Modeling of Elastic/Plastic Contact Between Nominally Flat Rough Surfaces Using an n-Point Asperity Model

Abstract

The asperities of rough surfaces have long been considered to be points higher than their immediate neighbors. Based on this concept, theories were developed for quantitatively understanding the elastic and plastic nature of contact between rough surfaces. Recently it has been recognized that the above model for asperities is inadequate. Consequently, all the models that have been constructed based on that model are inadequate too. In this paper, based on a newly developed multiple-point asperity model, the elastic and plastic contact problem between nominally flat surfaces is reformulated. This leads to finding the deformed area, and load produced by the contact. The model is developed for the general form of isotropic rough surfaces with arbitrary height distribution and autocorrelation function (ACF). The microcontact areas generated by each asperity contact are considered to be circles. The Gaussian distribution of heights and exponential ACF are considered as a benchmark to compare the results of the new model with the existing models. Using results from numerical models developed by other groups, the new model is validated.

Adhesive Friction Based on Accurate Elastic-Plastic Finite Element Analysis and n-Point Asperity Concept

“…A surface profile with low value of correlation length will carry thin and sharp asperities while that having high value of correlation length will have thick and flat asperities. In the present study practical value of correlation length ) ( is chosen as 6.5 μm which is same as that used in earlier studies [18,30].…”

“…The applied load and tangential load formulations consists of different surface roughness and material properties related parameters like number of height ordinates ) (n , correlation coefficient ) ( , adhesion index ) ( and plasticity index ) ( .The different conditions of contact with respect to variation in material properties and surface roughness features are obtained by varying the well-defined indices, viz., the plasticity index ) ( [18] and adhesion index ) ( [30]. Care is taken in selection of these indices for study so that we get significantly different zones with respect to plasticity effect and adhesion effect.…”

“…As per Hariri et al [18] and Sahoo et al [30], at critical point of yielding inception, the curvature coefficient and interference are related as …”

“…Load values in equations (23) and (24) are already in normalized form. Equations (25) and (26) It is to be noted that the plasticity index (ψ) [18] and adhesion index (ϕ) [30], got introduced in above equations (23) - (24) and (27) - (28) in normalization process.…”

Adhesive friction at the contact between rough surfaces using n-point asperity model

“…Thus as compared to conventional Greenwood and Williamson model [17], the n-point asperity model represents the rough surfaces in more realistic form as it considers the variation in form of asperities in vertical direction (asperity height direction) as well as horizontal direction (asperity spacing direction). Based on this new n-point asperity model, the elastic/plastic normal contact problems both non-adhesive [21] and adhesive contact [22] have been considered earlier. However, to the best of the authors' knowledge, no study is available on analysis of adhesive friction of contacting surfaces that involves n-point asperity model.…”