The laser ultrasonic technique (LUT) enables the analysis of complex signals and the extraction of the features of defects. The time-domain features can be used to quantify various defects, but are negatively affected by the coupling efficiency, measurement noise, and surface roughness during LUT. This paper describes defect analysis methods based on the power spectral density and wavelet packet energy. Defects are characterized using the power of low-frequency components after wavelet decomposition and the wavelet packet energy, and then linear relationships are established for two defect types. The R² values of the linear fitting for the characteristic variables of the defect are greater than 0.96. The experimental results show that the proposed methods provide effective and quantitative characterization of the defect size from laser ultrasonic signals.

中文翻译：

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基于功率谱密度分析和小波包能量的激光超声缺陷测量

激光超声技术 (LUT) 能够分析复杂信号并提取缺陷特征。时域特征可用于量化各种缺陷，但会受到 LUT 期间耦合效率、测量噪声和表面粗糙度的负面影响。本文介绍了基于功率谱密度和小波包能量的缺陷分析方法。利用小波分解后的低频分量功率和小波包能量对缺陷进行表征，然后建立两种缺陷类型的线性关系。R ²缺陷特征变量的线性拟合值大于 0.96。实验结果表明，所提出的方法提供了激光超声信号缺陷尺寸的有效和定量表征。