This paper presents a physically-based simulation approach to predict the friction force at oil lubricated contacts for rubber o-ring seals in dynamic applications. In the boundary lubrication regime the friction coefficient is calculated using a recently developed contact mechanics theory. The stress and strain fields in the rubber are calculated using the finite element analysis (FEA). In the FEA the temperature-dependent nonlinear rubber behaviour is considered. Loads due to the assembly process, thermal expansion, system pressure and tangential friction forces are included in the analysis. In the mixed and hydrodynamic lubrication regimes, the asperity-asperity and fluid-asperity interactions are deter- mined from the Persson's dry-contact mechanics theory, the Reynolds-equation (gap flow) and the deformation model of the seal. To test the theory a test rig has been developed. Simulation results, carried out for an unpressurized o-ring seal system, are compared to the experimental data and, especially for small velocities where mixed lubrication prevails, the results are in good agreement.

Keywords: hydraulics,pneumatics,o-ringseal,finiteelementanalysisFEA,gapflow,rubberfriction,contactmechanics,fluidstructureinteraction