针对传统涡流传感器会忽略特殊方向短裂纹的缺点,提出了一种绝对式科赫分形平面涡流传感器,其激励线圈和信号 拾取线圈均采用基于分形自相似理论的科赫雪花曲线。 首先,对具有相同尺寸的科赫和圆形传感器进行有限元分析。 然后,针 对不同长度、方向、宽度和深度的裂纹,对比分析两种传感器响应信号的差异。 最后,搭建实验系统对有限元分析结果进行验 证。 研究结果表明,对于不同长度、方向和宽度裂纹的探测,有限元分析结果与实验结果定性一致;在 3 和 5 mm 长的裂纹检测 中,科赫传感器输出信号变化量比圆形传感器至少高出 40% ;在不同方向裂纹检测中,对于难检测方向的 90°裂纹,科赫传感器 比圆形传感器至少高出 49% ;在不同宽度裂纹检测中,科赫传感器的信号变化量比圆形传感器至少高出 29% ;在不同深度裂纹 检测中,科赫传感器比圆形传感器至少高出 6% ;相对圆形传感器,科赫传感器对短裂纹探测的优势更加显著。 该研究结果对 平面柔性涡流传感器电磁感应结构的设计具有重要的参考意义。
The traditional eddy current probes may neglect short cracks in special orientation. To address this issue, an absolute Koch planar eddy current probe is proposed. Both the excitation coil and the pickup coil of the probe adopt the Koch snowflake curve based on fractal self-similarity theory. Firstly, the finite element analysis for the Koch probe and the circular probe with the same dimension is conducted. Then, for cracks with different lengths, directions, widths and depths, the difference of response signals of two probes is compared. Finally, an experimental system is established to evaluate the finite element analysis results. Results show that for the inspection of cracks with different lengths, directions and widths, the finite element analysis results are qualitatively consistent with the experimental results. For the inspection of the crack with 3 and 5 mm in lengths, the variations of signals output from the Koch probe are at least 40% higher than those of the circular probe. In the detection of crack in different orientations, the variation of signal output from the Koch probe is at least 49% higher than that of the circular probe for the inspection of the 90° crack which is difficult to be detected. In the detection of crack in different widths, the variation of signal output from the Koch probe is at least 29% higher than that of the circular probe. In the detection of crack in different depths, the variation of signal output from the Koch probe is at least 6% higher than that of the circular probe. The Koch probe has more significant edge for the inspection of short cracks relative to the circular probe. The research result has important reference significance for the design of the electromagnetic structure of planar eddy current probe.