多层介质内部缺陷远聚焦成像方法研究

Research on Far-focused Pixel-based Imaging Method of Defects inside Multilayer Media

针对常规超声成像方法在多层介质内部缺陷检测中存在的缺陷成像不清晰、定位不准确的问题,开展基于远聚焦像素成像算法的多层介质内部缺陷成像研究。对多层介质引起的声传播特性变化进行分析,以三层介质模型为例,通过仿真分析,将基于时间最短原理的射线追踪法和斯涅尔定理的声传播路径计算结果进行对比,仿真结果表明,在计算的耗时及计算结果的精度上,射线追踪法都高于斯涅尔定理。通过理论推导建立多层介质传播衰减模型,确定透射补偿系数、扩散衰减补偿系数及指向性校准系数,实验结果表明,衰减补偿后缺陷中心的成像幅值提高了6.3 dB,优化后的成像方法能够实现对多层介质内部缺陷的检测,缺陷的定位误差小于0.4 mm,尺寸测量误差小于0.35 mm 2。

To address the problems of unclear imaging and inaccurate positioning of defects in the conventional ultrasonic imaging methods for the detection of defects inside multilayer media,the research of the imaging of defects inside multilayer media was carried out based on the far-focused pixel-based imaging algorithm.The changes of acoustic propagation characteristics caused by multilayer media were analyzed,and the results of acoustic propagation path calculation were compared based on the ray-tracing method and Snell's theorem by simulation analysis with the three-layer media model.Through the theoretical derivation,a multilayer medium propagation attenuation model was established to determine the transmission compensation coefficient,diffusion attenuation compensation coefficient and directivity calibration coefficient.The experimental results show that the imaging amplitude of the defect center is improved by 6.3 dB after the attenuation compensation,and the optimized imaging method may achieve the detection of defects inside the multilayer media with the defect localization errors less than 0.4 mm and the dimensional measurement errors less than 0.35 mm 2.