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.

Prediction of Thermal Contact Conductance by Surface Deformation Analysis

2001 ◽  
Author(s):  
Vishal Singhal ◽  
Suresh V. Garimella
Keyword(s):  
Surface Deformation ◽  
Thermal Contact ◽  
Thermal Contact Conductance ◽  
Deformation Analysis ◽  
Improved Method ◽  
Contact Conductance ◽  
The Real ◽  
Real Area Of Contact ◽  
Surface Profiles ◽  
Real Area

Abstract An improved method has been developed for the prediction of thermal contact conductance between two nominally flat metallic rough surfaces by analysis of the deformation of individual asperities in contact. The deformation of the asperities in contact has been taken into account by considering three different modes of deformation — elastic, elastic-plastic and plastic. The model uses an iterative procedure to determine the real area of contact between the deformed surfaces for a given load, nominal area of contact, surface profiles and material properties of the surfaces in contact. The contact conductance is then determined as a function of the ratio of the real area of contact to the apparent area of contact The predicted variation of contact conductance with load obtained from the model is compared to simplified analytical predictions in the literature as well as to experiments conducted as part of this work.

Real Area of Contact in a Soft Transparent Interface by Particle Exclusion Microscopy

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Kyle D. Schulze ◽  
Alex I. Bennett ◽  
Samantha Marshall ◽  
Kyle G. Rowe ◽  
Alison C. Dunn
Keyword(s):  
Flexible Electronics ◽  
Soft Matter ◽  
Colloidal Particles ◽  
Contact Region ◽  
Real Contact Area ◽  
The Real ◽  
Real Area Of Contact ◽  
Static Indentation ◽  
Real Area

Soft matter mechanics are characterized by high strains and time-dependent elastic properties, which complicate contact mechanics for emerging applications in biomedical surfaces and flexible electronics. In addition, hydrated soft matter precludes using interferometry to observe real areas of contact. In this work, we present a method for measuring the real area of contact in a soft, hydrated, and transparent interface by excluding colloidal particles from the contact region. We confirm the technique by presenting a Hertz-like quasi-static indentation (loading time > 1.4 hrs) by a polyacrylamide probe into a stiff flat surface in a submerged environment. The real contact area and width were calculated from in situ images of the interface processed to reduce image noise and thresholded to define the perimeter of contact. This simple technique of in situ particle exclusion microscopy (PEM) may be widely applicable for determining real areas of contact of soft, transparent interfaces.

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).

On the Mechanism of Contact Between Metal Surfaces: Part 2—The Real Area and the Number of the Contact Points

1968 ◽  
Vol 90 (1) ◽  
pp. 81-88 ◽  
Author(s):  
T. Tsukizoe ◽  
T. Hisakado
Keyword(s):  
Contact Area ◽  
Three Dimensional ◽  
Real Contact Area ◽  
Load Range ◽  
The Real ◽  
Real Contact ◽  
Contact Points ◽  
Theoretical Analyses ◽  
Total Contact Area ◽  
Real Area

Assuming that the distribution curve obtained from the profile curve of the surface has a normal distribution, the relation between the real contact area and the separation is obtained theoretically in the case of ideal plastic flow of the microcontacts. If the asperities are cones of the same angle which depends on the surface roughness, the three-dimensional number and the distribution of the radii of contact points are also deduced theoretically. The results of the theoretical analyses are compared with the experimental results for the real contact areas and the numbers of the contact points. Results show that over the wide load range the average radii of contact points are almost constant; consequently, the total contact area is increased mainly owing to the increase in the number of the contact points.

Real Area of Contact between a Rough Surface and a Softer Optically Flat Surface

1970 ◽  
Vol 12 (4) ◽  
pp. 259-267 ◽  
Author(s):  
P. W. O'Callaghan ◽  
S. D. Probert
Keyword(s):  
Applied Pressure ◽  
Real Contact Area ◽  
Recent Theory ◽  
Micro Hardness ◽  
Normal Loading ◽  
The Real ◽  
Flat Interface ◽  
Contact Points ◽  
Real Area Of Contact ◽  
Real Area

The mean number of contact spots per unit area and their mean radius were measured and hence the real area of contact deduced for a rough-to-flat interface under normal loading. The contact pressure was varied from zero to half the micro-hardness of the softer material. The resulting experimental evidence did not endorse the predictions from the recent theory of Tzukizoe and Hisakado, which incorrectly assumes that the real contact area is given by the applied pressure P divided by the micro-hardness M of the softer material. It was found that this area equalled K( P/ M) n, where the coefficient K and index n depend upon the applied pressure range. A maximum number of contact points was encountered at a dimensionless loading ( P/ M) approximately equal to 7·5 × 10-3.

Role of Mechanical Properties and Surface Texture in the Real Area of Contact of Magnetic Rigid Disks

1989 ◽  
Vol 111 (3) ◽  
pp. 452-458 ◽  
Author(s):  
B. Bhushan ◽  
M. F. Doerner
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Surface Texture ◽  
Three Dimensional ◽  
Effective Elastic Modulus ◽  
The Real ◽  
Real Area Of Contact ◽  
Disk Structure ◽  
Rigid Disks ◽  
Real Area

The analysis of real area of contact for particulate and thin-film rigid disks is presented. The mechanical properties (hardness and modulus) of the disk structure are measured by a nanoindentation apparatus and the surface texture is measured by a three-dimensional noncontact optical profiler. For typical rigid disks selected for this study, we find that most contacts are elastic; the same observation was made by Bhushan (1984) for flexible media. In the case of elastic contacts, the real area of contact is governed by the effective elastic modulus of the disk structure and its surface summit distribution. Typical values for the fractional real area of contact, number of contacts per unit area, mean asperity diameter, and mean real pressure for a thin-film disk are calculated to be of the order of 5 × 10−5, 20/mm2, 1μm, and 200 MPa, respectively.

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.

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