多频涡流的谱分析和缺陷分类技术研究

Research on Spectrogram Method and Flaw Classification of Multi-frequency Eddy Current

多频涡流检测技术是一项重要的无损检测技术,它可以有效地实现多参数检测和干扰抑制。针对普通单频涡流检测方法只能实现缺陷检测而难以实现缺陷分类的问题,提出一种采用线性调频信号激励涡流传感器和检测信号谱分析的多频涡流检测方法。该方法采用线性调频信号激励位于交流电桥中的线圈涡流传感器,放大和采集桥路输出信号进行谱分析来识别缺陷的特征。根据谱图能量的变化,可以检测出缺陷;同时,为了有效地实现缺陷分类,提出一种新的称为'谱图重心偏移'的缺陷分类方法。与传统多频涡流检测方法相比较,该方法具有检测时间短和系统成本低等优点。理论分析和试验结果相一致,验证了所采用方法的正确性。

Multi-frequency eddy current test（MFECT） is an important NDT technology,and it can realize multi-parameter detection and interference suppression effectively.Aiming at the problem that normal single frequency eddy current test can only detect flaws but can＇t realize flaw classification,a new MFECT method which adopts linear frequency modulation（LFM） signal exciting and detection signal spectrogram analysis is proposed.The probe-coil in AC bridge is excited by LFM signal,and the output signal of AC bridge is amplified and sampled to identify flaw characteristic by spectrogram method.The flaw can be detected according to spectrogram energy variation,besides,with the purpose of flaw classification,a new method called spectrogram barycenter excursion is proposed to realize flaw classification.Compared with traditional multi-frequency eddy current test method,it has the merits of short detection time and low system cost.The agreement between theory and experiment verifies the correctness of the employed method.