Department of Mechanical Engineering, École de Technologie Supérieure, Montreal, QC H3C 1K3, Canada.
Sensors (Basel). 2021 Oct 7;21(19):6665. doi: 10.3390/s21196665.
The reliability of the ultrasonic phased array total focusing method (TFM) imaging of parts with curved geometries depends on many factors, one being the probe standoff. Strong artifacts and resolution loss are introduced by some surface profile and standoff combinations, making it impossible to identify defects. This paper, therefore, introduces a probe standoff optimization method (PSOM) to mitigate such effects. Based on a point spread function analysis, the PSOM algorithm finds the standoff with the lowest main lobe width and side lobe level values. Validation experiments were conducted and the TFM imaging performance compared with the PSOM predictions. The experiments consisted of the inspection of concave and convex parts with amplitudes of 0, 5 and 15 λ, at 12 standoffs varying from 20 to 130 mm. Three internal side-drilled holes at different depths were used as targets. To investigate how the optimal probe standoff improves the TFM, two metrics were used: the signal-to-artifact ratio (SAR) and the array performance indicator (API). The PSF characteristics predicted by the PSOM agreed with the quality of TFM images. A considerable TFM improvement was demonstrated at the optimal standoff calculated by the PSOM. The API of a convex specimen's TFM was minimized, and the SAR gained up to 13 dB, while the image of a concave specimen gained up to 33 dB in SAR.
超声相控阵全聚焦方法（TFM）对具有曲面几何形状的部件成像的可靠性取决于许多因素，其中之一是探头间距。某些表面轮廓和探头间距组合会引入强烈的伪影和分辨率损失，从而无法识别缺陷。因此，本文介绍了一种探头间距优化方法（PSOM）来减轻这种影响。基于点扩散函数分析，PSOM 算法找到了主瓣宽度和旁瓣电平值最低的探头间距。进行了验证实验，并将 TFM 成像性能与 PSOM 预测进行了比较。实验包括对具有 0、5 和 15λ 幅度的凹面和凸面部件进行检测，探头间距为 12 个，范围从 20 到 130mm。三个不同深度的内部侧钻孔用作目标。为了研究最佳探头间距如何改善 TFM，使用了两个指标：信号-伪影比（SAR）和阵列性能指标（API）。PSOM 预测的 PSF 特性与 TFM 图像的质量一致。通过 PSOM 计算出的最佳探头间距可显著提高 TFM。凸面试样 TFM 的 API 最小化，SAR 增益高达 13dB，而凹面试样的 SAR 增益高达 33dB。
