Measurements of Friction in Cold Metal Rolling

1996 ◽  
Vol 118 (3) ◽  
pp. 629-636 ◽  
Author(s):  
P. E. Tabary ◽  
M. P. F. Sutcliffe ◽  
F. Porral ◽  
P. Deneuville
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Strip Thickness ◽  
Secondary Importance ◽  
Smooth Film ◽  
The Mean ◽  
Cold Metal ◽  
Aluminium Strip ◽  
Additive Molecule

Measurements of friction in rolling of aluminium strip on an experimental mill are described. Friction depended most strongly on the ratio Λ of the smooth film thickness to the combined roughness of the roll and strip, and on the reduction in strip thickness. Whether the greater roughness was on the roll or on the strip was found to be unimportant. Varying the oil temperature from 40 to 60°C was also found to be of secondary importance. Profilometry results suggested that friction was determined by the mean film thickness between the surfaces. At the slowest speeds and smallest films, friction was close to the value of 0.09 found in separate measurements in a disk machine of the boundary additive properties. At the highest speed the friction values, which were less than 0.01, could be explained by hydrodynamic lubrication. The transition between these two extremes occurred when the film thickness was of the order of the additive molecule length of 3 nm.

scholarly journals Homogenization in Hydrodynamic Lubrication: Microscopic Regimes and Re-Entrant Textures

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
İ. N. Yıldıran ◽  
İ. Temizer ◽  
B. Çetin
Keyword(s):  
Film Thickness ◽  
Theoretical Study ◽  
Hydrodynamic Lubrication ◽  
Type Equation ◽  
Homogenization Theory ◽  
Review Of The Literature ◽  
Comprehensive Review ◽  
New Models ◽  
The Mean

The form of the Reynolds-type equation which governs the macroscopic mechanics of hydrodynamic lubrication interfaces with a microscopic texture is well-accepted. The central role of the ratio of the mean film thickness to the texture period in determining the flow factor tensors that appear in this equation had been highlighted in a pioneering theoretical study through a rigorous two-scale derivation (Bayada and Chambat, 1988, “New Models in the Theory of the Hydrodynamic Lubrication of Rough Surfaces,” ASME J. Tribol., 110, pp. 402–407). However, the resulting homogenization theory still remains to be numerically investigated. For this purpose, after a comprehensive review of the literature, three microscopic regimes of lubrication will be outlined, and the transition between these three regimes for different texture types will be extensively demonstrated. In addition to conventional textures, representative re-entrant textures will also be addressed.

Hydrodynamic Lubrication of Face Seal in a Turbulent Flow Regime

1996 ◽  
Vol 118 (3) ◽  
pp. 589-600 ◽  
Author(s):  
Jen Fin Lin ◽  
Chih Chung Yao
Keyword(s):  
Porous Material ◽  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Normal Load ◽  
Mixed Lubrication ◽  
Turbulent Regime ◽  
Face Seal ◽  
Hydrodynamic Load ◽  
Asperity Height ◽  
The Mean

Models for thermohydrodynamic lubrication in the turbulent regime are developed for a mechanical end face seal with various combinations of asperity height and roughness pattern. A surface wear model, based on deformation, is established for mixed lubrication such that the displacement is at most equal to the mean asperity height. Only normal load is involved in the solution of asperity deformation, and the mean film thickness is determined based on a total volume conservation hypothesis, in conjunction with an elastic-exponential hardening model. The singularity problem, present in the expected form of the Reynolds equation for a seal surface with circumferentially-oriented roughness grain sphere grooves, is avoided by viewing the seal roughness as porous material, thereby introducing roughness permeability. Flow permeability is thus obtained by combining Darcy’s law for porous material with the average flow model developed by Patir and Cheng for mixed lubrication. The hydrodynamic pressure and thereby the hydrodynamic load support are relatively higher from a seal with radially-oriented roughness. Both the mean film thickness and the hydrodynamic load support are substantially elevated by increasing the composite rms roughness, raising the inlet-flow pressure, and decreasing the rotational speed. Good agreement has been obtained from the comparison between the results herein and Lebeck’s experimental results.

DDC Lubrication: A New Concept in Tribology

1992 ◽  
Vol 114 (1) ◽  
pp. 181-185 ◽  
Author(s):  
K. To̸nder
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Gap Function ◽  
Upper And Lower Bounds ◽  
Roughness Effects ◽  
Cavity Depth ◽  
Roughness Amplitude ◽  
Previously Treated ◽  
The Mean ◽  
Expansion Scheme

A new lubrication concept is presented, Deep Disconnected Cavities. It differs from the lubrication of microcavities, previously treated by other authors, by the deepness of the cavities. The validity of Reynolds’ equation and nonturbulent conditions are assumed. By a Taylor expansion scheme, it is shown that the roughness effects are expressible in terms of roughness factors modifying the Reynolds equation, similar to those proposed by Patir and Cheng (1978). Unlike those established for ordinary roughness, the DDC factors are independent of local film thickness and roughness amplitude (cavity depth), and may therefore be used to modify standard hydro-dynamic parameters. By a different mathematical approach, involving upper and lower bounds on the various hydrodynamic quantities, it is found that Reynolds’ equation and all the other hydrodynamic expressions may be written just as for smooth surfaces, with the following modifications: 1. The film thickness should be expressed by the minimum gap function, and not by the mean gap function. 2. There are, in general, three effective viscosities, lower than the physical one, two of which are associated with the x and y directions respectively and appear in the modified Reynolds equation as well as in the flow terms. The third one appears only in the expression for shear stress.

scholarly journals Elastic hydrodynamic lubrication analysis for a sine movable tooth drive

2018 ◽  
Vol 10 (12) ◽  
pp. 168781401881410 ◽  
Author(s):  
Lizhong Xu ◽  
Wentao Song
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Normal Operation ◽  
Speed Ratio ◽  
Input Shaft ◽  
Load Carrying ◽  
Radial Dimension ◽  
Lubrication Condition ◽  
Shaft Rotation Angle ◽  
Large Speed

The sine movable tooth drive has small radial dimension such that the heat, caused by friction, becomes an important factor in deciding its load-carrying ability. It is important to determine the amount of tooth lubrication in order to reduce the heat caused by the friction. This study provides equations for the meshing performance and provides the forces for the sine movable tooth drive. Using these equations, the minimum oil film thickness for the drive system is investigated. Results show that the minimum film thickness between the movable tooth and input shaft or shell changes periodically along the input shaft rotation angle. A large movable tooth radius and a movable tooth rotation radius could increase the film thickness between the movable tooth and the input shaft or the shell. In addition, a large speed ratio could increase the film thickness between the movable tooth and the input shaft, but this would also decrease the film thickness between the movable tooth and the shell. A large sine amplitude could increase the film thickness between the movable tooth and the input shaft, but this does not change the film thickness between the movable tooth and the shell. Under normal operation speeds, the hydrodynamic lubrication condition occurs between the movable tooth and the input shaft, and the partial membrane hydrodynamic state occurs between the movable tooth and the shell.

Interplay Between Thermoelectric and Thermionic Effects in Heterostructures

2000 ◽  
Author(s):  
Taofang Zeng ◽  
Gang Chen
Keyword(s):  
Film Thickness ◽  
Free Path ◽  
Thermionic Emission ◽  
Approximate Solutions ◽  
Mean Free Path ◽  
Boltzmann Transport ◽  
Thermoelectric Effects ◽  
Double Heterojunction ◽  
The Mean ◽  
Electron Mean Free Path

Abstract When electrons sweep through a double-heterojunction structure, there exist thermionic effects at the junctions and thermoelectric effects in the film. While both thermoelectric and thermionic effects have been studied for refrigeration and power generation applications separately, their interplay in heterostructures is not understood. This paper establishes a unified model including both thermionic and thermoelectric processes based on the Boltzmann transport equation for electrons, and the nonequilibrium interaction between electrons and phonons. Approximate solutions are obtained, leading to the electron temperature and Fermi level distributions inside heterostructures and discontinuities at the interfaces as a consequence of the highly nonequilibrium transport when the film thickness is much smaller than the electron mean free path. It is found that when the film thickness is smaller than the mean free path of electrons, the transport of electrons is controlled by thermionic emission. The coexistence of thermoelectric and thermionic effects may increase the power factor when the electron mean free path is comparable to the film thickness.

scholarly journals Inversion of the Thickness of Crude Oil Film Based on an OG-CNN Model

2020 ◽  
Vol 8 (9) ◽  
pp. 653 ◽  
Author(s):  
Zongchen Jiang ◽  
Yi Ma ◽  
Junfang Yang
Keyword(s):  
Neural Network ◽  
Film Thickness ◽  
Spectral Feature ◽  
Coefficient Of Determination ◽  
Mean Deviation ◽  
Oil Film ◽  
Remote Sensing Technology ◽  
Sensing Technology ◽  
The Mean ◽  
Oil Thickness

In recent years, marine oil spill accidents have occurred frequently, seriously endangering marine ecological security. It is highly important to protect the marine ecological environment by carrying out research on the estimation of sea oil spills based on remote sensing technology. In this paper, we combine deep learning with remote sensing technology and propose an oil thickness inversion generative adversarial and convolutional neural network (OG-CNN) model for oil spill emergency monitoring. The model consists of a self-expanding module for the oil film spectral feature data and an oil film thickness inversion module. The feature data self-expanding module can automatically select spectral feature intervals with good spectral separability based on the measured spectral data and then expand the number of samples using a generative adversarial network (GAN) to enhance the generalization of the model. The oil film thickness inversion module is based on a one-dimensional convolutional neural network (1D-CNN). It extracts the characteristics of the spectral feature data of oil film with different thicknesses, and then accurately inverts the oil film’s absolute thickness. In this study, emulsification was not a factor considered, the results show that the absolute oil thickness inversion accuracy of the OG-CNN model proposed in this paper can reach 98.12%, the coefficient of determination can reach 0.987, and the mean deviation remains within ±0.06% under controlled experimental conditions. In the model stability test, the model maintains relatively stable inversion results under the interference of random Gaussian noise. The accuracy of the oil film thickness inversion result remains above 96%, the coefficient of determination can reach 0.973, and the mean deviation is controlled within ±0.6%, which indicates excellent robustness.

A Contact-Wear Model for the EHL Analysis of Engine Journal Bearings

2005 ◽  
Author(s):  
Ducai Wang
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Surface Profile ◽  
Journal Bearings ◽  
Bearing Surface ◽  
Wear Model ◽  
Contact Wear ◽  
Analysis Technique ◽  
Elastic Distortion ◽  
Account Interaction

Engine journal bearings are now routinely analysed using elasto-hydrodynamic lubrication (EHL) methods [1,2]. This analysis technique takes into account interaction of the hydrodynamic film with the elastic distortion produced in both the bearing and the journal. It has proved a robust analytic tool for designers in predicting the value and location of such parameters as minimum oil film thickness and maximum film pressure. However, for some very heavily loaded cases, the normal EHL analysis technique may fail to produce realistic solutions. Due to ‘cusping’ of the bearing surface under extreme pressures the edges of bearing may be predicted to penetrate the journal surface leading to a ‘negative’ film thickness. In reality, the surfaces will interact and a ‘running-in’ process will result in subtle changes to the bearing surface profile such that a hydrodynamic film can be maintained across the whole bearing surface. This study introduces a contact-wear model which attempts to model this situation.

Lubrication at point contacts

1961 ◽  
Vol 261 (1307) ◽  
pp. 532-550 ◽  
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
Single Point ◽  
Applied Pressure ◽  
Hydrodynamic Theory ◽  
Radius Of Curvature ◽  
Point Contacts ◽  
Wide Range ◽  
Electrical Capacity ◽  
Classical Hydrodynamic

Measurements have been made of the friction, electrical resistance, and electrical capacity between rotating steel cylinders with their axes mutually at right angles. The lubricant was a plain hydrocarbon mineral oil. Nominally the surfaces come together at a single point and the apparatus is designed to ensure that this condition is maintained even if the cylinders wear. It is shown that hydrodynamic lubrication exists over a wide range of conditions. At loads of a few kilograms it persists even when the speed falls below 1 cm/s and at higher speeds (~ 100 cm/s) it is maintained even when the load becomes large enough to cause bulk plastic flow of hardened steel. Hitherto it has been considered that only boundary lubrication could occur under these extreme conditions. At very light loads classical hydrodynamic theory applies but as the load is increased a departure from classical theory occurs because the viscosity of the oil increases under the applied pressure. At heavier loads the pressures become large enough to cause appreciable elastic deformation of the surfaces and a state of elasto-hydrodynamic lubrication is achieved. Under elasto-hydrodynamic conditions the film thickness can be deduced from the measure­ments of electrical capacity. A simplified theory of elasto-hydrodynamic lubrication at point contacts is developed, and the measured values of film thickness are in fairly good agreement with those derived from the theory. However, the variations of film thick­ness with viscosity, speed and radius of curvature forecast by the theory differ significantly from those obtained experimentally. The values of the film thickness range from 2 x 10 -6 cm to more than 1 x 10 -4 cm. The results, over the whole range, conform to a regular pattern and there is no evidence of any disturbing influence of the surface molecular fields, even with the thinnest films.

Analysis of Oil Film Thickness on a Piston Ring of Diesel Engine: Effect of Oil Film Temperature

2001 ◽  
Author(s):  
Yasuo Harigaya ◽  
Michiyoshi Suzuki ◽  
Masaaki Takiguchi
Keyword(s):  
Diesel Engine ◽  
Temperature Distribution ◽  
Heat Flow ◽  
Film Thickness ◽  
Piston Ring ◽  
Reynolds Equation ◽  
Energy Equation ◽  
Two Dimensional ◽  
Oil Film ◽  
The Mean

Abstract This paper describes that an analysis of oil film thickness on a piston ring of diesel engine. The oil film thickness has been performed by using Reynolds equation and unsteady, two-dimensional (2-D) energy equation with a heat generated from viscous dissipation. The temperature distribution in the oil film is calculated by using the energy equation and the mean oil film temperature is computed. Then the viscosity of oil film is estimated by using the mean oil film temperature. The effect of oil film temperature on the oil film thickness of a piston ring was examined. This model has been verified with published experimental results. Moreover, the heat flow at ring and liner surfaces was examined. As a result, the oil film thickness could be calculated by using the viscosity estimated from the mean oil film temperature and the calculated value is agreement with the measured values.

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