Soutenance de thèse : Andrei Shvarts

Couplage mécano-fluidique pour le contact et le frottement à petites et à grandes échelles

Résumé : 
Dans cette thèse, nous travaillons sur un problème d'interaction fluide-structure au niveau des interfaces du contact. Le problème du transport de fluide dépend de la solution du problème de contact mécanique, qui, à son tour dépend de la pression hydrodynamique et/ou hydrostatique du fluide, rendant l'ensemble des problèmes non linéaires. La rugosité de la surface à l'échelle microscopique détermine les propriétés macroscopiques de l'interaction de contact, y compris le transport de fluide le long de l'interface. La prise en compte dans les simulations numériques de la rugosité des solides en contact nous permet d'affiner notre compréhension des processus multi-physiques considérés à l'échelle macroscopique, qui est pertinente pour les applications industrielles.

Abstract :
We study a problem of thin fluid flow in contact interfaces relevant for a wide range of engineering applications and geophysical sciences. It requires resolution of a multi-field coupling of fluid and solid mechanics, enhanced by contact constraints and deterministic or randomly rough features of the surface geometry of contacting solids. We developed a monolithic finite-element framework, which includes robust contact resolution algorithms, fluid-flow elements for solving Reynolds equation for the incompressible viscous flow and fluid-structure interface elements to apply fluid pressure on the solid. Additionally, we take into account the possibility of fluid entrapment in the contact interface and its pressurization using non-linearly compressible constitutive laws and formulate a novel trapped-fluid element. The computational framework includes image analysis algorithms to distinguish between contact, fluid flow and trapped fluid zones and is suitable for both one- and two-way coupling approaches. First, the behaviour of a pressurized fluid trapped between deformable solid with a wavy surface and a rigid flat was studied. We showed how the evolution of the real contact area and of the global coefficient of friction under increasing external load depend on material properties of the fluid, as well as on that of the solid, and on the slope of the surface profile. The opening of the trap by the fluid in presence of friction was also analysed. The proposed framework was also used to study the fluid flow in the interface between a rigid flat and a deformable solid with a model geometry or random self-affine rough surface. We derived an approximate analytical solution for the fluid flow across a wavy contact interface, which was compared with our numerical results. Finally, we showed that for a range of physically relevant parameters, one-way coupling underestimates the interface permeability and the critical external load needed to completely seal the interface, compared to the two-way approach. A refined phenomenological law for macroscopic permeability of rough contact interfaces was proposed.

Titre anglais : Coupling mechanical frictional contact with interfacial fluid flow at small and large scales
Date de soutenance : mercredi 20 mars 2019 à 14h00
Adresse de soutenance : 60 Boulevard Saint-Michel, 75006 Paris, France – L213
Directeurs de thèse : Georges CAILLETAUD, Vladislav YASTREBOV

Contact : 
andrei.shvarts@mines-paristech.fr