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1 前言T、K、Y管节点焊缝的超声波探伤存在诸多技术困难和特征,对缺陷的定量技术也须有许多独到之处。主要表现在:(1)缺陷的定量与缺陷的判定以及定位互相渗透。首先要判定反射波是否由缺陷所造成,尔后判定缺陷是一个点、一条线还是一个面,按缺陷的类型选择相应的定量方法。在缺陷的判定、定位及定量之间,没有明显的界限,彼此互相验证。(2)在T、K、Y管节点焊缝的超声波探伤中,一般不要求测高;但如有特殊要求,还须测量缺陷的高度。测高的方法主要有:端部回波峰值法、回波高度比较法和有效声束宽度法等。工程上最常用的还是20dB降落法。(3)缺陷指示长度的测量与平板对接焊缝测长相比,主要差异表现在:T、K、Y管节点焊缝呈椭圆曲线形状,检测时探头要在垂直于焊缝延伸方向进行移动、摆动扫查,不能以缺陷两端点所对应的探头入射点连线作为缺陷指示长度,而应以对应焊缝上的曲线长度作为指示长度,如图1所示。(4)T、K、Y管节点焊缝超声波探伤缺陷定量工作
1 Introduction T, K, Y pipe joints ultrasonic flaw detection there are many technical difficulties and characteristics of the quantitative techniques of defects must also have many unique features. Mainly in: (1) Defects in the quantitative and defect determination and positioning of mutual penetration. First of all to determine whether the reflected wave caused by defects, and then determine the defect is a point, a line or a surface, according to the type of defect to select the appropriate quantitative method. Defects in the determination, positioning and quantitative, there is no clear boundary between each other to verify. (2) In T, K, Y pipe joints ultrasonic flaw detection, the general does not require elevation; but if there are special requirements, but also to measure the height of defects. The main method of altimetry are: peak echo method, echo height comparison method and effective beam width method. The most commonly used engineering or 20dB landing method. (3) The measurement of defect indication length Compared with the length measurement of flat butt weld, the main differences are as follows: The weld of T, K, Y joints is elliptic curve shape, the probe should be moved perpendicular to the weld extension direction, Swing scanning can not be the two ends of the defect corresponding to the probe incident point connection as a defect indication length, but should be the corresponding length of the curve on the weld as an indication of length, as shown in Figure 1. (4) T, K, Y pipe joints quantitative ultrasonic flaw detection work