Rail defect inspection based on coupled structural–acoustic analysis

The inspection of rail defects is of importance in high-speed railway operation and maintenance. As a highly efficient method for both nondestructive testing and structural health monitoring of the rail, ultrasonic guided waves (UGWs) inspection provide increased sensitivity to smaller defects. These advantages can be fully exploited only if the complexities of UGWs propagation between the medium of air and rail are unveiled and managed for the given inspection method. The development and validation of modeling procedure for the rail based on coupled structural–acoustic model is presented in this paper. Acoustic–structure interaction between air and rail is simulated based on COMSOL Multiphysics software. The transient response and natural characteristics of UGWs in the rail was computed and predicted. Moreover, the displacement distribution of UGWs in the defective rail and nondefective rail are analyzed both in time and frequency domain. A feasible method for detecting small defects in the rail is proposed in the paper. The results indicated that a defect of 8 mm in rail head can be inspected effectively using UGWs with frequencies of 40 kHz and above. And for small defects in rail web, the X-crystallographic direction ultrasonic transducer should be chosen for inspection.