Experimental Study of Lubrication Film Formation in Multiple Contacts Device Under Starved Conditions

2012 ◽  
Author(s):  
Petr Svoboda ◽  
David Kostal ◽  
Ivan Krupka ◽  
Martin Hartl
Keyword(s):  
Experimental Study ◽  
Film Thickness ◽  
Numerical Models ◽  
Film Formation ◽  
Lubrication Film ◽  
Multiple Contacts ◽  
Optical Test ◽  
Starved Lubrication ◽  
Traction Drives ◽  
Lubrication Conditions

Some machine elements such as gears, rolling bearings, cams and traction drives operate under starved lubrication conditions where the average lubricant film thickness is considerably less than under fully flooded conditions. These parts must operate correctly, often over prolonged periods with sufficient performance. One of the most important parameters determining the performance and life of machine parts is a lubrication film thickness, which is generated within elastohydrodynamic lubricated (EHL) non-conformal contacts. The film thickness in this regime is often time dependent and its value is governed by lubricant supply. If loss outstrips supply this leads to very thin films, which can no longer fulfill their role of separating the surfaces, and thus component failure can result. To achieve optimum bearing performance and component life, it is obviously desirable to be able to predict when starvation will occur. Today the film thickness and pressure in EHL can be predicted using numerical models also in the case of starvation. Although it is very essential to solve the starved EHL problems very little work aimed at comparing experiment and theory has been done. Especially in the case where the starved lubrication model requires as input the inlet layer thickness. This is crucial if the validity of numerical models is to be properly established. This paper is focused on the study of starved lubrication conditions on lubrication film formation. A new optical test rig with multiple EHL contacts was developed for experimental study of lubrication film formation.

Study of Lubrication Film Formation in Ball Bearings Under Starved Conditions

2011 ◽  
Author(s):  
Petr Svoboda ◽  
Martin Vrbka ◽  
Petr Sperka ◽  
Ivan Krupka ◽  
Martin Hartl
Keyword(s):  
Film Thickness ◽  
Film Formation ◽  
Test Rig ◽  
Rolling Bearings ◽  
Lubrication Film ◽  
Entrainment Velocity ◽  
Optical Test ◽  
Rolling Elements ◽  
Machine Parts ◽  
Lubrication Conditions

Rolling elements (e.g. rolling bearings, gears, cams and followers, etc.) fall into the most frequently used and highly loaded machine parts in machinery industry. These parts must operate correctly, often over prolonged periods with sufficient performance. One of the most important parameters determining the performance and life of machine parts is a lubrication film thickness, which is generated within elastohydrodynamic lubricated (EHL) non-conformal contacts. The entrainment velocity and the lubricant viscosity have the main effect on the film thickness formation in the classic fluid film lubrication. In some engineering applications e.g. grease lubricated rolling bearings, the available lubricant is not enough to fill the gap between the two contact surfaces thereby a poor lubrication conditions occur. Insufficient supply of lubricant may result in starvation and consequently in lubrication film collapse. With decreasing amounts of lubricant, the inlet meniscus approaches the contact entrance and finally causes lubrication film breakdown because of contact starvation. This paper is focused on the study of effect of starved lubrication conditions on lubrication film formation of non-conformal contacts operated under pure rolling conditions. A new optical test rig with multiple EHL contacts was developed for experimental study of lubrication film formation in the thrust ball bearing. Nevertheless to start this research the first experiments will be performed using ball on disc optical test rig where EHL contact is realized only between one ball and disc.

Analysis of Tribological Performance of Piston Ring Lubrication

2011 ◽  
Author(s):  
Yibin Guo ◽  
Wanyou Li ◽  
Dequan Zou ◽  
Xiqun Lu ◽  
Tao He
Keyword(s):  
Film Thickness ◽  
Friction Force ◽  
Power Loss ◽  
Piston Ring ◽  
Design Parameters ◽  
Oil Film ◽  
Starved Lubrication ◽  
Piston Ring Lubrication ◽  
Cylinder Bore ◽  
Lubrication Conditions

In this paper a mixed lubrication model considering lubricant supply conditions on cylinder bore has been developed for the piston ring lubrication. The numerical procedures of both fully flooded and starved lubrication were included in the model. The lubrication equations and boundary conditions at the end of strokes were discussed in detail. The effects of piston ring design parameters, such as ring face profile and ring tension, on oil film thickness, friction force and power loss under fully flooded and starved lubrication conditions due to available lubricant supply on cylinder bore were studied. The simulation results show that the oil available in the inlet region of the oil film is important to the piston ring friction power loss. With different ring face crown heights and tensions, the changes of oil film thickness and friction force were apparent under fully flooded lubrication, but almost no changes were found under starved lubrication except at the end of a stroke. In addition, the oil film thickness and friction force were affected evidently by the ring face profile offsets under both fully flooded and starved lubrication conditions, and the offset towards the combustion chamber made a large contribution to forming thicker oil film during the expansion stroke. So under different lubricant supply conditions on the cylinder bore, the ring profile and tension need to be adjusted to reduce the friction and power loss. Moreover, the effects of lubricant viscosity, surface composite roughness, and engine operating speed on friction force and power loss were also discussed.

Study of Scale Effect in a Starved Elastohydrodynamically Lubricated Contact

2016 ◽  
Vol 821 ◽  
pp. 138-143
Author(s):  
Petr Svoboda ◽  
David Kostal ◽  
Ivan Křupka ◽  
Martin Hartl
Keyword(s):  
Film Thickness ◽  
Scale Effect ◽  
Thickness Measurement ◽  
Lubricant Film ◽  
Scale Model ◽  
Lubricant Film Thickness ◽  
Film Distribution ◽  
Multiple Contacts ◽  
Optical Test ◽  
Lubricated Contact

The article describes an experimental investigation of scale effect in a starved elastohydrodynamically lubricated contact on lubricant film thickness. Lubricant film thickness and its distribution is one of the most important parameters determining the performance and life of machine parts. Current experimental and numerical studies are mostly connected with oil lubrication. However, greases are used in more than 80 % of all rolling bearings where the starvation phenomenon occurs most frequently. The aim of this work is to compare two approaches to measuring film thickness of different greases. The use of multiple contacts optical test rig based on thin film colorimetric interferometry for film thickness measurement has enables to obtain film thickness of starved contact and the film distribution. The experimental observation of full-scale model of bearing will help to understand better the behavior of real bearing. The evaluation of the experiment was made by chromatic interferometry. This method is used to measure thin lubrication films.

Experimental Study on Lubrication Film Thickness Under Different Interface Wettabilities

2014 ◽  
Vol 54 (1) ◽  
pp. 81-88 ◽  
Author(s):  
F. Guo ◽  
S. Y. Yang ◽  
C. Ma ◽  
P. L. Wong
Keyword(s):  
Experimental Study ◽  
Film Thickness ◽  
Lubrication Film

Effect of Proteins on Film Formation in Bovine Serum Lubricated Contacts Under Rolling/Sliding Conditions

2012 ◽  
Author(s):  
Martin Vrbka ◽  
Tomas Navrat ◽  
Ivan Krupka ◽  
Martin Hartl ◽  
Jiri Gallo
Keyword(s):  
Film Thickness ◽  
Bovine Serum ◽  
High Speed ◽  
Film Formation ◽  
Research Work ◽  
Digital Camera ◽  
Protein Film ◽  
Lubricating Film ◽  
Ceramic Femoral Head ◽  
Optical Test

The aim of this study is to perform detail experimental mapping of the lubricating film thickness of bovine serum (BS) within the contact between an artificial metal or ceramic femoral head and a glass disc and analyze effect of proteins on the film formation under rolling/sliding conditions. The film thickness was studied experimentally using an optical test rig as a function of time under variety of constant mean speeds. Chromatic interferograms were recorded with a high-speed digital camera and evaluated with thin film colorimetric interferometry. Under pure rolling conditions it was observed that the central film thicknesses increased with time for all measurements. When the disc was slower than head then the measured central film thicknesses achieved values only about some few nanometres, whereas when the tests were realized with faster disc then measured central film thicknesses achieved significantly higher values. Distribution of the film thickness within the contact zone is not homogeneous and two different film thickness regions can be found; thicker protein film and thinner base film that both show specific behaviour over time. This study showed that protein formation plays an important role in the lubrication processes of artificial joints of the human. Due to challenging of this study the more complex research work is carried out at the present time.

Experimental study of ultrathin liquid lubrication film thickness at the molecular scale

1997 ◽  
Vol 211 (2) ◽  
pp. 139-150 ◽  
Author(s):  
H Matsuoka ◽  
T Kato
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Film Thickness ◽  
Solid Surface ◽  
Experimental Measurements ◽  
Dynamic Measurements ◽  
Lubrication Film ◽  
Solid Specimen ◽  
Molecular Scale ◽  
New Apparatus

Ultrathin liquid lubrication film thicknesses at the molecular scale are measured by a new apparatus developed by the authors. Mica is used as the solid specimen and octamethylcyclotetrasiloxane (OMCTS), cyclohexane and n-hexadecane are used as liquid specimens. From experimental measurements, discretization of the lubrication film thickness is observed when the thickness is less than about 10 times the molecular diameter of the intervening liquid. Analysis of experimental data shows that the discretization of the lubrication film thickness is due to the solvation force. Dynamic measurements show that the solvation force is almost the same as the non-sliding case and is independent of the sliding speed of the solid surface.

Experimental Study of Microtextured Surfaces Operating Under Thin-Film EHD Lubrication Conditions

2007 ◽  
Vol 129 (3) ◽  
pp. 502-508 ◽  
Author(s):  
I. Křupka ◽  
M. Hartl
Keyword(s):  
Thin Film ◽  
Film Thickness ◽  
Measurement Techniques ◽  
Surface Texturing ◽  
Thickness Reduction ◽  
Lubrication Film ◽  
Ehd Lubrication ◽  
Lubricated Contact ◽  
Microtextured Surfaces ◽  
Lubrication Conditions

The effect of microdents within thin elastohydrodynamics (EHD) contacts has been studied by two measurement techniques. Phase-shifting interferometry was used to obtain topography of microtextured surface and thin-film colorimetric interferometry provided detailed information about film thickness changes within a lubricated contact. The behavior of microdents has been observed for positive slide-to-roll ratios when the disk is moving faster than the microtextured ball. The depth of microdents has been found to play significant role as to the lubrication films efficiency. The presence of deep microdents within lubricated contact results in film thickness reduction downstream that can even cause lubrication film breakdown. As the depth of microdents is reduced, this effect diminishes and beneficial effect of microdents on film thickness formation has been observed. No such an effect of microdent depth on lubricant film shape has been observed in case of negative slide-to-roll conditions when microdents do not cause film thickness reduction regardless of their depths. Obtained results suggest that surface texturing using microdents of an appropriate depth could help to increase lubrication films capabilities.

scholarly journals Microstructure and Wear Behavior of Plasma-Sprayed TiO2–SiAlON Ceramic Coating

Coatings ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1268
Author(s):  
Yun Wang ◽  
Weichao Wan ◽  
Junhong Mao ◽  
Lihui Tian ◽  
Ruitao Li
Keyword(s):  
Ceramic Coating ◽  
Wear Behavior ◽  
Rutile Phase ◽  
Atmospheric Plasma ◽  
Tio2 Anatase ◽  
Sialon Ceramic ◽  
Mating Surface ◽  
Starved Lubrication ◽  
Plasma Sprayed ◽  
Lubrication Conditions

In this study, atmospheric plasma spray was employed to deposit TiO2–SiAlON ceramic coating on 316 stainless steel. The phases and microstructure of the ceramic coating were investigated. Additionally, comparative studies on the tribological performances of the substrate and the ceramic coating, under both dry and starved lubrication conditions, were carried out. The SiAlON phase was preserved, while partial TiO2 anatase was transformed to rutile phase. The wear rate of the coating was roughly 1/3 of that of the substrate under both conditions. The wear mechanisms of the ceramic coating were surface fracture and abrasive wear in both cases, and the coating under starved lubrication underwent less abrasion. The pores in the coating served as micro-reservoirs, forming an oil layer on the mating surface, and improving tribological properties during sliding.

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