基于几何方法的焊缝倾斜裂纹TOFD定量检测

The Quantitative TOFD Detection of Inclined Crack in Bult Weld Based on Geometric Method

针对合金钢对接焊缝中倾斜裂纹定量困难的问题,提出了TOFD（超声衍射时差法）定量检测倾斜裂纹的方法。基于焊缝纵断面方向上两次B扫查间隔、两次B扫查过程中声程最短时编码器移动距离差和倾斜裂纹三者所构成的三角形,利用三者之间几何关系实现裂纹倾斜角度与长度定量。模拟结果表明：对长度5,10,60mm,倾斜角度范围为10°~90°的裂纹进行定量验证,角度定量误差小于1°;长度定量相对误差小于5%。试验针对对接焊缝试块中长度60mm,倾斜角度范围为30°~60°的倾斜裂纹应用此方法进行定量验证,可得裂纹角度定量误差最大值为0.29°;长度定量误差最大值为0.94mm。

To solve the problem that the inclined crack in butt weld of alloy steel is difficult to be quantified,a method of time-of-flight-diffraction（TOFD）for inclined crack is proposed.There is a triangle composed by the interval of two B-scans along with the direction of vertical section of weld profile,the difference of moving distance of encoder where the acoustic distance is minimum and the inclined crack.Taking advantage of this geometric relationship,the length and tilting angle of inclined crack can be detected quantitatively.In the simulation,artificial inclined crack with lengths of 5,10,60 mm and tilting angles from 10°to 90°were made.The simulation results showed that the quantitative error of angle was less than 1°,and the relative error of length was less than 5%.In the experiment,attention was paid to quantitative detection of inclined crack whose length was 60 mm and tilting angle was from 30°to 60°.The result presented the maximum of absolute error of angle and length was 0.29°and0.94 mm,respectively.