Post-doctoral Positions: Old


Post-Doctoral position at LEM3 (CNRS UMR 7239) – Metz – France
in the framework of Labex DAMAS (Lorraine University)

Development of advanced micromechanical models to capture elasto-plastic anisotropic effects on the mechanical properties of polycrystalline Ti-alloys

Description

Scientific context: Titanium alloys are used in the aerospatial industry for critical components (rotating parts in engines, landing gears, breaks …) often loaded under high cycle fatigue or creep. During the last decades, considerable research allowed a better understanding of the link between microstructure and properties and lead to a better control of the forging process. However, the anisotropy and heterogeneities of titanium parts are still difficult to take into account for a reliable prediction of in service mechanical properties. Such heterogeneities lead locally to deformation incompatibilities that act as crack initiation sites and reduce the overall performances of the material [1].

Objectives of the post-doc (12 months+ possibility 12 extra months after first year)
The objective of the present project proposed by the LabEx « DAMAS » (http://www.labex-damas.com/) is to develop innovative numerical approaches able to predict the local and overall behaviors of Ti alloys during tension and fatigue. Such modeling considers both the microtextural heterogeneities and elasto-plastic anisotropies. These new developments will be based on micromechanical models and reconstruction algorithms developed at LEM3 (UMR CNRS 7239, University of Lorraine). Two main tasks will be investigated during the scheduled total post-doc duration (2 years)

(1) Synthetic microstructures (in 2d and 3d) using the DREAM3d software or own algorithms will be developed accounting progressively the complexity of α/β Ti alloys. First, a 100% β microstructure with different grain morphologies and different textures and micro-textures will be examined. Second, a 100% α microstructure with different topological and morphological distributions for macrozones will be studied. Lastly, two-phase α / β with Burgers orientation relationship will be investigated.

(2) Micromechanical approaches will be developed to predict the mechanical properties of α/β Ti alloys under tensile or cyclic deformations. These models will be applied to the different synthetic microstructures developed in the first task to understand stress variations within the microstructure and quantify the weakest configurations at the origin of crack nucleation.

– The global effects of crystallographic texture and grain morphologies on the mechanical effective elastoviscoplastic behaviors of such alloys will be first investigated with a recently developed mean field EVPSC model based on Translated Fields (Elasto-Visco-Plastic Self-Consistent scheme) developed for polycrystalline metals using an « affine extension » [2].

– The statistical effects of grain to grain elastic/plastic incompatibilities and the influence of elastic anisotropy on these incompatibilities especially for the β phase will be investigated by full field Elasto-visco-plastic Fast Fourier Transform calculations adapting the EVPFFT approach [3] to such Ti-alloys. These numerical simulations will benefit from a collaboration with the Los Alamos Nat. Lab. /USA (R.A. Lebensohn).

– A recent bicrystalline model [4] will be also exploited to statistically quantify the incompatibility stresses as functions of elastic anisotropy, crystal and grain boundary orientations. These results will serve to quantify the locations of strong internal stress concentrations where cracks are supposed to appear in the more complex industrial microstructures.

References :
[1] E. Uta E., N. Gey, P. Bocher, M. Humbert, J. Gilgert , ‘Texture Heterogeneities in Titanium Forging analyzed by EBSD – Relation to Fatigue Crack Propagation’, Journal of Microscopy, Vol.233, Issue 3, 2009
[2] C. Mareau, S. Berbenni, An affine formulation for the self-consistent modeling of elasto-viscoplastic heterogeneous materials based on the translated field method. International Journal of Plasticity, Vol. 64, pp. 134-150, 2015.
[3] R. A. Lebensohn, A. K. Kanjarla, P. Eisenlohr, ‘An elasto-viscoplastic formulation based on fast Fourier transforms for the prediction of micromechanical fields in polycrystalline materials, International Journal of Plasticity, Volumes 32–33, May 2012, Pages 59–69
[4] I. Tiba, T. Richeton, C. Motz, H. Vehoff, S. Berbenni. Incompatibility stresses at grain boundaries in Ni bicrystalline micropillars analyzed by an anisotropic model and slip activity. Acta Materialia, Vol. 83, pp. 227-238, 2015.

Application: The candidate will have a high Ph.D. level in Mechanics of Materials and a good experience in multiscale modeling, numerical simulations like FEM, FFT, Crystal Plasticity, Homogenization, as well as good programming skills (Fortran, Matlab, C++…).

Duration: 12 months (renewable for a year) – Net salary: ~2218 euros/month – Starting date: October 1st, 2015

Contacts: Interested persons qualified for this position are invited to send their application before the 15th of September 2015 (Motivation and a Curriculum Vitae including a PhD report, a list of publications, a short description of your past and current research activities) to the following contact email addresses:

Dr. Stéphane Berbenni :Stephane.Berbenni@univ-lorraine.fr

Dr. Lionel Germain : Lionel.Germain@univ-lorraine.fr

Dr. Nathalie Gey : Nathalie.Gey@univ-lorraine.fr

 

January 15, 2015

Mechanical behaviour of a β-metastable titanium alloy in the β->α+β phase transformation temperature range

The present post-doctoral position will take place at Institut Jean Lamour (CNRS–Université de Lorraine, http://ijl.univ-lorraine.fr), within the research group “Microstructures et Contraintes”. It will be funded by the Laboratory of Excellence (Labex) DAMAS, (Design of alloy metals for low-mass structures).

Duration: 12 months from March 2015. The post-doc duration can be extended to 18 months.

Profile: PhD in Materials Science (metallurgy, titanium alloys, etc..).

Skills: Experimental characterisation of mechanical behaviour.

Application: Please send your CV and your cover letter to: julien.teixeira@univ-lorraine.fr.

Contact: Dr Julien Teixeira julien.teixeira@univ-lorraine.fr +33 3 83 58 42 25

PDF File

PD2102014

Title of research: Growth of drops from a liquid film

Application: The position is for 12 months, starting as soon as possible. The applicant must hold a PhD degree in either Engineering or Physics and should have experience in Computational Fluid Dynamics (with a first experience in programming). Knowledge in free surface flows would be advantageous and knowledge of the French language would be appreciated.

Applications should include a detailed CV, a cover letter, and the contact details of two potential referees. Applications should be sent to pierre.chapelle@univ-lorraine.fr.

 

Title of research: Developpement of 3D microscopy for advanced microstructural characterization

  • Receiving laboratory: Laboratory of Excellence ‘DAMAS’ (Design of Alloy Metals for low-mAss Structures)
  • Mentor(s): Nathalie GEY
  • Duration: 24 months
  • Desired starting date: January 2014
  • Contact person: Nathalie GEY nathalie.gey@univ-lorraine.fr
  • Phone: +33 (0)3 87 31 53 85

Title of research: Multiscale study of heterogeneity and anisotropy of plastic deformation using acoustic emission and local extensometry

  • Receiving laboratory: Laboratoire d’Étude des Microstructures et de Mécanique des Matériaux (LEM3), CNRS UMR 7239
  • Mentor(s): Dr. Mikhail LEBYODKIN
  • Duration: 12 months
  • Desired starting date: May 2014
  • Contact person: Dr. Mikhail LEBYODKIN mikhail.lebedkin@univ-lorraine.fr
  • Phone: +33 (0)3 87 31 53 66

Title of research: Nouvelles méthodes d’analyse multi-échelle en présence d’instabilités au niveau local

  • Duration: 1 year | Desired starting date: as soon as possible.
  • Research objective: Il s’agit de mettre au point une nouvelle méthode multi-échelle de type « éléments finis au carré (FE2)» lorsqu’ il y a une bifurcation au niveau local, puis de la valider numériquement. La théorie repose sur une technique classique de projection et permet de définir d’une part un problème local à solution unique et d’autre part un problème global bien posé.
  • Monthly net income: € 2,210
  • Mission: Le chercheur aura en charge la définition du modèle théorique, de sa mise en œuvre numérique et de sa validation.
  • Qualifications: Les candidat-e-s doivent avoir de fortes compétences en calcul scientifique et en mécanique des milieux continus. Une expérience en modélisation multi-échelle est souhaitable.
  • Context of work: La recHerchu era faite au sein de l’équipe Mécanique Numérique du Laboratoire d’Etude des Microstructures et de Mécanique des Matériaux, sous la responsabilité du professeur Michel Potier-Ferry et en collaboration avec le Laboratoire de Mécanique et Génie Civil de Montpellier (Saied Nezamabadi).
  • Contact person: Prof. Michel POTIER-FERRY
    michel.potier-ferry@univ-lorraine.fr +33 (0)3 87 31 53 84

Title of research: Microstructural study of the bainitic transformation in carbonitrided steels

Title of research: Study of Nitrogen Distribution in Nitrided alloys: Atom Probe Tomography

  • Receiving laboratory: Institut Jean Lamour, IJL, Nancy + Groupe de Physique des Matériaux (GPM), Unité Mixte de Recherche (UMR) at Universitǩ de"Ruen
  • Mentor: Prof. Abdelkrim REDJAÏMIA
  • Duration: 1 year | Desired starting date: September 2013
  • Contact person: Prof. Abdelkrim REDJAÏMIA
    abdelkrim.redjaimia@ijl.nancy-universite.fr+33 (0)3 83 58 41 90

Title of research: Development of numerical tools for analysis of 3D EBSD microstructures

  • Receiving laboratory: LEM3
  • Mentors: Dr. Lionel GERMAIN (LEM3), Dr. Nathalie GEY (LEM3)
  • Duration: 6 months | Desired starting date: 01/09/2013
  • Keywords: titanium alloys, high energy welding, microstructure, residual stress, properties.
  • Scientific description:
    The LEM3 aims to investigate microstructures in 3D coupled with orientation data from EBSD. The tools required to analyze such data are at best under development or not existing at all. The mission of the postdoc is to help us in developing those tools. The work involves programming skills and a good understanding of materials and EBSD data.
  • Contact person: Dr. Lionel GERMAIN, Lecturer
    lionel.germain@univ-lorraine.fr+33 (0)3 87 31 53 89

Title of research: Microstructural changes in dissimilar Ti alloys induced by high energy welding

  • Receiving laboratory: LEM3
  • Mentors: Prof. Eric FLEURY and Dr. Jérôme SERRI (LEM3), Dr. Julien ZOLLINGER (IJL)
  • Duration: 1 year | Desired starting date: September 2013
  • Keywords: titanium alloys, high energy welding, microstructure, residual stress, properties.
  • Contact person: Prof. Eric FLEURY
    eric.fleury@univ-lorraine.fr+33 (0)3 87 31 53 25

Title of research: Measurement and analysis of the kinetics of evaporation under vacuum