Frequency-Wavenumber Domain Analysis In Lamb Wave Structure Damage Monitoring

The structure health monitoring technology based on Lamb wave has been a hot topic in recent years all over the country.As a real-time,online and effective non-destructive monitoring method,it plays a vital role in ensuring the safety of the structure.In the structure health monitoring system based on the Lamb wave.Due to the multi-mode,dispersion characteristics of Lamb wave and the mode conversion problem caused by the interaction with the damage during propagation in the board.the wave packet is expanded and deformed,and the amplitude decreases.This phenomenon will become more and more obvious as the propagation distance increases,which seriously reduces the resolution and signal-to-noise of the sensor signal.In this paper,a dispersion compensation method based on Lamb wave frequency-wavenumber curve is studied and used to improve the imaging resolution.The research work of this thesis was illustrated as follow:(1)The research background and contents of structural health monitoring are given.Focusing on the main measures and application fields of frequency-wavenumber domain analysis for Lamb wave structural health monitoring.Secondly,the research of frequency-wavenumber domain processing is discussed.(2)Discuss the propagation characteristics of Lamb wave which is with the multimode and dispersion properties.Describe the Lamb wave excitation process and study the dispersion characteristics.Then focus on the main methods of Lamb wave dispersion compensation(3)Firstly,the Lamb wave excitation and sensing process is studied theoretically while the Lamb wave sensor model is established.On the basis of this sensing model,the sensor signals with different dispersion relation are obtained,as well as the effects of different dispersion characteristics on the sensing signals.Secondly,the original sensing signal is subjected to dispersion compensation based on frequency-wavenumber curve.In the study of circular array,the region of damage may be reconstructed by using RAPID tomography,and the direction of damage can be determined by orthogonal cross-scan method.So as to reconstruct the damage image more accurately.(4)Design a Lamb wave structure damage monitoring system based on the frequency-wavenumber domain,which implemented on an aluminum plate with round piezoelectric arrays.Combining with the existing imaging technology and cross orthogonality scanning method to reconstruct.Realized the real-time monitoring and assessment of damage.The results show that the method of Lamb wave structure damage detection based on frequency-wavenumber domain processing can effectively realize the location and reconstruction of the damage,improve the signal-to-noise ratio,the resolution of imaging and have better application prospect.