Mounting joint for externally-hung electric winch of helicopter and design method of mounting joint

Abstract

The invention provides a helicopter plug-in electric winch mounting joint and a design method thereof. Comprising the following steps that the load working condition of the externally-hung electric winch in the using state is determined according to a hanging scheme; secondly, according to the load working conditions in the first step, a load force transmission path is constructed, and according to the load force transmission path, an initial structure configuration of the externally-hung electric winch mounting connector is designed; a finite element simplified model is established according to the initial structure configuration, the simplified model comprises the initial structure configuration of the installation joint and a machine body structure connected with the initial structure configuration, constraints in all directions are applied to the finite element simplified model according to the actual use state, and loads are applied; analyzing and calculating through a finite element simplified model, and determining the section form and size of each component unit of the initial structural configuration according to a stress control principle; reinforcing structures are additionally arranged on the basis of the initial structural configuration of the mounting connector according to the connecting point of the mounting connector and the machine body and the connecting position of the mounting connector and the externally-hung electric winch connecting piece, and the reinforcing configuration of the mounting connector is obtained; and establishing a local detail finite element calculation model according to the reinforcement configuration, and determining the section form and size of each component unit of the reinforcement configuration according to a stress control principle.

Description

Technical Field

[0001] This invention belongs to the field of helicopter structural strength design technology, specifically relating to a helicopter external electric winch mounting joint and its design method. Background Technology

[0002] Externally mounted electric winches play a crucial role in helicopter rescue operations. These winches allow for personnel rescue while the helicopter is hovering, lifting the injured or staff from the ground into the helicopter cabin and quickly transferring trapped individuals onto the helicopter. Externally mounted electric winches can also rapidly deploy rescue supplies and personnel, improving rescue efficiency. Furthermore, helicopter electric winches can perform high-altitude operations and cargo transport, and with the continuous advancement of helicopter technology, they are playing an increasingly important role in a wider range of fields.

[0003] The design and operation of external electric winch mounting structures have high requirements, needing to adapt to the complex flight and rescue environments of helicopters. When designing external electric winch mounting structures, precise strength analysis is required to optimize the force transmission path and reduce weight to improve helicopter operational efficiency.

[0004] In previous helicopter models, the external winch mounting structure was usually located outside the fuselage, which affected the helicopter's aerodynamic performance and also somewhat impacted its aesthetic appearance. Summary of the Invention

[0005] Purpose of the invention: To provide a helicopter external electric winch mounting joint and its design method. The mounting joint designed using the method of the present invention is flush with the upper platform of the fuselage, which is beneficial to the aerodynamic performance of the helicopter, maintains the continuity of the helicopter's shape, and facilitates the disassembly, assembly, and maintenance of the external electric winch support.

[0006] To address the aforementioned technical issues, according to a first aspect of the present invention, a design method for a helicopter external electric winch mounting joint is proposed. One end of the external electric winch mounting joint is connected to the helicopter body, and the other end is connected to an external electric winch connector, through which an electric winch is connected. The method includes the following steps: Step 1: Determine the load conditions of the external electric winch under operating conditions based on the hoisting plan; Step 2: Based on the load conditions in Step 1, construct the load transmission path, and design the preliminary structural configuration of the external electric winch installation joint based on the load transmission path. Step 3: Establish a simplified finite element model based on the preliminary structural configuration. The simplified model includes the preliminary structural configuration of the mounting joint and the body structure connected to it. Apply constraints in each direction to the simplified finite element model according to the actual usage conditions, and apply loads. Step 4: Through simplified finite element model analysis and calculation, determine the cross-sectional form and dimensions of each component unit of the preliminary structural configuration according to the stress control principle; Step 5: For the connection points between the installation joint and the machine body, and the connection points between the installation joint and the external electric winch connector, add reinforcing structures based on the initial structural configuration of the installation joint to obtain the reinforced configuration of the installation joint; Step 6: Establish a local detail finite element calculation model based on the reinforced configuration, and determine the cross-sectional form and size of each component element of the reinforced configuration according to the stress control principle.

[0007] In one possible embodiment, in step one, according to the actual usage requirements of the external electric winch for hoisting and transportation, the external electric winch bears a load value of F from the winch assembly, and the line of action of the load is in a cone at a 30º angle to the vertical downward direction of the helicopter.

[0008] In one possible embodiment, in step two, the preliminary structural configuration includes a first flange 1, a second flange 2, a first web 3, a third flange 4, a fourth flange 5, and a second web 6; the middle structure of the first flange 1 is connected to the upper platform of the machine body, the inner side of the first flange 1 is fixedly connected to the upper flange of the inner beam of the machine body, and the outer side of the first flange 1 is connected to the external electric winch connector; the inner side of the second flange 2 is fixedly connected to the lower flange of the inner beam of the machine body, and the outer side of the second flange 2 is connected to the external electric winch connector. The first web plate 3 is fixedly connected to the web plate of the inner beam of the machine body; the upper part of the first web plate 3 is connected to the first flange 1; the lower part of the first web plate 3 is connected to the second flange 2; and the outer side of the first web plate 3 is connected to the external electric winch connector. The third flange 4 is fixedly connected to the upper flange of the outer beam of the machine body. The fourth flange 5 is fixedly connected to the lower flange of the outer beam of the machine body. The second web plate 6 is fixedly connected to the web plate of the outer beam of the machine body. The external electric winch connector 7 is located on the center line of the entire joint structure and is in the form of a pin cylinder.

[0009] In one possible embodiment, in step three, a simplified finite element model is established using the commercial software MSC.Patran. In the preliminary structural configuration, the first flange 1, the second flange 2, the third flange 4, and the fourth flange 5 are simulated using rod elements, and the first web 3 and the second web 6 are simulated using shear elements. The connection between the structures is simulated using a common node method. Constraints in each direction are applied to the finite element model according to the actual situation. The connection between the winch support connector and the mounting joint is simulated using an MPC unit, and a load FORCE is applied.

[0010] In one possible embodiment, in step four, the tensile load of the winch mounting joint flange structural member is read. Compression load Define and optimize the cross-sectional shape and dimensions of the flange structure; read the shear load of the web structure of the winch installation structure. Define and optimize the web form and dimensions; The dimensions of the first flange 1, the second flange 2, the third flange 4, and the fourth flange 5 are determined by tensile strength and compressive strength; The tensile strengths of the first flange 1, the second flange 2, the third flange 4, and the fourth flange 5 satisfy the following formula:

[0011] The compressive strengths of the first flange 1, the second flange 2, the third flange 4, and the fourth flange 5 satisfy the following formula:

[0012] In the formula, A represents the cross-sectional area of ​​the flange or rib. —Critical stress for flange instability —The width of the i-th plate element; —The thickness of the i-th plate element; —The compressive stress of the i-th plate element, with the cutoff value taken as... ; N —The total number of plate elements that make up the cross-section; The dimensions of the first web 3 and the second web 6 are determined by shear stability, and the web shear stress τ satisfies the following formula:

[0013] In the formula, —Critical stress for web instability; —Web thickness; B – Width of the web; k—shear stability coefficient; E – Material elastic modulus; μ — Poisson's ratio of the material.

[0014] In one possible embodiment, in step five, based on the preliminary definition results of the cross-sectional shape and size of the structure described in step four, a finite element calculation model of the local details of the winch installation joint is established, and the detailed dimensions of the external electric winch installation joint are designed. In the local detail finite element calculation model: The overall structure of the external electric winch mounting joint is simulated using shell units. The constraints of the upper platform plate on the winch installation structure are simulated by limiting the in-plane translational degree of freedom of the connection point between the first flange 1 and the body platform plate 9. The constraint conditions of the inner beam on the winch installation structure are simulated by restricting the translational degrees of freedom of the connection points between the first flange 1, the second flange 2, the first web plate 3 and the inner beam 8 of the machine body. The constraint conditions of the outer beam on the winch installation structure are simulated by restricting the translational degrees of freedom of the connection points between the third flange 4, the fourth flange 5, the second web plate 6 and the outer beam 10 of the machine body. The connection between the winch support connector 7 and the winch assembly is simulated by an MPC unit, and a load FORCE is applied. The load application point is the application point of the winch assembly rope.

[0015] Based on the structural dimensions defined in step four, set the element attribute PROPERTY_1 for each structural component in the model and perform calculations; Read the stress value σ of each component, and optimize the size and shape of each component structure according to stress control technology; read the stress distribution cloud map of each component structure, and optimize the position of the ribs. The stress control technique described above requires that the calculated stress σ of the structural component should satisfy the following formula:

[0016] In the formula, σ b The allowable stress for each structural material is taken from the mechanical property data of the materials used in the structure.

[0017] According to a second aspect of the present invention, a helicopter external electric winch mounting joint is provided, which is obtained by the above-mentioned design method for a helicopter external electric winch mounting joint, comprising: a first flange 1, a second flange 2, a first web 3, a third flange 4, a fourth flange 5, and a second web 6. The components of the external electric winch mounting structure are arranged as follows: The middle structure of the first flange 1 is connected to the body platform 9, the inner side of the first flange 1 is fixedly connected to the upper flange of the inner beam 8 of the body, and the outer side of the first flange 1 is connected to the external electric winch connector 7.

[0018] The inner side of the second flange 2 is fixedly connected to the lower flange of the inner beam 8 of the machine body, and the outer side of the second flange 2 is connected to the external electric winch connector 7. The inner side of the first web plate 3 is fixedly connected to the web plate of the inner beam 8 of the machine body, the upper part of the first web plate 3 is connected to the first flange 1, the lower part of the first web plate 3 is connected to the second flange 2, and the outer side of the first web plate 3 is connected to the external electric winch connector 7. The third flange 4 is fixedly connected to the upper flange of the outer beam 10 of the machine body; The fourth flange 5 is fixedly connected to the lower flange of the outer beam 10 of the machine body; The second web plate 6 is fixedly connected to the web plate of the outer beam 10 of the machine body.

[0019] The external electric winch connector 7 is located on the center line of the entire joint structure and is in the form of a pin cylinder.

[0020] In summary, the beneficial effects of the present invention are as follows: This invention provides a load basis for the design of the winch installation structure based on the installation scheme and equipment location of the external electric winch on a helicopter. A finite element calculation model was established, and the definition of the winch installation structure was completed through static strength iterative design, meeting the strength design requirements. The designed winch installation structure is parallel to the upper platform of the helicopter. When the winch is removed, there is no external structure, and it does not affect the aerodynamic performance of the helicopter's shape. Attached Figure Description

[0021] Figure 1 A flowchart illustrating the strength design of an external electric winch mounting joint for a helicopter, provided in this application.

[0022] Figure 2 This application provides a structural configuration diagram of a helicopter external electric winch mounting joint.

[0023] Wherein: 1-first flange 1, 2-second flange 2, 3-first web 3, 4-third flange 4, 5-fourth flange 5, 6-second web 6, 7-external electric winch connector.

[0024] Figure 3 Diagram showing the relative positions of the external electric winch installation connector and surrounding structures.

[0025] Among them: 8-internal beam of the fuselage, 9-platform plate of the fuselage, 10-external beam of the fuselage.

[0026] Figure 4 This is a schematic diagram of the cross-section of flange 1.

[0027] Among them: 11-plate element 1, 12-plate element 2, 13-plate element 3.

[0028] Figure 5 This is a schematic diagram for the experimental verification of a helicopter external electric winch mounting joint structure provided in this application.

[0029] Among them: 14-clamp fixing constraint, 15-external electric winch installation joint test piece, 16-external winch loading simulation piece. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0032] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0034] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0036] First aspect: such as Figure 1As shown, the strength design of a helicopter external electric winch mounting joint includes the following steps: (1) Clarify the load status of the external electric winch under the operating conditions to provide load basis for the structural strength design of the installation joint.

[0037] Based on the design requirements and suspension scheme of the external electric winch, the load conditions of the external electric winch under various operating conditions are clarified, providing calculation load conditions for subsequent structural strength design.

[0038] Based on the actual usage requirements of external electric winch for hoisting and transportation, the load value of the external electric winch from the winch assembly is F=20000N, and the line of action of the load is within a cone at a 30º angle to the vertical downward direction of the helicopter. The severe load conditions are shown in the table below: Table 1 Severe Load Conditions

[0039] (2) Determine the overall configuration and structural layout design of the external electric winch installation joint. In step (1), the load conditions are calculated, load matrices are established under multiple operating conditions, a simplified model of the external electric winch is established, the installation joint and structural strength design of the external electric winch are carried out, and the various components of the external electric winch installation structure are arranged to form a complete load transmission path.

[0040] All components of the external electric winch mounting joint structure are made of metal, including flange 1, flange 2, web, side angle brackets, side T-shaped stiffeners, and the external electric winch connecting structure. The external electric winch is connected to the connecting structure by bolts and transmits the winch's suspended load.

[0041] To simplify structural installation and improve structural weight efficiency, the above-mentioned components are integrated into a single machined structure with continuous transitions between the components.

[0042] The components of the external electric winch mounting structure are arranged as follows: The middle structure of flange 1 is connected to the upper platform of the machine body, the inner side of flange 1 is fixedly connected to the upper flange of the inner beam of the machine body, and the outer side of flange 1 is connected to the external electric winch connector.

[0043] The inner side of flange 2 is fixedly connected to the lower flange of the inner beam of the machine body, and the outer side of flange 2 is connected to the external electric winch connector.

[0044] The inner side of the web plate is fixedly connected to the web plate of the inner beam of the machine body, the upper part of the web plate is connected to flange 1, the lower part of the web plate is connected to flange 2, and the outer side of the web plate is connected to the external electric winch connector.

[0045] The two side angle members are connected to the flange 2 and distributed along the edge of the flange 2, serving as reinforcements for the flange 2.

[0046] Two T-shaped ribs extend from the external electric winch connector, forming a symmetrical structure, and are fixedly connected to the outer beam of the machine body.

[0047] The external electric winch connector is located on the center line of the entire joint structure. It is a pin-shaped connector that connects to flange 1, flange 2, web and T-shaped ribs.

[0048] (3) Establish a preliminary simplified finite element model of the winch installation structure, and apply constraints in each direction to the finite element model according to the actual situation.

[0049] Based on the overall configuration and structural layout design results of the external electric winch installation joint described in step (2), a simplified structural force transmission model is established. The simplified model includes the external electric winch installation joint and the body structure connected to it, wherein the body structure connected to it serves to simulate real constraints in the model.

[0050] A finite element model was established using the commercial software MSC.Patran. In the winch installation joint, all flanges and rib structures were simulated using rod elements, and the web structure was simulated using shear elements. In the body structure connected to the winch installation joint, flanges were simulated using rod elements, and the web and plate structures were simulated using shear elements. The connection between structures was simulated using a common node method. Constraints in each direction were applied to the finite element model according to the actual situation.

[0051] The connection between the winch support connector and the winch assembly is simulated by an MPC unit, and a load FORCE is applied. The load application point is the point of application of the winch assembly rope.

[0052] Based on the actual structure of the machine, the PROPERTY property is set for the machine structure connected to the external electric winch mounting joint in the model.

[0053] Based on engineering design experience, the initial property PROPERTY_0 was set for each structural component of the external electric winch installation joint in the model, and calculations were performed.

[0054] (4) Based on the preliminary finite element simplified model calculation results of the winch installation structure described in step (3), read the load F0 of the flange and rib structure of the winch installation joint, define and optimize the cross-sectional form and size of the flange and rib structure; read the shear load N0 of the web structure of the winch installation structure, define and optimize the web form and size; read the load Fjt and load Pjt of the flange and rib structure of the body structure connected to the external electric winch joint, and verify whether the body structure meets the strength design requirements.

[0055] The flange dimensions are determined by tensile strength and compressive strength.

[0056] The flange tensile strength satisfies the following formula:

[0057] The flange compressive strength satisfies the following formula:

[0058] In the formula, —Critical stress for flange instability —The width of the i-th plate element; —The thickness of the i-th plate element; —The compressive stress of the i-th plate element, with the cutoff value taken as... ; N —The total number of plate elements that make up the cross section.

[0059] The web dimensions are determined by shear stability. The web shear stress τ satisfies the following formula:

[0060] In the formula, —Critical stress for web instability; —Web thickness; B – Width of the web; k—shear stability coefficient; E – Material elastic modulus; μ — Poisson's ratio of the material (5) Establish a finite element calculation model of the local details of the winch installation joint.

[0061] Based on the preliminary definition results of the cross-sectional shape and size of the structure described in step (4), a finite element calculation model of the local details of the winch installation joint is established, and the detailed dimensions of the external electric winch installation joint are designed.

[0062] In the local detail finite element calculation model: The overall structure of the external electric winch installation joint is simulated using shell elements, while the connection between the angle bracket and flange 2 is simulated using beam elements. The constraints of the upper platform plate on the winch installation structure are simulated by constraining the in-plane translational degrees of freedom of the connection point between flange 1 and the upper platform plate. The constraints of the internal beam on the winch installation structure are simulated by limiting the translational degrees of freedom of the connection points between flange 1, flange 2, web and the internal beam of the machine. The constraints of the machine body's external beam on the winch installation structure are simulated by limiting the translational degrees of freedom of the connection point between the T-shaped stiffener and the machine body's external beam.

[0063] The connection between the winch support connector and the winch assembly is simulated by an MPC unit, and a load FORCE is applied. The load application point is the point of application of the winch assembly rope.

[0064] Based on the structural dimensions defined in step (4), set the unit attribute PROPERTY_1 for each structural component in the model and perform calculations.

[0065] (6) Based on the calculation results of the finite element model of the local details of the winch installation joint described in step (5), read the stress value σ of each component, optimize the size and shape of each component structure according to the stress control technology; read the stress distribution cloud map of each component structure, and optimize the position of the ribs.

[0066] The stress control technique described above requires that the calculated stress σ of the structural component should satisfy the following formula:

[0067] In the formula, σ b The allowable stress for each structural material is taken from the mechanical property data of the materials used in the structure.

[0068] (7) Based on the structural dimensions results described in step (6), update the element properties of each component in the finite element calculation model to PROPERTY_2, perform iterative calculations, optimize the structural dimensions of each component according to stress control technology, and meet the strength design requirements.

[0069] Taking flange 1 as an example, the defined dimensions are: Flange 1 has a T-shaped cross-section, with plate element one having a width of 30mm and a thickness of 3mm; plate element two having a width of 30mm and a thickness of 3mm; and plate element three having a width of 20mm and a thickness of 2.5mm.

[0070] Secondly, such as Figures 2-4 As shown, a helicopter external electric winch mounting joint is obtained by the above-mentioned design method for a helicopter external electric winch mounting joint, including: a first flange 1, a second flange 2, a first web 3, a third flange 4, a fourth flange 5, and a second web 6. The components of the external electric winch mounting structure are arranged as follows: The middle structure of the first flange 1 is connected to the body platform 9, the inner side of the first flange 1 is fixedly connected to the upper flange of the inner beam 8 of the body, and the outer side of the first flange 1 is connected to the external electric winch connector 7.

[0071] The inner side of the second flange 2 is fixedly connected to the lower flange of the inner beam 8 of the machine body, and the outer side of the second flange 2 is connected to the external electric winch connector 7. The inner side of the first web plate 3 is fixedly connected to the web plate of the inner beam 8 of the machine body, the upper part of the first web plate 3 is connected to the first flange 1, the lower part of the first web plate 3 is connected to the second flange 2, and the outer side of the first web plate 3 is connected to the external electric winch connector 7. The third flange 4 is fixedly connected to the upper flange of the outer beam 10 of the machine body; The fourth flange 5 is fixedly connected to the lower flange of the outer beam 10 of the machine body; The second web plate 6 is fixedly connected to the web plate of the outer beam 10 of the machine body.

[0072] The external electric winch connector 7 is located on the center line of the entire joint structure and is in the form of a pin cylinder.

[0073] The third aspect involves testing and verifying a helicopter external electric winch mounting connector, including the following steps: (1) Test piece: The helicopter external electric winch installation joint designed above was selected as the test test piece.

[0074] (2) Test specimen support: such as Figure 5 As shown, a fixture is used for support, and the test piece is bolted to the fixture. The loading of the test piece simulates the loading method of the actual installed state.

[0075] (3) Test load: The severe load conditions described in Table 1 of Technical Scheme 1 are selected as the test load conditions. The test load value is F=20000N and the loading direction is according to the load direction of conditions 1 to 5 in Table 1.

[0076] (4) Test loading 1: The severe load conditions [1] to [5] in step (3) were loaded with 67% ultimate load in sequence. After loading to 67% ultimate load, the load was held for 30 seconds and then unloaded to 0. The test pieces under each test condition were visually inspected and no residual deformation was found.

[0077] (5) Test loading 2: The severe load conditions [1] to [5] in step (3) were loaded with 100% ultimate load in sequence. After loading to 100% ultimate load, the load was held for 3 seconds and then unloaded to 0. The test pieces under each test condition were visually inspected and no damage was found.

[0078] The test results show that the installation joint structure of the helicopter external electric winch has passed the test and meets the strength design requirements.

[0079] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A design method for a helicopter external electric winch mounting joint, characterized in that, Includes the following steps: Step 1: Determine the load conditions of the external electric winch under operating conditions based on the hoisting plan; Step 2: Based on the load conditions in Step 1, construct the load transmission path, and design the preliminary structural configuration of the external electric winch installation joint based on the load transmission path. Step 3: Establish a simplified finite element model based on the preliminary structural configuration. The simplified model includes the preliminary structural configuration of the mounting joint and the body structure connected to it. Apply constraints in each direction to the simplified finite element model according to the actual usage conditions, and apply loads. Step 4: Through simplified finite element model analysis and calculation, determine the cross-sectional form and dimensions of each component unit of the preliminary structural configuration according to the stress control principle; Step 5: For the connection points between the installation joint and the machine body, and the connection points between the installation joint and the external electric winch connector, add reinforcing structures based on the initial structural configuration of the installation joint to obtain the reinforced configuration of the installation joint; Step 6: Establish a local detail finite element calculation model based on the reinforced configuration, and determine the cross-sectional form and size of each component element of the reinforced configuration according to the stress control principle.

2. The design method for a helicopter external electric winch mounting joint according to claim 1, characterized in that, In step one, according to the actual usage requirements of the external electric winch for hoisting and transportation, the load value of the external electric winch from the winch assembly is F, and the line of action of the load is in a cone at a 30º angle to the vertical downward direction of the helicopter.

3. The design method for a helicopter external electric winch mounting joint according to claim 1, characterized in that, In step two, the preliminary structural configuration includes a first flange 1, a second flange 2, a first web 3, a third flange 4, a fourth flange 5, and a second web 6. The middle structure of the first flange 1 is connected to the upper platform of the machine body, the inner side of the first flange 1 is fixedly connected to the upper flange of the inner beam of the machine body, and the outer side of the first flange 1 is connected to the external electric winch connector. The inner side of the second flange 2 is fixedly connected to the lower flange of the inner beam of the machine body, and the outer side of the second flange 2 is connected to the external electric winch connector. The inner side of the first web 3 is fixedly connected to the web of the inner beam of the machine body, the upper part of the first web 3 is connected to the first flange 1, the lower part of the first web 3 is connected to the second flange 2, and the outer side of the first web 3 is connected to the external electric winch connector. The third flange 4 is fixedly connected to the upper flange of the outer beam of the machine body. The fourth flange 5 is fixedly connected to the lower flange of the outer beam of the machine body. The second web 6 is fixedly connected to the web of the outer beam of the machine body. The external electric winch connector 7 is located on the center line of the entire joint structure and is in the form of a pin cylinder.

4. A design method for a helicopter external electric winch mounting joint according to claim 1, characterized in that, In step three, a simplified finite element model is established using the commercial software MSC.Patran. In the preliminary structural configuration, the first flange 1, the second flange 2, the third flange 4, and the fourth flange 5 are simulated using rod elements, while the first web 3 and the second web 6 are simulated using shear elements. The connection between the structures is simulated using a common node method. Constraints in each direction are applied to the finite element model according to the actual situation. The connection between the winch support connector and the mounting joint is simulated using an MPC unit, and a load FORCE is applied.

5. The design method for a helicopter external electric winch mounting joint according to claim 1, characterized in that, In step four, the tensile load of the winch mounting joint flange structural member is read. Compression load Define and optimize the cross-sectional shape and dimensions of the flange structure; read the shear load of the web structure of the winch installation structure. Define and optimize the web form and dimensions; The dimensions of the first flange 1, the second flange 2, the third flange 4, and the fourth flange 5 are determined by tensile strength and compressive strength.

6. The design method for a helicopter external electric winch mounting joint according to claim 5, characterized in that, The tensile strengths of the first flange 1, the second flange 2, the third flange 4, and the fourth flange 5 satisfy the following formula: The compressive strengths of the first flange 1, the second flange 2, the third flange 4, and the fourth flange 5 satisfy the following formula: In the formula, A represents the cross-sectional area of ​​the flange or rib. —Critical stress for flange instability —The width of the i-th plate element; —The thickness of the i-th plate element; —The compressive stress of the i-th plate element, with the cutoff value taken as... ; N —The total number of plate elements that make up the cross section.

7. The design method for a helicopter external electric winch mounting joint according to claim 5, characterized in that, The dimensions of the first web 3 and the second web 6 are determined by shear stability, and the web shear stress τ satisfies the following formula: In the formula, —Critical stress for web instability; —Web thickness; B – Width of the web; k—shear stability coefficient; E – Material elastic modulus; μ — Poisson's ratio of the material.

8. The design method for a helicopter external electric winch mounting joint according to claim 1, characterized in that, In step five, based on the preliminary definition results of the cross-sectional shape and size of the structure described in step four, a finite element calculation model of the local details of the winch installation joint is established, and the detailed dimensions of the external electric winch installation joint are designed. In the local detail finite element calculation model: The overall structure of the external electric winch mounting joint is simulated using shell units. The constraints of the upper platform plate on the winch installation structure are simulated by limiting the in-plane translational degree of freedom of the connection point between the first flange 1 and the body platform plate 9. The constraint conditions of the inner beam on the winch installation structure are simulated by restricting the translational degrees of freedom of the connection points between the first flange 1, the second flange 2, the first web plate 3 and the inner beam 8 of the machine body. The constraint conditions of the outer beam on the winch installation structure are simulated by restricting the translational degrees of freedom of the connection points between the third flange 4, the fourth flange 5, the second web plate 6 and the outer beam 10 of the machine body. The connection between the winch support connector 7 and the winch assembly is simulated by an MPC unit, and a load FORCE is applied. The load application point is the application point of the winch assembly rope.

9. The design method for a helicopter external electric winch mounting joint according to claim 1, characterized in that, Based on the structural dimensions defined in step four, set the element attribute PROPERTY_1 for each structural component in the model and perform calculations; Read the stress value σ of each component, and optimize the size and shape of each component structure according to stress control technology; read the stress distribution cloud map of each component structure, and optimize the position of the ribs. The stress control technique described above requires that the calculated stress σ of the structural component should satisfy the following formula: In the formula, σ b The allowable stress for each structural material is taken from the mechanical property data of the materials used in the structure.

10. A helicopter external electric winch mounting connector, characterized in that, The design method for a helicopter external electric winch installation joint according to any one of claims 1-9 includes: a first flange 1, a second flange 2, a first web 3, a third flange 4, a fourth flange 5, and a second web 6. The components of the external electric winch mounting structure are arranged as follows: The middle structure of the first flange 1 is connected to the body platform 9, the inner side of the first flange 1 is fixedly connected to the upper flange of the inner beam 8 of the body, and the outer side of the first flange 1 is connected to the external electric winch connector 7. The inner side of the second flange 2 is fixedly connected to the lower flange of the inner beam 8 of the machine body, and the outer side of the second flange 2 is connected to the external electric winch connector 7. The inner side of the first web plate 3 is fixedly connected to the web plate of the inner beam 8 of the machine body, the upper part of the first web plate 3 is connected to the first flange 1, the lower part of the first web plate 3 is connected to the second flange 2, and the outer side of the first web plate 3 is connected to the external electric winch connector 7. The third flange 4 is fixedly connected to the upper flange of the outer beam 10 of the machine body; The fourth flange 5 is fixedly connected to the lower flange of the outer beam 10 of the machine body; The second web plate 6 is fixedly connected to the web plate of the outer beam 10 of the machine body. The external electric winch connector 7 is located on the center line of the entire joint structure and is in the form of a pin cylinder.

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