title: A homodyne quadrature laser interferometer for  micro-asperity deformation analysis.
abstract: We report on the successful realization of a contactless, non-perturbing, displacement-measuring system for characterizing the surface roughness of polymer materials used in tribological applications. A single, time-dependent, scalar value, dubbed the collective micro-asperity deformation, is extracted from the normal-displacement measurements of normally loaded polymer samples. The displacement measurements with a sub-nanometer resolution are obtained with a homodyne quadrature laser interferometer. The measured collective micro-asperity deformation is critical for a determination of the real contact area and thus for the realistic contact conditions in tribological applications. The designed measuring system senses both the bulk creep as well as the micro-asperity creep occurring at the roughness peaks. The final results of our experimental measurements are three time-dependent values of the collective micro-asperity deformation for the three selected surface roughnesses. These values can be directly compared to theoretical deformation curves, which can be derived using existing real-contact-area models.
authors.affiliation: Iskra Mehanizmi doo, Lipnica 8, Kropa 4245, Slovenia. aljaz.pogacnik@iskra-mehanizmi.si
authors.forename: Aljaž
authors.initials: A
authors.lastname: Pogačnik
authors.forename: Tomaž
authors.initials: T
authors.lastname: Požar
authors.forename: Mitjan
authors.initials: M
authors.lastname: Kalin
authors.forename: Janez
authors.initials: J
authors.lastname: Možina