Low Friction Radial Lip Seals for Railcar Bearings

Abstract

Abstract. A numerical analysis investigates the feasibility of low-power-loss seals using alternative materials in a standard lip seal form factor for railcar bearing seal applications. This form factor is a common topology that finds use in other applications including air compressors, turbine engines, aircraft landing systems, and chemical equipment. The form factor, along with hyperelastic materials, most commonly nitrile butadiene rubber (NBR) for railcar bearing seals, is known for its reliability. The alternative materials of interest are polytetrafluoroethylene (PTFE) and filled PTFE with 15% glass and 5% MoS2 (PTFE-GM). In addition to a low friction coefficient, these materials exhibit dry-running capability and chemical compatibility. The impact of material choice, wear, and variations in seal design parameters on the contact zone and contact pressure distribution is presented. An axisymmetric, multiscale finite element model (FEM) with Archard wear of the flexible seal and rigid shaft is developed such that the materials operate at a stress state below the yield strength such that no plastic flow occurs during assembly, installation, and operation. Results are presented showing the contact pressure distributions of varying scraper angles, barrel angles, garter spring tensions, R-values, and interference fit. Results show PTFE-GM to be feasible for railcar bearing applications with a 49.6% reduction in power as compared to NBR. Pure PTFE shows a reduction of 87.6%, which represents an upper limit on power reduction but is not feasible in this form factor due to its high wear-rate.