( J. mech. Engng Sci . 19(4), 149 (1977)), we can show that an incipient pressure spike occurs when α becomes as large as O ( λ -1/5 ). However, asymptotic solutions in this latter parameter régime require new numerical solutions for each case of interest and are not pursued here.

The transition region of elastohydrodynamic lubrication

1991 ◽  
Vol 432 (1886) ◽  
pp. 467-479 ◽  
Keyword(s):  
Film Thickness ◽  
Transition Region ◽  
Parameter Space ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Series Method ◽  
Chebyshev Series ◽  
Pressure Spike ◽  
Constant Coefficients ◽  
Dimensional Parameters

A semi-analytic approach is presented for the elastohydrodynamic lubrication problem of two cylinders in line contact. The model takes account of the effects of elastic deformation and piezo-viscosity in the transition region (the area of parameter space where the pressure spike emerges and develops). Following Poritsky, pressure and displacement are expressed as Chebyshev series and Fejér’s method is used to deal with the sharp crease in the film shape that is a feature of piezoviscous contacts. It is shown that the film thickness depends solely upon two non-dimensional parameters and can be accurately represented by an equation of the form: H = a 0 g 3 a 1 g 1 + a 2 g 3 a 3 , where the a i = 0, 1, 2, 3) are constant coefficients. Important features of this Chebyshev series method include accurate representations for the emerging pressure spike and the associated sharp crease in the film shape together with film thickness predictions which smoothly link those areas of parameter space on either side of the transition region.

Elastoplastohydrodynamic Lubrication with Dent Effects

1996 ◽  
Vol 210 (4) ◽  
pp. 233-245 ◽  
Author(s):  
G Xu ◽  
D A Nickel ◽  
F Sadeghi ◽  
X Ai
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Sliding Contacts ◽  
Element Analysis ◽  
Elastic Case ◽  
Local Material

A line contact elastoplastohydrodynamic lubrication (EPHL) model has been developed to investigate the effect of a dent on heavily loaded rolling/sliding contacts. The Jinite element analysis (FEA) was used to obtain the plastic deformation of the surfaces caused by the high-pressure spikes that occur in the contact due to the presence of a dent. The effects of various dent sizes on the pressure and film thickness were studied. The results indicate that by including the plastic deformation of the surfaces in the analysis, the pressure spikes that occur due to a dent in the contact are smaller than those of the purely elastic case, and local material yielding occurs, resulting in bumps at the edges of the dent. Effects of diflerent bump shapes at the dent edges were then studied in elastohydrodynamic lubrication (EHL) contacts and the results indicated that these bumps can reduce the magnitude of pressure spikes.

Numerical Analysis of Elastohydrodynamic Lubrication with Non-Newtonian Lubricant

2013 ◽  
Vol 388 ◽  
pp. 3-7
Author(s):  
Dedi Rosa Putra Cupu ◽  
Adli Bahari ◽  
Kahar Osman ◽  
Jamaluddin Md Sheriff
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Fluid Model ◽  
Contact Region ◽  
Roller Bearing ◽  
Elastohydrodynamic Lubrication ◽  
Physical Interaction ◽  
Infinite Length ◽  
Line Contact ◽  
Lubricated Contacts

Elastohydrodynamic lubrication is a form of hydrodynamic lubrication involving physical interaction between two contacting surfaces and liquid where elastic deformation of the contacting surfaces due to heavily loading applied will affect the elastohydrodynamic pressure and fluid film thickness significantly. In this paper, a line contact EHL is modeled through the cylinder contact to a flat surface to represent the application of roller bearing. This solution is limited to two dimensional line contact problem only, an infinite length of cylinder was used as physical modeling. The behavior of non-Newtonian fluid also was investigated using power law fluid model. Bearing speed is to be assumed in steady state and temperature is assumed constant. The bearing performance parameters such as pressure and film thickness of lubricated contacts are calculated using Newton-Raphson method.The results show that the peak pressure increases as the parameters such as velocity, load and material parameter were increases and the spike was found to shift to the center of roller. The film was almost flat at contact region and formed a dimple shape near the outlet flow. The value of pressure spike and minimum film thickness were smaller at lower speed and were increased during raising speed then the peak point was found to be shifted to center of roller.

Pressure Spikes in Elastohydrodynamically Lubricated Conjunctions

1988 ◽  
Vol 110 (2) ◽  
pp. 279-284 ◽  
Author(s):  
B. J. Hamrock ◽  
Ping Pan ◽  
Rong-Tsong Lee
Keyword(s):  
Film Thickness ◽  
Pressure Gradient ◽  
Line Contact ◽  
Wide Range ◽  
Pressure Spike ◽  
Basic Parameters

The film thickness, pressure, and flow in elastohydrodynamically lubricated conjunctions were calculated for a line contact. The main focus of the study was to get a better understanding of why a pressure spike exists in elastohydrodynamically lubricated conjunctions. Various combinations of viscous or isoviscous and compressible or incompressible situations were studied for a wide range of loads. The basic parameters were pressure, pressure gradient, film shape, and flow. It was found that the major factor causing the pressure spike to occur was the viscosity.

scholarly journals Thermoelastohydrodynamics of grease-lubricated concentrated point contacts

2009 ◽  
Vol 224 (3) ◽  
pp. 683-695 ◽  
Author(s):  
B K Karthikeyan ◽  
M Teodorescu ◽  
H Rahnejat ◽  
S J Rothberg
Keyword(s):  
Film Thickness ◽  
High Pressures ◽  
Plug Flow ◽  
Elastohydrodynamic Lubrication ◽  
Solid Surfaces ◽  
Point Contacts ◽  
Base Oil ◽  
Oil Film ◽  
Lubricated Contacts ◽  
Pressure Spike

Isothermal and thermoelastohydrodynamic lubrication (TEHL) analyses of grease lubricated bearings are presented. A grease plug flow is formed in the conjunction that, with no shear at the boundaries with the solid surfaces, adheres to them in the region of high pressures under isothermal conditions. The elastohydrodynamic lubrication grease pressure distribution conforms fairly closely to that of its base oil alone, with the exception of inlet trail and pressure spike regions. The dependency of film thickness on speed (rolling viscosity) and load parameters for the base oil agrees with previously reported findings of the research community. For grease there are subtle differences with the base oil film thickness load and speed dependencies. However, it is clear that extrapolated oil film thickness formulae for oils can be used reasonably for the prediction of grease films, at least as a first approximation. The results presented agree well with optical interferometric measurements reported in the literature for grease-lubricated contacts at low temperatures and low surface velocities. TEHL analysis shows breakdown of the plug flow and significant reduction in film thickness, which can lead to changes in the regime of lubrication to mixed or boundary conditions.

scholarly journals Optical Analysis of Ball Bearing Starvation

1971 ◽  
Vol 93 (3) ◽  
pp. 349-361 ◽  
Author(s):  
L. D. Wedeven ◽  
D. Evans ◽  
A. Cameron
Keyword(s):  
Film Thickness ◽  
Ball Bearing ◽  
Point Contact ◽  
Experimental Measurements ◽  
Line Contact ◽  
Optical Analysis ◽  
Grease Lubrication ◽  
Theoretical Predictions ◽  
Pressure Stress ◽  
Starvation Conditions

Elastohydrodynamic oil film measurements for rolling point contact under starvation conditions are obtained using optical interferometry. The experimental measurements present a reasonably clear picture of the starvation phenomenon and are shown to agree with theoretical predictions. Starvation inhibits the generation of pressure and, therefore, reduces film thickness. It also causes the overall pressure, stress, and elastic deformation to become more Hertzian. Additional experiments using interferometry illustrate: the cavitation pattern, lubricant entrapment, grease lubrication, ball spin, and edge effects in line contact.

Simple Formulas for Performance Parameters Used in Elastohydrodynamically Lubricated Line Contacts

1989 ◽  
Vol 111 (2) ◽  
pp. 246-251 ◽  
Author(s):  
Ping Pan ◽  
B. J. Hamrock
Keyword(s):  
Film Thickness ◽  
Curve Fitting ◽  
Center Of Pressure ◽  
Operating Parameters ◽  
Performance Parameters ◽  
Practical Applications ◽  
Line Contacts ◽  
Pressure Spike

The film thickness and pressure in elastohydrodynamically lubricated conjunctions have been evaluated numerically for a rather complete range of operating parameters (dimensionless load, speed, and materials parameters) normally experienced in practical applications. From the film thickness and pressure throughout the conjunction a number of performance parameters were evaluated. By curve fitting the data, formulas were obtained that allow easy evaluation of the amplitude and location of the pressure spike, the minimum and central film thicknesses, the value of ρeHe, and the center of pressure.

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