Experimental Investigation of Lubrication Regimes of a Water-Lubricated Bearing in the Propulsion Train of a Marine Vessel

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Dov Avishai ◽  
Groper Morel
Keyword(s):  
Experimental Investigation ◽  
Friction Coefficient ◽  
Hydrodynamic Lubrication ◽  
Low Cost ◽  
Pollution Prevention ◽  
Elastohydrodynamic Lubrication ◽  
Sliding Bearings ◽  
Naval Vessel ◽  
Lubrication Regimes ◽  
Lubrication Regime

Abstract Sliding bearings, operating in a full hydrodynamic lubrication regime, exhibit a low friction coefficient and extended life. In recent years, with the increase in environmental awareness and pollution prevention, attention is being directed to oil spills, which pollute the environment. This is extremely prominent in ships and submarines whose propeller shafts are typically supported by oil-lubricated sliding bearings. To reduce pollution risk and also to obtain a simpler and low-cost maintenance system, the propeller shafts of numerous modern marine vessels are supported by water-lubricated bearings. An experimental investigation into the lubrication regime of a water-lubricated bearing in the propulsion train of a naval vessel is presented. A test rig was designed and built to allow testing of a scaled water-lubricated composite bearing supporting a naval vessel propeller shaft. Experimental results quantifying the effect of the rotational speed on the operating eccentricity, the friction coefficient, and the bearing’s lubrication regimes are presented. The experimentally obtained results are compared with an elastohydrodynamic lubrication (EHL) model solved by employing comsol multiphysics modeling software, and the differences are addressed. Finally, conclusions that may assist in better understanding the operation profile of the bearing and thus improving the vessel’s operability are presented.

The Role of Geometrical Parameters in the Lubrication of the Swiss Lever Escapement

2021 ◽  
Vol 88 (6) ◽  
Author(s):  
Alejandro Roda-Buch ◽  
Valentine A. M. Magnin ◽  
Sandra Guadalupe Maldonado ◽  
Stefano Mischler
Keyword(s):  
Hydrodynamic Lubrication ◽  
Contact Forces ◽  
Geometrical Parameters ◽  
Inverse Dynamic ◽  
Technical Parameters ◽  
Lubrication Regimes ◽  
Multibody Model ◽  
Lubrication Regime ◽  
The Coefficient Of Friction

Abstract The lubrication regimes of a contact pair escapement-ruby pallet of a Swiss lever escapement have been investigated combining the theory of fluid lubrication with a well-established kinematic and inverse dynamic multibody model. The kinematic analytical results have been confronted with experimental measurements. The developed model allows to easily obtain, for the three operating phases of the Swiss lever escapement, the relative speed and the contact forces and, by considering a hydrodynamic lubrication regime, the lubricant minimum film thickness and the coefficient of friction. The presented formulation allows to study the influence of crucial technical parameters in the Swiss lever escapement lubrication. The spout radii of curvature have been identified as the optimal parameters to control the lubrication regimes in the pallet/escapement contacts. In that sense, an interesting result is that the lubrication regime moves away from the boundary lubrication by increasing these radii.

The Statistical Application of a Thermal EHL Theory for Individual Asperity-Asperity Collisions to the Sliding Contact of Rough Surfaces

1975 ◽  
Vol 97 (2) ◽  
pp. 311-318 ◽  
Author(s):  
P. E. Fowles
Keyword(s):  
Friction Coefficient ◽  
Hydrodynamic Lubrication ◽  
Sliding Contact ◽  
Unit Load ◽  
Lubrication Regime ◽  
Statistical Application ◽  
Model Surfaces ◽  
Mixed Lubrication Regime ◽  
Thermal Ehl ◽  
20 Nm

The numerical results of a previously developed thermal EHL theory describing the collisions between idealized asperities are analyzed statistically to obtain macroscopic values of unit load, traction, and friction coefficient for two model surfaces in sliding contact under a range of conditions. It is shown that significant unit loads and tractions can be generated as a result of the microsopic EHL contacts alone. The variation of friction coefficient with load and sliding speed corresponds qualitatively with experiment in the mixed lubrication regime between boundary and hydrodynamic lubrication, but quantitatively the friction coefficients are two to three times too high. The results imply that the lubricant becomes non-Newtonian and/or exhibits a limiting shear strength in virtually all asperity interactions, even those in which the thickness of the intervening lubricant film is maintained in the 20-nm range.

scholarly journals Theoretical and Experimental Investigation on Friction in Lubricated Line Contacts with Different Materials and Textures in Presence of Wear

2016 ◽  
Vol 681 ◽  
pp. 142-154 ◽  
Author(s):  
Francesca Di Puccio ◽  
Enrico Ciulli
Keyword(s):  
Surface Roughness ◽  
Experimental Investigation ◽  
Friction Coefficient ◽  
Boundary Lubrication ◽  
Flat Surface ◽  
Surface Conditions ◽  
Lubrication Regimes ◽  
Line Contacts ◽  
Lubrication Conditions ◽  
Theoretical Procedure

An experimental investigation on the friction coefficient in line contacts under mixed and boundary lubrication regimes is described. Rectangular contacts between cylindrical specimens and the flat surface of discs of different material and surface roughness combinations were analyzed. Very low Stribeck numbers have been considered, resulting also in low dimensionless film thickness, so that the morphology of the surfaces and the material had a remarking role. In this work, the theoretical procedure for assessing the friction coefficient in the tested cases is described and compared to experimental results. Additionally, wear effects obtained in boundary lubrication conditions are shown. The surface conditions are put in relation with some particular trends of the friction coefficient obtained for certain combinations of materials and roughness.

A New Approach to Determine Lubrication Regimes of Piston-Ring Assemblies

1997 ◽  
Vol 119 (4) ◽  
pp. 808-816 ◽  
Author(s):  
Naeim A. Henein ◽  
Shengqiang Huang ◽  
Walter Bryzik
Keyword(s):  
Piston Ring ◽  
Hydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Spark Ignition Engine ◽  
Frictional Torque ◽  
New Approach ◽  
Lubrication Regimes ◽  
Lubrication Regime ◽  
Mixed Lubrication Regime ◽  
And Shifts

A new approach is developed to determine piston-ring assembly lubrication regimes from the instantaneous frictional torque measured for the whole engine. This is based on the variation of the friction coefficient with the duty parameter in the Stribeck diagram over the mixed and hydrodynamic lubrication regimes. The derived equation determines the lubrication regimes from the slope of the line in the Stribeck diagram. A single cylinder spark ignition engine was instrumented to determine the total instantaneous frictional torque of the engine. Experiments were conducted under different loads at a constant speed. Results show that the regime is mixed lubrication near the top dead center (TDC) and shifts to the hydrodynamic lubrication regime as the piston moves away from TDC. The extent of the mixed lubrication regime depends on engine load and speed.

Numerical Analysis of Laser-Textured Piston-Rings in the Hydrodynamic Lubrication Regime

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Gonzalo Brito Gadeschi ◽  
Katja Backhaus ◽  
Gunther Knoll
Keyword(s):  
Numerical Analysis ◽  
Friction Coefficient ◽  
Distribution Pattern ◽  
Surface Texture ◽  
Piston Ring ◽  
Hydrodynamic Lubrication ◽  
Piston Rings ◽  
Variable Curvature ◽  
Lubrication Regime ◽  
Optimal Surface

In this work, the performance of barrel-shaped laser-textured piston rings is numerically investigated. The surface texture, parameterized by the dimple density, dimple depth, and dimple distribution pattern, is optimized to minimize the friction coefficient for piston rings of variable curvature. We consider fully textured as well as partially textured piston rings with two different dimple distributions patterns: a central dimple distribution, and a distribution along the piston ring edges. Finally, the sensitivity of the optimal surface parameters to the piston ring curvature is assessed.

scholarly journals Identification of Local Lubrication Regimes on Textured Surfaces by 3D Roughness Curvature Radius

2014 ◽  
Vol 966-967 ◽  
pp. 120-125 ◽  
Author(s):  
Cédric Hubert ◽  
Krzysztof J. Kubiak ◽  
Maxence Bigerelle ◽  
Laurent Dubar
Keyword(s):  
Hydrodynamic Lubrication ◽  
Contact Boundary ◽  
Curvature Radius ◽  
Textured Surfaces ◽  
Lubrication Regimes ◽  
Lubrication Regime ◽  
Cross Section Area ◽  
Strip Drawing ◽  
Mixed Lubrication Regime ◽  
Tribological Contact

This paper proposes a new method of 3D roughness peaks curvature radius calculation and its application to tribological contact analysis as a characteristic signature of tribological contact. This method is introduced through the classical approach of calculation of radius of asperity in 2D. Actually, the proposed approach provides a generalization of Nowicki's method [], depending on horizontal lines intercepting the studied profile. Here, the basic idea consists in intercepting the rough surface by a horizontal plane and to calculate the cross section area without including “islands into islands”, i.e. the small peaks enclosed in bigger ones. Then, taking into account the maximal value of the height amplitude of the roughness included into this area, an appropriate algorithm is proposed, without requiring the classical hypothesis of derivability, which may be unstable when applied to engineering surfaces. This methodology is validated on simulated surfaces, and applied to engineering surfaces created experimentally, with a laboratory aluminium strip drawing process. The regions of the textured and lubricated specimens surface are analysed, and the results gives interesting prospects to qualitatively identify the local lubrication regimes: regions with high curvature radii correspond to severe contact (boundary/mixed lubrication regime) while regions with low curvature radii correspond to hydrodynamic lubrication regime.

Friction Reduction in Lubricated Rough Contacts: Numerical and Experimental Studies

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Zhiqiang Liu ◽  
Arup Gangopadhyay
Keyword(s):  
Friction Coefficient ◽  
Ambient Pressure ◽  
Classical Model ◽  
Experimental Studies ◽  
Elastohydrodynamic Lubrication ◽  
Contact Problems ◽  
Friction Reduction ◽  
Asperity Contact ◽  
Oil Viscosity ◽  
Lubrication Regimes

Combining the contact model of elastic-layered solid with the concept of asperity contact in elastohydrodynamic lubrication (EHL), a mixed-lubrication model is presented to predict friction coefficient over rough surfaces with/without an elastic-layered medium under entire lubrication regimes. Solution of contact problems for elastic-layered solids is presented based upon the classical model of Greenwood and Williamson (GW) in conjunction with Chen and Engel's analysis. The effects of the Young's modulus ratio of the layer to substrate and the thickness of the layer on the elastic real area of contact and contact load for a fixed dimensionless separation are studied using the proposed method, which is used for the asperities having contact with an elastic coating. Coefficient of friction with elastic-layered solids in boundary lubrication is calculated in terms of Rabinowicz's findings and elastic-layered solutions of Gupta and Walowit. The effect of rough contacts with an elastic layer on friction coefficient in lubrication regimes has been analyzed. Variations in plasticity index ψ significantly affect friction coefficients in boundary and mixed lubrications. For a large value of ψ, the degree of plastic contact exhibits a stronger dependence of the mean separation or film thickness than the roughness, and for a small value of ψ, the opposite result is true. The effect of governing parameters, such as inlet oil viscosity at ambient pressure, pressure–viscosity coefficient, combined surface roughness, and El/E2 on friction coefficient, has been investigated. Simulations are shown to be in good agreement with the experimental friction data.

The Influence of the Operating Conditions on the Lubrication Regimes of Ball Screws

2013 ◽  
Vol 371 ◽  
pp. 581-585
Author(s):  
George Constantin Puiu ◽  
Vasile Puiu
Keyword(s):  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Ball Screw ◽  
Minimum Thickness ◽  
Lubrication Regimes ◽  
Lubrication Regime ◽  
Ball Screw Drive ◽  
Ellipticity Parameter

In point contact related applications (ball bearings, ball-screws) the minimum and the central film thickness of lubricant have a particular importance. The literature presents various numerical solutions to determine these parameters in the case of elliptical contacts [1-4]. Most of them refer to the fully developed elastohydrodynamic lubrication regime (EHD). Hamrock [5] proposes four different lubrication regimes depending on the size and importance of two physical phenomena that occur in contact: elastic deformation of the bodies in contact under a given load and lubricant viscosity variation of contact pressure. These four lubrication regimes have specific relations for calculating the two parameters. Also, Hamrock [5] develops a methodology for identifying the lubrication regime in a point contact, depending on three dimensionless parameters: the ellipticity parameter; the viscosity parameter; the elasticity parameter. According to the viscosity and elasticity parameters, for each value of the ellipticity parameter a map of lubrication regimes can be built. These parameters are influenced by the materials and geometry of the bodies in contact and operating conditions. By using the methodology [5] a comprehensive analysis regarding the lubrication regimes in contacts between balls and races of a ball screw drive has been done. Thus, a complex program to draw lubrication regimes maps, starting from an imposed geometry and from given operating conditions, has been developed. The developed maps have revealed the different lubrication regimes that can occur in contacts between the balls and races on the screw and nut. It was also revealed, for a given type of screw, which are the load and speed limits that allow transition from an isoviscous-rigid regime of lubrication (IVR) / hydrodynamic (HD) to an elastohydrodynamic lubrication regime (EHD). For each lubrication regime, relations were used for calculating the appropriate minimum thickness of lubricant film, hence the major importance of accurate knowledge of lubrication regime.

Parametric Study of the Behavior of a Mechanical Face Seal Operating in Mixed and TEHD Lubrication Regimes

2012 ◽  
Author(s):  
André Parfait Nyemeck ◽  
Noël Brunetière ◽  
Bernard Tournerie
Keyword(s):  
Heat Transfer ◽  
Friction Coefficient ◽  
Mixed Lubrication ◽  
Operating Conditions ◽  
Fluid Viscosity ◽  
Face Seal ◽  
Lubrication Regimes ◽  
Lubrication Regime ◽  
Mechanical Face Seal ◽  
Mixed Lubrication Regime

In this paper, the behavior of a mechanical face seal is analyzed for different operating conditions and designs. For that, a theoretical model including a multiscale approach of the mixed lubrication regime, heat transfer and deformation of the seal rings is used. It has been possible to clearly identify the three different lubrication regimes of a mechanical seal: the mixed lubrication where the friction coefficient decreases, the rough hydrodynamic regime corresponding to an increasing friction and then the thermo-elasto-hydrodynamic (TEHD) regime for which the coefficient of friction is approximately constant. In this work, the influence of the fluid pressure, the seal roughness height, the balance ratio, the rings materials, the dry friction coefficient and viscosity are respectively examined. Generally speaking, the variation of these parameters affects the location of the optimum value of the friction coefficient in the mixed lubrication regime. In the TEHD regime, the temperature is mainly influenced by the materials and the fluid viscosity, which control the amplitude of deformation and heat transfer. A dimensionless parametric analysis has been carried out in order to perform an overall discussion of the results. It is shown that the mixed and rough hydrodynamic lubrication regimes are controlled by the modified duty parameter, while the TEHD regime is controlled by the sealing parameter.

The Response of Balls Undergoing Oscillatory Motion: Crossing From Boundary to Mixed Lubrication Regimes

1993 ◽  
Vol 115 (2) ◽  
pp. 261-266 ◽  
Author(s):  
M. R. Lovell ◽  
M. M. Khonsari ◽  
R. D. Marangoni
Keyword(s):  
Ball Bearing ◽  
Hysteresis Loops ◽  
Maximum Velocity ◽  
Elastohydrodynamic Lubrication ◽  
Rolling Friction ◽  
Friction Torque ◽  
Mixed Lubrication ◽  
Ball Bearings ◽  
Lubrication Regimes ◽  
Lubrication Regime

There are many applications where determining the response of a slowly oscillating ball bearing becomes crucial. Many instrument pointing mechanisms, in particular those used for aerospace applications, contain ball bearings which sinusoidally oscillate at very slow rates over small angles. Prediction of the frictional response of these bearings is essential to designers, as the friction torque which they develop is an important factor for controlling space instruments. The friction torque associated with the motion of sinusoidally oscillating ball bearings has been found to trace out hysteresis loops. These loops can be separated into two regions: the steady rolling region and the pre-rolling region. The steady rolling friction torque, Ts, characterizes the steady rolling region, while the rest slope, σ, characterizes the pre-rolling region. The speed of a ball bearing in sinusoidal motion varies from rest to a maximum velocity, changing velocity at instantaneous increments. It is found that while moving toward this maximum velocity, a bearing may cross from boundary to mixed lubrication regimes. As a result, the prediction and interpretation of σ and Ts in sinusoidal oscillating systems becomes more difficult than their counterparts in constant rate systems, which ordinarily operate in only one lubrication regime. To establish the velocity boundaries associated with the onset of different lubrication regimes, a series of experiments were conducted at a constant rotation rate. Starting at the ultra-low-speed of .01 deg/s, the angular velocity was gradually increased to 72 deg/s. In this velocity range, the balls traveled from boundary lubrication, crossing the mixed lubrication regime, into the elastohydrodynamic lubrication regime. Sinusoidal hysteresis curves were also generated experimentally and characterized. The rest slope and steady rolling friction torque were investigated in both rolling regions using two different lubricants.

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