Aircraft floating frame structure finite element modeling method, stress calculation method and related device

Abstract

The invention belongs to the technical field of aircraft strength design, and discloses an aircraft floating frame structure finite element modeling method, a stress calculation method and a related device.According to a known fuselage structure model, a first-round finite element model is established, and the first-round finite element model comprises a skin unit, a frame unit, a shear angle piece unit and a stringer unit which are conode; unit attributes are given to a skin unit, a frame unit, a shear angle sheet unit and a stringer unit in the first-round finite element model, and a second-round finite element model is obtained; and setting the material of the shear angle sheet unit in the second-round finite element model as an anisotropic material, and setting that the shear angle sheet unit is endowed with different material attributes along the radial direction, the annular direction and the shear direction of the fuselage to obtain the finite element model of the aircraft floating frame structure. According to the method, the shear angle sheet can be accurately and effectively modeled, and the force transfer form and rigidity setting in each direction of the shear angle sheet are accurate, so that the calculation result of the fuselage frame structure is accurate.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft strength design, and in particular relates to a finite element modeling method, a stress calculation method and related devices for an aircraft floating frame structure. Background Art

[0002] The overall finite element model of the aircraft is the most simplified finite element model of the entire aircraft. It analyzes the structural force transmission of the entire aircraft in the most resource-saving way, controls the dangerous parts of the entire aircraft, and provides a basis for the detailed model of the entire aircraft.

[0003] The aircraft fuselage structure includes skin, long stringers and frames. The frame structure is the main force transmission structure of the fuselage, which plays an important role in maintaining the fuselage shape and bearing the airtight load of the fuselage. Generally, the fuselage frame structure is designed as a floating frame, which is conducive to the passage of long stringers, has good damage tolerance characteristics, and is convenient for the adjustment and assembly of the frame structure. Due to the passage of long stringers, the shear angle pieces are not connected at one or both ends of the fuselage circumferential direction, and the structure cannot transmit circumferential tension and pressure loads, but can transmit force loads normally in the radial direction of the fuselage and the shear of the angle pieces. It is generally difficult for the overall finite element model of the whole aircraft to handle such problems. Usually, the shear angle pieces are treated as continuous load-transmitting elements, so that the shear angle pieces transmit force normally in the circumferential direction, resulting in a decrease in the force transmission of the frame structure and inaccurate calculated stress; another method is to establish a detailed finite element model, and one end of the shear angle piece is disconnected in the circumferential direction to ensure correct force transmission, but this method has a large workload and is not suitable for the overall finite element model. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a finite element modeling method, a stress calculation method and related devices for an aircraft floating frame structure. The present invention can accurately and effectively model the shear corner piece, and achieve accurate force transmission form and stiffness setting of the shear corner piece in all directions, thereby ensuring accurate calculation results of the fuselage frame structure.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A finite element modeling method for an aircraft floating frame structure includes the following steps: According to the known fuselage structure model, a first round of finite element models are established, wherein the first round of finite element models include skin units, frame units, shear corner unit units and long stringer units, wherein the skin units, frame units, shear corner unit units and long stringer units share a common node; Assigning unit attributes to the skin unit, frame unit, shear angle unit and long stringer unit in the first round of finite element model to obtain a second round of finite element model; The material of the shear corner unit in the second round of finite element model is set as anisotropic material, and different material properties are given to the shear corner unit along the radial, circumferential and shear directions of the fuselage to obtain the finite element model of the aircraft floating frame structure.

[0006] Preferably, the known fuselage structure model includes a skin, a frame, a shear corner piece and a long stringer, and the skin, the frame and the long stringer are connected, wherein the shear corner piece is connected to the skin at one end along the radial direction of the fuselage and is connected to the frame at the other end, and at least one end of the shear corner piece along the circumferential direction of the fuselage is a free end.

[0007] Preferably, when unit attributes are assigned to the skin units, frame units, shear angle unit and stringer units in the first round of finite element model, the unit attributes include material attributes and geometric attributes.

[0008] Preferably, when assigning unit attributes to the skin unit, frame unit, shear angle unit and stringer unit in the first round of finite element model: The geometric properties include: the thickness of the skin unit, the thickness of the web of the frame unit and the cross-sectional area of ​​the frame edge strip of the frame unit, the area of ​​the long stringer unit, and the thickness of the shear corner piece unit; Material properties include elastic modulus and Poisson's ratio.

[0009] Preferably, when the material of the shear corner piece unit in the second round of finite element model is set to anisotropic material, and different material properties are assigned to the shear corner piece unit along the radial, circumferential and shear directions of the fuselage: Set the tensile and compressive modulus of the shear corner piece element along the radial direction of the fuselage, the shear modulus in the shear direction, and the tensile and compressive modulus along the circumferential direction of the fuselage.

[0010] The present invention also provides a finite element modeling system for an aircraft floating frame structure, comprising: The first modeling module is used to establish a first round of finite element models according to a known fuselage structure model, wherein the first round of finite element models includes skin units, frame units, shear angle unit units and long stringer units, wherein the skin units, frame units, shear angle unit units and long stringer units share a common node; The second modeling module is used to assign unit attributes to the skin unit, frame unit, shear angle unit and long stringer unit in the first round of finite element model to obtain the second round of finite element model; The third modeling module is used to set the material of the shear corner unit in the second round of finite element model as anisotropic material, and to set different material properties of the shear corner unit along the radial, circumferential and shear directions of the fuselage to obtain the finite element model of the aircraft floating frame structure.

[0011] The present invention also provides a method for calculating stress of an aircraft floating frame structure, comprising the following process: Loads and constraints are applied to the aircraft floating frame structure finite element model obtained by the aircraft floating frame structure finite element modeling method described above in the present invention, and calculations are performed to obtain stress values ​​of skin units, frame units, shear angle unit and long stringer unit.

[0012] The present invention also provides an electronic device, comprising: one or more processors; a storage device having one or more programs stored thereon; When the one or more programs are executed by the one or more processors, the one or more processors implement the aircraft floating frame structure finite element modeling method of the present invention as described above.

[0013] The present invention also provides a storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the aircraft floating frame structure finite element modeling method of the present invention as described above.

[0014] The present invention also provides a computer program product, which includes computer instructions, and is characterized in that the computer instructions instruct a computer to execute the aircraft floating frame structure finite element modeling method of the present invention as described above.

[0015] The present invention has the following beneficial effects: The present invention establishes an overall finite element model for the aircraft floating frame structure model, and the skin unit, frame unit, shear angle unit and long stringer unit are simplified to shell units, and all units have common nodes; then the unit properties of all units are set; then for the shear angle unit, the material properties are modified to be anisotropic, and the shear angle unit is set to have different material properties along the radial, circumferential and shear directions of the fuselage, and the resulting model is the final aircraft floating frame structure finite element model. By applying loads and constraints to the model obtained by the modeling method of the present invention and submitting it for calculation, the stress value of each unit can be obtained. It can be seen that the technical solution of the present invention is simple in principle and can be implemented on all computing software. At the same time, it is easy to implement and can be applied to the analysis and calculation of the overall finite element model of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 It is a model diagram of a known aircraft floating frame structure used in an embodiment of the present invention.

[0018] Figure 2 It is a finite element model diagram of an aircraft frame structure established in an embodiment of the present invention.

[0019] Figure 3 It is a stress cloud diagram calculated by the finite element model of the floating frame structure in the embodiment of the present invention.

[0020] Figure 4 Schematic diagram of the hoop stress of the shear angle piece in the embodiment of the present invention.

[0021] Figure 5 Schematic diagram of radial stress of the shear angle piece in an embodiment of the present invention.

[0022] Figure 6 Schematic diagram of shear stress of shear angle piece in an embodiment of the present invention.

[0023] Explanation of numbers in the figure: 1 skin, 2 frame, 3 long stringer, 4 shear corner piece. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] See also Figure 1 The typical structure of the fuselage includes skin 1, frame 2, long stringer 3 and shear corner piece 4. The example described in the present invention is a simplified method example of a typical fuselage floating frame shear corner piece in the present invention, rather than a simplified example of all fuselage frames. According to this example, it is easy to realize a simplified finite element model of all types of fuselage floating frames. The examples described below with reference to the accompanying drawings are intended to be used to explain the present invention, and should not be understood as limiting the present invention.

[0026] The finite element modeling method of the aircraft floating frame structure of the present invention comprises the following steps: 1) In a known typical fuselage structure, a first round of finite element models is established, wherein the first round of finite element models includes skin units, frame units, shear angle unit units and long stringer units, wherein the skin units, frame units, shear angle unit units and long stringer units share a common node; 2) Assigning unit attributes to the skin unit, frame unit, shear angle unit and long stringer unit in the first round of finite element model to obtain the second round of finite element model; 3) The material of the shear corner piece unit in the second round of finite element model is set to anisotropic material, and different material properties are set along the radial, circumferential and shear directions of the fuselage to give the shear corner piece unit different material properties, so as to obtain the third round of finite element model, i.e., the finite element model of the aircraft floating frame structure of the present invention.

[0027] In order to further calculate the stress of the aircraft floating frame structure, loads and constraints are further applied to the third round of finite element model to form a finite element model for stress calculation of the aircraft floating frame structure; the finite element model for stress calculation of the aircraft floating frame structure is then submitted for calculation, and the stress values ​​of the skin unit, frame unit, shear corner unit and long stringer unit are output, wherein the calculation results of the shear corner include the unit force and stress value of the shear corner along the radial, circumferential and shear directions of the fuselage.

[0028] Example The aircraft floating frame structure stress calculation method of this embodiment includes the following steps: Step 1: See Figure 1 The known typical fuselage structural model includes skin 1, frame 2, shear angle piece 4 and long stringer 3, wherein the units corresponding to skin 1, frame 2, shear angle piece 4 and long stringer 3 are skin unit, frame unit, shear angle piece unit and long stringer unit respectively. In the known typical fuselage structural model, it is determined that the shear angle piece 4 is connected to the skin 1 at one end along the radial direction of the fuselage and connected to the frame 2 at the other end, and at least one end along the circumferential direction of the fuselage is free and not connected to any structure; Step 2: For the typical fuselage structure model known in step 1, establish a finite element model to ensure that all units (i.e. skin units, frame units, shear corner units and long stringers) have common nodes (i.e. skin units, frame units, shear corner units and long stringers share a node at the connection point) to form the first round of finite element model, see Figure 2 ; Step 3: Assign unit attributes (including material attributes and geometric attributes) to the first round of finite element model established in step 2, as follows: the thickness of the skin unit is 1.6mm, the thickness of the frame web unit is 1.6m, and the cross-sectional area of ​​the frame edge strip unit is 30mm 2 , the unit area of ​​the long truss is 100mm 2 , the thickness of the shear angle piece unit is 1.2mm; and the material properties of the skin unit, frame unit (including frame web unit and frame edge strip unit), long stringer unit and shear angle piece unit are assigned to form the second round of finite element model, in which the elastic modulus of the skin unit, frame unit, shear angle piece unit and long stringer unit material is 71000MPa, and the Poisson's ratio is 0.3; Step 4: Modify the second round of finite element model, change the material of the shear corner unit in the second round of finite element model to anisotropic material, that is, give the material a tensile and compressive modulus of 71000MPa along the radial direction (E11) of the fuselage, a shear modulus of 27307MPa along the shear direction (E12), and a tensile and compressive modulus of 10MPa along the circumferential direction (E22) of the fuselage, to form the third round of finite element model; Step 5: Apply loads and constraints to the third round of finite element model to form the final finite element model of the calculation; Step 6: Submit the final finite element model for calculation and output the calculation results of the finite element model, including the stress values ​​of all units, see Figure 3 ; Step 7: View the radial calculated stresses of the shear corner element (see Figure 5 ), hoop stress calculation (see Figure 4 ) and shear stress calculation (see Figure 6 ). If the calculated circumferential stress is very small, it indicates that the simplification is correct. Figure 4 , Figure 5 and Figure 6 The calculation results of the scheme of the present invention are reliable.

[0029] From the above scheme, it can be seen that the method provided by the present invention realizes the accurate force transmission form and stiffness setting of the shear angle piece in each direction, thereby ensuring the accurate calculation result of the fuselage frame structure. The present invention can not only ensure the accurate force transmission of the fuselage frame structure, but also is suitable for the overall finite element model of the aircraft.

[0030] The present invention also provides an aircraft floating frame structure finite element modeling system, comprising: The first modeling module is used to establish a first round of finite element models according to a known fuselage structure model, wherein the first round of finite element models includes skin units, frame units, shear angle unit units and long stringer units, wherein the skin units, frame units, shear angle unit units and long stringer units share a common node; The second modeling module is used to assign unit attributes to the skin unit, frame unit, shear angle unit and long stringer unit in the first round of finite element model to obtain the second round of finite element model; The third modeling module is used to set the material of the shear corner unit in the second round of finite element model as anisotropic material, and to set different material properties of the shear corner unit along the radial, circumferential and shear directions of the fuselage to obtain the finite element model of the aircraft floating frame structure.

[0031] Furthermore, in the above-mentioned embodiment of the present invention, the known fuselage structure model includes a skin 1, a frame 2, a shear corner piece 4 and a long stringer 3, and the skin 1, the frame 2 and the long stringer 3 are connected, wherein the shear corner piece 4 is connected to the skin 1 at one end along the radial direction of the fuselage, and is connected to the frame 2 at the other end, and at least one end of the shear corner piece 4 along the circumferential direction of the fuselage is a free end.

[0032] In the above embodiment of the present invention, when the second modeling module assigns unit attributes to the skin units, frame units, shear corner piece units and long stringer units in the first round of finite element models, it is necessary to assign material attributes and geometric attributes to the skin units, frame units, shear corner piece units and long stringer units, and in the second round of finite element models, the material attributes of the skin units, frame units, shear corner piece units and long stringer units are the same, and are all assigned isotropic material attributes. In a specific implementation, according to the shape characteristics of the skin unit, frame unit, shear corner piece unit and long stringer unit, when assigning geometric properties to the skin unit, frame unit, shear corner piece unit and long stringer unit: assign thickness dimensions to the skin unit, assign thickness dimensions to the web of the frame unit, assign cross-sectional area dimensions to the frame edge strip of the frame unit, assign area dimensions to the long stringer unit, and assign thickness dimensions to the shear corner piece unit. Of course, those skilled in the art can also assign other dimensions according to the shape characteristics of the skin unit, frame unit, shear corner piece unit and long stringer unit in different models, and the present invention does not make specific limitations; the material properties of the skin unit, frame unit, shear corner piece unit and long stringer unit are all assigned elastic modulus and Poisson's ratio. Of course, those skilled in the art can also assign other parameters to the material properties of the skin unit, frame unit, shear corner piece unit and long stringer unit according to the material characteristics of the skin unit, frame unit, shear corner piece unit and long stringer unit in different models, and the present invention does not make specific limitations.

[0033] In the above embodiment of the present invention, the third modeling module sets the material of the shear corner piece unit in the second round of finite element model as anisotropic material, and sets different material properties of the shear corner piece unit along the radial, circumferential and shear directions of the fuselage: specifically, the tensile and compressive modulus of the shear corner piece unit along the radial direction of the fuselage, the shear modulus in the shear direction, and the tensile and compressive modulus along the circumferential direction of the fuselage are set.

[0034] The embodiments of the present invention also provide corresponding electronic devices and computer-readable storage media for implementing the solutions provided by the embodiments of the present invention.

[0035] The device includes a memory and a processor, the memory is used to store instructions or codes, and the processor is used to execute the instructions or codes so that the device executes the aircraft floating frame structure finite element modeling method described in any embodiment of the present application.

[0036] In this embodiment, when the processor executes the computer program stored in the memory, the following process can be specifically implemented: according to the known fuselage structure model, a first round of finite element models are established, the first round of finite element models including skin units, frame units, shear corner units and long stringer units, wherein the skin units, frame units, shear corner units and long stringer units share nodes; unit attributes are assigned to the skin units, frame units, shear corner units and long stringer units in the first round of finite element models to obtain a second round of finite element models; the material of the shear corner unit in the second round of finite element models is set to anisotropic material, and different material properties are assigned to the shear corner unit along the radial, circumferential and shear directions of the fuselage to obtain a finite element model of the aircraft floating frame structure.

[0037] The storage medium stores a computer program, wherein the computer program, when executed by the processor, implements the aircraft floating frame structure finite element modeling method described in any embodiment of the present application.

[0038] Another object of an embodiment of the present invention is to provide a computer program product, wherein the computer program product includes computer instructions, and the computer instructions instruct a computer to execute the aircraft floating frame structure finite element modeling method.

[0039] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0040] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0041] The present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, readable storage media, optical storage, etc.) containing computer-usable program codes.

[0042] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A finite element modeling method for an aircraft floating frame structure, characterized in that: The process includes the following: According to the known fuselage structure model, a first round of finite element models are established, wherein the first round of finite element models include skin units, frame units, shear corner unit units and long stringer units, wherein the skin units, frame units, shear corner unit units and long stringer units share a common node; Assigning unit attributes to the skin unit, frame unit, shear angle unit and long stringer unit in the first round of finite element model to obtain a second round of finite element model; The material of the shear corner unit in the second round of finite element model is set as anisotropic material, and different material properties are given to the shear corner unit along the radial, circumferential and shear directions of the fuselage to obtain the finite element model of the aircraft floating frame structure.

2. The finite element modeling method for an aircraft floating frame structure according to claim 1, characterized in that: The known fuselage structure model comprises a skin (1), a frame (2), a shear corner piece (4) and a long stringer (3); the skin (1), the frame (2) and the long stringer (3) are connected, wherein the shear corner piece (4) is connected to the skin (1) at one end along the radial direction of the fuselage and is connected to the frame (2) at the other end, and at least one end of the shear corner piece (4) along the circumferential direction of the fuselage is a free end.

3. The finite element modeling method for an aircraft floating frame structure according to claim 1, characterized in that: When assigning unit attributes to the skin unit, frame unit, shear angle unit and stringer unit in the first round of finite element model, the unit attributes include material attributes and geometric attributes.

4. The finite element modeling method for an aircraft floating frame structure according to claim 3, characterized in that: When assigning element properties to the skin elements, frame elements, shear angle elements, and stringer elements in the first round of finite element models: The geometric properties include: the thickness of the skin unit, the thickness of the web of the frame unit and the cross-sectional area of ​​the frame edge strip of the frame unit, the area of ​​the long stringer unit, and the thickness of the shear corner piece unit; Material properties include elastic modulus and Poisson's ratio.

5. The finite element modeling method for an aircraft floating frame structure according to claim 1, characterized in that: When the material of the shear corner piece element in the second round of finite element model is set as anisotropic material, and different material properties are assigned to the shear corner piece element along the radial, circumferential and shear directions of the fuselage: Set the tensile and compressive modulus of the shear corner piece element along the radial direction of the fuselage, the shear modulus in the shear direction, and the tensile and compressive modulus along the circumferential direction of the fuselage.

6. A finite element modeling system for aircraft floating frame structure, characterized in that: include: The first modeling module is used to establish a first round of finite element models according to a known fuselage structure model, wherein the first round of finite element models includes skin units, frame units, shear angle unit units and long stringer units, wherein the skin units, frame units, shear angle unit units and long stringer units share a common node; The second modeling module is used to assign unit attributes to the skin unit, frame unit, shear angle unit and long stringer unit in the first round of finite element model to obtain the second round of finite element model; The third modeling module is used to set the material of the shear corner unit in the second round of finite element model as anisotropic material, and to set different material properties of the shear corner unit along the radial, circumferential and shear directions of the fuselage to obtain the finite element model of the aircraft floating frame structure.

7. A method for calculating stress of an aircraft floating frame structure, characterized in that: The process includes the following: Loads and constraints are applied to the aircraft floating frame structure finite element model obtained by the aircraft floating frame structure finite element modeling method described in any one of claims 1 to 5, and calculations are performed to obtain stress values ​​of skin units, frame units, shear angle unit units and long stringer units.

8. An electronic device, characterized in that: include: one or more processors; a storage device having one or more programs stored thereon; When the one or more programs are executed by the one or more processors, the one or more processors implement the aircraft floating frame structure finite element modeling method according to any one of claims 1 to 5.

9. A storage medium, characterized in that: A computer program is stored thereon, wherein when the computer program is executed by a processor, the finite element modeling method for an aircraft floating frame structure according to any one of claims 1 to 5 is implemented.

10. A computer program product, comprising computer instructions, characterized in that: The computer instructions instruct the computer to execute the aircraft floating frame structure finite element modeling method according to any one of claims 1 to 5.

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