Asperity contact theories: Do they predict linearity between contact area and load?

2008 ◽  
Vol 56 (8) ◽  
pp. 2555-2572 ◽  
Author(s):  
G. Carbone ◽  
F. Bottiglione
Keyword(s):  
Contact Area ◽  
Asperity Contact

Comparative Contact Analysis Study of Finite Element Method Based Deterministic, Simplified Multi-Asperity and Modified Statistical Contact Models

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
A. Megalingam ◽  
M. M. Mayuram
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Rough Surface ◽  
Contact Area ◽  
Model Analysis ◽  
Contact Model ◽  
Contact Load ◽  
Asperity Contact ◽  
Single Asperity ◽  
Contact Models

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.

Time dependent static friction force of agar gel-on-glass plate immersed in water

2002 ◽  
Vol 12 (9) ◽  
pp. 319-320
Author(s):  
T. Nitta ◽  
H. Haga ◽  
K. Kawabata
Keyword(s):  
Friction Force ◽  
Waiting Time ◽  
Contact Area ◽  
Glass Plate ◽  
Static Friction ◽  
Time Dependent ◽  
Asperity Contact ◽  
Contact Duration ◽  
Agar Gel ◽  
Static Friction Force

We measured the static friction force of agar gel-on-glass plate in water. The static friction force is independent of the apparent contact area between the agar gel and the glass plate. It increases with waiting time, that is, contact duration prior to motion. The static friction force is represented well by a power law of waiting time. The waiting time dependence is different from those of solid-on-solid systems. These results are discussed, based on asperity contact model.

A complete elastic-plastic spherical asperity contact model with the effect of isotropic strain hardening

2020 ◽  
pp. 135065012092989 ◽  
Author(s):  
A Megalingam ◽  
KS Hanumanth Ramji
Keyword(s):  
Strain Hardening ◽  
Rough Surface ◽  
Contact Area ◽  
Poisson’S Ratio ◽  
Combined Effect ◽  
Contact Model ◽  
Poisson's Ratio ◽  
Contact Load ◽  
Asperity Contact ◽  
Strain Hardening Rate

Understanding the deformation behavior of rough surface contacts is essential to minimise the tribological consequences of contacts. Mostly, statistical, deterministic and fractal approaches are adopted to explore the contact of rough surfaces. In statistical approach, a single asperity contact model is developed and extended to the whole surface. In the present work, a deformable spherical asperity contact with a rigid flat is modeled and analysed by accounting the combined effect of Young’s modulus, Poisson’s ratio, yield strength and isotropic strain hardening rate using finite element method. The results reveal that the elastic, elastoplastic and plastic contact states are highly influenced by E/Y ratio and strain hardening rate followed by Poisson’s ratio. The dimensionless contact radius is an inadequate parameter to explore the combined effect of material properties. For all E/Y ratio and Poisson’s ratio, as the strain hardening rate increases, the dimensionless contact area decreases for the same dimensionless contact load at elastoplastic and fully plastic contact states. As the strain hardening rate increases, the fully plastic contact state is reached at low dimensionless interference compared to elastic perfectly plastic materials for all E/Y ratio and Poisson’s ratio. For a common elastic-plastic material, empirical relations are developed to calculate the contact load and contact area appropriately with E/Y ratio, Poisson’s ratio and interference ratio as input variables. It can be utilised to study the interaction of rough surface contacts for most of the practical materials.

Elastic-Plastic Microcontact Analysis of a Sphere and a Flat Plate

2007 ◽  
Vol 23 (4) ◽  
pp. 341-352 ◽  
Author(s):  
J. L. Liou ◽  
J. F. Lin
Keyword(s):  
Surface Roughness ◽  
Flat Plate ◽  
Contact Pressure ◽  
Contact Area ◽  
Normal Load ◽  
Contact Load ◽  
Asperity Contact ◽  
Elastic Plastic ◽  
Deformation Regime ◽  
Maximum Contact

ABSTRACTThe elastic-plastic microcontact model of a sphere in contact with a flat plate is developed in the present study to investigate the effect of surface roughness on the total contact area and contact load. From the study done by the finite element method, the dimensionless asperity contact area, average contact pressure, and contact load in the elastoplastic regime are assumed to be a power form as a function of dimensionless interference (δ/δec). The coefficients and exponents of the power form expressions can be determined by the boundary conditions set at the two ends of the elastoplastic deformation regime. The contact pressures evaluated by the present model are compared with those predicted by the Hertz theory, without considering the surface roughness and the reported model, including the roughness effect, but only manipulating in the elastic regime. The area of non-zero contact pressure is enlarged if the surface roughness is considered in the microcontact behavior. The maximum contact pressure is lowered by the presence of surface roughness if the contact load is fixed. Under a normal load, both the contact pressure and the contact area are elevated by raising the plasticity index for the surface of the same surface roughness.

scholarly journals A Finite Element-Based Elastic-Plastic Model for the Contact of Rough Surfaces

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Finite Element ◽  
Contact Force ◽  
Contact Area ◽  
Rough Surfaces ◽  
Constitutive Relations ◽  
Element Model ◽  
Tangential Component ◽  
Asperity Contact ◽  
Elastic Plastic ◽  
Force Components

Three-dimensional elastic-plastic contact of two nominally flat rough surfaces is considered. Equations governing the shoulder-shoulder contact of asperities are derived based on the asperity constitutive relations from a finite element model of the elastic-plastic interaction proposed by Kogut and Etsion (2002), in which asperity scale constitutive relations are derived using piecewise approximate functions. An analytical fusion technique is developed to combine the piecewise asperity level constitutive relations. Shoulder-shoulder asperity contact yields a slanted contact force consisting of two components, one in the normal direction and a half-plane tangential component. Statistical summation of the asperity level contact force components and asperity level contact area results in the total contact force and total contact area formulae between two rough surfaces. Approximate equations are developed in closed form for contact force components and contact area.

A Mixed-Lubrication Study of Journal Bearing Conformal Contacts

1997 ◽  
Vol 119 (3) ◽  
pp. 456-461 ◽  
Author(s):  
Qian (Jane) Wang ◽  
Fanghui Shi ◽  
Si C. Lee
Keyword(s):  
Film Thickness ◽  
Contact Pressure ◽  
Contact Area ◽  
Numerical Solutions ◽  
Mixed Lubrication ◽  
Lubricant Film ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Lubricant Film Thickness ◽  
Asperity Contacts

Numerical analyses of finite journal bearings operating with large eccentricity ratios were conducted to better understand the mixed lubrication phenomena in conformal contacts. The average Reynolds equation derived by Patir and Cheng was utilized in the lubrication analysis. The influence function, calculated numerically using the finite element method, was employed to compute the bearing deformation. The effects of bearing surface roughness were incorporated in the present analysis for the calculations of the asperity contact pressure and the asperity contact area. The numerical solutions of the hydrodynamic and asperity contact pressures, lubricant film thickness, and asperity contact area were evaluated based on a simulated bearing-journal geometry. The calculations revealed that the asperity contact pressure may vary significantly along both the width and the circumferential directions. It was also shown that the asperity contacts and the lubricant film thickness were strongly dependent on the bearing width, asperity orientation, and operating conditions.

Contact Mechanics Analysis of a Rubber Piece on a Smooth Plate

2009 ◽  
Author(s):  
Kyosuke Ono
Keyword(s):  
Contact Mechanics ◽  
Elastic Deformation ◽  
Contact Area ◽  
Large Scale ◽  
Glass Plate ◽  
Applied Pressure ◽  
Small Scale ◽  
Asperity Contact ◽  
The Real ◽  
Parameter Values

In order to elucidate contact and friction characteristics of rubbers, numerical analysis of asperity contact mechanics of a rubber piece with a smooth glass plate was carried out on the basis of an asperity contact model that considers van der Waal’s (vdW) pressure. First, by ignoring vdW pressure and the elastic deformation of the mean height surface, asperity contact characteristics were analyzed using the measured Young’s modulus, and surface parameter values that could yield the measured contact area were estimated. Next, asperity contact characteristics were analyzed by considering the vdW pressure and elastic deformation of a rough sphere that is a model of a large-scale asperity having small-scale asperities. It was found that the actual contact area was similar to the measured contact area; this result could not be obtained without assuming an rms asperity height of ∼0.1 μm for the small-scale asperities. It was also found that the friction coefficient decreased with an increase in the applied pressure in the cases where the friction force is proportional to the real area of contact and to the real internal contact pressure.

A Deterministic Conformal/Counterformal Microcontact Model

1994 ◽  
Vol 116 (4) ◽  
pp. 833-840 ◽  
Author(s):  
V. Aronov ◽  
S. Nair ◽  
J. M. Wang
Keyword(s):  
Contact Area ◽  
Critical Analysis ◽  
Input Data ◽  
Friction And Wear ◽  
Real Contact Area ◽  
Contact Radius ◽  
Asperity Contact ◽  
Real Contact ◽  
Surface Statistics ◽  
Contact Parameters

Microcontact models, describing contact of two rough surfaces, are fundamental for the modeling of friction and wear. This paper presents a critical analysis of existing models and discusses their limitations. A new deterministic microcontact model based on conformal/counterformal contact of asperities, as opposed to the combined surface statistics and counterformal asperity contact, is presented. Based on this model, a computer program has been developed. The input data are the digitized 3-D topographies, separately measured from the two contacting surfaces. The program first determines the original mating position and then calculates the surface contact parameters: contact radius, contact pressure, real contact area and the number of elastic, plastic, conformal, and counterformal contacts.

The Impact of Diamond Conditioning on Surface Contact in CMP Pads

2007 ◽  
Vol 991 ◽  
Author(s):  
Carolina L Elmufdi ◽  
Gregory P. Muldowney
Keyword(s):  
Contact Area ◽  
Treatment Time ◽  
Removal Rate ◽  
Fundamental Property ◽  
Asperity Contact ◽  
Contact Points ◽  
The Mean ◽  
Pad Wear ◽  
The Impact ◽  
Total Contact Area

ABSTRACTTotal contact area between a CMP pad and wafer has emerged as a fundamental property that is directly linked to both removal rate and defectivity. Contact area has been shown to depend on surface morphology as it results from pad microstructure and material properties. Pads exhibiting higher contact area, hence imparting lower point stresses to the wafer, are effective in reducing CMP-related defects. The present study quantifies pad-wafer contact characteristics for both hard and soft porous polyurethane pads as a function of the extent of diamond conditioning. An Instron microtester is used to impart controlled quasi-static pad compression against a sapphire cover slip mounted on a Zeiss confocal microscope. Images collected through the microscope at discrete compressive states are analyzed off-line to quantify the total contact area and the size, shape, and distribution of individual contacts. A relationship is then established between these contact measures and the extent of conditioning. Conditioning decreases the mean asperity contact size as expected, but the evolution of contact regions shows non-intuitive features. In particular, total contact area passes through a minimum within the typical conditioning time of commercial CMP processes, then gradually increases. Clustered contact regions observed at short conditioning times spread out to a more uniform lateral spacing at longer conditioning times. These findings are accounted for by considering the texture subdivision achieved by individual diamonds together with bridging by the conditioning disk of higher regions on an unlevel pad surface. Textures produced by different conditioners on the same pad are quantified in terms of total contact area and number and uniformity of contact points. Formation of an ideal texture of abundant, well-spaced and level asperities is expedited by both conditioner type and treatment time. The results illustrate that evolution of pad contact area under compression is an essential measure for understanding polishing metrics such as wafer removal rate, defect count, and pad wear, and indicate clear direction for next-generation pad microstructures to achieve low-stress planarization.

Real-Time Observation of the Evolution of Contact Area Under Boundary Lubrication in Sliding Contact

2001 ◽  
Vol 124 (2) ◽  
pp. 229-238 ◽  
Author(s):  
Sy-Wei Lo ◽  
Sheng-Da Tsai
Keyword(s):  
Shear Stress ◽  
Contact Area ◽  
Normal Load ◽  
Sliding Contact ◽  
Observation System ◽  
In Situ Observation ◽  
Asperity Contact ◽  
Initial State ◽  
Time Observation ◽  
Sliding Distance

To study the evolution of asperity contact in the sliding contact, a new in situ observation system of sheet metal surface is built up. The workpiece is stationary so that the continuous deformation of a specific group of asperities can be traced. In the case of no strain rate in the substrate of workpiece, the experiments for various materials, roughness patterns, sliding velocities, and normal loads all show that the fractional contact area will increase from its initial state of pure flattening without shear stress, to a saturated value with sliding distance in different rates. The sliding velocity has minor influence on the variation of contact area for same sliding distance. The maximum increasing rate of the contact area is found in the case of medium load. In most cases, the increase in contact area takes place with simultaneously decreasing shear stress and pressure on the flattened asperity peak. The development of adhesive wear can be clearly observed in the case of high normal load and long sliding distance.

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