铝合金焊缝电涡流磁场信号的非线性特征提取及分类方法研究*

摘要

GMR (giant magneto resistance) sensor can be used to measure the eddy current magnetic field of the Al-alloy weld. The nonlinear time series analysis method is introduced to study the signals from the eddy current magnetic field of the weld in three different states, which include good, lack of penetration, and clustered blowhole weld. Several nonlinear characteristic parameters, such as Lyapunov exponent and correlation dimension etc., are extracted. The results show that the eddy current magnetic field of the Al-alloy weld has distinguished chaotic features. Analysis of the Lempel-Ziv complexity and approximate entropy for different signals leads to the conclusion that these two complex measures are sensitive to the eddy current magnetic field of the weld zone. Through these methods, nonlinear characteristics of eddy current magnetic field of the weld can be obtained for identifying and classifying the type of the weld, which will serve as an efficient supplementary diagnostic tool to reveal different patterns of the welds.%采用巨磁电阻(GMR)传感器对铝合金惰性气体保护焊焊缝的涡流电磁信号进行提取。采用非线性特征分析的方法对良好、含有密集气孔和未焊透三种不同状态焊缝的涡流电磁信号的特性进行分析。提取焊缝涡流电磁信号的Lyapunov指数、关联维数等参数进行分析，分析结果表明焊缝涡流电磁信号具有明显的非线性混沌特性。采用Lempel-Ziv复杂度和近似熵测度分析三种状态焊缝涡流电磁信号的复杂度，结果表明：Lempel-Ziv 复杂度和近似熵对不同状态焊缝的涡流电磁信号是敏感的，可以得到焊缝的电磁信号的非线性特征，并对焊缝的类别进行分类辨识，为分析焊缝的不同状态提供了一种有效的辅助工具和方法。