Contact and Noncontact Nonlinear/Linear Resonance Ultrasound Spectroscopy (N/RUS) of Additively Manufactured and Wrought 316L Stainless Steel Samples
Open Access
- Author:
- Bozek, Evan
- Graduate Program:
- Engineering Science and Mechanics
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 21, 2022
- Committee Members:
- Albert Segall, Program Head/Chair
Parisa Shokouhi, Thesis Advisor/Co-Advisor
Clifford Jesse Lissenden, III, Committee Member
Jacques Riviere, Thesis Advisor/Co-Advisor - Keywords:
- Ultrasound
NRUS
Additive Manufacturing
Resonance
Non-contact - Abstract:
- Additive manufacturing (AM) is becoming increasing popular owing to its ability to manufacture geometrically complex parts and produce customer-designed parts faster than traditional machining. One of the challenges of creating high quality AM parts is that the AM process often produces defects that are difficult to detect. A number of techniques have been used to evaluate the quality of AM parts, such as traditional ultrasonic testing and x-ray micro computed tomography (micro-CT) scans. These methods are not ideal, as traditional ultrasonic testing can require multiple tests to evaluate the entire part, while micro-CT has difficulty detecting small defects in large parts. Resonance-based ultrasonic methods have the advantage of only requiring one testing configuration to evaluate the entire part. Nonlinear resonance ultrasound spectroscopy (NRUS) is a resonance-based nondestructive testing (NDT) technique for material characterization that is especially sensitive to small-scale imperfections such as microscopic cracks. Previous NRUS tests have shown correlations between the parameters measured by NRUS and the fatigue life (fatigue endurance) of a small set of samples, indicating the potential of NRUS for evaluating the build quality of AM parts as related to their performance. However, these measurements on AM metals show large variability due to the experimental setup used. Typical NRUS tests involve bonding the sample to an excitation source that induces vibration in the sample. Unfortunately, the bonding introduces artifacts in the measurements leading to the observed large measurement variability. In this study, we seek to evaluate the use of non-contact excitation sources for NRUS testing with the goal of improving the measurement repeatability. We compare the NRUS measurements using contact and non-contact excitations on wrought and AM 316L stainless steel samples with several different heat treatments. This study suggests the improved repeatability of linear resonance frequency measurements when using an air-coupled transducer. However, the intensity of resulting excitations is not sufficient for NRUS measurements, which require higher excitation voltages. We propose two additional approaches for non-contact NRUS measurements: one using a high-power laser and the other using an air cavity.