The rapid development of high-speed and heavy-haul railways caused rapid rail defects and sudden failure. This requires more advanced rail inspection, i.e., real-time accurate identification and evaluation for rail defects. However, existing applications cannot meet future demand. In this paper, different types of rail defects are introduced. Afterwards, methods that have the potential to achieve rapid accurate detection and evaluation of rail defects are summarized, including ultrasonic testing, electromagnetic testing, visual testing, and some integrated methods in the field. Finally, advice on rail inspection is given, such as synchronously utilizing the ultrasonic testing, magnetic flux leakage, and visual testing for multi-part detection. Specifically, synchronously using the magnetic flux leakage and visual testing technologies can detect and evaluate surface and subsurface defects, and UT is used to detect internal defects in the rail. This will obtain full rail information, to prevent sudden failure, then ensure train ride safety.

The occurrence of near-surface defects in service steel rails is prevalent. Rapid detection and accurate quantitative evaluation of rail defects are of practical significance for railway operation safety and cost control. Previous studies indicate that high-speed and large lift-off distance detection have become the technical bottleneck for existing non-destructive testing (NDT) methods. To address these difficulties, a novel rectangular-reciprocating-plane sensing structure with its supporting system based on electromagnetic induction thermography technology is proposed. It can address the challenge of insufficient transient heat accumulation time through large range of excitation space under high-speed motion model. That is, it mitigates the influence of lift-off distance fluctuation on detection and evaluation accuracy, offering a new technical perspective in rail inspection beyond conventional electromagnetic NDT methods. Ulteriorly, in-situ experiments on calibration and in-service route are carried out to validate the detection effectiveness of the proposed perceptual structure under high-speed (40-80 km/h) and large lift-off (30 mm) conditions. In addition, the integrated intelligent rail inspection system provides an innovative way for near-surface defect of fast inspection on railways.