Turning 3D Grain Maps into a Finite Element Mesh

Researchers describe a methodology for coupling diffraction contrast tomography and the finite element method.

Modern beamlines at synchrotron facilities allow the observation of structural materials’ three dimensions (3D). By adding diffraction information, it is possible to retrieve the 3D spatial arrangement of the crystallographic grains composing polycrystalline metallic specimens. Dedicated meshing routines are developed to use the real 3D grain microstructure for finite element calculations. This is particularly important in many industrial problems involving plasticity of metals where the local anisotropy of the material resulting from its grain microstructure has to be accounted for.

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Researchers from Evry (France), Koege (Denmark), Lyon (France) and Grenoble (France) describe a methodology for coupling diffraction contrast tomography and the finite element method. Finite element simulations are carried out using experimental microstructures to predict their deformation behavior. Two examples using 3D experimental grain maps are presented. The first one deals with a pure titanium sample with about 1400 grains. The finite element calculation using elastic anisotropy and accurate boundary conditions allows the correct capturing of the grain to grain elastic strain variations. In the second example, a significantly larger zone of a polycrystalline Al-Li sample is meshed and computed using elastoplastic finite strain calculations.

Crystal plasticity allows the capture of the mean lattice reorientations and intra-grain lattice orientation as a function of macroscopic deformation. This could be compared to experimental measurements for several grains in the future, paricularly with near-field topo-tomography experiments, to observe in situ and simulate the early stage of plastic deformation in bulk grains of a metallic specimen.

In summary, turning experimental 3D microstructures into input for finite element calculations is a promising way to complement the rising 3D techniques related to polycrystalline materials. It may provide complete mesoscale information to study the deformation and fracture of structural materials in the near future.

 

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