超声导波在弯管中传播特性的有限元分析

通过建立弯管的ANSYS／LS-DYNA3D模型，模拟了L（0，2）模态导波在管道中的传播形态；计算了弯管中I。（0，2）和T（0，1）两种模态群速度曲线，并与相同管径和壁厚的直管做对比；研究了L（0，2）模态对管道弯头内外侧缺陷的检测能力。结果表明：导波在通过弯头时会发生模态转换，且频率越高模态转换越明显；L（0，2）和T（0，1）两种模态在弯管和直管中的频散曲线低频段时差异小而高频段时差异显著；并且，L（0，2）模态对弯头外侧缺陷检测能力要高于弯头内侧。

Finite Element Analysis of Propagation Characteristics of Ultrasonic Guided Waves in Ben,ded Pipes

Using ANSYS/LS-DYNA, a 3D model of bended pipes wa：s built and propagation of L（0,2） mode guided waves in pipes was simulated. The group velocity curves of L（0,21 and T（0,1} mode in bended pipes were calculated and compared with straight pipes of having the same diameter and thickness. Also, the ability of L{0,2） mode to detect defects located inner or outer side at bends was studied. Results showed that there would be a mode conversion when guided waves passed a bend part. When frequency increased, the mode conversion was more obvious. It was found that the difference of dispersion curves between curved pipes and straight pipes was small at low frequency and big at high frequency. And, L{ 0,2） mode performed better when used to detect outer side defects at bends.