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SUJET POURVU - Multiscale computational approach for severe deformation processes in crystalline aggregates.

SUJET POURVU - Multiscale computational approach for severe deformation processes in crystalline aggregates.

SUBJECT OF THESIS PROVIDED - Multiscale computational approach for severe deformation processes in crystalline aggregates

Proposition de thèse

Spécialité

Mécanique

Ecole doctorale

SMI - Sciences des Métiers de l'Ingénieur

Directeur de thèse

FOREST Samuel

Co-directeur de thèse

ROOS Arjen

Unité de recherche

Centre des Matériaux

ContactSamuel FOREST
Date de validité

01/10/2018

Site Webhttp://www.mat.mines-paristech.fr/Recrutements/Theses/
Mots-clés

Crystal plasticity, Strain gradient plasticity, Large deformations, Finite element

Crystal plasticity, Strain gradient plasticity, Large deformations, Finite element

Résumé

/

The PhD student will work on a finite deformation crystal plasticity model implemented in the implicit finite element code Zset (common code for MINES ParosTech-SafranTech). He will identify the material parameters for the titanium alloy for which experimental results are available within the project, using simulations of representative volume elements of polycrystals. The model will be also implemented in an explicit code for comparison. Finite element simulations will be performed at large strains in order to investigate the possibility of remeshing and field transfer in the context of crystal plasticity.

In a second step, the crystal plasticity framework will be extended to incorporate the effect of Geometrically Necessary Dislocations (GND) that arise in the presence of strong strain gradients. Two types of strain gradient crystal plasticity models will be considered. The first one is an available strain gradient crystal plasticity model incorporating the gradient of cumulative slip in the formulation. The corresponding implicit code is already available at finite strains. This first approach will be extended to incorporate the full dislocation density tensor (GND tensor) defined as the curl of the plastic deformation field. Size effects associated with grain size and strong strain gradients induced by the loading will be investigated and compared to experimental results obtained within the project.

The last stage will be devoted to the identification of a homogenized polycrystal model at large strains from the simulations of the polycrystalline aggregates. This reduced model will be used to determine the effect of the crystallographic texture and its evolution during straining. A first version of the model is available and will be extended to incorporate suitable constitutive laws including dislocation densities and characteristic lengths deduced from the full field simulations. The results of the homogenization model will serve forthe calibration of more macroscopic models not based on crystal plasticity.

Contexte

ENABLE (European Network for Alloys Behaviour Laws Enhancement) aims to train early-stage researchers in what is referred to as an outstanding challenge for the future of manufacturing: developing novel solutions for forecasting and mastering processes relevant for all factories using metallic alloys. The project Enable is financed by the H2020 programme under the “Marie Sk?odowska- Curie ITN action”.

ENABLE proposes a complete rethink of the usual process simulation method by developing innovative multiscale, multiphysical and multi-level advanced (TRL 1 to 8) simulation. To extend the benefits to a wide range of industrial actors, the simulation will be carried out on several widely-used processes: Machining, Friction Stir Welding and Additive Manufacturing. The most popular metals in industry (Titanium, Nickel based and Aluminium alloys) will be chosen for the scientific investigation.

ENABLE will lead to the development of new tools that are better suited to production (reduced premature wear, increased service life, improved tools, etc.) and will reduce production time and thereby production costs.

A group of 9 ESR will be introduced to dynamic approaches to exploiting advances in fundamental research towards innovative applications. To
“enable” this vision, each trainee will have access to closely integrated complementarities and world-class expertise in mechanical science, materials science, computer science/numerical methods, state-of-the-art scattering, advanced equipment and significant computational resources. Additional cross-disciplinary training and a strong involvement on the part of the 12 Industries and SMEs and research centres will provide the students with transferable skills.

Encadrement

Directeur de thèse : MR FOREST Samuel - Centre des Matériaux
Co-Directeur : MR. ROOS Arjen - SAFRAN TECH

Profil candidat

Engineer and / or Master of Science - Good level of general and scientific culture. Good level of knowledge of French (B2 level in french is required) and English. (B2 level in english is required) Good analytical, synthesis, innovation and communication skills. Qualities of adaptability and creativity. Teaching skills. Motivation for research activity. Coherent professional project.

The ESR (Early Stage Researcher) may be a national of a Member State, of an Associated Country or of any Third Country.
The ESR must not have resided or carried out her/his main activity (work, studies, etc.) in the country of her/his host organization for more than 12 months in the 3 years immediately prior to her/his recruitment.
Holds a Masters degree or equivalent, which formally entitles to embark on a Doctorate.
Does not holds a PhD degree.

Excellent Master degree in mechanical engineering, material science, computer science or related disciplines
Strong interest in computational mechanics related to material science and working knowledge in the field of metallic alloys, fields measuring
Significant laboratory experience in finite element computing and coding (C++)
Strong background in plasticity theory and computation
Familiarity with lab equipment, including chemical handling procedures and attention to detail as well as environmental, health and safety (EHS) requirements
Excellent communication skills and willingness to work in collaborative projects with multiple partners
Very good English language skills
Self-motivation and the ability to achieve goals independently as well as to contribute effectively to the team

Applicants should supply the following :

- a detailed resume
- a covering letter explaining the applicant's motivation for the position
- detailed exam results
- two references : the name and contact details of at least two people who could be contacted to provide an appreciation of the candidate

to be sent to recrutement_these@mat.mines-paristech.fr

Engineer and / or Master of Science - Good level of general and scientific culture.
Good level of knowledge of French (B2 level in french is required) and English.
(B2 level in english is required)
Good analytical, synthesis, innovation and communication skills.
Qualities of adaptability and creativity. Teaching skills. Motivation for research activity.
Coherent professional project.

The ESR (Early Stage Researcher) may be a national of a Member State, of an Associated Country or of any Third Country.
The ESR must not have resided or carried out her/his main activity (work, studies, etc.) in the country of her/his host organization for more than 12 months in the 3 years immediately prior to her/his recruitment.
Holds a Masters degree or equivalent, which formally entitles to embark on a Doctorate.
Does not holds a PhD degree.

Excellent Master degree in mechanical engineering, material science, computer science or related disciplines
Strong interest in computational mechanics related to material science and working knowledge in the field of metallic alloys, fields measuring
Significant laboratory experience in finite element computing and coding (C++)
Strong background in plasticity theory and computation
Familiarity with lab equipment, including chemical handling procedures and attention to detail as well as environmental, health and safety (EHS) requirements
Excellent communication skills and willingness to work in collaborative projects with multiple partners
Very good English language skills
Self-motivation and the ability to achieve goals independently as well as to contribute effectively to the team

Applicants should supply the following :

- a detailed resume
- a covering letter explaining the applicantÂ's motivation for the position
- detailed exam results
- two references : the name and contact details of at least two people who could be contacted to provide an appreciation of the candidate

to be sent to recrutement_these@mat.mines-paristech.fr

Résultat attendu

State of the art on crystal plasticity.

Simulation of polycrystalline aggregates within classic crystal plasticity for titanium alloys.

Strain gradient crystal plasticity modelling of polycrystalline aggregates under severe loading conditions;
Formulate physically-based and thermodynamically consistent crystal plasticity constitutive equations at the grain level from the literature and experiments performed within the project.

Provide digital polycrystalline morphologies, crystallographic textures and finite-element meshes of the grains.
Implementation of constitutive models and homogenizations laws for polycrystals.

Objectif

The PhD student will work on a finite deformation crystal plasticity model implemented in the implicit finite element code Zset (common code for MINES ParisTech and Safran Tech). He will identify the material parameters for the titanium alloy for which experimental results are available within the project, using simulations of representative volume elements of polycrystals. The model will be also implemented in an explicit code for comparison. Finite element simulations will be performed at large strains in order to investigate the possibility of remeshing and field transfer in the context of crystal plasticity.

In a second step, the crystal plasticity framework will be extended to incorporate the effect of Geometrically Necessary Dislocations (GND) that arise in the presence of strong strain gradients. Two types of strain gradient crystal plasticity models will be considered. The first one is an available strain gradient crystal plasticity model incorporating the gradient of cumulative slip in the formulation. The corresponding implicit code is already available at finite strains. This first approach will be extended to incorporate the full dislocation density tensor (GND tensor) defined as the curl of the plastic deformation field. Again, implicit and explicit formulations will be proposed. Size effects associated with grain size and strong strain gradients induced by the loading will be investigated and compared to experimental results obtained within the project.

The last stage will be devoted to the identification of a homogenized polycrystal model at large strains from the simulations of the polycrystalline aggregates. This reduced model will be used to determine the effect of the crystallographic texture and its evolution during straining. A first version of the model is available and will be extended to incorporate suitable constitutive laws including dislocation densities and characteristic lengths deduced from the full field simulations. The results of the homogenization model will serve for the calibration of more macroscopic models not based on crystal plasticity.

Références

C. Ling, J. Besson, S. Forest, B. Tanguy, F. Latourte, E. Bosso, An elastoviscoplastic model for porous single crystals at finite strains and its assessment based on unit cell simulations, International Journal of Plasticity, vol. 84, pp. 58-87, 2016. doi:10.1016/j.ijplas.2016.05.001

C. Ling, S. Forest, J. Besson, B. Tanguy and F. Latourte, A reduced micromorphic single crystal plasticity model at finite deformations. Application to strain localization and void growth in ductile metals , International Journal of Solids and Structures, vol. 134, pp. 43-69, 2018. doi:10.1016/j.ijsolstr.2017.10.013

Type financement

Contrat de recherche

Partenariat/contrat

Partenaire industriel : Safran Tech within Horizon 2020 ITN Project ENABLE

Type de financement : Horizon 2020 ITN Project ENABLE

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