METHOD FOR ASSEMBLING AN AERONAUTICAL PANEL
By measuring and applying overstress to aeronautical panel walls, the method ensures consistent panel shape and geometry by using stiffening elements to maintain the nominal position, addressing manufacturing variability and deformation issues.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- SAFRAN NACELLES
- Filing Date
- 2024-11-18
- Publication Date
- 2026-05-22
AI Technical Summary
Current assembly methods for aeronautical panels do not account for the manufacturing variability and natural deformation of parts, leading to geometric issues and unpredictable shape changes during assembly, which are difficult to predict and correct.
A method involving measuring the natural deformation of the panel wall, applying an overstress to the wall using a frame, and fixing stiffening elements to maintain the panel's nominal shape after removal from the frame, ensuring the wall retains its nominal position.
The method effectively counters natural deformation by applying calculated overstress, allowing the panel to maintain its intended shape and geometry post-assembly, adapting to individual part variations and material properties.
Smart Images
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Abstract
Description
Title of the invention: METHOD FOR ASSEMBLING AN AERONAUTICAL PANEL Technical field of the invention
[0001] The present invention relates to a method for assembling an aeronautical panel. Technical background
[0002] In this application, an aeronautical panel means a panel for aeronautical use, such a panel being able to equip an aircraft or an aircraft engine such as a turbomachine. It may, for example, be a nacelle panel, an acoustic panel, a nozzle panel, a cowling panel, an air intake panel, a grille panel, a thrust reverser panel, etc.
[0003] Furthermore, in the present application, such an aeronautical panel is formed by assembling a wall with stiffening elements. The wall has a curved shape, and the stiffening elements are intended to stiffen the wall. The stiffening elements are attached to and fixed onto the wall. The wall and the stiffening elements can be made of different materials, for example, the wall being made of a composite material and the stiffening elements being made of a metallic material.
[0004] The present invention thus relates to a method of assembling such an aeronautical panel.
[0005] To achieve such an assembly, an assembly jig can be used to reference the parts relative to each other. Such a jig consists of a structure onto which retaining elements are mounted to position the various parts of the panel.
[0006] In current technology, the frame is designed in relation to the nominal shape of the parts and therefore does not take into account their manufacturing variability or their natural deformation.
[0007] Depending on their design, materials, and manufacturing processes, parts can be more or less flexible and deformable. Their geometry is also quite variable (±2 mm on average for composite parts, ±0.6 mm for metal parts). Several parts manufactured in the same way on the same mold can therefore have a geometry that varies by several millimeters due to phenomena generated during manufacturing (chemical reactions related to the materials used, curing, etc.). This variation is currently neither calculable nor sufficiently repeatable to be predicted.
[0008] During assembly, the natural deformation of the parts can be countered by using the aforementioned retaining devices and shims and by putting the parts under stress, which can generate geometric problems at the end of the assembly.
[0009] The panel is thus positioned at nominal height and, if there is still play between its parts, an operator has the possibility of filling the gaps, for example with polymerizable resin.
[0010] The parts are then drilled and riveted or screwed to maintain their position relative to each other. The panel positioning devices on the frame are removed, and the panel is removed from the assembly frame.
[0011] However, removing the retaining elements releases the positioning constraints, and the panel wall may assume a shape different from its nominal form. The wall may also be "driven" by the more rigid stiffening elements to deform differently. This phenomenon is difficult to predict and leads to geometry problems during the final inspection of the panel.
[0012] There is therefore a need for a process to counter the natural deformation of the wall of a panel and to ensure that at the end of the assembly of this panel, this natural deformation remains countered.
[0013] The invention offers a solution to this need which is simple, effective and economical. Summary of the invention
[0014] The invention relates to a method for assembling an aeronautical panel, this panel comprising a curved wall and stiffening elements which are attached and fixed to the wall and which have a stiffness greater than that of the wall, in which it comprises the following steps:
[0015] a) measure dimensions of the wall in its free state without stress, compare the measured dimensions to reference dimensions corresponding to a wall of nominal shape, and determine deviations between these dimensions, these deviations corresponding to a natural deformation of the wall in its free state without stress,
[0016] b) mount the wall on a frame, attach the stiffening elements to the wall, and adjust the frame to apply at least one overstress to the wall such that the wall adopts a shape different from its nominal shape, and
[0017] c) fix the stiffening elements to the wall to form the panel, release said at least one overstress applied by the frame, and remove the panel from the frame, the stiffening elements applying at least one stress to the wall so that it adopts its nominal shape.
[0018] In the context of the present invention, a distinction is made between the stressing of the wall and the overstressing of the wall. The overstressing is achieved by the frame, while the stressing is achieved by the stiffening elements. The overstress is greater than the stress. In its free state, without stress, the wall has a natural deformation. Applying stress to the wall with stiffening elements allows it to assume its nominal position. Applying overstress to the wall with the frame allows it to adopt a deformed position that differs from both its free state and its nominal position. The overstress is calculated so that, after attaching the stiffening elements to the wall and removing the panel from the frame, the wall remains constrained by the stiffening elements and retains its aforementioned nominal position. To achieve this, the frame is adjusted to accommodate this overstress, which is calculated based on the differences between the measured dimensions of the wall and the reference dimensions.
[0019] The method according to the invention may comprise one or more of the following features, taken individually or in combination with each other: - overstresses in at least two different directions are applied by the frame on the wall, and, in step c), stresses in at least two different directions are applied by the stiffening elements on the wall; - the adjustment of the frame in step b) is carried out mechanically by an operator directly on the frame; - the adjustment of the frame in step b) is carried out automatically by a computer system; - the computer system is capable of determining the adjustment to be made on the frame according to the measured dimensions or the aforementioned deviations; - the measured dimensions or the aforementioned deviations are recorded on a computer network or in a chip or code present on the wall or one of the said stiffening elements; - step a) is carried out by the building itself which is able to measure the dimensions of the wall, compare the measured dimensions to reference dimensions, and determine the differences between these dimensions; - the adjustment in step b) is carried out using one or more elements chosen from among handwheels, spindles, slides, and cylinders; - the frame is equipped with force and / or displacement sensors, for example without contact, and / or at least one information display screen, for example of measured dimensions or applied overstress; - the structure is capable of issuing an alert when the overstress to be applied in step b) is likely to exceed an permissible limit for the wall; - the stiffening elements are fixed to the wall by riveting, screwing, and / or bolting; - the wall has a general shape in the form of a portion of a cylinder and the stiffening elements form a frame in the form of a portion of a cylinder around the wall; - the frame formed by the stiffening elements includes two lateral elements attached and fixed respectively to two longitudinal edges located at the two opposite circumferential ends of the wall, and a curved element which extends between the lateral elements and around the wall, and for example a middle part of the wall; - the panel is chosen from a nacelle panel, an acoustic panel, a nozzle panel, a cowling panel, an air inlet panel, a grid panel, and a thrust reverser panel; - the wall is made of composite or metallic material, and the stiffening elements are made of metallic or composite material; - the frame comprises an upper base and a lower support on the ground, the wall being mounted on the upper base so that its curved shape is around a vertically oriented axis of revolution. Brief description of the figures
[0020] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:
[0021] [Fig-1] [Fig.1] is a schematic perspective view of an aeronautical panel,
[0022] [Fig. 2a-2c] Figures 2a to 2c are very schematic views of a process assembly of an aeronautical panel, which does not correspond to the invention,
[0023] [Fig. 3a-3c] Figures 3a to 3c are very schematic views of a process assembly of an aeronautical panel, which corresponds to the invention,
[0024] [Fig.4] [Fig.4] is a schematic perspective view of an assembly frame on which an aeronautical panel is mounted,
[0025] [Fig.5] [Fig.5] is a schematic side view of the frame and panel of [Fig.4],
[0026] [Fig.6] [Fig.6] is a schematic top view of the frame and panel of the [Fig.4]
[0027] [Fig.7] [Fig.7] is a very schematic view of the parts of an aeronautical panel and the forces to be applied to these parts to counteract deformations,
[0028] [Fig.8] [Fig.8] is a view similar to that of [Fig.4] and shows forces applied by the frame on the panel, and
[0029] [Fig.9] [Fig.9] is a flowchart showing steps of a process according to the invention. Detailed description of the invention
[0030] Fig. 1 represents an example of an embodiment of an aeronautical panel 10 according to the invention.
[0031] The panel 10 can be a nacelle panel, an acoustic panel, a nozzle panel, a cowling panel, an air inlet panel, a grid panel, a thrust reverser panel, etc.
[0032] The panel 10 comprises a wall 12 curved around an axis A and stiffening elements 14 which are attached and fixed to the wall 12 and which have a stiffness greater than that of the wall 12.
[0033] In the example shown, the wall 12 has a general shape in the form of a portion of a cylinder and the stiffening elements 14, 15 form a frame in the form of a portion of a cylinder around the wall 12.
[0034] In the example shown, the frame formed by the stiffening elements 14, 15 comprises two lateral elements 14 attached and fixed respectively on two longitudinal edges located at the two opposite circumferential ends of the wall 12, and a curved element 15 which extends between the lateral elements 14 and around the wall 12, and for example a middle part of the wall 12.
[0035] The stiffening elements 14, 15 can be similar to elongated rails along axis A, straight or curved. In the illustrated example, the stiffening elements 14, 15 are shown on the outside of panel 10 but could alternatively be shown on the inside of panel 10, or on both the inside and outside of panel 10.
[0036] The wall 12 can be made of composite or metallic material, and the stiffening elements 14 can be made of metallic or composite material.
[0037] The wall 12 and the stiffening elements 14 can be considered "deformable" and may have a natural deformation. The assembly of the panel 10 must therefore be carried out under stress to bring the parts into their nominal position.
[0038] Figure 2a shows the wall 12, which has a shape different from its nominal shape due to its natural deformation. During the assembly of the wall 12 and the stiffening elements 14 on an assembly frame 16, stresses can be applied to the parts so that they adopt a nominal shape on the frame 16 (Figure 2b).
[0039] However, when the constraints on the frame 16 are released, the panel 10 returns to a deformed state due to elastic rebound, in which the wall 12 has a different shape than its nominal shape (Figure 2c). This means that, even if the parts are assembled nominally on the frame 16, after assembly, the tolerances are no longer compliant.
[0040] In the current technique, the initial dimensions of the wall 12 are not taken into account. Furthermore, the tolerances of the parts are wide, and it is not possible to apply the same stresses to different walls that do not have the same natural deformations.
[0041] The invention proposes a solution, schematically represented in Figures 3a to 3c, in which, after assembly, the stiffening elements 14 apply a stress to the wall 12 such that the wall 12 adopts and maintains its nominal position. To achieve this, the panel 10 is assembled onto the frame 16 by applying an overstress to the panel 10, the overstress being naturally greater than the stress.
[0042] Contrary to the solution in figures 2a-2c, which would consist of the wall 12 adopting its nominal position during assembly on the frame 16, the invention consists, on the contrary, of the wall 12 adopting its nominal position only after removal of the panel 10 from the frame 16.
[0043] The process according to the invention essentially comprises three steps a), b) and c). [Fig.9] illustrates a flowchart of this process.
[0044] According to the first step a), dimensions of the wall 12 are measured in the free state without stress (substep a1a), the measured dimensions are compared to reference dimensions corresponding to a wall 12 of nominal shape (substep a2), and deviations between these dimensions are determined (substep a3), these deviations corresponding to a natural deformation of the wall 12 in the free state without stress.
[0045] According to the second step b), the wall 12 is mounted on the frame 16 (sub-step bl), the stiffening elements 14 are attached to the wall 12 (sub-step b2), and the frame 16 is adjusted to apply on the wall 12 at least an overstress S such that the wall 21 adopts a shape different from its nominal shape (sub-step b3 - figure 3b).
[0046] According to the third step c), the stiffening elements 14 are fixed to the wall 12 to form the panel 10 (substep c1), said at least one overstress S applied by the frame 16 is released (substep c2), and the panel 10 is removed from the frame 16 (substep c3), the stiffening elements 14 applying at least one stress S to the wall 12 so that it adopts its nominal shape (figure 3c).
[0047] We will now describe in more detail the different steps and sub-steps of the process according to the invention.
[0048] Step a)
[0049] Step a) can be carried out by an operator who can thus carry out substeps a1), a2) and a3). Substep a1 is for example carried out by laser measurement.
[0050] Alternatively, step a1) could be carried out by a supplier who would then have to communicate the dimensions of the wall 12 with their supply. An operator could then carry out substeps a2) and a3).
[0051] Alternatively, substep a3) could be carried out by a computer system using input data recorded by an operator in that computer system, corresponding to the measured dimensions. This computer system could then include a memory containing a record of the reference dimensions.
[0052] In yet another variant, step a) could be carried out by the frame 16 itself, which would thus be capable of performing substeps a1), a2), a3) and therefore of measuring the dimensions of the wall 12, comparing the measured dimensions to reference dimensions, and determining the differences between these dimensions. In this case, it is understood that the wall 12 could also be mounted on the frame 16 during step a).
[0053] Step b)
[0054] In sub-step bl), the wall 12 is mounted on the frame 16.
[0055] Figures 4 to 8 show an example of a frame 16 which can be used in the context of the present invention.
[0056] In the example shown, the frame 16 includes an upper base 18 and a lower support 20 on the ground.
[0057] The wall 12 is mounted on the upper base 18 so that the axis A is oriented vertically.
[0058] In substep b2, the stiffening elements 14 are attached to the wall 12. The frame 16, and in particular its upper base 18, may include uprights 22 oriented vertically and capable of holding the stiffening elements 14 in position on the wall 12.
[0059] In substep b3, the frame 16 is adjusted to apply the aforementioned overstress S to the wall 12.
[0060] Overstresses S in at least two different directions can be applied by the frame 16 on the wall 12, as schematically represented by arrows in figures 3b and 8.
[0061] Deformations can indeed be multidirectional. Depending on the parts, the joints, and their measured deformation, the adjustment of the frame 16 could be unidirectional or multidirectional. In this case, the adjustment can be made in two (or more) directions simultaneously or sequentially (for example, if the part is twisted, stress is applied first along axis A and then along an axis perpendicular to axis A). This sequence is calculated in the same way as the force to be applied, as it can differ depending on the directions. Furthermore, the adjustment force can also differ depending on the areas of the part. A part with variations in thickness may thus require a greater stress force in its thicker areas than in its thinner areas. The density of the composite also has an effect on stiffness, which induces variations in the stress force to be applied.
[0062] The adjustment of the frame 16 in step b) can be carried out mechanically by an operator directly on the frame 16. This adjustment can be carried out using one or more elements chosen from among handwheels, spindles, slides, and cylinders for example.
[0063] Alternatively, the adjustment of the frame 16 in step b) can be carried out automatically by a computer system 24, which may be the same as that mentioned above. The computer system 24 is schematically represented in [Fig. 4].
[0064] This computer system 24 is capable of determining the adjustment to be made on the frame 16 according to the measured dimensions or the aforementioned deviations.
[0065] The measured dimensions or the aforementioned deviations can be recorded on a computer network or in a chip or code present on the wall or one of said stiffening elements.
[0066] Reference 25 in [Fig.4] represents, for example, an RFID chip or a QR code present on wall 12.
[0067] In the aforementioned case where step a) is performed by the frame 16 itself, it is understood that the frame 16 would be equipped with devices for measuring the dimensions of the wall 12. The computer system 24 associated with the frame 16 could then be configured to compare the measured dimensions with the reference dimensions and calculate the aforementioned discrepancies. The measured dimensions or the calculated discrepancies could be displayed on one or more information display screens 26 present on the computer system and / or directly on the frame 16 ([Fig. 5]).
[0068] The frame 16 is advantageously equipped with force sensors 28 ([Fig.6]), for example non-contact (of the laser type for example), which allow the overstress S applied to the wall 12 to be measured.
[0069] The level of overstress is, for example, calculated from the aforementioned deviations and an analysis of the stiffness of the panel components. It is known that the overstress force F to be applied (in Newtons) is given by the following formula: F = kx and is a function of the stiffness of each component (in Newtons / meter) and the deformation x to be applied to each component (in meters).
[0070] In the present case, as illustrated in [Fig. 7], in the free state without constraint, each of the parts of the panel 10 may have a certain natural deformation that must be compensated for (arrows DI to D4). To counteract these deformations, it is necessary to apply additional stresses to the parts in different positions, which are illustrated by arrows H1 to H4 in [Fig. 8]. Each of these additional stresses is calculated as a function of the stiffness of the part and the deformation to be applied to the part according to the aforementioned formula. Insofar as the stiffness of the stiffening elements 14 is greater than that of the wall 12, they are used to counteract the deformation of the wall 12.
[0071] The forces to be applied compensate for the various deformations and allow the nominal position to be reached (i.e., DI + D2 = 0, for example). Knowing that F = kx, where x is the deformation, then:
[0072] [Math.l] kt + k. “ u
[0073] The displacements D are measured (by the frame, the supplier, or the operators according to the variant chosen), the stiffnesses depend on the parts, and thanks to the formula above, the forces to be applied to reach the nominal position are calculated.
[0074] The frame 16 is preferably capable of issuing an alert when the overstress S to be applied in step b) is likely to exceed an permissible limit for the wall 12, a limit which would be likely to damage the wall 12 or affect its lifespan.
[0075] Step c)
[0076] The stiffening elements 14 fixed to the wall 12 allow the panel 10 to be fixed at the sub-step cl in a deformed position different from the nominal position.
[0077] The stiffening elements 14 are fixed to the wall 12 for example by riveting, screwing, and / or bolting.
[0078] The overstress S is then released and the panel 10 is removed from the frame 16.
[0079] The panel 12 then adopts its nominal position thanks to the fact that the elements of stiffening elements 14 continue to apply a stress S to the wall 12. As illustrated in Figure 3c, stresses S in at least two different directions can be applied by the stiffening elements 14 on the wall 12.
[0080] The method according to the invention thus makes it possible to adapt to the geometries of the parts. A conventional frame is only adjusted once, with respect to the nominal geometry. The frame 16 used in the context of the invention is adjusted for each part to adapt to its specific geometry and deformation.
[0081] This allows for consideration of the intrinsic effects of the materials used to manufacture the parts, which is not the case today. Indeed, the deformation of parts is currently considered a constraint, a cause of non-conformity, whereas the invention uses it as a parameter to be taken into account during assembly.
[0082] The invention can be used in any aeronautical assembly of deformable parts, metallic or composite, provided that the process uses a frame to position them in a reference frame. The resulting panel must consist of a wall capable of natural deformation and more rigid stiffening elements that are able to stiffen the geometry once the assembly is complete.
Claims
Demands
1. A method for assembling an aeronautical panel (10), said panel (10) comprising a curved wall (12) and stiffening elements (14) that are attached to and fixed to the wall (12) and that have a stiffness greater than that of the wall (12), wherein it comprises the following steps: a) measuring dimensions of the wall (12) in its free, unstressed state, comparing the measured dimensions to reference dimensions corresponding to a wall of nominal shape, and determining deviations between these dimensions, these deviations corresponding to a natural deformation of the wall in its free, unstressed state; b) mounting the wall (12) on a frame (16), attaching the stiffening elements (14) to the wall (12), and adjusting the frame (16) to apply at least one overstress (S) to the wall (12) such that the wall (12) adopts a shape different from its nominal shape; and c) fixing the stiffening elements (14) to the wall (12) to form panel (10),release said at least one overstress (S) applied by the frame (16), and remove the panel (10) from the frame (16), the stiffening elements (14) applying at least one stress (S) to the wall (10) so that it adopts its nominal shape.
2. A method according to claim 1, wherein, in step b), overstresses (S) in at least two different directions are applied by the frame (16) on the wall (12), and, in step c), stresses (S) in at least two different directions are applied by the stiffening elements (14) on the wall (12).
3. Method according to claim 1 or 2, wherein the adjustment of the frame (16) in step b) is carried out mechanically by an operator directly on the frame (16).
4. Method according to claim 1 or 2, wherein the adjustment of the frame (16) in step b) is carried out automatically by a computer system (24).
5. Method according to claim 4, wherein the computer system (24) is capable of determining the adjustment to be made on the frame (16) according to the measured dimensions or the aforementioned deviations.
6. A method according to claim 5, wherein the measured dimensions or the aforementioned deviations are recorded on a network computer or in a chip (25) or code present on the wall (12) or one of said stiffening elements (14).
7. A method according to claim 5, wherein step a) is carried out by the frame (16) itself which is capable of measuring the dimensions of the wall (12), comparing the measured dimensions to reference dimensions, and determining the differences between these dimensions.
8. A method according to any one of the preceding claims, wherein the adjustment in step b) is achieved by means of one or more elements selected from handwheels, spindles, slides, and cylinders.
9. A method according to any one of the preceding claims, wherein the frame (16) is equipped with force and / or displacement sensors (28), for example non-contact, and / or at least one display screen (26) for displaying information, for example measured dimensions or applied overstress.
10. A method according to any one of the preceding claims, wherein the frame (16) is capable of issuing an alert when the overstress (S) to be applied in step b) is likely to exceed an permissible limit for the wall (12).
11. A method according to any one of the preceding claims, wherein the stiffening elements (14) are fixed to the wall by riveting, screwing, and / or bolting.
12. A method according to any one of the preceding claims, wherein the wall (12) has a general form in the shape of a portion of a cylinder and the stiffening elements (14, 15) form a frame in the shape of a portion of a cylinder around the wall (12).
13. A method according to the preceding claim, wherein the frame formed by the stiffening elements (14, 15) comprises two lateral elements (14) attached and fixed respectively on two longitudinal edges located at the two opposite circumferential ends of the wall (12), and a curved element (15) which extends between the lateral elements (14) and around the wall (12), and for example a middle part of the wall (12).
14. A method according to any one of the preceding claims, wherein the panel (10) is selected from a nacelle panel, an acoustic panel, a nozzle panel, a cowling panel, an air inlet panel, a grid panel, and a thrust reverser panel.
15. A method according to any one of the preceding claims, wherein the wall (12) is made of composite or metallic material, and the stiffening elements (14) are made of metallic or composite material.
16. A method according to any one of the preceding claims, wherein the frame (16) comprises an upper base (18) and a lower support (20) for ground support, the wall (12) being mounted on the upper base (18) so that its curved shape is about a vertically oriented axis of revolution (A).