METHOD AND APPARATUS FOR ACOUSTIC DETECTION AND LOCATION OF DEFECTS IN STRUCTURES OR ICE ON STRUCTURES

摘要

The invention relates to a method and apparatus for nondestructive testing and evaluation of materials and mechanical structures to determine their integrity reducing contact-type flaws and presence of ice on a structure. The invention employs an ultrasonic probing signal (30) and a low frequency vibration (20) applied to a structure (8) tested. In a structure without flaws or ice, these signals propagate independently without any interaction. If the structure contains a defect or ice thereon, the vibration varies the contact area of the defect or ice/structure interface, modulating the phase and amplitude of the higher frequency ultrasonic probing signal passing through the structure (8). In the frequency domain the result of this modulation manifests itself as sideband spectral components with respect to frequency of the probe wave. This can be considered as a new signal generated by a defect, so that the defect can be detected more easily when such a signal is observed.