The vibro-modulation technique is a potential NDT method which involves monitoring the amplitude modulation of an ultrasonic vibration field transmitted through a cracked specimen undergoing an additional low frequency structural vibration (typically one of the first structural modes). If the specimen is undamaged and appropriately supported, the two vibration fields do not interact. However if a crack is present then the low frequency structural vibration slowly opens and closes the crack. This periodically modifies the dynamic characteristics of the system thereby modulating the amplitude of the ultrasound transmitted through a cracked specimen. This project is investigating the physics of the phenomenon, and the practical potential for its exploitation for NDT.

Diagram showing the method employed in vibroacoustic modulation


Duffour, P., Morbidini, M. and Cawley, P. 'Comparison between a type of vibro-acoustic modulation and damping measurement as NDT techniques', NDT&E International, Vol 39, pp123-131, 2006.

Duffour, P., Morbidini, M. and Cawley, P. 'A study of the vibro-acoustic modulation technique for the detection of cracks in metals', J Acosut Soc Am, Vol 119, pp1463-1475, 2006.