Research On Crack Detection Based On Dielectric Resonator And Its Array

In the field of sensing and communication,sensors are often used to detect cracks caused by external effects on large metal structures that work in harsh environments such as outdoors and high temperatures.Due to the complex working environment of large metal structures,sensors used for crack detection are increasingly challenged by the environment.Compared with traditional sensors,the use of dielectric resonators as crack detection means can meet the requirements of low cost,high operability and flexibility in various environments.Based on the sensing mechanism of dielectric resonators,this paper focuses on the research and design of crack detection.The main work is as follows:1.Research on the sensing mechanism of the cylindrical dielectric resonator.Based on the characteristics of miniaturization and high sensitivity of dielectric resonators,a cylindrical dielectric resonator is designed in this paper.The structural parameters of the resonator are calculated through the theoretical formula of the cylindrical dielectric resonator and the perturbation theory is carried out simulation and verification.In this paper,the sensing mechanism of the dielectric resonator as a sensor to detect cracks is first studied and analyzed.The simulation extracts the electromagnetic field energy change data of the crack and the dielectric resonator during the crack expansion process.According to the perturbation theory formula,it can be known that the crack expansion causes the dielectric resonance.The resonant frequency of the converter is shifted.Secondly,the data obtained through simulation and actual measurement of the dielectric resonator to monitor the cracks show that the resonator has good communication capabilities while maintaining its sensitivity.Finally,by simulating the different situation of the relative position of the crack and the center of the resonator,the interference effect of the crack position on the resonance frequency is analyzed.The simulation sensitivity of the dielectric resonator for detecting cracks with varying depth is-33 MHz/mm,the maximum error is 85 MHz,the measured sensitivity is-37.2 MHz/mm,the maximum error is 108 MHz.The simulation sensitivity for detecting cracks with varying width is-25 MHz/mm,the maximum error is 90 MHz,and the measured sensitivity is-21 MHz/mm,the maximum error is 89 MHz.2.Research on the array of dielectric resonators to eliminate the influence of the relative position of the cracks on the sensitivity of the resonator.In a complex environment,cracks on the metal structure will appear at random positions,and the relative position to the center of the sensor is also random.The uneven energy distribution of the dielectric resonator causes different crack detection sensitivities at different positions,which results in the resonator being sensitive to the crack position.In order to achieve high-sensitivity and position-insensitive crack detection,multiple dielectric resonators are used in a staggered array.By adjusting the spacing of the resonator array,a more uniform spatial field distribution is generated,thereby reducing the influence of the uncertainty of the crack position on the consistency of detection.The simulation sensitivity of the proposed dielectric resonator array to detect crack depth changes is-37 MHz/mm,the maximum error is 12 MHz,the measured sensitivity is-73.8 MHz/mm,and the maximum error is 17 MHz.The simulation sensitivity of the array to detect crack width changes is-30 MHz/mm,the maximum error is 10 MHz,the measured sensitivity is-53.2 MHz/mm,and the maximum error is 20 MHz.