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针对航空涡轮盘难检区域缺陷的超声相控阵检测技术,分析了检测信号及图像特征,提出了检测信号的小波包软阈值降噪方法,并对小波阈值进行改进,最后基于降噪后的信号进行了相控阵图像重构。结果表明:缺陷特征信号几乎分布于检测信号的整个频域范围,单纯的频域滤波必然导致缺陷信号的损失;基于改进的小波包阈值,并且有针对性地选择部分分解信号进行滤波降噪,可在较好保留有用信号的同时滤除噪声信号,有效地提高了检测信号信噪比及检测图像分辨率,对于提高涡轮盘的超声相控阵检测能力具有重要作用。
Aiming at the ultrasonic phased array detection technology of the regional defect of aviation turbine disk, the detection signals and the image characteristics are analyzed. The wavelet packet soft threshold denoising method of detecting signals is proposed and the wavelet threshold is improved. Finally, The signal is phased array image reconstruction. The results show that the defect signal is almost distributed over the entire frequency domain of the detection signal. The simple frequency domain filtering will inevitably lead to the loss of the defect signal. Based on the improved wavelet packet threshold and the selective filtering of the partially decomposed signal, Which can effectively preserve the useful signal and filter out the noise signal at the same time, effectively improve the signal-to-noise ratio of the detection signal and detect the resolution of the image, which plays an important role in improving the detection capability of the ultrasonic phased array of the turbine disk.