Crack detection using Non- Linear Wave Modulation Spectroscopy

Abstract: This report comprises an investigation of the non-linear ultrasonic crack detection method; Non-Linear Wave Modulation Spectroscopy, NWMS. Cracks in test objects were according to the NWMS method detected through their non-linearity. The non-linearity was observed as sum and difference frequencies for an ultrasonic signal interacting with a low frequency signal in the test objects. A test setup and test procedure was developed and an Excel program for a rational suggested quantification of non-linearity was written. The method was applied and evaluated on cracked and non-cracked rotor blades for jet engines.