METHOD AND DEVICE FOR COLD COMPRESSION OF AT LEAST ONE CELLUM OF A PART

Abstract

The invention relates to a method for cold compression of at least one cavity (12) of a part (10) comprising: - a step of inserting a compression device (18) inside at least one cavity (12), each cavity (12) having an open contour, at least a portion of the compression device (18) inserted inside a cavity (12) having a cross-section with an area (A1) greater than an area (A2) of a cross-section of said cavity (12), and - a step of removing the compression device (18) from inside at least one cavity (12). For short: Figure 3a

Description

Title of the invention: METHOD AND DEVICE FOR COLD COMPRESSION OF AT LEAST ONE CORE OF A PART

[0001] The present invention relates to a method for cold compressing at least one cell of a part. The invention finds a particularly advantageous, but not exclusive, application with a propulsion element of a turbomachine, such as a compressor disk, a turbine disk, or a fan disk of an aircraft turbomachine.

[0002] An aircraft turbomachine conventionally comprises, from upstream to downstream, with reference to the flow of gases in the turbomachine, a blower, one or more compressors, an annular combustion chamber, one or more turbines and a combustion gas exhaust nozzle.

[0003] A turbine disk comprises a plurality of open-contour cells in which blades are mounted. These cells have internal bearing surfaces ensuring radial retention of the blades. Similarly, a compressor disk or a blower disk comprises at least one cell in which blades are mounted. The cell comprises internal bearing surfaces ensuring radial retention of the blades.

[0004] The mechanical strength of the cells in these propulsion elements is critical for the durability of the turbomachine. To maximize their lifespan, it is known to compress the surface of the cells using a shot peening technique that involves bombarding the compressor disk or turbine disk with a high-pressure medium. However, this technique only compresses the surface of the cells to a shallow depth of approximately 100 micrometers.

[0005] Other so-called "deep" compression techniques are also known, such as the application of laser shocks, hammering, or roller grinding. However, this type of technology is difficult and expensive to implement.

[0006] The invention aims to effectively remedy these drawbacks by proposing a method for cold compression of at least one cell of a part comprising: - a step of inserting a compression device inside at least one cell, the cell having an open contour, at least a part of the compression device inserted inside a cell having a cross-section with an area greater than the area of ​​a cross-section of said cell, and - a step of removing the compression device from inside the at least an alveolus.

[0007] The invention thus makes it easy to achieve deep compression of the cell surfaces, allowing residual stresses to be applied at depths of several millimeters. The invention also improves the durability and homogeneity of the cell compression. The invention is also economical in that its implementation is rapid and based on an inexpensive tool.

[0008] According to one embodiment of the invention, the open contour of at least one alveolus is described by at least one segment.

[0009] According to another embodiment of the invention, the open contour of at least one alveolus is described by at least one continuous curve.

[0010] According to another embodiment of the invention, the open contour of at least one alveolus is described by at least one continuous curve and at least one segment.

[0011] According to one embodiment of the invention, the part of the compression device inserted inside a cell has in cross-section an excess thickness compared to the cross-section of said cell.

[0012] According to one embodiment of the invention, the extra thickness varies along a contour of the compression device.

[0013] According to one embodiment of the invention, the excess thickness varies along a longitudinal extension direction of the compression device.

[0014] According to one embodiment of the invention, the extra thickness is between 0.5% and 5% of a larger dimension of the cross-section of said cell.

[0015] According to one embodiment of the invention, the compression device comprises at least one mandrel intended to be inserted inside at least one cavity following a translational or helical movement.

[0016] According to one embodiment of the invention, the chuck comprises a narrowed portion and a flared portion.

[0017] According to one embodiment of the invention, the compression device further comprises at least one guide element interposed between the mandrel and the cavity.

[0018] According to one embodiment of the invention, said method comprises a step of filling, by at least one wedge, a cell adjacent to the at least one cell in which the compression device is inserted.

[0019] According to one embodiment of the invention, said process further comprises a finishing step.

[0020] According to one embodiment of the invention, the part is a propulsion element of a tur-bomachine.

[0021] The invention further relates to a cold compression device for less one open-contoured cell of a part comprising: - one or more mandrels, each intended to be inserted inside an open-contour cavity in the workpiece, - compression means associated with each chuck and - at least a part of the compression device intended to be inserted inside a cavity having a cross-section having an area greater than an area of ​​a cross-section of said cavity.

[0022] According to one embodiment of the invention, the compression means are capable of being actuated individually, simultaneously, or selectively.

[0023] According to one embodiment of the invention, the compression means can be controlled manually or automatically.

[0024] According to one embodiment of the invention, the compression means are of the pneumatic, electric or hydraulic type.

[0025] The present invention will be better understood and other features and advantages will become apparent upon reading the following detailed description, which includes embodiments given by way of illustration with reference to the accompanying figures, presented by way of non-limiting examples, which may serve to complete the understanding of the present invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which:

[0026] [Fig-1] Fig. 1 is a perspective view of a turbine disk with which is implemented the process of compressing cells according to the present invention;

[0027] [Fig.2] Fig.2 is a schematic side view representation of three alveoli of the turbine disc of the [Fig.l];

[0028] [Fig. 3a] Fig. 3a is a schematic representation of a step in the implementation of pressure of a cell of a turbine disc by means of a mandrel according to the present invention;

[0029] [Fig. 3b] Fig. 3b is a schematic representation of a step in the implementation of pressure of a cell of a turbine disc by means of a mandrel and a guide element according to the present invention.

[0030] It should be noted that, in the figures, structural and / or functional elements common to the different embodiments may have the same reference numerals. Thus, unless otherwise stated, such elements have identical structural, dimensional and material properties.

[0031] Figure 1 shows a turbine disc 10 with which the compression process according to the invention is implemented. The process can also be implemented with a compressor disc or a blower disc.

[0032] In the example shown, the turbine disk 10 has a portion 11 of the shape The cylindrical portion 11 has an axis XI corresponding to the axis of the turbine disk 10. The cylindrical portion 11 has a small thickness compared to its diameter. The turbine disk 10 has a plurality of cavities 12 on its outer periphery. The turbine disk 10 may have a central opening 13 for the passage of a shaft or, alternatively, mounting flanges with a ferrule (not shown).

[0033] More specifically, the turbine disk 10 has, along its circumference, an alternation of recesses 12 and teeth 15. A recess 12 is thus delimited by two consecutive teeth 15. An axis X2 of a recess 12 passing through the centers of the cross-sections of the recess 12 may have an orientation parallel or non-parallel to the axis XI of the turbine disk 10. As illustrated in [Fig. 2], each recess 12 has an open contour to receive a corresponding blade root. The open contour of a recess 12 may be described by at least one segment, or at least one continuous curve, or at least one continuous curve and at least one segment.

[0034] In this case, a cavity 12 has two bearing surfaces 16 facing each other, against which correspondingly shaped faces of the blade root are intended to bear. These bearing surfaces 16 ensure radial retention of the blade roots. The turbine disk 10 is made of a metallic material, such as, for example, a nickel-based alloy, steel, or any other material suitable for the application.

[0035] The method of compressing at least one cell 12 of the turbine disk 10 is described below with reference to Figures 3a and 3b.

[0036] This method includes a step of inserting a compression device 18 inside the cavity 12. At least a portion of the compression device 18 inserted inside the cavity 12 has a cross-section with an area A1 greater than an area A2 of the cross-section of the cavity 12 (see [Fig. 2]). The portion of the compression device 18 inserted inside the cavity 12 is therefore to be considered to the exclusion of any other portion of the compression device 18 located outside the cavity 12. The cross-section of the compression device 18 is considered along a plane perpendicular to an axis X3 of the compression device 18. The cross-section of the cavity 12 is considered along a plane perpendicular to an axis of the cavity 12.

[0037] Inserting the compression device 18 into the cavity 12 compresses the surface of the cavity 12 and thus plastically deforms it. Furthermore, the compression introduces residual stresses, particularly in two directions parallel to the surface of the cavity 12. Preferably, the residual stresses are observable to a depth of approximately 4 mm. The compression device 18 is then removed from inside the cavity 12. All the operations are preferably carried out cold.

[0038] The compression device 18 has a cross-sectional thickness 19 greater than that of a cross-sectional area of ​​the socket 12. This thickness 19 can vary along the contour of the compression device 18. The variation in the thickness 19 depends, in particular, on the thickness of the tooth 15 in a given area. For example, the thickness 19 is reduced in the flared portion 23 of the compression device 18 compared to a narrowed portion 22 of the compression device 18. Indeed, the flared portion 23 is designed to compress the surface of the socket 12 at the base of a tooth 15 with a small thickness. The thickness 19 is therefore reduced in this area to limit the applied compressive force and prevent deformation of the tooth 15.

[0039] The extra thickness 19 can also vary along a longitudinal extension direction of the compression device 18. In this case, this longitudinal extension direction runs along the X3 axis. Thus, on the end side of the compression device 18 intended to be inserted first into the cavity 12, the extra thickness 19 is reduced or zero to facilitate the insertion of the compression device 18 into the cavity 12. The extra thickness 19 then gradually increases until it reaches a maximum value that allows for a desired level of residual stress. The extra thickness 19 is, for example, between 0.5% and 5% of a larger dimension of the cross-section of said cavity.

[0040] In the embodiment of [Fig. 3a], the compression device 18 comprises at least one mandrel 21 inserted into a cavity 12 in a translational movement T. The translational movement T of the mandrel 21 is carried out in a direction parallel to or coinciding with the axis X2 of the cavity 12. Alternatively, the mandrel 21 can be inserted into a cavity 12 in a helical motion. This type of movement of the mandrel 21 is possible only for cavity geometries that allow rotation of the mandrel 21. The mandrel 21 can be made of a metallic material, for example, high-yield-strength steel, or a nickel-based alloy or carbide, or any other material suitable for the application. Only one mandrel 21 is shown for ease of understanding of the invention.

[0041] Of course, it is possible to use a compression device 18 comprising several mandrels 21, each intended to be inserted into a cavity 12. Compression means are associated with each mandrel 21. The compression means are capable of being actuated individually, simultaneously, or selectively. The compression means are controllable manually or automatically. The compression means may be of the type pneumatic, electric or hydraulic.

[0042] A mandrel 21 has a narrowed portion 22 and a flared portion 23. The flared portion 23 has a greater width in cross-section than the narrowed portion 22. The flared portion 23 is located on the side of one end of the mandrel 21.

[0043] The chuck 21 comprises a first lateral face 25 and a second lateral face 26, at least partially defining the narrowed portion 22 and the flared portion 23 of the tool. The first lateral face 25 comprises a first portion having a first direction of curvature and a second portion having a second direction of curvature opposite to the first direction of curvature. The second lateral face 26 comprises a first portion having a first direction of curvature and a second portion having a second direction of curvature opposite to the first direction of curvature. The portions of curvature having opposite directions of curvature are connected to each other by means of a line of inflection. The lateral faces 25 and 26 thus have an S-shape. The lateral faces 25 and 26 are symmetrical with respect to a median plane. The first lateral face 25 is intended to come into contact with a corresponding first bearing surface 16 of the socket 12.The second lateral face 26 is intended to come into contact with a corresponding second bearing surface 16 of the cavity 12. The first lateral face 25 and the second lateral face 26 are connected by an end face 27 intended to be positioned against the bottom of the cavity 12. The end face 27 may have a convex shape. Alternatively, the mandrel 21 may have a shape adapted to fir-tree-shaped cavities 12 having several bearing surfaces 16 provided in each of the lateral faces of the cavity 12.

[0044] In the embodiment of [Fig. 3b], the compression device 18 further comprises a guide element 30 having the shape of the cavity 12. This guide element 30 is interposed between the mandrel 21 and the cavity 12. In the case where the guide element 30 protrudes from the cavity 12, the guide element 30 may have a flared shape having a cross-section that decreases when moving from the outside of the cavity 12 towards the inside of the cavity 12.

[0045] The guide element 30 has a thin profile, specifically between 0.1 mm and 0.3 mm. This prevents damage to the surface of the cavity 12 and facilitates the sliding of the mandrel 21 within the cavity 12. According to this embodiment, the additional thickness 19 to be considered for the compression device 18 corresponds to the additional thickness of the "mandrel 21-guide element 30" assembly. In some embodiments, the mandrel 21 may have a shape complementary to the cavity 12, and the additional thickness 19 is then defined by the guide element 30.

[0046] In the event that the rigidity of the teeth 15 is insufficient to withstand the forces induced by the compression of the surfaces of the sockets 12 (risk of undesired deformation by the process), the process may include a filling step, by shims 31, with recesses 12 adjacent to the recess 12 into which the mandrel 21 is inserted to increase their stiffness. The shims 31 are thus arranged on either side of the recess 12 into which the compression device 18 is inserted. A shim 31 has a shape corresponding to that of a recess 12. The shims 31 are, for example, made of a metallic material.

[0047] In cases where compression causes deformation of the cavity 12, the process may also include a finishing step comprising a machining step and / or a deburring step and / or a shot peening step. The finishing step is specifically designed to remove any bulges that may appear at the edges or corners of a cavity 12.

[0048] The process is applicable to any part having at least one open contour cavity 12.

[0049] Of course, the different features, variants and / or embodiments of the present invention can be combined with each other in various ways insofar as they are not incompatible or mutually exclusive.

[0050] Furthermore, the invention is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms, and other variants that a person skilled in the art may consider within the scope of the present invention, and in particular all combinations of the different modes of operation described above, which may be taken separately or in combination.

Claims

Demands

1. A method for cold compression of at least one cavity (12) of a part (10), characterized in that said part (10) consists of a turbine disk comprising a cylindrical portion (11) having an axis (X1) corresponding to the axis of the turbine disk, and the open-contour cavity (12) comprising two bearing surfaces (12) opposite each other against which correspondingly shaped faces of a blade root are intended to bear, the cavity (12) comprising an axis (X2) passing through centers of cross-sections of the cavity (12), said method comprising: - a step of inserting a compression device (18) inside at least one cavity (12), at least a portion of the compression device (18) inserted inside a cavity (12) having a cross-section having an area (Al) greater than an area (A2) of a cross-section of said alveolus (12),the compression device (18) comprising at least one mandrel (21), the mandrel (21) being inserted inside at least one cavity (12) following a translational movement (T), the translational movement (T) being carried out in a direction parallel to or coinciding with the axis (X2) of the cavity (12) and - a step of withdrawing the compression device (18) from inside at least one cavity (12).

2. Method according to claim 1, characterized in that the part of the compression device (18) inserted inside a cavity (12) has in cross section an overthickness (19) relative to the cross section of said cavity (12).

3. Method according to claim 2, characterized in that the excess thickness (19) varies along a contour of the compression device (18).

4. Method according to claim 2 or 3, characterized in that the overthickness (19) varies along a longitudinal extension direction of the compression device (18).

5. A method according to any one of claims 2 to 4, characterized in that the extra thickness (19) is between 0.5% and 5% of a larger dimension of the cross-section of said cell (12).

6. Method according to claim 5, characterized in that the mandrel (21) has a narrowed portion (22) and a flared portion (23).

7. A method according to claim 5 or 6, characterized in that the device compression setting (18) further comprises at least one guide element (30) interposed between the mandrel (21) and the cavity (12).

8. A method according to any one of claims 1 to 7, characterized in that it comprises a step of filling, by at least one wedge (31), a cavity (12) adjacent to the at least one cavity (12) in which the compression device (18) is inserted.

9. A method according to any one of claims 1 to 8, characterized in that it further comprises a finishing step.

10. Device for implementing the method as defined according to any one of the preceding claims of cold compression of at least one open-contour cavity (12) of a part (10) characterized in that it comprises - one or more mandrels (21) each intended to be inserted inside an open-contour cavity (12) of the part (10), - a mandrel (21) having a narrowed portion (22) and a flared portion (23), the flared portion (23) having in cross-section a greater width than the narrowed portion (22), the flared portion (23) being located on the side of one end of the mandrel (21), the mandrel (21) having a first lateral face (25) and a second lateral face (26) delimiting at least in part the narrowed portion (22) and the flared portion (23) of the tool,the first lateral face (25) comprising a first portion having a first direction of curvature and a second portion having a second direction of curvature opposite to the first direction of curvature, the second lateral face (26) comprising a first portion having a first direction of curvature and a second portion having a second direction of curvature opposite to the first direction of curvature, the portions of curvature having opposite directions of curvature being connected to each other by means of a line of inflection, the lateral faces (25,26) having an S-shape, - compression means associated with each mandrel (21), and - at least a part of the compression device (18) intended to be inserted inside a cavity (12) having a cross-section having an area (A1) greater than an area (A2) of a cross-section of said cavity (12).

11. Device according to claim 10, characterized in that the compression means are capable of being actuated individually, simultaneously, or selectively.

12. Device according to claim 10 or 11, characterized in that the Compression methods can be controlled manually or automatically.

13. Device according to any one of claims 10 to 12, characterized in that the compression means are of the pneumatic, electrical or hydraulic type.

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