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The study of material properties is fundamental to the design, analysis, and service life estimation of rubber products. To investigate the usefulness of material test data the paper compares material test properties with those of a moulded product. The material properties include the stress-strain relationship, ageing properties in air and oil and abrasion properties. The study revealed the crucial material properties that directly affect the performance of a valve stem seal (VSS). In addition, a modified least square method is introduced to the Mooney-Rivlin fitting procedure.

The development of any sealing product invariably involves some form of physical leakage testing, and although this evaluates the performance of the product, it gives no insight to the fundamental sealing mechanism of the design. Elastohydrodynamic lubrication theory was used to study this problem. The study of hydrodynamic lubrication, where there is fluid flow, is, from a mathematical standpoint, the application of a reduced form of the Navier-Stokes equation with the continuity equation. This equation is well known as the Reynolds equation. However, normally, the Reynolds equation is derived from Cartesian co-ordinates where the curvatures of surfaces are ignored. However, a valve stem seal (VSS) works in an axisymmetric environment. This paper discusses the development of the elastohydrodynamic lubrication theory in a cylindrical co-ordinate system and its usefulness in the prediction of metered leakage across a valve stem seal.

Axisymmetric static Finite Element (FE) models were used to study sealing geometric changes on valve stem seals (VSSs). FE analysis is used to characterise the deformation of the rubber seal, and the contact pressure distribution. The deformations were analysed using animation techniques. The research gives a first order approximation, revealing magnitude and direction of seal lip to valve stem contact. Finally, a hypothesis on the sealing and lubricating mechanism is proposed.

As a precursor to a full leakage study on Valve Stem Seals (VSS), Finite Element (FE) Analyses were carried out using ANSYS 5.2. Two dimensional axisymmetric static models were developed, with the Mooney-Rivlin strain energy function used to describe the nonlinear behaviour of the rubber. For each analysis, elasto-hydrodynamic lubrication was assumed during valve stem reciprocation. Each model featured an alteration to a ‘standard’ design of valve stem seal (known to give excellent performance over its life cycle), the effect of these differences was then investigated. Where possible, physical measurements were made for comparison with the FE results. This research gives a first order approximation, revealing magnitude and direction of seal lip to valve stem contact.