Research On Wavefield Reconstruction And Damage Imaging Of Composite Laminate Based On Compressed Sensing Algorithm

Carbon Fiber Reinforced Plastic(CFRP)plate is widely used in aerospace,high-speed railway,wind turbine and other large structures due to their excellent comprehensive performance.The health of these structures is also directly related to the integrity and safety of the system.Among the current nondestructive testing technologies,the traditional Lamb wave detection method based on distributed sparse transducer array usually realizes the damage location according to the transit time between arrays,but it is difficult to accurately evaluate the scale and orientation of the damage due to the limited spatial resolution.Compared with the distributed sparse array transducer,using the noncontact scanning laser Doppler vibration(SLDV)detection method can obtain the high spatial resolution guided wave field in the tested area of composite materials,and then get the wave field characteristic change caused by damage.The purpose of accurate damage evaluation can be achieved by using massive data.However,in the full wave field detection technology based on SLDV,the spatial sampling points need to be collected according to the Nyquist sampling law,and the sampling points need to be measured and averaged multiple times to reduce the signal-to-noise ratio,resulting in serious consumption of the acquisition process.In addition,a large amount of mining data brings great challenges to data storage.In recent years,the sampling theory based on compression sensing method can realize the sparse decomposition and reconstruction of wave field by nonlinear algorithm under the condition of far less than Nyquist sampling frequency.However,due to the complex anisotropic propagation characteristics of guided waves in composite materials,the application of compression sensing method in composite plates becomes a challenge.To solve this problem,we studied the propagation of Lamb wave in composite material.Considering the wavenumber characteristics in all directions,we constructed the wave number library of Lamb in different directions of propagation in the specified parameter composite plate.Simultaneous interpreting the full wave field with the compressed sensing algorithm,which is far below the number of Nyquist sampling points.In the stage of damage analysis,the scattering wave field separation technology without reference signal was proposed,and the root mean square energy method was introduced to evaluate the damage,and the localization,quantification and analysis technology of anisotropic composite damage detection based on compression sensing is improved.The research contents of this paper are as follows:(1)Firstly,this paper introduces the research background and application significance of this subject,analyzes the research status of Lamb wave nondestructive testing method based on noncontact Doppler laser vibrometer(SLDV)at home and abroad,and investigates the development trend of compression sensing in the field of guided wave.Based on the above literature research and reading,determine the research direction and specific content of this topic.(2)The concept of Lamb wave was introduced,and the dispersion characteristics of Lamb propagating in composite laminates were analyzed.The wave number library of Lamb in simultaneous interpreting of different propagation directions in a specified parameter composite plate was constructed.Then,the theory of compression sensing algorithm was deeply explored,and the propagation equation of lamb in composite material was constructed into a series of source superposition,and the signal was reconstructed based on L1 minimization algorithm.The cross power spectral density was established to quantitatively characterize the reconstruction quality,and the RMS energy method was introduced to locate,quantify and analyze the damage of the reconstructed wave field.In order to verify the feasibility of the proposed method,taking the simulation data of lossless composite plates as an example,the wave field reconstruction and excitation source imaging analysis were carried out by using the proposed method.The simulation results show that the coherence of wave field reconstruction at the main analysis frequency band reaches 0.99,the positioning accuracy error of excitation source is 0,and the size evaluation error is 0.5mm.(3)By Using the finite element simulation software COMSOL to build the composite plate model with damage,the proposed method was applied to reconstruct and analyze the wave field with the damage data of through-hole.In the stage of damage analysis,the method of scattering wave separation without reference signal was proposed,and the RMS method was introduced to analyze the scattering wave field.The simulation results show that the coherence of wave field reconstruction at the main analysis frequency band reaches 0.96,the absolute error of damage location is 1.4mm,and the absolute error of size evaluation is 1.6mm.Then,taking the simulation data of composite plate with single hole damage as an example,the effects of measurement points,reconstruction points and noise parameters in the algorithm on reconstruction quality and calculation time were discussed respectively,and the optimal parameter selection space is summarized to guide the experiment.(4)To verify the feasibility and superiority of the proposed method from an experimental perspective,constructing a PZT excitation-SLDV receiving experimental platform.The test piece is a CFRP board made of carbon fiber / epoxy resin laminated material,and a circular magnet with a diameter of 10 mm is pasted to simulate damage.A phase spectrum method was used to measure the phase velocity and wave number of the guided wave propagating in all directions of the composite material,and a wave number library in the direction of 0 °-360 ° was constructed for subsequent calculations.The experimental data results prove that the calculation is based on the sampling compression rate of 94.96%,which mainly analyzes the accuracy of the lossless wavefield reconstruction in the frequency band.The coherence can reach 0.92,and the damage wavefield reconstruction has the accuracy of 0.9.The positioning accuracy error is 5.7mm,and the absolute error of size evaluation is 2.1mm.This paper validates the proposed method of sparse reconstruction and damage imaging of the Lamb wavefield of the composite plate from the perspective of simulation and experiment,and the localization,quantification and analysis technology of damage detection of anisotropic composite materials based on compression sensing was improved.The related achievements can provide a theoretical and methodological basis for the practical application of SLDV in composite material damage detection.