Experimental Investigation on Guided Wave Detection Technology for Rail Bottom Vertical Vibration Mode

Existing railroad rail ultrasonic testing car equipped with special transducer such as wheel probe is blind to the defects in rail bottom;which is a great hidden danger for rail transport safety.Therefore,investigation on propagation characteristics of ultrasonic guided waves in rail bottom and guided wave inspection technique based on vertical vibration mode was carried out.At first,the dispersion curve and wave structure of guided wave propagating in 60# rail bottom in various vibration modes were numerically calculated by using semi-analytical finite element method.Secondly,the propagation characteristics of guided wave in vertical vibration mode for rail bottom in unrestrained state were experimentally analyzed by model hammer technology.Results show that within 0～100kHz frequency range,the propagation characteristics of dominant guided wave vertical vibration mode in rail bottom are very similar to that of A0 mode of Lamb waves in a 14mm thick plate.Furthermore,dominate influence factors concerned to guided wave propagation in vertical vibration mode in rail bottom,such as excitation frequency,excitation pulse oscillate cycles and propagation distance were investigated.A guided wave angle probe was self-designed and appropriate parameters were select,then,the artificial cracks in rail bottom were successfully detected by vertical vibration guided waves.Above results provide a basis of nondestructive testing technique for rail bottom based on guided waves in vertical vibration mode.