In various industrial applications, fully metallic seals are employed to guarantee a high level of sealing of mechanical assemblies under severe thermodynamics conditions. Their performance is entirely controlled by the mechanical behaviour of the contacting interface between the facing rough surfaces of the seal and the flange, similar to a fracture, anisotropic and multi-scale by nature. The objective of the thesis is to improve our comprehension and predicting capabilities of the sealing mechanisms of gases in a rough fracture using a numerical approach coupled with experiments.

The work takes place in the continuity of previous studies performed at the laboratory. It will focus first on the conception of an experimental apparatus that will be used to press two metallic rough surfaces against each other with a given force, having the possibility to measure the corresponding leakage rate as well. The experiments will be performed during loading and unloading of the contact to characterise the hysteresis phenomenon brought by the permanent deformation of the sealing material at first loading. The results obtained will be compared to numerical ones in various configurations using models developed at the laboratory, in order to validate these latter. By experience, it is known that the flow simulation gives satisfactory results, but discrepancies persist in the contact mechanics model. Thus, it should be improved regarding the plastic effects specifically encountered in contact, considering the finite thickness of the sealing liner and optimizing the computational cost. Afterwards, the preceding results will be transposed to the industrial case of the HELICOFLEX metal seal, using a two-scale modelling strategy, coupling the macroscopic information at the seal scale to the microscopic one at the roughness scale.