Tittle

Multiscale computational approach for severe deformation processes in polycrystalline aggregates.

Objectives

Develop and fine-tune the macroscopic strain gradient model via microstructural computations taking the polycrystalline nature of the material into account, based on computational homogenisation methods; in particular, determination of characteristic lengths of the gradient models.

Host institution

Mines Paritech + Safran (FRANCE)

Job offer

The PhD student will work on a finite deformation crystal plasticity model implemented in the implicit finite element code Zset (common code for MAT-SAF). She/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.

Available codes : Implicit finite deformation crystal plasticity, Implicit gradient of cumulative slip crystal plasticity model at finite deformation. Implicit homogenized polycrystal model at finite deformations (Zset).

Codes to be produced : Explicit finite deformation crystal plasticity, Implicit and explicit Curl-based strain gradient crystal plasticity model. Explicit homogenized polycrystal model at finite deformations.

Collaboration

Secondment

10 months across Europe

• 4 months LTU (Sw) (05/2019-08/2019)
• 2 months ESI (Fr) (08/2020-09/2020)
• 4 months UPV-EHU (Sp) (10/2020-01/2021)

Timeline

Qualifications

• Excellent master degree in mechanical engineering, material science, computer science or related disciplines.
• Strong interest in material science and working knowledge in the field of metallic alloys.
• 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.

apply for this job

• Send your CV and a cover letter to the following address:

ESR4-APPLICATION@ENABLE-PROJECT.COM

• Please put in the object of your email that your are applying for the ESR4 position.
• Please check that you meet all eligibility criteria.