| Large-scale special facilities and equipment are the key to ensuring modern national defense construction and ensuring national production.Its core components such as aeroengine turbine blades and nuclear power plant boiler steam pipes have long-term work under extreme conditions of high temperature and high pressure,in order to ensure their normal operation,it is essential to carry out long-term structural health monitoring.Compared with the existing monitoring methods,the fiber Fabry-Perot sensor has the advantages of high measurement sensitivity,small installation size,no electromagnetic interference,little affected by temperature,long-term stability,etc.,which has application prospects for structural health monitoring in extreme working conditions.However,the existing methods mostly use a complex composite cavity Fabry-Perot sensor structure,resulting in poor mechanical strength.If the actual monitoring environment can be combined and the spontaneous emission characteristics of the black body under high temperature can be reasonably used,not only the light source support can be provided for the measurement system,but also realize the temperature compensation according to the temperature characteristics of the blackbody radiation.Therefore,this paper proposes a high-temperature strain measurement scheme for fiber Fabry-Perot sensors based on blackbody sources.In other words,the blackbody spontaneous radiation at high temperature is used as the light source of the measurement system of fiber Fabry-Perot sensor,and the single cavity fiber Fabry-Perot sensor of transmission type is used for high-temperature strain measurement,and the corresponding relationship between blackbody radiation and temperature is used to realize temperature compensation.Theoretical analysis and experimental research have been carried from the aspects of demodulation method and temperature compensation principle of fiber FabryPerot sensor based on blackbody radiation light source,optimization design of structure of blackbody radiation light source,intensity coupling efficiency of light source and fiber,etc.,and the following research work has been carried out:(1)Research on strain demodulation and temperature compensation principle of fiber Fabry-Perot based on blackbody radiation source.The characteristics of output signals of fiber Fabry-Perot sensor based on blackbody radiation source are analyzed,the signal demodulation method based on correlation calculation is studied,and the influence of light source parameters and sensor parameters on signal demodulation accuracy is analyzed.A high temperature strain measurement model is established.According to the corresponding relationship between the central wavelength and temperature of the black body radiation source,the temperature compensation mechanism s analyzed.(2)Study on the structure of blackbody radiation light source and its coupling efficiency with optical fiber.In order to improve the fiber-injection intensity of the blackbody light source,the effects of black body cavity structure,high emissivity coating material and coupling structure on the coupling light intensity are analyzed.The coupling efficiency of the tapered fiber end face,the spherical fiber end face and the black body light source is studied in detail,and the corresponding verification experiments are carried out.The results show that the high coupling efficiency of the tapered fiber end face and the spherical fiber end face is increased by about 50% and 80%,respectively,compared to the flat fiber end face coupling mode.(3)Experimental research.The temperature and strain test system of fiber FabryPerot sensor based on blackbody light source was built.The feasibility of the theoretical model of high temperature strain measurement is verified by the temperature and strain sensitivity test of the fiber Fabry-Perot sensor,the temperature compensation calibration experiment based on the black body radiation source and the high temperature strain measurement experiment within 300 ?. |
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