充粘液管材中超声纵向轴对称导波的频散特性分析

模拟分析充粘液管内径-壁厚比和超声纵向轴对称导波波包宽度的关系。考虑了衰减的情况下,在各传播距离、频厚积和激发脉冲周数上,采用脉冲回波法,分析了导波的频散特性。结果表明:对于特定的材料,当频厚积一定时,充粘液管材中传播的导波特性只与内径-壁厚比有关;各高阶模式的截止频厚积随内径-壁厚比的增大而减小。用L(0,1)模式检测内径-壁厚比在4附近的充粘液管时灵敏度较低;而用L(0,2)模式检测内径-壁厚比在9.2附近的管时灵敏度较低。对于不同内径-壁厚比的充粘液管,检测中应当用不同的纵向轴对称导波模式,所用的激发脉冲周数和频厚积也应当不同。

Analysis of dispersion characteristics of ultrasonic longitudinal axisymmetric guided-waves in viscous liquid-filled pipes

The relationship between wave-packet duration of ultrasonic longitudinal axisymmetric guided waves with lower order and Inner-Radius-Thickness Ratio (IRTR) of viscous liquid-filled pipes are simulation analyzed. In the condition of take into account the attenuations, at various propagation distances, various frequency-thickness products (fd) and various cycle numbers of the input pulse signal, the dispersion characteristics of guided waves are also analyzed using pulse echo method. The results shown that for a certain material and fd of testing, the dispersion characteristics of guided waves in viscous liquid-filled pipes are only related to IRTR. The cut-off fd of higher order modes will reduces with the increase of IRTR. When using L(0,1) mode to detect the defect of viscous liquid-filled pipes with IRTR at about 4, it has a lower sensitivity. While using L(0,2) mode, it has a lower sensitivity at about 9.2 of IRTR. For viscous liquid-filled pipes of different IRTR, one should select different modes, and chooses different cycle numbers and different fd.