Hilbert-Huang变换在非线性超声无损检测中的应用

Application of Hilbert-Huang transforms for nonlinear ultrasonic nondestructive testing

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。

The Hilbert-Huang transform was used to improve estimates of the position and relative size of defects for nonlinear ultrasonic nondestructive testing. The detected signal in stainless steel is nonlinear, non-stationary and has a low signal-to-noise ratio. The instantaneous frequency can indicate the defect position, which the instantaneous amplitude can characterize the relative defect size. The method can detect a φ 0.8 mm flat-bottom hole （at a depth of 65 mm） in a stainless steel sample of average grain size 0. 6 mm. Therefore, the Hilbert-Huang transform provides an improved ability to detect defects through time-resolved testing.