• CN:11-2187/TH
  • ISSN:0577-6686

›› 2007, Vol. 43 ›› Issue (10): 103-107.

• 论文 • 上一篇    下一篇

超声渡越时差法检测图像中裂纹端部信号的识别

迟大钊;刚铁;盛朝阳   

  1. 哈尔滨工业大学现代焊接生产技术国家重点实验室
  • 发布日期:2007-10-15

METHOD FOR CRACK TIP RECOGNITION IN AN ULTRASONIC TIME OF FLIGHT DIFFRACTION IMAGE

CHI Dazhao;GANG Tie;SHENG Zhaoyang   

  1. State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology
  • Published:2007-10-15

摘要: 利用超声渡越时差法(Time of flight diffraction,TOFD)对含有人工内部裂纹的铝合金试块进行检测。为了提高检测精度,对低分辨率双曲线特征的B扫描图像进行处理。根据超声TOFD法的检测特点,建立B扫描图像合成孔径聚焦(Synthetic aperture focusing technique,SAFT)重建的数学模型,实现图像的增强处理。灰度极值检测的预处理提高了图像纵向时间分辨率;后继的SAFT处理有效地抑制图像中的冗余信息,提高缺陷的横向方位分辨率,从而提出一种灰度极值检测与SAFT相结合的B扫描图像处理方法。为了减少SAFT算法的计算时间,采用加运算窗处理,并确定合适的运算窗宽度。结果表明,该方法能有效地增强图像中检测目标,进而能够准确、快速地检测出裂纹上、下端部在模拟试块中的位置。

关键词: 超声渡越时差法, 合成孔径聚焦, 裂纹检测

Abstract: An aluminum sample containing artificial internal crack is inspected by using the method of ultrasonic time of flight diffraction (TOFD), and the low resolution B-scan image with hyperbolic feature is processed in order to improve testing precision. According to the inspection manner of ultrasonic TOFD, a synthetic aperture focusing technique (SAFT) algorithmic model for B-scan image reconstruction is founded. By using the model, ultrasonic TOFD B-scan image can be enhanced. The time resolution of the B-scan image is improved by the pre-processing of searching for gray peak value, and the lateral resolution of the image is enhanced by suppression of the cutter by the following processing of SAFT. A B-scan image processing method that based on searching for gray peak value and SAFT is therefore proposed. A processing window is adopted in order to minimize the execution time of the algorithm, and proper width of the window is chosen. The result shows that the method can effectively enhance the target in the image, and the location of upper and lower crack tip in the sample can be measured rapidly and accurately accordingly.

Key words: Crack testing, Synthetic aperture focusing technique, Ultrasonic time of flight diffraction

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