Strength simulation method for stringer breaking design area of wallboard structure
By combining the real rod and the virtual rod, the load transfer in the long-truss breaking area is simulated, which solves the problem of difficulty in accurately capturing stress distribution in the prior art, improves simulation accuracy and modeling efficiency, and obtains accurate internal force data for optimization Structural design.
Patent Information
- Application Number
- CN202411198549.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-29
- Publication Date
- 2025-01-03
AI Technical Summary
The prior art is difficult to accurately capture the load transfer process when simulating the stress distribution of the long-truss breaking area of the aircraft wing box structure, resulting in insufficient structural strength and accelerated fatigue cracks, affecting safety and service life.
The natural mesh model is established by combining the real rod and the virtual rod. By adding virtual rods to simulate load transfer at the long-truss break, and giving the actual area and thickness attributes to each unit in the finite element model, static and dynamic analysis is carried out. Obtain internal force results and verify the accuracy of simulation results in combination with experiments.
The simulation accuracy of the finite element model in the long-truss fracture area is improved, the modeling process is simplified, resource consumption is reduced, and accurate internal force data is obtained to guide the structural optimization design.
Smart Images
Figure CN119249790A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of static / fatigue strength design of aircraft structures, and in particular relates to a strength simulation method for a long truss break-off design area of a wall panel structure. Background Art
[0002] In the prior art, the wing box structures such as the wings and tail of the aircraft usually adopt two layout modes in the longitudinal long stringer arrangement: one is the equal percentage chord length arrangement, and the other is the equal width arrangement. Different long stringer arrangement forms correspond to different simplified methods in finite element modeling. The equal percentage chord length arrangement structure of the long stringer is relatively simple. The number of long stringers at each station in the span direction is the same, but the spacing is different. In simplified modeling, it can be directly modeled according to the actual structure, but this form of structure is relatively heavy; the equal width arrangement adjusts the number of long stringers as the load and structure change, so that the weight distribution is more reasonable, but in simplified modeling, special attention should be paid to the long stringer disconnection design area to ensure the rationality of the model load transfer and the stability of the strain. In actual calculations, in the long stringer disconnection area and where the long stringer is interrupted at certain positions, the sudden change of the structure is prone to stress concentration. This phenomenon not only leads to insufficient local strength of the structure, but also accelerates the formation and development of fatigue cracks, thereby affecting the safety and service life of the entire structure. Therefore, when simulating the long-beam detachment area, the traditional finite element model often finds it difficult to accurately capture the complex stress distribution characteristics of the area, especially the process of how the load is transferred from the broken long beam to other structural components. Moreover, the simplified processing method for the long-beam detachment area in the prior art is not accurate enough, which easily leads to the internal force results predicted by the model being inconsistent with the actual situation. Summary of the invention
[0003] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a strength simulation method for the long girder breakaway design area of the wall panel structure, aiming to improve the accuracy of the finite element model of the long girder breakaway area and ensure that the model can accurately reflect the actual stress distribution in the area.
[0004] In order to solve the above problems, the technical solution adopted by the present invention is as follows: A strength simulation method for the long girder break-off design area of a wall panel structure comprises the following steps:
[0005] S1: According to the preliminary design structure layout of the wall panel provided by the structural department, determine the specific location of the long girder break;
[0006] S2: Use Nastran software to establish a finite element model of a natural network, and perform finite element discretization simplification on the wall panel structure, beam structure, and rib structure. The beam structure is composed of a beam flange and a beam web, and the rib structure is composed of a rib flange and a rib web. The intersections of the wall panel skin surface and the beam flange and rib flange are used as nodes. Beam units are used to simulate the long stringers, the beam flanges, and the rib flanges. Shell units are used to simulate the wall panel skin, the beam webs, and the rib webs.
[0007] S3: Simulate the breaking of the long girder. For the position where the long girder is broken, add a virtual rod with an area of 1 / 10 of the base area of the long girder at the rib position after the long girder is broken to simulate the load transfer after the long girder is broken;
[0008] S4: according to the attribute assignment of the simplified components in the model, the beam cap, the long stringer and the rib cap are assigned to the beam unit with the actual area attribute of the structure, and the shell unit attribute is assigned to the wall panel skin, the beam web and the rib web with the actual thickness of the structure;
[0009] S5: Extract the internal force of each unit in the finite element model, and solve the internal force such as the axial force and shear force borne by the wall skin unit, the axial force and bending moment borne by the long girder unit, and the axial force and bending moment borne by the beam flange. Check the continuity of the internal force solution at the long girder break. If there is no singularity, it can be used for subsequent engineering strength verification.
[0010] S6: Arrange strain gauges in the separation area, carry out test verification, compare the test results, and verify the conformity of the simulation method.
[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention adopts a combination of real rods and virtual rods to simulate the load transfer path after the long girder is broken off, thereby improving the simulation accuracy of the finite element model in the long girder breakoff area, and uses a combination of real rods and virtual rods to establish a natural grid model, which simplifies the modeling process of the long girder breakoff area and reduces the time and resources required for model establishment, and by performing loading analysis on the model and extracting internal force results, accurate internal force data is obtained to guide structural optimization design.
[0012] In the above strength simulation method, in step S1, determining the breaking position of the long stringer comprises the following steps:
[0013] S11: Obtaining the preliminary design structural layout drawing of the wall panel;
[0014] S12: Analyze the wall panel load conditions;
[0015] S13: Identify the need for long stringer breakaway;
[0016] S14: determine the severance position;
[0017] The panel loads in step S12 include but are not limited to flight loads, ground loads, water surface loads and temperature difference loads. In step S13, the long girder separation requirement includes determining whether the long girder separation needs to be set at the required position based on the panel load conditions and structural requirements.
[0018] In the above strength simulation method, step S2 comprises the following steps:
[0019] S21: Acquire structural parameters, and collect required structural parameters according to the preliminary design structural layout diagram of the wall panels provided by the structure, wherein the structural parameters include but are not limited to the size of the wall panels, the position of the long stringers, the position of the beam structures, and the position of the rib structures;
[0020] S22: Select finite element modeling tools;
[0021] S23: using the intersections of the panel skin outer surface and the beam structure and the rib structure as nodes, defining the node coordinates in the finite element model, and creating a natural network model according to the geometric shape and size parameters of the panel;
[0022] In the above-mentioned strength simulation method, in step S2, the beam unit is used to simulate the bending and torsion behaviors of the long stringer, the beam flange and the rib flange, and the shell unit is used to capture the stress and deformation of the wall panel skin, the beam web and the rib web structure.
[0023] In the above-mentioned strength simulation method, in step S3, the simulation of the long girder breaking includes: model simplification and virtual rod simulation, the model simplification includes establishing a model using the basic dimensions of the long girder between two rib segments before the rib segment closest to the long girder breaking point, and the virtual rod simulation requires that the direction of the virtual rod is to extend from the rib segment after the breaking point and the long girder node to the beam structure.
[0024] In the above strength simulation method, the attribute assignment in step S4 includes determining material attributes and allocation unit attributes, the material attributes include elastic modulus, Poisson's ratio and density, and the allocation unit attributes are simulated by the beam unit and the shell unit.
[0025] In the above strength simulation method, the attribute assignment in step S4 also includes assigning values to the virtual rods, and the virtual rod assignment includes setting area assignment and material attribute assignment.
[0026] In the above strength simulation method, step S5 comprises the following steps:
[0027] S51: Determine the load conditions, load types and combinations;
[0028] S52: Determine the specific loading position, loading size and loading direction according to the design drawing of the wall panel structure and the actual application scenario;
[0029] S53: Set boundary conditions and determine the degrees of freedom in the model;
[0030] S54: Perform static and dynamic analysis;
[0031] S55: extracting the internal force results of each unit from the finite element model, and checking the continuity of the internal force solution at the breaking point of the long stringer;
[0032] S56: analyzing the internal force results, evaluating the rationality of the finite element model, and optimizing the wall panel structure according to the internal force results;
[0033] S57: Compare the internal force result with theoretical data or existing data to verify the rationality of the finite element model. If the comparison result does not meet the expected requirements, return to the above step S3 or step S4 for adjustment.
[0034] In the above-mentioned strength simulation method, the strain gauges described in step S6 are arranged in the separation area to obtain actual strain data through experiments, so that the data obtained from the experiments are compared with the internal force results of the finite element model to verify the accuracy of the finite element model.
[0035] In the above-mentioned strength simulation method, the arrangement position of the strain gauge in step S6 also includes the area of stress concentration, and a loading device is used to simulate the load conditions in aircraft operation. The strain data is converted into stress and compared with the internal force results in the finite element model. If there is an unexpected difference between the stress and the internal force results, return to the above-mentioned step S2 to adjust the model parameters in sequence until a satisfactory matching degree is achieved. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Figure 1 It is a schematic diagram of the steps of a method for simulating the strength of a long girder break-off design area of a wall panel structure according to an embodiment of the present invention;
[0037] Figure 2 This is a schematic diagram of the step of determining the specific position where the long stringer breaks off in step S1 of an embodiment of the present invention;
[0038] Figure 3 This is a schematic diagram of the steps of establishing a natural network finite element model in step S2 of an embodiment of the present invention;
[0039] Figure 4 This is a schematic diagram of the step of extracting the internal force of each unit in the finite element model in step S5 of an embodiment of the present invention; DETAILED DESCRIPTION
[0040] The embodiments of the present invention are described in detail below. Figures 1 to 4 The embodiment of the present invention provides a method for simulating the strength of a long girder break-off design area of a wall panel structure, comprising the following steps:
[0041] S1: According to the preliminary design structure layout of the wall panel provided by the structural department, determine the specific location of the long girder break;
[0042] S2: Use Nastran software to establish a finite element model of the natural network, and use finite element discretization to simplify the panel structure, beam structure, and rib structure. Take the intersection of the panel skin surface and the beam flange and rib flange as nodes, use beam units to simulate the long stringers, beam flanges, and rib flanges, and use shell units to simulate the panel skin, beam webs, and rib webs.
[0043] S3: Simulate the breaking of the long girder. For the position where the long girder is broken, add a virtual rod with an area of 1 / 10 of the long girder base area at the rib after the long girder is broken to simulate the load transfer after the long girder is broken;
[0044] S4: According to the attributes assigned to the simplified components in the model, the beam flanges, long girders and rib flanges are assigned to the beam unit with the actual area attributes of the structure, and the shell unit attributes are assigned to the wall skin, beam web and rib web with the actual thickness of the structure.
[0045] S5: Extract the internal forces of each unit in the finite element model, including the axial force and shear force borne by the wall skin, the axial force and bending moment borne by the long stringer, and the axial force and bending moment internal forces borne by the beam flange. Check the continuity of the internal forces at the separation of the long stringer. If there is no singularity, it can be used for subsequent engineering strength verification.
[0046] S6: Arrange strain gauges in the long-beam breakaway area, conduct test verification, compare the test results, and verify the conformity of the simulation method. The present invention uses a combination of real rods and virtual rods to simulate the load transfer path after the long-beam breakaway, which improves the simulation accuracy of the finite element model in the long-beam breakaway area. The natural grid model established by combining real rods and virtual rods simplifies the modeling process of the long-beam breakaway area, reduces the time and resources required for model establishment, and obtains accurate internal force data by performing loading analysis on the model and extracting internal force results to guide structural optimization design.
[0047] Furthermore, step S1 determines the position of the long girder disconnection, including the following steps: S11: obtain the preliminary design structural layout of the wall panel; S12: analyze the wall panel load; S13: identify the long girder disconnection requirement; S14: determine the disconnection position; first, to determine the specific position of the long girder disconnection, it is necessary to obtain the preliminary design structural layout of the wall panel, which will show the layout of the wall panel, the position of the long girder, the position of the front beam and the rear beam structure, and other important structural elements in detail. The wall panel load in step S12 includes but is not limited to flight load, ground load, water surface load and temperature difference load, which will affect the stress analysis of the wall panel and further affect the design of the long girder disconnection. In step S13, the long girder disconnection requirement includes determining whether it is necessary to set the long girder disconnection at the required position according to the wall panel load and structural requirements. When determining the disconnection position in step S14, factors such as load distribution, structural strength and weight optimization need to be considered. Furthermore, in step S2, a finite element model is established using software. Of course, the present invention is not limited to a specific software type. Preferably, Nastran software is used to establish a finite element model of a natural network. Step S2 includes the following steps: S21: Acquire structural parameters, and collect required structural parameters according to the preliminary design structural layout diagram of the wall panels provided by the structure. The structural parameters include but are not limited to the size of the wall panels, the position of the long girders, the positions of the front beam and rear beam structures, and the position of the rib structures; S22: Select a finite element modeling tool; S23: Define the node coordinates in the finite element model with the intersection of the outer surface of the wall panel skin and the beam structure and the rib structure as nodes, and create a natural network model according to the geometric shape and size parameters of the wall panels; Further, in step S2, the beam unit is used to simulate the bending and torsional behavior of the long girders, beam flanges and rib flanges, and the shell unit is used to capture the stress and deformation of the wall panel skin, beam web and rib web structures.
[0048] Furthermore, in step S3, simulating the severance of the long girder includes: model simplification and virtual rod simulation. The model simplification includes establishing a model using the basic size of the long girder between two rib segments before the rib segment closest to the severance point of the long girder. In the virtual rod simulation, the direction of the virtual rod is required to extend from the rib segment after the severance point and the node of the long girder to the beam structure. In step S3, the size and shape of the long girder remain unchanged before the rib structure at the severance point to simplify the model. Furthermore, a virtual rod is added at the first rib position after the severance point of the long girder to simulate the load transfer after the severance of the long girder. Of course, the present invention does not limit the specific area of the virtual rod. Preferably, the area of the virtual rod is usually 1 / 1 of the basic area of the long girder. 0, to ensure that the virtual rod will not have a significant impact on the overall stiffness of the structure. Furthermore, the purpose of adding the virtual rod is mainly to simulate how the load after the long girder is broken extends from the broken rib structure and the long girder node to the adjacent beam structure or other structural components. In this way, the load transfer path after the long girder is broken can be simulated in the finite element model to ensure that the model can accurately reflect the actual situation. After completing the above steps, the model needs to be checked to ensure that the setting of the virtual rod will not have a negative impact on the overall stiffness and stability of the model. Of course, the present invention does not limit the specific inspection content. Preferably, the rationality of the virtual rod setting can be verified by checking the deformation and internal force distribution of the model.
[0049] Furthermore, the attribute assignment in step S4 includes determining material attributes and allocating unit attributes. Of course, the invention does not limit the specific content of the material attributes. Preferably, the material attributes include elastic modulus, Poisson's ratio and density. The allocated unit attributes are simulated by beam units and shell units. Furthermore, the section attributes and material attributes are defined in the beam unit. The section attributes need to be defined according to the section dimensions (such as width, height, etc.) and material properties of the actual structure. The material properties ensure that the mechanical behavior of the material is accurately reflected during simulation. Furthermore, the shell unit is used for structural simulation of thin plates such as skins, beam webs, and rib webs, including defining the thickness of the shell unit according to the thickness of the actual structure. After the initial attribute assignment, some fine-tuning may be required based on the analysis results to optimize the performance of the model. Of course, the invention does not limit the specific content of the fine-tuning. Furthermore, the attribute assignment in step S4 also includes assigning values to virtual rods. The virtual rod assignment includes setting area assignment and material property assignment.
[0050] Furthermore, after the establishment of the finite element model and the assignment of attributes are completed, the next step S5 is to perform loading analysis, which includes the following steps: S51: determine the load condition, determine the type and combination of loads; S52: determine the specific location, load size and load direction of the loading according to the design drawing of the wall panel structure and the actual application scenario; S53: set boundary conditions and determine the degrees of freedom in the model; S54: perform static and dynamic analysis; S55: extract the internal force results of each unit from the finite element model, and check the continuity of the internal force solution at the long girder break; S56: analyze the internal force results, evaluate the rationality of the finite element model, and optimize the wall panel structure according to the internal force results; S 57: Compare the internal force results with theoretical data or existing data to verify the rationality of the finite element model. If the comparison results do not meet the expected requirements, return to the above step S3 or step S4 for adjustment. In step S52, determine the specific loading position according to the design drawing of the wall panel structure and the actual application scenario. Of course, the present invention does not limit the specific loading size and loading direction. Preferably, the loading size involves calculating the aerodynamic pressure, gravity, etc., and the loading direction must be ensured to be consistent with the actual load. In step S54, perform static analysis to solve the internal force results under different load conditions. Of course, the present invention does not limit the specific mode of dynamic analysis. Preferably, perform dynamic analysis to consider vibration or transient response.
[0051] Furthermore, after completing the attribute assignment and loading analysis, the next step S6 is experimental verification to ensure the accuracy and reliability of the simulation results. In step S6, strain gauges are arranged in the separation area to obtain actual strain data through experiments, so that the data obtained from the experiment can be compared with the internal force results of the finite element model to verify the accuracy of the finite element model. Of course, the present invention does not limit the specific position of the strain gauge. Preferably, the strain gauge is arranged at a position with higher stress concentration. Furthermore, step S6 uses a loading device to simulate the load condition of the aircraft during operation, by converting the strain data into stress and comparing it with the internal force results in the finite element model. If there is an unexpected difference between the stress and the internal force results, return to the above step S2 to adjust the model parameters in sequence until a satisfactory matching degree is achieved.
[0052] It should be noted that in the description of the present invention, if there are any orientation descriptions, such as up, down, front, back, left, right, etc., the orientations or positional relationships indicated are all based on the orientations or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed or operated in a specific orientation, and cannot be understood as a limitation on the present invention.
[0053] In the description of the present invention, the meaning of "several" is one or more, the meaning of "more" is two or more, "greater than", "less than", "exceed" etc. are understood as not including the number, and "above", "below", "within" etc. are understood as including the number. If there is a description of the first wall panel structure long girder separation design area strength simulation method or the second, it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.
[0054] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.
[0055] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.
Claims
1. A method for simulating the strength of a long girder break-off design area of a wall panel structure, characterized in that: The steps include: S1: According to the preliminary design structure layout of the wall panel provided by the structural department, determine the specific location of the long girder break; S2: Use Nastran software to establish a finite element model of a natural network, and perform finite element discretization simplification on the wall panel structure, beam structure, and rib structure. The beam structure is composed of a beam flange and a beam web, and the rib structure is composed of a rib flange and a rib web. The intersections of the wall panel skin surface and the beam flange and rib flange are used as nodes. Beam units are used to simulate the long stringers, the beam flanges, and the rib flanges. Shell units are used to simulate the wall panel skin, the beam webs, and the rib webs. S3: Simulate the breaking of the long girder. For the position where the long girder is broken, add a virtual rod with an area of 1 / 10 of the base area of the long girder at the rib position after the long girder is broken to simulate the load transfer after the long girder is broken; S4: according to the attribute assignment of the simplified components in the model, the beam cap, the long stringer and the rib cap are assigned to the beam unit with the actual area attribute of the structure, and the shell unit attribute is assigned to the wall panel skin, the beam web and the rib web with the actual thickness of the structure; S5: extract the internal force of each unit in the finite element model, the internal force includes: the axial force and shear force borne by the wall panel skin, the axial force and bending moment borne by the long stringer, and the axial force and bending moment internal force borne by the beam flange, check the continuity of the internal force at the long stringer break, if there is no singularity, it can be used for subsequent engineering strength verification; S6: Arrange strain gauges in the long stringer breaking area, carry out test verification, compare the test results, and verify the conformity of the simulation method.
2. The strength simulation method according to claim 1, characterized in that: In the step S1, determining the detachment position of the long stringer comprises the following steps: S11: Obtaining the preliminary design structural layout drawing of the wall panel; S12: Analyze the wall panel load conditions; S13: Identify the need for long stringer breakaway; S14: determine the severance position; The panel loads in step S12 include but are not limited to flight loads, ground loads, water surface loads and temperature difference loads. In step S13, the long girder separation requirement includes determining whether the long girder separation needs to be set at the required position based on the panel load conditions and structural requirements.
3. The strength simulation method according to claim 1, characterized in that: The step S2 comprises the following steps: S21: Acquire structural parameters, and collect required structural parameters according to the preliminary design structural layout diagram of the wall panels provided by the structure, wherein the structural parameters include but are not limited to the size of the wall panels, the position of the long stringers, the position of the beam structures, and the position of the rib structures; S22: Select finite element modeling tools; S23: Using the intersections of the outer surface of the wall panel skin and the beam structure and the rib structure as nodes, defining the node coordinates in the finite element model, and creating a natural network model according to the geometric shape and size parameters of the wall panel.
4. The strength simulation method according to claim 1, characterized in that: In step S2, the beam unit is used to simulate the bending and torsion behaviors of the long stringer, the beam flange and the rib flange, and the shell unit is used to capture the stress and deformation of the wall panel skin, the beam web and the rib web structure.
5. The strength simulation method according to claim 1, characterized in that: In step S3, the simulation of the severing of the long girder includes: model simplification and virtual rod simulation, wherein the model simplification includes establishing a model using the basic dimensions of the long girder between two rib segments before the rib segment closest to the severing point of the long girder, and the virtual rod simulation requires that the direction of the virtual rod be extended from the rib segment after the severing point and the node of the long girder to the beam structure.
6. The strength simulation method according to claim 1, characterized in that: The attribute assignment in step S4 includes determining material attributes and allocation unit attributes, the material attributes include elastic modulus, Poisson's ratio and density, and the allocation unit attributes are simulated by the beam unit and the shell unit.
7. The strength simulation method according to claim 6, characterized in that: The assignment of properties in step S4 also includes assigning values to the virtual rod, and the virtual rod assignment includes setting area assignment and material property assignment.
8. The strength simulation method according to claim 1, characterized in that: The step S5 comprises the following steps: S51: Determine the load conditions, load types and combinations; S52: Determine the specific loading position, loading size and loading direction according to the design drawing of the wall panel structure and the actual application scenario; S53: Set boundary conditions and determine the degrees of freedom in the model; S54: Perform static and dynamic analysis; S55: extracting the internal force results of each unit from the finite element model, and checking the continuity of the internal force solution at the breaking point of the long stringer; S56: analyzing the internal force results, evaluating the rationality of the finite element model, and optimizing the wall panel structure according to the internal force results; S57: Compare the internal force result with theoretical data or existing data to verify the rationality of the finite element model. If the comparison result does not meet the expected requirements, return to the above step S3 or step S4 for adjustment.
9. The strength simulation method according to claim 8, characterized in that: Arranging strain gauges in the separation area in step S6 is used to obtain actual strain data through experiments, so that the data obtained from the experiments can be compared with the internal force results of the finite element model to verify the accuracy of the finite element model.
10. The strength simulation method according to claim 1, characterized in that: The arrangement position of the strain gauge in step S6 also includes the area of stress concentration. A loading device is used to simulate the load conditions during aircraft operation. The strain data is converted into stress and compared with the internal force results in the finite element model. If there is an unexpected difference between the stress and the internal force results, the process returns to step S2 to adjust the model parameters in sequence until a satisfactory matching degree is achieved.