Modelling of the ultrasonic propagation in polycrystalline materials

International audience; In some polycrystalline materials, ultrasonic non destructive testing is affected by structural noise and attenuation. Those phenomena can cause significant loss in detection performances. Thus, the presence of a microstructure is a limiting factor of ultrasonic inspection capabilities and it must be accounted for when designing new NDE methods. Modelling work has been underway at CEA-LIST in the software CIVA to describe attenuation, structural noise and beam distortions appearing when a wave propagates in a heterogeneous medium such as a polycrystalline material. The objective is to develop new simulation tools based on metallurgical data input. To achieve this goal, a theoretical model relating ultrasonic scattering to properties of the microstructure and its integration to existing algorithms, allowing us to compute structural noise and attenuation from material properties is proposed. Further numerical study and comparisons with experimental results have been performed to study the influence of the type of structure (simple or duplex), the shape (equiaxed or elongated) and the size of grains.