Rail Inspection Using Noncontact Laser Ultrasonics

In this study, a noncontact laser ultrasonic system is proposed for rail defect detection. An Nd-Yag pulse laser is utilized for generating ultrasonic waves, while the corresponding ultrasonic responses are measured by a laser Doppler vibrometer. For detecting rail surface damages, the excitation laser beam shape is transformed into a line, whereas a point source laser beam is employed for inspecting defects within the rail head. The interactions of propagating ultrasonic waves with defects are examined using actual rail specimens. Notable amplitude attenuation was observed for surface cracks, and reflections were significantly pronounced from internal damages. The study discusses the opportunities and challenges associated with real-time rail inspection from high-speed trains, highlighting the necessity for advanced and efficient inspection techniques as rail damage risk escalates with train speed and frequency increases.