Laser based inspection and monitoring of rails: A finite element analysis

In order to cope with the ever increasing requirement of heavy loads to be transported by rail, it is a must to inspect and monitor the health of the rail tracks on a regular basis. Condition monitoring and health inspection of rails not only complies with the safety regulations, but it also ensures the minimising of destructive damage caused due to catastrophic accidents. Laser ultrasonics stands out as a distinctive approach for its simplicity, reliability and rapid results compared with other conventional non-destructive methods available for flaw detection in rails. Not only is it used for detecting surface fatigue cracks, but also for the internal subsurface cracks. In the context of monitoring the health of the rail, which entails detecting cracks at the early stage, the development of a numerical method such as finite element analysis is required. This paper presents finite element simulations of ultrasonic wave propagation in the rail foot which provides guidance regarding appropriate positioning on a rail vehicle of the laser source and sensor which can detect the presence of cracks in the rail foot. A high frequency excitation signal of short duration was used as a source of ultrasonic wave generation which then travelled through the length of the rail. Reflections from the cracks captured by the ultrasonic sensor indicate the presence of cracks in the rail. The outcomes obtained through the simulations facilitate an efficient way for development of condition monitoring of the rail tracks using the ultrasonic guided wave based technique, providing a strong platform for comparison with the outcomes of future experimental tests. Moreover, a method to develop cracks in rail samples which can be used for performance verification of a flaw detection system during development is also presented.