Propagation Characteristic of High Frequency Longitudinal Guided Waves in Steel Rod

The attenuation dispersion curve and group velocitydispersion curve of ultrasonic guided waves in steel rod are calculatedwith consideration of the attenuation. Propagation characteristics of highfrequency longitudinal modes between 1MHz~3MHz in steel rod arestudied. In theory, there is one attenuation minimum in every high orderlongitudinal mode whose attenuation is the smallest in all modes at thespecial high frequency. The high order mode at this special frequency canpropagate a longer distance than other modes at the same frequency. Thisindicates that high frequency low attenuation longitudinal mode at thisspecial high frequency can be used for the inspection of steel rod. Theexperiments on steel rod of 22mm in diameter, 2m in length arecarried out usingultrasonic guided wave. Guided wave signals are excited andreceived by the same probe at the same end of the rod. The group velocityand amplitude curves of first endreflection against frequency are obtained. The experimental curves areconsistent with those dispersion curves of theory. This indicates that thedispersion curve of steel rod with consideration of attenuationcharacteristics can be a guidance to experiment.