Experimental Testing Procedures to Investigate and Improve Insulated Rail Joint Design and Life Cycle

An insulated block joint (IBJ) is a mechanical joint which joins two abutting railway rails whilst keeping them electrically separate from each other. They are an integral component of block signalling systems as they allow for train detection within the network, however, they are a weak point in the system where failures can occur. The aims of this research work were to develop test regimes to enable life cycle analysis of IBJs and use these tests to assess the performance of different materials and designs. This has been achieved by the use of specimen, component and full assembly level testing. Specimen and component level shear testing has been carried out which has allowed for the assessment of different glues and insulating materials that are used in an IBJ and also has tested differing design principles. These experiments have been monitored using ultrasound techniques to investigate how failures within the insulating materials occur. It has been found that by using a full fit design with a glass fibre lining material an improvement in the shear strength of the IBJ can be obtained in comparison to a standard UK design. A full scale testing regime was developed in order to cyclically load assembled IBJs and compare a new joint design with the standard design. The new test method enabled testing of the IBJs to failure and gave a good comparison between two joints. Ultrasonic monitoring techniques have been implemented based on knowledge gained in component level testing which has allowed for the assessment of de-bonding within the IBJs as the test is carried out. Further specimen and full scale testing was carried out and a novel test regime was used to experimentally model lipping, the plastic flow of steel over the end of an IBJ causing electrical failure. This test regime allowed for the testing of different materials in both the endpost and the rail. By using a hardened rail steel or a hardened laser clad layer on the running surface of the rail it has been found that lipping performance can be improved greatly. The work has led to the development of a new design of IBJ that incorporates material and design changes and aims to increase the life cycle of the IBJ by increasing static and dynamic stiffness and improving the rail material with respect to lipping performance. Further work on in service testing of laser cladding technology could be performed to further the work that has been achieved using twin disc testing.