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常规矢量全聚焦成像仅利用检测信号的幅值信息,其成像质量受噪声、栅瓣和旁瓣等的影响大。综合利用检测信号的幅值和相位信息,本文提出两种相位加权的矢量全聚焦成像方法。首先,对全矩阵数据的相位信息进行分析,提取出两种相位特征参数:相位一致因子(Phase Coherence Factor:PCF)和极性一致因子(Sign Coherence Factor:SCF);然后,将全阵列划分为若干子阵列,分别利用两种相位特征参数对各个子阵列的成像幅值进行加权,求取加权幅值特征向量;最后,对所有子阵列的加权特征向量进行合成,得到两种加权的矢量全聚焦成像,并从中提取出裂纹方向及尺寸等特征信息。将三种矢量全聚焦成像方法应用于不同缺陷检测仿真及实验验证,结果表明,3种方法均可以实现缺陷方向识别与长度定量测量;但相位加权矢量全聚焦成像效果明显优于常规矢量全聚焦成像结果,其成像信噪比及分辨率更高,缺陷角度及长度测量结果更准确。本文研究工作为缺陷无损评价提供了可行的技术手段。
Conventional vectorial all-focus imaging utilizes only the amplitude information of the detection signal, and its imaging quality is greatly affected by noise, grating lobes and side lobes. By comprehensively using the amplitude and phase information of the detection signal, two phase-weighted vector full-focus imaging methods are proposed in this paper. Firstly, the phase information of the whole matrix data is analyzed to extract two kinds of phase characteristic parameters: Phase Coherence Factor (PCF) and Sign Coherence Factor (SCF); then, the whole array is divided into A plurality of sub-arrays are respectively used to weight the imaging magnitudes of the respective sub-arrays by using two phase characteristic parameters respectively to obtain the weighted amplitude eigenvectors. Finally, the weighted eigenvectors of all the subarrays are synthesized to obtain two weighted vectors Focused imaging, and extracted from the crack direction and size and other characteristic information. The three kinds of vector full-focus imaging methods are applied to the simulation and experimental verification of different defect detection. The results show that all three methods can realize the defect direction identification and the length quantitative measurement; however, the phase-weighted vector all-focus imaging is obviously better than the conventional vector- Imaging results, the imaging signal to noise ratio and higher resolution, defect angle and length measurements more accurate. The work in this thesis provides a feasible technical means for the non-destructive evaluation of defects.