Vertical cracks characterization using lock-in thermography: I infinite cracks

Early detection of cracks is a challenging task to prevent failures in working structures. In the last decades the 'flying spot' method, based on heating the sample with a moving laser spot and detecting the surface temperature with an infrared detector, has been developed to detect cracks...

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Bibliographic Details
Published in:Measurement science & technology 2014-11, Vol.25 (11), p.115601-10
Main Authors: Pech-May, N W, Oleaga, A, Mendioroz, A, Omella, A J, Celorrio, R, Salazar, A
Format: Article
Language:English
Subjects:
analytical solution
crack detection
Cracks
Failure
Flaw detection
Flight
Heating
Infrared detectors
infrared thermography
nondestructive evaluation
quantification of crack width
Spots
Surface temperature
thermal waves
Thermography
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Summary:Early detection of cracks is a challenging task to prevent failures in working structures. In the last decades the 'flying spot' method, based on heating the sample with a moving laser spot and detecting the surface temperature with an infrared detector, has been developed to detect cracks in a fast manner. The aim of this work is to measure the width of an infinite vertical crack using lock-in thermography. An analytical solution for the surface temperature of a sample containing such a crack when the surface is illuminated by a modulated laser beam focused at a fixed spot close to the crack is obtained. Measurements on samples containing calibrated cracks have been performed using an infrared camera. A least square fit of the amplitude and phase of the surface temperature is used to retrieve the thickness of the crack. A very good agreement between the nominal and retrieved thicknesses of fissure is found, even for widths down to 1 µm, confirming the validity of the model.
ISSN:0957-0233
1361-6501
DOI:10.1088/0957-0233/25/11/115601