In recent years, an innovative vibro‐modulation technique has been introduced for the detection of contact‐type interfaces such as cracks, debondings, and delaminations. The technique utilizes the effect of nonlinear interaction of ultrasound and vibrations at the interface of the defect. Vibration varies the contact area of the interface, modulating a passing ultrasonic wave. The modulation manifests itself as additional side‐band spectral components with the combination frequencies in the spectrum of the received signal. The presence of these components allows for the detection and differentiation of the contact‐type defects from other structural and material inhomogeneities. The vibro‐modulation technique has been implemented in the N‐SCAN® damage detection system providing a cost effective solution for the complex NDT problems. N‐SCAN® proved to be very effective for damage detection and characterization in structures and structural components of simple and complex geometries made of steel, aluminum, ...
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