Wireless Strain Sensors for Dynamic Stress Analysis of Rail Steel Structural Integrity

Fatigue fractures were observed at the web-to-head and web-to-foot interface regions of rail steel thermite weld joint on curve tracks in a mass rapid transit tunnel. To investigate these failures, onsite wireless strain measurement was conducted to record the train-induced stress spectrum at a thermite weld joint and the results were presented in this paper. Dynamic finite element (FE) analysis was then conducted using the thermite weld and rail steel structural model under train-induced loading conditions and is validated by the strain gage sensor measurements. The train-induced stress at critical locations of thermite weld was investigated. Combining the strain measurements and FE analysis results, the service load stress spectrum using the variable amplitude strain analysis spectrum at the stress concentration site was obtained and fatigue life for a critical location of the thermite weld was predicted using the cumulative damage summation method. This research provides a fatigue mechanics-based approach for rail steel asset life prediction methodology.