ABSRACT The relative merits of three different periodic permanent magnet (PPM) configurations are investigated for the generation of SH0 waves with a Lorentz-force electromagnetic acoustic transducer (EMAT) on a 60-mm diameter aluminum pipe. Such transducers are often used for checking the integrity of pipelines. It was found that minimizing lift-off by using magnets machined to the same curvature as the pipe increased the magnitude of the generated wave by over 70%, compared to the use of a PPM with a single planar surface. A less expensive and more versatile alternative is to use a PPM for which the two lines of magnets are angled with respect to each other to realize closer average proximity to the pipe surface. Numerical simulations and experiments indicated that the amplitude of a SH0 wave with this magnet configuration would still be approximately 60% higher than the reference case of a PPM with a single planar surface.

中文翻译：

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洛伦兹力 EMAT 中周期性永磁体配置的优化

摘要研究了三种不同周期永磁 (PPM) 配置的相对优点，用于在 60 毫米直径铝管上使用洛伦兹力电磁声换能器 (EMAT) 生成 SH0 波。这种传感器通常用于检查管道的完整性。研究发现，与使用具有单个平面表面的 PPM 相比，通过使用机械加工成与管道相同曲率的磁体来最大限度地减少抬升，所产生的波的幅度增加了 70% 以上。一种更便宜且更通用的替代方案是使用 PPM，其中两条磁铁线相对于彼此成角度，以实现更接近管道表面的平均接近度。