Deformation of Rough Line Contacts

1999 ◽  
Vol 121 (3) ◽  
pp. 449-454 ◽  
Author(s):  
E. R. M. Gelinck ◽  
D. J. Schipper
Keyword(s):  
Surface Roughness ◽  
Pressure Distribution ◽  
Half Width ◽  
Central Pressure ◽  
Bulk Deformation ◽  
The Real ◽  
Good Parameter ◽  
Real Area Of Contact ◽  
Line Contacts ◽  
Real Area

The influence of surface roughness on the bulk deformation of line contacts is studied. The model of Greenwood and Tripp (1967) will be extended to line contacts. It is found that the central pressure is a very good parameter to characterize the pressure distribution of rough line contacts. Function fits of the central pressure, the effective half width, the real area of contact, and the number of contacts are made. Comparison is made with the work of Lo (1969) and Greenwood et al. (1984).

A New Three-Dimensional Numerical Model of Rough Contact: Influence of Mode of Surface Deformation on Real Area of Contact and Pressure Distribution

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
A. Jourani
Keyword(s):  
Pressure Distribution ◽  
Pressure Field ◽  
Surface Deformation ◽  
Three Dimensional ◽  
Real Contact Area ◽  
Geometrical Approach ◽  
Deterministic Models ◽  
The Real ◽  
Real Area Of Contact ◽  
Real Area

Surface roughness causes contact to occur only at discrete spots called microcontacts. In the deterministic models real area of contact and pressure field are widely evaluated using Flamant and Boussinesq equations for two-dimensional (2D) and three-dimensional (3D), respectively. In this paper, a new 3D geometrical contact approach is developed. It models the roughness by cones and uses the concept of representative strain at each asperity. To discuss the validity of this model, a numerical solution is introduced by using the spectral method and another 3D geometrical approach which models the roughness by spheres. The real area of contact and the pressure field given by these approaches show that the conical model is almost insensitive to the degree of isotropy of the rough surfaces, which is not the case for the spherical model that is only valid for quasi-isotropic surfaces. The comparison between elastic and elastoplastic models reveals that for a surface with a low roughness, the elastic approach is sufficient to model the rough contact. However, for surfaces having a great roughness, the elastoplastic approach is more appropriate to determine the real area of contact and pressure distribution. The results of this study show also that the roughness scale modifies the real contact area and pressure distribution. The surfaces characterized by high frequencies are less resistant in contact and present the lowest real area of contact and the most important mean pressure.

The Area of Contact Between Rough Surfaces and Flats

1967 ◽  
Vol 89 (1) ◽  
pp. 81-87 ◽  
Author(s):  
J. A. Greenwood
Keyword(s):  
Surface Roughness ◽  
Work Hardening ◽  
Deformation Mode ◽  
Constant Independent ◽  
The Real ◽  
Real Area Of Contact ◽  
Ideal Plastic ◽  
Average Size ◽  
Contact Size ◽  
Real Area

If the real area of contact between surfaces is determined by ideal plastic flow of the microcontacts, then the proportionality between the area of contact and the load follows immediately. If the deformation mode is elastic, or elastic-plastic, or plastic with work-hardening, which will be the usual cases, then the proportionality is harder to explain. However, by considering the statistical distribution of heights of the surface asperities, it can be shown that the average size of a microcontact is almost constant, independent of load; consequently, the fact that the contact pressure at a single micro-contact may vary with contact size becomes irrelevant. If the real origin of the laws of friction is in the statistics of surface roughness and not in a particular mode of deformation, the applicability of the Bowden and Tabor theory of friction to plastics and other nonmetals becomes more readily understandable.

Microcontact Model for Paper-Based Wet Friction Materials

2001 ◽  
Vol 124 (2) ◽  
pp. 414-419 ◽  
Author(s):  
H. Gao ◽  
G. C. Barber
Keyword(s):  
Surface Roughness ◽  
Density Distribution ◽  
Friction Material ◽  
Friction Materials ◽  
The Real ◽  
Real Area Of Contact ◽  
Wet Friction ◽  
Gaussian Density ◽  
Negative Skewness ◽  
Real Area

This paper is focused on the real area of contact for paper-based wet friction materials during the engagement of wet clutches. The deformation of the wet friction material is identified as elastic during the engagement. A microcontact model is proposed considering both surface roughness and skewness. A Weibull density distribution is employed in the model rather than a Gaussian density distribution. This model is compared with the Greenwood-Williamson (GW) model for the cases of positive skewness, zero skewness and negative skewness. The real areas of contact of new, run-in and glazed wet friction materials were investigated using this microcontact model. Both surface roughness and skewness were found to have a great effect on the real area of contact.

A Study of the Relative Surface Conformity Between Two Surfaces in Sliding Contact

1991 ◽  
Vol 113 (4) ◽  
pp. 755-761 ◽  
Author(s):  
Fu-Xing Wang ◽  
P. Lacey ◽  
R. S. Gates ◽  
S. M. Hsu
Keyword(s):  
Surface Roughness ◽  
Computer Program ◽  
Contact Area ◽  
Sliding Contact ◽  
Test Duration ◽  
Lubrication Mechanism ◽  
The Real ◽  
Wear Process ◽  
Real Area Of Contact ◽  
Real Area

The surface roughnesses of two surfaces in a wear contact can change throughout the course of the wear process. This may or may not change the lubrication mechanism of the system depending on the real area of contact as influenced by the changes in the surface roughness. The present work examines the changes in surface roughness within the contact area, as well as the relative mating of the two surfaces. To quantify the similarity between the two wear surfaces, a new concept, the relative surface conformity, has been defined and developed. To effectively measure this parameter, a computer program was written to input the wear scar profilometry traces and to calculate the relative surface conformity of the two. Finally, the relative surface conformity was shown to rise with increasing test duration, during running in.

On the Contact of Curved Rough Surfaces: Contact Behavior and Predictive Formulas

2014 ◽  
Vol 81 (11) ◽  
Author(s):  
Ali Beheshti ◽  
M. M. Khonsari
Keyword(s):  
Pressure Distribution ◽  
Point Contact ◽  
Pressure Profile ◽  
Bulk Deformation ◽  
Total Displacement ◽  
Real Area Of Contact ◽  
Contact Compliance ◽  
Predictive Formulas ◽  
Maximum Contact ◽  
Real Area

The statistical microcontact models of Greenwood–Williamson (GW), Kogut–Etsion (KE), and Jackson–Green (JG) are employed along with the elastic bulk deformation of the contacting solids to predict the characteristics of rough elliptical point contact such as the pressure profile, real area of contact, and contact dimensions. In addition, the contribution of the bulk deformation and the asperity deformation to the total displacement is evaluated for different surface properties and loads. The approach involves solving the microcontact and separation equations simultaneously. Also presented are formulas that can be readily used for the prediction of the maximum contact pressure, contact dimensions, contact compliance, real area of contact, and pressure distribution.

Analysis of the Real Area of Contact Between a Polymeric Magnetic Medium and a Rigid Surface

1984 ◽  
Vol 106 (1) ◽  
pp. 26-34 ◽  
Author(s):  
Bharat Bhushan
Keyword(s):  
Complex Modulus ◽  
Critical Value ◽  
Computer Applications ◽  
Hard Material ◽  
Rigid Surface ◽  
Magnetic Medium ◽  
The Real ◽  
Real Area Of Contact ◽  
The Mean ◽  
Real Area

The statistical analysis of the real area of contact proposed by Greenwood and Williamson is revisited. General and simplified equations for the mean asperity real area of contact, number of contacts, total real area of contact, and mean real pressure as a function of apparent pressure for the case of elastic junctions are presented. The critical value of the mean asperity pressure at which plastic flow starts when a polymer contacts a hard material is derived. Based on this, conditions of elastic and plastic junctions for polymers are defined by a “polymer” plasticity index, Ψp which depends on the complex modulus, Poisson’s ratio, yield strength, and surface topography. Calculations show that most dynamic contacts that occur in a computer-magnetic tape are elastic, and the predictions are supported by experimental evidence. Tape wear in computer applications is small and decreases Ψp by less than 10 percent. The theory presented here can also be applied to rigid and floppy disks.

A Relationship Between Autocorrelation Length and Adhesive Friction Behavior of Rough Surfaces

2005 ◽  
Author(s):  
Yilei Zhang ◽  
Sriram Sundararajan
Keyword(s):  
Rough Surface ◽  
Spatial Information ◽  
Roughness Parameter ◽  
Hertzian Contact ◽  
Root Mean Square Roughness ◽  
Friction Behavior ◽  
The Real ◽  
Real Area Of Contact ◽  
Autocorrelation Length ◽  
Real Area

Autocorrelation Length (ACL) is a surface roughness parameter that provides spatial information of surface topography that is not included in amplitude parameters such as Root Mean Square roughness. This paper presents a statistical relation between ACL and the real area of contact, which is used to study the adhesive friction behavior of a rough surface. The influence of ACL on profile peak distribution is studied based on Whitehouse and Archard’s classical analysis, and their results are extended to compare profiles from different surfaces. With the knowledge of peak distribution, the real area of contact of a rough surface with a flat surface can be calculated using Hertzian contact mechanics. Numerical calculation shows that real area of contact increases with decreasing of ACL under the same normal load. Since adhesive friction force is proportional to real area of contact, this suggests that the adhesive friction behavior of a surface will be inversely proportional to its ACL. Results from microscale friction experiments on polished and etched silicon surfaces are presented to verify the analysis.

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