脉冲涡流信号检测与分析

为了对较厚钢板进行缺陷检测，采用对低压大功率的电源进行斩波的方式产生大电流脉冲，设计圆柱形探头，采用激励线圈缓慢放电的方式检测钢板表面缺陷;设计矩形探头，采用激励线圈瞬间放电的方式检测钢板亚表面;对脉冲涡流瞬态感应电压信号进行小波滤噪和幅值归一化处理。实验结果表明，小波滤噪可以提高检测精度，对信号幅值进行归一化处理可以更直接地反映不同深度缺陷产生的曲线间的相互关系，大电流激励的脉冲涡流信号幅值能反映较厚钢板表面和亚表面缺陷深度。

Pulsed Eddy Current Signal Detection and Analysis

In order to detect the defects on thicker steel plate, a high-current pulse was needed, which was generated by chopping the low-voltage high power supply. Moreover, cylindrical probe was designed to detect surface defects of steel plate by slow discharging of exciting coil; rectangular probe was also designed to detect sub-surface defects of steel plate by instant discharging of exciting coil. Then the transient induced voltage signal of pulsed eddy current was processed by the wavelet filtering and amplitude normalization. Experimental results show that the wavelet filtering can improve detecting accuracy and the signals amplitude normalized can reflect the relationship of the defect curves at different depths defects more directly. It is concluded that amplitude of high pulsed eddy current signal excited by high-current can reflect the depths of defects on surface and sub-surface of thicker steel plate effectively.