Damping system including primary damper devices and secondary damper devices of different stiffness, related structure and aircraft

Abstract

In order to increase the compactness of a damping system intended in particular to operate in dynamic landing situations, a damping system (4) is proposed, comprising a primary damper device (12) and a secondary damper device (14). The primary damper device (12) comprises at least one beam (16), each beam (16) extending along a longitudinal axis (X-X), the damping system (4) being configured such that: at rest, the stiffness of the primary damper device (12) along the longitudinal axis (X-X) is greater than the stiffness of the secondary damper device (14); when a force applied to the damping system (4) along the longitudinal axis (X-X) has a value less than a limit value, each beam (16) remains in a compressed state; and when the force has a value greater than or equal to the limit value, each beam (16) undergoes buckling and the secondary damper device (14) undergoes elastic deformation.

Description

Technical Field

[0001] The invention relates to a damping system extending along a longitudinal axis. The invention also relates to an aircraft structure comprising such a damping system and an aircraft comprising such a structure.

[0002] The invention is applicable in the field of aviation, in particular to dissipating impact energy applied to an aircraft in the event of landing or collision. Background Art

[0003] An aircraft comprises a set of mechanical elements which are indispensable for its flight, including a skin reinforced by circumferential frames and longitudinal stiffeners. This set of mechanical elements which are indispensable for flight is generally called the "primary structure".

[0004] The aircraft also comprises structures assigned a specific function. For example, such a structure is a floor structure, such as a passenger cabin floor structure. According to another example, in the field of cargo transport, such a structure is a vertical partition wall whose function is to separate the cockpit from the volume of the aircraft intended for receiving containers.

[0005] Typically, such a structure comprises crosspieces and a network of spacers, the crosspieces being connected to a circumferential frame by the ends of the crosspieces. For example, each spacer is connected at one end of the spacer to a corresponding crosspiece of the structure and at the other end of the spacer to a corresponding circumferential frame. Such a network of spacers is designed, for example, to support the structure so that it is stiffened or even to provide a damping function.

[0006] In the case of passenger transport, during a dynamic landing, it is necessary to optimally dissipate the impact energy so that the vibration shocks (including vertical shocks) caused to the cabin passengers remain below regulatory limits, or as low as possible.

[0007] Furthermore, in the case of freight, the container may be thrown forwards and it is therefore necessary to try and protect the crew in the cockpit from the shocks generated by such displacement of the container.

[0008] It has been envisaged to provide the aforementioned structure with spacers in the form of compression beams of composite material. For example, as described in patent document WO 2009 / 101372 A1, each such spacer comprises a gusset at one of its ends, which is suitable for cutting the spacer under the action of high levels of compression forces, such as caused by dynamic landings. In this case, the spacer forms a damping device.

[0009] However, this structure is not entirely satisfactory.

[0010] In fact, in this structure, the dimensions of each spacer are adjusted to withstand the cutting means of the corresponding corner plate when the spacer is subjected to a compressive force corresponding to normal use (for example, in the case of a floor, the compressive force caused by the load of the floor), so that cutting of the spacer occurs only in the event of a collision.

[0011] This often results in oversized spacers, which in turn lead to an increase in the size of such spacers compared to conventional spacers, which is particularly detrimental in the aerospace sector.

[0012] It is therefore an object of the present invention to provide a damping system which is able to dissipate impact energy in a satisfactory manner while having smaller dimensions compared to damping devices of the prior art. Summary of the invention

[0013] To this end, the subject of the invention is a damping system of the type mentioned above, comprising:

[0014] a first base and a second base arranged at a distance from each other along a longitudinal axis;

[0015] A main damper device comprises at least one beam, each beam extending along a longitudinal axis, each beam comprising two opposite ends and being attached to the first base by one of its two ends and to the second base by the other of its two ends.

[0016] The secondary damper device includes two opposite ends, the secondary damper device is connected to the first base through one of its two ends and connected to the second base through the other of its two ends;

[0017] The damping system is constructed such that:

[0018] At rest, the stiffness of the primary damper arrangement along the longitudinal axis is greater than the stiffness of the secondary damper arrangement along the longitudinal axis;

[0019] each beam is held in compression when a force applied to the damping system to push the first base toward the second base has a value less than a predetermined limit value; and

[0020] When the force has a value greater than or equal to the limit value, each beam undergoes buckling and the secondary damper device undergoes elastic deformation.

[0021] In practice, the primary damper device and the secondary damper device are such that during the application of a longitudinal force on the damping system to push the first base towards the second base, and as long as the value of the longitudinal force is less than a limit value, the primary damper device bears most of the force, the stiffness of the primary damper device being greater than the stiffness of the secondary damper device. In this case, the beam remains in compression.

[0022] If the value of this force reaches a limit value, the beam buckles and dissipates a portion of the energy associated with the longitudinal force exerted on the damping system. Furthermore, due to the buckling, the beam is no longer able to withstand the longitudinal force. In this case, the secondary damper device undergoes deformation and withstands the force exerted on the damping system and thus dissipates another portion of the energy associated with the longitudinal force, in particular by elastic deformation. Thus, dissipating the energy associated with the force by using the primary damper device and then by using the secondary damper device successively provides the damping system according to the invention with the ability to dissipate energy more effectively than the devices of the prior art.

[0023] Therefore, under the same performance, the damping system according to the present invention may have a smaller size compared to the above-mentioned prior art structure.

[0024] According to other advantageous aspects of the invention, the damping system comprises one or more of the following features either alone or in any technically possible combination:

[0025] The secondary damper device comprises at least one flexure member, each flexure member comprising two opposite ends, each flexure member being connected to the first base by one of its two ends and to the second base by the other of its two ends, each flexure member being configured to undergo elastic bending when the force has a value within a range exceeding a limit value;

[0026] Each flexural member is hollow and / or each beam is solid;

[0027] Each beam is radially closer to the longitudinal axis than each flexure member;

[0028] At least one curved member includes two arched portions, each of the two arched portions includes two opposite ends, the two ends of each curved member are each formed by connecting two corresponding ends of the two arched portions, the two arched portions each have a concave surface, and the concave surfaces of the two arched portions are opposite to each other;

[0029] The damping system includes a single flexure member having circular symmetry about a longitudinal axis;

[0030] at least one curved member including a straight portion extending along a longitudinal axis and a plurality of hoops, the straight portion including two opposite ends, each of the hoops including two opposite ends, each of the two ends of each hoop being attached to a respective end of the straight portion;

[0031] The secondary damper device includes at least one mesh element, each mesh element has a three-dimensional lattice structure, each mesh element includes two opposite ends, each mesh element is connected to the first base through one of its two ends and is connected to the second base through the other of its two ends, and each mesh element is configured to undergo elastic bias of one of its two ends toward the other of its two ends when the force has a value within a range exceeding the limit value.

[0032] Furthermore, the invention relates to an aircraft structure comprising at least one damping system as defined above, each damping system being configured to absorb at least a portion of the forces exerted on the structure.

[0033] According to another advantageous aspect of the invention, the structure comprises the feature that the damping system forms a spacer connecting at least two structural elements fixed relative to each other.

[0034] Furthermore, the invention relates to an aircraft comprising a structure as defined above. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will be better understood using the following description, which is given by way of non-limiting example only and is made with reference to the accompanying drawings, in which:

[0036] Figure 1 is a perspective view of a first embodiment of a damping system according to the present invention;

[0037] Figure 2 is a three-dimensional image of a partition wall in which Figure 1 Damping system;

[0038] Figure 3 yes Figure 1 A perspective view of a portion of the damping system cut along a plane perpendicular to the longitudinal axis of the damping system;

[0039] Figure 4 is a perspective view of a second embodiment of a damping system according to the present invention, wherein some bending members of the damping system are shown in dotted lines;

[0040] Figure 5 is a perspective view of a third embodiment of a damping system according to the present invention;

[0041] Figure 6 is a perspective view of a fourth embodiment of a damping system according to the present invention;

[0042] Figure 7 yes Figure 6 A perspective view of a portion of the damping system cut along a plane perpendicular to the longitudinal axis of the damping system; and

[0043] Figure 8 is a cross-sectional view of a fifth embodiment of a damping system according to the invention in a plane containing the longitudinal axis of the damping system and passing through two beams of the damping system. DETAILED DESCRIPTION

[0044] The damping system 4 according to the invention is Figures 1 to 3 Shown in.

[0045] The damping system 4 is intended to be integrated in a structure 2, in particular an aircraft structure. For example, the structure 2 is a floor structure or Figure 2 The partition wall shown in .

[0046] In the structure 2, the damping system 4 is configured to absorb at least part of the forces exerted on the structure 2. For example, the damping system 4 forms a spacer of the structure 2 connecting at least two structural elements 6 of the structure 2 fixed relative to each other, such as crosspieces 7.

[0047] The damping system 4 extends along a respective longitudinal axis XX.

[0048] The damping system 4 comprises a first base 8 , a second base 10 , a primary damper device 12 and a secondary damper device 14 .

[0049] The first base 8 and the second base 10 are suitable for allowing the fastening of the damping system 4 to the structural element 6. In particular, during the implementation of the damping system 4, and as Figure 2 As shown in , each of the first base 8 and the second base 10 is fastened to a respective structural element 6 of the structure 2 .

[0050] The first base 8 and the second base 10 are arranged at a distance from each other along the longitudinal axis XX, in particular, as will emerge from the following description, held at a distance from each other by a primary damper device 12 and a secondary damper device 14 .

[0051] The primary damper device 12 and the secondary damper device 14 which will now be described are configured such that, when the damping system 4 is stationary, the stiffness of the primary damper device 12 along the longitudinal axis XX is greater than the stiffness of the secondary damper device 14 along the longitudinal axis XX.

[0052] The main damper device 12 comprises at least one beam 16. For example, the main damper device 12 comprises four beams 16.

[0053] Each beam 16 extends along a longitudinal axis XX.

[0054] Each beam 16 comprises two opposite ends 18. Each beam 16 is connected to the first base 8 by one of its two ends 18 and to the second base 10 by the other of its two ends 18.

[0055] The end 18 of the beam 16 along the longitudinal axis and attached to the first base 8 forms the first end of the main damper device 12. The end 18 of the beam 16 along the longitudinal axis and attached to the second base 10 forms the second end of the main damper device 12.

[0056] Preferably, each beam 16 is solid. This is advantageous when compressive forces are applied along the longitudinal axis XX of the damping system 4, since a larger part of the forces is always borne by the beam 16, since the amount of material of each beam 16 section in its cross-sectional plane perpendicular to the longitudinal axis XX is higher.

[0057] For example, each beam 16 is a solid tube having a circular cross-section.

[0058] The beams 16 are dimensioned so that each beam 16 undergoes a compressive deformation when a force applied to the damping system 4 to push the first base 8 along the longitudinal axis XX towards the second base 10 has a value less than a predetermined limit value. Furthermore, the beams 16 are dimensioned so that each beam 16 undergoes a buckling when this force has a value greater than or equal to the limit value.

[0059] The force applied to the damping system 4 to push the first base 8 along the longitudinal axis XX towards the second base 10 will be referred to as “longitudinal force”.

[0060] The secondary damper device 14 comprises at least one flexure member 20 .

[0061] Preferably, the secondary damper device 14 comprises a plurality of curved members 20 regularly distributed around the longitudinal axis XX.

[0062] For example, the secondary damper device 14 includes sixteen flexure members 20 .

[0063] Each flexure 20 is curved. Preferably, each flexure 20 extends in a plane containing the longitudinal axis XX.

[0064] Each bending member 20 includes two opposite ends 22. Each bending member 20 is fixed to the first base 8 by one of its two ends 22, and is fixed to the second base 10 by the other of its two ends 22.

[0065] The end 22 of the curved member 20 located on the same side along the longitudinal axis and attached to the first base 8 forms the first end of the secondary damper device 14. The end 22 of the curved member 20 located on the same side along the longitudinal axis and attached to the second base 10 forms the second end of the secondary damper device 14.

[0066] Preferably, each flexure 20 is hollow. This is beneficial in that, during the application of a bending force on the flexure 20 tending to bring the two ends 22 of the flexure 20 closer together, the hollow flexure 20 is able to dissipate energy substantially equal to the energy dissipated by a solid flexure of the same size, while being lighter. This is because the central portion of a solid flexure dissipates substantially no energy under the same conditions.

[0067] For example, each curved member 20 is a hollow curved cylindrical body having a circular cross section.

[0068] Preferably, the beam 16 and the flexure 20 are arranged such that the beam 16 is radially closer to the longitudinal axis XX than the flexure 20 .

[0069] For example, the flexures 20 are regularly arranged around the beam 16. Specifically, as shown in Figure 3, the concave surface 21 of each flexure 20 is oriented towards the longitudinal axis XX.

[0070] Furthermore, the dimensions of the flexure members 20 are designed so that each flexure member 20 undergoes elastic deflection when the longitudinal force has a value within a range exceeding the above-mentioned limit value.

[0071] The beam 16 arranged to be subjected to compression has a stiffness greater than the stiffness of the flexure member 20 arranged to be subjected to flexure. This provides the primary damper device 12 with a stiffness greater than the stiffness of the secondary damper device 14.

[0072] As a non-limiting example, each of the first base 8, the second base 10, the primary damper device 12 and the secondary damper device 14 is made of titanium, such as an alloy commonly referred to as "Titanium TA6V", which includes titanium, up to 7% aluminum, up to 4.5% vanadium and possibly small amounts of carbon, iron, oxygen and nitrogen.

[0073] In another example, each of the first base 8, the second base 10, the primary damper device 12, and the secondary damper device 14 is made of aluminum.

[0074] The first base 8, the second base 10, the primary damper arrangement 12 and the secondary damper arrangement 14 are preferably integral, for example jointly manufactured by additive manufacturing.

[0075] Alternatively, the primary damper device 12 and the secondary damper device 14 are attached to the first base portion 8 and the second base portion 10 by welding or any other known attachment method.

[0076] By way of example, at rest, the assembly formed by the primary damper device 12 and the secondary damper device 14 has an extension along the longitudinal axis of the order of XX 100 mm (millimeters), and the damping system 4 has an extension along the longitudinal axis of the order of XX 200 mm. In this case, the damping system 4 can be dimensioned so that the primary damper device 12 can withstand longitudinal forces up to a limit value of about 90 kN (kilonewtons) before the beam 16 undergoes buckling. In addition, the flexure member 20 can support an additional longitudinal force of 20 kN during its deformation.

[0077] The operation of the damping system 4 will now be described.

[0078] The longitudinal force applied to the damping system 4 pushes the first base 8 towards the second base 10 .

[0079] As long as the value of the longitudinal force is less than the limit value, the primary damper device 12, in particular the beam 16, bears most of the force and the stiffness of the primary damper device 12 is greater than the stiffness of the secondary damper device 14. In this case, the beam 16 remains in a compressed state. The deflection of the flexure member 20 is negligible for the shape of the flexure member 20 at rest.

[0080] If the value of the force reaches a limit value, the beam 16 undergoes buckling and dissipates part of the energy associated with the longitudinal force exerted on the damping system 4. Moreover, due to the buckling, the beam 16 is no longer able to withstand the longitudinal force. In this case, the flexural member 20 bends and withstands the force exerted on the damping system 4 and thus dissipates an additional part of the energy associated with the longitudinal force, in particular by elastic deformation.

[0081] It is conceivable that for longitudinal forces of even greater magnitudes, the flexure member 20 undergoes plastic deformation.

[0082] Further embodiments of the damping system according to the invention will now be described. Figures 1 to 3 The damping system of 4 is different, the rest of the features are similar.

[0083] Figure 4 The damping system 204 and Figures 1 to 3 The damping system 4 of the embodiment of the present invention is different in that the secondary damper device 214 comprises at least one curved member 220, which comprises two arched portions 224 having concave surfaces 221 oriented oppositely relative to each other. For example, one of the two arched portions 224 is arranged on the longitudinal axis side and has a concave surface 221 facing away from the longitudinal axis XX, while the other of the two arched portions 224 is arranged on the opposite opposite side and has a concave surface 221 oriented toward the longitudinal axis XX.

[0084] Each arched portion 224 includes two opposite ends 228. The ends 228 of the two arched portions 224 located on the same side in the longitudinal direction are connected to each other to form the end 222 of the curved member 220.

[0085] In this Figure 4 In FIG. 2 , some of the arched members 220 have been shown in dotted lines to give the drawing a better readability and in particular to allow a better visualization of the arched portions 224 .

[0086] Figure 5 The damping system 304 and Figures 1 to 3 The damping system 4 of FIG. 304 differs in that the secondary damper device 314 of the damping system 304 comprises a single flexure member 320. In this case, the flexure member 320 has a circular symmetry about the longitudinal axis XX.

[0087] Figure 6 and Figure 7 The damping system 404 and Figures 1 to 3 The damping system 4 of FIG. 4 is different in that each curved member 420 of the secondary damper device 414 comprises a damping member 431 . Each member 431 comprises a straight portion 430 and a corresponding plurality of hoops 432 .

[0088] The straight portion 430 corresponds to, for example, a middle portion of the corresponding curved member 420 .

[0089] The straight portion 430 includes two opposite end portions 434 that are attached to corresponding curved members 420 .

[0090] For example, the straight portion 430 is formed by a plurality of straight segments 435 extending along the longitudinal axis XX.

[0091] In addition, each hoop 432 includes two opposite ends 436, and each end 436 of each hoop 432 is attached to a corresponding end 434 of the straight portion 430, so that the damping member 431 has the same Figures 1 to 3 The geometry of the damping system 4 is similar to the geometry.

[0092] Alternatively, the damping member 431 has Figure 4 The damping system 204 or Figure 5 The geometry of the damping system 304 may be similar to a geometry of the TEFLON® or any other suitable geometry.

[0093] More generally, in certain embodiments of the invention, the damping member 431 has a geometry such that it comprises a primary damper device and a secondary damper device, the primary damper device having a stiffness greater than that of the secondary damper device along the longitudinal axis XX.

[0094] Figure 8The damping system 504 and Figures 1 to 3 The damping system 4 is different in that the secondary damper device 514 does not include a bending member, but includes at least one mesh element 540 having a three-dimensional lattice structure.

[0095] The mesh element 540 includes two opposing end portions 542 , 544 , each of which is connected to one of the first base portion 508 and the second base portion 510 .

[0096] Furthermore, the damping system 504 is configured such that during buckling of the beam 516 of the main damper device 512 , each mesh member 540 is pushed from one of its two ends 542 , 544 towards the other of its two ends 542 , 544 , resulting in elastic deformation of the mesh element 540 .

[0097] For example, the mesh element 540 generally defines a hollow cylindrical body extending along the longitudinal axis XX and arranged between the first base 508 and the second base 510. In this case, the hollow cylindrical mesh element radially surrounds the beam 516.

[0098] According to an embodiment of the damping system of the invention (not shown), at least one flexure 20 is arranged such that the concave surface 21 of the flexure 20 is oriented away from the longitudinal axis XX.

[0099] According to an embodiment of the damping system according to the invention (not shown), the flexure 20 is connected to the first base 8 and to the second base 10 without attachment, and the secondary damper device 14 is movable along the longitudinal axis XX.

[0100] More specifically, the ends 22 of the flexures 20 closest to the first base 8 are attached together to form a first ring. In addition, the ends 22 of the flexures 20 closest to the second base 10 are attached together to form a second ring. Each of the first and second rings radially surrounds the beam 16.

[0101] Furthermore, each of the first base 8 and the second base 10 comprises a stop intended to limit the displacement of the secondary damper device 14 in translation along the longitudinal axis XX.

[0102] In this case, the secondary damper device 14 is dimensioned so that when the beam 16 is subjected to buckling, the first base 8 contacts the first ring and the second base 10 contacts the second ring to transfer the force applied to the bases 8, 10 to the flexure member 20. The flexure member 20 then bends to absorb at least a portion of the energy provided by the longitudinal force.

Claims

1. A structure (2) for an aircraft, the structure (2) comprising at least one damping system (4; 204; 304; 404; 504), Each damping system (4; 204; 304； 404； 504) extends along a longitudinal axis (XX) and comprises: first bases (8;) arranged at a distance from each other along the longitudinal axis (XX); 508) and a second base (10; 510); A main damper device (12; 512), the main damper device (12; 512) comprising at least one beam (16; 516), each beam (16; 516) extending along the longitudinal axis (XX), each beam (16; 516) comprising two opposite ends (18) and being attached to the first base (8; 508) by one of its two ends (18) and to the second base (10; 510) by the other of its two ends (18); A secondary damper device (14; 214; 314; 414; 514), the secondary damper device (14; 214; 314; 414; 514) comprising two opposite ends, the secondary damper device (14; 214; 314; 414; 514) being connected to the first base (8; 508) by one of its two ends and to the second base (10; 510) by the other of its two ends; The damping system (4; 204; 304; 404; 504) is configured such that: When stationary, the stiffness of the primary damper device (12; 512) along the longitudinal axis (XX) is greater than the stiffness of the secondary damper device (14; 214; 314; 414; 514) along the longitudinal axis (XX); each beam (16; 516) is maintained in a compressed state when a force applied to the damping system (4; 204; 304; 404; 504) to push the first base (8; 508) towards the second base (10; 510) has a value less than a predetermined limit value; and When said force has a value greater than or equal to said limit value, each beam (16; 516) undergoes buckling and the secondary damper device (14; 514) undergoes elastic deformation, Each damping system (4; 204; 304; 404; 504) is configured to absorb at least a portion of the forces exerted on the structure (2).

2. The structure (2) according to claim 1, wherein: The secondary damper device (14; 214; 314; 414) comprises at least one bending member (20; 220; 320; 420), each bending member (20; 220; 320; 420) comprising two opposite ends (22; 222), each bending member (20; 220; 320; 420) being connected to the first base (8) via one of its two ends (22; 222) and to the second base (10) via the other of its two ends (22; 222), each bending member (20; 220; 320; 420) being configured to undergo elastic bending when the force has a value within a range exceeding a limit value.

3. The structure (2) according to claim 2, wherein: Each flexure (20; 220; 320; 420) is hollow and / or each beam (16) is solid.

4. The structure (2) according to claim 2 or 3, wherein: Each beam (16) is radially closer to the longitudinal axis (XX) than each curved member (20; 220; 320; 420).

5. The structure (2) according to claim 2 or 3, wherein: At least one curved member (204) includes two arched portions (224), each of the two arched portions (224) includes two opposite ends (228), the two ends (222) of each curved member (220) are respectively formed by connecting the two corresponding ends (228) of the two arched portions (224), and the two arched portions (224) each have a concave surface (221), and the concave surfaces (221) of the two arched portions (224) are opposite to each other.

6. Structure (2) according to claim 2 or 3, comprising a single curved member (320) having a circular symmetry about the longitudinal axis (XX).

7. The structure (2) according to claim 2 or 3, wherein: At least one curved member (420) comprises a straight portion (430) extending along the longitudinal axis (XX) and a plurality of hoops (432), the straight portion (430) comprising two opposite ends (434), each hoop (432) comprising two opposite ends (436), each of the two ends (436) of each hoop (432) being attached to a corresponding end (434) of the straight portion (430).

8. The structure (2) according to claim 1, wherein: The secondary damper device (514) comprises at least one mesh element (540), each mesh element having a three-dimensional lattice structure, each mesh element (540) comprising two opposite ends (542, 544), each mesh element being connected to the first base (508) via one of its two ends (542, 544) and connected to the second base (510) via the other of its two ends (544, 542), Each mesh element (540) is configured to undergo elastic biasing of one of its two ends toward the other of its two ends when the force has a value within a range exceeding the limit value.

9. The structure (2) according to any one of claims 1 to 3 and 8, wherein: The damping system (4; 204; 304; 404; 504) forms a spacer connecting at least two structural elements fixed relative to each other.

10. An aircraft comprising a structure (2) according to any one of claims 1 to 9.

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