超声TOFD检测方法在厚大焊缝的检测中具有较强的优势，特别是对裂纹类的缺陷，其检出效率高。为满足工程现场检测的需要，开发了基于USB接口的便携式超声TOFD检测系统，利用该系统对含有不同尺寸的人工底面开口窄槽的铝合金试块进行了D扫描检测。同时利用提出的自动算法提取了焊缝区域并将该区域的图像进行了转换，解决了D扫描图像在纵向方向上的显示与焊件厚度之间非线性的关系。结果表明，处理后的图像便于缺陷深度测量，检测人员可根据线性关系直接估算出缺陷的深度和高度，提高了检测效率。

Ultrasonic TOFD method has advantages on weld defects testing for thick workpiece, especially high-efficiency on crack defects detection. In this paper, a USB based pocket-type testing system that combines the software part with the scan equipment was designed. It was applied to test the aluminium alloy specimen which contained different depth of defects. Furthermore, the presented algorithm could be used to automatically recognize the weld zone and linearize the depth of image instead of the original testing image. The result showed that the processed image was more convenient for defect localization by the linearized algorithm of the depth, and the testing efficiency was increased.