A method for rapid dynamic load application in static testing of ultra-large flexible wings

Abstract

The present invention proposes a method for quickly applying a follower load for a static test of an ultra-large flexible wing, comprising the following steps: Step 1: fixing the wing root on a load-bearing wall, fixing one end of a steel wire rope at a loading point, and hanging a weight on the other end; arranging a fixed pulley on a horizontally movable stand; connecting a strain gauge to a strain meter, and connecting a camera and a strain meter to a computer; Step 2: preloading the wing using a weight of a set mass, visually observing the deformation of the wing and moving the fixed pulley until the deformation is stable, so that the loading direction is approximately perpendicular to the wing beam axis, using a computer to determine whether the loading direction is perpendicular to the wing beam axis, adjusting the pulley position until the two are perpendicular to each other, comparing the difference between the test strain and the theoretical strain, and proceeding to the next step if the difference is less than a set threshold; Step 3: loading step by step according to a percentage according to the load application requirement, the loading process of each level is the same as that of Step 2, and recording the strain after each level of loading; Step 4: completing all loading and ending the test.

Description

Technical Field

[0001] The present invention relates to the field of aircraft static strength testing, and in particular to a method for rapidly applying a dynamic load for a static test of an ultra-large flexible wing. Background Art

[0002] In static wing tests, conventional loading equipment uses a fixed-direction loading method, which is feasible for testing wings with minimal deformation. However, in tests with large aspect ratios, wing deformation increases significantly. For example, the Airbus A350 has a wingspan of 64.75 meters and a maximum wing deflection of 5.2 meters. The Boeing B787 has a wingspan of 60.1 meters and a maximum wing deflection of 7.6 meters. The domestically produced C919 large aircraft has a wingspan of 35.8 meters and a maximum wing deflection of nearly 3 meters. Such large wing deformations lead to large errors between the test load and the load in actual flight conditions. The main reason is that wing deformation causes the load application direction to change relative to the local wing normal. Therefore, in static wing tests of aircraft with large or even extremely large deformations, correcting the load direction to reduce errors has become a key issue for researchers. In static tests, when a large flexible wing produces large or even super-large deformation, how to ensure that the loading direction is always perpendicular to the wing axis and develop a follower load application technology to simulate the actual loading conditions of the wing are of great engineering significance.

[0003] For the loading of dynamic load in static test of large deformation aircraft wing, relevant comprehensive research has been carried out in China. Qin Xianggui et al. used two sets of actuators, one set of actuators provides normal load, and the other set of actuators adjusts the position of the former's base to achieve dynamic loading, such as Figure 1 As shown in Figure 2; Pang Baocai et al. used a single-point dual-actuator follow-up loading method, that is, the wing was loaded with the resultant force generated by two mutually perpendicular actuators, and the loading point was the equivalent loading point of the aerodynamic load, as shown in Figure 2. Figure 2 shown.

[0004] While this loading method can accurately apply dynamic loads to large deformations of high-aspect-ratio wings, it has the disadvantage of limiting the length of the actuator extension. This makes it unsuitable for static testing of ultra-flexible wings when the deformation exceeds the actuator's operating range. Therefore, a dynamic load-applying method that can handle the extreme deformations of ultra-flexible wings is urgently needed. Summary of the Invention

[0005] Since the ultra-large flexible wing under consideration can produce large deformation, the existing technology uses equipment with limited actuation stroke such as actuators for loading, which is difficult to meet the requirements of the dynamic load loading test of the ultra-large flexible wing under large deformation, resulting in large errors during the test process, affecting the accuracy and even feasibility of the final test results.

[0006] In order to solve the above problems, the present invention proposes a method for rapid application of dynamic loads for static tests of ultra-large flexible wings, which is implemented by a load loading system including steel wire ropes, weights, fixed pulleys, a horizontally movable gantry system, strain gauges, strain meters, cameras, computers and other equipment. The steel wire ropes and weights are used for loading; the fixed pulleys cooperate with the horizontally movable gantry system to dynamically adjust the loading direction; the strain gauges and strain meters are used to collect strain data during the wing loading process; the camera is used to take pictures of the wing deformation and the loading orientation of the steel wire rope during the loading process; the computer is installed with image processing software for processing the photographed images to obtain the normal direction of the loading position and the direction of the steel wire rope; the computer is also used to record and analyze the strain and deformation values ​​of the wing during the loading process. The technical solution of the present invention specifically includes the following steps:

[0007] Step 1: Experimental preparation;

[0008] The wing root is fixed to a load-bearing wall, strain gauges are attached to the wing surface at the location where measurement is required, one end of a steel wire rope is fixed at the wing loading position, and the other end of the steel wire rope is used to carry a weight for loading; a fixed pulley is arranged on a horizontally movable gantry system, with the front end of the fixed pulley resting against the loading steel wire rope; when the horizontal position of the gantry system is adjusted, the horizontal position of the fixed pulley is changed, thereby changing the loading direction of the steel wire rope;

[0009] A fixed camera is arranged on site to take pictures of the wing deformation and the loading orientation of the wire rope. The camera is connected to a computer installed with image processing software to process the photographed images to obtain the normal direction of the loading position and the orientation of the wire rope. The strain gauge is connected to the strain meter, which is then connected to the computer.

[0010] Step 2: Test preloading;

[0011] Use weights of set mass to preload the wing. After placing the preload weights, move the fixed pulley appropriately according to the visual deformation of the wing, so that the direction of the loading wire rope is roughly perpendicular to the axis of the wing beam at the wing loading point, until the deformation stabilizes. Then use the image processing software on the computer to accurately determine whether the direction of the wire rope is perpendicular to the axis of the wing beam after stabilization. If not, continue to adjust the pulley position until the two are perpendicular to each other after stabilization again. Record the strain at this time and compare it with the theoretical strain. If the difference between the measured strain and the theoretical strain is less than the set threshold, it indicates that the test equipment is reliable and proceed to the subsequent formal loading.

[0012] Step 3: Test formal loading;

[0013] According to the load application requirements of the static test, loading is carried out step by step according to the percentage. The loading process of each level is as follows:

[0014] After placing the loading weight, the fixed pulley is appropriately moved according to the visual observation of the wing deformation, so that the direction of the loading wire rope is roughly perpendicular to the axis of the wing beam at the wing loading point until the deformation stabilizes. Then, the computer image processing software is used to accurately determine whether the direction of the wire rope is perpendicular to the axis of the wing beam after stabilization. If not, the pulley position is continuously adjusted until the two are perpendicular to each other after stabilization again. The strain at this time is recorded; and the wing deformation value is obtained using the computer image processing software;

[0015] Step 4: After the test, record and analyze the data;

[0016] After all loading is completed and the test ends, the computer will give the strain and deformation diagram of the ultra-large flexible wing based on all the recorded data.

[0017] Furthermore, the camera in step 1 is a binocular camera, which can take pictures of the wings and the loading position at the same time.

[0018] Furthermore, the weight set in step 2 is 10% of the theoretical maximum load at the wing loading position.

[0019] Furthermore, the image processing software on the computer calibrates the photographed image and measures the feature points to obtain the coordinates of the deformed wing surface, and then calculates the normal direction of the loading position and the direction of the wire rope based on the deformed coordinates.

[0020] Beneficial effects

[0021] The present invention provides a method for quickly applying a follower load for a static test of an ultra-large flexible wing. The method applies a concentrated load by hanging a weight on a steel wire rope, monitors the deformation state of the wing using a camera system, and adjusts the direction of the steel wire rope according to the deformation state using a fixed pulley with a variable support position to achieve the purpose of follower loading. The method can effectively avoid the problem of limited actuation stroke encountered in the prior art of using an actuator cylinder for loading, and can monitor the deformation state of the wing in real time to quickly adjust the loading direction, thereby ensuring test accuracy and efficiency and meeting the requirements for follower load loading tests of ultra-large flexible wings under large deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the follower load loading method used by Qin Xianggui et al.

[0023] Figure 2 This is a schematic diagram of the follower load loading method used by Pang Baocai et al.

[0024] Figure 3This is a flowchart of an implementation scheme of an embodiment of the present invention;

[0025] Figure 4 A schematic diagram of a loading method using weights and pulleys according to an embodiment of the present invention;

[0026] Figure 5 Schematic diagram of the test site layout of an embodiment of the present invention.

[0027] Among them: 1-super large flexible wing; 2-strain gauge; 3-steel wire rope; 4-weight; 5-fixed pulley; 6-horizontally movable platform; 7-strain gauge; 8-computer; 9-camera. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood and to enable those skilled in the art to better understand the solutions of the present invention, the present invention is further described and fully explained below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention.

[0029] This embodiment uses a super-large flexible UAV wing as an example and employs a method for rapidly applying a dynamic load for static testing of super-large flexible wings, as proposed in this invention, to conduct a dynamic loading test on the wing. This embodiment utilizes a load-loading system comprising a steel wire rope, weights, a fixed pulley, a horizontally movable gantry system, strain gauges, a strain gauge, a camera, a computer, and other equipment. The steel wire rope and weights are used for loading; the fixed pulley, in conjunction with the horizontally movable gantry system, is used to dynamically adjust the loading direction; the strain gauges and strain gauges are used to collect strain data during the wing loading process; the camera is used to photograph the wing deformation and the loading orientation of the steel wire rope during the loading process; the computer is installed with image processing software for processing the photographed images to obtain the normal direction of the loading position and the direction of the steel wire rope; and the computer is also used to record and analyze the strain and deformation values ​​of the wing during the loading process.

[0030] like Figure 3 As shown, the specific steps include:

[0031] Step 1: Experimental preparation;

[0032] like Figure 4 and Figure 5 As shown, the wing root is fixed to a load-bearing wall, strain gauges are attached to the position on the wing surface where measurements are required, one end of a steel wire rope is fixed at the wing loading position, and the other end of the steel wire rope is used to carry a weight for loading; a fixed pulley is arranged on a horizontally movable gantry system, with the front end of the fixed pulley resting against the loading steel wire rope; when the horizontal position of the gantry system is adjusted, the horizontal position of the fixed pulley can be changed, thereby changing the loading direction of the steel wire rope;

[0033] A fixed camera is arranged on site to take pictures of the wing deformation and the loading orientation of the wire rope. The camera is connected to a computer installed with image processing software to process the photographed images to obtain the normal direction of the loading position and the orientation of the wire rope. The strain gauge is connected to the strain meter, which is then connected to the computer.

[0034] In this embodiment, the camera is a binocular camera that can take pictures of the wing and the loading position at the same time; the image processing software on the computer calibrates the photographed image and measures the feature points to obtain the coordinates of the wing surface after deformation, and then calculates the normal direction of the loading position and the direction of the wire rope based on the deformed coordinates.

[0035] Step 2: Test preloading;

[0036] The wing is preloaded using a weight of a set mass. In this embodiment, the weight of the set mass is 10% of the theoretical maximum load-bearing capacity at the wing loading position. After placing the preload weight, the fixed pulley is appropriately moved according to the visual deformation of the wing so that the direction of the loading wire rope is roughly perpendicular to the axis of the wing beam at the wing loading point until the deformation is stable. Then, the image processing software on the computer is used to accurately determine whether the direction of the wire rope is perpendicular to the axis of the wing beam after stabilization. If not, the pulley position is continuously adjusted until the two are perpendicular to each other after stabilization again. The strain at this time is recorded and compared with the theoretical strain. If the difference between the measured strain and the theoretical strain is less than the set threshold, it indicates that the test equipment is reliable and the subsequent formal loading begins. Small load preloading is used here mainly because under small load preloading conditions, the theoretical calculation is more accurate and can be used as a basis for judging the accuracy of the test equipment.

[0037] Step 3: Test formal loading;

[0038] According to the load application requirements of the static test, loading is carried out step by step according to the percentage. The loading process of each level is as follows:

[0039] After placing the loading weight, the fixed pulley is appropriately moved according to the visual observation of the wing deformation, so that the direction of the loading wire rope is roughly perpendicular to the axis of the wing beam at the wing loading point until the deformation stabilizes. Then, the computer image processing software is used to accurately determine whether the direction of the wire rope is perpendicular to the axis of the wing beam after stabilization. If not, the pulley position is continuously adjusted until the two are perpendicular to each other after stabilization again. The strain at this time is recorded; and the wing deformation value is obtained using the computer image processing software;

[0040] Step 4: After the test is completed, record and analyze the data.

[0041] After all loading is completed and the test ends, the computer will give the strain and deformation diagram of the ultra-large flexible wing based on all the recorded data.

[0042] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A method for rapidly applying a dynamic load for static testing of an ultra-flexible wing, characterized by: The steps include: Step 1: Experimental preparation; The wing root is fixed to a load-bearing wall, strain gauges are attached to the locations on the wing surface where measurements are required, one end of a steel wire rope is fixed to the wing loading position, and the other end of the steel wire rope is used to carry weights for loading; a fixed pulley is placed on a horizontally movable gantry system, with the front end of the fixed pulley resting against the loading steel wire rope; When the horizontal position of the gantry system is adjusted, the horizontal position of the fixed pulley can be changed, thereby changing the loading direction of the wire rope; A fixed camera is arranged on site to take pictures of the wing deformation and the loading position of the wire rope; Connecting the camera to a computer, wherein the computer is installed with image processing software for processing the photographed image to obtain the normal direction of the loading position and the direction of the wire rope; connecting the strain gauge to the strain meter, and then connecting the strain meter to the computer; Step 2: Test preloading; Use weights of set mass to preload the wing. After placing the preload weights, move the fixed pulley appropriately according to the visual deformation of the wing, so that the direction of the loading wire rope is roughly perpendicular to the axis of the wing beam at the wing loading point, until the deformation stabilizes. Then use the image processing software on the computer to accurately determine whether the direction of the wire rope is perpendicular to the axis of the wing beam after stabilization. If not, continue to adjust the pulley position until the two are perpendicular to each other after stabilization again. Record the strain at this time and compare it with the theoretical strain. If the difference between the measured strain and the theoretical strain is less than the set threshold, it indicates that the test equipment is reliable and proceed to the subsequent formal loading. Step 3: Test formal loading; According to the load application requirements of the static test, loading is carried out step by step according to the percentage. The loading process of each level is as follows: After placing the loading weight, the fixed pulley is appropriately moved according to the visual observation of the wing deformation, so that the direction of the loading wire rope is roughly perpendicular to the axis of the wing beam at the wing loading point until the deformation stabilizes. Then, the computer image processing software is used to accurately determine whether the direction of the wire rope is perpendicular to the axis of the wing beam after stabilization. If not, the pulley position is continuously adjusted until the two are perpendicular to each other after stabilization again. The strain at this time is recorded; and the wing deformation value is obtained using the computer image processing software; Step 4: After the test, record and analyze the data; After loading is completed and the test ends, the computer gives the strain and deformation diagram of the ultra-large flexible wing based on all the recorded data.

2. The method for rapidly applying a dynamic load for static testing of an ultra-flexible wing according to claim 1, characterized in that: The camera in step 1 is a binocular camera, which can take pictures of the wing and the loading position at the same time.

3. The method for rapidly applying a dynamic load for static testing of an ultra-flexible wing according to claim 1, characterized in that: The weight set in step 2 is 10% of the theoretical maximum load at the wing loading position.

4. The method for rapidly applying a dynamic load for static testing of an ultra-flexible wing according to claim 1, characterized in that: The image processing software on the computer calibrates the photographed image and measures the feature points to obtain the coordinates of the deformed wing surface, and then calculates the normal direction of the loading position and the direction of the wire rope based on the deformed coordinates.

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