超声导波在弯管中的传播较在直管中人传播更为复杂，而在实际工程现场，弯管弯头部位的检测尤为重要。利用磁致伸缩超声导波激励出扭转模态T（0，1），研究了超声导波在弯管中典型部位的缺陷检测问题及不同检测频率对弯管缺陷识别的影响。试验结果表明：检测频率低会导致超声导波反射信号在拱背外侧缺陷和弯头焊缝处发生频散而难以分离；检测频率高，得到的弯头拱背内侧缺陷与拱背外侧缺陷的信号幅值都很小。因此选择合适的检测频率，才能更好地对弯头缺陷进行有效识别。T（0，1）模态导波经过弯头时，能量会在拱背外侧产生聚焦，在拱背内侧出现发散，拱背外侧缺陷比拱背内侧缺陷更容易检出；信号经过弯头后，能量衰减严重，衰减后的能量约为原来的一半。

The propagation of ultrasonic guided wave in elbow pipe is more complex than that in straight pipe. However, the detection of elbow pipe part is especially important in the actual engineering site. The torsion mode T(0,1) excited by magnetostrictive ultrasonic guided wave was used to study the problems of ultrasonic guided wave in the detection of defects in typical parts of the bend and the influence of different detection frequencies on the detection of defects in the bend. The results show that the low detection frequency makes it difficult to separate the ultrasonic guided wave reflection signal at the defects of the dorsal side of the arch and the elbow weld due to the frequency dispersion. When the detection frequency is high, the amplitude of the defects on the inside of the arch back and the outside of the arch back is small. Therefore, selecting appropriate detection frequency can effectively identify the elbow defects. When the mode T(0,1) wave passes through the elbow, the energy focuses on the outside of the arch dorsum and diverges on the inside of the arch dorsum. Therefore, it is relatively easy to detect the defects on the outside of the arch dorsum as compared with those on the inside, which are easy to be undetected. After the signal through the elbow, the energy attenuation is serious, about half of the original energy.