Numerical Prediction of Surface Wear and Roughness Parameters During Running-In for Line Contacts Under Mixed Lubrication

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Yazhao Zhang ◽  
Alexander Kovalev ◽  
Noriyuki Hayashi ◽  
Kensuke Nishiura ◽  
Yonggang Meng
Keyword(s):  
Friction Coefficient ◽  
Contact Region ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Wear Particles ◽  
Wear Model ◽  
Wear Process ◽  
Line Contacts ◽  
Lubrication Condition ◽  
Initial Line

A stochastic model for predicting the evolutions of wear profile and surface height probability density function (PDF) of initial line contacts during running-in under mixed lubrication condition is presented. A numerical approach was developed on the basis of stochastic solution of mixed lubrication, which combined the Patir and Cheng's average flow model for calculation of the hydrodynamic pressure and the Kogut and Etsion's (KE) rough surface contact model for calculation of the asperity contact pressure. The total friction force was assumed to be the sum of the boundary friction at the contact asperities and the integration of viscous shear stress in the hydrodynamic region. The wear depth on the contact region was estimated according to the modified Archard's wear model using the asperity contact pressure. Sugimura's wear model was modified and used to link the wear particle size distribution and the variation of surface height PDF during wear. In the wear process, the variations of profile and surface height PDF of initial line contacts were calculated step by step in time, and the pressure distribution, friction coefficient, and wear rate were updated consequently. The effect of size distribution of wear particles on the wear process was numerically investigated, and the simulation results showed that the lubrication condition in which small wear particles are generated from the asperity contact region is beneficial to reduce friction coefficient and wear rate, and leads to a better steady mixed lubrication condition.

scholarly journals Friction and adhesive wear behavior caused by periodic impact in mixed-lubricated point contacts

2020 ◽  
Vol 12 (2) ◽  
pp. 168781402090166
Author(s):  
Xin Pei ◽  
Wei Pu ◽  
Jialong Yang ◽  
Ying Zhang
Keyword(s):  
Friction Coefficient ◽  
Adhesive Wear ◽  
Wear Behavior ◽  
Critical Role ◽  
Surface Velocity ◽  
Asperity Contact ◽  
Impact Action ◽  
Wear Process ◽  
Lubrication Condition ◽  
Functional Components

Periodic impact is a common phenomenon experienced by functional components. The mechanisms governing the adhesive wear growth caused by the periodic impact are not well understood, which limits the development of antiwear and lubricating behavior. In this work, the periodic impact action caused by rubbing surface velocity and contact load is studied in the sliding wear process under mixed lubrication condition. At each wear simulation circle, the material removal at each asperity contact location is evaluated and the surface topography is renewed correspondingly. The evolutions of friction and wear track are revealed during wear process. We find that the friction coefficient changes periodically caused by the periodic speed, and the wear rate increases almost linearly with either speed period or speed amplitude. The load impact results in an abrupt variation in friction coefficient, while it appears to be limited in adhesive wear state compared to speed, highlighting the critical role of velocity impact in wear formation.

Friction Characteristics with Pin-on-Disc Friction Test on Microstructured Surface Using Whirling Electrical Discharge Texturing

2014 ◽  
Vol 1017 ◽  
pp. 417-422
Author(s):  
Vitchuda Lertphokanont ◽  
Takayuki Sato ◽  
Masahiro Oi ◽  
Minoru Ota ◽  
Keishi Yamaguchi ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Electrical Discharge ◽  
Area Ratio ◽  
Mixed Lubrication ◽  
Optimal Conditions ◽  
Friction Test ◽  
Crater Diameter ◽  
Microstructured Surface ◽  
Pin On Disc ◽  
Lubrication Condition

A microstructured surface was created on a steel surface by whirling electrical discharge texturing (WEDT) since it was considered that the microstructures could act as lubricant reservoirs to assist the formation of a lubricating film, resulting in reduced friction. In this study, friction tests under engine oil were carried out over a range of loads and sliding speeds. In addition, the surface characteristics of the microstructured surface were also investigated to optimize the friction characteristics of the textured surface through pin-on-disc friction tests. It was found that under the mixed lubrication condition near the boundary condition, textured surfaces with texture-area ratio of approximately 6% and a mean crater diameter of 35 μm were considered as the optimal conditions for reducing the friction coefficient. However, a texture-area ratio of approximately 4% and a mean crater diameter of 35 μm were considered as the optimal conditions for reducing the friction coefficient under the mixed lubrication condition near the elastohydrodynamic lubrication condition. It was considered that when the normal load decreased, the lubrication region changed from the mixed lubrication condition to the hydrodynamic lubrication condition, which meant that the actual contact surface area decreased. The decrease in the actual contact surface area with decreasing texture-area ratio led to a reduction in the friction coefficient. Finally, it was clarified that the friction coefficient was reduced under the optimized conditions of the microstructured surface through a pin-on-disc friction test.

scholarly journals Friction coefficient in mixed lubrication: A simplified analytical approach for highly loaded non-conformal contacts

2017 ◽  
Vol 9 (7) ◽  
pp. 168781401770626 ◽  
Author(s):  
Javier Echávarri Otero ◽  
Eduardo de la Guerra Ochoa ◽  
Enrique Chacón Tanarro ◽  
Benito del Río López
Keyword(s):  
Friction Coefficient ◽  
Thermal Effects ◽  
Mixed Lubrication ◽  
Good Precision ◽  
Experimental Conditions ◽  
Lubrication Regime ◽  
Line Contacts ◽  
Mixed Lubrication Regime ◽  
Lubrication Conditions ◽  
Highly Loaded

This article presents an analytical model for predicting friction in mixed lubrication regime. The calculations consider load shared between roughness asperities and the lubricant film, as well as the appearance of thermal effects in the contact and the influence of the lubricant rheology. Tests using tribometers have been performed to measure the friction coefficient in non-conformal surfaces for both point and line contacts. This allows verifying the results of the model under a broad range of experimental conditions with an influence on the lubrication conditions. Reasonably good precision has been found in the results obtained, which combined with a simplicity of use confers the model a high practical utility for rough estimates of the friction coefficient under mixed lubrication.

Numerical Running-In Method for Modifying Cylindrical Roller Profile Under Mixed Lubrication of Finite Line Contacts

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Yazhao Zhang ◽  
Hui Cao ◽  
Alexander Kovalev ◽  
Yonggang Meng
Keyword(s):  
Contact Pressure ◽  
Hydrodynamic Pressure ◽  
Mixed Lubrication ◽  
Asperity Contact ◽  
Pressure Distributions ◽  
Line Contacts ◽  
Finite Line ◽  
Roller Profile ◽  
Rough Surface Contact ◽  
Cylindrical Roller

A numerical method for modifying cylindrical roller profile was proposed to smooth axial pressure distributions of finite line contacts under the mixed lubrication regime. The mixed lubrication model, in which the Reynolds equation modified by Patir and Cheng has been solved with implementing the rough surface contact model of Kogut and Etsion for the stochastic solution of hydrodynamic pressure and asperity-contact pressure, was established and it is validated by the comparison between simulation results and experiments. Some common roller profiles were carried into the mixed lubrication model and obvious increment of pressure appears near the roller ends or at the central contact area. A numerical running-in method was developed to smooth pressure shapes and the crown drop of roller profile was modified gradually implementing Archard's wear law, where a higher asperity-contact pressure leads to a larger crown drop on a roller profile. The results of the numerical running-in method indicated that pressure distributions of finite line contacts are uniform if the optimized roller profile is employed.

Effect of Liquid-Solid Lubricant on Mixed Lubrication in Line Contact

2011 ◽  
Vol 148-149 ◽  
pp. 778-784
Author(s):  
Rattapasakorn Sountaree ◽  
Panichakorn Jesda ◽  
Mongkolwongrojn Mongkol
Keyword(s):  
Friction Coefficient ◽  
Film Thickness ◽  
Solid Lubricant ◽  
Reynolds Equation ◽  
Contact Region ◽  
Mixed Lubrication ◽  
Line Contact ◽  
Load Carrying ◽  
Roughness Amplitude ◽  
Raphson Method

This paper presents the performance characteristics of two surfaces in line contact under isothermal mixed lubrication with non-Newtonian liquid–solid lubricant base on Power law viscosity model. The time dependent Reynolds equation, elastic equation and viscosity equation were formulated for compressible fluid. Newton-Raphson method and multigrid technique were implemented to obtain film thickness profiles, friction coefficient and load carrying in the contact region at various roughness amplitudes, applied loads, speeds and the concentration of solid lubricant. The simulation results showed that roughness amplitude has a significant effect on the film pressure, film thickness and surface contact pressure in the contact region. The film thickness decrease but friction coefficient and asperities load rapidly increases when surface roughness amplitude increases or surface speed decreases. When the concentration of solid lubricant increased, friction coefficient and asperities load decrease but traction and film thickness increase.

The comprehensive effect of surface texture and roughness under hydrodynamic and mixed lubrication conditions

2017 ◽  
Vol 231 (10) ◽  
pp. 1307-1319 ◽  
Author(s):  
Chenbo Ma ◽  
Yanjun Duan ◽  
Bo Yu ◽  
Jianjun Sun ◽  
Qiaoan Tu
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Hydrodynamic Lubrication ◽  
Diameter Ratio ◽  
Mixed Lubrication ◽  
Textured Surface ◽  
Texture Parameters ◽  
Lubrication Condition ◽  
Lubrication Conditions ◽  
Effect Of Surface

A theoretical study is carried out to investigate the comprehensive effect of the machined roughness and fabricated textures, by solving the average Reynolds equation coupled with a mass-conservative cavitation algorithm and taking into account asperity contact. We analyzed the influence of surface roughness, which is represented by the combined root-mean-square roughness σ and surface pattern parameter γ on the optimum texture parameters including the dimple depth-over-diameter ratio and area density under hydrodynamic and mixed lubrication conditions. The results show that the effect of surface roughness on load-carrying capacity can be ignored under hydrodynamic lubrication condition. Furthermore, the optimum texture parameters under hydrodynamic lubrication condition and the optimum dimple depth-over-diameter ratio under mixed lubrication condition are determined at minimized friction coefficient, which can be taken as the same for smooth-textured surface and rough-textured surface. The corresponding minimum friction coefficient increases with increasing σ and γ, and decreasing dimple area density under mixed lubrication condition.

A Sliding Wear Model for Partial-EHL Contacts

1991 ◽  
Vol 113 (1) ◽  
pp. 134-141 ◽  
Author(s):  
Shifeng Wu ◽  
H. S. Cheng
Keyword(s):  
Wear Rate ◽  
Wear Mechanism ◽  
Sliding Wear ◽  
Contact Region ◽  
Contact Temperature ◽  
Hertzian Contact ◽  
Asperity Contact ◽  
Wear Model ◽  
Actual Surface ◽  
Transitional Phenomenon

A sliding wear model has been developed for partial-EHL contacts, in which both the thermal desorption wear mechanism at low asperity contact temperature and the oxidative wear mechanism at elevated asperity contact temperature are considered. To include micro-EHL effects, digitized actual surface roughness profiles are used in simulating two contacting rough surfaces, and in obtaining the asperity contact area and asperity contact temperature distributions within a Hertzian contact region. Wear measurements in a two-disk machine configuration have been made over a comprehensive range of slide-to-roll ratios. The experimental results show a continuous decrease in wear rate with the increase in slide-to-roll ratio when the slide-to-roll ratio is relatively small, and a drastic rise in wear rate when slide-to-roll ratio is further increased. The experimental wear rate curve as a function of slide-to-roll ratio verifies the model prediction. The drastic rise in wear rate with the increase in slide-to-roll ratio in the range of slide-to-roll ratio beyond unity seems to suggest that a transitional phenomenon exists in the relation between wear rate and slide-to-roll ratio.

scholarly journals The influence of stick–slip transitions in mixed-friction predictions of heavily loaded cam–roller contacts

2018 ◽  
Vol 233 (5) ◽  
pp. 676-691 ◽  
Author(s):  
Shivam S Alakhramsing ◽  
Matthijn B de Rooij ◽  
Mark van Drogen ◽  
Dirk J Schipper
Keyword(s):  
Friction Coefficient ◽  
Rotational Velocity ◽  
Mixed Lubrication ◽  
Contact Forces ◽  
Contact Friction ◽  
Real Surface ◽  
Asperity Contact ◽  
Roughness Effects ◽  
Friction Mechanism ◽  
Stick Slip

A load-sharing-based mixed lubrication model, applicable to cam–roller contacts, is developed. Roller slippage is taken into account by means of a roller friction model. Roughness effects in the dry asperity contact component of the mixed lubrication model are taken into account by measuring the real surface topography. The proportion of normal and tangential load due to asperity interaction is obtained from a dry contact stick–slip solver. Lubrication conditions in a cam–roller follower unit, as part of the fuel injection equipment in a heavy-duty diesel engine, are analyzed. Main findings are that stick–slip transitions (or variable asperity contact friction coefficient) are of crucial importance in regions of the cam where the acting contact forces are very high. The contact forces are directly related to the sliding velocity/roller slippage at the cam–roller contact and thus also to the static friction mechanism of asperity interactions. Assuming a constant asperity contact friction coefficient (or assuming that gross sliding has already occurred) in highly loaded regions may lead to large overestimation in the minimal required cam–roller contact friction coefficient in order to keep the roller rolling. The importance of including stick–slip transitions into the mixed lubrication model for the cam–roller contact is amplified with decreasing cam rotational velocity.

Piston ring-cylinder liner tribology investigation in mixed lubrication regime: part I-correlation with bench experiment

2015 ◽  
Vol 67 (6) ◽  
pp. 520-530 ◽  
Author(s):  
Lin Ba ◽  
Zhenpeng He ◽  
Lingyan Guo ◽  
Young Chiang ◽  
Guichang Zhang ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Sudden Change ◽  
Mixed Lubrication ◽  
Friction Reduction ◽  
Asperity Contact ◽  
Film Rupture ◽  
Frictional Loss ◽  
Content Type ◽  
Oil Film ◽  
Ring Sample

Purpose – The purpose of this paper is to improve the environment and save energy, friction reduction, lower oil consumption and emissions demand that are the chief objectives of the automotive industry. The piston system is the largest frictional loss source, which accounts for about 40 per cent of the total frictional loss in engine. In this paper, the reciprocating tribometer, which is updated, was used to evaluate the friction and wear performances. Design/methodology/approach – An alternate method is introduced to investigate the effect of reciprocating speed, normal load, oil pump speed and ring sample and oil temperature on friction coefficient with the ring/liner of a typical inline diesel engine. The orthogonal experiment is designed to identify the factors that dominate wear behavior. To understand the correlations between friction coefficients and wear well, different friction coefficient results were compared and explained by oil film build-up and asperity contact theory, such as the friction coefficient over a long period and averaged the friction coefficient over one revolution. Findings – The friction coefficient changes little but fluctuates with a small amplitude in the stable stage. The sudden change of frequency, load and stroke will lead to the oil film rupture. The identification for the factors that dominates the wear loss is ranged as F (ring sample) > , E (oil sample) > , B (stroke) > , D (temperature) > , A (load) > , G (liner) > and C (frequency). Originality/value – This paper develops and verifies a methodology capable of mimicking the real engine behavior at boundary and mixed lubrication regimes which can minimize frictional losses, wear, reduce much work for the experiment and reduce the cost. The originality of the work is well qualified, as very few papers on a similar analysis have been published, such as: The friction coefficient values fluctuating in the whole stage may be caused by the vibration of the system; suddenly, boundary alternation may help the oil film to form the lubrication; and weight loss mainly comes from the contribution of the friction coefficient value fluctuation. The paper also found that the statistics can gain more information from less experiment time based on a design of experiment.

A New Deterministic Model for Mixed Lubricated Point Contact With High Accuracy

2020 ◽  
pp. 1-33
Author(s):  
Shuowen Zhang ◽  
Chenhui Zhang
Keyword(s):  
High Performance ◽  
Deterministic Model ◽  
Contact Region ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Mixed Lubrication ◽  
Stribeck Curve ◽  
Asperity Contact ◽  
Lubrication Regime ◽  
Pressure Boundary Condition

Abstract Mixed lubrication is a major lubrication regime in the presence of surface roughness. A deterministic model is established to solve mixed lubricated point contact in this paper, using a new method to solve asperity contact region in mixed lubrication. Treatment of pressure boundary condition between elastohydrodynamic lubrication region and asperity contact region is discussed. The new model is capable of calculating typical Stribeck curve and analyzing transition of lubrication regime, from full film lubrication to boundary lubrication. Moreover, final result of the model is independent of pressure initialization. High performance in accuracy and convergence has been achieved, which is of great importance for further lubrication modelling with consideration of nano-scale roughness, intermolecular and surface forces.

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