  This paper addresses the issue of the determination of the frictional stress
distribution from the inversion of the measured surface displacement field for
sliding interfaces between a glass lens and a rubber (poly(dimethylsiloxane))
substrate. Experimental results show that high lateral strains are achieved at
the periphery of the sliding contacts. As a consequence, an accurate inversion
of the displacement field requires that finite strains and non linear response
of the rubber substrate are taken into account. For that purpose, a Finite
Element (FE) inversion procedure is implemented where the measured displacement
field is applied as a boundary condition at the upper surface of a meshed body
representing the rubber substrate. Normal pressure is also determined by the
same way, if non-diverging values are assumed at the contact edge. This
procedure is applied to linearly sliding contacts as well as on twisting
contacts.
