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厚壁铸造奥氏体不锈钢(cast austenitic stainless steel,CASS)具有弹性各向异性粗晶结构,超声检测过程中会引起强烈的结构噪声和散射衰减,极大地降低了缺陷回波信噪比。针对上述问题,本文以基于电子背散射衍射技术构建的CASS超声检测模型为对象,仿真研究了相位相干成像(phase coherence imaging,PCI)算法的信噪比增强效果。深度50mm的3边钻孔的成像结果表明:PCI算法可通过放大相位分布对幅值的贡献有效抑制结构噪声和提高信噪比。经统计,PCI图像的信噪比为34.56dB,较全聚焦图像提高了14.41dB,较B扫描图像提高了25.44dB。
Cast austenitic stainless steel (CASS) with thick wall has elastic anisotropic coarse grain structure, which causes strong structural noise and scattering attenuation during ultrasonic testing, and greatly reduces the signal-to-noise ratio of defect echo. In order to solve the above problems, this dissertation takes CASS ultrasonic detection model based on electron backscatter diffraction technology as object, and simulates the signal to noise enhancement effect of phase coherence imaging (PCI) algorithm. Imaging results of the 503 borehole at a depth of 50mm show that the PCI algorithm can effectively suppress the structure noise and improve the signal-to-noise ratio by amplifying the contribution of the phase distribution to the amplitude. The statistics show that the SNR of PCI image is 34.56dB, which is 14.41dB higher than that of full-focus image and 25.44dB higher than that of B-scan image.