Abstract: Propagation characteristics of longitudinal ultrasonic guided waves of steel rod embedded in infinite medium are studied in theory. Due to the characteristic of dispersion and multi-mode of rod , a longitudinal mode whose attenuation is smallest in all modes and its energy velocity which is the fastest at special frequency can be excited. This high frequency loss attenuation mode can propagate longer distance and be received firstly, which indicates that this mode can be used to the inspection of rod embedded in infinite medium. At the same time, the experiments about diameter 22 mm, 1 m length rod embedded in grout detected using ultrasonic guided wave are carried out, and time-frequency analysis is also performed for the results of experiments. Experiment results are consistent with those of theory.

Key words: High frequency, Infinite medium, Nondestructive testing, Rod, Ultrasonic guided waves