This technical letter report (TLR) provides a summary of the study that was conducted at PNNL over the past 2 years. The TLR is organized with Section 2.0 providing the objectives and scope of the work. Section 3.0 describes common CASS material types and the specific specimens evaluated. The experimental setup, data acquisition protocol, and PA probes are presented in Sections 4.0 and 5.0. Section 6.0 presents the ultrasonic data acquisition and analyses conducted. The measurements performed on the sound field images include a measure of scatter, partitioning, and beam redirection. Additionally, various experimental parameters are evaluated and correlated to the sound field measurements in this section. Lastly, a discussion and conclusions are presented in Section 7.0 with references listed in Section 8.0. Supporting documentation is provided in Appendices A through E. The objective of this sound field mapping exercise is to relate ultrasonic inspection parameters or variables to phased array ultrasonic beam formation capabilities in CASS materials where the materials have been characterized by grain type, orientation, and size. The materials were measured for mean grain size as well as maximum grain size in cross-sectional slices from each specimen. In order to better understand the impacts of the CASS microstructures on sound field coherence and propagation, phased array ultrasonic beam formation was characterized in terms of beam scatter, partitioning, and redirection. The effects of the input ultrasonic inspection parameters such as probe center frequency and refracted and skew angles are discussed with respect to the specimen microstructure as they all relate to beam formation. Also examined was the ability to focus the sound field at the intended target. Lastly, suggested guidelines for a more effective evaluation of CASS components are presented.
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