ABSTRACT In this study, the discrete wavelet transform (DWT)-based signal processing methodology is applied for eliminating noise due to permeability variations in saturation eddy current (EC) testing signals from nickel tubes. The nickel tubes are of 0.3 mm thickness and 6.6 mm outer diameter. Systematic studies have been carried out to optimize the wavelet functions, number of decomposition levels, and thresholding algorithm for DWT processing based on the signal-to-noise ratio (SNR). The DWT processing has enabled reliable detection of a 0.1 mm deep notch located on the inner surface of the tubes meeting its stringent quality requirements. Application of signal processing-based methodology has resulted in an improvement in SNR of 11.4 dB as against 5.1 dB for the raw signals.

中文翻译：

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使用离散小波变换 (WDT) 处理方法通过涡流 (EC) 测试对薄壁镍管进行质量保证

摘要 在这项研究中，基于离散小波变换 (DWT) 的信号处理方法用于消除由于镍管饱和涡流 (EC) 测试信号中的磁导率变化引起的噪声。镍管的厚度为 0.3 毫米，外径为 6.6 毫米。已经进行了系统研究，以优化基于信噪比 (SNR) 的 DWT 处理的小波函数、分解级别数和阈值算法。DWT 处理能够可靠检测位于管内表面的 0.1 毫米深凹口，满足其严格的质量要求。基于信号处理的方法的应用导致 SNR 提高了 11.4 dB，而原始信号的 SNR 提高了 5.1 dB。