Ultrasonics of non-linear contacts: propagation, reflection and NDE-applications

Abstract The results of experimental investigation of acoustic non-linear phenomena on contact boundaries are presented. Simulation experiments demonstrated a threshold non-linear distortion due to ‘clapping’ and ‘kissing’ mechanisms, multiple bifurcations and chaos development for contact vibrations. Hertzian contact non-linearity was shown to increase with the decrease in contact load and to be predominated by a ‘clapping’ mechanism in a mixed mode of vibrations. Ultrasonic waves propagating on contact interfaces exhibited extremely efficient non-linear properties, unconventional higher harmonics ratio and non-linear waveform distortion. Non-linear sound reflection was accompanied by spectrum inversion, rectification and contact radiation broadening effects. Several modes of non-linear non-destructive evaluation (NDE) were proposed and shown to detect small fractured defects ‘invisible’ by linear NDE techniques.