| proposition sujet thèse ]PhD thesis in collaboration with industrial partners of the automotive industry: "Role of the friction material in the mechanisms of disc brake squeal noise"Scientific and industrial context
Most of the common systems in cars generate a braking force by pressing friction materials against a rotating disc. Noise generated by the brake system is unwanted; especially squeal noise with sound pressure levels greater than 80 dB at a frequency of several kHz. Squeal noise is found to originate from an unstable behavior of the system due to the friction-induced vibration corresponding to one or several natural frequencies of the brake. Considering the contact conditions, by means of experimental investigations on real brake systems, it may be established that the material formulation and the geometry of the friction pad strongly influence the occurrence of squeal noise. The misunderstanding of the role of the friction material on the release of the instabilities is the main lack to clear the mechanisms leading to squeal.
This PhD thesis will be focus on that point and will be performed in collaboration with two industrial partners in the car passenger domain.
The research activities will be theoretical as well as experimental. The means used are already developed for the greater part. The work will be done at the lab and in the units of the industrial partners.
Goals of the PhD thesis and strategy
The main objectives of the project are to identify relevant parameters of the contacting surfaces in squeal occurrence; to link these parameters to the friction material formulation and process; and to develop friction models allowing capturing the essential phenomena of squeal occurrence.
The global strategy is to consider step by step the different length scales. First the influence of the global contact force distribution on the dynamic instabilities will be considered, by varying the geometry of the pad. The effect of contact distribution at the surface and of the normal and tangential properties at the contacting surfaces will then be studied in order to identify relevant parameters on squeal occurrence. Last part is to link these parameters to the properties and formulation of the friction material.
In order to limit the complexity of the problematic, which is multiscale and multiphysic, the geometry of the brake will be simplified as far as the friction material composition and process.
The work will be equally divided in three parts: experiments on the facilities of the industrial partners and the lab, material and surface analysis at the lab, theoretical and numerical developments at the lab.
Profile of the candidate
Engineer school or MSc in the field of mechanics and mechanics of materials. Theoretical knowledge in vibrations. Interest for experiments and for understanding of physical mechanisms involved in friction.
| proposition sujet thèse ]Sujet de thèse : Acoustique non linéaire & bétonCe sujet donne lieu au financement par le Ministère de l’Education Nationale, de l’Enseignement Supérieur et de la Recherche, d’une allocation de recherche d’une durée de trois ans, attribuée sur concours.
Contacter le ou les Directeur(s) de thèse et préparer un dossier avant la date limite du 3 mai 2010.
Pour plus d’information sur les conditions d’éligibilité et d’attribution, veuillez consulter le site de l’Ecole Doctorale des Sciences pour l'Ingénieur.
| proposition sujet thèse ]Thesis subject: Large scale organization of Turbulent Boundary LayersThe Context:
Turbulent boundary layers are a very active subject of research at the international level. Their understanding and modelling is crucial for a better design of aircraft, cars and trains in order to reduce the fuel consumption and the CO2 emission. In the last 4 years, a European funded project called WALLTURB ((http://wallturb.univ-lille1.fr), coordinated by LML and grouping 16 partners, was focussed on this subject and a follow-up proposal called ADVANTAGE, with 17 partners in Europe and Australia (including AIRBUS and DASSAULT AVIATION) is under evaluation by the European Commission. This PhD proposal is set in this context.
Laboratoire de Mécanique de Lille http://www.univ-lille1.fr/lml/ is a joint laboratory between, Université de Lille, Ecole Nationale des Arts et Métiers, Ecole Centrale de Lille and CNRS, about 80 researchers and University teachers work in the fields of Fluid Dynamics, Solid Mechanics and Civil engineering. The team hosting the Post-Doc is involved in basic turbulence (both experimental and numerical, and optical measurement techniques http://www.meol.cnrs.fr/. It is participating to European projects and networks on all these aspects. More details can be found at http://www.univ-lille1.fr/pivnet/ and http://wallturb.univ-lille1.fr/.
The subject: In the frame of the WALLTURB project, an extensive database of both experimental and numerical results on near wall turbulence was gathered by LML. This database is unique by its size, its detailed and the fact that the most advanced experimental and numerical tools were used. The aim of the thesis is, by using advanced post-processing mathematical tools (pattern recognition, spatial correlation, Proper Orthogonal decomposition, Linear Stochastic Estimation...) to extract physical understanding and characterization allowing to improve RANS (Reynolds Averaged Navier Stokes) and LES (Large Eddy Simulation) turbulence models. Focus will be put on the large scales of turbulence (of the order of 10 boundary layer thicknesses) which are not yet understood and which seem to play a significant rôle in the shear stress production at the wall. This study will be performed both for the flat plate canonical boundary layer and for a boundary layer subject to an adverse pressure gradient which is representative of the situation encountered in practice and for which turbulence models are presently giving poor predictions.
The amount is 1500 Euros per month and the employer is Ecole Centrale de Lille or CNRS.
Starting date & duration: October 2010, 36 months
Highly motivated by research in Fluid Dynamics, he has a good background in mathematics and fluid mechanics. An experience in PIV is welcome He appreciates working in a small team. He is autonomous and has initiative. He writes and speaks English fluently.