Longitudinal Rail Stress Measurement using Ultrasound

The disruption to trains caused by rail maintenance commonly happens in operation. The stress state drives this issue as it causes damage to track. The longitudinal stress is induced by change in the temperature during extreme weather, especially in the widely used Continue Welded Rails (CWR) since there is no space for rail expansion. Existing stress measurement solutions to deal with this problem are either time/cost-consuming or destructive. Therefore, this project is aiming to develop a new non-destructive stress measurement device based on ultrasound, for rails, which is urgently needed and beneficial to the transportation industry. Previous researchers have shown the possibility of stress monitoring by using ultrasound and compared to other theories, this might be the best choice at the moment. The work in the PhD consists of five stages of testing. A pilot lab test for validating the ultrasonic stress measurement principle in small specimens, while, determining the most suitable transducer frequency and arrangement. After that, rail material study paralleled with validation testing of a removable transducer with rail specimens was conducted. Once the removable transducer-based system was built, laboratory testing with rail sections was performed to justify the versatility of the measurement system by testing it on different rails. In the real working condition, there are many random variables that must be assessed before a new system is turned into a commercial version, thus, field testing was critical in this work. Based on the performance from the field testing, an iteration can be delivered for improving accuracy and durability of the system. By using this rail stress monitoring system, the rail stress condition can be accessed without cutting the rail and closing the line from service, therefore, significant savings in operating and manpower costs can be achieved in the rail industry.