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为了提高非线性超声无损检测方法对缺陷位置和相对大小的表征能力,该文将H ilbert-Huang变换方法用于非线性超声无损检测信号的处理。粗晶奥氏体不锈钢材料的非线性超声无损检测信号具有非线性、非稳态和低信噪比的特性,H ilbert-Huang变换对此类信号的特征提取具有独特的优势。实验结果表明:通过H ilbert-Huang变换的瞬时频率能够确定缺陷位置,瞬时幅度可表征缺陷的相对大小;该方法达到了对0.6mm晶粒平均直径的粗晶奥氏体不锈钢中65 mm深、0.8 mm平底孔的小缺陷检出能力,说明H ilbert-Huang变换有效提高了非线性超声无损检测的缺陷表征能力。
In order to improve the characterization of the location and the relative size of the non-linear ultrasonic nondestructive testing method, the Hilbert-Huang transform method is applied to the non-linear ultrasonic non-destructive testing signal processing. The nonlinear ultrasonic non-destructive testing signal of the coarse-grained austenitic stainless steel has the characteristics of non-linearity, unsteady state and low signal-to-noise ratio. The Hilbert-Huang transform has unique advantages for the feature extraction of such signals. The experimental results show that the instantaneous frequency of Hilbert-Huang transform can determine the position of the defect, and the instantaneous amplitude can characterize the relative size of the defect. The method achieves the accuracy of 65 mm in the coarse grain austenitic stainless steel with an average grain diameter of 0.6 mm, 0.8 mm flat-bottomed hole defects detection ability, indicating that Hilbert-Huang transform effectively improve the non-linear ultrasonic non-destructive testing defect characterization ability.