高频纵向超声导波在埋于无限大介质中钢杆的传播特性

从理论上分析高频纵向超声导波在埋于无限大介质中钢杆传播的特性.根据在杆状波导中传播的超声波具有频散现象及多模态特征,选择特定频率下的单音频信号激励超声导波,使其衰减最小,能传播较长距离;能量速度最大,最先到达,从而可与其他速度较慢的模态相区别.说明此频率下的纵向模态可用来对埋于介质中的钢杆进行检测.同时建立试验系统,对直径22 mm、长度1 m的埋于水泥中的钢杆进行检测,并对结果进行时频分析,试验结果与理论分析相吻合.

PROPAGATION CHARACTERISTICS OF HIGH FREQUENCY LONGITUDINAL ULTRASONIC GUIDED WAVES IN STEEL ROD EMBEDDED IN INFINITE MEDIUM

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 inspec- tion 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.