Research On Structural Damage Location Based On Signal Reconstruction

With the development of science and technology,the application of wind turbines has become more and more extensive.However,according to the principle of wind power generation,wind turbines are often installed in wild mountainous areas with harsh conditions.This causes the wind turbine to be easily hit by a hard object during operation,or even eroded by wind and sand.This also creates a problem.If the health of the structure is not assessed and repaired in time,the structural material can only be continuously replaced,which is a considerable cost.Therefore,cost saving starts with monitoring and evaluating the health of the structure.So how should the health of the structure be monitored? In this paper,taking the most basic thin aluminum plate as the structural monitoring object,using the guided wave structure health monitoring technology based on piezoelectric crystal active sensors,the traditional structural health monitoring of aluminum plates will be optimized in time.The following are the work and innovations I have done while researching this topic:First of all,to understand the propagation characteristics of Lamb wave,to understand its propagation characteristics,it is necessary to understand its dispersion equation.According to the literature,Lamb waves have symmetric and asymmetric types,so I learned that there are two dispersion equations.Use the mathematical software MATLAB to solve the Lamb wave dispersion equation and draw its dispersion curve.After drawing the dispersion curve,use the frequency-thickness product(that is,the product of the multiplication of frequency and thickness,hereinafter referred to as "frequency-thickness product")as an independent variable,and select a more appropriate frequency-thickness product segment,that is,select a more appropriate frequency-thickness product segment.excitation signal frequency.Second,understand the mathematical principle of dispersion generation,that is,to understand the generation of dispersion from the perspective of signal processing,and use MATLAB to simulate the laws of signal propagation under high-order dispersion,secondary dispersion,linear dispersion and no dispersion conditions,according to the simulation results,understand the variation law of the amplitude and phase of the signal with the increase of the spatial distance under the conditions of high-order dispersion,second-order dispersion,linear dispersion and no dispersion.Third,consult the literature to understand the traditional wave packet decomposition method.Because even under the condition of low-frequency thick product,the response signal may still have multiple modes,and the signal wave packets of different modes have different degrees of dispersion effect.Therefore,the specific situation is analyzed on a case-by-case basis.The traditional wave packet decomposition method is improved so that it can decompose the multimodal response signal with frequency dispersion.The general process is as follows:construct the reference signal and the local response signal,and decompose the response signal by means of difference.And at the original time when the wave packet was decomposed,a Gaussian pulse with a narrower pulse width than the original excitation signal was constructed for reconstruction,and a new response signal without dispersion was obtained.Fourth,after improving the traditional wave packet decomposition method,analyze its limitations.On the basis of the traditional wave packet decomposition technology,the dispersion principle is added,that is,the dispersion effect of the wave packet is considered.At the same time,the excitation signal is optimized to excite only one mode as the dominant response signal,and the signal wave packet of this mode does not have a very serious wave packet.After that,the correlation function of the signal is obtained to obtain the position of each wave packet,the unit excitation signal is used,and the dispersion equation is substituted to obtain the dispersion wave packet as a reference signal for decomposition.Same as above,construct a Gaussian pulse with a narrower pulse width than the original excitation signal at the original time when the wave packet is decomposed,and obtain a brand-new response signal without dispersion.Finally,in the laboratory measurement stage,the thin aluminum plate is used as the structural object,and the piezoelectric transducer is arranged on the aluminum plate.Control the excitation conditions to excite a single mode of response signal.The response signal is processed using the above two methods.After processing,use the ellipse definition method to compare the advantages and disadvantages of the above two signal processing schemes.