Since a few years, millimeter-waves in the frequency range between 30 and 300GHz have been applied for nondestructive material testing. They have the advantage compared to ultrasound that no direct coupling between the probe and the object under test is required. Hence, the evaluation can be performed remotely from stand-off distance. Due to the short wave-length between 10mm and 1mm and the ability to penetrate many non-conduction materials, it is possible to find regions of structural degradation in a contactless way and with a high resolution.
The images show a case study of a Cured in Place Pipe Sample (CIPP) with artificial boreholes. This work is a collaboration between our group and the Fraunhofer IZFP (Saarbrücken).
