Computation and Measurement of the Sealing Contact Stress and its Role in Rotary Lip Seal Design

Abstract

This paper deals with the prediction of contact forces and distribution of the contact stress in elastomeric lip seals for rotary shaft applications. The study of the forces and stresses of the sealing contact has always been one of the basic steps in the process of designing a seal. In this paper the problem is treated by applying up-to-date finite element methods in combination with more traditional analytic techniques. In the experimental part of this work the mechanical characterization of the elastic properties of the rubber material and the measurement of contact forces, pressure distribution and deformations of the sealing contact are also discussed.

The computed results suggest that the traditionally assumed form of the pressure distribution for rotary lip seals, i.e. the asymmetric semielliptical shape with a single pressure peak on the oil side of the sealing interface, belongs to a new lip seal. Indeed, just a few hours of running-in time are sufficient to transform this contact pressure into a quite flat and symmetric distribution with a modest ridge located at each edge of the contact area. Comparison of numerical and experimental data indicates good overall agreement of the results. In particular, good correspondence was found between the calculated and measured pressure distributions from image-processing experiments on the dry contact imprint of the seal lip contact.