MEMS-based contact stress ?eld measurements at a rough elastomeric layer: local test of Amontons’ friction law in static and steady sliding regimes

摘要

We present the results of recent friction experiments in which a MEMS-based sensing device is used to measure both the normal and tangential stress ?elds at the base of a rough elastomer ?lm in frictional contact with smooth, rigid, glass indentors. We consider successively multicontacts under (i) static normal loading by a spherical indentor and (ii) frictional steady sliding conditions against a cylindrical indentor, for an increasing normal load. In both cases, the measured ?elds are compared to elastic calculations assuming (i) a smooth interface and (ii) Amontons’ friction law. In the static case, signi?cant deviations are observed which decrease with increasing load and which vanish when a lubricant is used. In the steady sliding case, Amontons’ law reproduces rather satisfactorily the experiments provided that the normal/tangential coupling at the contact interface is taken into account. We discuss the origin of the di?erence between the Amontons ?elds and the measured ones, in particular the e?ect of the ?nite normal and tangential compliances of the multicontact interface.