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Flying-spot lock-in thermography and its application to thickness measurement and crack detection

: Netzelmann, Udo

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12th International Conference on Quantitative InfraRed Thermography, QIRT 2014. Online resource : 7-11 July 2014, Bordeaux, France
Bordeaux, 2014
Paper QIRT-2014-064
International Conference on Quantitative InfraRed Thermography (QIRT) <12, 2014, Bordeaux>
Conference Paper, Electronic Publication
Fraunhofer IZFP ()
flying-spot thermography; lock-in thermography; sheet forming; crack detection; wall thinning

A heating laser beam was scanned periodically along a testing path on the surface of a test object. The thermal response of the beam was recorded by an infrared camera. Using a lock-in thermography algorithm, amplitude and phase images were generated. The phase image is corrected for effects due to the beam movement. A first application shows the contact-free determination of the steel sheet thickness at forming edges. Calibration of phase values to thickness was achieved by using an analytical model of thermal wave transmission. A second application is the detection of a perpendicular surface crack in steel.