The variation of the reflection coefficient of extensional guided waves in pipes from defects as a function of defect depth, axial extent, circumferential extent and frequency
The variation of the reflection coefficient of extensional guided waves in pipes from defects as a function of defect depth, axial extent, circumferential extent and frequency
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DOI：
10.1243/095440602761609498
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发表时间：
2002-01-01
影响因子：
2
通讯作者：
Roosenbrand, AG
中科院分区：
文献类型：
--
作者：
Cawley, P;Lowe, MJS;Roosenbrand, AG
采用有限元分析方法，研究了不同直径管道中不同轴向、周向和通厚缺口的拉伸导模反射系数。其中一些预测也得到了实验的验证。对于给定圆周范围和最小轴向范围的部分厚度缺口，反射系数在所有频率下均随深度单调增加，在给定深度处随频率增加。当波长较长时，与管壁厚度相比，反射系数来自部分厚度。给定圆周范围的缺口是缺陷轴向范围的强函数，反射在轴向范围内的最大值约为波长的25%，最小值为0%和50%。反射系数是更高频率下缺陷周向范围的线性函数（频率直径乘积大于约3000千赫毫米），其中射线理论分析解释了这种行为。而在低频时，在给定圆周范围内的反射系数减小。在高频区，透厚缺陷的轴向范围对反射系数影响不大，但在低频区影响较大。高频区域的三维有限元预测表明，可以用相同深度和轴向范围的轴对称缺陷的反射系数乘以相同周向范围的全厚度缺陷的反射系数来预测部分厚度、部分圆周缺陷的反射系数。
The reflection coefficients of extensional guided modes from notches of different axial, circumferential and through-thickness extent in pipes of different diameters have been studied using finite element analysis. A selection of the predictions has also been validated by experiments. For part-thickness notches of a given circumferential extent and minimal axial extent, the reflection coefficient increases monotonically with depth at all frequencies, and increases with frequency at a given depth. When the wavelength is long compared to the pipe wall thickness, the reflection coefficient from part-thickness. notches of a given circumferential extent is a strong function of the defect axial extent, the reflection being a maximum at an axial extent of about 25 per cent of the wavelength and a minimum at 0 and 50 per cent. The reflection coefficient is a linear function of the defect circumferential extent at higher frequencies (with frequency-diameter products greater than about 3000 kHz mm) where a ray theory analysis explains the behaviour, while at low frequencies the reflection coefficient at a given circumferential extent is reduced. In the high-frequency regime, the axial extent of a through-thickness defect has little influence on the reflection coefficient, while it is important at lower frequencies. Three-dimensional finite element predictions in the high-frequency regime have shown that the reflection coefficient from a part-thickness, part-circumferential defect can be predicted by multiplying the reflection coefficient for an axisymmetric defect of the same depth and axial extent by that for a through-thickness defect of the same circumferential extent.