Research On Improving Damage Detection Technology By Ultrasonic Guided Wave

In the field of health monitoring of flat structure,Lamb wave is widely used because of its wide spread,sensitive to defects and so on.Among them,Lamb wave imaging technology can not only accurately locate the damage location,but also assess the degree of damage.Lamb wave imaging technology is the research focus of Lamb wave application.Based on the limitations of Lamb wave in the application,this paper proposes a modified model and method,which aims to extend the application range of Lamb wave imaging technology and improve the image quality.In this paper,we firstly research the mechanism of Vibro-Acousitic Modulation(VAM)of pulse,and it provide theoretical guidance for VAM of the Lamb wave.Under this,this paper proposed a bistable model with VAM of the Lamb wave.In this model,the traditional linear vibration system becomes a bistable vibration system,which can effectively improve the amplitude of the plate in the nonresonant frequency region.As a result of VAM effect of the Lamb wave,the Lamb wave imaging can be realized without reference signal.Through the experimental comparison,we found that the model is more accurate in non-resonant frequency region by Lamb wave imaging.The proposed model effectively extends the operating bandwidth of the Lamb wave imaging method by VAM.The dispersion compensation method in ultrasonic guided wave imaging is also studied in this paper,and the dispersion compensation method based on time-frequency delay is proposed.If the material properties are unknown,the traditional dispersion compensation methods need to calculate the wave number curve by amplitude calculation and additional experiment.In this paper,the new linear mapping method is used to estimate the mapping parameters by using the narrowband signal time-frequency ridge estimation parameter.Compared with the traditional method,the method is simple and widely applicable.Simulation and experimental results verify the effectiveness of the proposed method,and show that the method can effectively improve the resolution of Lamb wave imagingThrough the above research,the image quality of the Lamb wave in the vibration system and the dispersion state is effectively improved,and the applications of the Lamb wave in the non-baseline monitoring,long-distance monitoring and multi-fault detection are extended.