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J. Imaging 2015, 1(1), 220-248; doi:10.3390/jimaging1010220

Detection and Characterization of Defects in Isotropic and Anisotropic Structures Using Lockin Thermography

Federal Institute for Materials Research and Testing (BAM), Unter den Eichen 87, D-12205 Berlin, Germany
These authors contributed equally to this work.
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Academic Editor: Carosena Meola
Received: 23 October 2015 / Revised: 8 December 2015 / Accepted: 11 December 2015 / Published: 21 December 2015
(This article belongs to the Special Issue The World in Infrared Imaging)
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Abstract

Lockin thermography is a well-suited method for the characterization of structures made of both metal and fiber reinforced plastic. In most cases, only phase images are analyzed, although the amplitude images might contain useful information as well. Thus, systematic studies of lockin thermography are presented, assessing amplitude and phase images for the detection and quantification of defects in isotropic (steel) and anisotropic (carbon fiber reinforced plastic) materials. Characterized defects are flat bottom holes with different diameters and various remaining wall thicknesses as well as crossed notches at different depths. The excitation frequency was varied while keeping the number of analyzed excitation periods nearly constant for each material. The data analysis was focused on the detectability of the defects both in the amplitude and phase images, including the determination of the signal-to-noise ratio and of the spatial resolution. As a result, the limits of defect detectability and spatial resolution are given for each material. View Full-Text
Keywords: lockin thermography; non-destructive testing; steel; Carbon Fiber Reinforced Plastic (CFRP); amplitude images; phase images; Signal-to-Noise Ratio (SNR); lateral resolution lockin thermography; non-destructive testing; steel; Carbon Fiber Reinforced Plastic (CFRP); amplitude images; phase images; Signal-to-Noise Ratio (SNR); lateral resolution
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Maierhofer, C.; Myrach, P.; Krankenhagen, R.; Röllig, M.; Steinfurth, H. Detection and Characterization of Defects in Isotropic and Anisotropic Structures Using Lockin Thermography. J. Imaging 2015, 1, 220-248.

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