The examples have shown that lockin thermography phase images are insensitive to inhomogeneous excitation. Such images provide fast and reliable results on large measurement areas within a short time since mechanical scanning is not needed. Defect depths can be probed via modulation frequency. These are the reasons why lockin thermography methods are of increasing interest for inspection of aircraft and aerospace components. Obviously a wide range of applications is covered using suitable excitation methods. Based on these results some future developments are being considered: 1. Data fusion for feature extraction and for identification of defects is well applicable to Lockin thermography images that are taken at the same relative orientation between camera and inspected object so that there is no need of measuring surface topography. This is important for maintenance inspection. 2. Thermal wave inspection is also feasible by combining optical shearography with the lockin technique so that thermal wave are imaged via the modulated thermal expansion going along with them. Depth range is almost twice the one of infrared surface temperature inspection, the measurement time is comparable due to thermal wave propagation and the price is just a fraction of lockin thermography. Fig. 13 compares results obtained with OLT, ULT and lockin shearography (LS) on a CFRP sample with partial stringer disbond.
Aerospace applications of lockin thermography with optical, ultrasonic and inductive excitation
Raumfahrtanwendungen der Lock-In-Thermographie mit optischer, Ultraschall- und induktiver Anwendung
2009
8 Seiten, 13 Bilder, 21 Quellen
Conference paper
Storage medium
English
Lockin-thermography for nondestructive evaluation of aerospace structures
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