Research On Acoustic-modulation Method For Structural Health Monitoring Of Aluminum Alloy

Aluminum alloy structure is widely used in various engineering equipments. Ifthe structure damage is un-prevented, it can cause equipment damage and othercatastrophic accident. To ensure structure health and operational safety, it is importantto research the technique about damage detection at an early stage. That is one part ofStructural Health Monitoring (SHM).Acoustic Modulation is a method using nonlinear ultrasonic. The method has theadvantage of simple theory and high sensitivity. This paper takes aluminum alloystructure as object and is based on the physical mechanism of Acoustic Modulation,the Acoustic Modulation method and experimental work of detection the earlystructure damage is studied. The main work includes:(1) Analysis the physical mechanism of Acoustic modulation phenomena. Thesolid medium nonlinear acoustic wave equation is deduced based on the stress strainconstitutive relation. Explained the theory of why damage lead to Acousticmodulation phenomena. Established the inner link between the damage variable,nonlinear coefficient and the ultrasonic response characteristics.(2) Research on signal processing analysis algorithm for Acoustic modulation.According to the modulation characteristics of the Acoustic modulated signal.Analysis the applicability of EMD and EEMD in the decomposition ofmulti-component signal. Then design a combination method of EEMD and AM-FMalgorithm for complex signal demodulation.(3) The simulation experiment of Aluminum alloy structure’s damage. Underengineering application background, built a measurement system of Acousticmodulation on the basis of surface bonded piezoelectric ceramics, and make anexperimental study of crack detection based on Acoustic Modulation technique inplate-like structure and tubular structure.(4) The verification of Acoustic Modulation signal processing and early damagedetection. Verify Acoustic Modulation method for structure damage detection viaexperimental work; and analysis the coupling character of Acoustic Modulation signalbase on the signal processing analysis algorithm.Research shows: the signal exist both amplitude modulation and frequencymodulation when there are damage on the structure; Acoustic Modulation technique can effectively detect the fatigue crack of Plate-like metal.and crack of tubularstructure.