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。
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.
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2007年第10期103-107,共5页
Journal of Mechanical Engineering
基金
国家高技术研究发展计划资助项目(863计划
2002AA305402)。
关键词
超声渡越时差法
合成孔径聚焦
裂纹检测
Ultrasonic time of flight diffraction Synthetic aperture focusing technique Crack testing
