Mixed Lubrication of “Parallel” Plane Sliders

1972 ◽  
Vol 39 (1) ◽  
pp. 36-40
Author(s):  
D. S. Bedi ◽  
M. J. Hillier
Keyword(s):  
Theoretical Model ◽  
Friction Coefficient ◽  
Critical Speed ◽  
Mixed Lubrication ◽  
Parallel Plane ◽  
Stick Slip ◽  
Lubrication Conditions ◽  
Film Lubrication ◽  
Slip Phenomenon ◽  
Fluid Film Lubrication

A theoretical model for the friction coefficient indicates two critical speeds of sliding. The lower critical speed corresponds to a change-over from boundary to mixed lubrication conditions, the higher critical speed a transition to full fluid-film lubrication at angles of inclination less than 0.01 deg. The first critical speed appears to be associated with the “stick-slip” phenomenon.

scholarly journals Contact stiffness and damping of spiral bevel gears under transient mixed lubrication conditions

Friction ◽  
2021 ◽  
Author(s):  
Zongzheng Wang ◽  
Wei Pu ◽  
Xin Pei ◽  
Wei Cao
Keyword(s):  
Contact Stiffness ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Spiral Bevel Gears ◽  
Bevel Gears ◽  
Dry Contact ◽  
Spiral Bevel ◽  
Stiffness And Damping ◽  
Lubrication Conditions ◽  
Film Lubrication

AbstractExisting studies primarily focus on stiffness and damping under full-film lubrication or dry contact conditions. However, most lubricated transmission components operate in the mixed lubrication region, indicating that both the asperity contact and film lubrication exist on the rubbing surfaces. Herein, a novel method is proposed to evaluate the time-varying contact stiffness and damping of spiral bevel gears under transient mixed lubrication conditions. This method is sufficiently robust for addressing any mixed lubrication state regardless of the severity of the asperity contact. Based on this method, the transient mixed contact stiffness and damping of spiral bevel gears are investigated systematically. The results show a significant difference between the transient mixed contact stiffness and damping and the results from Hertz (dry) contact. In addition, the roughness significantly changes the contact stiffness and damping, indicating the importance of film lubrication and asperity contact. The transient mixed contact stiffness and damping change significantly along the meshing path from an engaging-in to an engaging-out point, and both of them are affected by the applied torque and rotational speed. In addition, the middle contact path is recommended because of its comprehensive high stiffness and damping, which maintained the stability of spiral bevel gear transmission.

A Mixed-TEHL Analysis of Cam-Roller Contacts Considering Roller Slip: On the Influence of Roller-Pin Contact Friction

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Shivam S. Alakhramsing ◽  
Matthijn B. de Rooij ◽  
Aydar Akchurin ◽  
Dirk J. Schipper ◽  
Mark van Drogen
Keyword(s):  
Friction Coefficient ◽  
Thermal Effects ◽  
Mixed Lubrication ◽  
Contact Friction ◽  
Sudden Increase ◽  
Low Friction ◽  
Pure Rolling ◽  
Lubrication Performance ◽  
Cam Follower ◽  
Film Lubrication

In this work, a mixed lubrication model, applicable to cam-roller contacts, is presented. The model takes into account non-Newtonian, thermal effects, and variable roller angular velocity. Mixed lubrication is analyzed using the load sharing concept, using measured surface roughness. Using the model, a quasi-static analysis for a heavily loaded cam-roller follower contact is carried out. The results show that when the lubrication conditions in the roller-pin contact are satisfactory, i.e., low friction levels, then the nearly “pure rolling” condition at the cam-roller contact is maintained and lubrication performance is also satisfactory. Moreover, non-Newtonian and thermal effects are then negligible. Furthermore, the influence of roller-pin friction coefficient on the overall tribological behavior of the cam-roller contact is investigated. In this part, a parametric study is carried out in which the friction coefficient in the roller-pin contact is varied from values corresponding to full film lubrication to values corresponding to boundary lubrication. Main findings are that at increasing friction levels in the roller-pin contact, there is a sudden increase in the slide-to-roll ratio (SRR) in the cam-roller contact. The value of the roller-pin friction coefficient at which this sudden increase in SRR is noticed depends on the contact force, the non-Newtonian characteristics, and viscosity–pressure dependence. For roller-pin friction coefficient values higher than this critical value, inclusion of non-Newtonian and thermal effects becomes highly important. Furthermore, after this critical level of roller-pin friction, the lubrication regime rapidly shifts from full film to mixed lubrication. Based on the findings in this work, the importance of ensuring adequate lubrication in the roller-pin contact is highlighted as this appears to be the critical contact in the cam-follower unit.

scholarly journals Tribological functionalization of titanium alloys by Micro-Arc Oxidation for marine applications

2020 ◽  
Vol 321 ◽  
pp. 09001
Author(s):  
Aude MATHIS ◽  
Thierry MILLOT ◽  
Vincent BRANGER ◽  
Remy MULLER ◽  
Jean-Yves GUENEHEUX
Keyword(s):  
Friction Coefficient ◽  
Titanium Alloys ◽  
Pure Titanium ◽  
Dynamic Contact ◽  
Electrochemical Process ◽  
Commercially Pure Titanium ◽  
Tribological Behaviour ◽  
Stick Slip ◽  
Micro Arc Oxidation ◽  
Slip Phenomenon

Micro-arc Oxidation (MAO) process is a plasma assisted electrochemical process, which allows formation of ceramic-like dry oxides on top of light alloys surfaces. The good corrosion resistance as well as the low density of titanium alloys are recognized and so required for conception of structural parts in marine environment. However, their tribological behaviour reveals an important tendency to stick-slip phenomenon, which makes use of these alloys for dynamic contact mechanisms difficult. Through the MAO project from IRT M2P, formation of a MAO coating composed of aluminium titanate has been investigated to improve tribological behaviour of a commercially pure titanium (Grade 2) and an α+β alloy (TA6V, Grade 5). Pin-on-disc testing has been carried out to evaluate friction coefficient and the presence or not of stick-slip phenomenon in various contact configurations (involving non-treated titanium surfaces, MAO treated surfaces, with steel or titanium balls …) in dry or artificial seawater media. Those test campaigns are completed by evaluation of fatigue behaviour, and tribological testing on a demonstrator. Finally, this study highlights influence of MAO coating on diminishing (to removed) stick-slip phenomenon, accompanied by a reduction of friction coefficient, whatever the kind of contact (single treated surface or both ones) and the medium.

scholarly journals Mixed and Fluid Film Lubrication Characteristics of Worn Journal Bearings

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Toshiharu Kazama ◽  
Yukihito Narita
Keyword(s):  
Frictional Coefficient ◽  
Journal Bearings ◽  
Mixed Lubrication ◽  
Operating Conditions ◽  
Fluid Film ◽  
Asperity Contact ◽  
Lubrication Regimes ◽  
Lubrication Characteristics ◽  
Film Lubrication ◽  
Fluid Film Lubrication

The mixed and fluid film lubrication characteristics of plain journal bearings with shape changed by wear are numerically examined. A mixed lubrication model that employs both of the asperity-contact mechanism proposed by Greenwood and Williamson and the average flow model proposed by Patir and Cheng includes the effects of adsorbed film and elastic deformation is applied. Considering roughness interaction, the effects of the dent depth and operating conditions on the loci of the journal center, the asperity-contact and hydrodynamic fluid pressures, friction, and leakage are discussed. The following conclusions are drawn. In the mixed lubrication regime, the dent of the bearing noticeably influences the contact and fluid pressures. For smaller dents, the contact pressure and frictional coefficient reduce. In mixed and fluid film lubrication regimes, the pressure and coefficient increase for larger dents. Furthermore, as the dent increases and the Sommerfeld number decreases, the flow rate continuously increases.

scholarly journals Friction coefficient in mixed lubrication: A simplified analytical approach for highly loaded non-conformal contacts

2017 ◽  
Vol 9 (7) ◽  
pp. 168781401770626 ◽  
Author(s):  
Javier Echávarri Otero ◽  
Eduardo de la Guerra Ochoa ◽  
Enrique Chacón Tanarro ◽  
Benito del Río López
Keyword(s):  
Friction Coefficient ◽  
Thermal Effects ◽  
Mixed Lubrication ◽  
Good Precision ◽  
Experimental Conditions ◽  
Lubrication Regime ◽  
Line Contacts ◽  
Mixed Lubrication Regime ◽  
Lubrication Conditions ◽  
Highly Loaded

This article presents an analytical model for predicting friction in mixed lubrication regime. The calculations consider load shared between roughness asperities and the lubricant film, as well as the appearance of thermal effects in the contact and the influence of the lubricant rheology. Tests using tribometers have been performed to measure the friction coefficient in non-conformal surfaces for both point and line contacts. This allows verifying the results of the model under a broad range of experimental conditions with an influence on the lubrication conditions. Reasonably good precision has been found in the results obtained, which combined with a simplicity of use confers the model a high practical utility for rough estimates of the friction coefficient under mixed lubrication.

An Experimental Investigation of Stick-Slip in Hydrostatic Extrusion Using Wax to Simulate Metals

1976 ◽  
Vol 98 (3) ◽  
pp. 795-799 ◽  
Author(s):  
D. Egerton ◽  
W. B. Rice
Keyword(s):  
Experimental Investigation ◽  
Pressure Pulse ◽  
Pressure Fluctuations ◽  
Hydrostatic Extrusion ◽  
Fluid Film ◽  
Stick Slip ◽  
Film Lubrication ◽  
Fluid Film Lubrication

This paper describes an experimental investigation undertaken to check the explanation advanced by Rice and Iyengar for the violent pressure fluctuations which they observed during hydrostatic extrusion of wax. The results support the explanation advanced by Rice and Iyengar, confirming their suspicion that extrusion actually stops during the period of violent pressure fluctuations and reinforcing their contention that for short periods of time during each pressure pulse the velocity necessary for initiation of fluid film lubrication is exceeded, causing fluid in the form of a film to be transported into the die during those periods.

Running-in effects on friction of journal bearings under slow sliding speeds

2019 ◽  
Vol 234 (3) ◽  
pp. 362-372
Author(s):  
A Linjamaa ◽  
A Lehtovaara ◽  
M Kallio ◽  
A Léger
Keyword(s):  
Journal Bearings ◽  
Mixed Lubrication ◽  
Bearing Material ◽  
Environmentally Sustainable ◽  
Tin Bronze ◽  
Bearing Materials ◽  
Stribeck Curves ◽  
Remarkable Reduction ◽  
Lubrication Conditions ◽  
Film Lubrication

Hydrodynamic thrust and journal bearings are facing challenges in modern heavy-duty machinery where full film lubrication cannot always be achieved or sustained. This is due to reasons such as start–stop operation, increased power density and the use of thinner lubricants. Although this leads to increased overall efficiency, bearings are operating more often under mixed lubrication conditions. This is why the running-in behavior of the bearing material is important. In this study, running-in behavior of traditional leaded tin bronze and its environmentally sustainable alternative, bimetal bismuth, was studied. Experimental friction tests were performed with journal bearings under full film and mixed lubrication conditions in order to find the Stribeck curves. The results are analyzed using frictional energy, and friction coefficient values based on continuous friction monitoring. Remarkable reduction of friction was observed with both bearing materials due to running-in.

scholarly journals The effect of laser surface texturing to inhibit stick-slip phenomenon in sliding contact

2019 ◽  
Vol 11 (9) ◽  
pp. 168781401987463
Author(s):  
Hao Wang ◽  
Xuan Xie ◽  
Xijun Hua ◽  
Bifeng Yin ◽  
Hang Du ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Friction Coefficient ◽  
Machine Tools ◽  
Laser Surface Texturing ◽  
Lubricating Oil ◽  
Textured Surface ◽  
Slip Effect ◽  
Stick Slip ◽  
Adequate Amount ◽  
Slip Phenomenon

Stick-slip phenomenon in some mechanical structures, especially in machine tools, should be eliminated or inhibited, otherwise the vibration will occur and the position error will inevitably be obtained. In this study, different kinds of surface textures were carried out on the lower samples of the pin-on-disk contact. The starting process of the machine tools was simulated on an Rtec-Multi-Function Tribometer. The stick-slip phenomenon was observed in each kind of samples. However, the stick-slip phenomenon of smooth sample is larger than that of the textured samples. The bulge-textured surface shows excellent anti-stick-slip effect, and the critical stick-slip speed of bulge-textured surface is 95.9% lower than that of the smooth surface. Simultaneously, the anti-stick-slip effect of bulge-textured surface is superior to that of the dent-shaped texturing surface. What’s more, when the amount of lubricating oil is 15 mL, the standard deviation values of friction coefficient and critical speed of stick-slip phenomena (rotational speed when the standard deviation of friction coefficient is abrupt) are the lowest at different rotational speeds. It can be predicted that the bulge textures and adequate amount of lubricating oil (15 mL) can eliminate stick-slip phenomenon when processed in the surface of the machine tool because the bulge textures and adequate amount of lubricating oil can improve frictional state effectively and avoid the slip of the contact surface.

The comprehensive effect of surface texture and roughness under hydrodynamic and mixed lubrication conditions

2017 ◽  
Vol 231 (10) ◽  
pp. 1307-1319 ◽  
Author(s):  
Chenbo Ma ◽  
Yanjun Duan ◽  
Bo Yu ◽  
Jianjun Sun ◽  
Qiaoan Tu
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Hydrodynamic Lubrication ◽  
Diameter Ratio ◽  
Mixed Lubrication ◽  
Textured Surface ◽  
Texture Parameters ◽  
Lubrication Condition ◽  
Lubrication Conditions ◽  
Effect Of Surface

A theoretical study is carried out to investigate the comprehensive effect of the machined roughness and fabricated textures, by solving the average Reynolds equation coupled with a mass-conservative cavitation algorithm and taking into account asperity contact. We analyzed the influence of surface roughness, which is represented by the combined root-mean-square roughness σ and surface pattern parameter γ on the optimum texture parameters including the dimple depth-over-diameter ratio and area density under hydrodynamic and mixed lubrication conditions. The results show that the effect of surface roughness on load-carrying capacity can be ignored under hydrodynamic lubrication condition. Furthermore, the optimum texture parameters under hydrodynamic lubrication condition and the optimum dimple depth-over-diameter ratio under mixed lubrication condition are determined at minimized friction coefficient, which can be taken as the same for smooth-textured surface and rough-textured surface. The corresponding minimum friction coefficient increases with increasing σ and γ, and decreasing dimple area density under mixed lubrication condition.

Application of a Mixed Lubrication Model for Hydrostatic Thrust Bearings of Hydraulic Equipment

1993 ◽  
Vol 115 (4) ◽  
pp. 686-691 ◽  
Author(s):  
Toshiharu Kazama ◽  
Atsushi Yamaguchi
Keyword(s):  
Surface Roughness ◽  
Power Loss ◽  
Mixed Lubrication ◽  
Power Losses ◽  
Thrust Bearings ◽  
Supply Pressure ◽  
Hydraulic Equipment ◽  
Hydrostatic Balance ◽  
Film Lubrication ◽  
Fluid Film Lubrication

On mixed and fluid film lubrication the characteristics of hydrostatic bearings for hydraulic equipment are studied numerically. By applying a mixed lubrication model derived in a previous paper to the bearings, we clarify the effects of the surface roughness, eccentric or moment loads, supply pressure and speed of rotation on the friction, flow rate, and power losses. Introducing the concept of a ratio of hydrostatic balance, we show that the minimum power loss is given as the ratio becomes close to unity.

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