Monitoring of fatigue crack propagation by intensity-based plastic optical fiber sensor
Abstract »Optical fiber sensor has shown their excellent potential as one type of important sensor for damage detection and structural health monitoring. This paper proposed a novel extrinsic plastic optical fiber sensor for fatigue crack detection and its potential for tracking crack propagation was assessed. This intensity-based plastic optical fiber sensor was fabricated by connecting two cleaved optical fibers into a capillary tube and pushing some infilling into the tube to improve the sensitivity of the sensor. The sensor has a relatively simple sensing principle and the cost of the sensor is very low. Thus it can be produced by inexpensive components compared with other sensors such as Crack Opening Displacement (COD) gauges and Acoustic Emission (AE) sensors. The performance of the sensor was evaluated by comparison with a commercial COD gauge. The process of extraction of the crack propagation trend from the plastic optical fiber sensor was also proposed in this paper. The emphasis of this process is the algorithm of trend extraction for plastic optical fiber sensor signal. Experimental results showed good agreement with that of the COD gauge and highlighted the possibility of using the sensor for fatigue crack monitoring. Furthermore, the plastic optical fiber showed relative good durability and repeatability under fatigue loading compared with commercial COD gauge.