Research On High Temperature Strain Sensor Based On Surface Acoustic Wave(SAW) Technology

Being more widely used in safety engineering,environmental monitoring,aerospace and other fields,the surface acoustic wave(SAW)sensor is miniaturized,lightweight,high sensitivity,good temperature stability,and its planar structure process is convenient for mass production.In this paper,the research on the surface acoustic wave(SAW)strain sensor is of momentously scientific and practical value for the health monitoring of metal structural parts under high temperature and complex environment rather than being with low sensitivity and poor system stability.The paper aims to meet the requirements of real-time high sensitivity(above 50Hz/??)strain monitoring of metal structures under high temperature environment(temperature drift,maximum ambient temperature up to 250 ?).Based on SAW principle,two kinds of 41 ° YX tannin are proposed,using Lithium piezoelectric single crystal as the substrate.Also,the working principle of SAW sensor is introduced.The SAW device types and their application are analyzed and compared,either.The main structural parameters of the resonator are determined by SAW theory,and the principle sample is successfully developed.Aiming at rising the sensing accuracy of surface acoustic wave strain sensor in high temperature strain test of metal structural parts,the strain transmission hysteresis mechanism of adhesive device is explored,the experimental test plan is established,and the temperature and strain test platform are built to test and analyse the prototype.The experimental results show that the structural design of the SAW resonator interdigital transducer(IDT)can improve the strain sensitivity without affecting the temperature stability of the device.The strain sensitivity can reach 214.29 Hz/??,and the degree of improvement is about 19 %.Aiming at the problem that the frequency-temperature coupling coefficient(TCF)based on lithium niobate substrate is large and can not maintain stable sensing performance under temperature drift environment,the paper further proposes an aluminum nitride(AlN)based substrate.The SAW resonator was designed with the simulation software of Comsol and so on.The high temperature strain sensor chip was fabricated by designing the MEMS process.The TCF was improved to-27.9ppm/?,being compared with-83 ppm/? of the lithium niobate SAW strain sensor,nearly 60%.Finally,the modification of AlN piezoelectric sensitive film was discussed,which provided a technical reserve for the development of the next generation strain sensor.The main work: expounding the background and significance of the research,conducting a large number of literature research,analyzing and determining the application environment conditions;monitoring the sensor requirements for metal structural parts with high heat resistance,high strain sensitivity and high temperature stability.The strain sensor structure based on SAW principle is proposed.The theoretical model of strain sensing sensitivity prediction is established in the application environment.The principle sample of the sensor is prepared,and the experimental test method is determined.The temperature and strain test platform is built to complete the temperature stability test.The strain sensing experiment shows that the SAW strain sensor chip developed in this paper can meet the needs of the application environment.