Optical measurement for the estimation of contact pressure and stress

This paper presents experiments based on optical measurements which allowed characterising the elastic strains and stresses induced by a real contact between two parts. For that purpose, a disc of polymethyl methacrylate (PMMA) was indented by a rigid steel punch. Using the transparency of the material, the displacement field of the contact surface was measured, across the thickness of the sample, using a chromatic confocal sensor. Boussinesqʹs potential theory was then applied to this data in order to evaluate the true pressure of the contact. It allowed also estimating the strains and stresses at any point of the indented sample.