Doctoral Dissertations

Keywords and Phrases

Active Microwave Thermography; Defect Indication; Defect Quantification; Microwave Heating; Nondestructive Testing and Evaluation; Spatiotemporal Variance Reconstruction

Abstract

Active microwave thermography, or AMT, is a coupled electromagnetic-thermographic nondestructive testing and evaluation technique. AMT has found success in a variety of inspection needs in the aerospace, space, and infrastructure fields due to its unique type of thermal excitation. During an AMT inspection, a specimen is exposed to microwave energy from a radiating source (i.e., an antenna). This exposure to microwave energy results in dielectric/magnetic heating, which causes an increase in temperature and potential defect indications to manifest on an inspection surface (which is measured via an infrared camera). Due to the use of an antenna, there is a spatially nonuniform thermal increase which is related to the radiated spatially nonuniform power density. It has been found that this nonuniform heating leads to potential false positives and/or false negatives during interpretation of inspection results. Traditionally, this has been remedied through a variety of solutions such as referencing the results to a known and defect-free measurement, modulating the control signal, offsetting the electromagnetic excitation (and hence the heating) from the inspection area, etc. However, each of these approaches have drawbacks and thus alternative approaches are needed. To this end, this work proposes novel signal processing and image reconstruction approaches that do not require a reference, a-priori knowledge of the defect, nor additional instrumentation. These novel approaches are compared to traditional approaches both qualitatively and quantitatively, with improvements evident as a result. Additionally, these approaches are applied to a variety of specimens containing defects that vary in cross-section, depth, location, and quantity, with successful detection and quantification in all cases.

Advisor(s)

Donnell, Kristen M.

Committee Member(s)

Johnson, Catherine E.
Chandrashekhara, K.
Esmaeelpour, Mina
Ghasr, Mohammad Tayeb Ahmad, 1980-
Watkins, Steve Eugene, 1960-

Department(s)

Electrical and Computer Engineering

Degree Name

Ph. D. in Electrical Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2025

Journal article titles appearing in thesis/dissertation

Paper I, found on pages 8-47, “Modified Thermographic Signal-to-Noise Ratio for Active Microwave Thermography,” has been published in Volume 73 of the IEEE Transactions on Instrumentation and Measurement (TIM) in January 2024.

Paper II, found on pages 48-83, “Adaptive Polynomial Regression for Active Microwave-Thermographic Signal Reconstruction,” has been published in Volume 4 of the IEEE Open Journal on Instrumentation and Measurement (OJIM) in September 2025.

Paper III, found on pages 84-121, “Spatiotemporal Variance Image Reconstruction for Thermographic Inspections,” has been published in Volume 3 of the IEEE Open Journal on Instrumentation and Measurement (OJIM) in November 2024.

Paper IV, found on pages 122-137, “Improved Spatial Resolution of Spatiotemporal Variance Reconstructed Thermographic Images,” is under review in the IEEE Open Journal on Instrumentation and Measurement (OJIM).

Pagination

xiii, 146 pages

Note about bibliography

Includes_bibliographical_references_(pages 144-145)

Rights

© 2025 Logan Martin Wilcox , All Rights Reserved

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12581

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