A single asperity sliding contact model for molecularly thin lubricant

The study of the contact stresses generated when two surfaces are in contact plays a significant role in understanding the tribology of contact pairs. Most of the present contact models are based on the statistical treatment of the single asperity contact model. For a clear understanding about the elastic-plastic behavior of two rough surfaces in contact, comparative study involving the deterministic contact model, simplified multi-asperity contact model, and modified statistical model are undertaken. In deterministic contact model analysis, a three dimensional deformable rough surface pressed against a rigid flat surface is carried out using the finite element method in steps. A simplified multi-asperity contact model is developed using actual summit radii deduced from the rough surface, applying single asperity contact model results. The resultant contact parameters like contact load, contact area, and contact pressure are compared. The asperity interaction noticed in the deterministic contact model analysis leads to wide disparity in the results. Observing the elastic-plastic transition of the summits and the sharing of contact load and contact area among the summits, modifications are employed in single asperity statistical contact model approaches in the form of a correction factor arising from asperity interaction to reduce the variations. Consequently, the modified statistical contact model and simplified multi-asperity contact model based on actual summit radius results show improved agreement with the deterministic contact model results.

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A Complete Single Asperity-Based Statistical Gaussian Rough Surface Contact Model

Journal of Bio- and Tribo-Corrosion ◽

10.1007/s40735-020-00426-y ◽

2020 ◽

Vol 6 (4) ◽

Author(s):

A. Megalingam ◽

K. S. Hanumanth Ramji

Keyword(s):

Rough Surface ◽

Contact Model ◽

Single Asperity ◽

Surface Contact ◽

Rough Surface Contact

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Elastic Contact Model Accounting for Both Asperity and Substrate Compliance With Application to Patterned Media

ASME/STLE 2007 International Joint Tribology Conference, Parts A and B ◽

10.1115/ijtc2007-44503 ◽

2007 ◽

Author(s):

Chang-Dong Yeo ◽

Andreas A. Polycarpou

Keyword(s):

Bulk Material ◽

Contact Stiffness ◽

Contact Model ◽

Elastic Contact ◽

Element Analysis ◽

Patterned Media ◽

Single Asperity ◽

Proposed Model ◽

Stiffness Model ◽

Bulk Substrate

An improved elastic contact stiffness model for a single asperity system is proposed to account for the effects of both bulk substrate and asperity deformations between two contacting surfaces. Depending upon the applied load, as well as the geometrical and physical properties of the asperity and bulk material, the bulk substrate can have a considerable contribution to the overall contact stiffness. Finite element analysis is performed to verify the proposed analytical model. The single asperity model is extended to rough surfaces in contact. The contact stiffness values from the proposed model are compared to those from the GW model. The proposed contact model can be directly relevant to analyze the contact behavior of modern patterned media.

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Friction Heat Due to Sliding of Rough Surfaces: Micro-Scale Interactions and Their Macro-Scale Effect

Volume 10: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B, and C ◽

10.1115/imece2008-68844 ◽

2008 ◽

Author(s):

K. Farhang ◽

A. Elhomani

Keyword(s):

Closed Form ◽

Heat Generation ◽

Rough Surfaces ◽

Integral Form ◽

Sliding Contact ◽

Heat Generation Rate ◽

Friction Heat ◽

Single Asperity ◽

Macro Scale ◽

Statistical Integral

When two rough surfaces are in sliding contact an asperity on a surface would experience intermittent temperature flashes as it comes in momentary contact with asperities on a second surface. The frequency of the flash temperatures, their strength and duration depend, in addition to the sliding speed, on the topology of the two surfaces. In this paper a model is developed for the work-heat relation with a consideration of the above-mentioned intermittent nature of contact. The work of friction on one asperity is derived in integral form and closed-form equations. The rate of generation of heat is found due to a single asperity. Using the statistical account of asperity friction heat generation, rate of heat generation between two rough surfaces is obtained both in statistical integral form and in the approximate closed form.

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Deterministic Contact Model of a Rough Surface Against a Flat-Layered Surface

ASME/STLE 2004 International Joint Tribology Conference, Parts A and B ◽

10.1115/trib2004-64014 ◽

2004 ◽

Cited By ~ 1

Author(s):

H. R. Pasaribu ◽

D. J. Schipper

Keyword(s):

Mechanical Properties ◽

Rough Surface ◽

Contact Area ◽

Indentation Depth ◽

Normal Load ◽

Contact Model ◽

Real Contact Area ◽

Single Asperity ◽

Real Contact ◽

Effective Mechanical Properties

The effective mechanical properties of a layered surface vary as a function of indentation depth and the values of these properties range between the value of the layer itself and of the substrate. In this paper, a layered surface is modelled like a solid that has effective mechanical properties as a function of indentation depth by assuming that the layer is perfectly bounded to the substrate. The normal load as a function of indentation depth of sphere pressed against a flat layered surface is calculated using this model and is in agreement with the experimental results published by El-Sherbiney (1975), El-Shafei et al. (1983), Tang & Arnell (1999) and Michler & Blank (2001). A deterministic contact model of a rough surface against a flat layered surface is developed by representing a rough surface as an array of spherically shaped asperities with different radii and heights (not necessarily Gaussian distributed). Once the data of radius and height of every single asperity is obtained, one can calculate the number of asperities in contact, the real contact area and the load carried by the asperities as a function of the separation.

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Insights into dynamic sliding contacts from conductive atomic force microscopy

Nanoscale Advances ◽

10.1039/d0na00414f ◽

2020 ◽

Vol 2 (9) ◽

pp. 4117-4124

Author(s):

Nicholas Chan ◽

Mohammad R. Vazirisereshk ◽

Ashlie Martini ◽

Philip Egberts

Keyword(s):

Electrical Conductivity ◽

Atomic Force Microscopy ◽

Sliding Contact ◽

Current Transport ◽

Conductive Atomic Force Microscopy ◽

Sliding Contacts ◽

Force Microscopy ◽

Single Asperity ◽

Atomic Force ◽

Sliding Dynamics

Measuring the electrical conductivity serves as a proxy for characterizing the nanoscale contact. In this work, the correlation between sliding dynamics and current transport at single asperity sliding contact is investigated.

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Modelling Transient Behavior of a Mechanical System Including a Rolling and Sliding Contact

Tribology ◽

10.1115/imece2005-80906 ◽

2005 ◽

Cited By ~ 2

Author(s):

Anders So¨derberg ◽

Christer Spiegelberg

Keyword(s):

Contact Stiffness ◽

Transient Behavior ◽

Measurement Procedure ◽

Sliding Contact ◽

Contact Model ◽

Test Equipment ◽

Main Concern ◽

Contact Conditions ◽

Machine Elements ◽

Precision Machines

The friction and wear of rolling and sliding contacts are critical factors for the operation of machine elements such as bearings, gears, and cam mechanisms. In precision machines, for example, the main concern is to compensate for frictional losses, so as to improve control accuracy. In other applications it is often desirable to minimize friction losses to improve efficiency, though sometimes high friction is desired to prevent sliding and wear. The aim of this study is to simulate the behavior of a test equipment and show that simulations can be used to study and optimize mechanical systems that include rolling and sliding contact. Simulations can be used to study the system as a whole, as well as the contact conditions. The test equipment and the measurement procedure used are described. In the simulations, a contact model designed to handle transient contact conditions is integrated into a system model. The results show that the contact strongly influences the system. The simulations show that the use of a contact model allows the simulation of systems that contain contacts with different amounts of slip, and that such simulations can be used to study the contact as well as the system. Surface roughness influences the contact stiffness and is included in the simulations.

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Scanning Probe Microscopy Measurements of Friction

MRS Bulletin ◽

10.1557/mrs2004.142 ◽

2004 ◽

Vol 29 (7) ◽

pp. 478-483 ◽

Cited By ~ 25

Author(s):

Scott S. Perry

Keyword(s):

Scanning Probe Microscopy ◽

Sliding Contact ◽

Scanning Probe ◽

Interfacial Friction ◽

Probe Microscopy ◽

Frictional Properties ◽

Single Asperity ◽

Friction Measurements ◽

Detection Schemes ◽

Tribological Contact

AbstractThis article describes the details of scanning probe microscopy measurements of interfacial friction from an experimental perspective. In such studies, the probe tip is taken as a model of a single asperity within a tribological contact, and interfacial forces are measured as a function of the sliding contact of the probe tip with the surface. With appropriate detection schemes, friction and load forces can be monitored simultaneously and used together to describe the frictional properties of the microscopic contact. This article provides a detailed description of the procedures and protocols of friction measurements performed with scanning probe microscopy, the relevant properties of probe tips, and the influence of environment on microscopic friction measurements. In addition, the article provides a brief overview of several categories of friction studies performed with scanning probe microscopy, highlighting the type of materials characterized in these studies as well as the importance and impact of the microscopic measurements.

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