Study of leakage and friction of flexible seals for steady motion via a numerical approximation method

A numerical model has been developed to solve the steady-state, smooth-surface elastohydrodynamic problem of flexible (polymeric or elastomeric) seals of nominally rectangular or toroidal shape, most commonly found in linear and rotary hydraulic actuators for reciprocating motion. The seals can be fluid-pressurized or even act as wipers. The model offers the advantage of stable and very fast, approximate numerical solution of the EHL sealing problem, which has not been given much attention in the literature in the last 40 years. This model by-passes common obstacles in elastohydrodynamics of soft contacts. It uses an approach similar to that at the beginning of the Inverse Hydrodynamic theory but then deviates from it, avoiding the tricky part of solving a cubic equation. It is relatively easy to program and requires no more than a few hundredths of a second of processing time of a modern personal computer for a complete solution and performance analysis, which is a leap for-ward compared with previous studies in the literature that required hundreds of iterations and finite element analysis to achieve similar results. In this study and for demonstration purposes, it is applied for a wide range of operating conditions, namely operating temperature between -54 and + 99 degrees C, average contact pressure between 5 and 180 MPa and sliding speed between 0.6 and 38 mm/s (although these limits can safely be exceeded with the model). Results are presented for the contact pressure and film thickness distribution, seal leakage and hydrodynamic friction force. A study on the effects of the seal initial interference, sliding speed, seal geometry, and fluid starvation on lubrication and sealing performance have been derived for the previously mentioned range of operating conditions and for initially conformal and non-conformal sealing contacts, with the seals both stationary and non-stationary. The results are in agreement with those of several well-known theoretical and experimental studies in this field. The present study is for steady-state conditions and will be extended to a transient elastohydrodynamic analysis in another study. (c) 2005 Elsevier Ltd. All rights reserved.