基于合成孔径聚焦的超声TOFD检测技术及图像增强

为了精确定位开口裂纹的端部在铝合金厚板对接焊缝中的位置,对其超声衍射时差法(TOFD,time off flight diffraction)的 B 扫描图像进行了处理.为了提高图像的横向分辨率,引入了合成孔径聚焦技术(SAFT, synthetic aperture focusing technique).根据缺陷端部和换能器之间的几何关系,建立了图像SAFT处理的数学模型,实现了B扫描图像的SAFT重建.为了提高图像的纵向分辨率,先将原始图像进行了线性化处理,从而提出了一种新的超声TOFD法B扫描图像处理技术L-SAFT(linearization-SAFT).结果表明,该技术有效地提高了图像的分辨率.利用该技术能快速、准确地捕捉裂纹端部在试件中的横向和深度位置,实现缺陷的精确定位与定量.

Ultrasonic TOFD technique and image enhancemetn based on synthetin aperture fousing techinque

An ultrasonic TOFD(time of flight diffraction)B-scan image was processed in order to accurately locate crack tip in heavy aluminum butt weld.SAFT(synthetic aperture focusing technique)was introduced for improving lateral resolution of the image.According to the geometric relation between the probes and crack tip,an algorithmic model for SAFT processing was founded and SAFT reconstruted image was obtained.Linearization was proposed in order to enhance time resolution of the image before SAFT processing,and a novel technique named as L-SAFT (linearization-SAFT)was developed for ultrasonic TOFD B-scan image reconstruction.The results show that the technique can enhance resolution of the image effectively.Both lateral and vertical location of the crack tip in the specimen can be measured rapidly and accurately with this techinque,which contribute to precise locating and sizing of defect.