Research On Piezoelectric Impedance Technology Of U-tube Based On Dynamic Signal

With the rapid development of piezoelectric smart materials,there were more and more researches on Piezoelectric Impedance Technology.In the initial use of piezoelectric impedance technology for structural health testing,most scholars at home and abroad measure the impedance of coupling system in static state,there were few researches on the structure reactance in dynamic state.But,in real life,most mechanical structures work in a dynamic environment.Therefore,it was very important to study the impedance of structure in dynamic environment.In this paper,the dynamic sinusoidal frequency signal loaded pipe fitting were studied.A sinusoidal signal with a certain frequency was applied to simulate the excited vibration of the pipe under normal working condition.The changes of the admittance and impedance of the pipe were studied and Combined with BP neural network technology,the neural network recognition system of dynamic frequency signal based on impedance data of pipe fittings was built.The main contents of this paper are as follows(1)The research status of piezoelectric impedance technology was introduced.The basic principle of piezoelectric effect of PZT was obtained,and the piezoelectric equation of PZT was analyzed.The SMD system model driven by PZT was established.(2)Two experimental platforms for acoustic experiment and impedance mode experiment were set up.The acoustic signal of pipe fitting was collected by acoustic experiment.By designing corresponding program in LABVIEW software,the sound signal of pipe was converted to the sound pressure spectrum of pipe fitting,and the modal frequency of pipe fitting was obtained.The static impedance spectrum of pipe fitting was obtained by impedance modal experiment,and then,the modal frequency table and the resonance frequency range of pipe fitting were obtained(3)The ANSYS simulation platform of pipe fitting was built,and the simulation analysis of pipe fitting was carried out.The error analysis of the simulation modal frequency and the frequency obtained from the impedance modal experiment of the pipe fitting was carried out.The correctness of the impedance modal experiment was verified.Based on the static analysis and piezoelectric analysis of piezoelectric sheet,the paste mode of PZT and pipe fitting and the model parameters of PZT were determined.(4)The impedance experiment platform of dynamic frequency signal applied by pipe fitting was built.The impedance experiments were carried out in the resonance region,the low-frequency non resonance region and the high-frequency non resonance region.Therefore,the impedance spectrum of the pipe fitting loaded with different frequency signals was obtained.The experimental results were processed by the methods of RMS deviation of admittance and covariance of admittance,and the variation law of impedance and admittance of the pipe fitting loaded with dynamic frequency signal was summarized.The basic principle of piezoelectric impedance technology for structural health detection under normal working condition was obtained.(5)A neural network frequency recognition system based on impedance data was established,the BP neural network system was used to identify the frequency signals of pipe fitting.It was proved that piezoelectric impedance technology combined with neural network technology can identify the unknown frequency signals of mechanical components.Figure[40]Table[7]Reference[80]...