Investigation on load-dependent roughness variations

Abstract

In order to investigate the level of influence of roughness in the evaluation of the dimensionless film thickness Λ a study has been started to find a simplified but sufficiently general method to take into account the roughness variations of bodies, even with different characteristics, because of varying load. The investigation is based on a linear measured roughness profile. In this work, a model developed for the approximation of measured profiles through parabolas and formulas used for solving the contact mechanics problem are reported. The first results obtained with some specimens, used in previous works for experimental investigations on non-conformal line contacts, are presented. The specimens' surfaces are analysed both by a three-dimensional computer-controlled stylus profilometer and by an apparatus that allows investigations also under loaded conditions using optical interferometry. A way to compare the experimental and the theoretical results, in order to make some necessary verifications correlating line and surface aspects, is indicated. A first estimation of the variation of Λ under load is finally made. The method developed for the evaluation of roughness variations under load seems to furnish reasonable results in quite good agreement with the experimental ones. The results obtained with the investigated non-conformal line contacts, presenting characteristics in not complete agreement with the model-based hypotheses, give a certain confidence about the applicability of this simplified methodology to different kinds of contacts.