导波模态类型对锚固锚杆无损检测的影响

Influence of Guided Wave Mode Types on the Non-Destructive Testing of Grouting Rock Bolts

纵向模态、扭转模态和弯曲模态超声导波在锚固锚杆结构中衰减的差异性巨大,研究这3种模态超声导波的传播规律对无损检测中测试波的选择具有重要指导意义.应用全局矩阵法的理论计算方法和数值模拟方法分别对这3种模态导波的频散规律和传播规律进行研究,两种方法的研究结果吻合较好.研究结果表明,纵向模态在高频范围内存在衰减为20~44 dB/m的超声导波;扭转模态的所有导波衰减都大于180 dB/m;弯曲模态的导波衰减也大于50 dB/m.因此,纵向模态高频范围的超声导波由于衰减小、易激发等优点可以作为无损检测中的首选测试波.

Longitudinal mode,torsional mode and flexural mode ultrasonic guided waves have different attenuation properties in anchored rock bolt.Therefore,the study of the transmission law of the three modes of ultrasonic guided waves has important guiding significance for the selection of test waves in non-destructive testing(NDT).The global matrix method and numerical simulation were used to obtain the dispersion curves and time-domain waveforms corresponding to these three modes,respectively.The characteristics of these three modes obtained by theory calculation and numerical simulation are in good agreement with each other.The results indicate that the attenuation of longitudinal mode ultrasonic guided waves ranges from 20~44 dB/m with high frequency.Attenuations for all torsional mode ultrasonic guided waves are greater than 180 dB/m.Moreover,attenuations for flexural mode ultrasonic guided waves are greater than 50 dB/m.Thus,longitudinal ultrasonic guided waves with high frequency are the most applicable modes because of low attenuation and easy excitation.