A fast thermoelastic model based on the half-space theory applied to elastohydrodynamic lubrication of line contacts involving free boundaries

2021 ◽  
pp. 1-29
Author(s):  
Ali Yalpanian ◽  
Raynald Guilbault
Keyword(s):  
Finite Dimension ◽  
Elastohydrodynamic Lubrication ◽  
Contact Problems ◽  
Pressure Profile ◽  
Distribution Center ◽  
Maximum Pressure ◽  
Free Boundaries ◽  
Heat Flows ◽  
Line Contacts ◽  
Contact Models

Abstract This study allows contact models based on semi-analytical methods including the impacts of thermoelastic deformations in contacts of finite dimension bodies. The proposed method controls heat flows crossing free boundaries. A comparison with FEA reveals that the proposed method can reduce the calculation times by more than 98%. The paper introduces the thermoelasticity effects into thermal-elastohydrodynamic lubrication (TEHL) modeling of line contact problems. The analysis reveals that including thermoelastic deformations changes the pressure profile and tends to localize the pressure close to the distribution center. Compared to TEHL simulations, the examined configurations caused an overall increase in the maximum pressure by about 9%, an overall film thickness reduction of about 7%, and an overall temperature increase of about 2 K.

Squeeze and Entraining Motion in Nonconformal Line Contacts. Part II—Elastohydrodynamic Lubrication

1989 ◽  
Vol 111 (1) ◽  
pp. 8-16 ◽  
Author(s):  
Rong-Tsong Lee ◽  
B. J. Hamrock
Keyword(s):  
Transient Process ◽  
Peak Pressure ◽  
Initial Conditions ◽  
Hydrodynamic Lubrication ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Profile ◽  
Maximum Pressure ◽  
Steady State Condition ◽  
Maximum Peak ◽  
Line Contacts

A fast numerical approach to the solution of elastohydrodynamic lubrication (EHL) of line contacts in combined entraining and normal squeeze motion is developed. The initial conditions for the pressure profile, the central normal squeeze velocity, and the location of the outlet boundary at any specified dimensionless load and dimensionless entraining velocity were obtained from the hydrodynamic lubrication study in Lee and Hamrock (1988). The pressure and film thickness were obtained by solving the transient Reynolds, elasticity, rheology, and time-dependent central squeeze velocity equations. The squeeze effect on this transient EHL problem has been proved in that the maximum peak pressure was always higher than the maximum pressure calculated at the steady-state condition. The needle-shaped pressure profile during the transient process produced a dimpled shape near the center of the contacts. In general, the maximum peak pressure increased with increasing dimensionless load, decreasing dimensionless entraining velocity, and increasing dimensionless materials parameter. The dynamic performance parameters were plotted and are a function not only of the dimensionless velocity parameter (as described in Lee and Hamrock, (1988)), but also of the dimensionless load, the dimensionless entraining velocity, and the dimensionless materials parameter. The major factor causing the pressure gradient to be infinity during the transient process was the viscosity. A non-Newtonian fluid is suggested to execute the problem for high load and low entraining velocity.

Elastohydrodynamic Lubrication Analysis of Finite Line Contact Problem With Consideration of Two Free End Surfaces

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Haibo Zhang ◽  
Wenzhong Wang ◽  
Shengguang Zhang ◽  
Ziqiang Zhao
Keyword(s):  
Contact Problem ◽  
Finite Length ◽  
Elastohydrodynamic Lubrication ◽  
Line Contact ◽  
Free Boundaries ◽  
Finite Line Contact ◽  
Line Contacts ◽  
Speed Up ◽  
Finite Line ◽  
Overlapping Method

Elastohydrodynamic lubrication (EHL) analysis in finite line contacts is usually modeled by a finite-length roller contacting with a half-space, which ignores effect of the two free boundaries existing in many applications such as gears or roller bearings. This paper presents a semi-analytical method, involving the overlapping method and matrix formation, for EHL analysis in the finite line contact problem to consider the effect of two free end surfaces. Three half-spaces with mirrored loads to be solved are overlapped to cancel out the stresses at expected surfaces, and three matrices can be obtained and reused for the same finite-length space. The isothermal Reynolds equation is solved to obtain the pressure distribution and the fast Fourier transform (FFT) is used to speed up the elastic deformation and stress related calculation. Different line contact situations, including straight rollers, tapered rollers, and Lundberg profile rollers, are discussed to explore the effect of free end surfaces.

Thermal Non-Newtonian Elastohydrodynamic Lubrication of Rolling Line Contacts

1991 ◽  
Vol 113 (3) ◽  
pp. 481-491 ◽  
Author(s):  
H. Salehizadeh ◽  
N. Saka
Keyword(s):  
Film Thickness ◽  
Contact Region ◽  
Elastohydrodynamic Lubrication ◽  
Pressure Profile ◽  
Shear Stresses ◽  
Hertz Contact ◽  
Minimum Film Thickness ◽  
Line Contacts ◽  
Pressure Spike ◽  
Heavy Loads

The two-dimensional thermal elastohydrodynamic equations were numerically solved for a Ree-Eyring type lubricant under pure rolling conditions. Profiles of lubricant pressure, film thickness, and temperature were obtained for medium to heavy loads and moderate to high rolling speeds. The pressure results generally show a small secondary peak near the outlet, but at the highest load considered no pressure spike is obtained and the pressure profile is almost Hertzian. The film thickness results show an increase in minimum film thickness with increasing rolling speeds, but at a lesser rate than those predicted for a Newtonian fluid under isothermal conditions. It is found that unless the lubricant becomes non-Newtonian in the inlet region, the reduction in minimum film thickness at high rolling speeds is completely due to thermal effect. The lubricant temperature profile and the amount of heat generated and dissipated in the contact region were also calculated. The lubricant temperature reaches a maximum just before the entrance to the Hertz contact region. Both shear and compression heating are found to be important in raising the lubricant temperature in the inlet. As the lubricant enters the Hertz contact zone, the temperature first drops rapidly, because of the rapid heat conduction to the rollers, and then remains almost constant for most of the Hertz contact. Near the exit where the pressure gradients are large, the lubricant temperature drops rapidly below the ambient because of lubricant expansion. The lubricant then heats up rapidly before leaving the contact area as a result of heat generated by shear stresses.

Squeeze and Entraining Motion in Nonconformal Line Contacts. Part I—Hydrodynamic Lubrication

1989 ◽  
Vol 111 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Rong-Tsong Lee ◽  
B. J. Hamrock
Keyword(s):  
Hydrodynamic Lubrication ◽  
Dynamic Performance ◽  
Elastohydrodynamic Lubrication ◽  
Constant Load ◽  
Initial Guess ◽  
Maximum Pressure ◽  
Performance Parameters ◽  
Velocity Parameter ◽  
Dimensionless Velocity ◽  
Line Contacts

An analytical solution to the problem of combined entraining and normal squeeze motion in nonconformal line contacts hydrodynamically lubricated with an isoviscous, incompressible lubricant has been obtained without any limitations on dimensionless load, dimensionless entraining velocity, and dimensionless velocity parameter. The dimensionless load and entraining velocity are fixed for a complete range of operating parameters for both normal approach and separation. Results show that the lubrication of the outlet boundary and the location of the maximum pressure move upstream into the inlet region as the central film thickness decreases or the dimensionless velocity parameter increases from negative (normal approach) to positive (normal separation). All the dynamic performance parameters relating to the steady-state bearing performance parameters have been found to be functions of only the dimensionless velocity parameter with constant load and entraining velocity. The dimensionless velocity parameter significantly influenced those dynamic performance parameters. The results of this study will be used as the initial guess for the elastohydrodynamic lubrication of nonconformal line contacts.

Elastohydrodynamic lubrication of coated finite line contacts

2017 ◽  
Vol 232 (9) ◽  
pp. 1077-1092 ◽  
Author(s):  
Shivam S Alakhramsing ◽  
Matthijn B de Rooij ◽  
Dirk J Schipper ◽  
Mark van Drogen
Keyword(s):  
Mechanical Properties ◽  
Film Thickness ◽  
Surface Profile ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Maximum Pressure ◽  
Lubrication Performance ◽  
Line Contacts ◽  
Finite Line ◽  
Axial Surface

In this work, a finite element-based model is presented that simulates elastohydrodynamic lubrication in coated finite line contacts. Using this model, the film thickness and pressure distributions, between a straight roller with rounded edges on a plate, were analyzed. The model was successfully validated against representative results reported in literature. Parameter studies were conducted to study the influence of varying operating conditions, axial surface profile parameters and coating mechanical properties on the overall elastohydrodynamic lubrication behavior of the contact. It was found that in contrast with typical elastohydrodynamic lubrication behavior, the maximum pressure and minimum film thickness, which are located at the rear of the contact, are largely influenced by variations in load. Results also reveal that axial surface profile parameters and coating mechanical properties may act as amplifiers to the effect of load on pressure and film thickness distribution and can thus, if smartly chosen, significantly enhance lubrication performance.

Simulation of Plasto-Elastohydrodynamic Lubrication in Line Contacts of Infinite and Finite Length

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Tao He ◽  
Jiaxu Wang ◽  
Zhanjiang Wang ◽  
Dong Zhu
Keyword(s):  
Surface Roughness ◽  
Finite Length ◽  
3D Model ◽  
Three Dimensional ◽  
Elastohydrodynamic Lubrication ◽  
Axial Direction ◽  
Contact Length ◽  
Line Contact ◽  
Line Contacts ◽  
3D Surface Topography

Line contact is common in many machine components, such as various gears, roller and needle bearings, and cams and followers. Traditionally, line contact is modeled as a two-dimensional (2D) problem when the surfaces are assumed to be smooth or treated stochastically. In reality, however, surface roughness is usually three-dimensional (3D) in nature, so that a 3D model is needed when analyzing contact and lubrication deterministically. Moreover, contact length is often finite, and realistic geometry may possibly include a crowning in the axial direction and round corners or chamfers at two ends. In the present study, plasto-elastohydrodynamic lubrication (PEHL) simulations for line contacts of both infinite and finite length have been conducted, taking into account the effects of surface roughness and possible plastic deformation, with a 3D model that is needed when taking into account the realistic contact geometry and the 3D surface topography. With this newly developed PEHL model, numerical cases are analyzed in order to reveal the PEHL characteristics in different types of line contact.

Elastohydrodynamic Lubrication of Finite Line Contacts

1983 ◽  
Vol 105 (4) ◽  
pp. 598-604 ◽  
Author(s):  
A. Mostofi ◽  
R. Gohar
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Mineral Oil ◽  
Pressure Variation ◽  
Material Parameters ◽  
Line Contacts ◽  
Finite Line ◽  
Moderate Load ◽  
Infinite Line ◽  
Cylindrical Roller ◽  
Theoretical Results

In this paper, a numerical solution to the elastohydrodynamic lubrication (EHL) problem is presented for a cylindrical roller with axially profiled ends, rolling over a flat plane. Convergence was obtained for moderate load and material parameters (glass, steel, and a mineral oil). Isobars, contours, and section graphs, show pressure variation and film shape. Predictions of film thickness compare favorably with experiments which use the optical interference method, as well as with other theoretical results for an infinite line contact, or an ellipse having a long slender aspect ratio. The maximum EHL pressure occurs near the start of the profiling and can exceed pressure concentrations there predicted by elastostatic theory.

Two Dimensional Modified Reynolds Equation Including Pressure Dependent Viscosity Effect

2012 ◽  
Author(s):  
Jung Gu Lee ◽  
Alan Palazzolo
Keyword(s):  
Reynolds Equation ◽  
Elastohydrodynamic Lubrication ◽  
Fluid Film ◽  
Maximum Pressure ◽  
Elastic Solids ◽  
Pressure Distributions ◽  
Pressure Dependent Viscosity ◽  
Modified Reynolds Equation ◽  
Dependent Viscosity ◽  
Modified Equation

The Reynolds equation plays an important role for predicting pressure distributions for fluid film bearing analysis, One of the assumptions on the Reynolds equation is that the viscosity is independent of pressure. This assumption is still valid for most fluid film bearing applications, in which the maximum pressure is less than 1 GPa. However, in elastohydrodynamic lubrication (EHL) where the lubricant is subjected to extremely high pressure, this assumption should be reconsidered. The 2D modified Reynolds equation is derived in this study including pressure-dependent viscosity, The solutions of 2D modified Reynolds equation is compared with that of the classical Reynolds equation for the ball bearing case (elastic solids). The pressure distribution obtained from modified equation is slightly higher pressures than the classical Reynolds equations.

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