Airfoil structure virtual test loading analysis method based on digital simulation

Abstract

The invention belongs to the technical field of aircraft design, and discloses an airfoil structure virtual test loading analysis method based on digital simulation, which comprises the following steps of: firstly, carrying out detail finite element modeling according to an airfoil structure digital model, the attribute of the connecting piece is calculated and assigned according to the simplification principle of a bush unit, and the center coordinate of a loading point is determined according to the position of an adhesive tape or a pull-press block in the test partial load scheme; simulation analysis is carried out after loading is completed, loading is carried out according to the initial load direction, the load is discretized to a single loading point, then the single loading point is recorded, coordinates of a center node of the loading point and coordinates of an actuator connecting point after deformation are obtained, then the direction of a loading vector is obtained, all loading points of the simulation model are loaded, and a simulation result is obtained. After analysis is carried out, linear / nonlinear static force, buckling and post-buckling calculation is carried out; analyzing a stress-strain identification test risk position according to a calculation result, and pasting a strain gauge. The method can guide the design of a loading scheme in an airfoil structure test, improves the calculation precision, recognizes the test risk, avoids the loss of a test piece, and reduces the test cost.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft design, and relates to a virtual simulation analysis of the static / fatigue test state strength of an aircraft wing structure, and in particular to a virtual test loading analysis method for a wing structure based on digital simulation. Background Art

[0002] Traditional aircraft static / fatigue tests obtain internal force results based on the finite element model of the natural grid, and perform calculations in combination with engineering algorithms to identify test risks and obtain theoretical values ​​of load-transmitting structural strain. The results of engineering algorithms are reliable when the structure is simple, the load is single, and the simplification is reasonable. Its disadvantage is that the model is simplified a lot and cannot reflect local conditions. For example, in engineering tests, test loads are usually applied by adhesive tape loading. The loading itself has practical limitations and will cause differences in test measurement results in the loading influence area. It is easy to be misjudged as unreasonable model simplification in model verification work. At the same time, in the identification of test risks, inaccurate identification of areas with complex loads or affected by loading may cause greater test risks.

[0003] In addition, the load-bearing capacity of the location loaded with tape is generally calculated using engineering algorithms. The calculation results are conservative and the conservative amount is large. When the wing load concentration is large, the load distributed by the tape is likely to exceed the allowable load limit of the structure at the adhesive point, resulting in the loading scheme being unusable and test loading being difficult, and other loading methods must be used instead.

[0004] Analysis methods based on digital simulation can effectively solve such problems, but most digital simulations focus on macroscopic behavior and ignore changes in local structures, which may have a significant impact on the results in some cases. For example, the loading point may fail before the structure itself, resulting in a huge waste of resources. Therefore, a reasonable virtual simulation analysis loading method with small deviations is urgently needed to carry out strength analysis and test scheme design. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a wing structure virtual test loading analysis method based on digital simulation, which focuses on the boundary constraint level, guides the loading scheme design in the wing structure test, improves the calculation accuracy, identifies the test risks, and reduces the test cost.

[0006] The technical solution of the present invention is as follows:

[0007] A virtual test loading analysis method for an airfoil structure based on digital simulation comprises the following steps:

[0008] S1: Detailed finite element modeling is performed according to the digital model of the airfoil structure, and the modeling includes the real size and real properties of the airfoil structure;

[0009] S2: According to the characteristics of the connector, the properties of the connector are calculated and assigned using the simplified principle of the bush unit;

[0010] S3: Determine the center coordinates of the loading point according to the location of the tape or tension and compression block in the test load distribution scheme;

[0011] S4: If the test is loaded by tape, an MPC unit with the same size as the tape is established; if the test is loaded by tension and compression blocks, a double-layer unit with the same size as the tension and compression blocks is established for loading;

[0012] S5: After loading is completed, simulation analysis is carried out, loading is performed according to the initial load direction, the load is discretized to a single loading point, and then the single loading point is recorded to obtain the coordinates of the center node of the loading point after deformation and the coordinates of the actuator connection point;

[0013] S6: Connect the coordinates of the center node of the loading point and the connection point of the actuator after deformation to obtain the direction of the loading vector;

[0014] S7: Load all loading points of the simulation model, constrain them according to the experimental constraints, carry out simulation analysis combining geometric nonlinearity and material nonlinearity, and perform linear / nonlinear static, buckling and post-buckling calculations;

[0015] S8: Analyze stress and strain based on the calculation results of the detailed finite element model and identify the test risk locations;

[0016] S9: Paste the strain gauge at the location of the test risk determined by analysis;

[0017] S10: Test verification. If there are any abnormal conditions during the test, stop the test immediately, perform local reinforcement, repeat S7 to S9, and conduct the test again.

[0018] Furthermore, in S1, according to the digital model of the wing surface structure, the wing beam, wall panel and rib structure are modeled with detailed finite element using two-dimensional shell elements, and the modeling includes the real thickness and real offset properties of the structure.

[0019] Furthermore, in S2, according to the characteristics of the connector: if the meshes between two fasteners are adjacent in the continuous interval and the fasteners are loaded in shear, CBUSH units are used for point-to-point connection; if the number of meshes between fasteners exceeds 3, the MPC+CBUSH+MPC connection form is used as much as possible to simulate the fasteners.

[0020] Furthermore, in S3, the geometric center position coordinates of the tape or tension and compression block obtained in the test load distribution scheme are designed to be the center coordinates of the loading point.

[0021] Furthermore, in S4, if the test is loaded by a tape, an MPC unit with the same size coverage area as the tape is established, and the loading is implemented based on the stiffness of the structural connection area; if the test is loaded by a tension and compression block, a double-layer solid unit with the same size coverage area as the tension and compression block is established, and if there is a rubber pad structure, an additional layer of unit is added close to the structural side to simulate the stiffness characteristics of the rubber pad structure on the connection surface, and the MPC unit is used on the top surface of the solid unit to simulate the loading.

[0022] Furthermore, in S5, simulation analysis is carried out after loading is completed. The load is loaded in the direction of the initial load, and the load is discretized to a single loading point. For the single loading point, the load is first loaded in a direction perpendicular to the chord plane, and the force following option in the nonlinear calculation is turned on to obtain the coordinates of the center node of the loading point after deformation; then, the coordinates of the actuator connection point are obtained according to the position of the actuator loaded by the experimental installation gantry.

[0023] Furthermore, in S6, the coordinates of the center node of the deformed loading point and the actuator connection point are connected to obtain the direction of the real loading vector, and the loading vector direction is obtained for each loading point after discretization.

[0024] Furthermore, in S7, each discrete loading point in the simulation model is loaded and constrained according to the experimental constraints. After debugging the model, NASTRAN or Abaqus software is used to carry out simulation analysis combining geometric nonlinearity and material nonlinearity, and linear / nonlinear static, buckling and post-buckling calculations are performed as required.

[0025] Furthermore, in S8, based on the calculation results of the detailed finite element model, the stress, strain and connector load of the entire wing structure are extracted; the strength of the entire structural component and the strength of the connection area of ​​the tape or tension and compression block are analyzed, so as to identify the minimum margin, discover the test risk, and clarify the risk occurrence area.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. The present invention can guide the design of loading schemes in wing surface structure tests and improve calculation accuracy for wing surface strength tests of large amphibious aircraft with large wing surface load concentration or wing box section structures with the center of pressure deviating from the wing box. It can also identify test risks, avoid test piece losses, and reduce test costs.

[0028] 2. The present invention provides a modeling method and a loading process for the wing structure strength test, and the method of use is clear and concise, and can be used to guide the virtual simulation analysis of the wing structure strength test and obtain more accurate results. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solution of the implementation method of the patent of the present invention, the following is a brief introduction to the drawings required for use in the implementation method. It should be understood that the following drawings only show certain embodiments of the patent of the present invention and should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A schematic diagram of a test piece structure and a loading arrangement according to an embodiment of the present invention;

[0031] 5 and 7 in the figure are the size marks of the loading tape;

[0032] Figure 2 It is a schematic diagram of the loading results of the finite element simulation of the wing structure test in the embodiment. DETAILED DESCRIPTION

[0033] This section is an embodiment of the present invention, which is used to explain and illustrate the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0034] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships as given in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or case referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implying the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0035] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be interpreted in a broad sense, for example, it can be a fixed connection, a detachable connection or an integrated connection; it can be a mechanical connection or a point connection; it can be a direct connection or a connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0036] Embodiment 1:

[0037] A virtual test loading analysis method for an airfoil structure based on digital simulation comprises the following steps:

[0038] S1: Detailed finite element modeling is performed according to the digital model of the airfoil structure, and the modeling includes the real size and real properties of the airfoil structure;

[0039] S2: According to the characteristics of the connector, the properties of the connector are calculated and assigned using the simplified principle of the bush unit;

[0040] S3: Determine the center coordinates of the loading point according to the location of the tape or tension and compression block in the test load distribution scheme;

[0041] S4: If the test is loaded by tape, an MPC unit with the same size as the tape is established; if the test is loaded by tension and compression blocks, a double-layer unit with the same size as the tension and compression blocks is established for loading;

[0042] S5: After loading is completed, simulation analysis is carried out, loading is performed according to the initial load direction, the load is discretized to a single loading point, and then the single loading point is recorded to obtain the coordinates of the center node of the loading point after deformation and the coordinates of the actuator connection point;

[0043] S6: Connect the coordinates of the center node of the loading point and the connection point of the actuator after deformation to obtain the direction of the loading vector;

[0044] S7: Load all loading points of the simulation model, constrain them according to the experimental constraints, carry out simulation analysis combining geometric nonlinearity and material nonlinearity, and perform linear / nonlinear static, buckling and post-buckling calculations;

[0045] S8: Analyze stress and strain based on the calculation results of the detailed finite element model and identify the test risk locations;

[0046] S9: Paste the strain gauge at the location of the test risk determined by analysis;

[0047] S10: Test verification. If there are any abnormal conditions during the test, stop the test immediately, perform local reinforcement, repeat S7 to S9, and conduct the test again.

[0048] In S1, according to the digital model of the wing surface structure, the wing beam, wall panel and rib structure are modeled with detailed finite element using two-dimensional shell elements, and the modeling includes the real thickness and real offset properties of the structure.

[0049] In S2, according to the characteristics of the connector: if the meshes between two fasteners are adjacent in the continuous interval and the fasteners are loaded in shear, CBUSH units are used for point-to-point connection; if the number of meshes between fasteners exceeds 3, the MPC+CBUSH+MPC connection form is used as much as possible to simulate the fasteners.

[0050] In S3, the geometric center position coordinates of the tape or tension and compression block obtained in the test load distribution plan are the center coordinates of the loading point.

[0051] In S4, if the test is loaded by tape, an MPC unit with the same size coverage area as the tape is established, and loading is implemented based on the stiffness of the structural connection area; if the test is loaded by tension and compression blocks, a double-layer solid unit with the same size coverage area as the tension and compression blocks is established. If there is a rubber pad structure, an additional layer of unit is added close to the structural side to simulate the stiffness characteristics of the rubber pad structure on the connection surface, and the MPC unit is used on the top surface of the solid unit to simulate the loading.

[0052] In S5, simulation analysis is carried out after loading is completed. The load is loaded in the direction of the initial load and the load is discretized to a single loading point. For a single loading point, the load is first loaded in a direction perpendicular to the chord plane, and the force following option in the nonlinear calculation is turned on to obtain the coordinates of the center node of the loading point after deformation; then, the coordinates of the actuator connection point are obtained according to the position of the actuator loaded by the experimental installation gantry.

[0053] In S6, the coordinates of the center node of the loading point after deformation and the connection point of the actuator are connected to obtain the direction of the real loading vector, and the direction of the loading vector is obtained for each loading point after discretization.

[0054] In S7, each discrete loading point in the simulation model is loaded and constrained according to the experimental constraints. After debugging the model, NASTRAN or Abaqus software is used to carry out simulation analysis combining geometric nonlinearity and material nonlinearity, and linear / nonlinear static, buckling and post-buckling calculations are performed as required.

[0055] In S8, based on the calculation results of the detailed finite element model, the stress, strain and connector load of the entire wing structure are extracted; the strength of the entire structural component and the strength of the connection area of ​​the tape or tension and compression block are analyzed to identify the minimum margin, discover the test risks, and clarify the risk occurrence area.

[0056] Embodiment 2:

[0057] The structure of the wing box section in the present invention comprises a front beam, a rear beam, an upper wall plate, a lower wall plate and wing ribs.

[0058] In this embodiment, the wing structure virtual test loading calculation method based on digital simulation mainly includes the following steps:

[0059] Step 1: According to the digital model of the wing structure, use two-dimensional shell elements to carry out detailed finite element modeling of structures such as wing beams, wall panels and ribs. The modeling should include the actual thickness, offset and other properties of the structure, and try to use quadrilateral elements to ensure the quality of the unit mesh;

[0060] Step 2: Select a reasonable fastener unit for simulation based on the characteristics of the connector. For example, if the meshes between two fasteners are adjacent (number < 2) in a continuous interval and the fasteners are loaded in shear, you can use CBUSH units for point-to-point connection instead of adding MPC connections. If the number of meshes between fasteners exceeds 3, try to use the MPC+CBUSH+MPC connection form for fastener simulation, which is more accurate.

[0061] The "CBUSH" unit and "MPC" unit are a special combination connection unit, which is used to simulate the behavior characteristics of fasteners in structural components in the digital simulation software MSC.NASTRAN. By assigning unit properties, the flexibility, damping and constraint conditions of fasteners can be simulated to accurately simulate the actual connection behavior and stress distribution. In use, the tensile stiffness of fasteners is calculated by beam theory, and the shear stiffness of fasteners is calculated by Huss formula. The stiffness characteristics with less influence in the analysis can be simplified. For example, the torsional stiffness can be assigned a value of 100Nmm / rad, and the bending stiffness can be assigned a value of 109Nmm2 / rad, etc.;

[0062] Step 3: Design the geometric center coordinates of the tape or tension and compression block obtained in the test load distribution plan, which are the center coordinates of the loading point;

[0063] Step 4. In the general test digital simulation, the load is directly applied at the center of the loading point, and the peripheral stress distribution deviation is large. The present invention provides the following loading method: If the test is loaded by a tape, an MPC unit with the same size coverage area as the tape is established, and the loading is implemented based on the stiffness of the structural connection area. If the tension and compression block is loaded, a double-layer solid unit with the same size coverage area as the tension and compression block is established (such as the CHEXA8 unit in the NASTRAN software). If there are structures such as rubber pads, an additional layer of units should be added near the structural side to simulate the structural stiffness characteristics of the connection surface rubber pads, etc., and the MPC unit is used on the top surface of the solid unit to simulate the loading.

[0064] Step 5: After loading is completed, simulation analysis is carried out. Usually, the load is loaded in the direction of the initial load and the load is discretized to a single loading point. For a single loading point, first load in the direction perpendicular to the chord plane and turn on the force following option in the nonlinear calculation to obtain the coordinates of the center node of the loading point after deformation; then, the coordinates of the actuator connection point are obtained according to the position of the actuator loaded by the gantry installed in the test;

[0065] Step 6: Connect the coordinates of the two points obtained in the previous step to obtain the direction of the real loading vector, and obtain the direction of the loading vector for each loading point after discretization;

[0066] Step 7: Load each discrete loading point in the simulation model and constrain it according to the experimental constraints. After debugging the model, use NASTRAN or Abaqus software to carry out simulation analysis combining geometric nonlinearity and material nonlinearity, and perform linear / nonlinear static, buckling and post-buckling calculations as required;

[0067] Step 8. Extract stress, strain and connector load for the entire wing structure based on the calculation results of the detailed finite element model. Analyze the strength of the entire structure and the strength of the tape / block connection area to identify the minimum margin, discover test risks, and clarify the risk area;

[0068] Step 9: Paste strain gauges at the locations where the test risks are analyzed and determined, monitor the strain state during the test, and detect abnormal conditions in a timely manner;

[0069] Step 10: Test verification: If any abnormal situation occurs during the test, such as the strain significantly exceeds the calculated value and shows an amplifying trend, stop the test in time, strengthen the local area, repeat steps 7 to 9, and re-test to effectively avoid the loss of the test piece.

[0070] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A virtual test loading analysis method for wing structure based on digital simulation, characterized in that: The following steps are involved: S1: Detailed finite element modeling is performed according to the digital model of the airfoil structure, and the modeling includes the real size and real properties of the airfoil structure; S2: According to the characteristics of the connector, the properties of the connector are calculated and assigned using the simplified principle of the bush unit; S3: Determine the center coordinates of the loading point according to the location of the tape or tension and compression block in the test load distribution scheme; S4: If the test is loaded by tape, an MPC unit with the same size as the tape is established; if the test is loaded by tension and compression blocks, a double-layer unit with the same size as the tension and compression blocks is established for loading; S5: After loading is completed, simulation analysis is carried out, loading is performed according to the initial load direction, the load is discretized to a single loading point, and then the single loading point is recorded to obtain the coordinates of the center node of the loading point after deformation and the coordinates of the actuator connection point; S6: Connect the coordinates of the center node of the loading point and the connection point of the actuator after deformation to obtain the direction of the loading vector; S7: Load all loading points of the simulation model, constrain them according to the experimental constraints, carry out simulation analysis combining geometric nonlinearity and material nonlinearity, and perform linear / nonlinear static, buckling and post-buckling calculations; S8: Analyze stress and strain based on the calculation results of the detailed finite element model and identify the test risk locations; S9: Paste the strain gauge at the location of the test risk determined by analysis; S10: Test verification. If there are any abnormal conditions during the test, stop the test immediately, perform local reinforcement, repeat S7 to S9, and conduct the test again.

2. The method for virtual test loading analysis of wing structure based on digital simulation according to claim 1 is characterized in that: In the above S1, according to the digital model of the wing surface structure, the wing beam, wall panel and rib structure are modeled with detailed finite element using two-dimensional shell elements, and the modeling includes the real thickness and real offset properties of the structure.

3. The method for virtual test loading analysis of wing structure based on digital simulation according to claim 1 is characterized in that: In S2, according to the characteristics of the connector: if the meshes between two fasteners are adjacent in the continuous interval and the fasteners are loaded in shear, CBUSH units are used for point-to-point connection; if the number of meshes between the fasteners exceeds 3, the MPC+CBUSH+MPC connection form is used as much as possible to simulate the fasteners.

4. The method for virtual test loading analysis of wing structure based on digital simulation according to claim 1 is characterized in that: In the above-mentioned S3, the geometric center position coordinates of the tape or the tension and compression block obtained in the test load distribution scheme are the center coordinates of the loading point.

5. The method for virtual test loading analysis of wing structure based on digital simulation according to claim 1 is characterized in that: In the above S4, if the test is loaded by a tape, an MPC unit with the same size as the area covered by the tape is established, and the loading is performed based on the stiffness of the structural connection area; If the test is loaded by a tension-compression block, a double-layer solid unit with the same size and coverage area as the tension-compression block is established. If there is a rubber pad structure, an additional layer of unit is added close to the structure side to simulate the stiffness characteristics of the rubber pad structure on the connection surface. The MPC unit is used on the top surface of the solid unit to simulate the loading.

6. The method for virtual test loading analysis of wing structure based on digital simulation according to claim 1 is characterized in that: In the above-mentioned S5, simulation analysis is carried out after loading is completed, loading is performed in the direction of the initial load, and the load is discretized to a single loading point. For the single loading point, loading is first performed in a direction perpendicular to the chord plane, and the force following option in the nonlinear calculation is turned on to obtain the coordinates of the center node of the loading point after deformation; then, the coordinates of the actuator connection point are obtained according to the position of the actuator loaded by the experimental installation gantry.

7. The method for virtual test loading analysis of airfoil structure based on digital simulation according to claim 1 is characterized in that: In the above-mentioned S6, the coordinates of the two points of the center node of the loading point after deformation and the actuator connection point are connected to obtain the direction of the real loading vector, and the direction of the loading vector is obtained for each loading point after discretization.

8. The method for virtual test loading analysis of wing structure based on digital simulation according to claim 1 is characterized in that: In the above-mentioned S7, each discrete loading point in the simulation model is loaded and constrained according to the experimental constraints. After debugging the model, NASTRAN or Abaqus software is used to carry out simulation analysis combining geometric nonlinearity and material nonlinearity, and linear / nonlinear static, buckling and post-buckling calculations are performed as required.

9. The method for virtual test loading analysis of wing structure based on digital simulation according to claim 1, characterized in that: In the above-mentioned S8, based on the calculation results of the detailed finite element model, the stress, strain and connector load of the entire wing structure are extracted; the strength of the entire structural member and the strength of the connection area of ​​the tape or tension and compression block are analyzed, so as to identify the minimum margin, discover the test risk, and clarify the risk occurrence area.

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