The influence of sharp edges in corrosion profiles on the reflection of guided waves
The influence of sharp edges in corrosion profiles on the reflection of guided waves
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DOI：
10.1016/j.ndteint.2012.08.008
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发表时间：
2012-11-01
影响因子：
4.2
通讯作者：
Cawley, Peter
中科院分区：
文献类型：
--
作者：
Carandente, Rosalba;Lovstad, Anders;Cawley, Peter
由于实践中遇到的轮廓的复杂性，引导超声波确定真实腐蚀缺陷尺寸的能力仍然具有挑战性，在小圆周区域上深度突然发生较大变化的缺陷尤其成问题。本文的目的是通过分离缺陷轮廓的低空间频率分量和高空间频率分量并分析它们对反射系数（RC）频谱的影响来研究缺陷反射的频率依赖性，从而诊断缺陷轮廓是否急剧变化。已经发现，低通空间频率仅在低频处产生显着的反射；类似地，高空间频率仅在高频处才会导致显着的反射。对于在被全面腐蚀包围的小区域内深度急剧变化的缺陷，高空间频率的反射对 RC 的最大峰值有显着贡献。相比之下，在更渐进的腐蚀斑块的情况下，其高空间频率对最大峰值 RC 的贡献非常有限。此外，通过叠加缺陷的低空间频率内容和高空间频率内容计算出的 RC 可以很好地近似完整轮廓的 RC。提出了一种基于 RC 谱分析来诊断腐蚀斑块中是否存在锐边的方法，并定义了该过程的局限性。主要的有限元结果经过实验验证。 (C) 2012 Elsevier Ltd. 保留所有权利。
The capacity of guided ultrasonic waves to size real corrosion defects remains challenging due to the complexity of the profiles encountered in practice, defects with large sudden changes in depth over a small circumferential region being particularly problematic. The objective of this paper is to diagnose whether the defect profile changes sharply by studying the frequency dependence of the reflection from the defect by separating the low and high spatial frequency components of defect profiles and analyzing their effect on the reflection coefficient (RC) spectrum. It has been found that the low pass spatial frequencies give significant reflection only at low frequencies; similarly, high spatial frequencies result in significant reflection only at high frequencies. For a defect with a sharp change in depth within a small region otherwise surrounded by general corrosion, the reflection from the high spatial frequencies contributes significantly to the maximum peak of the RC. In contrast, in the case of a more gradual corrosion patch, its high spatial frequencies make only a very modest contribution to the maximum peak RC. Also, the RC calculated by superposition of the low and high spatial frequency content of a defect gives a good approximation to the RC from the full profile. A method to diagnose the presence of sharp edges in corrosion patches based on the analysis of the RC spectrum is proposed, and the limitations of the procedure are defined. The main FE results are validated experimentally. (C) 2012 Elsevier Ltd. All rights reserved.