Lamb Wave Structure Response Signal Compression Transformation Analysis Method And Its Damage Monitoring Application

Structural health monitoring technology can replace manual realization of online attention to structural conditions,and is a very important cutting-edge technology for intelligent manufacturing and intelligent structures.Guided wave based slab structure health monitoring technology is considered to be the most promising method for structural health monitoring.However,due to the influence of time-varying conditions,the structure monitoring technology based on guided wave damage scattering still has the problem of poor anti-interference ability.The slab structure is inevitably affected by vibrations from the surrounding environment under working conditions.At the same time,the structural health monitoring system is also affected by the surrounding electromagnetic field interference.These effects will prevent the structural health monitoring system from extracting the ideal information from the slab structure.In this paper,the propagation characteristics of Lamb wave in slab structure are studied.Through in-depth analysis of the synchrosqueezed wavelet transform signal analysis technology,the analysis and extraction of Lamb wave signal characteristic parameters using synchrosqueezed wavelet transform and the implementation scheme of structural health monitoring are researched.This scheme takes advantage of the Lamb wave's sensitivity to small damage and the high-resolution feature of synchrosqueezed wavelet transform,which has strong anti-interference ability.This article includes the following main contents:(1)The related information of structural health monitoring technology and the application of piezoelectric wafer active sensor in structural health monitoring technology are introduced.(2)The limitations of the signal analysis method for damage scattering are analyzed.The formula of synchrosqueezed wavelet transform is derived from wavelet transform.The results have been verified by experiments with higher resolution,and the computer implementation method of synchrosqueezed wavelet transform is studied.(3)The influence mechanism of the damage in the slab structure on the propagation of Lamb waves was studied,and a feature extraction scheme was proposed.This scheme uses multiple excitation signals with different center frequencies to excite Lamb waves in the slab structure,uses synchronous compression wavelet transform technology to extract the main components from the response signal,and obtains the feature vector set according to the number of main components and the energy propagation speed.The feature vector set can be used to draw the curves of the energy propagation speed of main components as functions of frequency for damage judgment.(4)A structural health monitoring scheme using active piezoelectric sensors and synchrosqueezed wavelet transform technology is designed,including hardware design and software design.The validity of the scheme was verified by building an experimental platform.The experimental results show that the Lamb wave structure health monitoring technology based on synchronous compression wavelet transform studied in this paper is feasible,with sensitivity to small damages and strong anti-interference ability.