SU1748052A1 - Test specimen for ultrasonic inspection - Google Patents

Abstract

The invention relates to the control in the manufacture and operation of thick-walled welded structures such as vessel pressure and can be used in non-destructive testing of welded joints. The aim of the invention is to increase the reliability of the detection of individual underlying internal defects when inspecting welds. The goal is achieved due to the fact that the defects are located in the weld and are formed into groups located at a distance of not less than Zmax {and}, where U is the characteristic size of the group of defects in the plan, and the distance between the defects in the group is selected from the relation: d (2.5 ... 5) VF / L, where; F is equivalent to the area of the largest defect in the group. 1 tab., 4 Il. (L

Description

The invention relates to the field of control in the manufacture and operation of thick-walled welded structures such as pressure vessels and can be used in research organizations and production associations engaged in the manufacture of welded structures, development and use of non-destructive control methods.

In the design and manufacture of welded structures of a responsible purpose, an urgent task is to ensure high reliability of the detection of internal defects, since it is they that may appear as initiators of destruction.

It is known that the detection of single defects by the methods of ultrasonic testing (UT) is not higher than 70 - 80%. Wherein

there are no data on the distinguishability and visibility of individual defects forming clusters inside the welds.

However, it is precisely such non-destructive testing data that is used as source information for the purpose of performing the strength calculations. It is assumed that if the distance d between the banks of two adjacent defects with dimensions of 2a and 2c meets the condition d max {2a, 2c}, then the two defects are considered as one. Hence, the urgency of the task is obvious, consisting in assessing the reliability of detecting individual internal defects forming clusters or chains, with different distances between defects in a group. There are no test samples that allow such studies.

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A disadvantage of the known samples is that the internal defects are uniquely classified as single ones, and their sizes and location coordinates are known in advance to the operator of the ultrasonic inspection. It is this that creates a certain psychological attitude of the flaw detector in the confident detection of defects. In addition, defects are created by drilling or milling, and are bulk type defects. The most dangerous in welds are plane defects of the crack-like type.

The closest to the technical essence of the invention is a sample made about the form of a plate, on the surface of which under the deposited layer are placed single defects, the dimensions of which vary randomly, and the coordinates of the location of the defects are also subject to random patterns.

The disadvantage of the known sample is that the distance between two adjacent defects exceeds the characteristic size, which determines their identification as single. This does not allow us to reveal the regularities of the influence of the size of defects and the distance between their banks on the formation of the reflected signal and the distinctiveness of individual defects forming a certain cluster.

The purpose of the invention is to increase the reliability of the detection of individual adjacent internal defects when monitoring welds.

The goal is achieved by the fact that in the test sample for ultrasonic testing, defects are located in the weld and are formed into groups located at a distance of not less than Zmax, where U is the characteristic size of the group of defects in the plan, and the distance between the defects in group selected from the ratio

d (2.5 ... 5) vfT,

l

where F is equivalent to the area of the largest defect in the group.

Defect sizes using the F parameter in the test sample should be assigned taking into account the stochastic regularities of their size distribution in real welds.

It is known that with a probability of P 0.95 there may be defects in the welds of the housings of power plants

size 2a 18 mm, respectively F 240 mm2 The condition for changing the parameter d in each group of defects follows from geometrically -

relations. D value 2.5VZT

P

corresponds to a size x equal to half the size of the defect, i.e. the state when in the strength test calculations one should always consider two or more defects as a single one with the generalized size L 2a + X + 2a. D value

15

P

fits the occasion when x Over

and defects in a group must be classified as single.

Figure 1 shows the geometrical parameters of the group of defects; figure 2 - the appearance of the test sample; Fig. 3 shows a section in the plane of location of defects; figure 4 - section a - a in figure 2.

The test sample consists of two plates 1,

interconnected by a weld 2, Before welding two plates along a V-shaped groove, lining 3 is placed on its side surface, which, after finishing with weld metal,

form groups of planar defects. The technology of creating planar defects corresponds to a known sample.

Example. Plates 1 (FIG. 2) with a size of 500x500 mm and a thickness of 100 mm were made of steel 15X2HMFA. The shape of the cutting edge corresponds to the standard cutting used at the ATOMMASH software. Inside the seam, 3 groups of defects of 2a 9 mm in size were placed (3 pieces per group).

Geometric parameters of clusters of defects are presented in the table.

The technical and economic advantages of the invention are associated with an increase in the quality of welded structures by providing reliable discernability of defects and their revealing ™.

Claims (1)

Claims An ultraviolet test test sample, made in the form of a plate with artificial planar defects, characterized in that, in order to increase the reliability of identifying certain underlying internal defects during control of welds, the defects are located in the weld and are formed in groups located at a distance of not less than Zmax {1 |}, where U is the characteristic size of the group of defects in the plan, and the distance d between the defects in the group is chosen from the relation: d (2.5 ... 5.0) VF / tG, where F is equivalent to the area of the largest defect in the group. figure 1 / Editor M. Bandura Compiled by S. Meerovsky Tehred M.MorgentalKorrektor I. Muska fig 2 Aa fig.z Fy