Fatigue Behavior of Metal-Packaged Regenerated Fiber Bragg Grating Strain Sensors at High Temperatures: A Preliminary Study

Abstract

Regenerated Fiber Bragg grating (RFBG) sensors exhibit tremendous growth in recent years and could be widely used for measuring strains and for structural integrity assessment of components operated at high-temperature if critical issues (fatigue life, interface integrity, etc.) are addressed. For the determination of fatigue life of metal-packaged RFBG strain sensors at high temperatures, tensile fatigue tests are performed on the sensors. The preliminary results show that the sensors exhibit good linearity and repeatability, and rare sensitivity change under cyclic tension loading when exposed to constant high temperature up to 500 °C, without obvious variations in the spectral response. The rupture of the optical fibers is the major cause of fatigue failure of the sensors. The sensors subjected to lower test strain have greater fatigue life. A rapid decrease in Bragg wavelength is observed at the beginning of the fatigue tests followed by stabilization of the Bragg wavelength. These results indicate that the sensors are the promising candidates for health monitoring of structures subjected to cyclic loads at high temperatures.