Assembling composite square tube connecting device and assembling method

Abstract

The invention discloses an assembled composite square tube connecting device and an assembling method, and belongs to the technical field of composite material connection. According to the assembled composite square tube connecting device, an outer hoop tube and a core tube are arranged outside and inside the end of a square tube in a sleeving mode correspondingly; the core pipe and the square pipe are fixedly connected through the connecting layer, then the outer hoop pipe and the end, extending out of the square pipe, of the core pipe are combined in the mode of extruding the outer hoop pipe, a metal combination face is formed, and finally the ends, away from the square pipe, of the outer hoop pipe and the core pipe are sleeved with the spliced pipe. The square tube, the core tube, the outer hoop tube and the splicing tube are spliced into a whole by adopting a splicing pin through a first connecting pin hole formed in the splicing tube, a second connecting pin hole formed in the outer hoop tube and a third connecting pin hole formed in the core tube, so that the synergistic force transmission effect is achieved when the outer hoop tube, the core tube and the square tube serve as a connecting assembly; the problem that connection strength is greatly reduced due to the fact that connection of the composite material square tubes only depends on a force transmission way of a single connecting piece and the composite material square tubes at present is solved.

Description

Technical Field

[0001] This invention relates to a composite square tube connection device and assembly method, belonging to the field of composite material connection technology. Background Technology

[0002] In high-end equipment sectors such as transportation, energy and power, aerospace, and marine engineering, prefabricated structures place stringent technical requirements on the reliability and ease of manufacturing of component connections. High-performance fiber-reinforced composite materials, due to their lightweight, high specific strength, and high specific modulus, have become the preferred material for load-bearing structures and components with complex geometries. Among these, composite square tubes, with their superior performance and ease of molding, are the preferred component for prefabricated structures. Therefore, constructing efficient, reliable, and easily assembled connection nodes between composite square tubes and between composite square tubes and metal components is crucial to ensuring the overall structural performance.

[0003] Currently, the main connection methods for composite square tubes include bolt connections and adhesive connections. However, both have certain limitations, particularly the low utilization rate of composite materials, the single force transmission path, low connection strength, and the inability to quickly assemble and disassemble. Furthermore, the composite square tube and metal connectors cannot cooperate in force transmission, making it difficult to meet the design requirements of high-load-bearing composite connection structures and rapid assembly structures. In addition, there is significant stress concentration at the corners of the square tube cross-section. The composite material itself is anisotropic and has low local compressive and shear strength. When the corner structure design of the composite square tube is unreasonable when connecting it to the external metal parts, it is easy to cause serious local damage to the corners of the composite square tube, significantly reducing the connection strength and reliability. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composite square tube connection device and assembly method that can realize the coordinated force transmission between each connector and the tube itself at the tube connection, thus solving the problem that the current connection of composite square tubes relies on only a single connector and the composite square tube for force transmission, and the resulting significant reduction in connection strength.

[0005] To solve the above-mentioned technical problems, the present invention is implemented using the following technical solution: The present invention provides a composite square tube connection device, including a connection part for connecting different square tubes, wherein the connection part includes an assembly tube at least at two ends, an outer clamp tube and a core tube disposed at the ends of the assembly tube; The end of the core tube away from the assembly tube is fitted inside the square tube, and the contact surface between the core tube and the square tube is provided with a connecting layer. The core tube and the square tube are fixedly connected through the connecting layer, and the other end of the core tube is fitted inside the outer hoop tube. The outer hoop tube is sleeved on the outside of the square tube at one end away from the assembly tube, and the other end of the outer hoop tube is sleeved in the assembly tube and contacts the core tube to form a metal bonding surface; The assembly tube is also provided with a first connecting pin hole, the other end of the outer clamp tube is provided with a second connecting pin hole corresponding to the first connecting pin hole, and the other end of the core tube is provided with a third connecting pin hole corresponding to the first connecting pin hole. The first connecting pin hole, the second connecting pin hole, and the third connecting pin hole are connected by an assembly pin.

[0006] Optionally, the outer surface of the outer hoop tube is provided with a transition arc, and the inner wall surface is provided with a transition fillet; the inner wall surface of the assembled tube is provided with a connecting fillet that matches the transition arc.

[0007] Optionally, the ends of the assembled tubes are provided with an included angle, the included angle ranging from 30° to 180°.

[0008] Optionally, the contact surface between the outer hoop and the square tube is also provided with a connecting layer, and the outer hoop and the square tube are fixedly connected through the connecting layer.

[0009] Optionally, the connecting layer includes a shear interlock interface or an adhesive layer.

[0010] Optionally, a group of metal shear bonds is provided on the outer surface of the end of the core tube away from the assembly tube, and a group of composite material shear bonds corresponding to the group of metal shear bonds is provided on the contact surface between the inner wall of the square tube and the core tube, and the group of metal shear bonds and the group of composite material shear bonds form a shear interlock interface.

[0011] Optionally, the metal shear bond group consists of multiple rows of diagonally parallel or laterally parallel triangular fine-tooth threads with a height of less than 1.8 mm, and the spacing between each row of the triangular fine-tooth threads is less than 2.0 mm.

[0012] Optionally, the lateral width of the metal shear bond group is smaller than the outer wall width of the core tube.

[0013] Optionally, the outer surface of the end of the outer clamp tube away from the assembled tube is on the same plane as the outer surface of the assembled tube.

[0014] In another aspect, the present invention provides an assembly method for the composite square tube connecting device as described above, comprising: According to the design drawings and size requirements, the square tube is cut to the preset size, and metal shear keys are machined on the outer surface of the core tube; The core tube, outer hoop tube, and square tube are connected together. The contact section between the outer hoop tube and the square tube is extruded using an extrusion die, so that the metal shear bond group on the outer surface of the core tube fits with the inner wall of the square tube. The metal shear bond group is forced to be extruded into the composite shear bond group on the inner wall of the square tube, forming a shear interlocking interface. Then, the other end of the outer clamp tube is extruded using an extrusion die, so that the outer clamp tube and the other end of the core tube come into contact with each other and radial pressure is applied, so that the outer clamp tube and the core tube are tightly joined together to form a metal bonding surface. The first connecting pin hole, the second connecting pin hole, and the third connecting pin hole are connected by assembly pins to complete the assembly.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: 1. This invention involves fitting an outer hoop tube and a core tube onto the outside and inside of the square tube end, respectively. The core tube is fixed to the square tube through a connecting layer, and then the outer hoop tube is pressed to connect the end of the core tube extending out of the square tube, forming a metal bonding surface. Finally, the ends of the outer hoop tube and the core tube away from the square tube are fitted into the assembled tube. An assembly pin is used to assemble the square tube, core tube, outer hoop tube, and assembled tube into a whole through a first connecting pin hole on the assembled tube, a second connecting pin hole on the outer hoop tube, and a third connecting pin hole on the core tube. This achieves a synergistic force transmission effect when the outer hoop tube, core tube, and square tube act as connecting components, solving the problem that current methods of connecting composite square tubes rely solely on a single connecting component for force transmission, resulting in a significant reduction in connection strength.

[0016] 2. This invention creates a group of metal shear keys on the outer surface of the core tube, the latter having a lateral width smaller than the outer wall width of the former. A corresponding composite shear key group is then created on the inner wall of the square tube using a press-fit method. Simultaneously, the core tube is also part of the connecting assembly. The metal shear key group and the composite shear key group form a shear interlocking interface. This achieves the synergistic force transmission effect of the connecting assembly while avoiding the high difficulty, high cost, and initial defects and assembly gaps associated with the secondary processing of directly opening teeth on the composite square tube. Furthermore, it solves the problem of stress concentration at the corners of the composite square tube and the resulting localized material damage.

[0017] 3. This invention uses an extruded outer hoop tube to connect the outer hoop tube to one end of the core tube extending out of the square tube. This end is then fitted into the assembly tube, forming an assembly connection structure with the same cross-section between the outer hoop tube and the assembly tube. By using the assembly pin and the connecting pin hole to cooperate, a rapid assembly effect between multiple composite material square tubes is achieved. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of an assembly composite square tube connection device provided in an embodiment of the present invention; Figure 2 This is an exploded structural diagram of an assembly composite square tube connection device provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the connection structure provided in an embodiment of the present invention; Figure 4This is a schematic diagram of the core tube structure provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the shear interlock interface provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the outer hoop tube structure provided in an embodiment of the present invention; Figure 7 This is a schematic diagram of the assembled pipe structure provided in an embodiment of the present invention (showing a linear structure); Figure 8 This is a cross-sectional structural schematic diagram of an assembly composite square tube connection device provided in an embodiment of the present invention; Figure 9 This is a schematic diagram of the assembled pipe structure provided in an embodiment of the present invention (showing an L-shaped structure); Figure 10 This is a schematic diagram of the assembled pipe structure provided in an embodiment of the present invention (showing a T-shaped structure); Figure 11 This is a schematic diagram of the assembled pipe structure provided in an embodiment of the present invention (showing a cross-shaped structure). Figure 12 This is a schematic diagram of shear interlock interface forming provided in an embodiment of the present invention (in the figure, F represents pressure and the arrow indicates the direction of force application). Figure 13 This is a schematic diagram of metal bonding surface forming provided in an embodiment of the present invention (in the figure, F represents pressure and the arrow indicates the direction of force application).

[0019] In the diagram: 1. Assembled tube; 101. Connecting rounded corner; 102. First connecting pin hole; 2. Outer clamp tube; 201. Transition arc; 202. Transition rounded corner; 203. Second connecting pin hole; 3. Core tube; 301. Third connecting pin hole; 401. First square tube; 402. Second square tube; 403. Third square tube; 404. Fourth square tube; 5. Connecting layer; 501. Shear interlock interface; 5011. Metal shear key group; 5012. Composite material shear key group; 6. Assembled pin; 7. Extrusion die; 8. Metal mating surface. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention. Example 1

[0021] like Figure 1As shown, a composite square tube connecting device includes a connecting part for connecting different square tubes. The connecting part includes an assembly tube 1 with at least two ends, an outer clamp tube 2 and a core tube 3 disposed at the ends of the assembly tube 1. The assembly tube 1 has at least two ends with an included angle between the ends, the included angle ranging from 30° to 180°. Specifically, in this embodiment, the assembly tube 1 has two straight ends for connecting two composite square tubes. For ease of description, the two composite square tubes are a first square tube 401 and a second square tube 402. The two composite square tubes are symmetrically disposed at the left and right ends of the assembly tube 1. Taking one side of the first square tube 401 as an example: like Figure 2 and Figure 3 As shown, in order to reduce weight while maintaining the structural strength of the core tube 3, a hole is drilled in the middle of the core tube 3, and the left end of the core tube 3 is fitted inside the first square tube 401. A connecting layer 5 is provided on the contact surface between the outer surface of the core tube 3 and the inner surface of the first square tube 401. The core tube 3 and the first square tube 401 are fixedly connected through the connecting layer 5. like Figure 4 and Figure 5 As shown, the connecting layer 5 is a shear interlock interface 501 or an adhesive layer. A metal shear bond group 5011 is formed on the outer surface of the core tube 3. By applying extrusion pressure to the first square tube 401, a composite material shear bond group 5012 is formed at the corresponding position on the inner wall of the first square tube 401. The metal shear bond group 5011 and the composite material shear bond group 5012 form a shear interlock interface 501. At the same time, the core tube 3 is also part of the force transmission of the connecting component. While achieving the coordinated force transmission effect of the connecting component, it avoids the high difficulty and cost of secondary processing of directly opening teeth on the composite material square tube. The metal shear key group 5011 consists of multiple rows of diagonally parallel or laterally parallel triangular fine-tooth threads with a height h less than 1.8 mm, and the spacing between each row of triangular fine-tooth threads is less than 2.0 mm. To avoid stress concentration and local damage at the corners of the inner wall of the first square tube 401 during the fabrication of the composite shear key group 5012 by pressing the metal shear key group 5011, the lateral width of the metal shear key group 5011 is less than the lateral width of the outer wall of the core tube 3. In this embodiment, the lateral width of the metal shear key group 5011 is three-quarters or four-fifths of the lateral width of the outer wall of the core tube 3. When the requirement for connection force transmission is small, the shear interlock interface 501 can also be replaced with an adhesive layer.

[0022] like Figure 2 and Figure 3 As shown, the right end of the core tube 3 is inserted into the left end of the outer hoop tube 2 and extends into the outer hoop tube 2. The left end of the outer hoop tube 2 is fitted outside the first square tube 401. If the connection force transmission requirement is large, the contact surface between the left end of the outer hoop tube 2 and the first square tube 401 is also provided with a connecting layer 5. The outer hoop tube 2 and the first square tube 401 are fixedly connected through the connecting layer 5. The right end of the outer clamp tube 2 is fitted onto the right end of the assembled tube 1 and extends into the assembled tube 1. The part of the right end of the core tube 3 extending into the outer clamp tube 2 corresponds to the part of the right end of the outer clamp tube 2 extending into the assembled tube 1. A metal bonding surface 8 is formed by extrusion. The outer surface of the end of the outer clamp tube 2 located outside the assembled tube 1 is on the same plane as the outer surface of the assembled tube 1, forming an assembled connection structure with the same cross-section as the outer clamp tube 2 and the assembled tube 1. like Figure 3 , Figure 6 and Figure 7 As shown, the outer surface of the outer hoop tube 2 is provided with a transition arc 201, and the inner wall of the assembly tube 1 is provided with a connecting fillet 101 that matches the transition arc 201, so as to achieve quick alignment and assembly of different connecting components during assembly, while avoiding jamming caused by slight misalignment. In addition, such as Figure 3 and Figure 5 As shown, the contact surface between the inner wall of the outer hoop tube 2 and the first square tube 401 is also provided with a transition fillet 202 to avoid local damage to the surface fibers and cross-section of the first square tube 401 during the extrusion splicing process. like Figure 3 , Figure 6 , Figure 7 and Figure 8 As shown, the assembly tube 1 is also provided with a first connecting pin hole 102. At the right end of the outer clamp tube 2 and the right end of the core tube 3, corresponding to the position of the first connecting pin control hole, a second connecting pin hole 203 and a third connecting pin hole 301 are respectively provided. The first connecting pin hole 102 is connected to the second connecting pin hole 203 and the third connecting pin hole 301 through the assembly pin 6. The connection methods of each core tube 3, outer hoop tube 2, and assembly pin 6 to the assembly tube 1 on one side of the second square tube 402 are the same, with only the orientation being different, so they will not be described in detail; then the square tube, core tube 3, outer hoop tube 2 and assembly tube 1 are assembled into a connected whole, thereby realizing the synergistic force transmission effect when the outer hoop tube 2, core tube 3 and square tube are used as connecting components; like Figure 9 As shown, the assembly tube 1 in this embodiment can also be L-shaped, with the included angle between the two ends of the assembly tube 1 being 90°. Example 2

[0023] like Figure 10 As shown, this embodiment is based on the same inventive concept as Embodiment 1. The difference is that the assembly tube 1 has three ends, which are T-shaped, for assembling and connecting three composite square tubes. The three composite square tubes are the first square tube 401, the second square tube 402, and the third square tube 403. Example 3

[0024] like Figure 11As shown, this embodiment is based on the same inventive concept as Embodiment 1. The difference is that the assembly tube 1 has four ends in a cross shape for assembling and connecting four composite square tubes. The four composite square tubes are the first square tube 401, the second square tube 402, the third square tube 403, and the fourth square tube 404. Example 4

[0025] An assembly method for a composite square tube connecting device, used to assemble a composite square tube connecting device provided in Embodiment 1, includes: like Figure 3 As shown, according to the design drawings and size requirements, the square tube to be connected is cut to the preset size, and metal shear key group 5011 is processed on the outer surface of the core tube 3; Taking the first square tube 401 as an example, such as Figure 12 As shown, the core tube 3 and the outer hoop tube 2 are respectively sleeved with the first square tube 401. The contact section between the left end of the outer hoop tube 2 and the first square tube 401 is squeezed by the extrusion die 7, so that the metal shear bond group 5011 on the outer surface of the core tube 3 fits with the inner wall surface of the first square tube 401, and the metal shear bond group 5011 is forced to be extruded into the composite shear bond group 5012 on the inner wall surface of the square tube, forming a shear interlock interface 501. like Figure 13 As shown, the other end of the outer clamp tube 2 is then extruded using the extrusion die 7, so that the outer clamp tube 2 and the other end of the core tube 3 come into contact with each other and are subjected to radial pressure, so that the outer clamp tube 2 and the core tube 3 are tightly joined together to form a metal bonding surface 8. like Figure 2 , Figure 3 and Figure 8 As shown, the right end of the outer clamp tube 2 is inserted into the left end of the assembly tube 1, so that the second connecting pin hole 203 and the third connecting pin hole 301 coincide with the first connecting pin hole 102 on the assembly pin 6. Then, the assembly pin 6 is inserted into the assembly tube 1 through the first connecting pin hole 102. The assembly pin 6 enters the outer clamp tube 2 through the second connecting pin hole 203 and the core tube 3 through the third connecting pin hole 301. The assembly pin 6 then exits the core tube 3 through the third connecting pin hole 301 and the outer clamp tube 2 through the second connecting pin hole 203. Finally, the assembly pin 6 exits the assembly tube 1 through the first connecting pin hole 102, completing the assembly.

[0026] Working principle Before assembly, no pre-processing of any grooves or screw holes is required at the ends of the square tubes. Taking one side of the first square tube 401 as an example: During the assembly process, the first connecting pin hole 102, the second connecting pin hole 203, and the third connecting pin hole 301 are respectively opened at the aligned positions of the first square tube 401, the outer hoop tube 2, and the core tube 3. Subsequently, radial pressure is applied to the outer hoop tube 2 through the extrusion die 7, causing the outer hoop tube 2 to undergo radial plastic deformation. Its inner wall tightly adheres to the outer wall of the first square tube 401, while the metal shear key group 5011 on the core tube 3 adheres to the inner wall surface of the first square tube 401, forcing the metal shear key group 5011 to adhere to the inner wall surface of the first square tube 401. The shear key group 5011 is extruded into the composite shear key group 5012 on the inner wall of the square tube to form a shear interlock interface 501. Then, the other end of the outer hoop tube 2 is extruded by the extrusion die 7, so that the outer hoop tube 2 and the other end of the core tube 3 come into contact with each other and are subjected to radial pressure, so that the outer hoop tube 2 and the core tube 3 are tightly combined to form a metal bonding surface 8. Then, the assembly pin 6 is used to complete the overall assembly of the square tube, the core tube 3, the outer hoop tube 2 and the assembly tube 1 through the cooperation of the first connecting pin hole 102, the second connecting pin hole 203 and the third connecting pin hole 301, forming a multi-path and multi-mode load transfer path. When the connecting part is subjected to axial load, the external load is first transmitted to the assembly tube 1, and then transmitted to the end of the outer hoop tube 2 and the core tube 3 extending into the assembly tube 1 via the assembly pin 6. The force is transmitted through the friction of the metal bonding interface 8. Subsequently, the external load is transmitted to the contact section of the outer hoop tube 2, the metal inner core 3 and the square tube respectively. Then, the external load is transmitted to the end of the square tube respectively through the shear interlock interface 501 between the core tube 3 and the square tube and the friction of the contact surface between the outer hoop tube 2 and the square tube. Finally, the external load is transmitted to the connecting part at the other end through the square tube. In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "assembly," "assembly," "connection," "linking," and "fixed connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite square tube assembly connection device, characterized in that, It includes a connecting part for connecting different square tubes, the connecting part including an assembly tube (1) at least two ends, an outer clamp tube (2) provided at the end of the assembly tube (1) and a core tube (3); The end of the core tube (3) away from the assembly tube (1) is sleeved inside the end of the square tube, and the contact surface between the core tube (3) and the square tube is also provided with a connecting layer (5). The core tube (3) and the square tube are fixedly connected through the connecting layer (5), and the other end of the core tube (3) is sleeved in the outer hoop tube (2). The outer hoop tube (2) is sleeved on the outside of the square tube end at one end away from the assembly tube (1), and the other end of the outer hoop tube (2) is sleeved in the assembly tube (1) and contacts the core tube (3) to form a metal joint surface (8). The assembly tube (1) is also provided with a first connecting pin hole (102), the other end of the outer hoop tube (2) is provided with a second connecting pin hole (203) corresponding to the first connecting pin hole (102), and the other end of the core tube (3) is provided with a third connecting pin hole (301) corresponding to the first connecting pin hole (102). The first connecting pin hole (102), the second connecting pin hole (203), and the third connecting pin hole (301) are connected by an assembly pin (6).

2. The assembled composite square tube connecting device according to claim 1, characterized in that, The outer hoop tube (2) has a transition arc (201) on its outer surface and a transition fillet (202) on its inner wall; the inner wall of the assembled tube (1) has a connecting fillet (101) that matches the transition arc (201).

3. The assembled composite square tube connecting device according to claim 1, characterized in that, The ends of the assembled tube (1) are provided with an included angle, which ranges from 30° to 180°.

4. The assembly composite square tube connecting device according to claim 1, characterized in that, The contact surface between the outer hoop tube (2) and the square tube is also provided with a connecting layer (5), and the outer hoop tube (2) and the square tube are fixedly connected through the connecting layer (5).

5. The assembled composite square tube connecting device according to claim 1 or 4, characterized in that, The connecting layer (5) includes a shear interlock interface (501) or an adhesive layer.

6. The assembled composite square tube connecting device according to claim 5, characterized in that, The outer surface of the core tube (3) away from the assembly tube (1) is provided with a metal shear bond group (5011), and the inner wall of the square tube and the contact surface of the core tube (3) are provided with a composite material shear bond group (5012) corresponding to the metal shear bond group (5011). The metal shear bond group (5011) and the composite material shear bond group (5012) form a shear interlock interface (501).

7. The assembled composite square tube connecting device according to claim 6, characterized in that, The metal shear bond group (5011) consists of multiple rows of diagonally parallel or laterally parallel triangular fine-tooth threads with a height of less than 1.8 mm, and the spacing between each row of the triangular fine-tooth threads is less than 2.0 mm.

8. The assembly composite square tube connecting device according to claim 6, characterized in that, The transverse width of the metal shear bond group (5011) is smaller than the outer wall width of the core tube (3).

9. The assembly composite square tube connecting device according to claim 1, characterized in that, The outer surface of the outer hoop tube (2) at the end away from the assembly tube (1) is on the same plane as the outer surface of the assembly tube (1).

10. An assembly method for a composite square tube connecting device as described in any one of claims 1 to 9, characterized in that, include: According to the design drawings and size requirements, the square tube is cut to the preset size, and metal shear keys (5011) are processed on the outer surface of the core tube (3). The core tube (3), outer hoop tube (2) are connected to the square tube. The contact section between the outer hoop tube (2) and the square tube is squeezed by the extrusion die, so that the metal shear bond group (5011) on the outer surface of the core tube (3) fits with the inner wall of the square tube, and the metal shear bond group (5011) is forced to be squeezed into the composite shear bond group (5012) on the inner wall of the square tube, forming a shear interlock interface (501). Then, the other end of the outer clamp tube (2) is squeezed by the extrusion mold, so that the other end of the outer clamp tube (2) and the core tube (3) come into contact with each other and are subjected to radial pressure, so that the outer clamp tube (2) and the core tube (3) are tightly joined to form a metal joint surface (8). The first connecting pin hole (102), the second connecting pin hole (203) and the third connecting pin hole (301) are connected by the assembly pin (6) to complete the assembly.

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