Tension-shear separation design method for uniaxial load bearing connector and load connector

Abstract

The invention belongs to the technical field of aircraft body strength design, and particularly relates to a tension-shear separation design method for a uniaxial load bearing connector and the load connector. On the basis of a given uniaxial load and a fixed supporting surface of a machine body structure, a load transfer path for separately transferring a shear load and a tensile load is provided, and a boss / groove is arranged on a joint bottom plate to be precisely matched with the machine body structure and is used for transferring the load in a mounting plane; meanwhile, the bolt hole is expanded to prevent the hole wall from being in contact with the bolt, and the bolt only transmits the load perpendicular to the mounting plane. Therefore, a uniaxial load borne by the joint lug is decomposed into a shear load transferred by the boss / groove of the joint bottom plate and a tensile load borne by the bolt, load separation is realized, and the design of the joint and a machine body structure is optimized.

Description

Technical Field

[0001] This invention belongs to the field of aircraft airframe strength design technology, specifically relating to a tensile-shear separation design method for a joint bearing a single-axis load and a load joint. Background Technology

[0002] In helicopter design, joints are a typical and commonly used load-bearing structure, playing a crucial role in maintaining structural integrity. Especially for the connection and fixation of major equipment or components such as the engine, main gearbox, and horizontal stabilizer to the fuselage, a combined load-bearing structure of "joint + strut" is typically used. In this case, the strut is a two-force member, and the joint is subjected to a uniaxial load F from the strut. Generally, the joint bearing the uniaxial load uses a lug structure to connect to the strut, while the joint base plate is usually bolted to the fuselage. Figure 1 As shown.

[0003] This design results in a complex load on the connecting bolts between the joint and the body, meaning the bolts bear both tensile load Ft and shear load Fs, such as... Figure 2 As shown. When this configuration is applied to critical connection parts, all bolt holes are required to be precision-machined holes, which greatly increases the difficulty of reaming and results in a high scrap rate; for the structure, it requires greater size and weight to meet the load-bearing requirements. Summary of the Invention

[0004] Objective: To provide a shear-load separation design method and load joint for bearing uniaxial loads, addressing the shortcomings of conventional joint configurations in terms of process and structural load transfer. Based on a given uniaxial load and a fixed support surface of the machine body structure, a load transfer path is proposed that separates shear and tensile loads. This is achieved by setting a boss / groove on the joint base plate for precise fit with the machine body structure to transfer loads within the mounting plane; simultaneously, the bolt holes are enlarged to avoid contact between the hole walls and the bolts, allowing the bolts to transfer loads perpendicular to the mounting plane. This decomposes the uniaxial load borne by the joint lugs into a shear load transferred by the boss / groove on the joint base plate and a tensile load borne by the bolts, achieving load separation. Figure 3 As shown, this leads to the optimization of the design of the connector and body structure.

[0005] To address the aforementioned technical issues, according to a first aspect of the present invention, a tensile-shear separation design method for a joint subjected to uniaxial loads is proposed, specifically comprising the following steps: Step 1: Based on the uniaxial load on the joint, set the load application point as point A, and determine the load direction vector. ; Step 2: Take point A as the center of the ear piece, and the direction of the ear piece is along the load direction vector. set up; Step 3: Determine the joint base plate arrangement surface that provides fixing function to the joint base plate, denoted as Surf-A; Step 4: Taking the load application point A as the endpoint, along the load direction vector... Extend the line in the opposite direction, and denote the intersection of the extension line and Surf-A as point O. Determine the vector passing through point O and perpendicular to Surf-A. ; Step 5: Convert the vector Projecting onto Surf-A, we obtain vectors in the Surf-A plane. ; Step Six: Based on the vector , The spatial geometric calculation relationship is used to determine the angle α between the load direction and the joint base plate arrangement surface; Step 7: With the perpendicular line perpendicular to Surf-A as the axis and the intersection point as point C, make a cylindrical groove on the side of the joint base plate that contacts the joint base plate arrangement surface, and make a cylindrical boss on the joint base plate arrangement surface that mates with the cylindrical groove. Step 8: Determine the magnitude of the shear load transmitted by the boss / groove based on the included angle α in Step 6, and then determine the dimensions of the cylindrical groove and cylindrical boss based on the load magnitude. The dimensions include the diameter and contact height. Step 9: Centered on point C, make multiple bolt through holes evenly spaced around the joint base plate and the surface of the joint base plate for installing fixing bolts.

[0006] In one possible embodiment, in step six, the included angle α is specifically calculated according to the following formula: With point O as the origin, and vector The Z-axis direction is represented by a vector. Establish a Cartesian coordinate system OXYZ along the X-axis, denoted as coordinate system 1; the coordinates of the following points are: Point O: Point A: ;

[0007] The included angle α serves as the basis for analyzing the rotational and overturning motions of the joint.

[0008] In one possible embodiment, step eight, determining the coordinates of point C, specifically includes the following steps: The center of the boss / groove on the Surf-A surface is set to point C, and its coordinates are... ; Point C lies on the Surf-A plane (i.e., the XOY plane), and can be determined. ; The rotational motion of the joint is analyzed to determine the coordinates Yc of point C. The process is as follows: Determine the component Fs of the load F in the Surf-A plane.

[0009] Determine the torque Mt that causes the joint to rotate around the axis of the boss.

[0010] in,

[0011] As a fixed load-transmitting structure, the joint must be designed to prevent rotation around the boss, thus requiring zero torque, i.e., Mt=0.

[0012] Determine the coordinates of point C

[0013] The overturning motion of the joint is analyzed to determine the coordinates Xc of point C. The process is as follows: Determine the component Fs of the load F in the Surf-A plane (i.e., the XOY plane).

[0014] Draw a perpendicular line from point C to Surf-A, intersecting line segment OA at point D.

[0015] Determine the moment Mp that causes the joint to overturn.

[0016] in,

[0017]

[0018] We can obtain,

[0019] The joint is bolted to a fixed support surface. Although the bolt load can balance the overturning moment of the joint, to avoid the overturning moment having a significant impact on the bolt load, the overturning moment value needs to be reduced in the joint design, i.e., it is required that... To determine the coordinates of point C using a smaller value, follow these recommendations: ; or

[0020] At this point, the coordinates of the center point C of the groove / boob are determined to be [Xo±10mm,Yo,Zo].

[0021] In one possible embodiment, in step eight, determining the dimensions of the cylindrical groove and the cylindrical boss based on the load size, including the diameter and contact height, specifically includes the following steps: The shear load transmitted at the boss / groove contact surface is Fs.

[0022] Let the diameter of the boss / groove be D and the contact height be H. Shear stress at the root of the boss

[0023] The shear strength limit of the material is And consider retaining a safety margin of ms. Diameter of the boss / groove:

[0024] Compressive stress at the contact surface

[0025] The tensile strength limit of the material is And consider retaining a safety margin of ms. The height of the boss / groove contact surface:

[0026] At this point, the dimensions of the groove / boss have been determined.

[0027] In one possible embodiment, in step nine, the magnitude of the tensile load transmitted at the bolted connection location is determined, and the bolt specification is determined; First, determine the load Ft that is perpendicular to the Surf-A plane and transmitted through the joint.

[0028] Ft is evenly distributed among the four bolts. The tensile load on each bolt due to Ft is:

[0029] In addition, the bolt load caused by the overturning moment on the joint:

[0030] From this, the tensile load of a single bolt can be obtained.

[0031] Set the bolt strength limit as Retain a safety factor of ms, and the bolt diameter d. To ensure structural integrity, the following must be satisfied:

[0032] Determine the bolt diameter as .

[0033] In one possible embodiment, in step five, the cylindrical groove and the cylindrical boss are in a precision fit; in step twelfth, the fixing bolt and the bolt through hole are in a clearance fit, and the diameter of the bolt through hole is enlarged until contact between the bolt shank and the bolt hole wall is avoided. A load Fs parallel to Surf-A is transmitted through cylindrical surface contact, and a load Ft perpendicular to Surf-A is transmitted through bolt connection.

[0034] According to a second aspect of the present invention, a load-bearing joint is provided, which is obtained by the above-described tensile-shear separation design method for a joint bearing a uniaxial load, comprising lugs, a joint base plate, a joint base plate arrangement surface, and fixing bolts; the lugs are disposed on the joint base plate along the load-bearing direction, a cylindrical groove is formed on the side of the joint base plate that contacts the joint base plate arrangement surface, and a corresponding cylindrical boss is provided on the joint base plate arrangement surface, the cylindrical boss and the cylindrical groove being precisely fitted; a plurality of bolt through holes are uniformly formed circumferentially around the center of the cylindrical boss on the joint base plate and the joint base plate arrangement surface, and the fixing bolts are installed in the bolt through holes and are clearance-fitted with the bolt through holes.

[0035] In summary, the beneficial effects of the present invention are as follows: For joints subjected to uniaxial loads, the above-mentioned tension-shear separation design method can bring the following benefits: (1) Compared to traditional joint configurations, this design method optimizes the load transmission path of joints bearing uniaxial loads. By separating the load at the joint fixing point through tension and shear, the load transmission at the connection point becomes more singular and clear. The groove / boob fit only bears the load within the plane of the joint base plate, and the bolt only bears the load perpendicular to the plane of the joint base plate. This is beneficial for the design of the fixing structure. For the groove / boob bearing structure, it can be designed as a long strip plate structure; while for the bolt support structure, it can be designed as a tension angle box structure. This makes the load transmission of the structure more direct, thereby achieving higher load-bearing efficiency and reducing the structural size and weight costs.

[0036] (2) This design method can be applied to the connection design of critical parts, separating the load transmission of the joint from tension and shear, which can reduce the number of precision holes. Since the bolt connection no longer bears shear load, the requirements for bolt hole diameter are greatly reduced, and there is no need to make a lot of reaming holes as with conventional joint configurations. This greatly reduces the difficulty of the process and also reduces the scrap rate of the product.

[0037] (3) The tensile-shear separation design method can optimize the fatigue design characteristics of the critical connection area between the joint and the fixed structure, and improve the fatigue characteristics of the structure. For bolted connections, the design of a large clearance fit avoids the scuffing damage to the bolt and the inner wall of the bolt hole; while for the precision fit between the groove / boob, the fatigue performance of the contact surface can be improved, thereby improving the fatigue life of the structure to a certain extent. Attached Figure Description

[0038] Figure 1 It is a common joint structure in existing technology; Among them, (1) the joint lugs of the prior art in general configuration and (2) the joint base plate of the prior art in general configuration. (3) Bolts of general configuration in the prior art.

[0039] Figure 2 This is a load analysis of conventional joint configurations in existing technologies; Figure 3 This is a schematic diagram of the load after the tensile and shear loads of the joint are separated according to a preferred embodiment of the present invention; Among them, (4) the new configuration of the connector lug of the present invention, (5) the new configuration of the connector base plate of the present invention, (6) the new configuration of the fixing structure of the present invention, (7) the new configuration of the bolt of the present invention, and (8) the new configuration of the groove / boss fit of the present invention; Figure 4 This is a schematic diagram of the load direction vector and lug arrangement of a preferred embodiment of the present invention; Figure 5 This is a schematic diagram of the joint base plate arrangement surface Surf-A of a preferred embodiment of the present invention; Figure 6 The preferred embodiment of the present invention is the joint base plate arrangement surface O and vector. A schematic diagram for determining the location; Among them, (8) the new configuration of the connector lug of the present invention, (9) the new configuration of the connector base plate of the present invention, (10) the new configuration of the fixing structure of the present invention, and (11) the new configuration of the present invention, Surf-A; Figure 7 This is a schematic diagram illustrating the determination of the reference coordinate system OXYZ and the included angle α in a preferred embodiment of the present invention; Among them, (12) the new configuration connector lug of the present invention, (13) the new configuration connector base plate of the present invention, and (14) the new configuration fixing structure of the present invention; Figure 8 This is a schematic diagram illustrating the arrangement of the boss / groove according to a preferred embodiment of the present invention; Among them, (16) the new configuration of the present invention, boss / groove mating Figure 9 This is a schematic diagram of the joint rotation torque analysis of a preferred embodiment of the present invention; Among them, (18) the groove of the new configuration of the present invention and (19) the boss of the new configuration of the present invention; Figure 10 This is a schematic diagram of the joint overturning moment analysis of a preferred embodiment of the present invention; Among them, (21) the groove of the new configuration of the present invention and (22) the boss of the new configuration of the present invention; Figure 11 This is a top view of the joint installation and a schematic diagram of the bolt hole arrangement of a preferred embodiment of the present invention. Among them, (24) the new configuration of the connector ear piece of the present invention, (25) the new configuration of the connector base plate of the present invention, (26) the new configuration of the fixing structure of the present invention, (27) the new configuration of the groove / boss of the present invention, and (28) the new configuration of the bolt hole of the present invention. Detailed Implementation

[0040] 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.

[0041] 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.

[0042] 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.

[0043] Example 1 A method for designing a tension-shear separation joint to withstand uniaxial loads, specifically including the following steps: Step 1: Based on the uniaxial load on the joint, set the load application point as point A, and determine the load direction vector. ,like Figure 4 As shown; Step 2: Based on the load direction vector Determine the placement of the connector lugs, taking point A as the lug center, with the lug direction along the load direction vector. ,like Figure 4 As shown; Step 3: Define the joint base plate arrangement surface that provides fixing function to the joint base plate, denoted as Surf-A, such as... Figure 5 As shown; Step 4: Taking the load application point A as the endpoint, along the load direction vector... Extend the line in the opposite direction, and denote the intersection of the extension line and Surf-A as point O. Determine the vector passing through point O and perpendicular to Surf-A. ,like Figure 6 As shown; Step 5: Convert the vector Projecting onto Surf-A, we obtain vectors in the Surf-A plane. ; Step Six: Taking point O as the origin, and using vector... The Z-axis direction is represented by a vector. Establish a Cartesian coordinate system OXYZ along the X-axis, denoted as coordinate system 1; for example... Figure 7 As shown.

[0044] Reference coordinate system 1, the coordinates of the following points are: Point O:

[0045] Point A:

[0046] Step 7: Determine the angle α between the load direction and the joint base plate layout surface, such as... Figure 7 As shown:

[0047] The included angle α serves as the basis for analyzing the rotational and overturning motions of the joint.

[0048] Step 8: Using the vertical line of Surf-A as the axis, create a cylindrical groove on the side of the joint base plate that contacts the joint base plate arrangement surface. Then, create a cylindrical boss on the joint base plate arrangement surface that mates with the cylindrical groove, such as... Figure 8 As shown.

[0049] The center of the aforementioned boss / groove on the Surf-A surface is set at point C, and its coordinates are... .

[0050] Point C lies on the Surf-A plane (i.e., the XOY plane), and can be determined.

[0051] Step Nine: Perform rotational motion analysis on the joint to determine the coordinates Yc of point C. The process is as follows. Figure 9 As shown.

[0052] Determine the component Fs of the load F in the Surf-A plane.

[0053] Determine the torque Mt that causes the joint to rotate around the axis of the boss.

[0054] in,

[0055] As a fixed load-transmitting structure, the joint must be designed to prevent rotation around the boss, thus requiring zero torque, i.e., Mt=0.

[0056] The coordinates of point C can be determined.

[0057] Step 10: Perform overturning motion analysis on the joint to determine the coordinates Xc of point C. The process is as follows. Figure 10 As shown.

[0058] Determine the component Fs of the load F in the Surf-A plane (i.e., the XOY plane).

[0059] Draw a perpendicular line from point C to Surf-A, intersecting line segment OA at point D.

[0060] Determine the moment Mp that causes the joint to overturn.

[0061] in,

[0062]

[0063] We can obtain,

[0064] The joint is bolted to a fixed support surface. Although the bolt load can balance the overturning moment of the joint, to avoid the overturning moment having a significant impact on the bolt load, the overturning moment value needs to be reduced in the joint design, i.e., it is required that... To determine the coordinates of point C using a smaller value, follow these recommendations: ; or

[0065] At this point, the coordinates of the center point C of the groove / bore are determined to be [Xo±10mm,Yo,Zo]. Step Eleven: Determine the magnitude of the shear load transmitted by the boss / groove, and determine the dimensions of the cylindrical groove and cylindrical boss, including diameter and contact height; The shear load transmitted at the boss / groove contact surface is Fs.

[0066] Let the diameter of the boss / groove be D and the contact height be H. Shear stress at the root of the boss

[0067] The shear strength limit of the material is And consider retaining a safety margin of ms. Diameter of the boss / groove:

[0068] Compressive stress at the contact surface

[0069] The tensile strength limit of the material is And consider retaining a safety margin of ms. The height of the boss / groove contact surface:

[0070] At this point, the dimensions of the groove / boss have been determined.

[0071] Step Twelve: Centered on point C, four bolt through holes are evenly opened on the joint base plate and the joint base plate layout surface for installing fixing bolts.

[0072] The spacing between bolt holes in the X direction is Lx, and the spacing between bolt holes in the Y direction is Ly. For example... Figure 11 As shown.

[0073] Step Thirteen: Determine the magnitude of the tensile load transmitted at the bolted connection location and determine the bolt specifications.

[0074] First, determine the load Ft that is perpendicular to the Surf-A plane and transmitted through the joint.

[0075] Ft is evenly distributed among the four bolts. The tensile load on each bolt due to Ft is:

[0076] In addition, the bolt load caused by the overturning moment on the joint:

[0077] From this, the tensile load of a single bolt can be obtained.

[0078] Set the bolt strength limit as Retain a safety factor of ms, and the bolt diameter d. To ensure structural integrity, the following must be satisfied:

[0079] The bolt diameter can be determined as follows:

[0080] In step five, the cylindrical groove and the cylindrical boss are precisely fitted; in step twelve, the fixing bolt and the bolt through hole are clearance fitted, and the diameter of the bolt through hole is enlarged until contact between the bolt shank and the bolt hole wall is avoided. A load Fs parallel to Surf-A is transmitted through cylindrical surface contact, and a load Ft perpendicular to Surf-A is transmitted through bolt connection.

[0081] Example 2 like Figure 10 As shown, a load-bearing joint, obtained using the above-mentioned tensile-shear separation design method for a joint bearing uniaxial loads, includes lugs, a joint base plate, a joint base plate arrangement surface, and fixing bolts. The lugs are disposed on the joint base plate along the load-bearing direction. A cylindrical groove is formed on the side of the joint base plate that contacts the joint base plate arrangement surface. A corresponding cylindrical boss is provided on the joint base plate arrangement surface, and the cylindrical boss and the cylindrical groove are precisely fitted together. Multiple bolt through holes are uniformly formed circumferentially around the center of the cylindrical boss on the joint base plate and the joint base plate arrangement surface. The fixing bolts are installed in the bolt through holes and are connected with the bolt through holes with a clearance fit.

Claims

1. A method of designing a pull-off joint for a single-axial load joint, characterized by, Specifically comprising the following steps: step one: according to the uniaxial load suffered by the joint, the load action point is set as point A, and the load direction vector is determined ; step two: taking point A as the ear piece center, the ear piece direction is set along the load direction vector ; step three: the joint bottom plate arrangement surface for providing fixing action to the joint bottom plate is determined, denoted as Surf-A; step four: an extension line is made along the reverse direction of the load direction vector with the load action point A as the end point, and the intersection point of the extension line and Surf-A is denoted as point O, and a vector passing through point O and perpendicular to Surf-A is determined; step five: the vector is projected to Surf-A, and a vector in the Surf-A plane is obtained; step six: according to the spatial geometric calculation relationship of the vectors , , the included angle α between the load direction and the joint bottom plate arrangement surface is determined; step seven: taking the perpendicular line perpendicular to Surf-A as the axis and the intersection point as point C, a cylindrical groove is set on the side of the joint bottom plate in contact with the joint bottom plate arrangement surface, and a cylindrical boss matched with the cylindrical groove is set on the joint bottom plate arrangement surface; step eight: according to the included angle α in the step six, the size of the shear load transmitted by the boss / groove is determined, and then according to the load size, the size of the cylindrical groove and the cylindrical boss, including the diameter and the contact height, is determined; step nine: taking point C as the center, a plurality of bolt through holes are uniformly set on the joint bottom plate and the joint bottom plate arrangement surface in the circumferential direction, which are used for installing fixing bolts.

2. The method of claim 1, wherein, In the step six, the included angle a is calculated according to the following formula: A Cartesian coordinate system OXYZ is established with O point as the origin, vector as the Z-axis direction, and vector as the X-axis direction, denoted as coordinate system 1; the coordinates of the following points are denoted as: O point: , A point: ; 。 3. The method of claim 1, wherein, In the step eight, the coordinates of the point C are determined, which specifically includes the following steps: The center of the boss / groove on the Surf-A surface is set as point C, and its coordinates are ; C point is located on Surf-A plane (i.e. XOY plane), which can determine ; The rotational motion analysis of the joint is performed to determine the coordinate Yc of the point C, and the process is as follows: The component Fs of the load F on the Surf-A plane is determined, The torque Mt that makes the joint rotate around the boss axis is determined, wherein The joint is a fixed transmission structure, and the rotation of the joint around the boss is avoided, so the torque should be zero, that is, Mt=0, Determining the coordinate amount of c-point The overturning motion analysis of the joint is performed to determine the coordinate Xc of the point C, and the process is as follows: The component Fs of the load F on the Surf-A plane (i.e. the XOY plane) is determined, A vertical line of Surf-A is drawn through the point C, and the line segment OA intersects the point D. The moment Mp that makes the joint overturn is determined, wherein, It can be obtained that The joint is bolted to the fixed support surface, although the bolt load can balance the overturning moment of the joint, in order to avoid the overturning moment from having a large impact on the bolt load, the value of the overturning moment needs to be reduced in the joint design, that is, the overturning moment needs to be reduced A small amount, for the coordinates of point C, is determined according to the following formula: ； Or At this point, the coordinates of the center point C of the groove / boss are determined as [Xo±10mm, Yo, Zo].

4. The method of claim 3, wherein, In the step eight, the size of the cylindrical groove and the cylindrical boss is determined according to the load size, and the size includes the diameter and the contact height, which specifically includes the following steps: The shear load transmitted by the contact surface of the boss / groove is Fs, The diameter of the boss / groove is set as D, and the contact height is set as H, Shear stress at root of boss The shear strength limit of the material is and considering a safety factor of retention ms, Then the diameter of the boss / groove is: Contact surface extrusion stress The tensile strength limit of the material is and considering a safety factor of reservation ms, Then the contact surface height of the boss / groove is: At this point, the size of the groove / boss is determined.

5. The method of claim 1, wherein, In the step nine, the size of the tensile load transmitted by the bolt connection position is determined, and the bolt specification is determined; Firstly, the load Ft perpendicular to the Surf-A plane is determined, Ft is evenly divided by the four bolts, and the tensile load of a single bolt caused by Ft is: In addition, the bolt load caused by the overturning moment of the joint is: From which the tensile load of a single bolt can be obtained Setting the bolt strength limit to , a safety factor ms, the bolt diameter d Then, in order to ensure the structural integrity, it is necessary to meet The bolt diameter is determined as 。 6. The method of designing a pull-off separation of a single-axial load joint according to claim 1, wherein, The cylindrical groove and the cylindrical boss are in precise fit; the fixed bolt and the bolt through hole are in clearance fit, and the diameter of the bolt through hole is expanded until contact between the bolt rod and the bolt hole wall is avoided.

7. A load link characterized by, A tensile-shear separation design method of a joint bearing uniaxial load is obtained by using any one of the design methods of claims 1-6, comprising an ear, a joint bottom plate, a joint bottom plate arrangement surface, a fixed bolt; the ear is arranged on the joint bottom plate in the direction of bearing load, the joint bottom plate is provided with a cylindrical groove on the side in contact with the joint bottom plate arrangement surface, the joint bottom plate arrangement surface is provided with a corresponding cylindrical boss, and the cylindrical boss and the cylindrical groove are in precise fit; the joint bottom plate and the joint bottom plate arrangement surface are uniformly provided with a plurality of bolt through holes around the center of the cylindrical boss, and the fixed bolt is installed in the bolt through hole and connected in clearance fit with the bolt through hole.

8. A helicopter characterized by A load joint comprising the joint of claim 7.

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