Crack Detection In The Curved Plate Based On Lamb Wave With Piezoelectric Film

The health monitoring of wind turbine blade,aircraft wing and other curved structures is the core of quality control and safe operation.Lamb wave has the advantage of a long propagation distance and high sensitivity to subtle defects,so it is suitable for large-area detection.Lamb wave detection technology is considered to have the most promising application prospect in structural health monitoring.,the initiation and expansion of cracks and other defects will bring significant security risks to the operation of the structure,will cause a huge amount of repair and replacement costs,well aware of the impact on the life of the structure,resulting in structural failure.The risk of stress concentration,fatigue and crack growth in the structure is detected by active or passive means,and the damage is evaluated.The traditional piezoelectric sensor has high hardness and brittle texture,so it is not suitable for detecting curved surface structure.Papers in the crack surface plate of Lamb wave propagation mechanism,developing a good flexibility,suitable for integration in the surface structure of 0-3 type piezoelectric thin film materials,and applied to the surface structure of Lamb wave detection,which provide basic theory for surface structure health monitoring and new sensor technology,has important academic significance and engineering application value.The main research contents of this paper include the following four aspects:(1)According to the dispersion equation of curved plate,the dispersion characteristics of Lamb wave are analyzed to obtain the dispersion curves of different modes and the displacement distribution.Simulation analysis is carried out on curved plates with different curvature,and comparison of theoretical dispersion curves between flat plates and curved plates is carried out to provide theoretical basis for simulation and experimental research.(2)The influence of different crack lengths,widths and depths on Lamb wave propagation characteristics in a curved plate was simulated and analyzed.The transmission and reflection wave displacement response signals were extracted,and the mapping relationship between crack size and Lamb wave propagation characteristics was established.The experiment of Lamb wave scattering signal detection in a curved plate with crack was carried out to verify the influence of crack length on the propagation characteristics of Lamb wave and provide theoretical basis for crack detection.(3)PZT/ epoxy resin piezoelectric film raw materials were selected,piezoelectric film materials were prepared by solid phase method,and the influence of PZT/ epoxy resin mass ratio,polarization temperature,polarization electric field,polarization time and other factors on its piezoelectric performance parameters were studied,so as to provide a flexible 0-3 piezoelectric composite material for monitoring the health of curved surface structure.(4)Using the developed piezoelectric film material to make Lamb wave detection sensor,the frequency response characteristics of the piezoelectric film sensor at different frequencies were tested and compared with the response characteristics of the traditional piezoelectric sensor.The results showed that the piezoelectric film sensor had good sensor response characteristics to Lamb wave.It is applied to the detection of Lamb wave damage scattering signal in the wing-shaped plate,and the damage location is conducted by the elliptic localization method.The experimental results are basically consistent with the actual damage location.