Ultrasonic testing for metal additive manufacturing: Experience with new course development

Abstract

Metal additive manufacturing (AM) has brought about the need for nondestructive evaluation (NDE) methods to assess part quality. AM processes result in complex microstructures, porosity, material texture, and residual stresses all of which may vary spatially throughout the part. Thus, knowledge of ultrasonic NDE methods to characterize materials is relevant to the AM community. To address this challenge, a new graduate-level course entitled “Ultrasound for Metal Additive Manufacturing,” was created at the University of Nebraska-Lincoln. The course followed a cognitive-situative blended learning approach to give students practical ultrasonics training regardless of prior acoustics background. The theory introduced key topics including: the general wave equation, plane wave solutions, waves in isotropic solids, impact of material anisotropy, role of material interfaces, reflection and transmission, surface waves, scattering, dispersion, material dissipation, and scattering attenuation. A series of laboratory experiments allowed students to learn: experimental setups, signal processing, transducer properties and selection, beam mapping, wave speed and attenuation measurements, and diffuse-field measurements. Finally, each student developed a project incorporating ultrasound measurements into their individual AM research. Their findings were included in research articles, conference presentations, and PhD dissertations. This presentation will describe the course design, successes, and recommendations for future implementations.