| Nowadays, most of electromechanical test systems used for dam seepagepressure monitoring, which generally exist disadvantages of weak anti-interferenceability, poor long-term stability and larger relative error, drift and dynamic deviation,are difficulty to meet actual needs. Most optical fiber Bragg grating (FBG) areembedded in high polymer to compose pressure sensors. However, the fataldisadvantages of high polymer such as poor corrosion resistance, easy to aging,severely restrict durability of sensors. Consequently, it is very necessary to designand research FBG encapsulation structure with long life, small measure range andhigh accuracy.Based on the advantages and disadvantages of existing FBG sensorencapsulation structures and the characteristics of dam seepage pressure monitoring,two kinds of FBG pressure sensor encapsulate structures are designed, that aredouble bellows and flat diaphragm structures made of stainless steel, with differentmeasure ranges and accuracies, that can satisfy the engineering application. Workbasically has the following parts:1. The flat diaphragm encapsulation structure of FBG pressure sensor is designed.Based on the mechanics model of flat diaphragm, the structure parameters of flatdiaphragm FBG pressure sensor are defined.2. The double bellows encapsulation structure of FBG pressure sensor is designed.Based on the mechanics model of double bellows, the structure stiffness parametersare optimized by finite element analysis software.3. The processing technology of FBG pressure sensors is refined and perfected.FBGs are encapsulated to make up the FBG pressure sensors of flat diaphragmstructure and double bellows structure.The FBG pressure sensing experiment system based on spectral analysis isestablished. The experiment researches for flat diaphragm FBG sensor, whose range is0.5MPa and double bellows FBG sensor, whose range is10KPa, are carried out.And the sensitivities, resolutions, accuracies and other indexes of sensors areobtained. |
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