Identification of heat source distribution in vibrothermography

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2014
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Vaddi, Jyani S.
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AIP Publishing LLC
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Holland, Stephen
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Aerospace Engineering

The Department of Aerospace Engineering seeks to instruct the design, analysis, testing, and operation of vehicles which operate in air, water, or space, including studies of aerodynamics, structure mechanics, propulsion, and the like.

History
The Department of Aerospace Engineering was organized as the Department of Aeronautical Engineering in 1942. Its name was changed to the Department of Aerospace Engineering in 1961. In 1990, the department absorbed the Department of Engineering Science and Mechanics and became the Department of Aerospace Engineering and Engineering Mechanics. In 2003 the name was changed back to the Department of Aerospace Engineering.

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1942-present

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  • Department of Aerospace Engineering and Engineering Mechanics (1990-2003)

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Center for Nondestructive Evaluation

The Center for Nondestructive Evaluation at Iowa State has been involved in the use of nondestructive evaluation testing (NDT) technologies to: assess the integrity of a substance, material or structure; assess the criticality of any flaws, and to predict the object’s remaining serviceability. NDT technologies used include ultrasonics and acoustic emissions, electromagnetic technologies, computer tomography, thermal imaging, and others.

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In October of 1985 the CNDE was approved by the State Board of Regents after it had received a grant from the National Science Foundation (NSF) as an Industry/University Cooperative Research Center.

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Abstract
Vibrothermography is a nondestructive evaluation method for finding cracks in materials using vibration induced heat generation. The specimen is subjected to high energy resonant vibrations and the heat generated at the crack is imaged with an infrared camera. Because of the uneven crack face morphology and closure stresses, the heat generation is not uniform across the crack length. Additionally, thermal diffusion in solids blurs the image and makes the heat source identification even harder. Therefore, the quantification of crack heating in vibrothermography is highly subjective. Some researchers define it as a measure of temperature rise, some use the infrared camera reading in arbitrary units to define it and some use the total power dissipated at the crack. In this paper, we propose an algorithm that hypothesizes the crack as a series of arbitarily located line sources and estimates the locations and intensities of each of these sources. We calculate the radius and amplitude at every point in the heated region using a curve fitting procedure and feed this as the input to our algorithm, which then estimates the source locations and intensities. The algorithm uses non-linear least squares optimization to minimize the mean square error between estimated and measured temperature distribution. The resulting source distribution can be used to estimate the thermal power dissipated in heating the crack.
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This proceeding may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This proceeding appeared in Vaddi, Jyani S., and Stephen D. Holland. "Identification of heat source distribution in vibrothermography." In AIP Conference Proceedings, vol. 1581, no. 1, pp. 1639-1643. American Institute of Physics, 2014, and may be found at DOI: 10.1063/1.4865020. Copyright 2014 AIP Publishing LLC. Posted with permission.
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