柔性差测量科赫分形涡流传感器内部裂纹检测

柔性涡流传感器由于其可变形性有望被用于复杂形貌结构的无损检测。 柔性科赫分形涡流传感器由于其局部微结构 对涡流的调理效果,对各方向短裂纹检测性能的一致性较高,但该传感器对于近表面及内部裂纹的检测还未展开研究。 构建了 差测量传感器的等效电路模型;通过仿真方法研究了涡流分布随深度的演化规律;通过试验方法,研究了传感器对覆盖不同厚 度铝板预制裂纹试块的检测效果。 有限元结果表明,随着深度的增加,涡流密度减小,集中性降低,分布的形态与其在表面差异 越来越大,形态由雪花状向圆形演化。 试验结果表明,传感器输出信号随着覆盖层厚度的增加而减弱;当激励频率为 10 kHz 时,传感器可检测到裂纹时覆盖铝板最大厚度为 2. 0 mm。

Flexible differential pick-up Koch fractal eddy current sensor for internal crack detection

Due to deformability, flexible eddy current sensors are used in nondestructive testing for complex structures. The flexible Koch fractal eddy current sensor consistently detects short cracks in all directions due to the eddy current conditioning effect of its local microstructure. However, the detection of near-surface and internal cracks has not been studied. This article formulates the equivalent circuit model of the difference pick-up sensor. The evolution of eddy current distribution with depth is studied by simulation method. Through the experimental method, the detection effect of the sensor on the prefabricated crack specimen covered with different thicknesses of aluminum plate is studied. The finite element results show that, with the increase of depth, the eddy current density decreases, the concentration decreases, and the distribution pattern is more and more different from that on the surface. The eddy current shape changes from snowflake to circular. The experimental results show that the output signal of the sensor decreases with the increase of the thickness of the covering layer. When the excitation frequency is 10 kHz, the sensor can detect the maximum thickness of the covered aluminum plate when the crack is 2. 0 mm.