This paper describes some development in experimental and numerical procedures to estimate friction torque on a rotating shaft due to radial elastomeric seals. Different test rigs have been built, in order to highlight the relationship between the overall friction and the local behavior of each lip portion in presence of dynamic eccentricities. A direct measurement has been performed with a rotating shaft machine and results have been compared with the torque calculated as product of a global frictional coefficient and the normal stress on the lip surface. The latter has been computed by a FEM simulation which has been optimized to evaluate the lip deformation due to mounting interference. Experimental results about radial and tangential oscillation of a limited lip region, repeated for different elastomer, allowed to calculate the frictional coefficient as the ratio of the friction force and the force pressing the lip on the shaft surface in some cases of practical interest.
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