This thesis is concerned with issues relating to the development of an active sealing system
for hydraulic actuators where the sealing elements can be radially extended and retracted
to vary the friction and leakage characteristics. In order to determine the feasibility of the
active sealing concept it is necessary to establish that varying the seal geometry may achieve
useful improvements in the friction-leakage trade-off and that a practical method of achieving
this seal extension can be realised. Experimental and simulation approaches for seal friction
prediction have been developed and active seal prototypes produced to demonstrate the
Experiments were carried out to measure the constant velocity friction for single-lip and
double-lip seals over a range of sliding speeds and sealed pressures with special consideration
applied to the instroke-outstroke direction dependence. Additional experiments were performed
with sinusoid motion to provide an indication of the transient friction characteristics.
Friction was shown to increase towards the end of the outstroke cycle and decrease once the
instroke motion began.
Tribology simulations were produced based on the results of a FEA simulation of the
rod-seal contact pressure. Empirical friction-load relationships and novel contact mechanics
approaches for high loads were considered. Simulations based on the Reynolds equation
including standard inverse EHL theory and the GW-average Reynolds lubrication are also
presented. Experimental agreement could be improved if loading is assumed to transfer to
the fluid to maintain a fluid film. A hysteresis friction model was also developed in attempt
to improve the prediction of speed dependent friction.
Two active seal prototypes were produced, each with an adjustable external pressure
supplied to the outer circumference of the sealing element. Constant velocity friction measurements
for different external pressures and the transient response following step changes
in this pressure are presented.
|Date of Award||1 Jul 2010|
|Supervisor||Patrick Keogh (Supervisor), Derek Tilley (Supervisor), Nigel Johnston (Supervisor) & Chris Bowen (Supervisor)|
- fluid power
- fluid sealing