Velichko Alexander, Wilcox Paul D
Department of Mechanical Engineering, University of Bristol, Bristol, United Kingdom.
J Acoust Soc Am. 2009 Jun;125(6):3623-31. doi: 10.1121/1.3117441.
The detection of localized defects such as cracks and corrosion in pipes using guided elastic waves is now an established non-destructive testing procedure. However, the prediction of guided wave excitation and scattering in pipes is a complex three-dimensional (3D) problem with many parameters that can generally only be solved using numerical methods. In many important industrial applications, the diameter of a pipe is much larger than wall thickness. In this case an approximate theory is applicable, when a pipe is considered as an unwrapped isotropic plate. In this paper, a technique for obtaining pipe mode amplitudes in terms of the solution to the forced 3D problem on a plate is presented. The same principle is extended to relate guided wave scattering from defects in plates to scattered circumferential modal amplitudes from defects in pipe. This is of practical benefit as the scattering of guided waves by defects in a plate is a much simpler problem than that in a pipe, and one that, in some cases, can be solved using analytical methods. Results are shown that illustrate the application of the method to reflection from through-thickness circumferential cracks in pipes.
利用导波检测管道中的裂纹和腐蚀等局部缺陷，如今已成为一种成熟的无损检测方法。然而，管道中导波的激励和散射预测是一个复杂的三维问题，涉及许多参数，通常只能用数值方法求解。在许多重要的工业应用中，管道直径远大于壁厚。在这种情况下，当把管道视为展开的各向同性板时，一种近似理论是适用的。本文提出了一种根据平板上受迫三维问题的解来获取管道模态振幅的技术。同样的原理被扩展，以将平板中缺陷的导波散射与管道中缺陷的散射周向模态振幅联系起来。这具有实际意义，因为平板中缺陷对导波的散射比管道中的散射问题简单得多，在某些情况下可以用解析方法求解。结果表明了该方法在管道中贯穿壁厚周向裂纹反射方面的应用。
