Train-based Rapid Ultrasonic Scanning of Track (TRUST)

Rail failures due to transverse surface and near surface cracks in the railhead, web or foot are significant problems for the Australian and international rail industry. Because of the danger to trains posed by cracking, currently frequent inspections of the tracks must be made, which disrupts normal traffic on the rail network. We will develop an ultrasonic system for detecting cracks on railway tracks. While ultrasonic systems already exist for this purpose, our proposed system differs in some key respects that give it unique advantages.

Firstly, we will use electromagnetic acoustic transducers (EMATs) instead of conventional ultrasonic transducers. Because EMATs generate and detect ultrasound electromagnetically on the surface of the metal rails, they do not need to be directly in contact with them, instead being capable of operating a few millimetres above the surface of the rail. Therefore, an EMAT system is suitable for deployment on fast-moving trains, including some passenger and freight trains, instead of relying on specially adapted low-speed inspection cars as current systems do.

Secondly, we will combine surface wave inspection with angled-incidence shear-vertical bulk wave inspection. The surface wave inspection will send ultrasonic waves along the top of the rail to look at cracks in the surface of the rail caused by contact with the train wheels. At the same time an angled ultrasonic beam will be bounced off the bottom (foot) of the rail to look for the rarer but more serious cracking that can occur at the base of the rail to repeated load cycling. Both these techniques use a pitch-catch EMAT pair, and there is some potential scope for running both inspections through the same pair of probes with modulation to the drive frequency, which will be investigated during the course of the project.

As part of the TRUST project, we intend to demonstrate the use of this system for high-speed inspection by making and deploying a suitable "probe head" that can ride on standard rail track at a high speed and acquiring the use of a small stretch of track or a rotating "high-speed simulator" rail wheel in order to perform the high-speed trials. The success of this project will allow us to go on to the next step of developing a more comprehensive version of the system that can be deployed for testing on commercial trains and tracks.