Evaluation of Contact Parameters Using Single Asperity Contact Model for the Normal Contact of Rough Surfaces

An axisymmetrical hemispherical asperity in contact with a rigid flat is modeled for an elastic-perfectly plastic material. The single asperity finite element contact model is used for determining the contact parameters for the normal contact between two rough surfaces. The objective of this paper is to show the difference in the statistical model developed by Kogut-Etsion Model (KE Model) and Jackson-Green Model (JG Model) for the materials having higher yield strength, in calculating the contact parameters. The present analysis extends the work of KE Model and JG Model. KE model predicts that when the interference ratio (ω/ω_c) reaches 110; the mean contact pressure to yield strength ratio (p/Y) reaches 2.8, after that plastic deformation starts. JG Model extends KE model for materials of different yield strengths and concludes that hardness does not depends upon the strength of the material alone. Based on their results, they developed two statistical models to calculate the contact parameters for the entire surfaces. But JG model results violate Abbott-Firestone (AF Model) work based contact area ratio limitation. The present analysis covers higher interference ratios. The elastic perfectly plastic assumption made in the present analysis satisfies AF model results for higher yield strengths and the contact area ratio (A*/ω*) never crosses 2. The predicted results shows that the statistical model developed by KE and JG models are still not enough to calculate accurately the real contact area and contact load for the entire surfaces based on FEM single asperity model for all the yield strengths.