Use of laser ultrasonics for rail flaw detection: an insight into preliminary experiments

There is an ever increasing demand for higher tonnages to be transported in heavy haul trains. This means that ensuring safety and reliability of rail tracks becomes an even more critical priority. Early detection of rail flaws ensures transportation safety and averts unplanned downtime. Several conventional non-destructive techniques have been proposed for rail flaw detection including eddy-current, infrared, vibration and laser induced ultrasonic guided wave based detection techniques. Laser induced ultrasonic guided wave based detection stands out as a more suitable method for being adopted in a moving vehicle rail flaw detection system. This paper presents the design process of preliminary tests carried out on rail samples to understand the laser induced ultrasonic guided wave propagation. Firstly, standard ultrasound non-destructive testing equipment is used to verify the ultrasonic guided wave propagation in a rail section. Secondly, ultrasonic guided wave generation using a pulsed laser source is used to generate ultrasonic guided waves in a rail section. This is followed by sensing of the guided waves using air coupled ultrasonic sensors. Rail samples with known interior flaws are used to verify the reflection properties of ultrasound waves as the next step. The paper presents these preliminary experimental results.