Author
Sebastian Thiele
Bio: Sebastian Thiele is an academic researcher from Georgia Institute of Technology. The author has contributed to research in topics: Z-scan technique & Harmonic. The author has an hindex of 3, co-authored 5 publications receiving 151 citations.
Papers
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TL;DR: This research presents a new technique for nonlinear Rayleigh surface wave measurements that uses a non-contact, air-coupled ultrasonic transducer; this receiver is less dependent on surface conditions than laser-based detection, and is much more accurate and efficient than detection with a contact wedge transducers.
72 citations
TL;DR: A method for extracting the nonlinearity parameter β11 is proposed based on a nonlinear least squares curve-fitting algorithm that is tailored for Rayleigh wave measurements and improves upon conclusions drawn from previous analysis.
60 citations
TL;DR: In this article, the effects of copper precipitates on the acoustic nonlinearity parameter of 17-4PH stainless steel were investigated using nonlinear ultrasonic measurements using Rayleigh waves, consistent with evidence of copper precipitation from hardness, thermo-electric power, transmission electron microscopy and atom probe tomography measurements.
Abstract: This research is part of a broader effort to develop a nondestructive evaluation technique to monitor radiation damage in reactor pressure vessel steels, the main contributor being copper-rich precipitates. In this work, 17-4PH stainless steel is thermally aged to study the effects of copper precipitates on the acoustic nonlinearity parameter. Nonlinear ultrasonic measurements using Rayleigh waves are performed on isothermally aged 17-4PH. Results showed a decrease in the acoustic nonlinearity parameter with increasing aging time, consistent with evidence of copper precipitation from hardness, thermo-electric power, transmission electron microscopy, and atom probe tomography measurements.
45 citations
01 Jan 2014
TL;DR: In this paper, a precipitate hardenable material namely 17-4 PH stainless steel is thermally treated to obtain different precipitation stages, and then the influence of precipitates on the acoustic nonlinearity parameter is assessed.
Abstract: Nonlinear ultrasonic waves have shown to be sensitive to various microstructural changes in metals including coherent precipitates; these precipitates introduce a strain field in the lattice structure. The thermal aging of certain alloy steels leads to the formation of coherent precipitates, which pin dislocations and contribute to the generation of a second harmonic component. A precipitate hardenable material namely 17–4 PH stainless steel is thermally treated in this research to obtain different precipitation stages, and then the influence of precipitates on the acoustic nonlinearity parameter is assessed. Conclusions about the microstrucutural changes in the material are drawn based on the results from a nonlinear Rayleigh surface wave measurement and complementary thermo-electric power, hardness and ultrasonic velocity measurements. The results show that the nonlinear parameter is sensitive to coherent precipitates in the material and moreover that precipitation characteristics can be characterized b...
4 citations
01 Jan 2016
TL;DR: In this paper, the authors proposed a nuclear power system for the nuclear power sector based on the work of the G W Woodruff School of Mechanical Engineering at the Georgia Institute of Technology.
Abstract: James J, Wall, Laurence L Jacobs, Jin-Yeon Kim, Kathryn H Matlack, Sebastian Thiele, Katherine M Scott, Alexander J Lakocy and Christoph Doerr, Nuclear Sector, Electric Power Research Institute, Charlotte, NC USA; G W Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA USA; School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA USA; Mechanics and Materials, ETH-Zurich, Zurich, Switzerland
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TL;DR: In this article, the authors present a comprehensive review of the current state of knowledge of second harmonic generation (SHG) measurements, a subset of nonlinear ultrasonic non-destructive evaluation techniques.
Abstract: This paper presents a comprehensive review of the current state of knowledge of second harmonic generation (SHG) measurements, a subset of nonlinear ultrasonic nondestructive evaluation techniques. These SHG techniques exploit the material nonlinearity of metals in order to measure the acoustic nonlinearity parameter, $$\beta $$
. In these measurements, a second harmonic wave is generated from a propagating monochromatic elastic wave, due to the anharmonicity of the crystal lattice, as well as the presence of microstructural features such as dislocations and precipitates. This article provides a summary of models that relate the different microstructural contributions to $$\beta $$
, and provides details of the different SHG measurement and analysis techniques available, focusing on longitudinal and Rayleigh wave methods. The main focus of this paper is a critical review of the literature that utilizes these SHG methods for the nondestructive evaluation of plasticity, fatigue, thermal aging, creep, and radiation damage in metals.
271 citations
TL;DR: In this paper, the main results of research in the field of non-linear ultrasonic wave investigations for the inspection of fatigue damage, thermal damage and chemical damage are highlighted for the first-stage damage.
104 citations
TL;DR: In this paper, the evolution of nano-precipitates and their effects on the mechanical properties of 17-4 precipitation hardening stainless steel (17-4 PH SS) aged at 450 °C were investigated by high-resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT).
82 citations
TL;DR: In this article, the microstructure of a Cu-bearing 15-5PH steel is thoroughly characterized along the precipitation heat treatment, using a combination of transmission electron microscopy with phase and orientation mapping, atom probe tomography, in-situ small-angle X-ray scattering and Xray diffraction.
79 citations