The reflection of the fundamental torsional mode from cracks and notches in pipes
The reflection of the fundamental torsional mode from cracks and notches in pipes
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DOI：
10.1121/1.1582439
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发表时间：
2003-08-01
影响因子：
2.4
通讯作者：
Roosenbrand, AG
中科院分区：
文献类型：
--
作者：
Demma, A;Cawley, P;Roosenbrand, AG
在10 - 300 kHz频率范围内，对管道缺陷的T（0，1）模式反射进行了定量研究，并通过选定情况下的实验验证了有限元预测。考虑了轴向尺寸为零的裂纹类缺陷和轴向尺寸变化的缺口。结果表明，轴对称裂纹的反射系数在所有频率下随深度单调增加，在任意给定深度下随频率增加。在感兴趣的频率范围内，在轴对称缺陷处没有模式转换。对于非轴对称裂纹，反射系数在相对较高的频率下是缺陷周向范围的大致线性函数，在较低的周向范围下的反射系数低于在较低频率下的线性预测。对于非轴对称缺陷，通常可以看到到F（1，2）模式的模式转换，并且在较低频率下也会产生F（1，3）模式。深度和圆周范围是控制裂纹反射的参数;当考虑具有有限轴向范围而不是裂纹的凹口时，从凹口的开始和结束的反射之间的干涉导致反射系数作为凹口的轴向范围的函数的周期性变化。用波数-缺陷尺寸乘积ka解释了结果。当ka 1时，可以看到低频散射行为。(C)2003年，美国声学学会。
A quantitative study of the reflection of the T(0,1) mode from defects in pipes in the frequency range 10-300 kHz has been carried out, finite element predictions being validated by experiments on selected cases. Both cracklike defects with zero axial extent and notches with varying axial extents have been considered. The results show that the reflection coefficient from axisymmetric cracks increases monotonically with depth at all frequencies and increases with frequency at any given depth. In the frequency range of interest there is no mode conversion at axisymmetric defects. With nonaxisymmetric cracks, the reflection coefficient is a roughly linear function of the circumferential extent of the defect at relatively high frequencies, the reflection coefficient at low circumferential extents falling below the linear prediction at lower frequencies. With nonaxisymmetric defects, mode conversion to the F(1,2) mode is generally seen, and at lower frequencies the F( 1,3) mode is also produced. The depth and circumferential extent are the parameters controlling the reflection from cracks; when notches having finite axial extent, rather than cracks, are considered, interference between the reflections from the start and the end of the notch causes a periodic variation of the reflection coefficient as a function of the axial extent of the notch. The results have been explained in terms of the wave-number-defect size product, ka. Low frequency scattering behavior is seen when ka 1. (C) 2003 Acoustical Society of America.