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1 April 2003 Frequency-modulated elastic wave thermography
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Ultrasound excited thermography allows for defect selective imaging using thermal waves that are generated by elastic waves. The mechanism involved is local friction or hysteresis which turns a dynamically loaded defect into a heat source which is identified by a thermography system. If the excitation frequency matches to a resonance of the vibrating system, temperature patterns can occur that are caused by standing elastic waves. This undesirable patterns can affect the detection of damages in a negative way. We describe a technique how the defect detectability of ultrasound activated thermography can be improved. With the objective of a preferably diffuse distributed sonic field we applied frequency modulated ultrasound to the material. That way the standing waves can be eliminated or reduced and the detectability is improved.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Thomas Zweschper, Gernot Riegert, Alexander Dillenz, and Gerhard Busse "Frequency-modulated elastic wave thermography", Proc. SPIE 5073, Thermosense XXV, (1 April 2003);

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