Fatigue crack monitoring using plastic optical fibre sensor

Abstract

Optical fibre sensors have shown their excellent potential for structural monitoring in a variety of engineering structures. This paper discussed the feasibility of real-time monitoring of fatigue crack using an extrinsic plastic optical fibre sensor. This intensity-based plastic optical fibre (POF) sensor was fabricated by connecting two cleaved optical fibres into a capillary tube and inserting some in-filling into the tube to improve the sensitivity of the sensor. The aim of this sensor is to detect crack initiation and subsequently monitor the propagation of crack under fatigue load, relying only on the plastic fibre sensor signal and a simple signal processing method. Performance of the fabricated POF sensor was evaluated by comparing with another technique, namely, acoustic emission (AE) method. The results show remarkable resemblance in terms of crack initiation and propagation identification exhibited by both of the sensors, highlighting the potential of the proposed method for crack initiation detection and subsequent monitoring of crack propagation. The simplicity of the technique renders it an attractive structure health monitoring tool for fatigue crack monitoring.