Research Of Integrated Temperature-Strain Thin Film Sensor

In the aerospace field,high-speed aircrafts are subject to enormous gas friction at the head,resulting in fast and drastic changes in strain and temperature.Aircrafts prolonged exposure to such extreme environments can lead to severe safety issues such as erosion and cracking,making it difficult for the aircraft to operate normally and even causing serious accidents.Therefore,real-time health monitoring of temperature and strain is crucial and necessary for high-speed aircrafts.For testing in such harsh environments,sensors must first be able to withstand high temperatures.Secondly,due to the rapid changes in temperature and strain,sensors require a short response time.Lastly,sensors must have good integration with the surface of the aircraft,and temperature and strain sensors must have a high degree of integration,minimizing the sensitive area of the sensor to unify the temperature and strain testing points.By using thin film strain gauges and thin film thermocouples,real-time measurements of strain and temperature at a certain position of the aircraft can be obtained,achieving health monitoring.Strain and temperature measurement in extreme environment and sensor integration have always been research challenges.To address this problem,this thesis conducted research on the integrated temperature-strain thin film sensor.Firstly,prepare PtW8 and PtRh10 thin films on Al₂O₃ ceramic substrates respectively,and investigate the influence of different sputtering pressures,annealing temperatures,and film thicknesses on the microstructure and electrical properties of the thin film samples.The optimal process conditions for the two types of films were obtained.The results showed that the optimal preparation conditions for the PtW8 film were:sputtering pressure of 0.77Pa,argon flow rate of 20sccm,sputtering power of70W,thickness of 2mm,and annealing at 1000℃for 2h.The optimal preparation conditions for the PtRh film were:sputtering pressure of 0.77Pa,argon flow rate of 20sccm,sputtering power of 80W,thickness of 2mm,and annealing at 1000℃for 2h.Under these conditions,the thin film resistivity was the lowest,and the thin film quality was the best under microstructure characterization.Subsequently,sensor patterns were designed and implemented.Based on the optimal process,the resistance temperature coefficient and strain sensitivity coefficient of PtW strain sensors with different annealing conditions and thicknesses were calibrated and compared.The best performance was achieved with a thickness of 1mm and annealing at 1000℃for 2h.Using this process,a PtW-PtRh integrated temperature-strain thin film sensor was fabricated,and cyclic calibrations were performed under 0-800℃and 0-600meconditions to study its resistance temperature coefficient,strain sensitivity coefficient,and Seebeck coefficient.The sensor exhibited good linearity in resistance and thermoelectric potential output within this temperature and strain range,and no failure occurred.The strain sensitivity coefficient of the strain sensor decreased linearly with increasing temperature,from 3.82 at 0℃to 3.68 at 800℃,and the resistance temperature coefficient was 823.78ppm/℃.The maximum strain test error under different temperature is 1.883%.The average Seebeck coefficient of the thermocouple was 5.66mV/℃,and the maximum temperature test error was 0.913%.A mathematical calculation method was used to study the temperature-strain decoupling of the dual-parameter sensor,and validation and error analysis were performed.The calculated value had an error of 4.92%compared to the linear fitting of the actual test value,demonstrating the feasibility and accuracy of the decoupling scheme and providing a viable solution for temperature.