A Dynamic Wear Model for Micro-Grooved Water-Lubricated Bearings Under Transient Mixed Lubrication Condition

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Guo Xiang ◽  
Yanfeng Han ◽  
Tao He ◽  
Jiaxu Wang ◽  
Ke Xiao
Keyword(s):  
Friction Coefficient ◽  
Sliding Wear ◽  
Boundary Friction ◽  
Radial Clearance ◽  
Asperity Contact ◽  
Wear Coefficient ◽  
Wear Model ◽  
Surface Parameters ◽  
Simulation Results ◽  
Dynamic Wear

Abstract The study presents a dynamic wear model for micro-grooved water-lubricated bearings considering the transient mixed elastohydrodynamic lubrication (mixed-EHL) condition. In the established model, the modified Archard wear model and the mixed-EHL model are bridged to study the transient interdependent relationship between the sliding wear behavior and the mixed-EHL performance. In order to consider the effect of the transient mixed-EHL performance on the sliding wear, the Archard model is extended to include the time-varying wear coefficient based on the fatigue concept. To verify the presented model, the comparisons with the experimental results available in the literatures have been conducted. In this study, the evolution of the wear and mixed-EHL performance distribution over time is predicted, and the impact of the radial clearance, boundary friction coefficient, and surface parameters on the numerical predictions is evaluated. The simulation results reveal that the worn region moves toward the rotational direction slowly. The simulation results also reveal that the wear rate and the wear coefficient first decrease considerably, and then decrease gently, and the sliding wear geometry promotes the hydrodynamic effects and reduces the asperity contact during the operation. Furthermore, the parametric study demonstrates that dynamic wear and mixed-EHL performance is sensitive to the radial clearance, boundary friction coefficient, and surface parameters.

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.

An Adhesive Wear Model of Fractal Surfaces in Normal Contact

2008 ◽  
Author(s):  
X. Yin ◽  
K. Komvopoulos
Keyword(s):  
Interfacial Adhesion ◽  
Adhesive Wear ◽  
Adhesion Force ◽  
Plastic Material ◽  
Normal Load ◽  
Asperity Contact ◽  
Wear Coefficient ◽  
Wear Model ◽  
Normal Contact ◽  
Fractal Surfaces

A generalized adhesive wear model was derived for three-dimensional fractal surfaces in normal contact. A criterion for wear particle formation was derived based on the critical asperity contact area for fully plastic asperity deformation, taking into account the contribution of the adhesion force to the total normal load applied at the contact interface. The analysis yields a relationship of the adhesive wear coefficient in terms of total normal load (global interference), fractal parameters, elastic-plastic material properties, surface energies, material compatibility, and interfacial adhesion characteristics of the contacting rough surfaces. Numerical results of the wear coefficient of representative engineering material systems illustrate the roles of global interference and interfacial adhesion conditions (lubrication effect) in adhesive wear of surfaces in normal contact.

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.

A new asperity interaction model considering transient flash temperature and inhomogeneous distribution of oil viscosity

2016 ◽  
Vol 231 (3) ◽  
pp. 347-356
Author(s):  
Jun Liu ◽  
Zhinan Zhang ◽  
Bo Zhao ◽  
Youbai Xie
Keyword(s):  
Friction Coefficient ◽  
Boundary Lubrication ◽  
Interaction Model ◽  
Asperity Contact ◽  
Inhomogeneous Distribution ◽  
Sliding Velocity ◽  
Flash Temperature ◽  
Oil Viscosity ◽  
Temperature Characteristics ◽  
Simulation Results

A momentary contact of asperities will generate transient flash temperature phenomena in boundary lubrication. According to the viscosity–temperature characteristics of lubricant, the inhomogeneous distribution of temperature during the process of asperity contact would cause the inhomogeneous distribution of oil viscosity. This paper proposes a coupled Eulerian–Lagrangian based approach to analyze the influence of inhomogeneous distribution of viscosity on the friction coefficient of an asperity junction. The asperity interaction in boundary lubrication with different sliding velocities and different degrees of overlap of the undeformed surfaces were taken into account. Simulation results showed that the friction coefficient is proportional to the overlap and inversely proportional to sliding velocity. The results also showed that the influence of inhomogeneous distribution of oil viscosity on friction coefficient in boundary lubrication is limited.

Prediction of Steady State Adhesive Wear in Spur Gears Using the EHL Load Sharing Concept

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
S. Akbarzadeh ◽  
M. M. Khonsari
Keyword(s):  
Steady State ◽  
Wear Rate ◽  
Thermal Effects ◽  
Sliding Wear ◽  
Adhesive Wear ◽  
Load Sharing ◽  
Spur Gears ◽  
Wear Model ◽  
Wear Calculation ◽  
Simulation Results

The concept of load sharing between asperities and fluid film is applied in conjunction with lubricated sliding wear formulation proposed by Wu and Cheng (1991, “A Sliding Wear Model for Partial-EHL Contacts,” ASME J. Tribol., 113, pp. 134–141; 1993, “Sliding Wear Calculation in Spur Gears,” ASME J. Tribol., 115, pp. 493–500) to predict the steady state adhesive wear in gears. Thermal effects are included using a simplified thermoelastohydrodynamic analysis. The prediction of the model is verified by comparing simulation results with published experimental data pertinent to steady state wear rate. The main advantages of this method are the accuracy and the remarkable computational efficiency. The results of parametric simulation study are presented to investigate the effect of speed and surface roughness on a portion of load carried by asperities and wear rate.

scholarly journals Boundary Friction of ZDDP Tribofilms

2020 ◽  
Vol 69 (1) ◽  
Author(s):  
Jie Zhang ◽  
Mao Ueda ◽  
Sophie Campen ◽  
Hugh Spikes
Keyword(s):  
Friction Coefficient ◽  
Group Structure ◽  
Boundary Friction ◽  
Considerable Proportion ◽  
Base Oil ◽  
Characteristic Boundary ◽  
Long Duration ◽  
Structure Boundary ◽  
Alkoxy Groups ◽  
20 Nm

AbstractThe frictional properties of ZDDP tribofilms at low entrainment speeds in boundary lubrication conditions have been studied in both rolling/sliding and pure sliding contacts. It has been found that the boundary friction coefficients of these tribofilms depend on the alkyl structure of the ZDDPs. For primary ZDDPs, those with linear alkyl chains give lower friction those with branched alkyl chain ZDDPs, and a cyclohexylmethyl-based ZDDP gives markedly higher friction than non-cyclic ones. Depending on alkyl structure, boundary friction coefficient in rolling-sliding conditions can range from 0.09 to 0.14. These differences persist over long duration tests lasting up to 120 h. For secondary ZDDPs, boundary friction appears to depend less strongly on alkyl structure and in rolling-sliding conditions stabilises at ca 0.115 for the three ZDDPs studied. Experiments in which the ZDDP-containing lubricant is changed after tribofilm formation by a different ZDDP solution or a base oil indicate that the characteristic friction of the initial ZDDP tribofilm is lost almost as soon as rubbing commences in the new lubricant. The boundary friction rapidly stabilises at the characteristic boundary friction of the replacement ZDDP, or in the case of base oil, a value of ca 0.115 which is believed to represent the shear strength of the bare polyphosphate surface. The single exception is when a solution containing a cyclohexylethyl-based ZDDP is replaced by base oil, where the boundary friction coefficient remains at the high value characteristic of this ZDDP despite the fact that rubbing in base oil removes about 20 nm of the tribofilm. XPS analysis of the residual tribofilm reveals that this originates from presence of a considerable proportion of C-O bonds at the exposed tribofilm surface, indicating that not all of the alkoxy groups are lost from the polyphosphate during tribofilm formation. Very slow speed rubbing tests at low temperature show that the ZDDP solutions give boundary friction values that vary with alkyl group structure in a similar fashion to rolling-sliding MTM tests. These variations in friction occur immediately on rubbing, before any measurable tribofilm can develop. This study suggest that ZDDPs control boundary friction by adsorbing on rubbing steel or tribofilm surfaces in a fashion similar to organic friction modifiers. However it is believed that, for primary ZDDPs, residual alkoxy groups still chemically bonded to the phosphorus atoms of newly-formed polyphosphate/phosphate tribofilm may also contribute to boundary friction. This understanding will contribute to the design of low friction, fuel efficient crankcase engine oils. Graphical Abstract

scholarly journals Simulation and Experimental Study on Wear of U-Shaped Rings of Power Connection Fittings under Strong Wind Environment

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 735
Author(s):  
Songchen Wang ◽  
Xianchen Yang ◽  
Xinmei Li ◽  
Cheng Chai ◽  
Gen Wang ◽  
...  
Keyword(s):  
Abrasive Wear ◽  
Adhesive Wear ◽  
Surface Hardness ◽  
Wear Depth ◽  
Strong Wind ◽  
Wear Model ◽  
Wind Environment ◽  
Simulation Results ◽  
Oxidation Wear ◽  
Good Agreement

The objective of this study was to investigate the wear characteristics of the U-shaped rings of power connection fittings, and to construct a wear failure prediction model of U-shaped rings in strong wind environments. First, the wear evolution and failure mechanism of U-shaped rings with different wear loads were studied by using a swinging wear tester. Then, based on the Archard wear model, the U-shaped ring wear was dynamically simulated in ABAQUS, via the Umeshmotion subroutine. The results indicated that the wear load has an important effect on the wear of the U-shaped ring. As the wear load increases, the surface hardness decreases, while plastic deformation layers increase. Furthermore, the wear mechanism transforms from adhesive wear, slight abrasive wear, and slight oxidation wear, to serious adhesive wear, abrasive wear, and oxidation wear with the increase of wear load. As plastic flow progresses, the dislocation density in ferrite increases, leading to dislocation plugs and cementite fractures. The simulation results of wear depth were in good agreement with the test value of, with an error of 1.56%.

Effect of shape/size and distribution of microgeometries of textures on tribo-performance of crankpin bearing

2021 ◽  
pp. 135065012110105
Author(s):  
Nguyen Van Liem ◽  
Wu Zhenpeng ◽  
Jiao Renqiang
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Contact Force ◽  
Distribution Density ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Combined Model ◽  
Obvious Effect ◽  
Area Density

The effect of the shape/size and distribution of microgeometries of textures on improving the tribo-performance of crankpin bearing is proposed. Based on a combined model of the slider-crank mechanism dynamic and hydrodynamic lubrication, the distribution density, area density, and shape of spherical textures, square-cylindrical textures, wedge-shaped textures, and a hybrid between spherical texture and square-cylindrical texture on the crankpin bearing's tribo-performance are investigated under different operating conditions of the engine. The tribological characteristic of the crankpin bearing is then evaluated via the indexes of the oil film pressure p, asperity contact force, friction force, and friction coefficient of the crankpin bearing. The research results show that the distribution density with n = 12 and m = 6, and area density with α = 30% of various microtextures have an obvious effect on ameliorating the crankpin bearings tribo-performance. Concurrently, at the mixed lubrication region, the shape of the square-cylindrical texture on improving the tribo-performance is better than the other shapes of the spherical texture, wedge-shaped texture, and spherical and square-cylindrical texture. Particularly, all the average values of the asperity contact force, friction force, and friction coefficient with a square-cylindrical texture are significantly reduced by 14.6%, 19.5%, and 34.5%, respectively, in comparison without microtextures. Therefore, the microtextures of the spherical texture applied on the bearing surface can contribute to enhance the durability and decrease the friction power loss of the engine.

The Influence of the Addition of Ti on the Mechanical Properties of W-S-Ti Coatings

2006 ◽  
Vol 514-516 ◽  
pp. 687-691 ◽  
Author(s):  
Manuel Evaristo ◽  
Ana Nossa ◽  
Albano Cavaleiro
Keyword(s):  
Mechanical Properties ◽  
Friction Coefficient ◽  
Tribological Performance ◽  
The Self ◽  
Wear Coefficient ◽  
Gradual Loss ◽  
Order Of Magnitude ◽  
Amorphous Structures ◽  
Ti Content ◽  
Ti Films

In this work, W-S-Ti films were deposited by r.f. magnetron sputtering, using simultaneously WS2 and Ti targets. The atomic percentage of Ti in the coating was varied from 0 at.% up to 28 at.%. No significant variations in the S/W ratio with the increase of Ti content were observed. The increasing Ti contents in the films led to a gradual loss of crystallinity. Coatings with contents greater than ≈ 16 at.% only presents a broad peak characteristic of amorphous structures. Alloying the films with Ti led to significant improvements in the hardness (from 0.3 to 8.9 GPa). Also, the adhesive critical load continuously grew with the increase of the Ti content in the films. The wear coefficient of the films dropped more than one order of magnitude with the increase of Ti content whereas the friction coefficient was kept fairly constant with just a small increase in relation to single W-S film. In conclusion, to have a good tribological performance, the addition of Ti to the films should be balanced in order that the increase of the mechanical properties does not lead to severe loss of the self-lubricant properties.

Predicting the wear coefficient and friction coefficient in dry point contact using continuum damage mechanics

2018 ◽  
Vol 233 (3) ◽  
pp. 447-455 ◽  
Author(s):  
Sahar Ghatrehsamani ◽  
Saleh Akbarzadeh
Keyword(s):  
Friction Coefficient ◽  
Damage Mechanics ◽  
Point Contact ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Wear Coefficient ◽  
Mechanics Model ◽  
Pin On Disk ◽  
Disk Test ◽  
The Continuum

Wear coefficient and friction coefficient are two of the key parameters in the performance of any tribo-system. The main purpose of the present research is to use continuum damage mechanics to predict wear coefficient. Thus, a contact model is utilized that can be used to obtain the friction coefficient between the contacting surfaces. By applying this model to the continuum damage mechanics model, the wear coefficient between dry surfaces is predicted. One of the advantages of using this model is that the wear coefficient can be numerically predicted unlike other methods which highly rely on experimental data. In order to verify the results predicted by this model, tests were performed using pin-on-disk test rig for several ST37 samples. The results indicated that the wear coefficient increases with increasing the friction coefficient.

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