钢花管中低频扭转模态的衰减特性

摘要

The effect of hole number and the diameter of holes of perforated pipe on the attenuation of torsional guided wave mode, T(0,1), at low frequency is investigated by finite element simulation and experiment. First, propagation characteristics of torsional guided waves at low frequency in free steel pipe are theoretically analyzed. Then, group velocities of T(0,1) mode at different frequencies are obtained by finite element simulation and experiment and compared with theoretical dispersion curve of this mode. Result show that finite element simulation is valid, and the excitability of T(0,1) mode by thickness shear mode transducers is effective. Based on this, the fittest excitation frequency for T(0,1) mode inspection of perforated pipe is confirmed to be 30 kHz. Finally, both finite element simulation and experimental results show that the signal amplitude of T ( 0 , 1 ) mode at 30 kHz decreases in different extents along with the increase of the hole number and the diameter of the hole. These results provide a foundation for nondestructive inspection of perforated pipes by using T(0,1) mode at low frequency.%结合有限元仿真与实验研究了钢花管的注浆孔数与孔直径对低频扭转模态T(0,1)衰减特性的影响。首先,理论分析了自由钢管中低频扭转模态的传播特性,然后将有限元仿真、实验得到的不同频率的T(0,1)模态群速度与理论频散曲线进行对比,验证了有限元仿真的正确性及厚度切变型传感器激励T(0,1)模态的有效性。在此基础上,确定了30 kHz为T(0,1)模态检测钢花管的最佳激励频率。仿真与实验研究结果表明：频率30 kHz的T(0,1)模态的信号幅值随注浆孔数的增多与孔直径的增大有不同程度的下降,为利用低频T(0,1)模态对钢花管进行无损检测奠定了基础。