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分析了位于导电平板上方任意张角的聚焦线圈所产生的线性瞬态电磁场。在单个倾斜圆环线圈电磁模型基础上,推导出了聚焦线圈电磁场量的复频域解析表达式。运用这些表达式和拉氏反变换的数值方法计算了瞬态响应,并讨论了瞬态响应与线圈张角以及平板参数的关系。研究发现,随着线圈张角变小,导体内部涡流密度分布更加集中、时域波形更为陡峭,线圈中感应电动势的峰值变大;平板导体的电导率和磁导率对涡流密度与线圈感应电动势波形影响较大,板厚对瞬态响应影响较小。通过与商用软件仿真结果的对比验证了该文模型与方法,其结果可以用于脉冲涡流检测的信号预测与解释以及探头结构的设计。
The linear transient electromagnetic field generated by the focusing coil at any angle above the conducting plate is analyzed. Based on the electromagnetic model of a single inclined toroidal coil, the complex frequency domain analytical expression of the electromagnetic field of the focusing coil is deduced. The transient response was calculated by using these expressions and Laplace inverse numerical method. The relationship between transient response and coil opening angle and plate parameters was also discussed. The results show that with the decrease of the coil angle, the eddy current density distribution is more concentrated in the conductor, the waveform in the time domain is steeper, and the peak value of the induced electromotive force in the coil becomes larger. The influence of the conductivity and permeability of the plate conductor on the eddy current density and coil induction The influence of the electromotive force waveform is larger, and the plate thickness has less influence on the transient response. The model and method are verified by comparison with commercial software simulation results. The results can be used to predict and explain the signal of pulse eddy current detection and the design of the probe structure.