Application of Plastic Optical Fiber Fatigue Sensor in Real-Time Monitoring of Fatigue Cracks in Steel Structures

Plastic optical fiber (POF) is a new type of sensing material. Compared with traditional quartz optical fiber, it has the advantages of good tenacity, low cost, easy processing, and high sensitivity. A new type of POF-Fatigue sensor (nPOF-Fs) is designed by using POF, which is based on the changes the luminous flux. The change in the relative displacement of the two ends of the fiber is obtained through the change in the luminous flux in the POF, which is later converted into an electrical signal by the photoelectric conversion device. By collecting and analyzing the signals, accurate measurement of the dynamic response of the workpiece is achieved. Combined with the signal processing algorithm that can detect and monitor the crack expansion of steel structures under cyclic loading based on the RMS envelope and Hilbert transform filters, the fatigue crack can be monitored in real-time. The results obtained by nPOF-Fs are fundamentally coincide with the results acquired by the COD sensor. In view of the higher cost of monitoring with the COD sensor, the use of a POF sensor combined with a signal processing algorithm in monitoring the occurrence and expansion of fatigue cracks has great potential in the field of structural monitoring.