LGF Seminar – Jean-Lin Dequiedt – June 16, 2026

An LGF seminar will take place on Tuesday, June 16, 2026, at 2:00 PM in room J3.03, presented by Jean-Lin Dequiedt, Research Engineer at CEA DAM, invited by Guillaume KERMOUCHE.

Title

Crystal plasticity and phase transformations: Multi-scale approach and some applications

Jean-Lin DEQUIEDT^a,b, Christophe DENOUAL^a,b, Ronan MADEC^a,b, Nicolas BRUZY^a,b

^a CEA, DAM, DIF, F-91297 Arpajon, France
^b Université Paris-Saclay, CEA, LMCE, F-91680 Bruyères-le-Chatel, France

Abstract

The plastic deformation of metallic single crystals is driven by the activation of slip planes favorably oriented with respect to the loading. Under dynamic loading and high pressure, certain crystalline structures also undergo twinning and displacive phase transformations. A crystal plasticity law based on physics at the smallest scales has been continuously developed and improved at CEA/DAM for about twenty years. It uses dislocation densities per slip system as internal variables; the interaction matrix between systems is derived from Dislocation Dynamics calculations [1] and the associated hardening law is validated using tensile tests on single crystals available in the literature. Phase transformations are modeled using a reaction-path phase-field approach [2]. These various formalisms are integrated into the Coddex simulation code, which was developed for this purpose and allows for characterizing the response of single crystals and aggregates to given loadings.

During this presentation, several completed or ongoing studies will be illustrated. The first concerns the segregation of slip systems in single crystals and the link with the interaction matrix [3]. The second focuses on necking in a polycrystalline plate under extension [4]. The third addresses the behavior of HCP beryllium polycrystals as a function of active slip system families and the introduction of a first twinning system.

[1] Madec, R., Kubin, L., 2017. Dislocation strengthening in FCC metals and in BCC metals at high temperatures. Acta Mater., 126, 166-173.

[2] Bruzy, N., Denoual, C., Vattré, A., 2022. Polyphase crystal plasticity for high strain rate: application to twinning and retwinning in tantalum. J. Mech. Phys. Solids, 166, 104921.

[3] Dequiedt, J.L., Denoual, C., Madec, R., 2015. Heterogeneous deformation in ductile FCC single crystals in biaxial stretching: the influence of slip system interactions. J. Mech. Phys. Solids, 83, 301-318.

[4] Dequiedt, J.L., Denoual, C., 2021. Localization of plastic deformation in stretching sheets with a crystal plasticity approach: competition between weakest link and instable mode controlled process. Int. J. Solids Struct., 210-211, 183-202.