Ultrasonic Inspection Techniques for Strongly Scattering and Additively Manufactured Materials

Authors

• Geoffrey R. Soneson, University of Nebraska-LincolnFollow

First Advisor

Joseph A. Turner

Second Advisor

Qilin Guo

Committee Members

Eveline Baesu, Bai Cui

Date of this Version

5-2026

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Mechanical Engineering and Applied Mechanics

Under the supervision of Professors Joseph A. Turner and Qilin Guo

Lincoln, Nebraska, May 2026

Professor Joseph A. Turner and Professor Qilin Guo

Comments

Copyright 2026, Geoffrey R. Soneson. Used by permission

Abstract

Ultrasonic nondestructive evaluation (NDE) is widely used to characterize microstructure and material properties, but challenges remain when applying ultrasonic techniques to strongly scattering materials, where double and multiple scattering can lead to misinterpretation of grain size and material properties. In this thesis, the capabilities of ultrasonic techniques are investigated through experimental and analytical approaches. The first portion focuses on quantifying higher-order scattering in backscatter measurements using single element transducers (SETs) and phased array ultrasonic transducers (PAUTs). Experiments conducted over a range of frequencies, material paths, and materials are analyzed using instantaneous time domain (ITD) and joint time-frequency analysis. Within these domains, a dimensionless broadening ratio, , is introduced to identify transitions between single and higher-order scattering regimes in ultrasonic backscatter measurements. Results show that increasing frequency and material path increases the contributions of higher-order scattering in SET measurements, while PAUT measurements are largely dominated by attenuation and higher-order scattering. Building upon these ideas, ultrasonic techniques are also applied to additively manufactured (AM) and hybrid-AM components. PAUT sector scans are first utilized to measure directional wave speeds from angled internal surfaces within AM AlSi10Mg NIST bridges, demonstrating the effectiveness of sector scans relative to SETs. A complementary finite element model is then used to approximate residual stress distributions in the bridge prior to removal from the build plate. Following this, spatially resolved maps of wave speed, attenuation, and diffuse backscatter are obtained for hybrid-AM 316L stainless steel samples fabricated using laser powder bed fusion, with varying levels of ultrasonic peening. These measurements are used to evaluate the effects of ultrasonic peening on residual stress, grain structure, and material properties, as reflected in the ultrasonic response. Overall, this work establishes a structured approach for applying and interpreting ultrasonic measurement techniques in strongly scattering and AM materials. By improving upon the abilities to detect variations in residual stress and microstructure, this work supports safer and more efficient validation of critical components across aerospace, automotive, nuclear power, and many other industries.

Advisors: Joseph A. Turner and Qilin Guo