A New Adaptive-Surface Elastic-Plastic Contact Model of Rough Surfaces: Parameter Correlations

2006 ◽  
Vol 532-533 ◽  
pp. 961-964
Author(s):  
Min Song
Keyword(s):  
Rough Surface ◽  
Root Mean Square ◽  
Rough Surfaces ◽  
Computing Time ◽  
Contact Model ◽  
Asperity Contact ◽  
Mean Square ◽  
Elastic Plastic ◽  
Surface Profiles

Based on an presented adaptive-surface elastic-plastic asperity contact model which can greatly decrease contact computing time and keep the precision loss less than 5%, a series of 2-D rough surface profiles with different roughness and correlative length are numerically generated to investigate how to select the threshold used in this model for different adaptive rough surfaces. The results show that well acceptable precision of the elastic-plastic contact calculation would be derived when the ratio of threshold to root mean square curvature, δ 1.0 10 6mm2 − < × .

On a model for the prediction of asperity interactions of the coated friction pair

2019 ◽  
Vol 72 (3) ◽  
pp. 449-454 ◽  
Author(s):  
Chunxing Gu ◽  
Shuwen Wang
Keyword(s):  
Optimum Design ◽  
Numerical Experiments ◽  
Rough Surfaces ◽  
Contact Model ◽  
Real Contact Area ◽  
Plastic Behavior ◽  
Asperity Contact ◽  
Content Type ◽  
Contact Behavior ◽  
Elastic Plastic

Purpose Surface coatings have been introduced on the contact surfaces to protect the mechanical parts for a long time. However, in terms of the optimum design of coatings, some key coating parameters are still selected by trial and error. The optimum design of coatings can be conducted by numerical experiments. This paper aims to predict the contact behavior of the coated rough surfaces accurately. One improved asperity contact model for the coated rough surfaces considering the misalignment of asperities would be developed. Design/methodology/approach Incorporating the coated asperity contact model into the improved Greenwood Tripp-based statistical approach, the proposed model can predict the elastic-plastic behaviors of the interacting coated asperities. Findings According to numerical experiments, compared with the coated asperity contact model in which an equivalent rough surface against a plane is assumed, the improved asperity contact model for the coated contacts can account for the effect of permitting misalignment of two rough surfaces. The contacts having the thicker, stiffer and harder coatings result in higher asperity contact pressure and smaller real contact area fraction under the given Stribeck oil film ratio. Originality/value In this paper, one statistical coated asperity contact model for two rough surfaces was developed. The developed model can consider the elastic-plastic behavior of interacting coated asperities. The effects of the coating thickness and its mechanical properties on the contact behavior of the rough surfaces with coatings can be evaluated based on the developed model.

A Two-Dimensional Adaptive Elasto-Plastic Contact Model of Rough Surfaces

2005 ◽  
Author(s):  
Tianxiang Liu ◽  
Geng Liu ◽  
Qin Xie
Keyword(s):  
Rough Surfaces ◽  
Computing Time ◽  
Surface Profile ◽  
Contact Problems ◽  
Contact Model ◽  
Computational Time ◽  
Real Contact Area ◽  
Asperity Contact ◽  
Pressure Distributions ◽  
Element Free

When contact problems are solved by numerical approaches, the surface profile is usually described by a series of discrete nodes with the same intervals along the coordinate axis. An adaptive-surface-based elasto-plastic asperity contact model is presented in this paper. Such a model is developed in order to reduce the computing time by removing the surface nodes that have little influence on the contact behavior of rough surfaces. The removed nodes are determined by setting a threshold. Thus, the contact problems can be described by fewer surface nodes but have similar results to the ones of the original surface. The adaptive asperity contact model is solved by using the element-free Galerkin-finite element (EFG-FE) coupling method because of its flexibility in domain descritization and versatility in node arrangements. The effects of different thresholds on the contact pressure distributions, real contact area, and the elasto-plastic stress fields in the contacting bodies are investigated and discussed. The results show that the computational time will dramatically reduce to about 50% when the relative error is about 5%.

On Pastewka and Robbins' Criterion for Macroscopic Adhesion of Rough Surfaces

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
M. Ciavarella
Keyword(s):  
Rough Surface ◽  
Root Mean Square ◽  
Rough Surfaces ◽  
Mean Square ◽  
Asperity Model ◽  
Factor Α ◽  
Rms Amplitude ◽  
Simplified Form

Pastewka and Robbins (2014, “Contact Between Rough Surfaces and a Criterion for Macroscopic Adhesion,” Proc. Natl. Acad. Sci., 111(9), pp. 3298–3303) recently have proposed a criterion to distinguish when two surfaces will stick together or not and suggested that it shows quantitative and qualitative large conflicts with asperity theories. However, a comparison with asperity theories is not really attempted, except in pull-off data which show finite pull-off values in cases where both their own criterion and an asperity based one seem to suggest nonstickiness, and the results are in these respects inconclusive. Here, we find that their criterion corresponds very closely to an asperity model one (provided we use their very simplified form of the Derjaguin–Muller–Toporov (DMT) adhesion regime which introduces a dependence on the range of attractive forces) when bandwidth α is small, but otherwise involves a root-mean-square (RMS) amplitude of roughness reduced by a factor α. Therefore, it implies that the stickiness of any rough surface is the same as that of the surface where practically all the wavelength components of roughness are removed except the very fine ones.

Approximate Macroscale Constitutive Relations Using a Finite Element Based Constitutive Equations for Microscale Contact

2008 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Finite Element ◽  
Contact Force ◽  
Rough Surfaces ◽  
Constitutive Relations ◽  
Cumulative Effect ◽  
Element Model ◽  
Tangential Component ◽  
Total Force ◽  
Asperity Contact ◽  
Elastic Plastic

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-asperity constitutive relations from a finite element model of their elastic-plastic interaction. Shoulder-shoulder asperity contact yields a slanted contact force consisting of both tangential (parallel to mean plane) and normal components. Multiscale modeling of the elastic-plastic rough surface contact is presented in which asperity-level FE-based constitutive relations are statistically summed to obtain total force in the normal and tangential direction. The equations derived are in the form of integral functions and provide expectation of contact force components between two rough surfaces. An analytical fusion technique is developed to combine the piecewise asperity level constitutive relations. This is shown to yield upon statistical summation the cumulative effect resulting in the contact force between two rough surfaces with two components, one in the normal direction and a half-plane tangential component.

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.

Direct numerical simulation of turbulence over systematically varied irregular rough surfaces

2019 ◽  
Vol 862 ◽  
pp. 781-815 ◽  
Author(s):  
Y. Kuwata ◽  
Y. Kawaguchi
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Root Mean Square ◽  
Drag Force ◽  
Rough Surfaces ◽  
Skin Friction Coefficient ◽  
Root Mean Square Roughness ◽  
Mean Square ◽  
Mean Velocity ◽  
Navier Stokes Equation

Lattice Boltzmann direct numerical simulation of turbulent open-channel flows over randomly distributed hemispheres at $Re_{\unicode[STIX]{x1D70F}}=600$ is carried out to reveal the influence of roughness parameters related to a probability density function of rough-surface elevation on turbulence by analysing the spatial and Reynolds- (double-) averaged Navier–Stokes equation. This study specifically concentrates on the influence of the root-mean-square roughness and the skewness, and profiles of turbulence statistics are compared by introducing an effective wall-normal distance defined as a wall-normal integrated plane porosity. The effective distance can completely collapse the total shear stress outside the roughness sublayer, and thus the similarity of the streamwise mean velocity is clearer by introducing the effective distance. In order to examine the influence of the root-mean-square roughness and the skewness on dynamical effects that contribute to an increase in the skin friction coefficient, the triple-integrated double-averaged Navier–Stokes equation is analysed. The main contributors to the skin friction coefficient are found to be turbulence and drag force. The turbulence contribution increases with the root-mean-square roughness and/or the skewness. The drag force contribution, on the other hand, increases in particular with the root-mean-square roughness whereas an increase in the skewness does not increase the drag force contribution because it does not necessarily increase the surface area of the roughness elements. The contribution of the mean velocity dispersion induced by spatial inhomogeneity of the rough surfaces substantially increases with the root-mean-square roughness. A linear correlation is confirmed between the root-mean-square roughness and the equivalent roughness while the equivalent roughness monotonically increases with the skewness. A new correlation function based on the root-mean-square roughness and the skewness is developed with the available experimental and direct numerical simulation data, and it is confirmed that the developed correlation reasonably predicts the equivalent roughness of various types of real rough surfaces.

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.

On the Nature of O-Rings in Contact With Rough Surfaces

1988 ◽  
Vol 110 (4) ◽  
pp. 632-637 ◽  
Author(s):  
W. E. Warren ◽  
J. G. Curro ◽  
D. E. Amos
Keyword(s):  
Theoretical Analysis ◽  
Root Mean Square ◽  
Contact Pressure ◽  
Contact Force ◽  
Rough Surfaces ◽  
Fundamental Importance ◽  
Elastic Behavior ◽  
Surface Irregularity ◽  
Mean Square ◽  
Irregular Surfaces

This work provides a theoretical analysis of the elastic behavior of an O-ring compressed between two rigid plates with irregular surfaces. Relations between deflection, contact force and contact pressure are obtained. The contact pressure, which is of fundamental importance in establishing criteria for effective sealing, is dependent upon both the amplitude and wavelength of the surface irregularity. This analysis suggests that surfaces in contact with O-ring seals should be characterized by the root mean square slope Δq in addition to the usual Ra which depends on amplitude only.

Simulation on Composite Backscattering from Rough Surface with Target above it

2012 ◽  
Vol 490-495 ◽  
pp. 603-607
Author(s):  
Wei Tian ◽  
Xin Cheng Ren
Keyword(s):  
Rough Surface ◽  
Root Mean Square ◽  
Cross Section ◽  
Correlation Length ◽  
Rectangular Cross Section ◽  
Mean Square ◽  
Method Of Moment ◽  
Backscattering Coefficient ◽  
One Dimensional ◽  
Surface Fluctuation

One-dimensional Gaussion rough surface is simulated and employed by Monte Carlo Method, the composite backscattering from one-dimensional Gaussion rough surface with rectangular cross-section column above it is studied using Method of Moment. The curves of composite backscattering coefficient with scattering angle and frequency of incident wave are simulated by numerical calculation, the influence of the root mean square and the correlation length of rough surface fluctuation, the height between the center of the rectangular cross-section column and the rough surface, the length and the width of the rectangular cross-section column is discussed. The characteristic of the composite back-scatting from one-dimensional Gaussion rough surface with a rectangular cross-section column above it is obtained. The results show that the influences of the root mean square and the correlation length of rough surface fluctuation, the height between the center of the rectangular cross-section column and the rough surface, the width of the rectangular cross-section column on the composite backscattering coefficients are obvious while the influences of the length of the rectangular cross-section column on the complex backscattering coefficient is less.

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.

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