Termography based on optical techniques, in general, provide very good defect resolution. However, results are strongly affected by surface features and external factors such as non uniform heating and environmental reflections. Advanced signal/image processing is required to reduce their impact. For instance, PPT and TSR techniques allow detecting defects down to a depth of 2.5 mm, for defects having a size-to-depth ratio of approximately 2 and higher. Thermography using ultrasounds provide an interesting means for inspecting materials. It has the inconvenience of requiring a physical contact between the ultrasonic transducer and the specimen and that many experimental factors need to be addressed to obtain good results. Nevertheless, once all these factors are correctly addressed, inspection is extremely fast and results provide good defect contrast without processing. Cold image subtraction or the FFT can be used to improve contrast in some cases. Electromagnetic excitation is a relatively new field of investigation in active thermography. In this study only line inspection was used. Pulsed and modulated inductive excitations are currently under investigation.
Infrared thermography. Principle and applications to aircraft materials
Infrarotthermographie. Prinzipien und Anwendungen auf Luftfahrtwerkstoffe
2008
8 Seiten, 2 Bilder, 1 Tabelle, 21 Quellen
Aufsatz (Konferenz)
Englisch
Infrared thermography: principles and applications
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