|Tipo di tesi||Tesi di dottorato di ricerca|
|Titolo||Formulazione in Complementarietà Lineare per Risolvere Problemi di Lubrificazione con Cavitazione in Regime Elastoidrodinamico|
|Titolo in inglese||A Linear Complementarity Approach to Solve Elastohydrodynamic Lubrication Problems in the Presence of Cavitation|
|Settore scientifico disciplinare||ING-IND/14 - PROGETTAZIONE MECCANICA E COSTRUZIONE DI MACCHINE|
|Corso di studi||Scuola di D.R. in HIGH MECHANICS AND AUTOMOTIVE DESIGN & TECHNOLOGY / MECCANICA AVANZATA E TECNICA DEL VEICOLO|
|Data inizio appello||2013-03-22|
|Disponibilità||Accessibile via web (tutti i file della tesi sono accessibili)|
In questa tesi viene descritta una formulazione per lo studio di problemi di lubrificazione basata sul concetto di complementarietà lineare.
This thesis describes a formulation for the analysis of lubrication problems that handles the cavitation phenomenon with the concept of linear complementarity. This formulation is based on the Reynolds equation, appropriately recasted in terms of pressure and void fraction. The correct detection of the cavitation and the location of the boundaries between cavitated and active areas is guaranteed by the complementary nature of the two chosen variables. Therefore, it is possible to describe the hydrodynamic problem all over the domain using a single equation, which is valid both in the active and in the cavitated zone. This approach naturally guarantees the mass conservation. A detailed analysis of the proposed complementary formulation of the Reynolds equation is presented, both for one dimensional and two dimensional cases. In addition, various rheological models are considered in order to simulate accurately the lubricant behaviour and properties. The Hertz contact theory has been introduced for the consideration of the elastic deflection of the contact bodies. As an alternative, it is possible to handle the elasticity of the solids by importing the compliance matrix generated by a external structural Finite Element model. This second method is suitable for the EHL analysis of various common mechanical components, such connecting rods big end and small end bearings, that cannot be satisfactorily modelled with the Hertz contact theory. A numerical method, based on the Finite Element framework, has been employed to solve the complementarity formulation of the Reynolds equation. The developed implementation is versatile and robust and does not require particular conditions on the dimensions of the elements of the mesh. The numerical development focused on the maximization of the computational speed. The proposed formulation is capable to solve efficiently a wide range of problems and to consider various rheological and elastic models. Particular advantages, with respect to standard finite difference approaches, have been found in the cases of isoviscous and rigid lubrication regimes and in the presence of steep film thickness gradients.