L(0,1)模态导波在小管径管道弯头处的散射特性

采用实验和有限元模拟的方法研究了L(0,1)模态导波在小管径管道弯头处的模态转换和反射、透射特性,分别使用不同频率的激励信号对含不同弯曲半径弯头的管道进行检测。研究结果表明:L(0,1)模态导波在管道弯头处发生模态转换,转换成F(1,1)模态,并且其偏振方向与弯头拱背—拱腹方向一致;随着检测频率和弯曲半径的增大,反射F(1,1)模态呈减小趋势,透射F(1,1)模态呈非单调变化趋势;反射L(0,1)模态导波呈减小趋势,透射L(0,1)模态导波呈增大趋势;当检测频率或弯曲半径增大到一定程度时,两参数的变化对反射F(1,1)模态、反射L(0,1)模态和透射L(0,1)模态的影响不大。实验结果与模拟结果吻合度高,验证了模拟结果的正确性。研究结论为检测小管径含弯头管道提供了理论指导。

Scattering for L(0,1) mode guided wave at the elbow in small diameter tube

The experimental and finite element simulation methods were used to investigate the mode conversion and reflection and transmission phenomenon at the elbow in small diameter tubes. Excitation signals of different frequency were used to inspect tubes involve elbows of different bending radius. The results show that mode conversion phenomenon occurs at the elbow and the L(0,1) guided wave converts to F(1,1) guided wave. The orientation of F(1,1) is identical to the extrados-intrados direction of the elbow. With in increase of the inspection frequency and bending radius, the reflected F(1,1) mode decreases monotonically while the transmitted F(1,1) mode changes non-monotonically, the reflected L(0,1) mode decreases while the transmitted L(0,1) mode increases. When the inspection frequency and bending radius increase to some extent, the change of inspection frequency or bending radius has little influence to the reflected F(1,1) mode, reflected L(0,1) mode and transmitted L(0,1) mode. The experimental results agree with the simulation results well which validates the truth of the simulation results. The conclusions will provide theoretical guide to the inspection of small diameter tubes involve elbows.