A riveting device using carbon fiber rivets and an electric pulse forming method

Abstract

The application relates to the technical field of material plastic forming, and provides a riveting device using carbon fiber rivets and an electric pulse forming method. The riveting device comprises an upper die and a lower die, the upper die is detachably connected with an upper electrode, the lower die is detachably connected with a lower electrode, the upper electrode and the lower electrode are respectively connected with an alternating current power supply; a first plate and a second plate are limitingly arranged between the upper die and the lower die, a carbon fiber rod is arranged in a prefabricated hole of the first plate and the second plate, and the carbon fiber rod is deformed under the action of the upper electrode and the lower electrode to complete the riveting of the first plate and the second plate. The beneficial effects are as follows: the carbon fiber rivet arranged with carbon fibers is used as a riveting piece, compared with other riveting connecting pieces, potential corrosion can be reduced, and the service life of the material is prolonged. When the carbon fiber rivet is deformed, the carbon fibers at the end of the carbon fiber rivet are scattered from the center to the periphery, the curling of the carbon fibers is reduced, the generation probability of defects such as gaps and carbon fiber separation is reduced, and the joint quality is improved.

Description

Technical Field

[0001] This invention relates to the field of material plastic forming technology, specifically to a riveting device using carbon fiber rivets and an electro-pulse forming method. Background Technology

[0002] In recent years, to achieve energy conservation and emission reduction, industries such as automotive and aerospace are moving towards lightweighting. Carbon fiber reinforced resin matrix composites, due to their advantages such as light weight, high strength, and corrosion resistance, have significant advantages and prospects as structural and connecting materials for achieving lightweighting. Furthermore, riveting, as a material joining process, produces joints with excellent joint strength and sealing performance, which is crucial in the aerospace field.

[0003] Currently, metal fasteners are mainly used for connecting composite structural components. However, this method has many drawbacks, such as a large potential difference between the metal fastener and the composite structural component, which can lead to corrosion of the composite material, affecting its mechanical properties and joint sealing. The use of metal fasteners also increases the overall weight of the component. To address these issues, carbon fiber reinforced resin matrix composites have been used as fasteners. However, problems remain, including immature riveting technology, difficulty in controlling joint quality, and cumbersome processes. A prominent problem is that when carbon fiber composites are formed into rivets, the carbon fibers become irregularly curled and deformed, creating voids in the carbon fiber composite rivets, and even causing the carbon fibers to separate from the matrix, severely affecting their mechanical properties. Therefore, this invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a riveting device and an electro-pulse forming method using carbon fiber rivets to solve the technical problems existing in the prior art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a riveting device using carbon fiber rivets, comprising: an upper mold and a lower mold, wherein an upper electrode is detachably connected to the upper mold, and a lower electrode is detachably connected to the lower mold, wherein the upper electrode and the lower electrode are respectively connected to an AC power supply;

[0006] A first plate and a second plate are installed between the upper mold and the lower mold, and carbon fiber rods are placed in the pre-made holes of the first plate and the second plate. The carbon fiber rods complete the riveting of the first plate and the second plate under the action of the upper electrode and the lower electrode.

[0007] In an optional embodiment, the upper mold is detachably divided into a top mold and a connecting seat, and the upper electrode is snapped between the top mold and the connecting seat.

[0008] In an optional embodiment, the lower mold is detachably divided into a bottom mold and a connecting flange, and the lower electrode is snapped between the bottom mold and the connecting flange.

[0009] In an optional embodiment, the first plate and the second plate are positioned between the connecting flange and the sleeve, and the upper electrode is inserted into the mold cavity of the sleeve.

[0010] In an optional embodiment, the upper electrode and the lower electrode are provided with outwardly extending conical positioning cores; and positioning blind holes are provided at both ends of the carbon fiber rod.

[0011] In an optional embodiment, the upper and lower electrodes are made of brass or stainless steel, and the upper mold, lower mold, and sleeve are made of high-temperature glass fiber composite insulating material.

[0012] In an optional embodiment, the first and second plates are carbon fiber reinforced resin-based composite material plates, and the resin is one of polyphenylene sulfide, polyether ether ketone, polylactic acid, and epoxy resin.

[0013] In an optional embodiment, the carbon fiber rod is a unidirectional carbon fiber or a braided carbon fiber reinforced thermoplastic composite material.

[0014] In an optional embodiment, the output voltage of the AC power supply is 0-50V, the output current is 0-20A, and the output waveform of the AC power supply is one of square wave, trapezoidal wave, and sawtooth wave.

[0015] On the other hand, the present invention also provides an electropulse forming method using the riveting device described above, comprising the following steps:

[0016] S1, Assemble the lower mold together with the lower electrode and the negative terminal of the AC power supply, and place it horizontally;

[0017] S2, stack the first plate and the second plate with pre-made holes on the lower mold, and insert carbon fiber rods into the pre-made holes so that the carbon fiber rods contact the lower electrode;

[0018] S3, place the sleeve above the first and second plates to be connected, and connect it to the connecting flange of the lower mold with bolts to clamp the first and second plates;

[0019] S4, assemble the upper mold, upper electrode, and positive terminal of the AC power supply together, and insert the upper electrode into the mold cavity of the sleeve so that the upper electrode contacts the carbon fiber rod;

[0020] S5, turn on the AC power supply to allow pulse current to flow through the carbon fiber rod, providing forming heat;

[0021] S6, Use a pressure device to press down the upper mold, so that the carbon fiber rod fills the mold cavity and forms the shape;

[0022] S7. After holding the pressure for a period of time, turn off the AC power supply and allow it to cool and solidify naturally.

[0023] S8, remove the device, disassemble the upper mold, sleeve, and lower mold, and complete the riveting.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) The carbon fiber rivets used in this invention, with carbon fibers arranged in the same pattern, are suitable for connecting carbon fiber composite plates. Compared with other riveting connectors, they can reduce potential corrosion and improve the service life of the material. Furthermore, when the carbon fiber rivets are deformed, the carbon fibers at the ends of the rivets spread outwards from the center, reducing carbon fiber curling and thus lowering the probability of defects such as voids and carbon fiber separation, thereby improving the joint quality. The carbon fiber rivets are cylindrical carbon fiber rods that, through simple machining, expose some carbon fibers, improving the heating efficiency of the pulsed current.

[0026] (2) This invention uses electric pulses to provide the heat required for carbon fiber rivet forming, resulting in a rapid heating rate and high heat utilization. Compared with other heating methods, this reduces damage to the plates to be joined. After the rivet reaches the forming temperature, it does not need to be transferred to a forming mold for forming; it can be formed directly in the device, simplifying the process and improving production efficiency. In addition, the electroplasticity of the electric pulses improves the deformation capacity of the carbon fiber rivet to a certain extent, reduces the riveting force, and further improves the riveting efficiency. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of a riveting device using carbon fiber rivets provided in one embodiment of the present invention.

[0029] Figure 2 This is a partially enlarged structural diagram of a riveting device using carbon fiber rivets provided in one embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram showing the riveting process completed using a riveting device with carbon fiber rivets according to an embodiment of the present invention.

[0031] The attached diagram is labeled as follows: upper mold 1, upper electrode 2, sleeve 3, carbon fiber rod 4, plate to be connected 5, lower electrode 6, lower mold 7, AC power supply 8. Detailed Implementation

[0032] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it may be directly or indirectly located on that other component. When a component is referred to as "connected to" another component, it may be directly or indirectly connected to that other component. The terms "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate orientations or positions based on the accompanying drawings, and are for ease of description only, and should not be construed as limiting the technical solution. The terms "first" and "second" 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. "A plurality" means two or more, unless otherwise explicitly defined.

[0034] Example 1

[0035] Please see the appendix Figure 1-3 The purpose of this embodiment is to provide a riveting device using carbon fiber rivets, including: an upper mold 1 and a lower mold 7. An upper electrode 2 is detachably connected to the upper mold 1, and a lower electrode 6 is detachably connected to the lower mold 7. The upper electrode 2 and the lower electrode 6 are respectively connected to an AC power supply 8. The output voltage of the AC power supply 8 is 0-50V, the output current is 0-20A, and the output waveform of the AC power supply 8 is one of square wave, trapezoidal wave, and sawtooth wave.

[0036] Specifically, the upper mold 1 is detachably divided into a top mold and a connecting seat, with the upper electrode 2 snapped between the top mold and the connecting seat. The lower mold 7 is detachably divided into a bottom mold and a connecting flange, with the lower electrode 6 snapped between the bottom mold and the connecting flange. This structural design facilitates the installation and removal of the two electrodes. The upper electrode 2 and the lower electrode 6 are made of brass or stainless steel, while the upper mold 1, lower mold 7, and sleeve 3 are made of high-temperature glass fiber composite insulating material.

[0037] In this embodiment, a first plate and a second plate are installed between the upper mold 1 and the lower mold 7. The first plate and the second plate are carbon fiber reinforced resin-based composite materials, and the resin is one of polyphenylene sulfide, polyetheretherketone, polylactic acid, and epoxy resin. Carbon fiber rods 4 are placed in pre-drilled holes in the first plate and the second plate. The carbon fiber rods 4 are unidirectional carbon fiber or braided carbon fiber reinforced thermoplastic composite materials. The carbon fiber rods 4 complete the riveting of the first plate and the second plate under the action of the upper electrode 2 and the lower electrode 6. The carbon fiber rivets are cylindrical carbon fiber rods 4. After simple mechanical processing, some carbon fibers at both ends of the rod are exposed, which improves the heating efficiency of the pulse current. The exposed areas need to be uniform, otherwise the joint quality will be affected. The method for uniformly exposing the exposed areas involves uniformly grinding each end of the rod, with an even number of exposed areas at each end, preferably eight. Adjacent exposed areas are evenly spaced, and each exposed area has an equal area; preferably, each exposed area is fan-shaped. During energization, the area near the center of each end of the rod first contacts the electrode. The exposed areas then contact the electrode radially from the center, with the contact area between each exposed area and the electrode gradually increasing uniformly. When the electrode first contacts the end of the rod, the current in the electrode is small due to the small contact area. As the contact area increases, the current in the electrode increases linearly. Through coordinated adjustment of the current in the electrode and the contact area between the electrode and the exposed area, the electrode descent speed remains constant, while ensuring uniform local heat absorption of the rod. This effectively controls the deformation of the carbon fiber rivet and ensures the riveting quality.

[0038] It should be noted that the upper electrode 2 and the lower electrode 6 are provided with outwardly extending conical positioning cores; the two ends of the carbon fiber rod 4 are respectively provided with positioning blind holes. Under the action of the conical positioning cores and positioning blind holes, when the carbon fiber rivet is deformed, the carbon fiber at the end of the carbon fiber rivet spreads out from the center to the surrounding area, reducing the curling of the carbon fiber, thereby reducing the probability of defects such as voids and carbon fiber separation, and improving the joint quality.

[0039] Example 2

[0040] Please see the appendix Figure 1-3 The purpose of this embodiment is to provide an electrical pulse forming method using the riveting device described above, comprising the following steps:

[0041] S1. Assemble the lower mold 7, lower electrode 6, and negative terminal of AC power supply 8 together and place them horizontally.

[0042] S2, stack the first plate and the second plate with pre-made holes on the lower mold 7, and insert the carbon fiber rod 4 into the pre-made holes so that the carbon fiber rod 4 contacts the lower electrode 6;

[0043] S3, place the sleeve 3 above the first plate and the second plate to be connected, and connect it to the connecting flange of the lower mold 7 with bolts to clamp the first plate and the second plate;

[0044] S4, assemble the upper mold 1, upper electrode 2, and positive electrode of AC power supply 8 together, and insert the upper electrode 2 into the mold cavity of sleeve 3 so that the upper electrode 2 contacts the carbon fiber rod 4.

[0045] S5, turn on the AC power supply 8 to allow the pulse current to flow through the carbon fiber rod 4, providing forming heat;

[0046] S6, use a pressure device to press down the upper mold 1, so that the carbon fiber rod 4 fills the mold cavity and forms the shape;

[0047] S7, after holding the pressure for a period of time, turn off the AC power 8, and allow it to cool and solidify naturally;

[0048] S8, remove the device, disassemble the upper mold 1, sleeve 3, and lower mold 7 to complete the riveting.

[0049] It should be noted that the upper and lower electrodes, in addition to their conductive function, also have a stamping function; other components are made of insulating materials, ensuring that most of the current flows only through the carbon fiber rod, thus reducing the impact on the plates to be connected.

[0050] It is worth mentioning that the unique mold structure reduces defects such as voids and carbon fiber separation generated during the deformation of the carbon fiber rods, thus improving the riveting quality. Furthermore, the use of electropulse-assisted riveting utilizes the Joule effect to provide the necessary heat for forming and its electroplasticity to enhance the deformation capacity of the carbon fiber rods and reduce internal damage. In addition, compared to traditional riveting, pre-fabricated rivets are not required, simplifying the process and improving its operability and standardization.

[0051] Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention shall be included within the scope of protection of this invention.

Claims

1. A riveting device using carbon fiber rivets, characterized in that, include: The upper mold (1) and the lower mold (7) are provided. The upper electrode (2) is detachably connected in the upper mold (1), and the lower electrode (6) is detachably connected in the lower mold (7). The upper electrode (2) and the lower electrode (6) are respectively connected to an AC power supply (8). A first plate and a second plate are installed between the upper mold (1) and the lower mold (7). A carbon fiber rod (4) is placed in the pre-made hole of the first plate and the second plate. The carbon fiber rod (4) completes the riveting of the first plate and the second plate under the action of the upper electrode (2) and the lower electrode (6). The upper electrode (2) and the lower electrode (6) are provided with outwardly extending conical positioning cores; the two ends of the carbon fiber rod (4) are respectively provided with positioning blind holes; The carbon fiber rod (4) has some carbon fiber exposed at both ends, and the exposed area is uniform.

2. The riveting device using carbon fiber rivets as described in claim 1, characterized in that, The upper mold (1) is detachably divided into a top mold and a connecting seat, and the upper electrode (2) is snapped between the top mold and the connecting seat.

3. The riveting device using carbon fiber rivets as described in claim 2, characterized in that, The lower mold (7) is detachably divided into a bottom mold and a connecting flange, and the lower electrode (6) is snapped between the bottom mold and the connecting flange.

4. The riveting device using carbon fiber rivets as described in claim 3, characterized in that, The first plate and the second plate are positioned between the connecting flange and the sleeve (3), and the upper electrode (2) is inserted into the mold cavity of the sleeve (3).

5. The riveting device using carbon fiber rivets as described in claim 4, characterized in that, The upper electrode (2) and lower electrode (6) are made of brass or stainless steel, and the upper mold (1), lower mold (7) and sleeve (3) are made of high-temperature glass fiber composite insulating material.

6. The riveting device using carbon fiber rivets as described in claim 1, characterized in that, The first and second plates are carbon fiber reinforced resin-based composite material plates, and the resin is one of polyphenylene sulfide, polyether ether ketone, polylactic acid, and epoxy resin.

7. The riveting device using carbon fiber rivets as described in claim 1, characterized in that, The carbon fiber rod (4) is a unidirectional carbon fiber or woven carbon fiber reinforced thermoplastic composite material.

8. The riveting device using carbon fiber rivets as described in claim 1, characterized in that, The output voltage of the AC power supply (8) is 0-50V, the output current is 0-20A, and the output waveform of the AC power supply (8) is one of square wave, trapezoidal wave, and sawtooth wave.

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