scholarly journals Prediction of oil-film thickness and shape in elliptical point contacts under combined rolling and sliding motion

2000 ◽  
Vol 214 (5) ◽  
pp. 427-437 ◽  
Author(s):  
D Jalali-Vahid ◽  
H Rahnejat ◽  
R Gohar ◽  
Z. M. Jin
Keyword(s):  
Point Contact ◽  
Rolling Element Bearings ◽  
Point Contacts ◽  
Practical Applications ◽  
Sliding Motion ◽  
Numerical Predictions ◽  
Local Point ◽  
Rolling Element ◽  
Raphson Method

The paper presents a numerical solution for elliptical point contact conjunctions under combined rolling and sliding motion. This condition is prevalent in many practical applications, such as rolling element bearings and conformal gears. An effective influence Newton-Raphson method is employed in local point distributed or global line distributed low-relaxation iterations. This method enables determination of the pressure distribution and film shape at high loads such as are encountered in many practical applications. Some of the numerical predictions have been validated against experimental results.

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.

scholarly journals Transient Analysis of Isothermal Elastohydrodynamic Point Contacts under Complex Kinematics of Combined Rolling, Spinning and Normal Approach

Lubricants ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 81
Author(s):  
Gajarajan Sivayogan ◽  
Ramin Rahmani ◽  
Homer Rahnejat
Keyword(s):  
Critical Role ◽  
Point Contact ◽  
Squeeze Film ◽  
Point Contacts ◽  
Historical Sources ◽  
Transient Conditions ◽  
Sliding Motion ◽  
Numerical Predictions ◽  
Contact Kinematics

This paper presents a brief review of elastohydrodynamic analysis in commemoration of the immense contributions of Duncan Dowson. This paper also presents an elastohydrodynamic analysis of the elliptical point contact problem under steady state as well as transient conditions. The overall methodology is validated against numerical predictions and experimental observations of acknowledged historical sources. The validated methodology is used to make original contributions in the elastohydrodynamics of elliptical point contact subjected to complex combined contact kinematics, including rolling/sliding, mutual convergence and separation (squeeze film motion) of contacting pairs, when subjected to reciprocating and spinning motions. This combined complex contact kinematics under transient conditions has not hitherto been reported in the literature. This paper shows the critical role of squeeze film motion upon lubricant film thickness. The results also show that the influence of spin motion is only significant at fairly high values of angular velocity and in the absence of a rolling/sliding motion.

Early Detection of Fatigue Damage on Rolling Element Bearings Using Adapted Wavelet

2007 ◽  
Vol 129 (4) ◽  
pp. 495-506 ◽  
Author(s):  
Xavier Chiementin ◽  
Fabrice Bolaers ◽  
Jean-Paul Dron
Keyword(s):  
Wavelet Transform ◽  
Time Scale ◽  
Degrees Of Freedom ◽  
Ball Bearings ◽  
Rolling Element Bearings ◽  
Mechanical Shock ◽  
Vibratory Analysis ◽  
Rolling Element ◽  
Shock Response

Among the advanced techniques of the predictive maintenance, the vibratory analysis proves to be very effective, in particular, for monitoring rotating components such as the bearings. Their damage creates cyclic efforts which are at the origin of the processing of vibratory measurements. This processing can be made by temporal methods, frequential methods, or by time-scale methods using the wavelets for 2 decades. The wavelet transform is a very effective processing, however, the difficulties of application and interpretation of the results slow down their employment. The determination of the parameters of the wavelets makes its use all the more difficult. Moreover, the use of these time-scale methods is very expensive in time computation. This paper proposes a wavelet adapted to the mechanical shock response of a structure with n degrees of freedom. In addition, we developed a procedure for analysis of signals by this wavelet which makes it possible to accelerate the process and to improve detection in the case of disturbed signals. This methodology is compared with the traditional time-scale methods and is implemented to detect defects of different sizes on outer rings and inner rings of ball bearings.

THEORY OF POINT CONTACT SPECTRA FOR SYSTEM METAL TIP-SUPERCONDUCTOR WITH INTERNAL JOSEPHSON JUNCTION

1989 ◽  
Vol 03 (10) ◽  
pp. 789-794 ◽  
Author(s):  
M. KUPKA ◽  
O. HUDÁK
Keyword(s):  
Josephson Junction ◽  
Energy Gap ◽  
Point Contact ◽  
Model System ◽  
Point Contacts ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
Metal Tip ◽  
Contact Metal

We report on the calculations of current-voltage characteristics and dynamical resistivity for a model system (series connected point contact metal — superconductor and Josephson junction of the S-N-S type) as a function of applied voltage. Calculated shape of dV/dI as a function of V shows some qualitative agreement with measured curves on real low-resistivity point contacts of the type metal tip – ceramic superconductor (LaBaCuO, YBaCuO). Method for determination of the energy gap is proposed.

Power Loss Predictions in Geared Transmissions Using Thermal Networks-Applications to a Six-Speed Manual Gearbox

2005 ◽  
Vol 128 (3) ◽  
pp. 618-625 ◽  
Author(s):  
C. Changenet ◽  
X. Oviedo-Marlot ◽  
P. Velex
Keyword(s):  
Power Loss ◽  
Rolling Element Bearings ◽  
Power Losses ◽  
Uniform Temperature ◽  
Manual Gearbox ◽  
Transient Conditions ◽  
Numerical Predictions ◽  
Rolling Element ◽  
Power Inputs ◽  
Lumped Elements

A model is presented which makes it possible to predict power losses in a six-speed manual gearbox. The following sources of dissipation, i.e., power inputs in the model, are considered: (i) tooth friction; (ii) rolling element bearings; (iii) oil shearing in the synchronizers and at the shaft-free pinion interfaces; and (iv) oil churning. Based upon the first principle of Thermodynamics for transient conditions, the entire gearbox is divided into lumped elements with a uniform temperature connected by thermal resistances which account for conduction, convection, and radiation. The numerical predictions compare favorably with the efficiency measurements from the actual gearbox at different speeds and torques. The results also reveal that, at lower temperatures (about 40°C), power loss estimations cannot be disassociated from the accurate prediction of temperature distributions.

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