Research On Damage Detection Characteristics Of Metal Structure Based On Piezoelectric Wafer Active Sensor

Sheet metal structural parts can be seen everywhere in aerospace,military and civil infrastructure,and the detection of structural health and fatigue damage is particularly important.Acoustic emission technology,as an emerging method of metal structure health detection,can help people have a more intuitive understanding of the physical characteristics of metal structure damage.In view of the high price and large size of acoustic emission sensors for metal structure health detection,this paper proposes the use of piezoelectric wafer active sensors for metal fatigue crack detection.The main work of this thesis is as follows:(1)The piezoelectric wafer active sensor was used to capture the acoustic emission signal generated by the fatigue crack of the metal and compared with the commercially available R15 AE sensor.The experimental results were analyzed based on AE hit analysis,AE waveform analysis,and background noise analysis.The analysis results found that the piezoelectric wafer can successfully capture the acoustic emission generated by the fatigue cracks of the metal,and it is better than the R15 AE sensor in the high frequency area.The signal-to-noise ratio is higher,but the background noise is larger.The problem of large background noise of the piezoelectric wafer was dealt with in the experiment.(2)Research on the propagation characteristics of the Lamb wave in the metal sheet,numerical simulation verification on the Lamb wave damage recognition theory based on piezoelectric wafer active sensors,the simulation results show that the piezoelectric wafer is used for the positioning of the flat sound emitting source has high precision and stability.On the basis of understanding the coupling between the Piezoelectric wafer and the LAMB wave in the structure,the single mode Lamb wave time inversion imaging method is studied,and the accuracy of the positioning of piezoelectric wafer sound emission damage is analyzed.(3)Set up a piezoelectric wafer acoustic emission positioning experiment platform for thin metal plate specimens to simulate the acoustic emission source by breaking the lead,analyze the acoustic emission signal received by the piezoelectric wafer,and use the single-mode Lamb wave time-reversal imaging method proposed in the thesis to transmit Source for positioning,the positioning error of the four experiments is less than 4%.