General results for loading and unloading rough elasto-plastic interfaces

From the classical model of Bowden and Tabor it is known that metallic materials make contact only on a small fraction of the nominal contact area, where pressure is so high that plastic deformations is likely. While the contact area has been extensively studied within this context, indentation has attracted less attention. In this work we thus characterize the relationship between load and indentation for nominally flat Gaussian surfaces, finding universal trends which persist when either the level of plasticity or the indentation depth change. We study both loading and unloading trends. Also, we discuss the height distribution of the surfaces resulting from cumulative plastic deformation. For all this cases, we obtain very simple and closed form analytical fittings that allow a convenient and general use of the results here presented. Finally, we compare the results obtained from the model, based on Boundary Element model and perfect plasticity, with experimental result, to justify the validity of its use. • Indentation of elastoplastic Gaussian self-affine rough surfaces is characterized. • Results are summarized by easy-to-use analytical formulas provided by fitting. • Surface changes due to plasticity are characterized through height distributions. • The plasticity model used is tested against experimental data.