scholarly journals Two-Process Random Textures: Measurement, Characterization, Modeling and Tribological Impact: A Review

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 268
Author(s):  
Pawel Pawlus ◽  
Rafal Reizer ◽  
Wieslaw Żelasko
Keyword(s):  
Contact Mechanics ◽  
Functional Properties ◽  
Functional Significance ◽  
Measurement Errors ◽  
Friction And Wear ◽  
Hydrodynamic Lubrication ◽  
Asperity Contact ◽  
Future Challenges ◽  
Number Of Publications ◽  
And Behavior

Two-process random textures seem to present better functional properties than one-process surfaces. There are many random two-process textures. Plateau-honed cylinder surfaces are the most popular example. Two-process surfaces are also created during the initial periods of life of machined elements. However, knowledge about two-process textures measurement, modeling, and behavior is low. Two-process surfaces are very sensitive to measurement errors. It is very difficult to model them. Special methods of their characterization were created. Their functional significance was studied in a small number of publications. In this paper, measurement, characterization, and modeling of two-process textures were presented. The functional impact of them was analyzed, the effects on contact mechanics and friction and wear were mainly studied. Finally, considerations of future challenges were addressed. The nature of two-process random textures should be taken into account during analyses of properties of machined elements. The plateau part decides about the asperity contact, and the valley portion governs the hydrodynamic lubrication.

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.

scholarly journals Influence of the Lubrication Oil Temperature on the Disengaging Dynamic Characteristics of a Cu-Based Wet Multi-Disc Clutch

2021 ◽  
Vol 11 (23) ◽  
pp. 11299
Author(s):  
Liangjie Zheng ◽  
Biao Ma ◽  
Man Chen ◽  
Liang Yu ◽  
Qian Wang
Keyword(s):  
Dynamic Characteristics ◽  
Hydrodynamic Lubrication ◽  
Friction Pair ◽  
Automatic Transmission ◽  
Friction Torque ◽  
Asperity Contact ◽  
Uniformity Coefficient ◽  
Lubrication Oil ◽  
The Impact ◽  
First Time

Clutch disengaging dynamic characteristics, including the disengaging duration and the variations of friction pair gaps and friction torque, are crucial to the shifting control of an automatic transmission. In the present paper, the influence of lubrication oil (ATF) temperature on disengaging dynamic characteristics is investigated through a comprehensive numerical model for the clutch disengaging process, which considers the hydrodynamic lubrication, the asperity contact, the heat transfer, the spline resistance, and the impact between the piston and clutch hub. Moreover, the non-uniformity coefficient (NUC) is proposed to characterize the disengaging uniformity of friction pairs. As the ATF temperature increases from 60 °C to 140 °C, the clutch disengaging duration shortens remarkably (shortened by 55.1%); besides, the NUC sees a decreasing trend before a slight increase. When the ATF temperature is 80 °C, the distribution of friction pair gaps is most uniform. During the disengaging process, the increase of ATF temperature not only accelerates the change of the lubrication status between friction pairs but also contributes to the decrease of contact torque and hydrodynamic torque. This research demonstrates for the first time, evidence for clutch disengaging dynamic characteristics with the consideration of ATF temperature.

scholarly journals Analysis on micro-motion of cylinder block based on elasto-hydrodynamic lubrication

2019 ◽  
Vol 72 (5) ◽  
pp. 645-650 ◽  
Author(s):  
Jihai Jiang ◽  
Wei-Peng Yan ◽  
Ge-Qiang Li
Keyword(s):  
Numerical Model ◽  
Hydrodynamic Lubrication ◽  
Valve Plate ◽  
Cylinder Block ◽  
Asperity Contact ◽  
Plate Interface ◽  
Content Type ◽  
Micro Motion ◽  
Belt Width ◽  
Discharge Pressure

Purpose The purpose of this paper is to analyze the micro-motion of the cylinder block. Design/methodology/approach Based on the elasto-hydrodynamic lubrication, a numerical model for the cylinder block/valve plate interface is proposed, with consideration of the elastic deformations, the pressure-viscosity effect and asperity contacts. The influence-function method is applied to calculating the actual deformations of the cylinder block and the valve plate. The asperity contact model simplified from Greenwood assumption is introduced into the numerical model. Furthermore, the relationship between the micro-motion and the operating condition, the sealing belt width is discussed, respectively. Findings The results show an increase in the discharge pressure causes the tilt state and the vibrating motion getting worse, which can be eased by improving the rotational speed, the sealing belt width and the ratio of external and internal sealing belt width. Originality/value The proposed research can provide a theoretical reference for the optimizing design of cylinder block/valve plate pair.

Sustainable Mobility in Smart Cities

2020 ◽  
pp. 211-246 ◽  
Author(s):  
Annapaola Marconi ◽  
Enrica Loria
Keyword(s):  
Behavior Change ◽  
Smart Cities ◽  
Success Factor ◽  
Sustainable Mobility ◽  
On Demand ◽  
Future Challenges ◽  
User Centric ◽  
Sustainability Challenges ◽  
And Behavior ◽  
Key Success Factor

MaaS, with its user-centric vision aiming at more flexible, personalized, and on-demand mobility services, has a perspective to address the key sustainability challenges of the mobility of the future: transport solutions that are integrated, inclusive, and time-efficient, while containing the economic, social, and environmental costs. Civic engagement is a key success factor towards this objective: to fully embrace MaaS transformation, citizens need to feel part of the process. Gamification proved to be effective to raise citizens' awareness, encourage their participation, and promote a gradual but profound behavior change. These characteristics can be exploited by MaaS solutions to attract users and encourage the acceptance of tailored mobility plans. The chapter presents two successful cases of gamified systems aiming at promoting a more sustainable mobility, Play&Go and Kids Go Green; investigates the potential of gamified systems, in combination with MaaS solutions, in terms of citizens' engagement and behavior change; and discusses current limitations and future challenges.

Effects of double parabolic profiles with groove textures on the hydrodynamic lubrication performance of journal bearing under steady operating conditions

2020 ◽  
Vol 21 (3) ◽  
pp. 301
Author(s):  
Chongpei Liu ◽  
Wanyou Li ◽  
Xiqun Lu ◽  
Bin Zhao
Keyword(s):  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Operating Conditions ◽  
Lubricating Oil ◽  
Asperity Contact ◽  
Adiabatic Flow ◽  
Lubrication Performance ◽  
Load Carrying ◽  
Edge Wear ◽  
Journal Misalignment

The textures on the bushing surface have important effects on the performance of journal bearing. In this study, the effects of double parabolic profiles with groove textures on the hydrodynamic lubrication performance of journal bearing under steady operating conditions are investigated theoretically. The journal misalignment, asperity contact and thermal effects are considered, while the profile modifications due to running-in are neglected. The Winkler/Column model is used to calculate the elastic deformation of bushing surface and the adiabatic flow hypothesis is adopted to obtain the effective temperature of lubricating oil. The numerical solution is established by using finite difference and overrelaxation iterative methods, and the rupture zone of oil film is determined by Reynolds boundary conditions. The numerical results reveal that the double parabolic profiles with groove textures with proper location and geometric sizes can increase load carrying capacity and reduce friction loss under steady operating conditions, which effectively overcome the drawbacks of double parabolic profiles. This novel bushing profile may help to reduce the bushing edge wear and enhance the lubrication performance of journal bearing.

Contact Mechanics: Friction and Wear

1998 ◽  
pp. 323-367
Author(s):  
Dominique François ◽  
André Pineau ◽  
André Zaoui
Keyword(s):  
Contact Mechanics ◽  
Friction And Wear

Contact Mechanics of Rough Surfaces in Tribology: Single Asperity Contact

1996 ◽  
Vol 49 (5) ◽  
pp. 275-298 ◽  
Author(s):  
Bharat Bhushan
Keyword(s):  
Friction And Wear ◽  
Rough Surfaces ◽  
Asperity Contact ◽  
Elastic Solids ◽  
Elastic Plastic ◽  
Single Asperity ◽  
Real Area Of Contact ◽  
Single Asperity Contact ◽  
Indentation Problem ◽  
Real Area

Contact modeling of two rough surfaces under normal approach and with relative motion is carried out to predict the real area of contact which affects friction and wear of an interface. The contact of two macroscopically flat bodies with microroughness is reduced to the contact at multiple asperities of arbitrary shapes. Most of deformation at the asperity contact can be either elastic or elastic-plastic. In this paper, a comprehensive review of modeling of a single asperity contact or an indentation problem is presented. Contact analyses for a spherical asperity/indenter on homogeneous and layered, elastic and elastic-plastic solids with and without tangential loading are presented. The analyses reviewed in this paper fall into two groups: (a) analytical solutions, primarily for elastic solids and (b) finite element solutions, primarily for elastic-plastic problems and layered solids. Implications of these analyses in friction and wear are discussed.

A Molecular Model of Asperity Contact and Comparison to Continuum Based Models

2008 ◽  
Author(s):  
Wei Huang ◽  
Robert L. Jackson
Keyword(s):  
Contact Mechanics ◽  
Continuum Mechanics ◽  
Material Properties ◽  
Molecular Model ◽  
Small Scale ◽  
Elastic Contact ◽  
Asperity Contact ◽  
Molecular Forces ◽  
The Continuum

Surface asperities can range widely in size. Therefore it is important to characterize the effect of size and scale on the contact mechanics. This work presents a molecular model of asperity contact in order to characterize small scale asperity contact. The model is also compared to existing continuum mechanics based models developed originally by Hertz for elastic contact and later expanded by others to include plasticity. It appears that the predictions can be related to each other and that the continuum material properties can be related to the properties describing the molecular forces.

Celebrating Half a Century of Environment and Behavior: A Bibliometric Review

2019 ◽  
Vol 51 (5) ◽  
pp. 469-501 ◽  
Author(s):  
Taciano L. Milfont ◽  
Keivan Amirbagheri ◽  
Elena Hermanns ◽  
José M. Merigó
Keyword(s):  
Web Of Science ◽  
Natural Environments ◽  
University Of Michigan ◽  
Scientific Impact ◽  
Environment And Behavior ◽  
Bibliometric Review ◽  
Number Of Publications ◽  
And Behavior ◽  
The University ◽  
The Impact

Environment and Behavior is a leading international journal that publishes research examining the relationships between human behavior and the built and natural environments since 1969. Motivated by its half-century anniversary, the present article uses the Web of Science Core Collection database to provide a bibliometric overview of the leading trends that have occurred in the journal during the 1969-2018 period. The impact of the journal has increased over the years, Gary W. Evans is the author with most published papers, articles by Paul C. Stern and Thomas Dietz have made a notable scientific impact, the University of Michigan is the institution with the highest number of publications, and there is a growing trend in the number of women and international contributors to the journal. This bibliographic review provides strong evidence of the scientific impact of the journal, and the wider Environment-and-Behavior community should be proud of its story of success.

scholarly journals A Method for Monitoring Lubrication Conditions of Journal Bearings in a Diesel Engine Based on Contact Potential

2020 ◽  
Vol 10 (15) ◽  
pp. 5199
Author(s):  
Biao Wan ◽  
Jianguo Yang ◽  
Sicong Sun
Keyword(s):  
Diesel Engine ◽  
Journal Bearing ◽  
Hydrodynamic Lubrication ◽  
Journal Bearings ◽  
Asperity Contact ◽  
Contact Potential ◽  
Axis Orbit ◽  
Lubrication Condition ◽  
The Relationship ◽  
Lubrication Conditions

Wear of the journal bearings in a diesel engine is usually caused by asperity contact. Increased contact potential is caused by the asperity contact between the journal bearing and the shell. This paper analyzes the relationship between the contact potential and asperity contact and presents a method based on contact potential to monitor the bearing wear caused by asperity contact. A thermo-elastic hydrodynamic lubrication (THL) model of the journal bearing on the test bench was established and was verified by measuring its axis orbit. The asperity contact proportion was calculated based on this THL model, and its relationship with the measured contact potential was determined. The main contribution of this paper is to present a new method for monitoring the lubrication conditions of journal bearings in a diesel engine based on contact potential. The results showed that (a) when the minimum oil film thickness was less than 5 μm, asperity contact occurred between the bearing shell and the journal, which led to a sharp increase in contact pressure and a rapid increase in friction power consumption. Further, (b) there was a positive correlation between contact potential and asperity contact. The contact potential was greater than 0.75 mv when asperity contact occurred. These results proved that asperity contact could be accurately monitored using the contact potential, and the feasibility of using the contact potential to monitor the lubrication condition of a bearing was verified.

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