The interaction of waves with matter strongly depends on the frequency of these waves and on the scale of their wavelengths relative to the properties of the medium under consideration. In the context of ultrasonic imaging applications that are of interest to us, the relevant length scales for metals are generally on the order of millimeters (from tenths to several tens of millimeters). Depending on the manufacturing processes used, metallic media—often anisotropic—may also exhibit microstructures with heterogeneities of similar characteristic dimensions. As a result, ultrasonic waves propagating through metals can, under certain circumstances, be significantly affected by these microstructures. This may hinder some ultrasonic techniques (due to attenuation or structural noise), or conversely, offer an opportunity to estimate local properties of the inspected metal.

The general objective of the proposed PhD thesis is to deepen the understanding of the relationship between microstructure and ultrasonic wave behavior for broad classes of materials, leveraging the combined expertise of LEM3 in virtual microstructure generation and CEA in ultrasonic wave propagation simulation.

The proposed work will combine the acquisition and analysis of experimental data (both material and ultrasonic), the use of simulation tools, and statistical data processing. This will enable an analysis of wave behavior across material classes, and possibly the development of inversion procedures to characterize a microstructure based on ultrasonic datasets. The combination of these methods will support a holistic approach, contributing to significant advancements in the field.