Step corrosion FBG-induced twin reflection spectrum for temperature and strain composite decoupling measurement with adjustment of range and sensitivity

Abstract

This study introduces a novel method for composite temperature-strain sensing, addressing the growing need for large-range, high-sensitivity measurement systems in aeroengine compressor blades. We designed a sensor featuring an adjustable measurement range and sensitivity, incorporating a step corrosion FBG (SCF) and a “Bi”-shaped parallel lever elastic substrate. To improve the accuracy of strain monitoring, we established a six-layer strain transfer model for the SCF, with a suspended grating region and both ends bonded. An algorithm of dynamic adaptive twin-peak locking and extreme learning machine (DATLA-ELM) for twin reflection spectrum demodulation and nonlinear decoupling was proposed, achieving precise peaks identification and dual-parameter separation. The creep resistance and high-temperature performance of different packaging methods, including AB adhesive, tin welding and laser welding, were evaluated. The results show that the laser welding sensor can withstand temperatures up to 625  °C, with a drift ratio of 0.71 % and a drift rate of 0.01 %·h⁻¹ approximately. Additionally, it offers a measurement range of ±5,000 με and a sensitivity of 11.26 pm/με. By adopting DATLA-ELM, the maximum decoupling deviations for temperature and strain are 3.11  °C and 19.45 με, respectively. These attributes position the developed sensor as an ideal solution for composite strain-temperature sensing in various aerospace applications, underscoring its effectiveness and reliability in challenging operational environments.