PhD defence of David Ruiz

7 December 2020

David Ruiz defends his PhD in Numerical Mechanics and Materials on Dec. 7th, 2020.

"Full field modeling of discontinuous dynamic recrystallization in a CPFEM context"

David Ruiz Sarrazola conducted his PhD work under the supervision of Marc Bernacki  (MSR team) in the framewwork of the  Industrial ANR Chair DIGIMU.

He will defend his thesis work in Numerical Mechanics and Materials in front of this jury:

– Pr. Laurent DELANNAY (Univ. Catholique de Louvain, Louvain-la-Neuve, Belgique)

– Pr. Lukasz MADEJ (AGH Univ. of Science and Tech., Krakow, Pologne) 

– Assoc. Prof. Roland LOGÉ (Ecole Polytechnique Fédérale de Lausanne, Lausanne, Suisse)

– Pr. Javier SIGNORELLI (Inst. de Fisica Rosario, Santa Fé, Argentine)

– Privat Dozen Franz ROTERS (Max-Planck-Institut für Eisenforschung, Düsseldorf, Allemagne)

– M.R. Daniel PINO MUÑOZ (MINES ParisTech-CEMEF, Sophia Antipolis)

– C.R. Aurore MONTOUCHET (Framatome Creusot, Le Creusot)

Abstract of his work:

Dynamic recrystallization (DRX) is one of the main metallurgical phenomena responsible for the evolution of the microstructure of metallic materials subjected to hot metal forming processes. Understanding and predicting the subsequent physical mechanisms is of prime importance as the resulting microstructure will be directly responsible of the final in-use material properties. Thus, numerous phenomenological models (JMAK type for example) aiming to describe DRX have been developed in the state of the art. However, because of the complexity of the mechanisms involved in DRX and their interactions, phenomenological or mean field models are not able to fully account for the local evolution of the microstructure and full field approaches are required generally when precise calculations are aimed. Most DRX full field models have limitations in their ability to model high deformation (which limits their applicability for real industrial thermomechanical treatments) and in their description of plastic deformation (which is often grossly simplified).
 
In this PhD, a new full field  discontinuous DRX (DDRX) model is proposed by coupling a crystal plasticity finite element method (CPFEM) with  a level-set finite element (LS-FE)  framework to describe the grain boundary network motion. The proposed model considers anisotropic plastic deformation and its impact on grain boundary motion. Combined with a remeshing methodology, the proposed numerical framework is capable of describing DDRX up to very large deformation levels. The model is calibrated and compared against experimental measurements of 304L steel. Moreover, the interest of this strategy (ratio precision/numerical cost) is also discussed comparatively to a simpler approach (CP Taylor approximation). All these developments are realized in a generic CPFEM module easily usable in any FE code. 
 
Keywords: Dynamic recrystallization, Full field model, Crystal plasticity, Level-set, Finite element method, 304L Steel.
 

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