PhD Defense of D. Ruiz

The PhD defense will take place in CEMEF Mines ParisTech on the 07th of December. These PhD works are dedicated to the « Full-field modeling of discontinuous dynamic recrystallization in a CPFEM context ».

A brief summary below:

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.

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