A method for designing and analyzing a helicopter outrigger

Abstract

The present application belongs to the field of helicopter structure strength design, and relates to a design analysis method of a helicopter overhanging equipment support. The method comprises the following steps: determining the positions of each interface of the helicopter overhanging equipment by analyzing the proportion of each direction component of the aerodynamic load and the inertial load under the severe load condition and the bearing capacity of the installation interface of the fuselage; designing the load transmission path and the initial main body transmission structure according to the positions of each interface, the aerodynamic load and the inertial load, and performing topology optimization on the initial main body transmission structure; and finally completing the design of the overhanging equipment support by performing detail size optimization according to the strength requirement and the dynamics requirement.

Description

Technical Field

[0001] This invention belongs to the field of helicopter structural strength design and relates to a design and analysis method for helicopter outrigger equipment brackets. Background Technology

[0002] To meet the requirements of different helicopter flight missions, various mission equipment needs to be installed on the outside of the helicopter. Among these, the installation design of equipment installed on the outside of the helicopter is particularly complex. When the equipment is located on the outside of the helicopter, it must withstand aerodynamic loads and inertial loads during flight, resulting in complex load conditions. At the same time, it is necessary to find a suitable interface location on the helicopter fuselage and design the force transmission path of the equipment bracket. How to design a lightweight and efficient external equipment bracket that meets the strength and dynamic requirements has become a challenge in the design of helicopter equipment installation. Summary of the Invention

[0003] The purpose of this invention is to provide a design and analysis method for helicopter outrigger support, establish a structural strength design process for outrigger support, and combine structural topology optimization and dimensional optimization design ideas to achieve a lightweight, manufacturable outrigger support design that meets strength and dynamic requirements. This design method enables rapid design of outrigger support.

[0004] The technical solution of this invention:

[0005] A design and analysis method for a helicopter extendable equipment bracket includes:

[0006] By analyzing the proportion of aerodynamic and inertial load components and the load-bearing capacity of the fuselage mounting interface under severe load conditions, the positions of each interface of the helicopter's external equipment are determined.

[0007] Based on the location of each interface, aerodynamic load and inertial load, the load transmission path and the initial main force transmission structure are designed, and the topology of the initial main force transmission structure is optimized.

[0008] Finally, based on strength and dynamic requirements, detailed dimensional optimization was completed, and the design of the extended equipment bracket was finalized.

[0009] By analyzing the proportions of aerodynamic and inertial load components under severe load conditions and the load-bearing capacity of the fuselage mounting interfaces, the locations of various interfaces for helicopter extended equipment are determined, including:

[0010] Based on the location of the helicopter's extended equipment, obtain the aerodynamic and inertial loads on the extended equipment affected by the helicopter's shape;

[0011] For aerodynamic or inertial loads, the triaxial force F of a load under each working condition is considered. X F Y F Z and the combined force FHE The maximum value is selected for the target, and the working condition corresponding to the maximum value is designed as a severe load condition.

[0012] Based on the location of the helicopter's extended equipment (X0, Y0, Z0), the initial interface locations (X1, Y1, Z1), (X2, Y2, Z2)...(X i Y i Z i Under various severe load conditions, load decomposition is performed to obtain the constraint loads (F) at each interface location. Xi F Yi F Zi );

[0013] By comparing the constraint loads with the helicopter fuselage's load-bearing capacity, if the constraint loads exceed the helicopter fuselage's load-bearing capacity, the solution is not feasible, and the interface locations need to be replanned until all constraint loads are no greater than the helicopter fuselage's load-bearing capacity.

[0014] Based on the location of each interface, aerodynamic loads, and inertial loads, the load transmission path and the initial main load transmission structure are designed, including:

[0015] The location of the helicopter extension equipment is taken as the loading point, and the m planned interface locations of the helicopter extension equipment are taken as the m interface constraint points.

[0016] Based on the loading point, m interface constraint points, and the connection interface of the helicopter fuselage, and in accordance with the requirements of manufacturability and load transfer rationality, the initial main force transmission structure is designed. The initial main force transmission structure is an integral structure or a box structure composed of a strut structure and a main support structure. Among them, the strut structure acts as a two-force member to transmit axial tensile and compressive loads; the main support structure bears and transmits bending moment and dynamic force in the support plane; and the box structure bears all aerodynamic loads and inertial loads.

[0017] Aerodynamic and inertial loads are applied to the main support structure to obtain the load transmission path.

[0018] For the box structure, topology optimization is performed on the initial main force transmission structure, including:

[0019] Finite element modeling of the box structure;

[0020] The constraint method and loading point load of the box structure are obtained by load decomposition. The element stiffness of the model is used as the design variable, the preset stress of the box structure is used as the constraint condition, and the mass of the box structure is used as the optimization objective. Iterative analysis is carried out by combining topology optimization algorithm to obtain the topology optimization result.

[0021] For the overall structure, topology optimization is performed on the initial main force transmission structure, including:

[0022] Finite element modeling of the main support structure;

[0023] The overall structural constraint method and loading point load are obtained by decomposing the load. The loading point load component of the strut structure is deducted to obtain the main support structure constraint method and loading point load.

[0024] Using the element stiffness of the model as the design variable, the preset stress of the main support structure as the constraint condition, and the mass of the main support structure as the optimization objective, iterative analysis is performed using a topology optimization algorithm to obtain the topology optimization results.

[0025] In the above optimization process, the minimum optimization size constraint is set by the manufacturability.

[0026] Based on the final optimization of detailed dimensions according to strength and dynamic requirements, the design of the extended equipment bracket was completed, including:

[0027] Based on the topology optimization results, the structural thickness is used as the optimization variable, and the thickness of each typical section of the structure is used as the discrete variable. The thickness range is [t1, t2], and the interval between values ​​is Δt. Then, the sample horizontal point N = (t2 - t1)Δt is used for strength optimization design.

[0028] The constraint is the stress resulting from the topology optimization, and the optimization objective is the mass of the helicopter extension equipment support.

[0029] Simultaneously, structural dynamics characteristics analysis was performed on the strength-optimized structure to complete the final structural design.

[0030] The beneficial effects of this invention are: the analytical method can improve the design efficiency of equipment extension brackets, optimize the structural design, meet the requirements of strength and dynamics while maintaining a light structural weight, and can be applied to the design of similar equipment extension brackets. Attached Figure Description

[0031] Figure 1 This is a flowchart of the overall technical solution.

[0032] Figure 2 This is a schematic diagram of the interface scheme.

[0033] Figure 3 This is a schematic diagram of topology optimization.

[0034] Figure 4 This is a schematic diagram for size optimization.

[0035] Figure 5 This is a schematic diagram of the support structure. 1-Strut; 2-Support; 3-Arm. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] This method is a design and analysis approach for helicopter outrigger equipment brackets. By analyzing the proportions of load components in each direction and the load-bearing capacity of the fuselage mounting interface, it designs the load transmission path and the main load transmission structure. Topology optimization is performed on the main structure, and finally, detailed dimensional optimization is completed based on strength and dynamic requirements, thus finalizing the design of the outrigger equipment bracket. Figure 1 As shown, the main steps of the method are as follows:

[0038] (1) Based on the position of the installed equipment on the machine body, obtain the aerodynamic load and inertial load of the equipment, and based on the triaxial force F under each working condition. X F Y F Z and the combined force F HE The maximum value is selected as the target and designed as a severe load condition;

[0039] (2) Based on the equipment installation point location (X0, Y0, Z0), the initial interface locations are (X1, Y1, Z1), (X2, Y2, Z2)...(X i Y i Z i The load decomposition calculation must satisfy the six-force equation system.

[0040] Analysis yields the constraint loads (F) at each interface location. Xi F Yi F Zi If the constraint load is greater than the bearing capacity of the supporting structure, the solution is not feasible and the interface positions need to be replanned so that all constraint loads are not greater than the bearing capacity of the supporting structure.

[0041] (3) Select the configuration of the support structure according to the design requirements of processability and maintainability, and analyze and design the force transmission route according to the load and interface position.

[0042] (4) Obtain the main structure constraint method and loading point load based on the load decomposition, and express it using the element stiffness as the design variable and the element equivalent stiffness:

[0043] K′(ρ)=ρ P K

[0044] In the formula, K′ is the equivalent stiffness of the element, K is the true stiffness of the element, ρ is the density, and P is the penalty function coefficient.

[0045] Using stress σ as a constraint and mass M as the optimization objective, iterative analysis is performed using an optimization algorithm, while setting minimum optimization size constraints based on manufacturability.

[0046] Based on the topology optimization results, a preliminary structural design is carried out.

[0047] (5) Based on the given preliminary structural form, the structural thickness is used as the optimization variable. The thickness of each typical section of the structure is a discrete variable with a range of values ​​of [t1, t2] and an interval of t. Then, the sample level point N = (t2-t1)t is used for strength optimization design.

[0048] Using stress σ as a constraint and mass M as the optimization objective, iterative analysis is performed using an optimization algorithm.

[0049] Simultaneously, structural dynamics analysis is conducted to complete the final structural design.

[0050] Example Application

[0051] (1) Obtain the aerodynamic load and inertial load of the added equipment, and filter by severe load in all directions to obtain the severe load conditions as shown in Table 1.

[0052] Table 1

[0053]

[0054]

[0055] (2) Load distribution analysis is performed based on severe load conditions and the initially selected interface locations.

[0056] Load distribution analysis can be performed using either engineering algorithms or the finite element method. The engineering algorithm solves the problem using a system of six simultaneous force equations, where rotational degrees of freedom are released at the connection points. For statically indeterminate problems, it can be assumed that the stiffness is the same in the corresponding degrees of freedom, meaning the constraint loads at the connection points in that direction are the same. The finite element method uses RBE3 elements for load distribution at the connection points. The loads on the equipment are applied to the master nodes, while the slave nodes are located at the connection points and their rotational degrees of freedom are released. The results of the load distribution and load-bearing capacity comparison are shown in Table 2.

[0057] Table 2

[0058] Interface location X(N) Y(N) Z(N) Resultant force (N) Bearing capacity of supporting structure (N) Point A 5023 1345 0 5200 12000 Point B 9000 3500 -1000 9708 21000 Point C -9000 2900 -1000 9508 21000

[0059] The interface constraint loads are compared and analyzed with the bearing capacity of the supporting structure. Based on the condition of meeting the structural bearing capacity, the constraint loads of the final interface design scheme are selected, such as... Figure 2 As shown.

[0060] Point P is the loading point, and points A, B, and C are interface constraint points.

[0061] (3) Based on the process, the equipment support adopts an integral structure or a box structure composed of a strut structure and a main support structure. The integral structure has fewer connection interfaces with the machine body support structure and is used when the equipment support needs to be disassembled or replaced. The box structure has more connection interfaces with the machine body support structure and in most cases, it also needs to be connected by rivets. It is used when the equipment support does not need to be disassembled or replaced.

[0062] Based on the feasibility of manufacturing and the rationality of load transmission, the structure is divided into a strut structure and a main support structure, in which the strut structure acts as a two-force member to transmit axial tensile and compressive loads.

[0063] Force transmission analysis is performed to obtain bending moment loads in all directions based on the loads at the equipment and the distances from the equipment to the interface constraint points:

[0064] The MX load is mainly balanced by the torque formed by the Y-direction constraint loads at points A and B and the Y-direction constraint load at point C;

[0065] The MY load is mainly balanced by the torque formed by the X-direction constraint loads at points A and B and the X-direction constraint load at point C;

[0066] The MZ load is mainly balanced by the torque formed by the X-direction constraint load at point A and the X-direction constraint loads at points B and C.

[0067] (4) The main support structure was selected for topology optimization design. Based on the material selection process, the shape and dimensions of the main support were established using 3D modeling software. The structure was divided into a hexahedral solid finite element mesh, and the structural boundaries and loading conditions were constrained. Minimum size constraints and face symmetry constraints were applied to meet the process requirements, and stress constraints were applied to meet the strength requirements. The support structure topology optimization was performed using optimization analysis software. The optimization results are as follows: Figure 3 As shown.

[0068] The optimization method adopts the variable density method, which uses the density function form of continuous variables to express the correspondence between the relative density of the unit and the elastic modulus of the material support. The material distribution within the design range is obtained through iterative calculation, and this material distribution is the optimal force transmission path.

[0069] Based on the topology optimization results, the positions of the elements with higher topology optimization density are transformed by using a flange plus web form, thus completing the preliminary scheme determination.

[0070] (5) Based on the preliminary structural design, the web and flanges of each part of the structure are divided into regions, thickness optimization variables are set, and dimensional optimization is performed with structural stress as a constraint and mass M as the optimization objective. Figure 4 As shown.

[0071] Sensitivity analysis is required during the size optimization process to obtain the impact of structural thickness changes on stress, mass, stiffness, etc., and then obtain the final optimized size.

[0072] Strength analysis is performed to determine the structural dimensions and connection design of each part. The structure must meet the requirement that the structural stress does not exceed the allowable stress limit of the material, the connection compression and pull-out meet the allowable strength requirements, and the structure does not become unstable.

[0073] Perform dynamic analysis of the equipment and support structure. The structural modal frequencies analyzed must avoid the first passing frequency of the helicopter rotor in order to meet the dynamic design requirements.

[0074] The final bracket design is completed, such as Figure 5 As shown.

[0075] The above description is merely a specific embodiment of the present invention, providing a detailed description of the invention. Parts not covered herein are conventional techniques. However, the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method of design analysis of a helicopter external store pylon, characterized in that, Comprise: Determine the interface position of the helicopter external equipment by analyzing the proportion of each component of the aerodynamic load and the inertia load under severe load conditions and the bearing capacity of the installation interface of the fuselage; Design the load transmission path and the initial main force transmission structure according to the interface position, aerodynamic load and inertia load, and topologically optimize the initial main force transmission structure; Finally, complete the detail size optimization according to the strength requirement and the dynamics requirement, and complete the design of the external equipment support; Design the load transmission path and the initial main force transmission structure according to the interface position, aerodynamic load and inertia load, comprising: Take the position of the helicopter external equipment as a loading point, and take the planned m interface positions of the helicopter external equipment as m interface constraint points; According to the loading point, the m interface constraint points, and the connecting interface of the helicopter fuselage, design the initial main force transmission structure according to the process and load transmission rationality requirements. The initial main force transmission structure is a whole structure or a box structure composed of a strut structure and a main support structure. The strut structure is used as a two-force rod to transmit axial tensile and compressive load. The main support structure bears and transmits the bending moment and translation force in the support plane. The box structure bears all aerodynamic loads and inertia loads. Apply the aerodynamic load and the inertia load to the main support structure to obtain the load transmission path.

2. The method of claim 1, wherein, Determine the interface position of the helicopter external equipment by analyzing the proportion of each component of the aerodynamic load and the inertia load under severe load conditions and the bearing capacity of the installation interface of the fuselage, comprising: According to the position of the helicopter external equipment, obtain the aerodynamic load and the inertia load of the external equipment affected by the shape of the helicopter; For aerodynamic load or inertial load, according to three-direction force F X 、 F Y 、 F Z and resultant force FHE as the target for maximum screening, and the working condition corresponding to the maximum value is designed as a serious load working condition; According to the position (X0, Y0, Z0) of the helicopter outrigger device, the preliminary position (X1, Y1, Z1) of the interface, (X2, Y2, Z2) … (X i , Y i , Z i ), load decomposition is carried out under each severe load condition to obtain the constraint loads (F Xi , F Yi , F Zi ) of each interface position; Compare the constraint load with the bearing capacity of the helicopter fuselage. If the constraint load is greater than the bearing capacity of the helicopter fuselage, the scheme is not feasible, and the interface position needs to be re-planned until all constraint loads are not greater than the bearing capacity of the helicopter fuselage.

3. The method of claim 1, wherein, For the box structure, topologically optimize the initial main force transmission structure, comprising: Carry out finite element modeling on the box structure; According to the load decomposition, obtain the constraint mode of the box structure and the loading point load. Take the unit stiffness of the model as the design variable, take the preset stress of the box structure as the constraint condition, take the mass of the box structure as the optimization target, and combine the topological optimization algorithm to carry out iterative analysis to obtain the topological optimization result.

4. The method of claim 1, wherein, For the whole structure, topologically optimize the initial main force transmission structure, comprising: Carry out finite element modeling on the main support structure; According to the load decomposition, obtain the constraint mode of the whole structure and the loading point load, and deduct the loading point load component of the strut structure to obtain the constraint mode of the main support structure and the loading point load; Take the unit stiffness of the model as the design variable, take the preset stress of the main support structure as the constraint condition, take the mass of the main support structure as the optimization target, combine the topological optimization algorithm to carry out iterative analysis, and obtain the topological optimization result.

5. The method according to claim 3 or 4, characterized in that, In the above topological optimization process, the minimum optimization size constraint is set by the process.

6. The method according to claim 3 or 4, characterized in that, Finally, complete the detail size optimization according to the strength requirement and the dynamics requirement, and complete the design of the external equipment support, comprising: According to the topology optimization result, taking the thickness size of the structure as an optimization variable, taking the thickness of each typical section of the structure as a discrete variable, the thickness value range is [t1, t2], and the value interval is Δt, then the sample horizontal point N = (t2-t1) / Δt, and strength optimization design is performed; Wherein, the constraint condition is the stress of the topology optimization result, and the optimization target is the quality of the helicopter overhanging equipment support; Meanwhile, the structure dynamics characteristic analysis is performed on the strength optimized structure, and the final structure design is completed.

7. A computer-readable storage medium having stored thereon a computer program, characterized in that The computer program is executed by a processor to implement the method of any one of claims 1-6.

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