METHOD FOR MANUFACTURING AN AERODYNAMIC PANEL FOR AN AIRCRAFT PROPULSION ASSEMBLY

Abstract

A method for manufacturing an aerodynamic panel (32) for an aircraft propulsion assembly (10), the method comprising the following steps: a) applying at least one reinforcing plate (38, 42, 44) to a first face (34a) of a wall (34), b) joining the reinforcing plate (38, 42, 44) and the wall (34, 36) by friction stir welding, c) making through holes (50) through the wall (34) and the reinforcing plate (38, 42, 44), these holes (50) being formed through the weld bead (40), and d) mounting screws (52, 54, 56) in the holes (50), these screws (52, 54, 56) having countersunk heads (58) which have a thickness (H) greater than the thickness (E1) of the wall (34) and less than the thickness (E3) of the weld bead (40). Figure for the abbreviation: Figure 2

Description

Title of the invention: METHOD FOR MANUFACTURED AN AERODYNAMIC PANEL FOR AN AIRCRAFT PROPULSION ASSEMBLY Technical field of the invention

[0001] The present invention relates to a method of manufacturing an aerodynamic panel for an aircraft propulsion assembly, as well as an aerodynamic panel obtained by this method. Technical background

[0002] A propulsion unit comprises a turbomachine surrounded by a nacelle. The propulsion unit includes aerodynamic panels, which are panels designed, during operation, to be swept by one or more gas flows running along the propulsion unit. These panels may be nacelle cowlings designed to be swept by a gas flow external to the propulsion unit, or turbomachine casings designed to be swept by a secondary flow, for example.

[0003] An aerodynamic panel comprises an aerodynamic face adapted to be swept by the gas flow. This panel is fixed to the nacelle or turbomachine by screws that pass through the panel. Additional elements can be fixed to such a panel by screws.

[0004] The panel preferably has the thinnest possible thickness to limit its mass. However, this thickness must not be too thin at the screw points to withstand the stresses in the areas where the panel or components are fixed.

[0005] To circumvent this problem, it is known to use a thick panel and to machine it so as to leave excess thickness only in the fixing areas having holes for the fixing screws.

[0006] Another solution could be to attach a reinforcing plate to the wall. The reinforcing plate would be attached to the face of the panel opposite its aerodynamic face, and this reinforcing plate would include holes aligned with the holes in the wall, for the passage of the fixing screws.

[0007] The screws are countersunk head screws, that is, screws whose heads have a generally frustoconical shape and are designed to be engaged in flared portions of the holes located on the aerodynamic side of the wall. The larger the diameter of the screws, the larger the axial dimension or thickness of their countersunk heads. In current technology, it is not possible to use screws whose countersunk heads have a thickness or axial dimension greater than 2 / 3 of the panel thickness because the resulting assembly would not be optimal, since the panel would not would not be properly tightened by the screws on the reinforcement plate.

[0008] The present invention offers a simple, effective and economical solution to this problem. Summary of the invention

[0009] The present invention relates to a method for manufacturing an aerodynamic panel for an aircraft propulsion assembly, the method comprising the following steps:

[0010] a) applying at least one reinforcing plate to a first face of a wall, the reinforcing plate covering part of this first face and the wall having a second face, opposite to the first face, which is a face suitable for being swept by a gas flow when the panel is mounted in a propulsion assembly,

[0011] b) to join the reinforcing plate and the wall by friction stir welding using a tool comprising a welding head which is moved on the second face so as to create a weld bead which extends in thickness from the second face over the entire thickness of the wall and over at least part of the thickness of the reinforcing plate,

[0012] c) making through holes through the wall and the reinforcing plate, these holes being formed through the weld bead, and

[0013] d) mounting screws in the holes, these screws having countersunk heads which are located on the side of said second face and aligned with this face, these countersunk heads having a thickness or axial dimension less than said thickness of the weld bead.

[0014] A first advantage of the invention is that the thickness of the countersunk heads, and therefore the diameter of the screws, is not limited by the wall thickness. This means that thinner walls than in the prior art can be used in the context of the present invention, which is also advantageous in terms of mass and cost. The weld bead thickness is determined, on the one hand, based on the wall thickness and, on the other hand, based on the thickness or axial dimension of the countersunk screw heads. The weld bead thickness is greater than the wall thickness so that the weld bead extends into the reinforcing plate and secures it to the wall. The weld bead thickness is also greater than the thickness or axial dimension of the countersunk screw heads so that they are fully embedded within the weld bead.Finally, the thickness or axial dimension of the countersunk screw heads is greater than the wall thickness to ensure optimal support of the wall and the reinforcement plate.

[0015] Advantageously, the milled heads have a thickness or axial dimension greater than 2 / 3 of the thickness of the weld bead.

[0016] According to the invention, welding is carried out by friction stir welding (or FSW, which is

[0017]

[0018]

[0019]

[0020]

[0021]

[0022] (the acronym for Friction Stir Welding). This type of welding is advantageous because it does not require filler material. Furthermore, this type of weld does not produce a raised weld bead. On the contrary, the weld bead produced is relatively flat and generally has a free outer surface that is aligned with the face of the wall along which the welding tool head is moved. The wall face can, however, undergo a sanding and / or finishing operation to improve its surface finish. The double fixing of the wall and the reinforcement plate, via the weld bead and screws, improves the transmission of forces and therefore the lifespan of the panel. The method according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another: • the weld bead is made in a single pass in step b); • the process includes, after step d), a step e) of fixing an element on the reinforcement plate, on the side opposite said wall, this element having holes through which said screws pass, which receive nuts which are screwed onto the screws and which bear against the element; • the element is a fitting or a splint; • the process includes, between steps b) and c), a step i) of sanding a free external surface of the weld bead; • the panel has a thickness, preferably constant, between 1 and 3mm, and preferably between 1.5 and 2mm; • the weld codon has a width between 5 and 15mm; • The weld codon has a thickness between 1.5 and 4 mm, and preferably between 1.5 and 3mm; • the milled heads have a thickness or axial dimension greater than 2 / 3 (two-thirds) of said thickness of the weld bead; • the wall and the reinforcing plate are made of metallic materials, and are for example made of the same metallic alloy; — the reinforcing plate has a thickness greater than that of the wall; alternatively, its thickness could be the same or less; — the reinforcing plate has a thickness, preferably constant, between 2 and 4mm. The present invention also relates to an aerodynamic panel for an aircraft propulsion system, this panel being obtained by the process described above and comprising: - a wall comprising a first face and a second face opposite to the first this second face being capable of being swept by a gas flow when the panel is mounted in a propulsion assembly,

[0023] - a reinforcing plate which covers part of this first face and which is so bonded to the wall by a weld bead, this weld bead having a free external surface which is aligned with said second face, this weld bead having holes passing through the wall and the reinforcing plate, and

[0024] - screws mounted in the holes and having countersunk heads which are located from the side of said second face and aligned with this face and the free external surface of the weld bead, these milled heads having a thickness or axial dimension greater than a wall thickness and less than a weld bead thickness.

[0025] The panel according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0026] — the panel has a thickness, preferably constant, between 1 and 3 mm, and preferably between 1.5 and 2mm;

[0027] — the weld bead has a width between 5 and 15mm;

[0028] — the weld bead has a thickness between 1.5 and 4 mm, and preferably between 1.5 and 3mm;

[0029] — the countersunk heads have a thickness or axial dimension greater than 2 / 3 (two third) of said thickness of the weld bead;

[0030] — the wall and the reinforcing plate are made of metallic materials, and are for example made from the same metal alloy;

[0031] — the reinforcing plate has a thickness greater than that of the wall; alternatively, its thickness could be the same or less;

[0032] — the reinforcing plate has a thickness, preferably constant, between 2 and 4mm.

[0033] The present invention also relates to an aircraft propulsion assembly, comprising an aerodynamic panel as described above. Brief description of the figures

[0034] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the accompanying drawings in which:

[0035] [Fig-1] [Fig.1] is a schematic half-view in axial section of an assembly aircraft propulsion,

[0036] [Fig.2] [Fig.2] is a schematic perspective view of an embodiment of an aerodynamic panel according to the invention,

[0037] [Fig.3] [Fig.3] is a block diagram illustrating one embodiment of a process of manufacture according to the invention,

[0038] [Fig.4] [Fig.4] is a cross-sectional view of the panel of [Fig.2],

[0039] [Fig.5] [Fig.5] is a larger scale view of part of [Fig.3],

[0040] [Fig.6] [Fig.6] is a view similar to that of [Fig.4] and showing di dimensions,

[0041] [Fig.7a] [Fig.7a] is a schematic view of a countersunk head of a first embodiment of a fastening screw, and

[0042] [Fig.7b] [Fig.7b] is a schematic view of a countersunk head of a second embodiment of a fixing screw. Detailed description of the invention

[0043] Fig. 1 shows a propulsion unit 10 for an aircraft, this propulsion unit 10 comprising a turbomachine 12 surrounded by a nacelle 14.

[0044] The turbomachine 12 is here of the dual-flow type. This is not, however, limiting and the turbomachine 12 may be of another type, such as for example a turboprop.

[0045] The turbomachine 12 extends along a longitudinal axis X and comprises, from upstream to downstream, in the direction of gas flow, a blower 16, one or more compressor stages (for example a low pressure compressor 18 and a high pressure compressor 20), an annular combustion chamber 22, one or more turbine stages (for example a high pressure turbine 24 and a low pressure turbine 26), and a gas exhaust nozzle 28.

[0046] The blower 16, the low-pressure compressor 18, and the low-pressure turbine 26 are connected to a low-pressure shaft extending along the longitudinal axis X. The high-pressure compressor 20 and the high-pressure turbine 24 are connected to a high-pressure shaft formed around the low-pressure shaft. The low-pressure turbine 26 drives the low-pressure shaft in rotation, while the high-pressure turbine 26 drives the high-pressure shaft in rotation.

[0047] The nacelle 14 is centered on the longitudinal axis X and defines an annular vein around the turbomachine 12.

[0048] The gas flow F that passes through the fan 16 inside the nacelle 14 is divided downstream of the fan 2 into two coaxial annular flows. A first flow, called the primary flow Fl, flows into the turbomachine and is compressed in the compressors 18, 20, mixed with fuel and burned in the combustion chamber 22, then expanded in the turbines 24, 26, to finally be discharged through the nozzle 28. A second flow, called the secondary flow F2, flows in the annular channel around the turbomachine 12 and can provide the majority of the turbomachine's thrust, particularly when the latter is of the high bypass ratio type.

[0049] Furthermore, a flow of gas F3 flows around the nacelle 14 in operation.

[0050] The propulsion assembly 10 includes aerodynamic panels which are panels intended in operation to be swept by one or more gas flows running along the propulsion assembly 10. These panels can be hoods of the nacelle 14 intended to be swept by the gas flow F3, casings of the tur-bomachine 12 intended to be swept by the secondary flow F2, etc.

[0051] The present invention proposes an improvement of such a panel, as well as of its manufacturing process.

[0052] Fig. 2 illustrates an embodiment of a panel 32 according to the invention and Fig. 3 illustrates an example of a manufacturing process for this panel 32.

[0053] The panel 32 has a wall 34 having a first face 34a and a second face 34b opposite the first face 34a. This second face 34b is capable of being swept by a gas flow when the panel 32 is mounted in the propulsion assembly 10, as mentioned above.

[0054] The panel 32 may include one or more other walls 36. For example, it may include another adjacent wall 36, which is positioned next to and aligned with the wall 34. The two walls 34 and 36 are, for example, intended to be fixed or joined together.

[0055] As with wall 34, wall 36 has a first face 36a and a second face 36b opposite the first face 36a. This second face 36b is designed to be swept by a gas flow when panel 32 is mounted in propulsion assembly 10, as mentioned above. Faces 34b and 36b are intended to be aligned together.

[0056] Walls 34 and 36 can be identical.

[0057] The wall or each wall 34, 36 has a general parallelepiped shape in the example shown, although this aspect is not limiting.

[0058] The wall or each wall 34, 36 has a thickness, preferably constant, of between 1 and 3 mm, and preferably between 1.5 and 2 mm. This thickness is denoted El in [Fig. 6].

[0059] The wall or each wall 34, 36 is made of metallic materials. They are preferably made of the same metallic alloy, for example based on aluminium or titanium.

[0060] The wall or each wall 34, 36 can be flat, as in the example shown, or curved.

[0061] The panel 32 further comprises at least one reinforcing plate 38 which covers part of the first face 34a of the wall 34 and which is joined to this wall 34 by a weld bead 40.

[0062] The reinforcing plate 38 therefore extends over only part of the face 34a, and is thus located in an area that must be reinforced. The plate 38 therefore locally reinforces the wall 34.

[0063] The panel 32 may include one or more other reinforcing plates 42, 44. For example, it may include another reinforcing plate 42 which is disposed on the face 34a of the wall 34, along an edge adjacent to the wall 36, and another reinforcing plate 44 which is disposed on the face 36a of the wall 36, along an edge adjacent to the wall 34.

[0064] Each of the reinforcing plates 38, 42, 44 is secured to the wall 34, 36 by a weld bead 40.

[0065] Each of the reinforcing plates 38, 42, 44 has a first face applied against the face 34a, 36a of the wall 34 or 36, and a second face 40b opposite the first face (see figures 4 and 5).

[0066] This second face 40b is suitable for receiving an element to be fixed.

[0067] In the example shown, the second face 40b of the reinforcement plate 38 receives a fitting 46, and the second faces 40b of the reinforcement plates 42, 44 receive a splice 48 which is applied to these two faces 40b.

[0068] The or each reinforcing plate 38, 42, 44 has a general parallelepiped shape in the example shown, although this aspect is not limiting.

[0069] The reinforcing plate(s) 38, 42, 44 has a thickness, preferably constant, and advantageously greater than the thickness E1 of the wall(s) 34, 36. The reinforcing plate(s) 38, 42, 44 preferably has a thickness between 2 and 4 mm. This thickness is denoted E2 in [Fig. 6].

[0070] The reinforcing plate or plates 38, 42, 44 are made of metallic materials. They are preferably made of the same metallic alloy as the walls 34, 36, for example based on aluminium or titanium.

[0071] The or each reinforcing plate 38, 42, 44 can be flat, as in the example shown, or curved.

[0072] The panel 32 further includes mounting holes 50 for screws 52, 54, 56 for fixing the aforementioned elements, such as the fitting 46 and the splice 48.

[0073] The holes 50 are through holes and are formed in the wall or each wall 34, 36 and in the reinforcement plate or each plate 38, 42, 44, as well as in the elements to be fixed.

[0074] In the example shown, the reinforcing plate 38 includes two holes 50 which are aligned with two holes 50 in the wall 34 and two holes in the fitting 46. These holes 50 receive fixing screws 52. The reinforcing plate 42 includes eight holes 50 which are aligned with eight holes in the wall 34 and eight holes in the splice 48. These holes 50 receive fixing screws 54. The reinforcing plate 44 includes eight holes 50 which are aligned with eight holes in the wall 36 and eight other holes in the splice 48. These holes 50 receive fixing screws 56.

[0075] Each of the screws 52, 54, 56 is of the countersunk head type and comprises a countersunk head 58 located at one end of a shank 60 which is at least partially threaded (see [Fig. 5]). The The rod 60 passes through the holes 50 and the countersunk head 58 is housed in a flare 50a of the hole 50 formed in the wall 34, 36. The countersunk head 58 is intended to be entirely housed in this flare 50a, as can be seen in the drawings, so that its end surface 58b is aligned with the face 34b, 36b of the wall 34, 36.

[0076] As can be seen in figures 7a and 7b, this end surface 58b may include a recess 61 to allow engagement with a tightening / loosening tool of the screw 52, ​​54, 56, in particular when the latter is of the disassembly type. Alternatively, the screw 52, ​​54, 56 is of the non-removable type and does not include a recess on its end surface 58b, which is then smooth.

[0077] The shank 60 of each screw 52, ​​54, 56 receives a nut 62 which is screwed and tightened against the element to be fixed. In the case where the screw 52, ​​54, 56 is of the non-removable type, the end of the shank 60, opposite the countersunk head 58, may include a recess 61 for engaging with a tool to prevent the screw from rotating during screwing and tightening of the nut 62 (see [Fig. 5]).

[0078] The screw or screws 52, 54, 56 has a diameter noted D in [Fig.6], this diameter being that of its shank 60. The diameter of the screw head 58 is noted A.

[0079] The countersunk head 58 of the screw or each screw 52, ​​54, 56 has a thickness or axial dimension (along the axis of elongation of the screw) which is noted H.

[0080] Preferably, H is greater than El and is between El and E1+E2.

[0081] The panel 32 further includes weld beads 40 for joining the reinforcement plates 38, 42, 44 to walls 34, 36, as mentioned above.

[0082] In the example shown, a first weld bead 40 is formed between the wall 34 and the reinforcement plate 38. A second weld bead 40 is formed between the wall 34 and the reinforcement plate 42, along the aforementioned edge of the wall 34, and a third weld bead 40 is formed between the wall 36 and the reinforcement plate 44, along the aforementioned edge of the wall 36.

[0083] Each of the weld beads 40 has a generally elongated shape.

[0084] Each weld bead 40 can be made in a single pass. Alternatively, the weld bead 40 could be made in two or more passes.

[0085] The distinctive feature of each weld bead 40 is that it is formed by friction stir welding (or FSW welding). This welding technique is known to those skilled in the art of welding and will not be described in detail hereafter.

[0086] The weld bead 40 has a free external surface 40a which is aligned with the second face 34b, 36b of the corresponding wall 34, 36. The weld bead 40 extends in thickness from this face 34b, 36b over the entire thickness E1 of the wall 34, 36 and over at least a part of the thickness E2 of the reinforcing plate 38, 42, 44 (Figures 5 and 6).

[0087] The thickness of the weld bead 40 is noted as E3 in [Fig.6]. It is for example between 1.5 and 4mm, and preferably between 1.5 and 3mm.

[0088] The weld bead 40 has a width (measured in a direction transverse to the elongation axis of the weld bead) that is greater than D and A. D and A can be between 4 and 12 mm. The width, denoted L in [Fig. 6], of the weld bead 40 is preferably between 5 and 15 mm.

[0089] Preferably, H is less than or equal to E3 and more preferably strictly less than E3.

[0090] Preferably, H is greater than 2 / 3 of E3.

[0091] Preferably, H is greater than or equal to El + 1 / 3 x EL

[0092] According to the invention, the holes 50 are formed in the weld bead 40, as shown in the drawings. The holes 50 are therefore formed in the panel 32 after welding.

[0093] Figure 3 illustrates a method for manufacturing a panel 32 according to an embodiment of the invention.

[0094] The process includes several steps, some of which are optional.

[0095] The process includes, in particular, the following steps:

[0096] a) apply at least one reinforcing plate 38, 42, 44 to a first face 34a of a wall 34, the reinforcing plate 38, 42, 44 covering part of this first face 34a and the wall 34 having a second face 34b, opposite the first face, which is a face suitable for being swept by a gas flow when the panel 32 is mounted in a propulsion assembly,

[0097] b) to join the reinforcing plate 38, 42, 44 and the wall 34 by friction stir welding using a tool having a welding head which is moved on the second face 34b so as to create a weld bead 40 which extends in thickness from the second face 34b over a whole thickness E1 of the wall 34 and over at least a part of a thickness E2 of the reinforcing plate 38, 42, 44,

[0098] c) making through holes 50 through the wall 34 and the reinforcing plate 38, 42, 44, these holes 50 being formed through the weld bead 40, and

[0099] d) mounting screws 52, 54, 56 in the holes 50, these screws 52, 54, 56 having countersunk heads 58 which are located on the side of the second face 34b and aligned with this face 34b, these countersunk heads 58 having a thickness H or axial dimension greater than the thickness El of the wall 34 and less than the thickness E3 of the weld bead 40.

[0100] As mentioned above, the weld bead 40 can be made in a single pass in step b).

[0101] The method may include, after step d), a step e) of fixing an element onto the reinforcing plate 38, 42, 44, on the side opposite the wall 34, this element having holes 50 through which screws 52, 54, 56 pass, which receive nuts 62 which are screwed onto the screws 50 and which bear against the element. The element is, for example, a fitting 46 or a splice 48.

[0102] The process may include, between steps b) and c), a step i) of sanding the free external surface 40a of the weld bead 40.

[0103] The present invention makes it possible in particular to obtain optimized panels that meet the right requirements for mass, cost and integration of fixings.

Claims

Claims

1. Method for manufacturing an aerodynamic panel (32) for an aircraft propulsion unit (10), the method comprising the following steps: a) applying at least one reinforcing plate (38, 42, 44) to a first face (34a) of a wall (34), the reinforcing plate (38, 42, 44) covering a portion of this first face (34a) and the wall (34) comprising a second face (34b), opposite the first face (34a), which is a face capable of being swept by a gas flow when the panel (32) is mounted in a propulsion unit (10), b) securing the reinforcing plate (38, 42, 44) and the wall (34, 36) by friction stir welding using a tool comprising a welding head which is moved over the second face (34b) so as to create a weld bead (40) which extends in thickness from the second face (34b) over an entire thickness (El) of the wall (34) and over at least a part of a thickness (E2) of the reinforcement plate (38, 42, 44),c) making through holes (50) through the wall (34) and the reinforcement plate (38, 42, 44), these holes (50) being formed through the weld bead (40), and d) mounting screws (52, 54, 56) in the holes (50), these screws (52, 54, 56) having countersunk heads (58) which are located on the side of said second face (34b) and aligned with this face (34b), these countersunk heads (58) having a thickness (H) or axial dimension greater than said thickness (El) of the wall (34) and less than said thickness (E3) of the weld bead (40).,

2. A method according to claim 1, wherein the weld bead (40) is made in a single pass in step b).

3. Method according to claim 1 or 2, in which it comprises, after step d), a step e) of fixing an element on the reinforcing plate (38, 42, 44), on the side opposite to said wall (34), this element comprising holes (50) crossed by said screws (52, 54, 56) which receive nuts (62) which are screwed onto the screws (52, 54, 56) which bear on the element.

4. A method according to claim 3, wherein the element is a fitting (58) or a fishplate (60).

5. Method according to one of the preceding claims, in which it comprises, between steps b) and c), a step i) of sanding a

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12. free external surface (40a) of the weld bead (40). Method according to one of the preceding claims, in which the panel (34) has a thickness (El), preferably constant, of between 1 and 3 mm, and preferably between 1.5 and 2 mm. Method according to one of the preceding claims, in which the welding codon (40) has a width (L) of between 5 and 15 mm. Method according to one of the preceding claims, in which the welding codon (40) has a thickness (E3) of between 1.5 and 4 mm, and preferably between 1.5 and 3 mm. Method according to one of the preceding claims, in which the countersunk heads (58) have a thickness (H) or axial dimension greater than 2 / 3 of said thickness (E3) of the weld bead (40). Method according to one of the preceding claims, in which the wall (34) and the reinforcing plate (38, 42, 44) are made of metallic materials, and are for example made of the same metallic alloy. Aerodynamic panel (32) for an aircraft propulsion unit (10), this panel (32) being obtained by the method according to one of the preceding claims and comprising: - a wall (34) comprising a first face (34a) and a second face (34b) opposite the first face (34a), this second face (34b) being capable of being swept by a flow of gas when the panel (32) is mounted in a propulsion unit (10), - a reinforcing plate (38, 42, 44) which covers a part of this first face (34a) and which is secured to the wall (34) by a weld bead (40), this weld bead (40) comprising a free external surface (40a) which is aligned with said second face (34b), this weld bead (40) comprising holes (50) passing through the wall (34) and the reinforcing plate (38, 42, 44), and - screws (50) mounted in the holes (50) and comprising countersunk heads (58) which are located on the side of said second face (34b) and aligned with this face (34b) and the free external surface (40a) of the weld bead (40), these countersunk heads (58) having a thickness (H) or axial dimension greater than a thickness (El) of the wall (34) and less than a thickness (E3) of the weld bead (40). Aircraft propulsion assembly (10), comprising an aerodynamic panel (32) according to claim 11.

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