STANDARD PART FOR MAGNETIC ACTING INSPECTION

Abstract

The invention relates to a ferromagnetic test piece (50) for magnetic particle inspection of a turbomachine shaft. The test piece has an internal bore and includes notches (53, 55) representing predefined surface defects on said test piece. It is characterized in that it further includes cutouts in which are formed openings representing predefined internal defects within said material. Figure to be published with the abbreviation: Figure 4A.

Description

Title of the invention: STANDARD PIECE FOR TESTING BY MAGNETOSCOPY Technical field of the invention

[0001] The present invention relates to a tubular standard part made of ferromagnetic material for the magnetic particle inspection of another tubular part made of ferromagnetic material of an aircraft gas turbine engine. A turbine engine shaft to be inspected is in particular concerned. Magnetic particle inspection (MT) is a non-destructive testing (NDT) technique for detecting defects on the surface of a part made of ferromagnetic material or inside this material. This technique consists of spraying a product containing colored particles or ferromagnetic particles coated with a fluorescent pigment onto the surface of the part to be inspected, then subjecting this part to a magnetic field while observing by endoscopy and under white light or ultraviolet light illumination the surface treated with the product.

[0002] With ferromagnetic particles, when the current lines of the magnetic field encounter a defect in the part, they are deflected, which creates a leakage field on the surface of the part attracting the ferromagnetic particles at the defect, these particles being observable under ultraviolet lighting due to the presence of the fluorescent pigment.

[0003] In the current technique, observation under ultraviolet illumination of the internal surface of a tubular part as defined above can be carried out by means of a rod engaged in the part and which carries an ultraviolet light source as well as an inclined mirror for returning images to a CCD camera. This technology has drawbacks. The rod is equipped with relatively complex and bulky equipment. The neon lamps which equip the light source do not allow the part to be illuminated uniformly. The emitted wavelength is difficult to control. The mirror returns small images. The rod is moved in translation inside the part at the same time as the latter is rotated around its axis, which results in a deformation of the images recorded by the camera.It is also difficult in this case to obtain sufficient coverage of the inspected surfaces and to guarantee that the entire surface to be explored has been checked.

[0004] FR-2946752 provided elements of a response by proposing a control device by magnetic particle inspection of a said tubular part having a longitudinal axis, this device comprising an elongated tool inserted inside the part and carrying ultraviolet lighting endoscopy means for lighting the interior tubular shape of the part and the observation of possible defects in the latter, the tool comprising a plurality of external markers regularly distributed over at least part of its length and defining regular steps of translational advance of the tool along the longitudinal axis of the part.

[0005] However, problems remain linked to incomplete verification of the structural characteristics of the part to be checked: the state at the heart of the material is insufficiently known.

[0006] The invention aims in particular to provide a simple, effective and economical solution to this.

[0007] A proposed solution is that the reference part concerned, which will have an axis (A) along which an internal bore will extend, comprises: - not only notches materializing predefined surface defects on said standard part, but also - cutouts in which lights are formed, materializing predefined internal defects within said material.

[0008] With such internal lights, we will be able, on the standard part: - to materialize internal defects, thus making them detectable, - by having previously calibrated them, thus predefined.

[0009] Note that the term “cut” is generic: said standard part having surfaces respectively: - exterior oriented towards the external environment of said standard part and - interior oriented towards the interior bore, it is a passage through the standard part which extends radially to the axis A) between said outer and inner surfaces respectively.

[0010] To combine on this single standard part the validation detections of the aforementioned magnetic particle inspection device, thus avoiding having to resort to several sub-devices, some of which are manual, others with an automatic operating cycle, it is also proposed that the aforementioned notches be formed in these external and internal surfaces.

[0011] Thus, we will associate materialization / detection of potential internal defects and materialization / detection of potential exterior and interior (apparent) surface defects.

[0012] To make the materialization / detection of potential internal defects (therefore in the ferromagnetic material) more reliable / secure, it is also proposed that the aforementioned lights be located at different radial distances from the aforementioned longitudinal axis.

[0013] And to ensure both the production and the magnetic particle identification of these lights which are respectively simple and efficient in all circumstances, it is also proposed that said lights comprise, within the ferromagnetic material genetic, elongated holes oriented for some parallel to said longitudinal axis, for others along sectors of circumference, around this axis.

[0014] To avoid having to drill the part to form these holes, one alternative proposes that the lights include grooves: - elongated for some parallel to said axis (A), for others along sectors of circumference, and - each opening, along its elongation, onto the outer surface or onto the inner surface.

[0015] The grooves can be made from the outer surface or the inner surface, radially to said axis (A), on thicknesses different from each other.

[0016] In groups, the grooves can be made parallel to each other, opening only onto the outer surface or only onto the inner surface.

[0017] A given rectangular cutout may be surrounded by four groups (one per side) of slots (in particular grooves), each with several more or less deep grooves (if they are grooves): two groups facing each other (on two opposite sides) opening out for one on the outer face and for the other on the inner surface.

[0018] Thus, the calibration reference will be of very good quality, without any notable complication in the manufacture of the part.

[0019] As already noted, the reference part concerned will favorably be a reference shaft intended to serve as a calibration reference for said magnetic particle inspection devices for gas turbomachine shafts, in particular low-pressure turbine and low-pressure compressor shafts which must be inspected: - after their manufacture, to detect possible metallurgical defects such as inclusions or machining cracks, and - during maintenance operations, to detect possible operational cracks.

[0020] In order for these shafts to be checked by magnetic particle inspection in their entirety, it is also proposed that said standard shaft has a tubular axial part provided axially with a journal, said aforementioned notches and slots being formed in the tubular axial part and in the journal, including in a said cutout thereof.

[0021] Furthermore, to facilitate these magnetic particle checks, it is proposed that the standard part be covered with a product containing ferromagnetic particles and a fluorescent pigment.

[0022] The invention may, if necessary, be even better understood and other details, characteristics and advantages of the invention may appear on reading the following description given by way of non-limiting example with reference to the appended drawings in which Brief description of the figures

[0023] [fig.l] and

[0024] [fig.2] are schematic views of a non-destructive testing bench by magnetic- toscopy and represent two stages of the process of controlling an operational tree,

[0025] [fig.3] is a partial schematic perspective view of the aforementioned “tool”,

[0026] [fig.4] illustrates, in part A, a perspective view of an embodiment of the standard part according to the invention, in part B, a detail at any one of the locations marked in figure 4A, in part C, also a detail at one of the locations marked in figure 4A, from another angle of view, and, in part D, again a detail at one of the locations marked in figure 4A, from another angle,

[0027] [fig.5] illustrates, in part A, a perspective view of an embodiment of the standard part according to the invention, in part B, a detail at the location shown in figure 5A, and, in part C, again the same detail as Fig. 5A, from another angle,

[0028] [fig.6] illustrates, in part A, a perspective view of an embodiment of the standard part according to the invention, and, in part B, a detail at the locations shown in figure 6A,

[0029] [fig.7] illustrates an alternative embodiment, in section, of one of the circled locations Fig. 4A, and

[0030] [fig.8] illustrates the same variant embodiment, according to another view. Detailed description of the invention

[0031] Reference is first made to Figures 1, 2 which show a device or bench 10 for non-destructive testing (NDT) by magnetic particle inspection of a tubular part which is, in the example shown, a shaft 12 of a gas turbomachine for an aircraft, and in particular a low-pressure turbine or low-pressure compressor shaft. The shaft 12 is elongated, with a longitudinal axis A. It is made of ferromagnetic material. The inner and outer cylindrical surfaces of the shaft 12 must be inspected by magnetic particle inspection after the manufacture of this shaft or during maintenance operations, to detect the presence of any defects in the ferromagnetic material of the shaft.This control is essentially carried out in two stages: a first stage in which a product containing ferromagnetic particles coated with a fluorescent pigment is sprayed onto the internal surface of the shaft, and a second stage in which the shaft is subjected to a magnetic field and a tool 14 carrying endoscopy means is engaged inside the shaft for visual inspection under ultraviolet lighting of its internal surface treated with the aforementioned product.

[0032] The control bench 10 comprises means 16 for supporting and rotating the shaft 12 around its axis A, a tool 14 for non-destructive testing by magnetic particle scanning of the aforementioned type, means 18 for supporting and guiding in translation this tool inside the shaft 12, and magnetic field generators 20.

[0033] The support means 16, which rest on the ground, make it possible to rotate the shaft 12 around its axis A. Means 18, such as rollers 26, for supporting the tool 14 are arranged towards the ends of the shaft 12 so that the tool can be engaged and guided in one of these ends, as can be seen in FIGS. 1 and 2. The magnetic field generators 20 are capable of applying a magnetic field to the shaft 12 in a longitudinal direction (arrows 28) and / or in a transverse direction (arrows 30). The tool 14 comprises endoscopy means housed inside a tubular cylindrical body on the outer surface of which are formed marks 32 defining regular steps of translational advance of the tool along the axis A. In the example shown, these marks 32 are formed by external annular marks or external annular grooves extending around the longitudinal axis of the tool (figure 1).

[0034] The means 18 for supporting the tool 14 are equipped with indexing means 34 cooperating with the markers 32 of the tool to control and determine the axial position of the tool in the shaft 12. The endoscopy means carried by the tool 14 comprise image transmission means 36 and ultraviolet light guiding means 38, which extend axially in the body of the tool. The image transmission means 36 protrude axially from the distal end of the body of the tool (figure 3) and comprise at this end at least one prism 40 for returning images to a series of lenses housed in the body of the tool. The images are for example captured by a camera located at the proximal end of the tool to then be viewed on a control screen.

[0035] The light guide means 38 are connected at the proximal end of the tool to an ultraviolet light source and protrude axially at their opposite end from the distal end of the body of the tool.

[0036] The endoscopy means may have a deflected distal view - the observation axis defined by the prism of the image transmission means 36 is oriented substantially perpendicular to the longitudinal axis of the tool, and the viewing axis defined by the distal end of the light guiding means 38 is substantially parallel to this viewing axis. The image transmission and light guiding means 36, 38 are further connected at their proximal ends to a control and data processing unit 42. The tool 14 is intended to be engaged in the shaft by one of its ends (figure 1) and to be blocked in a given axial position in the shaft using the indexing means 34. The tool is held fixedly by the support means 18 and the shaft 12 is rotated around its axis A by the support means 16, so that the lighting task of the endoscopy means of the tool scans an internal annular surface of the tool.The tool is then moved in translation by one step in . forward or backward in the shaft (arrow 42) and is then again immobilized by the indexing means 34 of the support means 18. The rotation of the shaft 12 causes the lighting task of the endoscopy means to scan a new internal annular surface of the shaft which at least partially covers the previously inspected annular surface. The tool 14 is thus advanced or moved back step by step inside the shaft and held fixedly after each of these movements and during the rotation of the shaft 12.

[0037] To make such Non-Destructive Testing by magnetic particle inspection reliable, regular verification of the machine parameters is necessary to guarantee the proper functioning of the test bench.

[0038] This serial verification is carried out in a known manner in several stages.

[0039] Firstly, using a first standard gauge (cylindrical ring which may have machining of 01 to 2mm underlying - that is to say internal to the material, for example at approximately 2mm from the surface and which simulate defects), a circular magnetization is carried out with an external inspection carried out visually by the inspector, as well as an internal inspection carried out using an endoscope or an endoscopic camera.

[0040] In a second step, using a second gauge block (elongated bar which may have underlying machining as above, which therefore simulates defects), a longitudinal magnetization is carried out with an external inspection carried out visually by the inspector, as well as an internal inspection carried out using an endoscope or an endoscopic camera.

[0041] In a third step, and less frequently, another check is carried out, with a situation of a standard shaft which has internal and external surface machining, which always simulate surface defects. The check carried out by the inspector is visual for the external surface and is carried out using an endoscopic camera for the internal surface of the shaft - along its central bore.

[0042] To best secure the checks of the control device or bench 10, it is proposed to use, instead of the shaft 12, the standard part 50, on which checks will be carried out periodically, in an automatic cycle, so as to ensure the correct calibration of the checks of the “real” shafts 12 from the series motors.

[0043] As illustrated in Figures 4 to 8, the standard part 50 is therefore tubular and made of ferromagnetic material. It is an equivalent of the shaft 12. The standard part 50 is therefore elongated along the longitudinal axis A, along which an internal bore 51 extends. On its outer surface 57, oriented towards the external environment, and inner surface 63, oriented towards the internal bore, it comprises notches, or grooves, 53, 55 materializing predefined surface defects; see in particular Figures 6A, 6B.

[0044] The standard part 50 further comprises cutouts 59 in which (around which) are formed slots 61 materializing predefined internal defects inside the material of the standard part. The slots 61 are located at different radial distances from the axis A, therefore at different radial depths in the material of the standard part 50, as can be seen in Figures 5B-5D. For detection efficiency and ease of production, these slots may each comprise an elongated hole oriented, for some, parallel to the axis A, for others along circumference sectors; see Figure 6. Thus, slots 61 forming crosses will then be formed around the cutouts 59 into which they will open.

[0045] In addition to an essentially tubular part 65, the axially longest, which has just been presented, the part 50 also comprises a so-called trunnion part 67, at a free end. On the operational shaft, this trunnion part 67 serves as an interface with the rotating parts to be mounted around this shaft.

[0046] Other surface notches 69 (see figures 6A, 6B) and slots 71 (see figures 5B, 5C) are formed in the journal 67. The slots 71, distributed at different radial depths, parallel to the axis A, are formed in a said cutout, here marked 73, and in one of the radial faces 75a, 75b of the journal, here that 75a oriented towards the essentially tubular part 65 of the standard shaft.

[0047] The slots 71 are each rectilinear and circumferentially oriented. The surface notches 69 are like those 53 (circumferential hollow lines a few hundredths of a mm deep and a few cm long). The surface notches 69 may be formed in the radially outer and inner circumferential surfaces 77a, 77b respectively of an axial rim of the journal 67. Figures 6A-6B show locations on the essentially tubular portion 65 and the journal 67 where surface notches may be present.

[0048] To facilitate identification by magnetic particle scanning, the standard part 50 will be favorably covered with a product containing ferromagnetic particles and a fluorescent pigment.

[0049] The alternative embodiment of Figures 7 and 8 is different from the previous embodiment of Figures 4B-4D in that the lights 61 now comprise grooves 650 - elongated for some parallel to said axis A, for others along sectors of circumference, and - each opening, along its elongation, onto the outer surface 57 or onto the inner surface 63.

[0050] The grooves may be presented in groups: two pairs of groups of grooves with, in each pair, two groups of grooves facing each other from one group to the other, on two opposite sides of a rectangular slot 61.

[0051] In each pair of groups facing each other, the grooves 650 open, along their elongations (such as L1 and L2 in Figure 8), onto the outer surface 57 for one of the groups and onto the inner surface 63 for the other group.

[0052] In groups, the grooves may be made parallel to each other, be rectilinear, and therefore only open onto the outer surface or only onto the inner surface.

[0053] In a group, the grooves 650 are successively and progressively deeper from the first to the last groove of the group.

[0054] Thus, the grooves 650 may be produced from the outer surface or the inner surface, radially to said axis A, on thicknesses different from each other.

[0055] In the version with elongated holes 65 (figures 4B-4D) it is the radial position (of digging) of the holes which varied successively and progressively from the first to the last hole of the group.

[0056]

Claims

Claims

1. Tubular standard part (50) made of ferromagnetic material for the magnetic particle inspection of a tubular part (12) made of ferromagnetic material of an aircraft gas turbine engine, the standard part having an axis (A) along which an internal bore (51) extends and comprising notches (53, 55, 69) materializing predefined surface defects on said standard part, characterized in that it further comprises cutouts (, 59, 73) in which are formed slots (61, 71) materializing predefined internal defects inside said material.

2. Standard part according to claim 1, having respectively external surfaces, oriented towards the external environment of said standard part, and internal surfaces, oriented towards the internal bore (51), the notches (53, 55, 69) being formed in the external and internal surfaces (57, 63; 77a, 77b).

3. Standard part according to one of the preceding claims, in which the lights (61, 71) are located at different radial distances from said axis (A).

4. Standard part according to one of the preceding claims in which, the part having respectively external surfaces oriented towards the external environment of said standard part and internal surfaces oriented towards the internal bore (51), the slots (61, 71) comprise grooves (650): - elongated for some parallel to said axis (A), for others along sectors of circumference, and - each opening, along its elongation, onto the external surface or onto the internal surface.

5. Standard part according to one of the preceding claims, in which the lights (61, 71) comprise elongated holes (65) oriented for some parallel to said axis (A), for others along sectors of circumference.

6. A standard part according to one of the preceding claims, in which the standard part (50) is a standard shaft.

7. A standard part according to claim 6, in which the standard shaft has a tubular axial part (65) provided axially with a journal (67), said notches (53, 55, 69) and slots (61, 71) being formed in the tubular axial part and in the journal, including

8. in a said cutout (71) thereof. A standard part according to one of the preceding claims, wherein the standard part (50) is covered with a product containing ferromagnetic particles and a fluorescent pigment.

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