Device for aircraft modal test and test method

Abstract

The invention relates to a device for an aircraft modal test and a test method, and relates to the technical field of aerospace engineering test equipment. The upper end of the elastic suspension mechanism is connected with the test bracket, and the lower end of the elastic suspension mechanism is connected to a designed position on the to-be-tested piece to suspend the to-be-tested piece; and the loading mechanism is connected with the test bracket and is used for being connected with a to-be-tested piece so as to apply a load to the to-be-tested piece. Before a test is started, a loading mechanism and an elastic suspension mechanism are connected to a to-be-tested piece; starting the elastic suspension mechanism to suspend the to-be-tested piece; and starting the loading mechanism, adjusting the loading load to be within the allowance range of the design value, keeping the to-be-tested piece horizontal, and carrying out the test. According to the test device and method provided by the invention, a modal + overload composite mechanical environment test can be realized, the overload state of an aircraft in flight can be simulated more approximately, and more accurate missile body structure modal parameters can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of aerospace engineering test equipment, and particularly relates to a device and a test method for aircraft modal tests. Background Art

[0002] In the process of aerospace product research and development, aircraft modal tests are an important way to obtain the inherent vibration characteristics and modal parameters of aircraft structures, and have now become an essential ground environment test item.

[0003] In the prior art, current aircraft modal tests are usually modal tests in a state where the projectile body is horizontally freely suspended. Generally, the aircraft is horizontally suspended through two suspension points to simulate the free state of the aircraft, and modal parameter tests are carried out in this state.

[0004] However, there are overload loads during the actual flight of the aircraft. Under this load, the structural connection performance of the aircraft may change, resulting in a change in modal parameters. The existing aircraft modal tests are difficult to simulate this overload environment. Therefore, there is a "difference between ground and space" in the obtained modal parameters, and there is a problem that it is difficult to obtain accurate modal parameters. Summary of the Invention

[0005] The present application provides a device and a test method for aircraft modal tests, which can solve the problem that in the prior art, there are overload loads during the actual flight of the aircraft. Under this load, the structural connection performance of the aircraft may change, resulting in a change in modal parameters. The existing aircraft modal tests are difficult to simulate this overload environment. Therefore, there is a "difference between ground and space" in the obtained modal parameters, and there is a problem that it is difficult to obtain accurate modal parameters.

[0006] In a first aspect, an embodiment of the present application provides a device for aircraft modal tests, which includes:

[0007] A test bracket;

[0008] An elastic suspension mechanism, the upper end of which is connected to the test bracket, and the lower end is used to be connected to a designed position on the test piece to suspend the test piece;

[0009] A loading mechanism, which is connected to the test bracket and is used to be connected to the test piece to apply a load to the test piece.

[0010] In an implementation manner, the elastic suspension mechanism includes two spaced elastic suspension units, the loading mechanism includes at least one elastic loading unit, and both the elastic suspension unit and the elastic loading unit include:

[0011] A connecting band, which is used to wrap around the test piece;

[0012] A force-measuring connection component, one end of which is connected to the connection strap;

[0013] A driving member, which is connected to the test support and the other end of the force-measuring connection component, and is used to adjust the magnitude of the loading force of the force-measuring connection component.

[0014] In one embodiment, the force-measuring connection component includes:

[0015] An elastic rubber rope, one end of which is connected to the driving member;

[0016] A tension sensor, the suspension end of which is connected to the other end of the elastic rubber rope;

[0017] A suspension rope, one end of which is connected to the force-measuring end of the tension sensor, and the other end of the suspension rope is connected to the connection strap.

[0018] In one embodiment, the driving member is detachably connected to the test support.

[0019] In one embodiment, the loading mechanism further includes a tension deflection assembly, the tension deflection assembly includes two fixed pulleys, the two fixed pulleys are arranged on the test support, the suspension rope passes through the two fixed pulleys, and is used to be connected to the connection strap to adjust the application direction of the loading load.

[0020] In one embodiment, it further includes a baffle assembly, the baffle assembly includes a plurality of baffles, and the plurality of baffles are arranged circumferentially along the test piece to limit the axial displacement of the test piece.

[0021] In a second aspect, the embodiment of the present application further provides a test method for a device for an aircraft modal test, which is implemented by using the above-mentioned device for an aircraft modal test, and includes:

[0022] Connect a loading mechanism and an elastic suspension mechanism to the test piece;

[0023] Start the elastic suspension mechanism to suspend the test piece;

[0024] Start the loading mechanism, adjust the loading load to within the allowable range of the design value, and keep the test piece horizontal for testing.

[0025] In one embodiment, before connecting the loading mechanism and the elastic suspension mechanism to the test piece, it further includes:

[0026] Determine the action direction, action position and load magnitude of the load applied by the loading mechanism;

[0027] Determine the suspension force of the elastic suspension mechanism according to the suspension point of the elastic suspension mechanism, the acting direction, acting position and load magnitude of the load applied by the loading mechanism.

[0028] Select the zero position length of the elastic rubber rope according to the suspension force of the elastic suspension mechanism, the load magnitude of the load applied by the loading mechanism, and the suspension height of the test piece to be tested.

[0029] Determine the equivalent stiffness of the modal test device according to the suspension force of the elastic suspension mechanism, the load magnitude of the load applied by the loading mechanism, the suspension height of the test piece to be tested, the length of the suspension rope, and the zero position length of the elastic rubber rope.

[0030] In one embodiment, after determining the equivalent stiffness of the modal test device, it further includes:

[0031] Judge whether the system frequency meets the requirements of the modal test according to the equivalent stiffness of the modal test device;

[0032] If not, adjust the zero position length or stiffness of the elastic rubber rope until the requirements of the modal test are met.

[0033] In one embodiment, when the acting direction of the applied load is horizontal, the loading mechanism includes two elastic loading units with opposite acting directions and the same applied load. According to the formula: Determine the equivalent stiffness of the modal test device;

[0034] Wherein, K is the equivalent stiffness of the modal test device, k 1 is the stiffness of one of the elastic rubber ropes in the elastic suspension mechanism, k 2 is the stiffness of the other elastic rubber rope in the elastic suspension mechanism, k 11 is the stiffness of one of the elastic rubber ropes in the loading mechanism, k 22 is the stiffness of the other elastic rubber rope in the loading mechanism, l 11 is the deformed length of one of the elastic rubber ropes in the loading mechanism, l 22 is the deformed length of the other elastic rubber rope in the loading mechanism, l 110 is the zero position length of one of the elastic rubber ropes in the loading mechanism, l 220 is the zero position length of the other elastic rubber rope in the loading mechanism, and Δx is the displacement of the test piece to be tested under the exciting force during the test.

[0035] The beneficial effects brought by the technical solutions provided in the embodiments of the present application include:

[0036] When using the device for aircraft modal testing, connect the upper end of the elastic suspension mechanism to the test bracket, and the lower end is used to connect to the designed position on the test piece to suspend the test piece. One end of the loading mechanism is connected to the test bracket, and the other end is connected to the test piece to apply a load to the test piece. Before the test starts, connect the loading mechanism and the elastic suspension mechanism to the test piece; start the elastic suspension mechanism to suspend the test piece; start the loading mechanism, adjust the loading load within the allowable range of the designed value, and keep the test piece horizontal to conduct the test. Since the loading load can be adjusted through the loading mechanism, and the application of an overload load can be simulated through the loading mechanism, a "modal + overload" combined mechanical environment test can be achieved, more closely simulating the overload state of the aircraft during flight, obtaining more accurate modal parameters of the projectile structure, and solving the problem that in the prior art, there is an overload load during the actual flight of the aircraft, and the structural connection performance of the aircraft may change under this load, resulting in a change in the modal parameters. The existing aircraft modal tests are difficult to simulate such an overload environment, so there is a "difference between ground and air" in the obtained modal parameters, and it is difficult to obtain accurate modal parameters. Description of the Drawings

[0037] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0038] Figure 1 Structural schematic diagram of an embodiment of a device for aircraft modal testing according to the present invention.

[0039] Figure 2 Schematic diagram of the upward force when applying a load in an embodiment of a device for aircraft modal testing according to the present invention.

[0040] Figure 3 Structural schematic diagram of an embodiment of a device for aircraft modal testing according to the present invention including a tension turning component.

[0041] Figure 4 Schematic diagram of the downward force when applying a load in an embodiment of a device for aircraft modal testing according to the present invention.

[0042] Figure 5 Schematic diagram of the horizontal force when applying a load in an embodiment of a device for aircraft modal testing according to the present invention.

[0043] Figure 6 Schematic diagram of the force on the connecting strap in an embodiment of a device for aircraft modal testing according to the present invention.

[0044] In the figure: 1. Test support; 2. Elastic suspension mechanism; 3. Loading mechanism; 231. Connecting belt; 232. Force-measuring connection assembly; 2321. Elastic rubber cord; 2322. Tensile force sensor; 2323. Suspension cord; 233. Driving member; 31. Tensile force deflection assembly; 311. Fixed pulley; 4. Specimen to be tested; 5. Baffle assembly; 51. Baffle. Specific implementation manner

[0045] In order to enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0046] The embodiment of this application provides a device and a test method for aircraft modal testing, which can solve the problem that in the prior art, there is an overload load during the actual flight of an aircraft, and the structural connection performance of the aircraft may change under this load, resulting in a change in modal parameters. The existing aircraft modal tests are difficult to simulate such an overload environment, so there is a "difference between ground and air" in the obtained modal parameters, and it is difficult to obtain accurate modal parameters.

[0047] As Figure 1 and Figure 3 shown, on the one hand, this application provides a device for aircraft modal testing, which includes:

[0048] Test support 1;

[0049] Elastic suspension mechanism 2, whose upper end is connected to the test support 1, and the lower end is used to be connected to the designed position on the specimen to be tested 4 to suspend the specimen to be tested 4;

[0050] Loading mechanism 3, which is connected to the test support 1 and is used to be connected to the specimen to be tested 4 to apply a load to the specimen to be tested 4.

[0051] When using the device for aircraft modal testing, connect the upper end of the elastic suspension mechanism 2 to the test support 1, and the lower end is used to connect to the designed position on the test piece 4 to suspend the test piece 4. One end of the loading mechanism 3 is connected to the test support 1, and the other end is connected to the test piece 4 to apply a load to the test piece 4. Before the test starts, connect the loading mechanism 3 and the elastic suspension mechanism 2 to the test piece 4; start the elastic suspension mechanism 2 to suspend the test piece 4; start the loading mechanism 3, adjust the loading load to within the allowable range of the designed value, and keep the test piece 4 horizontal for the test. Since the loading load can be adjusted through the loading mechanism 3, and the application of an overload load can be simulated through the loading mechanism 3, a "modal + overload" combined mechanical environment test can be achieved, more closely simulating the overload state of the aircraft during flight, obtaining more accurate modal parameters of the projectile structure, and solving the problem that in the prior art, there is an overload load during the actual flight of the aircraft, and the structural connection performance of the aircraft may change under this load, resulting in a change in the modal parameters. The existing aircraft modal tests are difficult to simulate such an overload environment, so there is a "difference between ground and air" in the obtained modal parameters, and it is difficult to obtain accurate modal parameters.

[0052] In this example, the test piece 4 is an aircraft of the rocket type. The device for aircraft modal testing also has the advantages of high flexibility, low space requirements, conventional equipment, low cost, high safety, and simple operation.

[0053] As Figure 1 and Figure 3 shown, in some alternative embodiments, the elastic suspension mechanism 2 includes two elastically suspended units arranged at intervals, and the loading mechanism 3 includes at least one elastic loading unit. Both the elastically suspended unit and the elastic loading unit include:

[0054] A connecting strap 231, which is used to wrap around the test piece 4;

[0055] A force-measuring connection component 232, one end of which is connected to the connecting strap 231;

[0056] A driving member 233, which is connected to the test support 1 and the other end of the force-measuring connection component 232, and is used to adjust the magnitude of the loading force of the force-measuring connection component 232.

[0057] In this embodiment, the structures of the elastic suspension mechanism 2 and the loading mechanism 3 are specifically described. The elastic suspension mechanism 2 includes two spaced-apart elastic suspension units, and the loading mechanism 3 includes at least one elastic loading unit. Both the elastic suspension unit and the elastic loading unit include a connecting strap 231, a force-measuring connection assembly 232, and a driving member 233. Among them, the connecting strap 231 is used to wrap around the test piece 4. One end of the force-measuring connection assembly 232 is connected to the connecting strap 231, and the driving member 233 is connected to the test bracket 1 and the other end of the force-measuring connection assembly 232, and is used to adjust the loading force of the force-measuring connection assembly 232. The structure is simple and convenient to use.

[0058] As Figure 1 and Figure 3 shown, in some alternative embodiments, the force-measuring connection assembly 232 includes:

[0059] An elastic rubber cord 2321, one end of which is connected to the driving member 233;

[0060] A tension sensor 2322, the hanging end of which is connected to the other end of the elastic rubber cord 2321;

[0061] A suspension cord 2323, one end of which is connected to the force-measuring end of the tension sensor 2322, and the other end of the suspension cord 2323 is connected to the connecting strap 231.

[0062] In this embodiment, the specific structure of the force-measuring connection assembly 232 is described. The force-measuring connection assembly 232 includes an elastic rubber cord 2321, a tension sensor 2322, and a suspension cord 2323. Among them, one end of the elastic rubber cord 2321 is connected to the driving member 233, the hanging end of the tension sensor 2322 is connected to the other end of the elastic rubber cord 2321, one end of the suspension cord 2323 is connected to the force-measuring end of the tension sensor 2322, and the other end of the suspension cord 2323 is connected to the connecting strap 231, which can facilitate reading the acting force of the elastic suspension mechanism 2 and the loading mechanism 3 and can adjust the test load in real time.

[0063] In some alternative embodiments, the driving member 233 is detachably connected to the test bracket 1.

[0064] In this embodiment, the driving member 233 is detachably connected to the test bracket 1, and the setting position of the driving member 233 can be adjusted according to the test requirements, improving the applicability of the device for aircraft modal tests.

[0065] As Figure 3As shown, in some alternative embodiments, the loading mechanism 3 further includes a tension steering assembly 31. The tension steering assembly 31 includes two fixed pulleys 311. The two fixed pulleys 311 are arranged on the test bracket 1. The suspension rope 2323 passes through the two fixed pulleys 311 and is used to connect with the connecting strap 231 to adjust the application direction of the loading load.

[0066] In this embodiment, the loading mechanism 3 further includes a tension steering assembly 31. The tension steering assembly 31 includes two fixed pulleys 311. The two fixed pulleys 311 are arranged on the test bracket 1. The suspension rope 2323 passes through the two fixed pulleys 311 and is used to connect with the connecting strap 231 to adjust the application direction of the loading load. This is more efficient in utilizing the test space and can facilitate the adjustment process of the application direction of the loading load.

[0067] As Figure 1 and Figure 3 shown, in some alternative embodiments, it further includes a baffle assembly 5. The baffle assembly 5 includes a plurality of baffles 51. The plurality of baffles 51 are arranged circumferentially along the test piece 4 to limit the axial displacement of the test piece 4.

[0068] In this embodiment, the device for aircraft modal testing further includes a baffle assembly 5. The baffle assembly 5 includes a plurality of baffles 51. The plurality of baffles 51 are arranged circumferentially along the test piece 4 to limit the axial displacement of the test piece 4, prevent the test piece 4 from detaching, and improve the safety of the device for aircraft modal testing.

[0069] As Figure 6 shown, in this example, a baffle assembly 5 is provided on each connecting strap 231. The test piece 4 will not slide only when the following balance condition is met:

[0070] It is derived that F 5 = F 1 (sinθ - μcosθ);

[0071] Wherein, F 4 is the support force of the test piece 4 on the connecting strap 231, f is the frictional force between the connecting strap 231 and the test piece 4, μ is the friction coefficient between the connecting strap 231 and the test piece 4, θ is the angle between the generatrix of the conical part of the test piece 4 and the horizontal plane, and F 5 is the reaction force received by the baffle 51.

[0072] When μ >> tanθ, the baffle 51 is not stressed, and the connecting strap 231 can prevent sliding only by relying on the frictional force; when μ < tanθ or they are close, the baffle 51 needs to provide a certain support force to prevent the connecting strap 231 from sliding. For the mechanical environment of the baffle 51, it bears an equal and opposite force to F5 The pressure at this time requires that the baffle 51 does not undergo large flexural deformation and has a certain safety factor. It is possible to install 5 to 7 baffles at the lower surface position of the test piece 4 to further improve safety. If the front suspension point is located on the cylindrical surface part of the test piece 4, the baffle 51 can be not installed.

[0073] Such as Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 shown, on the other hand, the present application also provides a test method for a device for aircraft modal testing, which is implemented by using the above-mentioned device for aircraft modal testing, including:

[0074] Connect the loading mechanism 3 and the elastic suspension mechanism 2 to the test piece 4 to be tested;

[0075] Start the elastic suspension mechanism 2 to suspend the test piece 4 to be tested;

[0076] Start the loading mechanism 3, adjust the loading load within the allowable range of the design value, and keep the test piece 4 horizontal for testing.

[0077] Such as Figure 2 , Figure 4 and Figure 5 shown, in some alternative embodiments, before connecting the loading mechanism 3 and the elastic suspension mechanism 2 to the test piece 4 to be tested, it further includes:

[0078] Determine the acting direction, acting position, and load magnitude of the load applied by the loading mechanism 3;

[0079] According to the suspension point of the elastic suspension mechanism 2 and the acting direction, acting position, and load magnitude of the load applied by the loading mechanism 3, determine the suspension acting force of the elastic suspension mechanism 2;

[0080] According to the suspension acting force of the elastic suspension mechanism 2, the load magnitude of the load applied by the loading mechanism 3, and the suspension height of the test piece 4 to be tested, select the zero position length of the elastic rubber rope 2321;

[0081] According to the suspension acting force of the elastic suspension mechanism 2, the load magnitude of the load applied by the loading mechanism 3, the suspension height of the test piece 4 to be tested, the length of the suspension rope 2323, and the zero position length of the elastic rubber rope 2321, determine the equivalent stiffness of the modal test device.

[0082] In this embodiment, before connecting the loading mechanism 3 and the elastic suspension mechanism 2 to the test piece 4 to be tested, it is also necessary to determine the acting direction, acting position, and load magnitude of the load applied by the loading mechanism 3, and determine the suspension force of the elastic suspension mechanism 2 based on the suspension points of the elastic suspension mechanism 2 and the acting direction, acting position, and load magnitude of the load applied by the loading mechanism 3. Then, based on the suspension force of the elastic suspension mechanism 2, the load magnitude of the load applied by the loading mechanism 3, and the suspension height of the test piece 4 to be tested, select the zero position length of the elastic rubber rope 2321. Finally, based on the suspension force of the elastic suspension mechanism 2, the load magnitude of the load applied by the loading mechanism 3, the suspension height of the test piece 4 to be tested, the length of the suspension rope 2323, and the zero position length of the elastic rubber rope 2321, determine the stiffness of the elastic rubber rope 2321. The deformed length of the elastic rubber rope 2321 can be obtained based on the suspension height of the test piece 4 to be tested, the length of the suspension rope 2323, and the zero position length of the elastic rubber rope 2321. Then, based on the stiffness of the elastic rubber rope 2321, the zero position length of the elastic rubber rope 2321, and the deformed length of the elastic rubber rope 2321, determine the equivalent stiffness of the modal test device.

[0083] In this example, the acting direction, acting position, and load magnitude of the load applied by the loading mechanism 3 are determined based on the bending moment at a certain section in the flight condition. According to the formula: where X 1 is the coordinate point at the front end of the test piece 4 to be tested, is the coordinate point at the tail end of the test piece 4 to be tested, m i is the mass at the coordinate point X i and the physical meanings of the other symbols are the same as those in the following text.

[0084] In this example, after determining the suspension force of the elastic suspension mechanism 2, the stiffness of the elastic rubber rope 2321 can also be selected according to experience. Then, based on the suspension force of the elastic suspension mechanism 2, the stiffness of the elastic rubber rope 2321, and the load magnitude of the load applied by the loading mechanism 3, obtain the deformation amount of the elastic rubber rope 2321. And based on the suspension height of the test piece 4 to be tested, the length of the suspension rope 2323, and the deformation amount of the elastic rubber rope 2321, determine the zero position length of the elastic rubber rope 2321.

[0085] In some alternative embodiments, after determining the equivalent stiffness of the modal test device, it further includes:

[0086] Judge whether the system frequency meets the requirements of the modal test according to the equivalent stiffness of the modal test device;

[0087] If not, adjust the zero position length or stiffness of the elastic rubber rope 2321 until the requirements of the modal test are met.

[0088] In this embodiment, after determining the equivalent stiffness of the modal test device, it is also necessary to judge whether the system frequency meets the requirements of the modal test based on the equivalent stiffness of the modal test device. If the obtained equivalent stiffness does not meet the requirements of the system suspension frequency, adjust the zero position length or stiffness of the elastic rubber rope 2321 until the requirements of the modal test are met to ensure the safety of the test.

[0089] In this example, if the stiffness of the elastic rubber rope 2321 is selected first, the stiffness of the elastic rubber rope 2321 can be preferentially adjusted until the requirements of the modal test are met.

[0090] As Figure 2 、 Figure 4 and Figure 5 shown, in some alternative embodiments, when the acting direction of the applied load is horizontal, the loading mechanism 3 includes two elastic loading units with opposite acting directions and the same applied load. According to the formula: Determine the equivalent stiffness of the modal test device;

[0091] where K is the equivalent stiffness of the modal test device, k 1 is the stiffness of one of the elastic rubber ropes 2321 in the elastic suspension mechanism 2, k 2 is the stiffness of the other elastic rubber rope 2321 in the elastic suspension mechanism 2, k 11 is the stiffness of one of the elastic rubber ropes 2321 in the loading mechanism 3, k 22 is the stiffness of the other elastic rubber rope 2321 in the loading mechanism 3, l 11 is the deformed length of one of the elastic rubber ropes 2321 in the loading mechanism 3, l 22 is the deformed length of the other elastic rubber rope 2321 in the loading mechanism 3, l 110 is the zero position length of one of the elastic rubber ropes 2321 in the loading mechanism 3, l 220 is the zero position length of the other elastic rubber rope 2321 in the loading mechanism 3, and Δx is the displacement of the test piece 4 under the excitation force during the test.

[0092] In this embodiment, when the acting direction of the applied load is horizontal, the loading mechanism 3 includes two elastic loading units with opposite acting directions and the same applied load. According to the formula: Determine the equivalent stiffness of the modal test device; where K is the equivalent stiffness of the modal test device, k 1 is the stiffness of one of the elastic rubber ropes 2321 in the elastic suspension mechanism 2, k 2 is the stiffness of the other elastic rubber rope 2321 in the elastic suspension mechanism 2, k 11 is the stiffness of one of the elastic rubber ropes 2321 in the loading mechanism 3, k 22is the stiffness of another elastic rubber cord 2321 in the loading mechanism 3, l 11 is the deformed length of one of the elastic rubber cords 2321 in the loading mechanism 3, l 22 is the deformed length of another elastic rubber cord 2321 in the loading mechanism 3, l 110 is the zero - position length of one of the elastic rubber cords 2321 in the loading mechanism 3, l 220 is the zero - position length of another elastic rubber cord 2321 in the loading mechanism 3, Δx is the displacement of the test piece 4 under the exciting force during the test. According to the above formula, the equivalent stiffness can be obtained quickly.

[0093] In this example, when the direction of the applied load is upward, the loading mechanism 3 includes an elastic loading unit. The sum of the suspension force of the elastic suspension mechanism 2 and the force of the loading mechanism 3 providing the loading load is equal to the gravity of the test piece 4. where, F 1 is the suspension force provided by one of the elastic rubber cords 2321 in the elastic suspension mechanism 2, F 2 is the suspension force provided by the other elastic rubber cord 2321 in the elastic suspension mechanism 2, F 3 is the force of the elastic rubber cord 2321 in the loading mechanism 3 providing the loading load, G is the gravity of the test piece 4. is the acting point of one of the elastic rubber cords 2321 in the elastic suspension mechanism 2. is the acting point of the other elastic rubber cord 2321 in the elastic suspension mechanism 2. is the acting point of the elastic rubber cord 2321 in the loading mechanism 3, X g is the centroid point of the test piece 4. The equivalent stiffness is equal to the sum of the stiffnesses of the elastic suspension mechanism 2 and the loading mechanism 3.

[0094] When the direction of the applied load is downward, the loading mechanism 3 includes an elastic loading unit. The suspension force of the elastic suspension mechanism 2 is equal to the sum of the force of the loading mechanism 3 providing the loading load and the gravity of the test piece 4. where, the physical meanings of the symbols are the same as above. The equivalent stiffness is equal to the sum of the stiffnesses of the elastic suspension mechanism 2 and the loading mechanism 3.

[0095] In this example, when the direction of the applied load is horizontal, the loading mechanism 3 includes two elastic loading units with opposite acting directions and the same applied load, satisfying the following equilibrium conditions:

[0096]

[0097] where, l 1 is the deformed length of one of the elastic rubber cords 2321 in the elastic suspension mechanism 2, l 2is the deformed length of another elastic rubber cord 2321 in the elastic suspension mechanism 2, l 10 is the zero-length of one of the elastic rubber cords 2321 in the elastic suspension mechanism 2, l 20 is the zero-length of another elastic rubber cord 2321 in the elastic suspension mechanism 2, F 11 is the acting force that provides the loading load for one of the elastic rubber cords 2321 in the loading mechanism 3, F 22 is the acting force that provides the loading load for another elastic rubber cord 2321 in the loading mechanism 3. The physical meanings of other symbols are the same as above.

[0098] When the test piece 4 is displaced by the exciting force, the following equilibrium conditions are satisfied:

[0099]

[0100] Among them, F 1 ’ is the suspension acting force provided when one of the elastic rubber cords 2321 in the elastic suspension mechanism 2 is displaced by the exciting force, F 2 ’ is the suspension acting force provided when another elastic rubber cord 2321 in the elastic suspension mechanism 2 is displaced by the exciting force, F 11 ’ is the acting force that provides the loading load when one of the elastic rubber cords 2321 in the loading mechanism 3 is displaced by the exciting force, F 22 ’ is the acting force that provides the loading load when another elastic rubber cord 2321 in the loading mechanism 3 is displaced by the exciting force, θ 11 is the angle between the direction of the acting force that provides the loading load when one of the elastic rubber cords 2321 in the loading mechanism 3 is displaced by the exciting force and the horizontal plane, θ 22 is the angle between the direction of the acting force that provides the loading load when another elastic rubber cord 2321 in the loading mechanism 3 is displaced by the exciting force and the horizontal plane. F is the exciting force. The physical meanings of other symbols are the same as above.

[0101] By combining the above two equations,

[0102] Since the displacement Δx caused by the exciting force is small, it can be obtained that

[0103] In summary, when using the device for aircraft modal tests, the upper end of the elastic suspension mechanism 2 is connected to the test support 1, and the lower end is used to connect to the designed position on the test piece 4 to suspend the test piece 4. One end of the loading mechanism 3 is connected to the test support 1, and the other end is connected to the test piece 4 to apply a load to the test piece 4. Before the test starts, the loading mechanism 3 and the elastic suspension mechanism 2 are connected to the test piece 4; the elastic suspension mechanism 2 is started to suspend the test piece 4; the loading mechanism 3 is started to adjust the loading load within the allowable range of the designed value and keep the test piece 4 horizontal for the test. Since the loading load can be adjusted through the loading mechanism 3 and the application of an overload load can be simulated through the loading mechanism 3, a "modal + overload" composite mechanical environment test can be achieved, more closely simulating the overload state of the aircraft during flight, obtaining more accurate modal parameters of the projectile structure, and solving the problem that in the prior art, there is an overload load during the actual flight of the aircraft, and the structural connection performance of the aircraft may change under this load, resulting in a change in the modal parameters. The existing aircraft modal tests are difficult to simulate such an overload environment, so there is a "difference between ground and air" in the obtained modal parameters, and it is difficult to obtain accurate modal parameters.

[0104] In the description of the present application, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application. Unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0105] It should be noted that in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the said element.

[0106] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A device for aircraft modal testing, characterized in that: include: Test stand (1); An elastic suspension mechanism (2), the upper end of which is connected to the test support (1), and the lower end of which is used to be connected to a designed position on the test object (4) to suspend the test object (4); A loading mechanism (3) is connected to the test support (1) and is used to connect to the test object (4) to apply a load to the test object (4).

2. The device for aircraft modal testing according to claim 1, characterized in that: The elastic suspension mechanism (2) comprises two elastic suspension units arranged at intervals, the loading mechanism (3) comprises at least one elastic loading unit, and the elastic suspension unit and the elastic loading unit both comprise: A connecting tape (231) for wrapping the test piece (4); A force measuring connection assembly (232), one end of which is connected to the connection strap (231); A driving member (233) is connected to the test bracket (1) and to the other end of the force measuring connection assembly (232) and is used to adjust the loading force of the force measuring connection assembly (232).

3. The device for aircraft modal testing according to claim 2, characterized in that: The force measuring connection assembly (232) comprises: An elastic rubber cord (2321), one end of which is connected to the driving member (233); A tension sensor (2322), the suspension end of which is connected to the other end of the elastic rubber rope (2321); A suspension rope (2323) has one end connected to the force measuring end of the tension sensor (2322), and the other end of the suspension rope (2323) is connected to the connecting strap (231).

4. The device for aircraft modal testing according to claim 3, characterized in that: The driving member (233) is detachably connected to the test bracket (1).

5. The device for aircraft modal testing according to claim 4, characterized in that: The loading mechanism (3) further comprises a tension steering assembly (31), wherein the tension steering assembly (31) comprises two fixed pulleys (311), wherein the two fixed pulleys (311) are arranged on the test stand (1), and the suspension rope (2323) passes through the two fixed pulleys (311) and is used to connect with the connecting strap (231) to adjust the direction of application of the loading load.

6. The device for aircraft modal testing according to claim 1, characterized in that: It also comprises a baffle assembly (5), wherein the baffle assembly (5) comprises a plurality of baffles (51), wherein the plurality of baffles (51) are arranged along the circumference of the test piece (4) to limit the axial displacement of the test piece (4).

7. A test method for an apparatus for aircraft modal testing, characterized in that: The method is implemented by using a device for aircraft modal testing as claimed in any one of claims 1 to 6, comprising: Connecting a loading mechanism (3) and an elastic suspension mechanism (2) to a test piece (4); Starting the elastic suspension mechanism (2) to suspend the test piece (4); The loading mechanism (3) is started, the loading load is adjusted to be within the tolerance range of the design value, and the test piece (4) is kept horizontal to carry out the test.

8. A test method for an aircraft modal test device as claimed in claim 7, characterized in that: Before connecting the loading mechanism (3) and the elastic suspension mechanism (2) to the test piece (4), the method further comprises: Determining the direction, position and magnitude of the load applied by the loading mechanism (3); Determining the suspension force of the elastic suspension mechanism (2) according to the suspension point of the elastic suspension mechanism (2) and the direction, position and magnitude of the load applied by the loading mechanism (3); The zero-position length of the elastic rubber rope (2321) is selected according to the suspension force of the elastic suspension mechanism (2), the load size of the load applied by the loading mechanism (3), and the suspension height of the test piece (4); The equivalent stiffness of the modal test device is determined based on the suspension force of the elastic suspension mechanism (2), the load size of the load applied by the loading mechanism (3), the suspension height of the test piece (4), the length of the suspension rope (2323), and the zero-position length of the elastic rubber rope (2321).

9. A test method for an aircraft modal test device as claimed in claim 8, characterized in that: After determining the equivalent stiffness of the modal test device, the method further includes: Determine whether the system frequency meets the modal test requirements based on the equivalent stiffness of the modal test device; If not, adjust the zero length or stiffness of the elastic rubber rope (2321) until the modal test requirements are met.

10. A test method for an aircraft modal test device as claimed in claim 8, characterized in that: When the direction of the applied load is horizontal, the loading mechanism (3) includes two elastic loading units with opposite directions of action and the same applied load, according to the formula: Determine the equivalent stiffness of the modal test device; Wherein, K is the equivalent stiffness of the modal test device, k1 is the stiffness of one of the elastic rubber ropes (2321) in the elastic suspension mechanism (2), k2 is the stiffness of another elastic rubber rope (2321) in the elastic suspension mechanism (2), and k 11 is the stiffness of one of the elastic rubber ropes (2321) in the loading mechanism (3), k 22 is the stiffness of another elastic rubber rope (2321) in the loading mechanism (3), l 11 is the deformed length of one of the elastic rubber ropes (2321) in the loading mechanism (3), l 22 is the deformed length of another elastic rubber rope (2321) in the loading mechanism (3), l 110 is the zero position length of one of the elastic rubber ropes (2321) in the loading mechanism (3), l 220 is the zero-position length of another elastic rubber rope (2321) in the loading mechanism (3), and Δx is the displacement of the test piece (4) subjected to the exciting force during the test.

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