An inflatable deformable wing fatigue strength testing device

Abstract

The application discloses an inflatable deformable airfoil fatigue strength testing device, and relates to the technical field of aviation structure fatigue testing. The device comprises a rack, a clamping mechanism and a force applying mechanism. The clamping mechanism comprises a guide rail and two clamping seats. The guide rail is arranged on the rack, and the two clamping seats are respectively slidably connected to the guide rail. Each clamping seat is provided with two oppositely arranged first flexible contact pieces, and a clamping gap for clamping the end of the airfoil is formed between the two first flexible contact pieces. The force applying mechanism comprises a power assembly and a force applying head. The power assembly is arranged on the rack, the force applying head is connected to the power output end of the power assembly, and the force applying head is provided with a second flexible contact piece facing the area between the two clamping seats. The above structure can effectively avoid local indentation and stress concentration caused by rigid clamping on the flexible film surface, the clamping interval can be adjusted according to different wing span sizes, different specifications of inflatable airfoil test pieces can be adapted, and the distribution characteristics of the aerodynamic load can be truly simulated.

Description

Technical Field

[0001] This invention relates to the field of fatigue testing technology for aerospace structures, and in particular to a fatigue strength testing device for an inflatable deformable wing. Background Technology

[0002] Inflatable deformable wings are lightweight, foldable, and quick to deploy, making them promising for use in small unmanned aerial vehicles (UAVs). However, during long-term service, inflatable deformable wings are susceptible to fatigue failures such as membrane tearing, stiffness reduction, and decreased airtightness due to the combined effects of alternating aerodynamic loads, air pressure fluctuations, and repeated deformation of the flexible membrane. Therefore, fatigue strength testing is crucial for their application.

[0003] Currently, most existing material testing fixtures are rigid structures, such as wedge clamps and rigid pressure plates. When using a fixed-size rigid clamping method to directly clamp a flexible thin-film wing, indentations or localized stress concentrations are easily generated at the ends, causing damage to the sample at the clamping end before effective loading. Furthermore, these methods are unsuitable for wings with different wingspans. Existing fatigue loading methods often use small-area rigid indenters, such as eccentric wheels or ordinary hydraulic cylinders. When loading a flexible membrane surface supported by air pressure using rigid point contact, the load cannot be evenly distributed across the flexible membrane surface, easily causing severe localized indentations or even non-real ruptures. In addition, traditional strain gauges are prone to detachment when the flexible membrane surface undergoes large deformations or repeated wrinkling, and single-point measurement methods cannot obtain the full-field strain distribution of the wing, making it difficult to accurately record the evolution of fatigue damage.

[0004] Therefore, there is an urgent need for a fatigue strength testing device that can perform non-destructive clamping, realistic simulation of aerodynamic load loading, and non-contact full-field deformation monitoring of inflatable deformable wings. Summary of the Invention

[0005] The purpose of this invention is to provide an inflatable deformable wing fatigue strength testing device to solve the problems existing in the prior art, and to achieve non-destructive clamping, realistic simulation of aerodynamic load loading, and non-contact full-field deformation monitoring.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides an inflatable deformable wing fatigue strength testing device, comprising a frame, a clamping mechanism, and a force application mechanism; the clamping mechanism includes a guide rail and two clamping seats; the guide rail is disposed on the frame, and the two clamping seats are slidably connected to the guide rail; each clamping seat is provided with two opposing first flexible contact members, and a clamping gap for clamping the wing tip is formed between the two first flexible contact members; the force application mechanism includes a power component and a force application head; the power component is disposed on the frame, the force application head is connected to the power output end of the power component, and the force application head is provided with a second flexible contact member facing the area between the two clamping seats.

[0007] In one embodiment, both the first flexible contact and the second flexible contact are made of polyurethane rubber.

[0008] In one embodiment, the clamping seat includes a clamping frame and an adjusting member. The clamping frame has a clamping space for accommodating the wing tip. Two first flexible contacts are disposed opposite each other in the clamping space. At least one first flexible contact is connected to the adjusting member to adjust the size of the clamping space.

[0009] As one embodiment, the clamping mechanism further includes an adjustment drive assembly, which includes a first lead screw, a drive motor, and a guide structure. The first lead screw has threaded sections with opposite directions of rotation. The two clamping seats are respectively threaded into the threaded sections with opposite directions of rotation on the first lead screw. The first lead screw is connected to the output shaft of the drive motor. The guide structure is used to limit the two clamping seats to move in opposite directions or in opposite directions.

[0010] As one embodiment, the force-applying head is strip-shaped, and the surface of the force-applying head facing the wing is a curved surface adapted to the outer contour of the wing.

[0011] In one embodiment, the power component is a servo electric cylinder, and the telescopic rod of the servo electric cylinder is the power output end.

[0012] As one embodiment, a detection module is also included, which includes a force sensor and an air chamber pressure sensor; the force sensor is disposed between the power output end and the force application head, and the air chamber pressure sensor is used to detect the air pressure inside the air chamber of the wing.

[0013] As one embodiment, the detection module further includes a DIC image acquisition camera, the lens of which is positioned facing the wing surface area between the two clamping seats.

[0014] As one embodiment, it also includes a pressure control component, which includes an air source and an inflation pipe, the inflation pipe connecting the air source and the wing air cavity.

[0015] As one embodiment, the frame further includes a support beam located above the two clamping seats, and the power assembly is fixed to the support beam.

[0016] The present invention achieves the following technical effects compared to the prior art: This invention utilizes two opposing first flexible contact elements on the clamping base to form a clamping gap, thereby effectively avoiding localized indentations and stress concentrations on the flexible membrane surface caused by rigid clamping. By sliding the two clamping bases onto the guide rail, the clamping distance can be adjusted according to different wingspan dimensions, thus adapting to inflatable wing specimens of different specifications. Furthermore, by incorporating a force-applying head with a second flexible contact element, adaptive deformation occurs upon contact with the wing surface, increasing the contact area and preventing localized membrane surface damage caused by point contact loading, thereby more realistically simulating the distribution characteristics of aerodynamic loads. Therefore, the testing device of this invention can achieve fatigue strength testing of inflatable deformable wings without causing unrealistic fatigue damage to the flexible specimen by the testing device itself. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of an inflatable deformable wing fatigue strength testing device according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a clamping frame in one embodiment of the present invention; Figure 3 This is a schematic diagram of a clamp mounting base in one embodiment of the present invention; Figure 4 This is a schematic diagram of the second lead screw in one embodiment of the present invention; Figure 5 This is a schematic diagram of the first flexible contact element in one embodiment of the present invention; Figure 6 This is a schematic diagram of an adjusting member in one embodiment of the present invention.

[0019] The components include: 1. Frame; 2. Guide rail; 3. Clamping seat; 4. First flexible contact; 5. Second flexible contact; 6. Clamping frame; 7. Adjusting component; 8. Second lead screw; 9. Drive motor; 10. Servo electric cylinder; 11. Wing air chamber; 12. Chuck mounting seat. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The purpose of this invention is to provide an inflatable deformable wing fatigue strength testing device to solve the problems existing in the prior art, and to achieve non-destructive clamping, realistic simulation of aerodynamic load loading, and non-contact full-field deformation monitoring.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] like Figures 1-6 As shown, this embodiment provides an inflatable deformable wing fatigue strength testing device, including a frame 1, a clamping mechanism, and a force application mechanism; the clamping mechanism includes a guide rail 2 and two clamping seats 3; the guide rail 2 is disposed on the frame 1, and the two clamping seats 3 are slidably connected to the guide rail 2 respectively; each clamping seat 3 is provided with two opposing first flexible contact members 4, and a clamping gap for clamping the wing tip is formed between the two first flexible contact members 4; the force application mechanism includes a power component and a force application head; the power component is disposed on the frame 1, the force application head is connected to the power output end of the power component, and the force application head is provided with a second flexible contact member 5 facing the area between the two clamping seats 3. By clamping the wing tip with the first flexible contact 4, the problems of local indentation and stress concentration caused by rigid clamping on the flexible membrane surface can be reduced; the two clamping seats 3 are slidably connected to the guide rail 2, and the clamping distance can be flexibly adjusted according to different wingspan sizes, thereby adapting to various specifications of inflatable wing test pieces; the second flexible contact 5 on the force application head can produce adaptive deformation when contacting the wing surface to increase the contact area, which can reduce the possibility of local damage to the membrane surface caused by point contact loading.

[0024] Optionally, the surface of the first flexible contact 4 is provided with anti-slip texture to enhance friction during clamping and prevent the wing from slipping during testing.

[0025] In one embodiment, both the first flexible contact 4 and the second flexible contact 5 are made of polyurethane rubber. Polyurethane rubber has excellent elasticity and wear resistance, and can generate moderate deformation during clamping and loading, which can ensure the stability of clamping and loading while avoiding damage to the flexible membrane surface.

[0026] In one embodiment, the clamping base 3 includes a clamping frame 6 and an adjusting member 7. The clamping frame 6 has a clamping space for accommodating the wing tip. Two first flexible contact members 4 are disposed opposite each other within the clamping space. At least one first flexible contact member 4 is connected to the adjusting member 7 to adjust the size of the clamping space. By adjusting the size of the clamping space through the adjusting member 7, the clamping gap can be flexibly adjusted according to the thickness of the wing tip, thereby adapting to inflatable wing specimens of different thicknesses. At the same time, the clamping force can be controlled, further reducing the possibility of damage to the flexible membrane surface due to excessive clamping force.

[0027] Optionally, the clamping frame 6 has an open C-shaped structure, and the adjusting element 7 is an adjusting knob located above the clamping frame 6. By rotating the adjusting knob, the first flexible contact element 4 can be easily moved up and down, realizing rapid adjustment of the clamping space.

[0028] Optionally, the clamping frame 6 also includes a chuck mounting base 12, on which the first flexible contact 4 is mounted, and the chuck mounting base 12 is connected to the adjustment knob. The chuck mounting base 12 makes the installation and replacement of the first flexible contact 4 more convenient.

[0029] As one embodiment, the clamping mechanism further includes an adjustment drive assembly, which includes a first lead screw, a drive motor 9, and a guide structure. The first lead screw has threaded sections with opposite directions of rotation. The two clamping seats 3 are respectively threaded into the threaded sections with opposite directions of rotation on the first lead screw. The first lead screw is connected to the output shaft of the drive motor 9. The guide structure is used to limit the opposing or backward movement of the two clamping seats 3. By setting threaded sections with opposite directions of rotation on the first lead screw and making the two clamping seats 3 respectively threaded into the corresponding threaded sections, when the drive motor 9 drives the first lead screw to rotate, the two clamping seats 3 can move synchronously in opposite or backward along the guide rail 2 under the limitation of the guide structure, thereby realizing precise stepless adjustment of the clamping distance. It can adapt to inflatable wing specimens of different sizes within the wingspan range of 300mm to 600mm, and can complete the clamping of specimens of different specifications without changing the clamps.

[0030] Optionally, the drive motor 9 is connected to the first lead screw via a right-angle transmission mechanism, which is a bevel gear pair. The bevel gear pair can change the direction of power transmission, facilitating the arrangement of the drive motor 9 and making the overall structure more compact.

[0031] Optionally, the guide structure is a linear slide rail, which is parallel to the first lead screw and mounted on the frame 1. The two clamping seats 3 are slidably connected to the linear slide rail via sliders. The linear slide rail provides precise guidance for the movement of the clamping seats 3, ensuring the smoothness and coaxiality of the movement of the two clamping seats 3. It should be noted that in this application, "guide rail 2" and "linear slide rail" refer to the same structure, namely, a track assembly fixedly mounted on the frame 1 for guiding the clamping seats 3 to slide in a linear direction. "Guide rail 2" is a general functional term for this structure, while "linear slide rail" is its specific selection in this embodiment.

[0032] Optionally, the drive motor 9 is a servo motor, which has precise position control capabilities and can achieve precise adjustment of the clamping distance.

[0033] Optionally, the first lead screw is a ball screw, which has the advantages of high transmission efficiency and smooth movement, and can further improve the accuracy and reliability of the position adjustment of the clamping seat 3.

[0034] In one implementation, the drive motor 9 drives the second lead screw 8 to rotate, and the second lead screw 8 transmits power to the first lead screw through a right-angle transmission mechanism. Since the left and right sections of the first lead screw have opposite thread directions, when the first lead screw rotates, the left and right clamping seats 3, under the constraint of the guide structure, perform synchronous and symmetrical reciprocating movements along the first lead screw, thereby driving the two clamping seats 3 to perform synchronous opposing or opposite movements on the guide rail 2. Through this transmission method, only one drive motor 9 is needed to achieve the synchronous and symmetrical movement of the two clamping seats 3, which simplifies the transmission structure and ensures the synchronicity and symmetry of the position adjustment of the two clamping seats 3. This helps ensure that the wing specimen is in a centered position after clamping, improving the accuracy of the test.

[0035] In one implementation, the force-applying head is strip-shaped, and the surface of the force-applying head facing the wing is a curved surface adapted to the outer contour of the wing. The strip-shaped force-applying head can provide a large contact area in the wingspan direction of the wing, and the surface facing the wing is set as a curved surface adapted to the outer contour of the wing, which allows the force-applying head to better fit the aerodynamic shape of the wing, so that the load is more evenly transferred to the wing surface during loading, which helps to simulate the distribution of real aerodynamic loads.

[0036] Optionally, the force-applying head is a flexible loading head made of polyurethane rubber. When in contact with the wing surface, the flexible loading head made of polyurethane rubber can adaptively deform according to the actual contour of the wing surface, further increasing the effective contact area and optimizing load distribution.

[0037] In one embodiment, the power component is a servo electric cylinder 10, and the telescopic rod of the servo electric cylinder 10 is the power output end. The servo electric cylinder 10 has precise displacement and frequency control capabilities, and can perform up-and-down reciprocating motion according to the set displacement and frequency to apply periodic fatigue loads to the wing, thereby accurately simulating the alternating aerodynamic loads borne by the wing during flight.

[0038] Optionally, the servo electric cylinder 10 is fixed to the top crossbeam of the frame 1 and is mounted on top, so that the force-applying head applies a downward loading force to the wing from above, which is consistent with the direction of action of the aerodynamic load.

[0039] As one implementation, a detection module is also included, comprising a force sensor and a cavity pressure sensor. The force sensor is positioned between the power output end and the force-applying head, while the cavity pressure sensor detects the air pressure inside the wing cavity 11. Real-time monitoring of the load applied to the wing by the force sensor ensures the accuracy and repeatability of the applied load. Real-time monitoring of air pressure changes inside the wing cavity 11 by the cavity pressure sensor allows for simultaneous recording of air pressure fluctuations during fatigue testing, providing data support for analyzing the coupling relationship between air pressure fluctuations and membrane fatigue damage.

[0040] Optionally, a force sensor is installed at the end of the servo electric cylinder 10, located between the power output end and the flexible loading head, and can directly measure the actual load applied to the wing surface.

[0041] As one implementation, the detection module also includes a DIC image acquisition camera, whose lens is positioned facing the wing surface area between the two clamping seats 3. The DIC image acquisition camera can continuously capture images of the wing surface in a non-contact manner, and calculate and output the full-field displacement field and strain field of the specimen surface through digital image correlation. This avoids the interference of the added mass and stiffness of traditional strain gauges on the mechanical properties of the flexible membrane surface, and can intuitively capture the entire process of fatigue crack initiation and stiffness degradation on the membrane surface, providing comprehensive data support for fatigue damage evolution analysis.

[0042] Optionally, the DIC image acquisition camera is a binocular stereo vision camera, capable of measuring three-dimensional full-field displacement and strain.

[0043] Optionally, random speckle patterns are created on the wing surface before the test. The DIC image acquisition camera continuously captures speckle images during the loading process, and the full-field strain distribution is calculated by analyzing the displacement changes of the speckles using software.

[0044] As one embodiment, it also includes a pressure control component, which includes an air source and an inflation pipe, the inflation pipe connecting the air source and the wing air cavity 11. The pressure control component can inflate the wing air cavity 11 and achieve constant or variable pressure control during the test, thereby simulating different pressure conditions of the inflatable wing during actual service and meeting the needs of various test conditions.

[0045] Optionally, the air pressure control assembly also includes a proportional pressure regulating valve and a pressure gauge. The proportional pressure regulating valve is used to precisely regulate the inflation pressure, and the pressure gauge is used to display the current air pressure value.

[0046] Optionally, the air pressure control assembly also includes a pressure relief valve for quickly releasing the air pressure in the wing air chamber 11 after the test or in an emergency.

[0047] As one embodiment, the frame 1 also includes a support beam located above the two clamping seats 3, on which the power assembly is fixed. The support beam provides a stable mounting base for the power assembly, ensuring its stability during loading and facilitating the accurate transmission of the load. The support beam's location above the two clamping seats 3 allows the force-applying head to apply load vertically to the wing from above, conforming to the actual aerodynamic load's direction of action.

[0048] Optionally, the frame 1 also includes a frame base plate, with guide rails 2 positioned above the frame base plate. Support beams are fixedly connected to the frame base plate via columns, forming an inverted U-shaped structure. This inverted U-shaped structure has high structural rigidity, effectively reducing the impact of frame 1 deformation on test results during loading.

[0049] Optionally, the frame 1 is made of high-strength steel to ensure structural stability during testing.

[0050] The method of using the inflatable deformable wing fatigue strength testing device in one embodiment of the present invention is as follows: First, based on the wingspan of the inflatable wing to be tested, the drive motor 9 is started to rotate the first lead screw. The two threaded sections on the first lead screw with opposite directions drive the two clamping seats 3 to move in opposite directions or back to back on the linear slide rail, adjusting the distance between the two clamping seats 3 to a size that matches the wingspan of the wing.

[0051] Then, place both ends of the inflatable wing into the clamping spaces of the two clamping seats 3 respectively, and rotate the adjustment knob to move the first flexible contact 4 downwards until the two opposing first flexible contact 4 gently clamp the wing ends. The clamping force is evenly distributed on the surface of the wing end through the flexible clamps made of polyurethane rubber, achieving non-destructive clamping.

[0052] Next, gas at a set pressure is injected into the wing air chamber 11 through the air pressure control component via the air inflation pipe, and the air pressure inside the wing air chamber 11 is monitored in real time by the air chamber pressure sensor until the air pressure reaches the set value required for the test.

[0053] Subsequently, random speckle patterns were created on the wing surface, and the position of the DIC image acquisition camera was adjusted so that the camera lens was facing the wing surface area between the two clamping seats 3.

[0054] The servo electric cylinder 10 is activated, and its extension rod reciprocates up and down according to a set displacement and frequency, applying a periodic fatigue load to the wing through the flexible loading head. During the loading process, a force sensor monitors the magnitude of the load in real time, an air chamber pressure sensor monitors the air pressure changes inside the wing's air chamber 11 in real time, and a DIC image acquisition camera continuously captures speckle images of the wing surface.

[0055] After the test is completed, the servo electric cylinder 10 is turned off, the air pressure in the wing air chamber 11 is released through the pressure relief valve, the adjustment knob is rotated to loosen the first flexible contact 4, and the wing specimen is removed. By performing digital image correlation analysis on the images captured by the DIC image acquisition camera, the full-field displacement field and strain field data of the specimen surface can be obtained. Combined with the data from the force sensor and the air chamber pressure sensor, a comprehensive assessment of the fatigue strength of the inflatable deformable wing is completed.

[0056] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A fatigue strength testing device for an inflatable deformable wing, characterized in that, Includes a frame (1), a clamping mechanism, and a force-applying mechanism; The clamping mechanism includes a guide rail (2) and two clamping seats (3); the guide rail (2) is disposed on the frame (1), and the two clamping seats (3) are slidably connected to the guide rail (2); each clamping seat (3) is provided with two oppositely disposed first flexible contact members (4), and a clamping gap for clamping the wing end is formed between the two first flexible contact members (4); The force-applying mechanism includes a power component and a force-applying head; the power component is mounted on the frame (1), the force-applying head is connected to the power output end of the power component, and the force-applying head is provided with a second flexible contact (5) facing the area between the two clamping seats (3).

2. The inflatable deformable wing fatigue strength testing device according to claim 1, characterized in that, The first flexible contact (4) and the second flexible contact (5) are both made of polyurethane rubber.

3. The inflatable deformable wing fatigue strength testing device according to claim 1, characterized in that, The clamping seat (3) includes a clamping frame (6) and an adjusting member (7). The clamping frame (6) has a clamping space for accommodating the wing tip. Two first flexible contact members (4) are disposed opposite each other in the clamping space. At least one first flexible contact member (4) is connected to the adjusting member (7) to adjust the size of the clamping space.

4. The inflatable deformable wing fatigue strength testing device according to claim 1, characterized in that, The clamping mechanism further includes an adjustment drive assembly, which includes a first lead screw, a drive motor (9), and a guide structure. The first lead screw has a threaded section with opposite rotation direction. The two clamping seats (3) are respectively threaded into the threaded section with opposite rotation direction on the first lead screw. The first lead screw is connected to the output shaft of the drive motor (9). The guide structure is used to limit the two clamping seats (3) to move in opposite directions or in opposite directions.

5. The inflatable deformable wing fatigue strength testing device according to claim 1, characterized in that, The force-applying head is strip-shaped, and the surface of the force-applying head facing the wing is a curved surface adapted to the outer contour of the wing.

6. The inflatable deformable wing fatigue strength testing device according to claim 1, characterized in that, The power component is a servo electric cylinder (10), and the telescopic rod of the servo electric cylinder (10) is the power output end.

7. The inflatable deformable wing fatigue strength testing device according to claim 1, characterized in that, It also includes a detection module, which includes a force sensor and an air chamber pressure sensor; the force sensor is located between the power output end and the force application head, and the air chamber pressure sensor is used to detect the air pressure inside the air chamber (11) of the wing.

8. The inflatable deformable wing fatigue strength testing device according to claim 7, characterized in that, The detection module also includes a DIC image acquisition camera, the lens of which is positioned facing the wing surface area between the two clamps (3).

9. The inflatable deformable wing fatigue strength testing device according to claim 1, characterized in that, It also includes a pressure control component, which includes an air source and an inflation pipe, the inflation pipe connecting the air source and the wing air chamber (11).

10. The inflatable deformable wing fatigue strength testing device according to claim 1, characterized in that, The frame (1) also includes a support beam located above the two clamping seats (3), and the power assembly is fixed to the support beam.

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