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This paper summarizes the results and findings of a program to design, develop, and evaluate actuator rod seals for use in advanced aircraft high-temperature hydraulic systems. The rod seals are intended to function efficiently and reliably for 3000 hr in the temperature range of -40-500 F. Preliminary studies of various material and design combinations showed that a polyimide low-pressure second-stage V-seal in a two-stage configuration had the greatest potential in long-term duty cycle testing in a simulated actuator test system. Modifications of this seal that provided for improved fatigue life and more efficient loading met the test objectives of 20 X 106 short-stroke cycles of operation at 500 F. Severity of this testing was equivalent to 3000 hr of duty cycle operation. The validity of design techniques used to achieve performance goals was shown.

Filled tetrafluoroethylene (TFE) backup rings offer superior resistance to extrusion, wear, deformation and cold flow in dynamic and static O-ring sealing applications. TFE compounds consisting of various concentrations (5 - 60%) of inorganic fillers such as glass, molybdenum disulphide, graphite and bronze are the most commonly used materials for backup rings. An important consideration in the use of these filled materials is that hard mating surfaces be used to minimize abrasive wear. However, recently developed organic-type fillers have extended the utility of filled backup rings to applications involving non-hardenable mating surfaces such as hard anodized aluminum and titanium.

Visteon Automotive Systems has developed an Electro-Hydraulic Power Assist Steering (EHPAS) System. This low-cost system uses conventional hydraulic power steering components with an electrically-driven and electronically-controlled power steering pump. This paper presents the Visteon EHPAS system and its development process. This process began with analytical modeling of the EHPAS system and integration of these models with a two degree of freedom (2DOF) vehicle model. These models were critical for system analysis and control strategy design. The EHPAS system sizing procedure and control strategy performance optimization were verified with the use of a real-time computer designed by Ford Motor Company, and by specially-designed Visteon test benches. Finally, EHPAS equipped test vehicles were tuned for high performance, providing better feel and fuel economy than conventionally equipped base line vehicles.