Method for mounting an abradable element comprising a cellular structure in an annular groove of a turbomachine member

Abstract

Method (100) for mounting an annular abradable element (16) in an annular groove of a member (21) of a turbomachine (1), the annular abradable element (16) extending along an axis (A3) and comprising a cellular structure, the groove opening out at the radially inner periphery of said member (21), the method (100) comprising the steps of stressing the abradable element (16) in such a way as to deform it in a plane perpendicular to the axis (A3) of the non-deformed annular abradable element (16), with the aid of a device (20); positioning the deformed abradable element (16) axially opposite the annular groove, inside the member (21); freeing the abradable element (16) in such a way that it inserts itself into the groove and recovers its annular shape there.

Description

technical field

[0001] The present invention relates to a method of mounting an abradable element comprising a honeycomb structure in an annular groove of a turbomachine component. Previous technique

[0002] There figure 1 Figure 1 illustrates a prior art turbomachine. This comprises, from upstream to downstream in the direction of gas flow, a fan 2, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber 5, a high-pressure turbine 6, a low-pressure turbine 7, and a gas exhaust nozzle 8. The high-pressure compressor 4 and the low-pressure compressor 3 are respectively connected to a high-pressure turbine 6 and a low-pressure turbine 7 by a respective shaft 9 extending along the direction of a longitudinal axis X of the turbomachine 1.

[0003] Each compressor stage 3, 4 is formed by an upstream rotating wheel comprising an annular row of moving blades 10 inside an external annular casing 11 and a downstream stator comprising an annular row of fixed blades 12 relative to the external annular casing 11. Similarly, each turbine stage 6, 7 is formed by an upstream distributor comprising an annular row of fixed blades 12 relative to the external annular casing 11 and a downstream rotating wheel comprising an annular row of moving blades 10 inside the external annular casing 11.

[0004] Each annular row of moving blades 10 or fixed blades 12 includes an inner platform 13 and an outer platform 14 delimiting an annular gas flow channel through the compressor 3, 4 or the turbine 6, 7.

[0005] As depicted in figure 2In the case of a turbine 7, the radially external face of the external platform 14 of each moving blade 10 includes scrapers 15 cooperating in a sealing manner with an annular abradable element 16, mounted in an external ring 17. In particular, the external ring 17 has a groove opening radially inwards, in which the abradable element 16 is mounted. The external ring 17 is carried by the external annular housing 11.

[0006] As depicted in figure 3 In the case of a compressor 4, the radially inner face of the inner platform 13 of each annular row of fixed blades 12 comprises an annular groove receiving an annular abradable element 16. The abradable element 16 cooperates in sealing with the blades 15 of the turbomachine shaft 9 1.

[0007] The abradable element 16 generally comprises a honeycomb structure, into which the swabs 15 penetrate due to differential thermal expansion and mechanical deformation during operation. Following prolonged use, the abradable element 16 wears down and then needs to be replaced.

[0008] To this end, after removing the worn abradable element 16 from the annular groove of one of the outer rings 17 or from the inner platform 13 of one of the annular rows of fixed blades 12, a new abradable element 16 having an annular shape is manually deformed to be inserted into the annular groove. The abradable element 16 is then manually deformed again to extend fully annularly inside the annular groove. An example is described in US patent application 2016 / 169043.

[0009] However, such manual deformation of the abradable element is random and has the disadvantage of deteriorating the alveolar structure of the abradable element 16, in particular due to the low resistance of the alveolar structure in a tangential direction of the abradable element, so that the abradable element 16 mounted in the annular groove does not ultimately conform to the required specifications. Summary

[0010] The purpose of this disclosure is to address this drawback in a simple, reliable and inexpensive way.

[0011] To this end, the invention relates to a method for mounting an annular abradable element in an annular groove of a component of a turbomachine, the annular abradable element extending along an axis and comprising a honeycomb structure, the groove opening radially on the inner periphery of said component, the method comprising the steps of: The abradable element is constrained so as to deform it in a plane perpendicular to the axis of the undeformed annular abradable element. Using a device, the deformed abradable element is axially positioned opposite the annular groove inside the organ. The abradable element is then released so that it inserts into the groove and regains its annular shape. In this constrained and deformed position, the abradable element has a deformed omega-shaped portion and a rounded, undeformed portion. This shape reduces the dimensions of the abradable element to allow its insertion into the organ containing the groove, while avoiding bending zones with excessively small radii of curvature.In particular, when constrained and deformed, the abradable element can have a maximum radius of curvature smaller than the radius of the organ's groove, allowing for its insertion without forcing. Furthermore, this bean-like shape avoids an excessively small radius of curvature that could crush some alveoli and thus damage the abradable element. Moreover, this bean-like shape is also compatible with deformation of the annular element in a plane.

[0012] The terms axial, radial and circumferential are defined with respect to the axis of the annular groove, which coincides with the axis of the turbomachine.

[0013] This process, by deforming the abradable element in a plane perpendicular to the axis of the undeformed annular abradable element, allows the application of a normal force—that is, in the direction of the cell extension—at any point on the abradable element. This prevents the degradation of the abradable element by crushing its cells. Furthermore, the process is relatively easy and quick to implement, as well as reproducible.

[0014] The abradable element can be annularly closed around the axis. In particular, the abradable element can be axisymmetric about the axis. Furthermore, the abradable element can be cylindrical in revolution about the axis. A cross-section of the abradable element in a perpendicular plane of cut can have the shape of a closed ring.

[0015] The device may include a first pressing member and a second pressing member disposed on either side of a support base, each pressing member being connected to the support base by a connecting rod having a first end mounted pivoting relative to the support base and a second end supporting the corresponding pressing member, the support base and the pressing members each having a curved lateral support surface, said lateral support surface of the support base bearing on an external surface of the abradable element, said lateral support surfaces of the pressing members bearing on an internal surface of the abradable element, the deformation of the abradable element being obtained by pivoting the connecting rods relative to the support base and moving the connecting rods relative to each other.

[0016] The shapes of the curved support surfaces allow control of the radii of curvature of the abradable element thus deformed.

[0017] The deformation of the abradable element can consist of wrapping the abradable element around the curved bearing surface of the support base, by moving the pressure members.

[0018] Curved bearing surfaces can be cylindrical or in the shape of a portion of a cylinder.

[0019] The pressure elements are, for example, formed by rollers. The bearing surface of the base can be a portion of a cylinder extending over an angular range greater than 120°, for example. The bearing surface of the base can be semi-cylindrical.

[0020] The device can be symmetrical with respect to a plane of symmetry passing through a center of the support base, the pressure members and connecting rods being located on either side of said plane of symmetry, the step aimed at constraining the abradable element being carried out by symmetrical displacement of the pressure members and connecting rods with respect to said plane of symmetry.

[0021] The symmetrical movement of the connecting rods prevents any rotation of the support base around the axis of the abradable element.

[0022] The forces to be applied to the pressing elements to deform the abradable element around the base can then be equal.

[0023] Before deformation of the abradable element, the pressure members may be located on one side of a plane perpendicular to the plane of symmetry and passing through the center of the support base and in which, after deformation of the abradable element, the pressure members are located, at least in part, on the other side of said plane perpendicular to the plane of symmetry.

[0024] Each pressure member can be mounted pivoting relative to the second end of the corresponding connecting rod, each pressure member rolling on the internal surface of the abradable element when the connecting rods move relative to the support base.

[0025] This avoids friction between the pressure elements and the inner face of the abradable element, thus preventing any degradation of the abradable element.

[0026] A gripping handle can be mounted on each connecting rod, the said connecting rods being moved manually.

[0027] The device may include means for gearing the connecting rods together, said gearing means ensuring a symmetrical movement of said connecting rods with respect to a plane of symmetry passing through the support base.

[0028] The first end of each connecting rod may have a toothed part that meshes with the toothed part of the opposite connecting rod, the movement of one of the connecting rods causing the movement of the other connecting rod.

[0029] The device may include stop means suitable for limiting the movement of the pressure members and connecting rods during the deformation of the abradable element.

[0030] The stop means prevent over-deformation of the abradable element, thus preventing its degradation and crushing of the cells.

[0031] Such a stop can be formed, for each connecting rod, by a part projecting from the base, for example a rod, the connecting rod being able to bear against said projecting part.

[0032] Such a stop can be formed, for each connecting rod, by a tab extending laterally from the corresponding connecting rod, the tabs of each connecting rod being adapted to come into contact with each other when the connecting rods move relative to each other.

[0033] The device may include locking means suitable for immobilizing each pressing member in position relative to the support base.

[0034] The locking means thus make it possible to keep the abradable element in a deformed position after movement of the pressing members, in order to facilitate the implementation of the process, in particular when this process is implemented manually.

[0035] The locking means may include at least one ratchet wheel. This ratchet wheel may comprise a toothed wheel fixed to the base or to one of the connecting rods, and a pawl, a portion of which engages with the teeth of the toothed wheel. The pawl is pivotally mounted on one of the connecting rods or to the base. The engagement of the pawl with the toothed wheel allows the connecting rod to rotate relative to the support base in one direction of rotation but prevents its rotation relative to the support base in the opposite direction. The permitted direction of rotation corresponds to the movement of the connecting rods from the undeformed position of the abradable element to the deformed position of the abradable element.

[0036] The pawl may be subjected to the action of an elastic return element tending to apply the meshing part of the pawl to the teeth of the toothed wheel. The elastic return element may be a torsion spring.

[0037] The ratchet wheel can be disengaged to prevent the pawl from engaging with the toothed wheel, particularly when an operator wants to move the connecting rods from the deformed position of the abradable element to its undeformed position. The pawl can include an actuating rod for manual disengagement of the ratchet wheel by an operator. In other words, an operator can use the actuating rod to move the pawl away from the teeth of the ratchet wheel, against the return force exerted by the elastic return element, thereby disengaging the ratchet wheel.

[0038] The teeth of the ratchet wheel can be shaped to allow the ratchet wheel to disengage only after the abradable element has been pre-stressed. This ensures the safe return of the abradable element to its undeformed position.

[0039] One or both connecting rods can be equipped with a ratchet wheel. Equipping each connecting rod with a ratchet wheel has the advantage of requiring an operator to have one hand on each handle during disengagement and return of the abradable element to the undeformed position, thus minimizing the risk of accidents and injuries.

[0040] The invention also relates to a device for implementing the process as described above. Brief description of the drawings

[0041] Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which: Figure 1is a half axial cross-sectional view of a prior art turbomachine; Figure 2 is an axial cross-sectional view of part of a prior art turbine; Figure 3 is an axial cross-sectional view of part of a prior art compressor; Figure 4 is a front view of the device enabling the implementation of the process, in the undeformed position of the abradable element; Figure 5 is a side view of the device of the figure 4 ; Figure 6 is an exploded, perspective view of the device figures 4 And 5 ; Figure 7 is seen illustrating the meshing of the connecting rods of the device of the figures 4 to 6 ; Figure 8 includes the figures 8a, 8b and 8c illustrating the different successive positions of the ratchet and the toothed wheel of the locking means of the device figures 4 to 6 ; Figure 9is a functional diagram of the method for mounting an abradable element in an annular groove of a turbomachine, according to the method according to the invention; Figure 10 is a front view illustrating the device of figures 4 to 6 positioned on the undeformed abradable element; Figure 11 is a front view illustrating a step in the process during which the abradable element is deformed; Figure 12 is a front view illustrating the abradable element in a constrained and deformed position due to the device of figures 4 to 6 ; Figure 13 is a view illustrating a step in the process in which the deformed abradable element is positioned opposite the annular groove of the turbomachine component; Figure 14 is a front view illustrating a step in the process during which the abradable element is released to extend inside the annular groove. Description of the implementation methods

[0042] THE figures 4 to 8represent a device 20 adapted for a method of mounting an abradable element 16 in an annular groove of a component 21 of a turbomachine 1.

[0043] As depicted in figure 4 The device 20 comprises a first pressing member 22 and a second pressing member 22. The device 20 also comprises a support base 23. The first and second pressing members 22 are arranged on either side of the support base 23.

[0044] The support base 23 and the pressure members 22 each have a curved lateral support surface 24. The pressure members 22 are each formed by a roller. The support surface 24 of the support base 23 is a portion of a cylinder extending over approximately 180°. The base 23 also includes a lateral surface opposite the support surface 24. This opposite lateral surface is flat.

[0045] Each pressure member 22 is connected to the support base 23 by a connecting rod 25 having a first end mounted pivotally about a first axis A1 relative to the support base 23 and a second end supporting the corresponding pressure member 22. For this purpose, the first end of each connecting rod 25 is mounted on a first rod 26, formed for example by a screw, fixed to the support base 23 and extending along the corresponding first axis A1.

[0046] The device 20 is symmetrical with respect to a plane of symmetry P1 passing through a center of the support base 23. For this purpose, the pressure members 22 and the connecting rods 25 are located on either side of the plane of symmetry P1.

[0047] Remarkably, each first axis A1, around which the corresponding connecting rod 25 pivots, is parallel to the plane of symmetry P1. Thus, the pressure members 22 can be moved at least in part between a first side c1 of a plane perpendicular P2 to the plane of symmetry P1 and passing through the center of the support base 23, and a second side c2 of the plane perpendicular P2 to the plane of symmetry P1.

[0048] Each pressure member 22 is also pivotally mounted relative to the second end of the corresponding connecting rod 25. In particular, each pressure member 22 is pivotally mounted about a second axis A2 of revolution. To this end, each pressure member 22 is mounted on a second rod 27 fixed to the corresponding connecting rod 25 and extending along the second axis A2 of revolution of the corresponding pressure member 22.

[0049] As represented at Figures 5 And 6The device 20 further includes a gripping handle 28 mounted on each connecting rod 25. Each handle 28 is rigidly mounted on its corresponding connecting rod 25. Here, each handle 28 is screwed onto its corresponding connecting rod 25. Thus, the connecting rods 25 can be manually pivoted relative to the support base 23 using the handles 28.

[0050] The device 20 also includes means for gearing the connecting rods 25 together. The gearing means are particularly visible at figures 6 And 7To achieve this, the first end of each connecting rod 25 may have a toothed portion 29 that meshes with the toothed portion 29 of the opposite connecting rod 25. The teeth are arranged at the first end of each connecting rod 25 along an arc of a circle around the first axis A1 of the corresponding connecting rod 25. In other words, the first end of each connecting rod 25 forms a half-gear wheel. This ensures symmetrical and simultaneous pivoting of the connecting rods 25 with respect to the plane of symmetry P1 of the device 20.

[0051] The device 20 further includes stop means suitable for limiting the movement of the pressure members 22 and the connecting rods 25. Here, the stops are each formed by a leg 30 extending laterally from one of the connecting rods 25. Thus, the legs 30 of the connecting rods 25 come into contact with each other when the connecting rods 25 are pivoted from the first side c1 to the second side c2 of the plane perpendicular P2 to the plane of symmetry P1 of the device 20.

[0052] Device 20 also includes visible locking means in figure 6 The locking means are suitable for immobilizing each pressing member 22 in position relative to the support base 23.

[0053] The locking means here comprise two ratchet wheels 31. Each ratchet wheel 31 includes a toothed wheel 32 having teeth 33. Each toothed wheel 32 is here fixed to the support base 23, notably by means of one of the first rods 26. Each toothed wheel 32 is thus centered on one of the first axes A1. The toothed wheels 32 of the ratchet wheels 31 are also fixed together by a plate 34, screwed into each of the toothed wheels 32.

[0054] Each ratchet wheel 31 also includes a pawl 35, part of which engages the teeth 33 of one of the toothed wheels 32. Each pawl 35 is pivotally mounted on one of the connecting rods 25. As shown in figures 8a, 8b and 8cThe teeth 33 of each toothed wheel 32 are uniform but asymmetrical, each tooth 33 having a moderate slope 40 on one edge and a steep slope 41 on the other edge. Thus, the meshing of the pawl 35 with the teeth 33 of the corresponding toothed wheel 32 is such that it allows the connecting rod 25 carrying the pawl 35 to pivot in one direction and prevents the connecting rod 25 from pivoting in the opposite direction of rotation. The permitted direction of rotation corresponds to the movement of the connecting rods 25 from the first side c1 of the plane perpendicular P1 to the plane of symmetry P2 to the second side c2 of the plane perpendicular P2 to the plane of symmetry P1 of the device 20.

[0055] There figure 8a represents the pawl 35 at the bottom of the tooth or at the steep slope 41 of one of the teeth 33. Thus, a rotation of the connecting rod 25 carrying the pawl 35 in the opposite direction (counterclockwise on the figure 8a) is prevented by the steep slope 41 of tooth 33. Conversely, a rotation in the permitted direction (clockwise on the figure 8a ) is made possible by the sliding of the pawl 35 on the moderate slope 40 of the adjacent tooth 33. The figure 8b shows the slippage of pawl 35 on the moderate slope 40 of tooth 33. The figure 8c represents the pawl 35 again at the bottom of the tooth and spaced one tooth 33 apart from the position of the pawl in figure 8a . Similarly, a rotation of the pawl 25 in the opposite direction is prevented by the steep slope 41 of the tooth 33, whereas rotation in the permitted direction is allowed by the sliding of the pawl 35 on the moderate slope 40 of the adjacent tooth 33.

[0056] Each pawl 35 is also subjected to the action of an elastic return element tending to apply the meshing portion of the pawl 35 to the teeth 33 of the corresponding toothed wheel 32. Each elastic return element is a torsion spring 36. One end of each torsion spring 36 is fixed to one of the connecting rods 25. A second end of each torsion spring bears against, or is fixed to, the corresponding pawl 25.

[0057] Each torsion spring 36 can be compressed to prevent the pawl 35 from engaging with the corresponding toothed wheel 32. The corresponding ratchet wheel 31 is then disengaged to allow the respective connecting rod 25 to pivot in the opposite direction of rotation to that permitted by the ratchet wheel 31. Each pawl 35 has an actuating rod 37 for manually disengaging the ratchet wheel 31.

[0058] THE figures 9 to 14represent a method of mounting 100 an abradable element 16 in an annular groove of a turbomachine component 21 by means of a device 20 in accordance with figures 4 to 8 The turbomachine 1 component 21 can be an external ring 17 or an internal platform 13 belonging to a turbine 6, 7 or a compressor 3, 4, as known from the prior art. The annular groove opens radially internally at the periphery of the turbomachine 1 component 21.

[0059] The abradable element 16 is annular in shape and extends along a third axis A3. The abradable element 16 also includes a honeycomb structure and is deformable.

[0060] There figure 9 represents a functional diagram of the assembly process 100.

[0061] The assembly process 100 includes a first step 110 represented in Figure 10The first step 110 consists of positioning the device 20 so that the lateral bearing surface 24 of the base 23 bears on an external surface of the abradable element 16 and the lateral bearing surfaces 24 of the pressure members 22 bear on an internal surface of the abradable element 16. Remarkably, the pressure members 22 are located on the first side c1 of the plane perpendicular P2 to the plane of symmetry P1 of the device 20.

[0062] As represented in figure 11The method 100 includes a second step 120 of constraining the abradable element 16 so as to deform it, at least partially, in a plane perpendicular to the third axis A3 of the undeformed abradable element 16, using the device 20. To do this, the connecting rods 25 are pivoted relative to each other so as to move the pressing members 22 towards the second side c2 of the plane perpendicular P2 to the plane of symmetry P1. The connecting rods 25 are thus moved away from each other relative to the plane of symmetry P1 in a first phase of the movement. The connecting rods 25 are then moved closer together relative to the plane of symmetry P1 in a second phase of the movement. The connecting rods 25 are moved manually here, using the handles 28.Before deformation of the abradable element 16, the pressure members 22 are located on the first side c1 of the plane perpendicular P2 to the plane of symmetry P1, and after deformation of the abradable element 16, the pressure members 22 are located here on the second side c2 of the plane perpendicular P2 to the plane of symmetry P1 of the device 20.

[0063] Thus, the abradable element 16 is deformed so as to surround the curved bearing surface 24 of the bearing base 23.

[0064] Such deformation in a plane perpendicular to the third axis A3 of the undeformed abradable element 16 makes it possible to limit, or even avoid, the crushing of the cells of the abradable element 16. Furthermore, the curved shapes of the bearing surfaces 24 allow control of the radii of curvature of the abradable element 16 thus deformed. Also, the permitted rotation of the pressure members 22 around their respective second axis of revolution A2 allows the pressure members 22 to roll on the inner face of the abradable element 16 during the movement of the connecting rods 25 relative to the support base 23. This prevents friction of the pressure members 22 on the inner face of the abradable element 16, thereby avoiding any degradation of the abradable element 16.

[0065] The abradable element 16 is deformed into a constrained and deformed position in which the abradable element 16 has a bean-like shape, as illustrated in the figure 12or a shape. In other words, the abradable element 16 is partially deformed to have an omega (ω) shape. The deformed abradable element therefore also includes a rounded, undeformed portion 38. This shape reduces the dimensions of the abradable element 16, allowing it to be inserted into the turbomachine component 21, which includes the annular groove. Furthermore, this shape avoids areas where the abradable element 16 would bend due to excessively small radii of curvature.

[0066] The constrained and deformed position of the abradable element 16 corresponds here to a position of the device 20 in which the tabs 30 of the connecting rods 25 are bearing against each other. This ensures the conformity of the deformation of the abradable element 16. The process 100 is therefore easy to implement and reproducible. Furthermore, the stop means limit the movement of the pressure members 22 and the connecting rods 25 during the deformation of the abradable element 16. The stop means thus prevent over-deformation of the abradable element 16, thereby avoiding its degradation and crushing of the cells.

[0067] On the other hand, the locking means of the device 20 allow here a rotation of the connecting rods 25 from the undeformed position of the abradable element 16 towards the deformed position of the abradable element 16. A rotation in the opposite direction is blocked by the ratchet wheels 31.

[0068] Thus, after the pressure members 22 have moved, the constrained and deformed position of the abradable element 16 is maintained by the locking means. This facilitates handling the abradable element in the constrained and deformed position, particularly when process 100 is carried out manually.

[0069] As represented in figure 13The method 100 includes a third step 130 consisting of axially positioning the abradable element 16 in a constrained and deformed position opposite the annular groove, inside the turbomachine component 21. The deformed abradable element 16 can be positioned so that the third axis A3 of the undeformed abradable element 16 coincides with an axis of revolution of the annular groove of the turbomachine component 21. Furthermore, the abradable element 16 can be partially disposed within the annular groove. In particular, the undeformed rounded portion 38 of the deformed abradable element 16 can be engaged inside the annular groove of the turbomachine component 21.

[0070] Process 100 then includes a fourth step 140 represented in figure 14 . The fourth step 140 consists of releasing the abradable element 16 so that it inserts itself into the groove and regains its annular shape.

[0071] To do this, each ratchet wheel 31 of the device 20 is disengaged by the operator using the corresponding rod 37, so that the operator can move the connecting rods 25 from the deformed position of the abradable element 16 to the undeformed position of the abradable element 16.

[0072] In other words, an operator can move the pawl 35 away from the teeth 33 of the toothed wheel 32 of each ratchet wheel 31 using the actuating rod 37, against the return force exerted by the elastic return member, so as to disengage the ratchet wheel 31. Then, the operator can move the connecting rods 25 towards the undeformed position of the abradable element 16 by keeping the pawl 35 of each ratchet wheel 31 away from the teeth 33 of the toothed wheel 32.

[0073] The invention is not limited to the examples described above and is susceptible to numerous variations.

[0074] According to an unrepresented variant, the support base 23 can be fixed to a support such as a table.

[0075] According to another variant not shown, the abradable element 16 can be deformed asymmetrically. For example, the connecting rods 25 can exhibit asymmetrical displacement relative to the support base 23.

[0076] According to another variant not shown, device 20 may include a motor which drives the rotation of the connecting rods.

[0077] According to another variant not shown, the device 20 may include a support base 23 and rollers 22 having a different profile and / or size.

[0078] According to another variant not shown, the device 20 may include a system for reducing the effort required to move the pressure members 22 and the connecting rods 25 relative to the support base 23. Such a system may, for example, be a gear reducer.

Claims

1. Method (100) for mounting an annular abradable element (16) in an annular groove of a member (21) of a turbomachine (1), the annular abradable element (16) extending along an axis (A3) and comprising a cellular structure, the groove emerging at the radially inner periphery of said member (21), the method (100) including the steps of: - constraining the abradable element (16) so as to deform it in a plane perpendicular to the axis (A3) of the non-deformed annular abradable element (16), by means of a device (20), - axially positioning the deformed abradable element (16) facing the annular groove, inside the member (21), - releasing the abradable element (16) so that it is inserted in the groove and regains its annular shape therein, and wherein, in a constrained and deformed position of the abradable element (16), it has a deformed omega-shaped section and a rounded, non-deformed section.

2. Method according to claim 1, wherein the device (20) comprises a first pressing member (22) and a second pressing member (22) both disposed on either side of a support base (23), each pressing member (22) being connected to the support base (23) by a linkage (25) including a first end mounted so as to pivot with respect to the support base (23) and a second end supporting the corresponding pressing member (22), the pressing members (22) and the support base (23) each including a curved lateral support surface (24), said lateral support surface (24) of the support base (23) coming into abutment on an external surface of the abradable element (16), said lateral support surfaces (24) of the pressing members (22) coming into abutment on an internal surface of the abradable element (16), the deformation of the abradable element (16) being obtained by pivoting the linkages (25) with respect to the support base (23) and moving the linkages (25) with respect to each other.

3. Method according to claim 2, wherein the curved support surfaces (24) are cylindrical in shape or in the form of a portion of a cylinder.

4. Method according to claim 2 or 3, wherein the device (20) is symmetrical with respect to a symmetry plane (P1) passing through a center of the support base (23), the pressing members (22) and the linkages (25) being located on either side of said symmetry plane (P1), the step aimed at constraining the abradable element (16) being implemented by symmetrical movement of the pressing members (22) and linkages (25) with respect to said symmetry plane.

5. Method according to claim 4, wherein, before the abradable element (16) is deformed, the pressing members (22) are located on one side (c1) of a plane (P2) perpendicular to the symmetry plane (P1) and passing through the center of the support base (23) and wherein, after the abradable element (16) is deformed, the pressing members (22) are located, at least partly, on the other side (c2) of said plane (P2) perpendicular to the symmetry plane (P1).

6. Method according to any one of claims 2 to 5, each pressing member (22) is mounted pivotably with respect to the second end of the corresponding linkage (25), each pressing member (22) rolling on the internal surface of the abradable element (16) when the linkages (25) are moved with respect to the support base (23).

7. Method according to any one of claims 2 to 6, wherein the device (20) includes means for meshing the linkages with each other, said meshing means ensuring symmetrical movement of said linkages (25) with respect to a symmetry plane passing through the support base (23).

8. Method according to either one of claims 2 or 7, wherein the device (20) includes stop means able to limit the movement of the pressing members (22) and linkages (25) during the deformation of the abradable element (16).

9. Method according to any one of claims 2 to 8, wherein the device (20) comprises locking means able to immobilize each pressing member (22) in position with respect to the support base (23).

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