基于超声TOFD法的焊接缺陷横向定位检测技术

Measurement method of weld defect transverse location based on ultrasonic TOFD technology

针对焊缝余高存在时,超声衍射时差法(time of flight diffraction,TOFD)B扫描可达性受限这一问题,提出了双椭圆法及纵横波复合法两种缺陷横向位置无损检测方法。根据探头和缺陷位置的几何关系,建立了缺陷定位测量的数学模型,利用确定的缺陷定位算法,分别对人工缺陷和焊接缺陷进行了定位检测。结果表明,双椭圆法在缺陷定位测量精度和操作实施过程上要优于纵横波复合法;采用双椭圆法,人工缺陷的埋藏深度及横向位置的平均测量误差分别为0.5和0.3 mm;焊接缺陷的埋藏深度及横向位置的平均测量误差分别为0.6和0.4 mm。所提方法克服了由于焊缝余高的存在,传统超声TOFD法B扫描不可达的问题,并为缺陷在焊缝中的横向位置检测提供解决办法。

Ultrasonic TOFD(time of flight diffraction)B-scan cannot be carried out because of the weld reinforcements.Aims at the problem,transverse position measurement methods for weld defects are proposed,including double ellipse based method and longitudinal-shear wave composite method.According to the geometric relationship between probe and defect position,two mathematical models of defect localization are established.Using the algorithm,the position of the artificial defects and actual defects are measured.The analysis and comparison results show that the double ellipse method is better than the longitudinal-shear wave composite method in terms of accuracy and implementation.Using double ellipse based method,the average errors of buried depth and transverse position of artificial defects are 0.5 and 0.3 mm respectively,and the average errors of buried depth and horizontal position of weld defects are 0.6 and 0.4 mm respectively.The proposed method effectively overcomes the disadvantage of limited accessibility of traditional ultrasonic TOFD B-scan because of the weld reinforcements,and provides a solution for the detection of the transverse position of the defect in the weld.