Experimental investigation of modulation types in modulation transfer tests

Abstract

Damage detection methods based on phenomena from non-linear acoustics are valuable tools. Among the range of techniques, there is a diagnostic method based on the Modulation Transfer phenomenon. It involves the transfer of modulation from an amplitude-modulated wave to a non-modulated wave in the presence of damage. This paper is dedicated to investigating types of modulation related to Modulation Transfer and its applicability to fault localization. The algorithm was proposed to extract amplitude and frequency modulation-related components from the response signal. To quantitatively describe the phenomena under study, two damage index types were introduced. Experiments were performed on a damaged beam, where excitation was introduced from two sources: A low-frequency amplitude-modulated one from the modal range and a high-frequency one from the ultrasound range. The structure response was measured using non-contact methods via a laser vibrometer. The presented experimental results reveal that the modulation transfer phenomenon allows damage localization. In addition, improved localization results were observed for indicators calculated from signals with separated amplitude and frequency modulation.