Post-Doctorants


Offre de post-doctorat au LaMCoS (INSA-Lyon) dans le cadre du projet MELTED au LAMCOS, INSA-Lyon (10/03/2017)

Sujet : Développement d’un outil numérique pour le pilotage virtuel des procédés de fabrication additive métal par réduction de modèles

Personnes à contacter :
Nawfal BLAL, MCF, LaMCoS (nawfal.blal@insa-lyon.fr)
Thomas ELGUEDJ, MCF HDR LaMCoS (thomas.elguedj@insa-lyon.fr)
Arnaud DUVAL, IR CNRS , LaMCoS (arnaud.duval@insa-lyon.fr)

Contexte :
MELTED (MaîtrisE de la quaLiTé des piècEs issues de fabrication aDditive) est un projet financé par l’Institut CARNOT i@L rassemblant différents partenaires académiques et industriels de la région Lyon-Saint-Étienne. Il est dédié aux technologies de fabrication additive de type SLM (Selective Laser Melting) et DMD (Direct Metal Deposition) pour des matériaux métalliques, technologies qui permettent de fabriquer des matériaux innovants sur mesureavec de hautes performances et valeurs ajoutées. Dans l’objectif de mieux prédire la qualité des pièces obtenuespar ces procédés, il est important de bien appréhender l’influence des différents paramètres mis en jeu (puissance laser, vitesse de balayage, débit de poudre…). Des simulations numériques prédictives nécessiteraient des temps de calculs coûteux à cause des aspects non-linéaires et multi-physiques. Le recours à des simulations en temps réel s’avère ainsi prometteur, efficace et permettrait un gain considérable en temps de calcul et in fine un pilotage en temps réel de ces procédés.

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Offre de Post-Doctorat au LMA ou au LAMCOS à Marseille (02/03/2017)

Missions principales
Sur la base d’un modèle thermomécanique des TTS développé par le laboratoire LMA dans le code éléments finis Aster (thèse de Grégory ANTONI en 2010), les travaux consistent à :

1. Mettre en œuvre le modèle développé et optimiser les algorithmes d’intégrations numériques associés
2. Valider ce modèle numérique à travers une batterie de tests numériques
3. Confronter ce modèle numérique à des essais expérimentaux qui seront réalisés au sein du laboratoire LAMCOS
4. Proposer des axes d’amélioration du modèle en concertation avec l’équipe d’encadrement

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Post-doctoral position in computational mechanics – ENS Cachan (02/11/2016)

Required Education / Niveau requis : PhD in computational mechanics / applied mathematics
From / Date de début : right away
Duration / Durée : 2 years
Salary : 3136 euros gross per month

Context / Contexte
Domain decomposition methods are well established approaches for solv ing large scale problems on parallel computers. In the field of solid mechanics, non-overlapping approaches such as FETI (Finite Element Tearing and Interconnecting) and BDD (Balancing Domain Decomposition) are recognized as the methods of choice. Given the current trend of increasing computational power by increas ing the number of cores, the adaptation and tuning of these approaches is essential in order to maintain their parallel efficiency while employing large numbers of cores.

Description / Description
In domain decomposition methods, the domain associated with the partial differential equation is decom posed into a possibly large number of subdomains. Local problems are then defined on each subdomain and are solved at each iteration step in order to approximate the inverse of the system’s matrix (stiffness matrix in mechanics for instance). It must be noticed that, in order to obtain a n efficient and scalable parallel algorithm, a coarse problem has to be introduced and solved at each iteration step. Given the evolution of parallel computers to higher core counts, the number of subdomains grows (say several thousands and beyo nd) so that sizes of the local (subdomain) stiffness matrices are reduced. On the one hand, t his notably accelerates the local treatments (mainly factorization of the stiffness matrices). On the other hand, this increases the dimension of the null space and solving the coarse problem will then turn out to constitute a major computational cost. The goal of the post-doctoral internship is to deal with this new challenge by studying novel techniques to solve and approximate the subdomain and the coarse grid problems, and to devise asynchronous scheduling and suitable load balancing strategies. The goal of the project is to help engineers as well as scientists to benefit from the performance of parallel computers with very large number of cores.

Industrial partnership / Partenariat industriel
The post-doctoral position takes part in a wider industrial partnership through the nationally funded project PAMSIM (PArallélisme Massif en SImulation numérique pour la Mécanique aka Massive Parallelism for the Numerical Simulation in Solid Mechanics). In addition to CERFACS, the consortium includes the R&D division of EDF, the LMT laboratory of ENS Cachan and several participating starts-up.

Contact : Ulrich RUEDE, ulrich.ruede@cerfacs.fr

Post-doctoral position en Vibro-acoustique – Université de Cambrige (30/09/2016)

A position exists, for a Research Assistant/Associate in the Department of Engineering, to work on a project funded by the EPSRC concerning the use of experimental data in computational models of noise and vibration. Despite the availability of sophisticated mathematical and computational modelling techniques, some components in a built-up structure can be so complex that it is not possible to produce an ab initio computational model of the whole system, and hence some degree of physical testing is unavoidable. This project will consider how experimental testing can be best performed and utilised in advanced vibro-acoustic models; the experimental work will be based at the University of Salford, while the theoretical and computational work (the current position) will be based at Cambridge. The project has industrial partners (Bentley Motors Ltd, Bruel and Kajaer, Dyson Ltd, and Wave Six LLC) and liaison with these partners will be required throughout the project.

Candidates must have, or be close to obtaining, a PhD in Structural Dynamics.  Expertise in vibration theory and computational methods is a requirement, and some experience of experimental testing is highly desirable.

The post holder will be located in Central Cambridge, Cambridgeshire, UK.

Salary Ranges: Research Assistant: £25,023 – £28,982, Research Associate: £28,982 – £37,768.

Fixed-term: The funds for this post are available until 31 May 2019 in the first instance.

Once an offer of employment has been accepted, the successful candidate will be required to undergo a health assessment.

http://www.jobs.ac.uk/job/AOQ395/research-assistant-associate-in-vibration-and-acoustics/

Post-doctoral fellowship proposal at the Laboratoire de Mecanique des Sols, Structures et Materiaux (MSSMat) CentraleSupelec, CNRS « Coupling of numerical solvers for large-scale wavepropagation from source to structure »  (15/09/2016)

Scientific context and objectives

The Spectral Element Method (SEM) is currently very popular for large-scale wave propagation in geophysics, while the Finite Element Method (FEM) is much more widely used for vibration of structures in the context of Earthquake Engineering. This implies in particular that the two communities have developed efficient and validated solvers based on these two methods for their respective cases of interest. These cases of interest consider in particular non-linearities in the mechanical behavior (both for the soil and the structure) and uncertainties in the mechanical parameters. When aiming at computing the full seismic wave propagation path, from the fault to the structure, a natural approach would consist in coupling a SEM solver for the ground and a FEM solver for the structure. However, the space  discretization is different for the two methods (larger elements for high order methods). Likewise, the classical time discretization for the SEM is explicit with very small time steps, while it is implicit for the FEM, with larger time steps. These issues must be mitigated by appropriate numerical treatment at the interface or through a coupling volume. When considering wave propagation over large numbers of processing cores, the questions of synchronous computation and load balancing are essential, and will be of constant concern. The post-doctoral candidate will propose novel approaches for the coupling between SEM and FEM solvers (here SEM3D and Code Aster), and implement them in a High Performance Computing environment.
(…)

Research position

  • Duration : 1 year, plus possible renewal for 1 year.
  • Location : The applicant will join the MSSMat laboratory (http://www.mssmat.ecp.fr), located on the campus of CentraleSupelec, in Ch^atenay-Malabry, France.
  • Net Salary : 2200 euros net per month (possibilities for cheap housing close to campus available upon request).

Qualifications
We seek for candidates with excellent skills in numerical methods and computational science.
An experience in mechanics or wave propagation would be appreciated, but not compulsory.

Application
Applicants should send their curriculum vitae and statement of interest, or questions, to

postdoc_coupling_SINAPS

Post-doctoral position IFPEN « Optimisation des paramètres d’une loi matériau élasto-viscoplastique utilisée en calculs de structure » (12/07/2016)

Présentation du sujet :
La production pétrolière reste la première source d’énergie pour les transports et la chimie, et les pétroliers cherchent en permanence à repousser les limites technologiques actuelles pour garantir la production d’hydrocarbures. Cet enjeu impose une meilleure connaissance des matériaux utilisés et notamment leur comportement en condition d’utilisation.
Dans ce contexte, IFPEN travaille depuis plusieurs années sur la tenue mécanique de la gaine en polymère soumise à un environnement sévère associé à une pression élevée de fluide ou de gaz, ainsi qu’à une température élevée. Un modèle de comportement mécanique permettant de prédire l’évolution du comportement élasto-viscoplastique de ce type de matériau a été mis au point. Ce modèle de comportement a été implémenté dans un code de calculs de structure par la méthode des éléments finis et a fait ses preuves pour prédire la déformation de plusieurs grades de polymères semi-cristallins pour différents états de contraintes multiaxiales subis par la structure flexible en service.
Cependant, dans un contexte économique concurrentiel, il devient nécessaire de valider l’utilisation des structures de plus en plus rapidement et facilement. Il est donc nécessaire pour les matériaux polymères semi-cristallins de :
• Disposer d’une loi de comportement robuste sous des sollicitations toujours plus extrêmes en terme de pression et de température.
• Disposer d’une méthodologie simple d’identification des paramètres de la loi de comportement IFPEN quel que soit le grade de matériau polymère d’intérêt.

Profil du candidat :
Le candidat devra avoir une double compétence Maths/Méca, voire une thèse en mécanique des solides ou sciences des matériaux, avec une compétence forte en optimisation et en programmation (Matlab, programmation en C++/Fortran). La connaissance d’un logiciel de
calculs Eléments Finis sera appréciée (AbaqusTM). Il devra être autonome, pragmatique et ouvert d’esprit.

Lieu :
IFP Energies nouvelles 1-4 avenue de Bois Préau, 92852, Rueil-Malmaison Cedex, FRANCE

Encadrants / Contacts :
Direction Mécanique Appliquée : Dr E. Roguet (eleonore.roguet@ifpen.fr)
Direction Mécatronique et Numérique : Dr Frédéric Delbos (frederic.delbos@ifpen.fr)

Offre en français

Offre en anglais

Post-Doctoral position: « Domain decomposition method for the computation of the effective elastic tensor of random materials », Ecole des Ponts ParisTech (28/06/2016)

Supervisors:
E. Cancès (CERMICS, Ecole des Ponts Paristech)
V. Ehrlacher (CERMICS, Ecole des Ponts Paristech)
F. Legoll (Laboratoire Navier, Ecole des Ponts Paristech) | frederic.legoll@enpc.fr | http://navier.enpc.fr/LEGOLL-Frederic

Keywords:
random materials, homogenization, parallel computation, domain decomposition.

The aim of this project is to develop an efficient and original numerical method to compute the effective elastic properties of random heterogeneous materials.

We focus on heterogeneous elastic materials containing small inclusions embedded in a matrix. We assume that these inclusions are randomly distributed in the material. The effective elastic properties of the material are then deterministic, and their computation by a full-field method requires the resolution of an auxiliary problem defined over the entire space. Classical methods consist in considering a large (but finite) statistical elementary volume, on which the auxiliary problem, complemented with appropriate boundary conditions (for instance, periodic boundary conditions), is solved.

In this project, we consider another type of auxiliary problem, defined over the whole space, where the statistical elementary volume is embedded in an exterior infinite homogeneous material. The new problem, which has initially been introduced in a completely different setting, can be seen as a generalization of the Eshelby problem. In some previous work, we have shown, in collaboration with Benjamin Stamm (Aachen university, Germany), how such auxiliary problems can be used to approximate the effective thermal conduction properties.

In this project, the candidate will extend the range of application of the method in order to (i) compute the effective properties of polydisperse materials, (ii) compute the effective mechanical properties of microstructured materials (only thermal problems have been considered until now), …

Announcement.pdf