ABSTRACT An eddy-current testing (ECT) method with miniature-printed circuit board (PCB)-based planar spiral coils for carbon fibre-reinforced plastics (CFRP) is proposed in this paper. First, the electromagnetic model of the rectangular spiral coil is discussed, thus the analytical expressions of the impedance in free-space, and impedance change due to the eddy-current are provided. Next, the intensity areas of impedance change of a certain PCB-based planar spiral coil for metal and CFRP are theoretically given with different frequencies. Then, an ECT system for CFRP is established, and a resonant probe with a PCB-coil is designed by coupling to the parasitic capacitance of the cables. Finally, a series of ECT experiments for unidirectional, four-directional angle-ply, and orthogonal woven CFRP laminates are conducted. The results show that the minimum defect depth that can be detected on the unidirectional CFRP laminate reaches 0.1 mm. This study is an effective attempt for CFRP ECT based on planar spiral coils fabricated by PCB technology and lays the foundation for further ECT large-scale array scanners manufactured by PCB technology.

中文翻译：

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带有微型 PCB 螺旋线圈的 ECT 技术在 CFRP 层压板可视化中的应用

摘要 本文提出了一种用于碳纤维增强塑料 (CFRP) 的基于微型印刷电路板 (PCB) 的平面螺旋线圈的涡流检测 (ECT) 方法。首先讨论了矩形螺旋线圈的电磁模型，从而给出了自由空间阻抗和涡流引起的阻抗变化的解析表达式。接下来，从理论上给出了金属和CFRP的某PCB基平面螺旋线圈在不同频率下阻抗变化的强度区域。然后，建立了用于 CFRP 的 ECT 系统，并通过耦合到电缆的寄生电容设计了带有 PCB 线圈的谐振探头。最后，对单向、四向角层和正交编织 CFRP 层压板进行了一系列 ECT 实验。结果表明，在单向CFRP层压板上可检测到的最小缺陷深度达到0.1 mm。本研究是对基于PCB技术制造的平面螺旋线圈的CFRP ECT的有效尝试，为进一步采用PCB技术制造的ECT大型阵列扫描仪奠定了基础。