Experimental and Numerical Investigation of Inlet Dimple in Point and Elliptical Contact Elastohydrodynamic Lubrication Films

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Xuefeng Wang ◽  
Rufu Hu ◽  
Mingjun Wang ◽  
Huanxin Yao
Keyword(s):  
Numerical Analysis ◽  
Numerical Investigation ◽  
Experimental Observation ◽  
Elastohydrodynamic Lubrication ◽  
High Load ◽  
Minor Axis ◽  
Point Contacts ◽  
Included Angle ◽  
Speed Range ◽  
Elliptical Contact

The experimental observation of the inlet dimple of the elastohydrodynamic lubrication (EHL) film was carried out in point and elliptical contacts, respectively, and then, the numerical analysis under point contacts was conducted. The inlet dimple appears and then moves upstream toward the inlet and finally disappears with the increase of the entrainment speed. In the meantime, the dimple depth increases at the beginning and then decreases. The high load leads to a wide entrainment speed range where dimple exists. The varying range of the entrainment speed corresponding to the dimple appearance is smaller at a smaller included angle between the minor axis of elliptical contact and the entrainment direction.

Isothermal Elastohydrodynamic Lubrication of Point Contacts: Part 1—Theoretical Formulation

1976 ◽  
Vol 98 (2) ◽  
pp. 223-228 ◽  
Author(s):  
B. J. Hamrock ◽  
D. Dowson
Keyword(s):  
Numerical Analysis ◽  
Entire Range ◽  
Reynolds Equation ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Uniform Pressure ◽  
Point Contacts ◽  
Elasticity Analysis ◽  
Simultaneous Solution ◽  
Theoretical Formulation

The analysis of an isothermal elastohydrodynamic lubrication (EHL) point contact was evaluated numerically. This required the simultaneous solution of the elasticity and Reynolds equations. In the elasticity analysis the contact zone is divided into equal rectangular areas and it is assumed that a uniform pressure is applied over each element. In the numerical analysis of the Reynolds’ equation a phi analysis where phi is equal to the pressure times the film thickness to the 3/2 power is used to help the relaxation process. The EHL point contact analysis is applicable for the entire range of elliptical parameters and is valid for any combination of rolling and sliding within the contact.

Pressure Increase in Elliptical Impact Elastohydrodynamic Lubrication Contacts With Longitudinal Asperities

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
M. Kaneta ◽  
F. Guo ◽  
J. Wang ◽  
I. Krupka ◽  
M. Hartl
Keyword(s):  
Numerical Analysis ◽  
Applied Load ◽  
Steel Plate ◽  
Elastohydrodynamic Lubrication ◽  
Major Axis ◽  
Minor Axis ◽  
Pressure Increase ◽  
Local Pressures ◽  
Ellipticity Ratio ◽  
Steel Body

The phenomena that occur when an elliptical steel body impacts a stationary steel plate with surface asperities are discussed through isothermal Newtonian numerical analysis using sinusoidal roughness. The ridges of the surface asperities produce large local pressures, especially at a large ellipticity ratio, when the surfaces are approaching each other under the applied load. The values of the local pressures are larger when the ridges are along the major axis than when the ridges are along the minor axis. Furthermore, as the loading speed increases, the pressure increases. As a result, the microgrooves are produced in the ridges and the horseshoe-shaped constrictions are formed at the ridges located around the contact edge.

scholarly journals A thermal resistances-based approach for thermal-elastohydrodynamic calculations in point contacts

2017 ◽  
Vol 232 (11) ◽  
pp. 2088-2102 ◽  
Author(s):  
Eduardo de la Guerra Ochoa ◽  
Javier Echávarri Otero ◽  
Enrique Chacón Tanarro ◽  
Benito del Río López
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Thermal Effects ◽  
Good Accuracy ◽  
Computational Cost ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Point Contacts ◽  
New Approach ◽  
Ball On Disc

This article presents a thermal resistances-based approach for solving the thermal-elastohydrodynamic lubrication problem in point contact, taking the lubricant rheology into account. The friction coefficient in the contact is estimated, along with the distribution of both film thickness and temperature. A commercial tribometer is used in order to measure the friction coefficient at a ball-on-disc point contact lubricated with a polyalphaolefin base. These data and other experimental results available in the bibliography are compared to those obtained by using the proposed methodology, and thermal effects are analysed. The new approach shows good accuracy for predicting the friction coefficient and requires less computational cost than full thermal-elastohydrodynamic simulations.

Effects of out-of-contact lubricant channeling on friction and film thickness in starved elastohydrodynamic lubrication point contacts

2016 ◽  
Vol 231 (4) ◽  
pp. 432-440 ◽  
Author(s):  
Fadi Ali ◽  
Ivan Křupka ◽  
Martin Hartl
Keyword(s):  
Film Thickness ◽  
Digital Camera ◽  
Elastohydrodynamic Lubrication ◽  
Contact Condition ◽  
Friction Reduction ◽  
Rolling Element Bearings ◽  
Point Contacts ◽  
Practical Applications ◽  
Rolling Element ◽  
Ball On Disc

This study presents experimental results on the effect of out-of-contact lubricant channeling on the tribological performance of nonconformal contacts under starved lubrication. Channeling of lubricant was carried out by adding a slider with a limited slot for scraping the displaced lubricant on one of mating surfaces (ball). Thus, the scraped lubricant is forced to flow back into the depleted track through the limited slot resulting in robust replenishment. The measurements have been conducted using optical tribometer (ball-on-disc) equipped with a digital camera and torque sensor. The effect of lubricant channeling was compared to the original contact condition by means of measuring friction and film thickness. The results show that the out-of-contact lubricant channeling leads to a significant enhancement of film thickness and friction reduction under starved conditions. Indeed, the starved elastohydrodynamic lubrication contacts transformed to the fully flooded regime after introducing the flow reconditioning. Moreover, the film thickness decay over time, which is common with starved elastohydrodynamic lubrication contacts, has not been observed in the case of lubricant channeling. However, the beneficial effect of lubricant channeling diminishes as the original contact condition tends to the fully flooded regime. The results of this study can be easily implemented in practical applications such as radial and thrust rolling-element bearings.

Theoretical and experimental studies of the oil film in lubricated point contact

1966 ◽  
Vol 291 (1427) ◽  
pp. 520-536 ◽  
Keyword(s):  
Surface Layer ◽  
Film Thickness ◽  
Strong Evidence ◽  
Experimental Studies ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Experimental Results ◽  
Point Contacts ◽  
Previous Theory ◽  
Oil Film

A technique using Newton’s rings for mapping the oil film of lubricated point contacts is described. A theoretical value for the film thickness of such contacts in elastohydrodynamic lubrication is derived. The experimental results give the exit constriction predicted by previous theory but never shown in detail. The comparison of theoretical and experimental oil film thicknesses, which is satisfactorily accurate, gives strong evidence for a viscous surface layer some 1000Å thick. This film agrees with the known ‘lubricating power’ of the various oils tested.

scholarly journals Silencing of glycolysis in muscle: experimental observation and numerical analysis

2010 ◽  
Vol 95 (2) ◽  
pp. 380-397 ◽  
Author(s):  
Joep P. J. Schmitz ◽  
Natal A. W. Van Riel ◽  
Klaas Nicolay ◽  
Peter A. J. Hilbers ◽  
Jeroen A. L. Jeneson
Keyword(s):  
Numerical Analysis ◽  
Experimental Observation

Micro-Elastohydrodynamic Lubrication and its Relationship with Running-in

1986 ◽  
Vol 200 (6) ◽  
pp. 415-424 ◽  
Author(s):  
K P Baglin
Keyword(s):  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
High Load ◽  
The Way ◽  
Pressure Ripples

The paper determines the conditions under which sinusoidal asperities with a circumferential lay become elastically deformed by hydrodynamic pressure ripples within an elastohydrodynamic conjunction. The information is presented on a non-dimensional plot and it is found that such micro-elastohydrodynamic lubrication (micro-EHL) occurs at relatively low loads and/or with thin macroelastohydrodynamic films. Consideration is given to the way in which the plot may be extended to deal with real surfaces. Its use is demonstrated by the presentation of the lubrication histories of two scuffing tests, one of which ‘ran-in’ prior to failure. It is shown that the test which ‘ran-in’ operated throughout under micro-EHL conditions; in contrast, the second test, which started at a high load and with a thick EHL film, failed practically as soon as there was nominal contact between the surfaces. It is suggested that micro-EHL is a necessary prerequisite for ‘running-in’ and a mechanism is outlined.

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