The Effect of Viscous Shear Heating on Both Film Thickness and Rolling Traction in an EHL Line Contact—Part I: Fully Flooded Conditions

1978 ◽  
Vol 100 (3) ◽  
pp. 346-352 ◽  
Author(s):  
P. G. Goksem ◽  
R. A. Hargreaves
Keyword(s):  
Experimental Data ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Thermal Effect ◽  
Line Contact ◽  
Heating Effect ◽  
Viscous Shear ◽  
Isothermal Case ◽  
Shear Heating ◽  
Contact Part

A theoretical analysis of both fully flooded rolling traction and film thickness in an EHL line contact is described and modified formulas for fully flooded isothermal conditions are presented. These are compared with the Grubin, Dowson, and Higginson film thickness formulas, and the rolling traction theory by Archard and Baglin (1975). The effect of viscous shear heating in the inlet region has been investigated and new equations for both fully flooded film thickness and rolling traction, including this thermal effect, are introduced. These equations predict significant reductions in both film thickness and rolling traction, relative to the isothermal case, as speed is increased. Viscous shear heating effect is found to be negligible only at very low rolling speeds. The results of the theoretical analysis compare well with experimental data presented by Dyson, Naylor, and Wilson (1966) and Adams and Hirst (1973).

The Effect of Viscous Shear Heating on Both Film Thickness and Rolling Traction in an EHL Line Contact—Part II: Starved Conditions

1978 ◽  
Vol 100 (3) ◽  
pp. 353-358 ◽  
Author(s):  
P. G. Goksem ◽  
R. A. Hargreaves
Keyword(s):  
Theoretical Analysis ◽  
Film Thickness ◽  
Approximate Equation ◽  
Theoretical Work ◽  
Line Contact ◽  
Viscous Shear ◽  
Isothermal Case ◽  
Shear Heating ◽  
Boundary Distance ◽  
Contact Part

A theoretical analysis of both fully flooded rolling traction and film thickness in an EHL line contact has been presented in Part I of this paper. The effect of viscous shear heating was investigated and the results predict a significant reduction in both fully flooded film thickness and rolling traction, relative to the isothermal case, as speed is increased. In this part of the Series, the analysis is extended to consider the calculation of starved rolling traction and film thickness, including viscous shear heating of the lubricant in the inlet region. An approximate equation has been developed, which predicts both the isothermal and non isothermal starved film thickness for all conditions of inlet boundary distance, rolling speed, load, geometry, material constants and lubricant properties. The results show that both rolling traction and film thickness are significantly reduced from the starved isothermal case. For the starved isothermal case, the theoretical analysis for the film thickness agrees closely with experimental data and published empirical formula by Wymer and Cameron, (1974) and the theoretical work of Wolveridge, et al. (1971).

The Influence of Quantizing Magnetic Field on The Magnetic Susceptibilities in Ultra Thin Films of Dilute Magnetic Materials

1993 ◽  
Vol 313 ◽  
Author(s):  
Kamakhya P Ghatak ◽  
S. N. Biswas
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Thin Films ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Magnetic Materials ◽  
Ultrathin Films ◽  
Surface Concentration ◽  
Magnetic Susceptibilities ◽  
Quantizing Magnetic Field

ABSTRACTIn this paper we have studied the dia and paramagnetic susceptibilities of the holes in ultrathin films of dilute magnetic materials in the presence of a quantizing magnetic field and compared the same with that of the bulk specimens under magnetic quantization for the purpose of relative comparison. It is found, taking Hg1−xMnxTe and Cd1−xMnxSe as examples, that both the susceptibilities increase with decreasing film thickness and increasing surface concentration in oscillatory Manners. The numerical values of the susceptibilities in ultrathin films of dilute magnetic materials are greater than that of the bulk and the theoretical analysis is in agreement with the experimental data as reported elsewhere.

Thermal and Starvation Effects on the Minimum Film Thickness in Inlet Zone in Cold Rolling

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
P. Singh ◽  
R. K. Pandey ◽  
Y. Nath
Keyword(s):  
Film Thickness ◽  
Temperature Rise ◽  
Speed Reduction ◽  
Heating Effects ◽  
Empirical Relations ◽  
Viscous Shear ◽  
Minimum Film Thickness ◽  
Starvation Effects ◽  
Shear Heating ◽  
Inlet Zone

The main objective of this research is to analyze the variation of minimum film thickness in the inlet zone of roll-strip interface by incorporating starvation and viscous shear heating effects at high rolling speeds (5–20m∕s), reduction ratios (0.05–0.20), and slip values (varying up to 20%). An additional objective of this paper is to develop empirical relations for predictions of minimum film thicknesses (both isothermal and thermal) and maximum film temperature rise in the inlet zone of the lubricated roll strip contact as functions of roll-speed, reduction ratio, material parameter, slip, and starvation parameter. An efficient numerical method based on Lobatto quadrature technique is adopted for rigorous analysis of the present problem. The results reveal that the existence of starvation seems to be beneficial in terms of reduction in maximum film temperature rise as well as reduction in quantity of oil required for lubrication provided thin continuous film exists at the contact.

Inlet Shear Heating in Elastohydrodynamic Lubrication

1973 ◽  
Vol 95 (4) ◽  
pp. 417-423 ◽  
Author(s):  
J. A. Greenwood ◽  
J. J. Kauzlarich
Keyword(s):  
Shear Rate ◽  
Theoretical Analysis ◽  
Film Thickness ◽  
Temperature Rise ◽  
Thermal Effects ◽  
Elastohydrodynamic Lubrication ◽  
Oil Film ◽  
Comparison With Experiment ◽  
Pure Rolling ◽  
Shear Heating

In EHL, the oil film thickness of rollers is controlled by the rate at which the oil is drawn into the conjunction of the disks by the moving surfaces of the rollers. The theory often assumes isothermal conditions in the inlet although it can be shown that the maximum shear rate often exceeds 106 sec−1, even in pure rolling. A theoretical analysis is presented for the oil temperature rise in the inlet of rollers, and the result is applied to predict the consequent film thickness. It is found that thermal effects on film thickness are only negligible at low rolling speeds. A comparison with experiment supports the conclusion that the thinning of the film thickness below that predicted by isothermal theory is substantially explained by inlet shear heating of the lubricant.

Lubrication state identification of the line contact tribo-pair under a pure rolling condition with ultrasonic method

2021 ◽  
pp. 135065012110337
Author(s):  
Zhihe Duan ◽  
Tonghai Wu
Keyword(s):  
Theoretical Analysis ◽  
Film Thickness ◽  
Ultrasonic Method ◽  
Elastohydrodynamic Lubrication ◽  
Theoretical Models ◽  
Lubrication Theory ◽  
Operating Conditions ◽  
Line Contact ◽  
Oil Film ◽  
Pure Rolling

A line contact tribo-pair is a key mechanism unit in rolling bearings, which is often characterized by ultra-high contact pressure and ultra-thin oil film. Elastohydrodynamic lubrication is often adopted to characterize the lubrication state of such a tribo-pair. As a primary parameter for elastohydrodynamic lubrication, the oil film thickness is often evaluated with simplified theoretical models or complicated measurements. So far, a comprehensive verification of the lubrication states in a real line-contact tribo-pair, however, is rarely reported. Focusing on the roller/ring tribo-pair of a wet-lubricated rolling bearing under pure rolling conditions, this study investigates the lubrication states by integrating multiple theories. Five regions including isoviscous hydrodynamic, piezoviscous hydrodynamic, elastohydrodynamic lubrication, mixture lubrication, and boundary lubrication regions can be identified using the framework. Then, validation experiments are carried out on a line contact tribo-pair test rig under the same operating conditions applied in the theoretical analysis. The oil film thickness is measured by the ultrasonic method. The analysis results demonstrate that only two regions, the elastohydrodynamic lubrication and mixture lubrication regions, can be identified using the experimental data. The identified elastohydrodynamic lubrication and mixture lubrication regions are consistent with theoretical analysis; and the Blok equation and elastohydrodynamic lubrication theory are suggested to calculate the oil film thickness in the elastohydrodynamic lubrication and mixture lubrication regions, respectively. Moreover, the oil film thickness calculated by the Dowson equation is larger than that based on the elastohydrodynamic lubrication theory due to a different viscous pressure equation.

Microdiffraction Patterns of Small Metallic Particles II; Theoretical Analysis

1982 ◽  
Vol 40 ◽  
pp. 668-669
Author(s):  
A. Gómez ◽  
P. Schabes-Retchkiman ◽  
M. José-Yacamán ◽  
T. Ocaña
Keyword(s):  
Experimental Data ◽  
Electron Diffraction ◽  
Theoretical Analysis ◽  
Size Range ◽  
Dynamical Theory ◽  
Metallic Particles ◽  
Splitting Effect

The splitting effect that is observed in microdiffraction pat-terns of small metallic particles in the size range 50-500 Å can be understood using the dynamical theory of electron diffraction for the case of a crystal containing a finite wedge. For the experimental data we refer to part I of this work in these proceedings.

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.

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.

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