WO1998019155A1

WO1998019155A1 - Method for producing a test element for the qualifying of personnel, processes and equipment in non-destructive testing, as well as test element

Info

Publication number: WO1998019155A1
Application number: PCT/SE1997/001806
Authority: WO
Inventors: Sven Stenarson
Original assignee: UDDCOMB ENGINEERING AB
Current assignee: UDDCOMB ENGINEERING AB
Priority date: 1996-10-30
Filing date: 1997-10-29
Publication date: 1998-05-07
Anticipated expiration: 1999-04-30
Also published as: SE507590C2; SE9603954D0; SE9603954L

Abstract

A method for producing a test element (1) for use in non-destructive testing comprises the steps of making a hole (6) in a frame (2), of producing from a piece of metal a body (7) which is somewhat oversized but which corresponds to the shape of the hole (6), and of heating the frame (2) and/or chilling the body (7), whereupon the body (7) is inserted into the hole (6) in order to be, after temperature equalisation, fixedly and tightly joined to the frame (2), the body (7) comprising at least one detectable defect (3, 4). A test element (1), which is produced according to the method, has a frame (2) with a body (7) inserted therein. The body (7) is tightly fixed with a shrink fit in a hole (6) in the frame (2) and comprises a detectable defect (3, 4).

Description

METHOD FOR PRODUCING A TEST ELEMENT FOR THE

QUALIFYING OF PERSONNEL, PROCESSES AND EQUIPMENT IN

NON-DESTRUCTIVE TESTING, AS WELL AS TEST ELEMENT

The present invention relates to a method for producing a test element for the qualifying of personnel, processes and equipment in non-destructive testing of metal objects, the test element comprising a frame, which is made of metal and in which there is at least one defect, which for said qualifying is to be detected and/or sized. In addition, the invention relates to a test element produced with the aid of this method.

In connection with nuclear power in particular, it is very important that the personnel, the procedures, and the equipment used in testing components in reactor systems meet the requirements established by the supervisory authority. In order to ensure that this is the case, the personnel concerned and/or the procedures applied and/or the equipment used undergo special qualifying routines. There are various types of non-destructive testing, mostly testing with the aid of ultrasound, since ultrasound makes it possible to detect both surface-breaking and inclusion defects. It is considered important to car- ry out the qualifying on test elements which simulate reality and on defects which have been found to occur in manufacturing or during operations.

Prior art test elements have consisted either of defective components, which have been taken from plants in operation, or of test elements manufactured for this purpose, in which various defects have been created. One such defect can typically be a surface crack, which can be achieved in a metal frame with the aid of special spark machining. Another such defect can consist of an inclusion in a steel frame, which inclusion has been achieved by means of special manufacturing methods when manufacturing the frame. Hitherto, there has been no known method for producing test elements, which comprise a real fatigue crack which has not been applied to the test element with the aid of ordinary welding, diffusion bonding (DB) or hot isostatic pressing (HIP) . In the light of the above, the object of the present invention is to provide a method for producing a test element of the type mentioned by way of introduction, which test element can comprise a plurality of different types of defects, which, moreover, can be placed in different locations in the test element.

With respect to the method, the object is achieved by at least one rotationally symmetrical hole being made in the frame in the place where the defect is to be located; by a body, which is somewhat oversized but cor- responds to the shape of the hole and contains a known defect, being made from a piece of metal; and by the frame being heated and/or the body being chilled, whereupon the body is inserted into the hole in order to be, after temperature equalisation, fixedly and tightly join- ed to the frame, said at least one defect, which exists in the frame, consisting of the known defect in the body.

Since the known defect is located in a separate body, which has first been introduced into a frame by shrinking, it becomes possible to choose the defects which are to exist in the test element among a plurality of possible defects which can exist in different starting materials .

Specifically, in this way, it also becomes possible to provide test elements with fatigue cracks, something which is achieved by the body being cut from a metal sheet in which, in the location from which the body is cut, a defect in the form of a fatigue crack has been made by cyclic bending of the metal sheet.

Moreover, surface cracks, which are traditionally made by welding directly on the frame, can be achieved according to the invention by the body being cut from a metal sheet in which, in the location from which the body is cut, a defect in the form of a surface crack has been made by welding up a cut in the metal sheet.

In addition, the placing of a defect in the form of an inclusion is facilitated considerably with the aid of the method according to the invention, if the body is cut from a metal sheet in which there is a defect in the form of an inclusion in the location from which the body is cut. In this case, unlike in prior methods, the inclusion can be placed in the desired location in the frame. Suitably, the detecting and/or sizing is carried out with the aid of ultrasound, X-ray, or eddy currents, which constitute the most common examination solutions in this context.

Preferably, the hole is made circular-cylindrical, which makes working the surfaces of the hole and of the body very easy, or cone-shaped, which facilitates the insertion of the body into the frame even at small cone angles .

If the frame is made of steel, it should not be heated to more than 500°C at the time of the shrinking, because otherwise there is a considerably increased risk of oxidation which can leave revealing traces in, for example, ultrasound examinations.

It will be appreciated that the body is suitably made from a like material to that of frame, since this, inter alia, facilitates the relative dimensioning of the hole and the body.

It will also be appreciated that the body joined to the frame can suitably be ground or milled down to flush with the surface of the frame in order not to leave any visible traces which reveal the location of the defect. In addition, it may be covered with a weld.

The test element produced in accordance with the method according to the invention is characterised in that the frame has at least one rotationally symmetrical hole with finished walls, and that a body, which is made of metal, is tightly fixed to the hole with a shrink fit, and that the body comprises a known defect, which constitutes said at least one defect in the frame.

As was mentioned above, unlike prior art test elements, such a test element can comprise a plurality of different defects, which, moreover, can be placed in different locations in the frame. Possible defects are, specifically, fatigue cracks, surface cracks, and inclusions .

It can be seen from the above that the hole is suit- ably circular-cylindrical or, if desired, cone-shaped and that the frame and the body are suitably made of like materials .

Embodiments of a test element according to the invention will be described in more detail below with refe- rence to the accompanying drawing, in which

Fig. 1 is a cross-sectional view and shows a part of a test element consisting of a sturdy frame with a body inserted therein; and

Fig. 2 is a cross-sectional view and shows a part of a test element, consisting of a relatively thin-walled frame and a body inserted therein.

The test elements 1, which are illustrated in Figs 1 and 2, are tubular and correspond in size and shape and ^j choice of material to pipes of the type which exist in nuclear power plants. The test elements 1 have a frame 2, which has an exterior and an interior surface 2 ' . At the location of the sections, the exterior and interior surfaces 2' are broken open by a through hole 6, which in the embodiments shown is circular-cylindrical and has a diameter d. Since the frames 2 in Figs 1 and 2 have different wall thickness t, it will be appreciated that the interior walls 6' of the holes 6 have different heights. However, otherwise they can be said to be identical.

In each of the two holes 6 sits a body 7, which has a circular-cylindrical circumferential surface 7', which abuts tightly and fixedly against the wall 6' of its respective hole 6. The bodies 7 are made of the same kind of material as the frames 2 and have been inserted into their respective frames 2 and have been applied thereto with a shrink fit.

In order for the bodies themselves 7 not to be detectable in an ultrasound examination of the test elements 1, it is important to pay attention to the following when effecting the shrinking: the circumferential surfaces 7' of the bodies 7 and the walls 6' of the holes

6 must be given a finishing cut before the shrinking, so that there will be no revealing cracks between the circumferential surfaces 7' and the walls 6'. Obviously, the bodies 7 must have a slightly larger diameter than the diameter d of the holes. Suitable dimensioning can be found in various tables and to some extent depends on the material. Finally, it should be noted that the frame 2, if heated to enable the insertion of the body 7, must not be heated excessively, because in that case oxidation will occur, which in for example an ultrasound examination will reveal the location of the body 7 in the frame 2. Obviously, at the time of the shrinking, it is also possible additionally or exclusively to chill the body 7 substantially prior to its insertion into the frame 2.

In the Figures, a height dimension h is indicated, which illustrates that the bodies 7 at the outset suit- ably have a height which exceeds the wall thickness t of the frames 2. In this way, it becomes possible, after the insertion of the bodies, to grind or mill down the bodies

7 to exactly flush with the surfaces 2 ' of the frames 2 and thus make the bodies 7 completely invisible. The bodies 7 in the Figures comprise defects 3, 4,

5, which are placed in different locations in the bodies. The defect 3 is completely contained in the test element 1, while defects 4 and 5 are surface-breaking and are located on the inside and the outside respectively of the frame 2. The defects can of course be of different types, where particularly one of these types is to be emphasised. Traditionally, the supply of test elements 1, which comprise fatigue cracks of the type which can occur after a certain period of operation of a plant, has been extremely limited. The reason for this is that prior art methods for producing test elements have not permitted the artificial application of fatigue cracks in a manner acceptable for qualifying purposes. This situation is changed by the creation of the method according to the invention, since it is now possible to make a fatigue crack in a metal sheet, which is not part of the frame

2, by means of cyclic bending back and forth of the metal sheet and by subsequently cutting a body 7 from this metal sheet at the location of the fatigue crack, which body is then inserted into a frame 2 by shrinking. The skilled person will appreciate that the method according to the invention is usable for producing test elements 1, which comprise several different types of defects, and that the defects mentioned herein only represent a preferred selection. The skilled person will also appreciate that a test element 1 according to the invention must not necessarily comprise a through hole 6 of the kind shown in the drawing, but that the hole 6 can also be a blind hole. In addition, the skilled person will appreciate that it can be a major advantage for the defect not to be surrounded by weld metal or other

"foreign" materials, such as in the above-mentioned DB or HIP techniques.

Claims

1. A method for producing a test element (1) for the qualifying of personnel, processes and equipment in nondestructive testing of metal objects, which test element

(1) comprises a frame (2), which is made of metal and in which there is at least one defect (3, 4, 5), which for said qualifying is to be detected and/or sized, c h a r a c t e r i s e d by the steps of making at least one rotationally symmetrical hole (6) in the frame (2) in the place where the defect is to be located; making a body, which is somewhat oversized but which corresponds to the shape of the hole (6) and which contains a known defect (3, 4, 5), from a piece of metal; and heating the frame (2) and/or chilling the body (7), whereupon the body (7) is inserted into the hole (6) in order to be, after temperature equalisation, fixedly and tightly joined to the frame (2), said at least one defect (3, 4, 5), which exists in the frame (2), consisting of the known defect (3, 4, 5) in the body (7) .

2. A method according to claim 1, c h a r a c t e r i s e d by effecting the detecting and/or the sizing with the aid of ultrasound, X-ray, or eddy currents.

3. A method according claim 1 or 2, c h a r a c t e r i s e d by making the hole (6) circular-cylindrical or cone-shaped.

4. A method according to any one of claims 1-3, c h a r a c t e r i s e d by cutting the body (7) from a metal sheet in which, in the location from which the body (7) is cut, a defect (3, 4, 5) in the form of a fatigue crack has been made by cyclic bending.

5. A method according to any one of claims 1-3, c h a r a c t e r i s e d by cutting the body (7) from a metal sheet in which, in the location from which the body (7) is cut, a defect (3, 4, 5) in the form of a surface crack has been made by welding up a cut.

6. A method according to any one of claims 1-3, c h a r a c t e r i s e d by cutting the body (7) from a metal sheet in which, in the location from which the body is cut, there is a defect (3, 4, 5) in the form of an inclusion.

7. A method according to any one of claims 1-6, c h a r a c t e r i s e d by heating the frame (2) , if made of steel, to a maximum of 500°C.

8. A method according to any one of claims 1-7, c h a r a c t e r i s e d by making the body (7) of a like material to that of the frame (2).

9. A method according to any one of claims 1-8, c h a r a c t e r i s e d by grinding or milling down the body (7) which is joined to the frame (2), to flush with the surface (2') of the frame (2).

10. A test element produced with the aid of the method according to claim 1, which test element (1) is intended for the qualifying of personnel, processes and equipment in non-destructive testing of metal objects and comprises a frame (2), which is made of metal and in which there is at least one defect (3, 4, 5), which for said qualifying is to be detected and/or sized, c h a r a c t e r i s e d in that the frame (2) has at least one rotationally symmetrical hole (6) with finished walls (β¹), that a body (7), which is made of metal, is tightly fixed to the hole (6) with a shrink fit, and that the body (7) comprises a known defect (3, 4, 5), which constitutes said at least one defect (3, 4, 5) in the frame (2) .

11. A test element according to claim 10, c h a r a c t e r i s e d in that the hole (6) is circular-cylindrical .

12. A test element according to claim 10, c a r a c t e r i s e d in that the hole (6) is cone-shaped.

13. A test element according to any one of claims 10-12, c h a r a c t e r i s e d in that the defect (3, 4, 5) is a fatigue crack.

14. A test element according to any one of claims 10-12, c h a r a c t e r i s e d in that the defect (3, 4, 5) is a surface crack.

15. A test element according to any one of claims 10-12, c h a r a c t e r i s e d in that the defect (3, 4, 5) is an inclusion.

16. A test element according to any one of claims 10-15, c h a r a c t e r i s e d in that the frame (2) and the body (7) are made of like materials.