An integrated approach to characterize liquid leakage through metal contact seal
Résumé
Static seal is of major concern in spatial technology and because of severe thermodynamic conditions, direct metal/metal contact is often used. This work is a contribution to the study of liquid leakage through a rough metal contact resulting from the tightening of two machined surfaces. Our approach is based on experimental measurements of leak-rates on a model configuration close to a real design on the one hand and on theoretical developments for predictive estimates of leakage on the other hand. Experiments are performed on turned metal samples reproducing the contact surface of a real metal seal. The sample is pressed against a sapphire surface under a controlled contact pressure using a specific experimental set-up. Leak tests are carried out with a liquid and leak-rate is measured versus liquid pressure and contact load using gas chromatography. Starting from the initial topology of the surface, elastic and plastic deformations are computed applying contact pressures corresponding to the ones used in the experiment. Computed deformed surfaces are further employed to form the aperture field on a representative part of the contact on which flow computation is performed. Assuming the flow to be exclusively pressure driven, the equivalent "permeability" of the contact is computed using the local Reynolds approximation classically employed for flow in fracture with slowly varying aperture. Experimental results are commented and compared to predictions.
