Speaker: Joseph Turner, Robert W. Brightfelt Professor of Mechanical and Materials Engineering at the University of Nebraska
Title: Ultrasonic Characterization of Microstructure with Applications for Hybrid Additive Manufacturing of Metals
Abstract: In this presentation, the prospects for ultrasonic characterization of microstructures of samples created using hybrid metal additive manufacturing (AM) are discussed. High-frequency ultrasound has been shown to be sensitive to microstructural parameters including grain size, the grain size distribution, grain morphology, and grain texture such that the sensitivity is available to provide a means to quantify the material state at any given time. The structural performance of metals is governed in large part by the organization of the microstructure within the sample. Properties such as strength, hardness, fracture toughness, and fatigue life are critical to component safety such that they must be controlled during manufacturing. Metal AM is an exciting new approach that allows innovative designs to be realized that are beyond the scope of more traditional processes. In addition, hybrid AM integrates secondary processes, such as laser peening or machining, within the AM process stream to influence material behavior at the local scale. While metal AM offers a growing number of new manufacturing opportunities, many challenges remain especially in the context of microstructure control. The role of ultrasonic measurements for both in situ and ex situ inspections of hybrid metal AM samples will be reviewed with respect to their ability to differentiate the microstructural organization within samples and across an ensemble of samples created using nominally identical build conditions. Finally, new predictive models based on DREAM.3D synthetics will be described with respect to ultrasonic predictions that can be made for much more complex microstructures. The production of quality metal AM samples will require a suite of characterization tools and ultrasonic methods will likely play a critical role in this exciting new field.
Bio: Joseph A. Turner is currently the Robert W. Brightfelt Professor of Mechanical and Materials Engineering and Director of the Nano-Engineering Research Core Facility (NERCF) at the University of Nebraska-Lincoln (UNL). He received his B.S. (Eng. Sci.) and M.Engr. (Eng. Sci. Mech.) degrees from Iowa State University and his Ph.D. (Theoretical and Appl. Mech.) from the University of Illinois at Urbana-Champaign (UIUC). After a postdoctoral experience at UIUC, he served as an Alexander von Humboldt Postdoctoral Fellow at the Fraunhofer Institute for Nondestructive Testing (IZFP) in Saarbrücken, Germany before joining UNL. He is a Fellow of the Acoustical Society of America and recipient of the Wilhelm Bessel Forschungspreis from the Alexander von Humboldt Foundation. His expertise in ultrasonic scattering has applications for many types of microstructures including those found in additively manufactured metals and is the focus of his QUISP (Quantitative Ultrasonics for Inspection and Structural Prognosis) group. His TULiPS (Transforming our Understanding of Living Polymer Systems) group is focused on biopolymers including those in plant and animal cells.
Seminar Host: Pete Collins