中文摘要：

从理论上得到了充非粘性液体管道中纵向超声导波的频散方程。分析了纵向模态在充水钢管和带刚性边界的水圆柱体中传播特性。除or．模态，充水钢管中的其他模态均是钢管和带刚性边界的水圆柱体中各模态相互耦合的结果。对于充水钢管中同一模态，在不同频率范围，传播特性差别也较大。在充水和未充水的钢管中进行了激励和接收纵向模态的试验研究。结果表明，在充水钢管中具有模态分支、群速度降低等传播特性。当充水钢管中纵向模态的频带处于钢管中未受干扰的L（0，2）模态分支部分时，能长距离传播，由于频散较小，在传播距离较长时，波形和幅度不会发生明显变化，适合于长距离充水管道的缺陷检测。

英文摘要：

Longitudinal ultrasonic guide wave dispersion equation of inviscid liquid-filled pipe is analyzed theoretically. Propagation characteristics of longitudinal modes in waterfilled steel pipe and water cylinder with rigid boundary are studied. Except ct mode, other modes in wall-filled steel pipe are the coupling of the modes of steel pipe in vacuum and of water cylinder with rigid boundary. To the same mode in water-filled steel pipe, its propagafion characteristics vary greatly with frequency range. Furthermore, longitudinal modes are excited and received in steel pipes filled with and without water experimentally. Results show that propagation characteristics, such as mode branching and group velocity decrease, occur in water-filled steel pipe. When frequency band of longitudinal mode in water-filled steel pipe is in the range of one unperturbed L（0, 2） mode branching of steel pipe in vacuum, the mode has the ability of long distance propagation, and the signal shape and amplitude are retained as it travels long distances for its low dispersion. As a result, the kind of longitudinal mode is suitable to defect detection of long distance waterfilled pipe.