Rail Base Defect Detection via Line Scan Thermography

Abstract

High-speed, in-motion detection of defects in active railways has become a primary focus in nondestructive testing (NDT) research and development efforts in the rail industry today. This investigation aims to provide further insight regarding the dynamic application of infrared thermography (IRT), namely line-scanning thermography (LST), for the detection of rail-base defects. A 3D finite element analysis (FEA) model was developed to first determine feasible parameters for the experimental setup, then subsequently employed for comparison with experimental results. To perform the experiments, mild steel samples were heated first by passing beneath an IR line heater (2000 W) then immediately observed with an IR camera to capture the thermal response. Results showed that for a thin steel specimen having stepped thickness (3.175 mm, 6.350 mm), a thermal contrast of 4.1ºC could be detected when inspections were performed at ~48.0 mm/s, revealing an agreement of roughly 95% with experimental results. In the case of thick steel samples containing bottom-drilled holes (BDHs), both experimental and analytical results showed that thermal contrasts of ~1ºC could be detected in regions above BDHs. Finally, performing LST on a rail-base sample containing BDHs yielded a contrast of 4.2ºC when moving at 40 mm/s.