三层平板导体厚度及电导率的涡流检测

Thickness and Conductivity Measurement of Three-Layered Plane Conductors Based on Harmonic Eddy Current Testing

为一次性检测出三层不导磁平板导体的各层厚度及各层电导率,利用电磁场理论建立了正问题求解模型,推导了三层不导磁平板导体上方空心圆柱线圈的散射场阻抗表达式,试验验证了该表达式的正确性;建立了反问题求解模型,使用最优化算法计算了反问题的解,根据一组不同激励频率点的线圈散射场阻抗测量值,计算出了三层不导磁平板导体的各层厚度及各层电导率。试验结果表明,反演结果可靠。

For the purpose of measuring thickness and conductivity of all the layers of three-layered plane conductors at one time, a forward problem model was built. In the model, analytic solution of an air-core cylindrical coil＇s impedance caused by eddy current in three-layered plane conductors was presented. Calculated results based on the presented analytic solution agreed well with the experiment results. After this, an inverse problem was put forward. The ultimate goal was to calculate the thickness and conductivity of all the layers of three-layered plane conductors when the probe impedance caused by eddy current at several frequency points was acquired. Combined with the analytic expressions, optimization algorithm was employed to solve the inverse problem. Inversion results for the three-layered plane conductors showed that the proposed method was practicable and the accuracy was good.