The proposed thesis falls into the framework of designing innovative methods in the materials characterization. The thesis aims to develop a new tomographic technique for characterizing microstructures using bulk laser ultrasound. In the state of the art, acoustic methods such as the scanning acoustic microscope and surface wave optoacoustic spectroscopy lead to grain imaging but only at the surface of the sample. However, industrial manufacturing processes (in metallurgy, welding, additive manufacturing...) can reveal spatial inhomogeneity of the microstructure, such as grain size gradients with depth within the component. Electron backscatter diffraction (EBSD) also provides surface imaging of grains but has disadvantages, including restriction on sample size and the need to make transversal cuts through the sample to image its volume.
The proposed idea is to develop a bulk laser ultrasound tomography technique able to determine the grain size in areas of a component or even to obtain imaging of large-grain microstructures and a local determination of crystallographic orientation. Therefore, the thesis's main objective will be to design such an experimental characterization tool and optimize its design using a digital twin to develop.