Research on the factors influencing strain transmission of high-temperature fiber Bragg grating sensors with welding packaging metallization

By constructing a mathematical model of a four layer fiber optic grating sensor, the influencing factors of strain transfer in welded encapsulated metalized high-temperature fiber optic grating sensors were studied and analyzed. The relationship between single physical quantity and dual parameters and axial strain transfer rate was studied, and the theoretical analysis was validated using finite element method. The results showed that the strain transfer rate was 91.1% at a temperature of 300 ℃, and the Poisson's ratio had a relatively small effect on strain transfer. The thickness was inversely proportional to the strain transfer rate. In contrast to the welding layer, the smaller the elastic modulus of the coating, the more conducive it was to strain transfer. When the length of the welding layer was 4mm, the strain transfer rate reached 99.5%. Theoretical and simulation results showed high consistency, with an error within 0.004. This verified the correctness of the strain transfer function model selection and theoretical calculation, and provided a theoretical reference for further optimizing the selection of sensor materials and welding design.