Local contact stress measurements at a rough interface

An original MEMS-based force sensing device is designed which allows to measure spatially resolved normal and tangential stress fields at the base of an elastomeric film. This device is used for the study of the contact stress between a rough film and a smooth glass sphere under normal load. The measured profiles are compared to Finite Elements Method calculations for a smooth contact with boundary conditions obeying Amontons-Coulomb's friction law. The accuracy of the measurements allows to discriminate between dry and lubricated contact conditions and to evidence load-dependent deviations from Amontons-Coulomb's profiles. These deviations are qualitatively interpreted by taking into account the finite compliance of the micro-contact population.