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1 问题的提出 在T、K、Y管节点焊缝超声波探伤中,由于支管的壁厚较小,一次波声程较短,加之焊接缺陷多出现在根部与支管侧熔合区部位,故此通常都要求在支管侧进行探伤,面以主管侧探伤作为辅助手段。为了确保缺陷的检出率,探伤时必须保证波束垂直于焊缝的延伸方向。为此,在焊缝的不同位置,探头与支管的圆周线必然构成一定角度θc。这时探头中心线与波束所构成的平面切取支管,从而得到一同心椭圆形的管壁截面。这导致一次波的声程将随θc的变化面发生改变。如图1所示,在平板情况下一次波声程为AB,在曲面情况下为AC。那么,定义声程修正系数K为 K=AC/AB (1) 式中 AC——有曲率情况下的一次波声程
PROBLEM TO BE SOLVED BY THE INVENTION In the ultrasonic flaw detection of T, K and Y pipe joints, since the wall thickness of the branch pipe is small and the acoustic wave length of the primary wave is short and the welding defects mostly appear in the root and branch side fusional zone, It is required to carry out the flaw detection on the branch pipe side and to inspect the flank pipe as an auxiliary means. In order to ensure the detection rate of defects, flaw detection must ensure that the beam perpendicular to the direction of extension of the weld. To this end, in different locations of the weld, the probe and the branch pipe circumference must constitute a certain angle θc. At this time, the centerline of the probe and the plane formed by the beam cut off the branch pipe to obtain a concentric elliptical pipe wall cross-section. This results in a change in the acoustic path of the primary wave with the change in θc. Shown in Figure 1, in the case of flat wave once the acoustic path AB, in the case of surface AC. Then, the definition of sound path correction coefficient K is K = AC / AB (1) Where AC - curvature of the case with the first wave path