中文摘要：

理论分析得到了带粘弹性包覆层充液管道中纵向模态的频散曲线。为了验证理论分析结果，利用纵向模态对7．12m长的带环氧树脂包覆层充水钢管中的人工周向缺陷进行了检测。结果表明，频散和衰减小的未受干扰的L（0，2）模态分支部分适合带粘弹性包覆层充液管道中的缺陷检测。但是，在频段0～0．5MHz，随着频率的增加，这些分支部分衰减值逐渐增加，缺陷检测能力也逐渐下降。并且频散和衰减较大，能量主要在水和（或）粘弹性包覆层中传播，不属于未受干扰的L（0，2）模态分支部分的纵向模态不适合检测带粘弹性包覆层充液管道中的缺陷。因此，在对带粘弹性包覆层充液管道进行缺陷检测时，根据频散、衰减和波结构等传播特性选取合适的纵向模态十分重要。

英文摘要：

Our theoretical analysis produces the dispersion curves of longitudinal modes of ultrasonic guided waves in liquid-filled pipes with viscoelastic coatings. To verify the analysis results, we utilize the longitudinal modes to detect the artificial and circumferential defects of water-filled pipes with epoxy resin coatings and the length of 7.12 meters. The detection results show that the unperturbed L（0,2） mode branch with low attenuation and weak dispersion is suitable for detecting the defects in liquid-filled pipes with viscoelastic coatings. However, at the frequency range of 0 - 0.5 MHz, as the frequency increases, the attenuation value of the mode branches is on the increase; their defect detection capacity is on the decrease. On the contrary, the opposite kind of longitudinal mode whose energy propagates mainly in water and/or viscoelastic coatings are not suitable for detecting the defects in liquidfilled pipes with viscoelastic coatings. Therefore, in so doing, it is important to select an appropriate longitudinal mode in accordance with the propagation characteristics such as dispersion, attenuation and wave structures.