Damage Analysis of Switch Rail Welding by Examining Hardness and Microstructural Features: A Case Study of Addis Ababa Light Rail Transit

Abstract

The failure of railway tracks is an unavoidable phenomenon that affects the operation intensively. Previously different failure assessments and investigation research have been carried out; however, failure investigation techniques need to be updated frequently and assessed because the problem still exists. “Failure mode, effects, and criticality analysis” (FMECA) were implemented to identify the most critical failure mode with higher risk. The welded rail specimens’ quality, hardness, and microstructural features were evaluated at different cooling rates experimentally. To identify and assess the microstructure feature and hardness of rail welding through different cooling mediums three major NDT tests have been employed. Generally, all the nondestructive test results demonstrate that there is a noticeable defect on the welded rail cooled at 6 °C/s. Comparatively fewer defects were observed on the welded rail cooled at 3 °C/s, while acceptable defects were manifested on the one cooled at 2 °C/s. from “Failure mode, effects, and criticality analysis” (FMECA) results “gauge corner spalling” failure mode was with the highest risk priority number so its improvement has a great influence on the maintenance efficiency. As a conclusion, cooling of rail welding’s at 2 °C/s cooling rate will give the material good microstructural feature and better weld quality relatively. Finally, the researcher suggests that the one working in the field can control the cooling rate of the weld for welding quality improvement and maintenance efficiency increment.