An example system for inspecting railcar axles includes a flash source, an infrared camera, and a trigger sensor. The flash source is configured to apply a thermal pulse toward a surface of a railcar axle of a railcar wheelset, while the railcar wheelset is on a track. The infrared camera is configured to capture infrared data indicative of a thermal response of the surface of the railcar axle to the thermal pulse. The trigger sensor is configured to trigger the flash source to apply the thermal pulse based on a position of the railcar wheelset on the track. The example system can also include a processor configured to determine whether the captured infrared data is indicative of a crack on the surface of the railcar axle, and a vision camera configured to capture an image of the surface of the railcar axle.