ABSTRACT During fabrication and practical service, nonmagnetic tubes are prone to the External Wall-thickness Loss (EWL) which leaves the tubes vulnerable to structural failure. In this paper, a bobbin-typed electromagnetic acoustic transducer is proposed for tube inspection. The feasibility of EWL evaluation by using the proposed transducer is investigated via simulations and experiments. In order for efficient simulations of Electromagnetic Acoustic Transduction (EMAT), the hybrid modeling integrating the analytical modeling and finite element modeling is established. Closed-form expressions particularly regarding the EMAT-related field quantities of electromagnetics are formulated via the Extended Truncated Region Eigenfunction Expansion (ETREE) modeling. Simulations by using the hybrid model indicate that the proposed transducer is capable of evaluating EWL in nonmagnetic tubes. In parallel, experiments with the fabricated transducer have been carried out. The experimental results are supportive of the conclusion drawn from simulations. From simulations and experiments, it can be found that EWL evaluation with the proposed bobbin-typed electromagnetic acoustic transducer is feasible, which could benefit the real-time and in-situ nondestructive evaluation of nonmagnetic tubes.

中文翻译：

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使用线轴型电磁声换能器评价非磁性管外壁厚度损失的可行性研究

摘要 在制造和实际使用过程中，非磁性管容易出现外壁厚度损失 (EWL)，这使得管容易发生结构故障。在本文中，提出了一种用于管道检查的线轴型电磁声换能器。通过模拟和实验研究了使用所提出的换能器进行 EWL 评估的可行性。为了有效地模拟电磁声换能（EMAT），建立了分析建模和有限元建模相结合的混合建模。通过扩展截断区域特征函数展开 (ETREE) 建模制定了闭式表达式，特别是关于与 EMAT 相关的电磁场量。使用混合模型的模拟表明，所提出的换能器能够评估非磁性管中的 EWL。同时，对制造的换能器进行了实验。实验结果支持了模拟得出的结论。从模拟和实验中可以发现，使用所提出的线轴型电磁声换能器进行 EWL 评估是可行的，这有利于非磁性管的实时和原位无损评估。