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Modelling and simulation of ultrasound scattering mechanisms in WLAM components with a view to multiscale characterization
The scattering of elastic waves in polycrystalline materials is a physically interesting phenomenon that is widely exploited in the field of Non-Destructive Testing (NDT). Polycrystalline materials often exhibit complex morphological and crystallographic variations, leading to fluctuations in acoustic impedance. Individual grains, each characterized by their own elastic anisotropy, can be misoriented relative to the sample reference frame, resulting in different types of macroscopic anisotropy. This thesis focuses on nickel-based superalloy produced by Wire Laser Additive Manufacturing (WLAM), a process that often yields a microstructure characterized by columnar grains and a pronounced macroscopic fiber texture. For ultrasonic characterization, it is essential to understand the correlation between the coherent waves and the microstructure under investigation. The multiple scattering of elastic waves by the grains are commonly quantified in terms of the wave amplitude attenuation, phase velocity dispersion and backscattered noise. In this thesis, theoretical and numerical models are developed to investigate the influence of WLAM-specific microstructural features on elastic wave amplitude attenuation and phase velocity dispersion. The theoretical and numerical results together provide an in-depth analysis showing that attenuation and phase velocity dispersion exhibit a strong directional dependence in fiber-textured and elongated microstructures. These findings offer valuable insights for ultrasonic characterization of the polycrystalline microstructures typical of WLAM-produced components. The developed frameworks provide a physically consistent basis for analyzing elastic wave scattering in virtually any type of polycrystalline material.
Composition du jury :
- Arnaud DERODE, Rapporteur & Examinateur, Professeur, ESPCI Paris, Institut Langevin
- Christopher KUBE, Rapporteur & Examinateur, Associate Professor, Pennsylvania State University
- Michael LOWE, Examinateur, Professor, Imperial College of London
- Claire PRADA, Examinatrice, Directrice de recherche, ESPCI Paris, Institut Langevin
- Tony VALIER-BRASIER, Examinateur, Maître de conférences, Sorbonne Université, Institut Jean le Rond d'Alembert