A friction riveting device and riveting method for thermoplastic carbon fiber composite material and aluminum alloy

Abstract

This invention discloses a friction riveting device for thermoplastic carbon fiber composite materials and aluminum alloys, comprising: a die, the lower part of which is a solid cylindrical structure, and the upper part has a circular groove at its center, the bottom surface of which protrudes upward in a conical shape; a pressure ring, which is a cylindrical structure with a cylindrical central hole at its center, the pressure ring being disposed above the die and coaxially disposed therewith; and a drive rod, which is coaxially disposed inside the central hole and is capable of rotational movement and axial feed movement along the central hole. This invention also discloses a riveting method for the friction riveting device for thermoplastic carbon fiber composite materials and aluminum alloys, which generates heat through rotational friction, and simultaneously adjusts the rotational speed and axial feed speed of the rivet to achieve the optimal riveting and welding state between the thermoplastic carbon fiber composite material sheet and the aluminum alloy sheet, thereby improving the joint strength and joint forming effect.

Description

Technical Field

[0001] The present invention relates to the technical field of riveting thermoplastic carbon fiber composite material plates and aluminum alloy plates, and more specifically, the present invention relates to a friction riveting device and a riveting method for thermoplastic carbon fiber composite material and aluminum alloy. Background Art

[0002] Under the requirement of lightweight automobiles, composite materials and light alloy materials are used as the main lightweight materials in light structure products. Thermoplastic carbon fiber composite materials have the remarkable characteristics of high toughness, high impact resistance and damage tolerance, unlimited prepreg storage period, short molding cycle, recyclability, easy repair, etc. They have the advantages of environmental protection, high efficiency and high performance, and are increasingly widely used in car bodies.

[0003] As thermoplastic carbon fiber composites are increasingly used in car bodies, the difficulty that comes with it is that when connecting with traditional metal materials, some common connection methods such as gluing, riveting and welding will have various technical and economic defects when connecting these lightweight materials, resulting in connection failure or extremely high costs. Carbon fiber composites are a brittle material with very little plastic deformation during deformation, and their ductility is much different from that of metal materials. In severe cases, cracks or even fractures may occur during riveting, affecting the performance of the joint. Therefore, new technologies are needed to solve these problems at the joint and further improve the performance of the joint. Summary of the invention

[0004] The purpose of the present invention is to design and develop a friction riveting device for thermoplastic carbon fiber composite materials and aluminum alloys, which utilizes the rotational friction of rivets to obtain a solid phase welding effect, while retaining the deformation self-locking characteristics of traditional riveting to improve the connection strength of the joint.

[0005] Another object of the present invention is to design and develop a riveting method for a friction riveting device of a thermoplastic carbon fiber composite material and an aluminum alloy. According to the characteristics of the composite material, the temperature of the riveting area is determined, and the temperature is adjusted by adjusting the rotation speed and axial feed speed of the driving rod to improve the riveting effect.

[0006] The technical solution provided by the present invention is:

[0007] A friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy, comprising:

[0008] The die has a solid cylindrical structure at the bottom and a circular groove at the center of the upper part, and the bottom surface of the circular groove is convex upward in a cone shape;

[0009] A blank holder ring, which is a cylindrical structure with a cylindrical center hole in the center, and the blank holder ring is arranged above the die and coaxially therewith;

[0010] A drive rod, which is coaxially arranged inside the central hole and can perform rotational motion and axial feed motion along the central hole;

[0011] A rivet, comprising a rivet cap, a rivet neck and a rivet foot connected in sequence, wherein the rivet cap and the driving rod are engaged with each other;

[0012] A connecting piece, which is arranged between the die and the blank holder;

[0013] A vacuum insulation pipe, which is interference-fitted inside the central hole;

[0014] A through hole, which is arranged at the lower part of the blank holder and connected to the center hole;

[0015] The rivet sleeve is sleeved on the outside of the nail cap, the nail neck and the driving rod, and the rivet sleeve is loosely matched with the vacuum insulation tube.

[0016] Preferably, the top diameter of the circular groove is 20 mm, and the depth of the circular groove is 0-10 mm.

[0017] Preferably, a tip is provided at the bottom of the driving rod, the tip is in the shape of a polygonal column, a polygonal pyramid or a cross, and the tip is engaged with the nail cap.

[0018] Preferably, the nail foot is provided with a fork, and the edge of the fork is arc-shaped.

[0019] Preferably, the height of the pressure ring is 20 mm, the diameter of the center hole is 20 mm, the diameter of the driving rod is 12 mm, the diameter of the rivet is the same as the diameter of the driving rod, the height of the rivet is 0-40 mm, the height of the rivet foot is 0-20 mm, the height of the rivet sleeve is 40 mm, and the diameter of the through hole is 1 mm.

[0020] Preferably, it also includes:

[0021] A temperature sensor is arranged at the connection between the via hole and the central hole;

[0022] A speed sensor, which is arranged on the driving rod and is used to detect the rotation speed and the descending speed;

[0023] A controller is connected to the temperature sensor and the speed sensor and is used to maintain the riveting temperature.

[0024] A riveting method of a friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy, using the friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy, comprises the following steps:

[0025] Step 1: placing the thermoplastic carbon fiber composite material plate and the aluminum alloy plate to be riveted between the concave die and the blank holder and pressing them tightly, wherein the thermoplastic carbon fiber composite material plate is on top;

[0026] Step 2: Assemble the rivet sleeve, the rivet and the driving rod, and drive the rivet to rotate and axially feed by the driving rod;

[0027] Step 3: After the rivet contacts the thermoplastic carbon fiber composite material plate and generates friction, the rotation speed and axial feed speed of the driving rod are adjusted according to the riveting temperature until the thermoplastic carbon fiber composite material plate and the aluminum alloy plate reach the optimal riveting state value, the driving rod stops moving, and the riveted joint is completed after cooling until the riveted joint state is stable.

[0028] Preferably, the rotation speed in step 3 satisfies:

[0029]

[0030] Where V f is the rotation speed, ξ is the rotation factor, T is the riveting temperature, F V is the initial applied pressure, m is the mass of the rivet, V b is the initial rotation speed of the driving rod, D V is the thickness of the thermoplastic carbon fiber composite material plate, D b is the thickness of the aluminum alloy plate;

[0031] The axial feed speed satisfies:

[0032]

[0033] Where V h is the axial feed speed, ψ is the axial feed factor, V k is the initial feed speed.

[0034] Preferably, the optimal riveting state is that the thermoplastic carbon fiber composite material plate and the aluminum alloy plate are combined with each other, a ring-shaped anchor hook shape appears between the rivet and the plate, and a mechanical self-locking effect is formed.

[0035] The beneficial effects of the present invention are:

[0036] 1. The friction riveting device for thermoplastic carbon fiber composite materials and aluminum alloys provided by the present invention overcomes the joint damage caused by the brittle properties of carbon fiber composite materials at room temperature. By rotating the rivet relative to the thermoplastic carbon fiber composite material plate, a certain temperature distribution is generated in the connection area of ​​the thermoplastic carbon fiber composite material plate, thereby improving the plastic flow effect of the thermoplastic carbon fiber plate and the joint forming effect.

[0037] 2. The riveting method of the friction riveting device of the thermoplastic carbon fiber composite material and the aluminum alloy provided by the present invention controls the rotation friction speed and feed speed of the rivet through the "speed-temperature" friction riveting monitoring system, controls the heat input in the riveting area, so that the riveting temperature can be maintained within a suitable range, avoids cracks and fractures of the plate caused by temperature inappropriateness, and improves the joint strength.

[0038] 3. The joint prepared by the riveting method of the friction riveting device of the thermoplastic carbon fiber composite material and the aluminum alloy provided by the present invention takes into account the advantages of riveting and welding methods, and overcomes some corresponding defects; compared with the traditional riveting technology, friction riveting does not destroy the integrity of the thermoplastic carbon fiber composite material plate, there is no excess material caused by punching, the noise is small, and it is green and environmentally friendly; compared with the gluing technology, friction riveting does not require adhesives, overcomes the safety hazards of the gluing bonding process in terms of high temperature resistance, impact resistance, and aging resistance. After the joint is formed, the rivet is fixed on the joint to ensure the bearing capacity of the joint; compared with special welding, the cost is relatively low, the process is simple, the production efficiency is high, it can be streamlined, and it is convenient for production line integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic cross-sectional structure diagram of the friction riveting device of the thermoplastic carbon fiber composite material and aluminum alloy according to the present invention.

[0040] Figure 2 It is a schematic structural diagram of the rivet driving system of the present invention.

[0041] Figure 3 It is a schematic structural diagram of the blank holding ring described in the present invention.

[0042] Figure 4 This is a process flow chart of the first step of friction riveting according to the present invention.

[0043] Figure 5 This is a process flow chart of the second step of the friction riveting process described in the present invention.

[0044] Figure 6 This is a process flow chart of the third step of the friction riveting process described in the present invention.

[0045] Figure 7 This is a process flow chart of the fourth step of the friction riveting process described in the present invention.

[0046] Figure 8 This is a forming effect diagram of the friction riveted joint described in the present invention.

[0047] Fig. 9 This is a diagram of the structure of the "speed-temperature" monitoring system described in the present invention. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0049] Thermoplastic composites can produce a plastic flow effect when heated to a certain temperature and recover their initial properties after cooling. Therefore, the softening flow properties of thermoplastic composites at high temperatures can be used to connect dissimilar materials.

[0050] like Figure 1 As shown, the friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy of the present invention specifically comprises: a die 111, a blank holder 121, a vacuum insulation tube 122, a through hole 123, a driving rod 131, a rivet 140, a rivet sleeve 150 and a connecting piece, wherein the lower part of the die 111 is a solid cylindrical structure, and a circular groove 112 is arranged at the center of the upper part, and the bottom surface of the circular groove 112 is upwardly protruding and conical; Figure 3 As shown, the blank holder 121 is a cylindrical structure and a cylindrical center hole 124 is arranged in the center. The blank holder 121 is arranged above the die 111 and coaxially therewith; the connecting part includes a thermoplastic carbon fiber composite material plate 161 and an aluminum alloy plate 162, and the thermoplastic carbon fiber composite material plate 161 and the aluminum alloy plate 162 are arranged between the die 111 and the blank holder 121, and the thermoplastic carbon fiber composite material plate 161 is on top; the vacuum insulation tube 122 is interference fit inside the center hole 124; the through hole 123 is arranged at the lower part of the blank holder 121 and connected to the center hole 124; the driving rod 131 is a cylindrical structure, coaxially arranged inside the center hole 124, and can perform rotational motion and axial feed motion along the center hole 124.

[0051] like Figure 2As shown, the bottom of the driving rod 131 is provided with a tip 132, which is a key part for cooperating with the rivet 140, and the shape of the tip 132 is a polygonal column, a polygonal pyramid or a cross; the rivet 140 includes a nail cap 141, a nail neck 142 and a nail foot 143 connected in sequence, the nail cap 141, the nail neck 142 and the nail foot 143 are an integrated structure, the nail cap 141 and the tip 132 are mutually engaged, and the rivet is driven to move through the cooperation of the tip 132 and the nail cap 141; and the rivet 140 is a solid rivet, and the overall diameter of the rivet 140 is consistent with that of the driving rod 131, which is 12 mm. A groove is provided above the nail cap 141, and the shape of the groove is consistent with that of the tip 132 and can cooperate with the driving rod 131; the nail foot 143 is provided with a fork The edge of the fork is transitioned with an arc segment. The fork design can increase the heat generated by the rotation friction of the rivet 140, and at the same time can reduce the weight of the rivet 140. The thickness of the fork of the nail foot 143 is 2mm, and the height can be set to 0-20mm (the specific height should be slightly smaller than the overall thickness of the plate. For example, if the thickness of the two plates is 10mm respectively, then the height of the fork of the nail foot 143 can be set to 16mm,), the height of the nail foot 143 is consistent with the total thickness of the plate, the height of the nail cap 141 and the nail neck 142 can be set to 20mm, and the overall height of the rivet 143 can be set to 0-40mm (the specific height is based on the height of the nail foot 143, and the height of the nail foot 143 plus the height of the nail cap 141 and the nail neck 142 is the overall height of the rivet 140).

[0052] Due to the rotary feeding motion of the rivet, there are certain requirements on the material of the rivet. As a preferred material, the rivet can be made of carbon steel, titanium alloy, nickel-based high-temperature alloy, cemented carbide and the like.

[0053] A rivet sleeve 150 is provided on the outside of the rivet 140. The rivet sleeve 150 is a hollow cylindrical structure. The inner diameter of the rivet sleeve 150 is 12 mm, which is the same size as the rivet 140 and the driving rod 131, and the outer diameter is 20 mm. The height of the rivet sleeve 150 is 40 mm. The lower part of the rivet sleeve 150 wraps the nail cap 141 and the nail neck 142, and the upper part can wrap the driving rod 131. The rivet sleeve 150 is provided with a thread inside to facilitate fastening the rivet 140 and the driving rod 131, and prevent the driving rod 131 and the rivet 140 from falling off during the friction riveting process.

[0054] The top diameter of the circular groove 112 is 20mm, and the depth of the circular groove 112 is 0-10mm (the depth of the circular groove 112 is based on the thickness of the plate. If the thickness of the plate is 10mm, the depth of the circular groove 112 is preferably 4mm). The volume of the circular groove 112 is roughly equivalent to the volume of the nail foot 143. The height of the pressure ring 121 is 20mm, the diameter of the center hole 124 is 20mm, the diameter of the driving rod 131 is 12mm, the diameter of the rivet 140 is the same as the diameter of the driving rod 131, the height of the rivet 140 is 0-40mm, the height of the nail foot 143 is 0-20mm, the height of the rivet sleeve 150 is 40mm, and the aperture of the through hole 123 is 1mm.

[0055] like Fig. 9 As shown, the friction riveting device of the thermoplastic carbon fiber composite material and the aluminum alloy described in the present invention also includes: a temperature sensor 171, a speed sensor 172 and a controller 173, the temperature sensor 171 is arranged at the connection between the through hole 123 and the center hole 124; the speed sensor 172 is arranged on the driving rod 131, and is used to detect the rotation speed and the descending speed; the controller 173 is connected to the temperature sensor 171 and the speed sensor 172, and is used to maintain the riveting temperature.

[0056] like Figure 4-7 As shown in the figure, the working process of the invention is: the driving rod 131 drives the rivet 140 to rotate and axially feed. With the axial movement of the rivet 140, the rivet 140 contacts the thermoplastic carbon fiber composite material plate 161, and friction begins. The rivet 140 rotates and the axial servo feed continues, and enters the thermoplastic carbon fiber composite material plate 161. At this time, the rotation speed of the rivet 140 is reduced compared to the initial speed, and the axial force is also continuously reduced. Under the action of pressure and friction heat, the plate is locally heated and softened, and the thermoplastic carbon fiber composite material plate 161 is Under the action of high temperature, plastic softening and flow phenomenon occurs, which improves the ductility of the plate. The rivet 140 is also softened at the same time. As the rivet 140 rotates and the axial feeding continues, the rivet 140 deforms and produces self-locking. The plastic flow phenomenon between the plates forms a riveting welding state in the connection area. When the connection area reaches the optimal riveting welding state value, the driving rod 131 stops moving, and the rivet 140 stops sharply relative to the thermoplastic carbon fiber composite material plate 161. After cooling and observation for a period of time, the joint is slowly taken out after the joint state is stable. The riveting joint is completed. Figure 8 shown.

[0057] The friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy provided by the present invention produces a certain temperature distribution in the connection area of ​​the thermoplastic carbon fiber composite material plate 161 through the rotational friction of the rivet 140 relative to the thermoplastic carbon fiber composite material plate 161, and produces plasticization flow of the thermoplastic carbon fiber composite material plate 161 through the axial feeding and relative rotation of the rivet 140, thereby generating a dynamic riveting state, which can produce a solid phase welding effect, significantly improve the connection strength of the connection joint, and does not destroy the integrity of the thermoplastic carbon fiber composite material plate 161, thereby ensuring the bearing capacity of the structure.

[0058] The present invention provides a riveting method of a friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy, using the friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy, comprising the following steps:

[0059] Step 1: placing the thermoplastic carbon fiber composite material plate and the aluminum alloy plate to be riveted between the concave die and the blank holder and pressing them tightly, wherein the thermoplastic carbon fiber composite material plate is on top;

[0060] Step 2: Assemble and center the rivet sleeve, rivet and driving rod, and drive the rivet to rotate by the driving rod while servo feeding in the axial direction;

[0061] Step 3: When the rivet contacts the thermoplastic carbon fiber composite material plate and generates friction, and then enters the thermoplastic carbon fiber composite material plate, the rivet rotation speed is reduced compared to the initial speed, and the axial force is also continuously reduced. Under the action of pressure and friction heat, the thermoplastic carbon fiber composite material plate is locally heated and softened. The thermoplastic carbon fiber composite material plate produces a plastic softening flow phenomenon under the action of high temperature, which improves the ductility of the plate, and the rivet is also softened at the same time. Fig. 9 As shown, at the same time, the "speed-temperature" monitoring system detects the temperature of the riveting area, determines whether the temperature is appropriate, and adjusts the speed of the driving rod in real time, so that the riveting temperature can be kept within an appropriate range, ensuring the performance of the plate and improving the joint strength; as the rivet rotates and the axial feed continues, the rivet deforms and self-locks, and a riveted welding state is formed in the connection area. The rotation speed and axial feed speed of the driving rod are adjusted according to the riveting temperature until the connection area between the thermoplastic carbon fiber composite material plate and the aluminum alloy plate reaches the optimal riveted welding state value, the driving rod stops moving, the rivet stops sharply relative to the base material, and is cooled and observed for a period of time. After the joint state is stable, the joint is slowly taken out, and the riveted joint is completed.

[0062] The rotation speed in step 3 satisfies:

[0063]

[0064] Where V fis the rotation speed, ξ is the rotation factor, T is the riveting temperature, F V is the initial applied pressure, m is the mass of the rivet, V b is the initial rotation speed of the driving rod, D V is the thickness of the thermoplastic carbon fiber composite material plate, D b is the thickness of the aluminum alloy plate;

[0065] The axial feed speed satisfies:

[0066]

[0067] Where V h is the axial feed speed, ψ is the axial feed factor, V k is the initial feed speed.

[0068] Preferably, the initial rotation speed of the rivet is 300-10000r / min, the initial applied pressure is 0-5000N, different temperature ranges are taken according to different types of carbon fiber, the reference temperature range of the riveting temperature can be set to 100℃~120℃, the range of the rivet axial feed speed is: 500mm / s~800mm / s, and the range of the rivet rotation speed is: 300r / min~10000r / min.

[0069] The optimal riveting state is that the thermoplastic carbon fiber composite material plate and the aluminum alloy plate are combined with each other, a ring-shaped anchor hook shape appears between the rivet and the plate, and a mechanical self-locking effect is formed.

[0070] Another object of the present invention is to design and develop a riveting method for a friction riveting device of a thermoplastic carbon fiber composite material and an aluminum alloy. According to the characteristics of the composite material, the temperature of the riveting area is determined, and the temperature is adjusted by adjusting the rotation speed and axial feed speed of the driving rod to improve the riveting effect.

[0071] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A riveting method of a friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy, characterized in that: A friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy is used, and the friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy comprises: The die has a solid cylindrical structure at the bottom and a circular groove at the center of the upper part, and the bottom surface of the circular groove is convex upward in a cone shape; A blank holder ring, which is a cylindrical structure with a cylindrical center hole in the center, and the blank holder ring is arranged above the die and coaxially therewith; A drive rod, which is coaxially arranged inside the central hole and can perform rotational motion and axial feed motion along the central hole; A rivet, comprising a rivet cap, a rivet neck and a rivet foot connected in sequence, wherein the rivet cap and the driving rod are engaged with each other; A connecting piece, which is arranged between the die and the blank holder; A vacuum insulation pipe, which is interference-fitted inside the central hole; A through hole, which is arranged at the lower part of the blank holder and connected to the center hole; A rivet sleeve, which is sleeved on the outside of the rivet cap, the rivet neck and the driving rod, and the rivet sleeve is loosely matched with the vacuum insulation tube; The riveting method of the friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy comprises the following steps: Step 1: placing the thermoplastic carbon fiber composite material plate and the aluminum alloy plate to be riveted between the concave die and the blank holder and pressing them tightly, wherein the thermoplastic carbon fiber composite material plate is on top; Step 2: Assemble the rivet sleeve, the rivet and the driving rod, and drive the rivet to rotate and axially feed by the driving rod; Step 3: When the rivet contacts the thermoplastic carbon fiber composite material plate and generates friction, the rotation speed and axial feed speed of the driving rod are adjusted according to the riveting temperature until the thermoplastic carbon fiber composite material plate and the aluminum alloy plate reach the optimal riveting state value, the driving rod stops moving, and after cooling until the riveted joint state is stable, the riveted joint is completed; Wherein, the rotation speed satisfies: Where V f is the rotation speed, ξ is the rotation factor, T is the riveting temperature, F V is the initial applied pressure, m is the mass of the rivet, V b is the initial rotation speed of the driving rod, D V is the thickness of the thermoplastic carbon fiber composite material plate, D b is the thickness of the aluminum alloy plate; The axial feed speed satisfies: Where V h is the axial feed speed, ψ is the axial feed factor, V k is the initial feed speed.

2. The riveting method of the friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy according to claim 1, characterized in that: The top surface diameter of the circular groove is 20 mm, and the depth of the circular groove is 0-10 mm.

3. The riveting method of the friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy according to claim 2, characterized in that: The bottom of the driving rod is provided with a tip, the shape of the tip is a polygonal column, a polygonal pyramid or a cross, and the tip is engaged with the nail cap.

4. The riveting method of the friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy according to claim 3, characterized in that: The nail foot is provided with a fork, and the edge of the fork is arc-shaped.

5. The riveting method of the friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy according to claim 4, characterized in that: The height of the pressure ring is 20mm, the diameter of the center hole is 20mm, the diameter of the driving rod is 12mm, the diameter of the rivet is the same as the diameter of the driving rod, the height of the rivet is 0-40mm, the height of the rivet foot is 0-20mm, the height of the rivet sleeve is 40mm, and the diameter of the through hole is 1mm.

6. The riveting method of the friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy according to claim 5, characterized in that: The friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy also includes: A temperature sensor is arranged at the connection between the via hole and the central hole; A speed sensor, which is arranged on the driving rod and is used to detect the rotation speed and the descending speed; A controller is connected to the temperature sensor and the speed sensor and is used to maintain the riveting temperature.

7. The riveting method of the friction riveting device for thermoplastic carbon fiber composite material and aluminum alloy according to claim 1, characterized in that: The optimal riveting state is that the thermoplastic carbon fiber composite material plate and the aluminum alloy plate are combined with each other, a ring-shaped anchor hook shape appears between the rivet and the plate, and a mechanical self-locking effect is formed.

Images