A Numerical Analysis for Piston Skirts in Mixed Lubrication—Part I: Basic Modeling

This paper presents a mathematical model for piston skirts in mixed lubrication. It takes into account the effects of surface waviness, roughness, piston skirt surface profile, bulk elastic deformation and thermal distortion of both piston skirts and cylinder bore on piston motion, lubrication and friction. The corresponding computer program developed can be used to calculate the entire piston trajectory and the hydrodynamic and contact friction forces as functions of crank angle under engine running conditions. Complete distributions of the oil film thickness and elastic deformation as well as the hydrodynamic and contact pressures can also be given at any crank angle if needed. This paper is the second part of a series of two papers. The first part (Basic Modeling), presented earlier by Zhu et al. (1991), gave the basic formulation and some preliminary results without bulk deformation considerations. In the present part, the three-dimensional finite element method is used to calculate so-called influence coefficient matrices. These matrices are repeatedly used to compute bulk elastic deformations of piston skirts. Results for 12 different cases are presented, and discussions are given focusing on the influences of elastic and thermal deformations on piston motion, lubrication and friction. An attempt to compare the calculated friction with experimental data is made, and agreement appears good for the two available cases. The computer program presented should be a useful tool for piston design and development.

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Effects of using smart fluid in lubrication on skirt‐liner friction

Industrial Lubrication and Tribology ◽

10.1108/00368791211208697 ◽

2012 ◽

Vol 64 (2) ◽

pp. 90-97 ◽

Cited By ~ 1

Author(s):

S.H. Mahdavi ◽

S.H. Mansouri ◽

A. Kimiaeifar

Keyword(s):

Mathematical Model ◽

Power Loss ◽

Design Methodology ◽

Variable Viscosity ◽

Mixed Lubrication ◽

Contact Friction ◽

Friction Forces ◽

Content Type ◽

Piston Skirt ◽

First Time

PurposeThe purpose of this paper is to present, for the first time, a mathematical model for a piston skirt in mixed lubrication with respect to applying a smart fluid in lubrication. In this way, the smart fluid, as a lubricant with controlled variable viscosity, is proposed and applied to minimize the power loss in the interaction between liner and skirt.Design/methodology/approachBased on signal processing, the relationships between viscosity of lubricant and the friction loss, the hydrodynamic and contact friction force consequently are found, as part of an effective approach to acquire the function of variable viscosity.FindingsIt is shown that hydrodynamics and contact friction forces can be controlled and minimized by using the variable viscosity signal with the optimized viscosity signal technique.Originality/valueIn this paper, a mathematical model for a piston skirt in mixed lubrication with respect to applying a smart fluid in lubrication is presented for the first time.

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Effect of Thermal Distortion on Wear of Composites

Journal of Tribology ◽

10.1115/1.2831526 ◽

1995 ◽

Vol 117 (4) ◽

pp. 622-628 ◽

Cited By ~ 3

Author(s):

Shingo Obara ◽

Takahisa Kato

Keyword(s):

Elastic Deformation ◽

Composite Structure ◽

Frictional Heating ◽

Tetragonal Zirconia ◽

Surface Profile ◽

Normal Pressure ◽

Oxide Ceramic ◽

Thermal Distortion ◽

Test Results ◽

Worn Surface

The worn surface profile of a composite structure was experimentally and numerically investigated focusing on the effects of sliding conditions. Wear tests on composites made of an oxide ceramic and an amorphous metal against a tetragonal zirconia polycrystals-alumina were carried out under various mean contact pressures, P, and sliding velocities, V. The test results showed that the worn surface profiles of the composites changed with the PV value. A new numerical method for simulating the worn surface profile of a composite structure has been developed. The present method is based upon the assumption that the profile of a worn surface is changed by thermal distortion of the sliding bodies due to frictional heating and by elastic deformation due to normal pressure and friction traction. The calculated results were compared with the test results, and the comparison showed that the elastic deformation plays an important role in forming the worn surface profile and that the effect of thermal distortion becomes remarkable with an increase in PV values. The numerical results clarified the contribution of the thermal distortion to the change in the worn surface profile of the composite.

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Dynamical Modeling of Gear Transmission Considering Gearbox Casing

Volume 8: 30th Conference on Mechanical Vibration and Noise ◽

10.1115/detc2018-85656 ◽

2018 ◽

Author(s):

Yang Luo ◽

Natalie Baddour ◽

Ming Liang

Keyword(s):

Dynamic Models ◽

Signal Propagation ◽

Gear Transmission ◽

Gear System ◽

Dynamical Model ◽

Contact Friction ◽

Dynamical Response ◽

Dynamic Simulations ◽

Friction Forces ◽

Frequency Domains

Much research has been carried out to investigate the dynamical response of a gear system because of its importance on vibration feature analysis. It is well known that the gearbox casing is one of the most important components of the gear system and plays an important role in signal propagation. However, its effects have widely been neglected within the dynamic simulations and few dynamic models have considered the gearbox casing when modeling a gear transmission. This paper proposes a gear transmission dynamical model with the consideration of the effects of gearbox casing. The proposed dynamical model incorporates TVMS, a time-varying load sharing ratio, as well as dynamic tooth contact friction forces, friction moments and dynamic mesh damping coefficients. The proposed gear dynamical model is validated by comparison with responses obtained from experimental test rigs under different speed conditions. Comparisons indicate that the responses of the proposed dynamical model are consistent with experimental results, in both time and frequency domains under different rotation speeds.

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Hydrodynamic Lubrication and Wear in Wavy Contacting Face Seals

Journal of Lubrication Technology ◽

10.1115/1.3453120 ◽

1978 ◽

Vol 100 (1) ◽

pp. 81-90 ◽

Cited By ~ 9

Author(s):

A. O. Lebeck ◽

J. L. Teale ◽

R. E. Pierce

Keyword(s):

Surface Roughness ◽

Hydrodynamic Lubrication ◽

Surface Profile ◽

Operating Conditions ◽

Face Seal ◽

Hydrodynamic Load ◽

Surface Waviness ◽

Wear Rates ◽

Elastic Deflection ◽

Face Seals

A model of face seal lubrication is proposed and developed. Hydrodynamic lubrication for rough surfaces, surface waviness, asperity load support, elastic deflection, and wear are considered in the model. Predictions of the ratio of hydrodynamic load support to asperity load support are made for a face seal sealing a low viscosity liquid where some contact does occur and surface roughness is important. The hydrodynamic lubrication is caused by circumferential surface waviness on the seal faces. Waviness is caused by initial out of flatness or any of the various distortions that occur on seal ring faces in operation. The equilibrium solution to the problem yields one dimensional hydrodynamic and asperity pressure distributions, mean film thickness, elastic deflection, and friction for a given load on the seal faces. The solution is found numerically. It is shown that the fraction of hydrodynamic load support depends on many parameters including the waviness amplitude, number of waves around the seal, face width, ring stiffness, and most importantly, surface roughness. For the particular seal examined the fraction of load support would be small for the amount of waviness expected in this seal. However, if the surface roughness were lower, almost complete lift-off is possible. The results of the analysis show why the initial friction and wear rates in mechanical face seals may vary widely; the fraction of hydrodynamic load support depends on the roughness and waviness which are not necessarily controlled. Finally, it is shown how such initial waviness effects disappear as the surface profile is altered by wear. This may take a long or short time, depending on the initial amount of hydrodynamic load support, but unless complete liftoff is achieved under all operating conditions, the effects of initial waviness will vanish in time for steady state conditions. Practical implications are drawn for selecting some seal parameters to enhance initial hydrodynamic load support without causing significant leakage.

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

Journal of Tribology ◽

10.1115/1.4040979 ◽

2018 ◽

Vol 141 (1) ◽

Cited By ~ 5

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.

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Experimental Study on the Dynamic Performance of Water-Lubricated Rubber Bearings with Local Contact

Shock and Vibration ◽

10.1155/2018/6309727 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10 ◽

Cited By ~ 5

Author(s):

Wu Ouyang ◽

Xuebing Zhang ◽

Yong Jin ◽

Xiaoyang Yuan

Keyword(s):

Rotational Speed ◽

Dynamic Performance ◽

Water Film ◽

Mixed Lubrication ◽

Contact Friction ◽

Specific Pressure ◽

Test Rig ◽

Identification Method ◽

Bearing Stiffness ◽

Rubber Bearings

Accurate dynamic characteristic coefficients of water-lubricated rubber bearings are necessary to research vibration of ship propulsion system. Due to mixed lubrication state of water-lubricated rubber bearings, normal test rig and identification method are not applicable. This paper establishes a test rig to simulate shaft misalignment and proposes an identification method for water-lubricated rubber bearings, which utilizes rotor unbalanced motion to produce self-excited force rather than artificial excitation. Dynamic performance tests under different conditions are operated. The results show that when rotational speed is less than 700 r/min, even if specific pressure is 0.05 MPa, it is difficult to form complete water film for the rubber bearing which was investigated, and contact friction and collision of the shaft and bearing are frequent. In the mixed lubrication, water film, rubber, and contact jointly determine dynamic characteristics of water-lubricated rubber bearings. The contact condition has a significant effect on the bearing stiffness, and water film friction damping has a significant effect on bearing damping. As for the particular investigated bearing, when rotational speed is in the range of 400~700 r/min and specific pressure is in the range of 0.03~0.07 MPa, bearing stiffness is in the range of 5.6~10.06 N/μm and bearing damping is in the range of 1.25~2.02 Ns/μm.

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A Note on the Surface Profile of the Greenland Ice Sheet

Journal of Glaciology ◽

10.1017/s0022143000026903 ◽

1970 ◽

Vol 9 (55) ◽

pp. 150-153 ◽

Cited By ~ 6

Author(s):

K. Philberth ◽

B. Federer

Keyword(s):

Ice Sheet ◽

Surface Profile ◽

Greenland Ice Sheet ◽

Thermal Softening ◽

Outer Edge ◽

Bottom Temperature ◽

Constant Amount ◽

Maximum Increase ◽

Friction Forces ◽

Pressure Melting

AbstractThis paper deals with the influence on the surface profile of the Greenland ice sheet, of an accumulation which increases between the ice divide and the coast, and of the thermal softening of the lowermost layers. It is concluded that the form of the surface of the profile measured by E.G.I.G. can be described by Glen's law with the exponentn= 3.5. The assumption is made that the bottom differs everywhere from the pressure melting point by a constant amount. This assumption is dropped in the second part of the paper. On the basis of the measured surface profile it is shown that the maximum increase of the bottom temperature is a few degrees within a range of 300 km. In view of the increasing surface temperature and heat of friction towards the outer edge it is concluded that, relatively close to the ice divide, that ice at the bottom must be temperate. Therefore we concluded that friction forces are preventing the ice from slipping on the bedrocks.

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Piston Ring-Cylinder Bore Friction Modeling in Mixed Lubrication Regime: Part I—Analytical Results

Journal of Tribology ◽

10.1115/1.1286337 ◽

1999 ◽

Vol 123 (1) ◽

pp. 211-218 ◽

Cited By ~ 82

Author(s):

Ozgen Akalin ◽

Golam M. Newaz

Keyword(s):

Boundary Conditions ◽

Friction Force ◽

Piston Ring ◽

Cylinder Liner ◽

Surface Flow ◽

Mixed Lubrication ◽

Asperity Contact ◽

Friction Modeling ◽

Crank Angle ◽

Cylinder Bore

An axi-symmetric, hydrodynamic, mixed lubrication model has been developed using the averaged Reynolds equation and asperity contact approach in order to simulate frictional performance of piston ring and cylinder liner contact. The friction force between piston ring and cylinder bore is predicted considering rupture location, surface flow factors, surface roughness and metal-to-metal contact loading. A fully flooded inlet boundary condition and Reynolds boundary conditions for cavitation outlet zone are assumed. Reynolds boundary conditions have been modified for non-cavitation zones. The pressure distribution along the ring thickness and the lubricant film thickness are determined for each crank angle degree. Predicted friction force is presented for the first compression ring of a typical diesel engine as a function of crank angle position.

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Experimental Validation of a 2D Bristle Friction Force Model

ASME 2010 Dynamic Systems and Control Conference, Volume 2 ◽

10.1115/dscc2010-4031 ◽

2010 ◽

Author(s):

Steven Fillmore ◽

Jianxun Liang ◽

Ou Ma

Keyword(s):

Friction Model ◽

Contact Friction ◽

Force Model ◽

Tangential Plane ◽

Stick Slip ◽

Friction Forces ◽

Body Contact ◽

Point Of Interest ◽

Experimental Effort ◽

Sliding Regimes

This paper describes an experimental effort designed to validate a general 2D bristle contact friction model. The model extends the 1D integrated bristle friction model to a 2D space by allowing the “bristle spring” to not only stretch along the direction of the bristle displacement but also rotate due to the instantaneous direction change of the velocity or motion trend in the common tangential plane of the contacting surfaces involved at the point of interest. The model is capable of simulating frictional behaviour in both sliding and sticking regimes occurring in general 3D rigid-body contact. With such an extension, the resulting friction model can be readily used to compute 3D contact friction forces in both sticking and sliding regimes. Two experiments were designed and implemented to validate the new 2D bristle model. The experiments were able to passively produce common frictional phenomena such as sliding, sticking, and stick-slip.

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