Partial Hydrodynamic Lubrication Research Articles

Investigation of Lubrication Characteristics for a Soft Contact Lens

It is popular to wear the contact lens nowadays. Also, the output value of the contact lens is estimated more than 4 billion NT dollar every year. Because the phenomena of the contact lenses are very complicated, the relevant mechanisms are not well understood. Thus, the security of contact lens needs to be further investigated. In the lubricated mechanism of the contact lens, there is a layer of tear between the contact lens and cornea. The contact lens’ behavior is akin to that of a slider bearing. The lens represents the slider, the eye plays the role of the stationary pad, and the tear film is the lubricant. Hence, hydrodynamics and contact mechanisms of a contact lens are quite a fascinating subject that is relevant to the science of tribology. In the paper, the lubrication mechanisms include the partial hydrodynamic lubrication (contact lens roughness), contact mechanics and Newtonian fluid mechanics have been established. The parameters of roughness, flow factor, tear film geometry, and hydrodynamic pressure distribution are discussed. The developed technology increases the safety of contact lens.

A comprehensive mathematical model for an accurate calculation of the oil film thickness of strip cold rolling

The surface quality of cold rolled strip is related to a greater extent on the rolling oil film thickness, and there are many factors that affect the oil film thickness. Considering the various factors comprehensively, an integrated mathematical model is established, such as roughness of rolls and strips, elastohydrodynamic lubrication, friction heat and plastic deformation heat in the rolling zone, viscosity varying with temperature and pressure, etc. A series of equations are developed, such as the Reynolds equation of partial membrane hydrodynamic lubrication based on average flow theory, equation of oil film thickness on rough elastic surface, the thermal interface equations between strip, oil film and roller surface, surface asperity contact pressure equation, lubricant viscosity and density equations, motion equation of the oil film, etc. This model is solved by finite difference method to get the film pressure, oil film thickness, and temperature distribution in the rolling zone. The average rolling pressure, the roll, and strip temperature calculated by the model are very close to the field test results. Comparing the minimum film thickness calculated by the model with the regression formula of other literature test, the error is less than 10%. The minimum oil film thickness is analyzed. It increases with the decrease of the rolling force and is approximately proportional to the rolling speed and lubricant viscosity.

Experimental and numerical study on water-lubricated rubber bearings

Purpose – Water-lubricated rubber bearing is one of the most appropriate bearings for underwater use. The most popular design used widely today is the straight fluted rubber bearing. The special configuration leads to partial hydrodynamic lubrication and low load capacity. A new bearing bush structure with two cavities which is favorable for constructing continuous hydrodynamic lubrication was designed and studied. The paper aims to discuss these issues. Design/methodology/approach – A new bearing bush structure with two cavities which is favorable for constructing continuous hydrodynamic lubrication was designed. The apparatus for studying the tribological behaviors of the two types of water-lubricated rubber bearings has been devised and established in the paper. The experimental studies on the tribological properties of the rubber bearings have been conducted under different loads and velocities. The eccentricity ratio of the new structure rubber bearing with two cavities was measured in experiment and the load capacity was calculated by numerical simulation. Findings – The experimental results show that the friction coefficient decreases with increasing velocity; the friction coefficient increases sharply with the rising temperature, the friction coefficient increases at first and then decreases with increasing load for fluted rubber bearings. The numerical results were in good agreement with the experimental results. The numerical results show that complete hydrodynamic lubrication can be formed in the new designed rubber bearing with two cavities. The experimental and numerical results all indicate that there is an appropriate bearing clearance which the friction coefficient is minimum and the load capacity is maximum. Originality/value – A new bearing bush structure with two cavities which is beneficial to constructing continuous hydrodynamic lubrication film was designed. A new apparatus for studying the tribological behaviors of the two types of water-lubricated rubber bearings has been devised and established. Experimental and numerical study on the new structure rubber bearing were conducted in the paper.

Numerical Analysis of Hydrodynamic Lubrication on Water-Lubricated Rubber Bearings

Water lubricated rubber bearings are one of the most appropriate bearings for underwater use. The most popular design used widely today is the straight fluted rubber bearing. The special configuration leads to partial hydrodynamic lubrication and low load capacity. A new bearing bush structure which is favorable for constructing continuous hydrodynamic lubrication was designed and produced for experiment in the paper. The eccentricity ratio of the new structure rubber bearing was measured under different loads in experiment. Used the measured eccentricity ratios, the load capacity was calculated by numerical simulation and compared with the given test values. The calculated values were in good agreement with the given test results. The results show that complete hydrodynamic lubrication can be formed in the new designed rubber bearing. The experimental results also indicate that there is an appropriate bearing clearance which the load capacity is up to the maximum.

Chemical Mechanical Polishing in Elastic Contact and Partial Hydrodynamic Lubrication: Modeling and Experiments

Chemical mechanical polishing (CMP) has become a primary technique for planarization of semiconductor wafers in submicro device fabrication. Increasing demands for high uniformity and dimensional precision make previously discountable levels of asperity, powder slurry, and wafer-pad contact significant. In this study, a CMP model considering both the elastic microcontact mechanism and the grain flow with roughness effects is presented. The model applies the average lubrication equation with partial hydrodynamic lubrication theory and elastic microcontact theory proposed by Greenwood and Williamson. In experiments, a test rig is used to simulate the CMP process and acquire the signals of polishing. The shear force is measured by a load transducer mounted on the lever and connected with the polishing head during CMP process. Furthermore, the theoretical results are compared with the experimental data. The theoretical and experimental results increase the understanding of CMP process.

An improved model considering elastic—plastic contact and partial hydrodynamic lubrication for chemical mechanical polishing

Chemical mechanical polishing (CMP) has become a primary technique for planarization of semiconductor wafers in sub-micro device fabrication. A physical CMP model combines the effects of grain flow hydrodynamic lubrication, pad roughness, and asperity contact between wafer and pad. In this study, an improved CMP model, considering both the grain flow with roughness effects and the micro-contact mechanism, is proposed. The model applies the average lubrication equation with partial hydrodynamic lubrication theory and considers the elastic—plastic micro-contact theory. The applied load acting on the wafer is balanced by the slurry pressure in the non-contact area, and the surface asperity contact force in the contact area. The effects of the CMP parameters including applied load, rotation speed, particle size, and pad roughness are studied and discussed. The simulation results compare well with experimental data in the literature and contribute to further understanding in wafer—pad contact mechanism.

Modelling and simulation of friction for toroidal drive

In this paper, the relative motions for the toroidal drive are analysed. The sliding factors between the planet and the stator or the worm are given. The friction coefficients between the planet and the stator or the worm under asperity contact or hydrodynamic lubrication are presented. The friction coefficients between the planet and the stator or the worm under partial hydrodynamic lubrication are also given. Changes of the sliding factors between the planet and the stator or the worm along with drive parameters are presented. The friction coefficients between the planet and the stator or the worm under hydrodynamic lubrication are compared, and the changes of them along with drive parameters are discussed. Under asperity contact, the changes of the friction coefficient between the planet and the stator along with the drive parameters are given as well. Under partial hydrodynamic lubrication, the changes of the friction coefficient between the planet and the stator along with the ratio of the film thickness to mean standard deviations of the height distributions for two teeth are also discussed. These results can be used for friction design of the toroidal drive.

Elasto-Partial Hydrodynamic Contact Model for Chemical Mechanical Polishing

Chemical mechanical polishing (CMP) has become a primary technique for the planarization of semiconductor wafers in submicrometer device fabrication. Increasing demands for high uniformity and dimensional precision make previously discountable levels of asperity, powder slurry, and wafer-pad contact significant. In this study, an improved model considering both the elastic microcontact mechanism and the grain flow with roughness effects is proposed. The model applies the average lubrication equation with the partial hydrodynamic lubrication theory and elastic microcontact theory proposed by Greenwood and Williamson. The external force acting on the wafer is supported by the partial hydrodynamic slurry pressure in the noncontact area and the surface asperity contact force in the contact area. This model predicts slurry flow film thickness under a variety of the CMP parameters, including applied load, rotation speed, particle size, and pad roughness. The results compare well with experimental data in the literature. Furthermore, the contact ratio of area and removal rate are studied and discussed.

The Characteristic of Abrasive Particle in Chemical – Mechanical Polishing

Chemical Mechanical Polishing (CMP) is the key technique for wafer global planarization. However, the characteristic of abrasive particle, including particle size and grain/grain collision elasticity, plays an important role in CMP process. This investigation analyzes the slurry flow between the wafer and pad using a grain flow model with partial hydrodynamic lubrication theory. This model predicts the film thickness and remove rate of the slurry flow under a variety of the CMP parameters including load, rotation speed, pad roughness, grain/grain collision elasticity and grain size. The theoretical results compare well with the previous experiment data. This study elucidates the grain characteristics during CMP process. It also contributes to the understanding of abrasive particle effects in the chemical mechanical polishing mechanism.

Surface anisotropy for monitoring the wear of IC engine cylinders

AbstractThe present work proposes a methodology for monitoring the wear of internal combustion engine cylinders. This could be useful in calculating the time at which maintenance should be done on such a tribosystem or in determining its lifetime. On the basis of experimental data obtained using a friction—wear simulator, and through the determination of certain standardised and non‐standardised micro‐geometric parameters of the cylinder surface that change with respect to operating time, it is shown that the characteristic that exhibits the most variation is the cylinder surface anisotropy. This factor participates to a large degree in the partial hydrodynamic lubrication mechanism of the reciprocating piston ring system and, as it is associated with the stage of wear, better expresses the characteristics of the cylinder's worn surface. As a consequence, by prescribing a limit for the maximum acceptable anisotropy as a basic criterion, the ultimate tolerable stage of wear is controlled simultaneously and vice versa.

Improved Model of Wafer/Pad Powder Slurry for CMP

Chemical mechanical polishing (CMP) is a key technique for wafer global planarization. Increasing demands for high uniformity and dimensional precision make previously discountable levels of asperity and particle effects significant. However, particle size and pad asperity have not been considered simultaneously in previous literature. This study presents a grain flow model which applies the average lubrication equation with partial hydrodynamic lubrication theory, thereby analyzing slurry flow between wafer and pad and taking into account both grain flow and roughness effects. This model predicts slurry flow film thickness with various convex wafer curvature radii under a variety of the CMP parameters, including applied load, rotation speed, dome height, particle size, and pad roughness. Furthermore, the influence of particle size and pad asperity on removal rate is investigated. The results compare well with experimental data in the literature. © 2003 The Electrochemical Society. All rights reserved.

Partial Hydrodynamic Lubrication With Large Fractional Contact Areas

An alternative average Reynolds equation for use under conditions of large fractional contact area is proposed. The flow factors for this form of the equation are calculated for a variety of longitudinal surfaces and the results are shown to be relatively insensitive to the initial height distribution. Pressure and shear flow factors for the Christensen height distribution and a variety of Peklenik surface pattern parameters are also derived from the work of Patir and Cheng, Lo and Tripp. These are represented by semi-empirical equations over the full range of contact conditions. The implications of the results, with respect to the lubrication of metal forming processes, is discussed.

Stability characteristics of rough submerged oil elliptical bearings under dynamic load

This paper discusses the effect of surface roughness on the stability of submerged oil elliptical journal bearings under unidirectional constant and unidirectional periodic load. The non-linear transient simulation, taking the oil film history into account, has been used to predict the threshold of instability. The average flow model of Patir and Cheng (An average flow model for determining effects of three-dimensional roughness on partial hydrodynamic lubrication. Trans. ASME, Journal of Lubrication Technology, 1979, 100, 12–17) has been used to describe the surface roughness effects. The effect of ellipticity ratio and that of various surface roughness parameters, viz., composite surface roughness, roughness orientation pattern and variance ratio on the stability has been studied.

Numerical Simulation of Engagement of Paper Based Wet Clutch Facing

Theoretical analysis was carried out on the engagement process of a paper based wet clutch. The annular multidisk clutch in a SAE#2 tester was chosen as an example. The average flow model on partial hydrodynamic lubrication proposed by Patir and Cheng was employed for the analysis of squeeze motion taking the permeability, the compressive strain, and the asperity contact of paper facing into account. Simultaneously, the equations of heat conduction were solved to calculate the viscosity reduction due to frictional heat generation. The theoretical torque curve agreed qualitatively with the experimental one in spite of the many assumptions made in this analysis.

Casing Wear: Laboratory Measurements and Field Predictions

Summary Casing wear caused by rotation of nonhardbanded tool joints has been investigated with a full-sized test machine. Three grades of casing were used during this study: K55, N80, and PI 10. Tests were conducted in both water-based and oil-based muds. Contact forces between the tool joint and casing were either 1,000 or 2,000 lbf [4.4 or 8.9 kN]. Both the casing wear and friction forces were measured during the tests. A linear wear-efficiency model was used to correlate the data. This model relates casing-metal removal to the amount of energy dissipated as friction in the wear process. The wear-efficiency model fits the data well and is easily used for field wear predictions. The data from this study indicate that high-strength casing steels wear more rapidly than K55 and that wear in oil muds is possibly more rapid than in water muds. Partial hydrodynamic lubrication occurred during many tests; friction measurements and the wear-efficiency model were used to account for its effects.

An Average Flow Model for Determining Effects of Three-Dimensional Roughness on Partial Hydrodynamic Lubrication

A new approach is utilized to determine the effects of surface roughness on partially lubricated contacts. An average Reynolds equation for rough surfaces is defined in terms of pressure and shear flow factors, which are obtained by numerical flow simulation. Through the use of measured or numerically generated rough surfaces, any three dimensional roughness structure can be analyzed with this method. The average Reynolds equation is obtained for isotropic surfaces, and for surfaces with directional patterns. The flow factors for these surfaces are expressed as empirical relations in terms of h/σ and a surface characteristic γ defined as the ratio of x and y correlation lengths.

Review on marginal and partial hydrodynamic lubrication

Review on marginal and partial hydrodynamic lubrication