基于调频激励和细化谱分析的多频涡流检测技术研究

Research on multi-frequency eddy current testing technology based on frequency modulation excitation and zoom spectrum analysis

常规多频涡流检测技术在谱分析时,一般采用多个频率的正弦信号同时工作,其激励信号峰值因数较大且检测信号频谱为离散谱。文中提出了一种基于调频信号激励和检测信号细化谱分析的多频涡流检测技术,它不仅降低了激励信号峰值因数,而且检测信号频谱为连续谱。对检测信号施加Tukey窗函数改善谱图,采用Chirp-Z变换计算检测信号频谱,提高谱图的频率分辨率。定义谱图能量、谱图重心、谱图峰度和谱图偏度4个特征量应用于缺陷识别和分类。对于内部缺陷,采用谱图差峰值频率点,定量检测内部缺陷的位置。理论分析和实验结果相一致,验证了所采用方法的正确性。

In conventional multi-frequency eddy current testing（MFECT） technique,the excitation signal is synthesized synchronously from many sine signals when eddy current testing signals are analyzed in frequency domain.The crest factor of the excitation signal is rather large and the testing signal spectrum is discrete.This paper proposes a new MFECT technology,which adopts frequency modulation excitation and zoom spectrum analysis.The new technology reduces the crest factor of the excitation signal and the test signal spectrum becomes continuous.Tukey window is exerted to the test signal to improve its spectrum.Chrip-Z transform is adopted to calculate the testing signal spectrum,which heighten its frequency resolution.Spectrum energy,spectrum barycenter,spectrum kurtosis and spectrum skewness are defined to identify and classify the defects.The position of inner defects is quantitatively detected using the peak frequency point of the spectrum difference.Theoretical analysis and experimental data agree with each other,which verifies the correctness of the employed method.