Mechanics of Materials and Metallurgy
The MECAMETA axis gathers most of the activities related to structural materials (mainly metallic alloys and composite materials), which we want to be more efficient, more reliable and more durable, in increasingly severe environments. In order to better understand and model the mechanical behavior of complex and heterogeneous materials, and thus better control their final properties, the work carried out is both experimental and numerical. The mechanisms involved (plasticity, damage, phase transformations, ….) being non-linear and active at different scales, it is necessary to use or develop advanced tools in the fields of :
- elaboration and thermo-mechanical transformations: the MECAMETA axis is now very involved in the elaboration of new alloys and microstructures based on powders (SPS and HIP), of materials architected by additive manufacturing, or in the mastery of non-standard shaping methods (asymmetric rolling);
modeling and simulations that can now range from molecular dynamics to finite element calculations, including discrete dislocation dynamics, phase field methods, and homogenization.
- Experimental analysis using the means gathered in the scientific services, in which we find a great diversity of scales of microstructural characterization by XRD, AFM, SEM, TEM and mechanical characterization thanks in particular to a set of mini-machines adaptable on SEM, AFM and XRD, for various tests (traction, compression, bending, shearing), in various ranges of temperatures according to the types of tests (until 800°C).
In addition to these studies, the axis also contributes (in partnership with other teams) to studies aiming, on the one hand, at the modeling of the mechanical behavior of functional materials (in thin layers for example) and the prediction of their coupled properties and, on the other hand, at the functionalization of structural materials. It is also in constant dialogue with the common scientific services. It is also developing very strong partnerships at the regional (LABEX SEAM, CNRS F2MSP and FERMI federations), national (CEA, etc.), international (ITER consortium, USA, Poland, Algeria, Japan) and industrial (FUI and ANR projects with the energy, defense, transport and aeronautics industries in particular) levels.
FFT modeling of the phase transformation and the associated plasticity during the cooling of two-phase steels with a heterogeneous banded structure after hot rolling. Austenite (in red) develops from pearlite bands on the one hand and from ferrite grains on the other.
Collaboration R. Brenner (IJLRDA) and Nippon Steel Corporation (Japan).
Otsuka et al, Mater. Sci. Techn. in 2019, 35, 187-194.
Example of a very large pure titanium crystal obtained by a grain growth method coupling critical strain hardening and thermal cycling.
Photo reconstructed from several SEM images).
Chaubet et al, J. Physics, Conf. Series, 2019, 1270 012045.
Development and validation of a methodology for measuring residual stresses in highly anisotropic materials (titanium alloys in particular). Simulation by homogenization of a tensile test on titanium and extraction at each step of the macroscopic elastic deformation perpendicular to a given crystallographic plane (which can be measured by XRD). Calculation of the residual stresses from these strains, using the standard methodology (treatment of a single plane) or using data from several planes. Calculation of an error parameter (right). This error is considerably reduced by performing a multi-plane analysis and taking into account the anisotropy of the material.
(1) elastic loading, (2) elasto-plastic loading, (3) unloading, and (4) elastic reloading