Insulated rail joint (IRJ) contact characterisation-an ultrasonic reflectometry approach for a cross-material interface

Vehicle–track interaction at insulated rail joints (IRJs) plays a significant role in the wear evolvement and damage of the IRJ components. It is, however, challenging to characterise the contact conditions within the region non-destructively and accurately using experimental tools, especially when the IRJ contact involves both wheel–rail and wheel–endpost contact pairs. This study presents an ultrasonic technique to monitor and characterise static IRJ contacts in a non-invasive manner. The proposed ultrasonic reflectometry technique can realise high-resolution visualisation of contact patch and contact pressure distribution for both wheel–rail contact and wheel–endpost contact, by striking a beam of focused ultrasonic signals at the contact interface. Different data post-processing strategies are applied for the two types of contacts and a deconvolution algorithm is applied to rectify the measurements near the rail–endpost boundary. The ultrasonic measurements are verified through finite element simulations and the results show good agreement with each other in terms of both contact area and contact pressure level. It is expected that the proposed ultrasonic approach can be a reliable tool to assist in revealing the contact behaviour of IRJs more profoundly.