Metal and composite self-piercing rivet and device

Abstract

The utility model discloses the technical field of metal and composite material's connection is metal and composite material's self -piercing riveting rivet and device, including for the upper die of material punching and for the lower die of material cutting, still include: fixedly installed on the upper die for the edge ring of plate material compression, the coaxial sliding of edge ring has for the material punching die of material punching, the end fixed mounting of material punching die has the rivet, the detachable installation of material punching die has for the heating of heating spare, the material cutting die of floating setting in the lower die. The utility model realizes the on -line blanking of composite material through the cooperation of rivet riveting area and material cutting die, need not previously to the composite material and set up prefabricated hole, not only simplifies the riveting procedure, reduced the hole difficulty to the hole, still reduced the additional defect risk of traditional drilling process, is helpful to the production efficiency and process stability of promotion.

Description

Technical Field

[0001] This utility model relates to the field of metal and composite material joining technology, and in particular to a rivet and device for self-piercing riveting of metal and composite materials. Background Technology

[0002] Carbon fiber reinforced composite materials have advantages such as high specific strength, high specific modulus, excellent fatigue resistance, low coefficient of thermal expansion and good corrosion resistance. They are often used in combination with metal materials such as aluminum alloys and applied to key parts such as automobile bodies and aerospace components by riveting.

[0003] However, existing riveting technologies have significant drawbacks: on the one hand, carbon fiber composites have poor plasticity, and during the riveting process, damage such as fiber breakage, matrix cracking, interface degumming, and delamination can easily occur, directly reducing the mechanical properties of the joint or even causing joint failure; on the other hand, in order to achieve the riveting of metal and composite materials, existing technologies require pre-drilling holes in the composite material, which not only increases the complexity of the riveting process but also increases the difficulty of aligning the tooling and the holes, reduces production efficiency, and is prone to causing additional defects due to hole misalignment. Therefore, we urgently need rivets and devices for self-piercing riveting of metal and composite materials to solve the above problems. Utility Model Content

[0004] To address the shortcomings of existing technologies, this utility model provides a rivet and device for self-piercing riveting of metals and composite materials. By heating the upper mold to ensure the plasticity of the metal and cooling the lower mold with liquid nitrogen to enhance the brittleness of the composite material, and by working together with a specially structured rivet and a cutting die, self-piercing riveting without pre-drilled holes can be achieved, reducing cracking and delamination of the composite material and improving riveting efficiency and joint performance.

[0005] The purpose of this utility model is achieved as follows: it includes an upper die for punching and a lower die for cutting, and further includes: a pressure ring fixedly installed on the upper die for pressing the sheet metal, a punching die for punching is coaxially slidable inside the pressure ring, a rivet is fixedly installed at the end of the punching die, and a heating element for heating is detachably installed inside the punching die; a cutting die floatingly installed inside the lower die, a support die for supporting the material floatingly installed inside the cutting die, a guide area for liquid nitrogen flow is provided inside the support die, and the support die is connected to an external conveying unit through an air pipe penetrating the outer shell of the lower die.

[0006] Optionally, the rivet is a solid flange structure, and the rivet has a flange, a necking area and a riveting area arranged sequentially along its axis.

[0007] Optionally, the heating element includes a placement groove formed on the stamping die, in which a heater electrically connected to an external power supply unit is fixedly installed. When the heater is working, heat is transferred to the rivet and a heating zone is formed.

[0008] Optionally, a first floating groove is provided in the lower mold, and the cutting mold is slidably connected in the first floating groove. A first spring is provided in the first floating groove, and the two ends of the first spring are respectively connected to the cutting mold and the bottom wall of the first floating groove.

[0009] Optionally, the upper part of the cutting die is provided with a second floating groove, the support die is slidably connected in the second floating groove, the second floating groove is provided with a second spring, and the two ends of the second spring are respectively connected to the support die and the bottom wall of the second floating groove.

[0010] Optionally, the top of the support mold is provided with an annular step, and when the material abuts against the upper surface of the support mold, an annular storage area for containing liquid nitrogen is formed at the gap between the material and the annular step.

[0011] Optionally, the guide area includes an axial air passage formed within the support mold, the axial air passage being arranged along the axis of the annular step, and horizontal air passages being formed equidistantly in the annular shape within the support mold, the outlet end of the horizontal air passage being connected to the protrusion of the annular step, and the inlet end of the horizontal air passage being connected to the axial air passage.

[0012] Compared with the prior art, the beneficial effects of this utility model are as follows: 1. This utility model achieves online punching of composite materials through the cooperation of the rivet punching area and the cutting die, eliminating the need to pre-drill holes in the composite material. This not only simplifies the riveting process and reduces the difficulty of drilling, but also reduces the additional defect risks brought about by traditional drilling processes, which helps to improve production efficiency and process stability.

[0013] 2. This utility model uses a synergistic design of heating the upper mold to enhance the plasticity of the metal plate and cooling the lower mold with liquid nitrogen to enhance the brittleness of the composite material. Combined with the structure of the metal plate flanging to wrap the opening area of ​​the composite material, it significantly reduces defects such as fiber breakage, delamination, and degumming during the punching of the composite material. At the same time, through the interlocking of the rivets and the metal plate, it significantly improves the static tensile performance and fatigue performance of the riveted joint, meeting the requirements for high-reliability connections. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, 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 embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the orthographic structure of the upper and lower molds provided by this utility model; Figure 2This is a cross-sectional view of the upper and lower molds provided by this utility model; Figure 3 This is a schematic diagram of the support mold structure provided by this utility model; Figure 4 This is a schematic diagram of the cross-sectional structure of the axial air passage and the horizontal air passage provided by this utility model; Figure 5 This is a partially enlarged structural schematic diagram provided by this utility model; Figure 6 This is a schematic diagram of the internal structure of the support mold provided by this utility model; Figure 7 This is a schematic diagram of the riveting effect provided by this utility model; Figure 8 This is a schematic diagram of the punching and riveting process provided by this utility model.

[0016] In the diagram: 1. Upper die; 2. Lower die; 3. Pressure ring; 4. Punching die; 5. Rivet; 51. Flange; 52. Necked area; 53. Riveting area; 6. Cutting die; 7. Support die; 8. Placement slot; 9. Heater; 10. First floating slot; 11. First spring; 12. Second floating slot; 13. Second spring; 14. Annular step; 15. Axial air passage; 16. Horizontal air passage. Detailed Implementation

[0017] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0018] like Figure 1-8 As shown in the figure, the present invention provides a self-piercing riveting rivet 5 and device for metal and composite materials, including an upper die 1 for punching and a lower die 2 for cutting.

[0019] Here, the upper die 1 is the core carrier of the stamping driving force. It is made of high-strength alloy steel (such as Cr12MoV) to reduce deformation during riveting. The lower end face of the upper die 1 is fixedly connected to the pressure ring 3 by bolts. The pressure ring 3 is a ring structure with an inner diameter slightly larger than the outer diameter of the stamping die 4 (the gap is controlled at 0.05~0.1mm), which helps the stamping die 4 to slide smoothly along the axis of the pressure ring 3. The area where the lower end face of the pressure ring 3 contacts the upper metal plate is a planar structure. When the pressure ring 3 is pressed down, a clamping force of 5-10kN can be applied to the "metal plate-composite material" composite plate, so that the composite plate remains relatively fixed during subsequent stamping and riveting processes.

[0020] Furthermore, the core of the lower mold 2 is the lower mold shell, which is made of the same high-strength alloy steel as the upper mold 1. The lower mold shell has a first floating groove 10, which is a cylindrical groove. The cutting mold 6 is slidably connected in the first floating groove 10. The cutting mold 6 has a ring structure, and the inner hole size matches the riveting area 53 of the rivet 5. The inner wall is a cutting edge structure, which helps to cut the composite material fibers during punching. The first spring 11 is set at the bottom of the first floating groove 10, and its two ends are respectively connected to the cutting mold 6 and the bottom wall of the floating groove. The spring stiffness is greater than that of the second spring 13. In the initial state, the upper surface of the cutting mold 6 is slightly higher than the lower mold shell.

[0021] Furthermore, the annular cutting edge of the cutting die 6 cooperates with the riveting area 53 of the rivet 5 to form an "annular shear" on the composite material, which helps the composite material to break neatly along the cutting edge and reduces the "tearing" damage to the fibers. The stiffness design of the first spring 11 is adapted to the riveting process. During the blanking stage, the cutting die 6 can move down synchronously with the support die 7, which helps to ensure that the composite material is fully blanked. During the metal flanging stage, the first spring 11 can provide a reaction force to create a gap between the cutting die 6 and the composite material plate, providing space for the deformation of the metal plate and helping to achieve good results in the blanking of the composite material.

[0022] It also includes a pressure ring 3 that is fixedly installed on the upper mold 1 to press the sheet metal.

[0023] Here, the plywood forms a full circumferential positioning, reducing the probability of lateral displacement of the material during punching and rivet 5 pressing down, thus effectively alleviating the problem of "difficulty in aligning pre-drilled holes with rivet 5" in traditional processes; at the same time, the coaxial sliding fit between the pressure ring 3 and the punching die 4 helps to ensure the axial accuracy of rivet 5 when it is pressed down (the deviation can be controlled within ≤0.03mm), reducing the risk of excessive local extrusion of composite materials due to rivet 5 misalignment, thereby reducing cracking and laying the foundation for subsequent precise riveting.

[0024] The blanking ring 3 has a blanking die 4 that slides coaxially inside it. The blanking die 4 has a rivet 5 fixedly installed at its end. The rivet 5 is a solid structure with a flange 51. The rivet 5 has a flange 51, a necking area 52 and a riveting area 53 arranged sequentially along its axis.

[0025] Here, the stamping die 4 has a cylindrical structure. The upper end is connected to the upper die drive system (such as a hydraulic cylinder), and the lower end is fixedly installed with rivets 5 through an interference fit, which helps to ensure that rivets 5 are not easily loosened during the pressurization process. The inner cavity of the stamping die 4 has a placement groove 8 along the axis. The size of the placement groove 8 matches that of the heater 9. The heater 9 uses an electric heating wire (power 300-500W) and is connected to an external power supply unit and temperature control system through a wire. During operation, the heat generated by the heater 9 can be conducted to the rivets 5 through the stamping die 4, so that the temperature of the rivets 5 is stabilized at 80-200℃ (adjusted according to the metal plate material, such as 120-150℃ for aluminum alloy plates). At the same time, the heat can be transferred to the upper metal plate to improve the plasticity of the metal plate.

[0026] Furthermore, the design of the heating element built into the stamping die 4 enables precise heat transfer, mainly heating the rivet 5 and the upper metal plate, reducing the possibility of heat conduction to the composite material and causing the matrix to soften; after heating, the yield strength of the metal plate can be reduced by 30% to 50%, and the plasticity is significantly improved, which helps the metal plate to expand and fold along the gap in the subsequent riveting process, laying the foundation for the metal plate to wrap the opening area of ​​the composite material.

[0027] Furthermore, the rivet 5 is made of high-strength aluminum alloy (such as 6061-T6) or titanium alloy, and has a solid structure. It is divided into a flange 51, a necking area 52, and a riveting area 53 along the axis. The diameter of the flange 51 is larger than that of the necking area 52, and its lower end face can be completely fitted with the upper metal plate, which helps to ensure uniform force after riveting. The diameter of the necking area 52 is smaller than that of the flange 51, which can reserve space for the deformation and embedding of the upper metal plate. The riveting area 53 is a pointed structure, and its hardness is improved through heat treatment (such as HV300 or above), which can realize the piercing and punching of composite material plates.

[0028] It is worth noting that the solid rivet 5 has higher shear strength than the hollow rivet 5, and can better withstand the dynamic loads of automotive and aerospace components; the fitting design of the flange 51 and the metal plate can disperse the local pressure at the riveting joint and reduce the possibility of indentation on the metal plate; the necking area 52 can accommodate the deformed metal plate and form a relatively stable interlocking structure, which, together with the fitting effect of the flange 51, helps to improve the connection strength of the joint; the high-hardness tip of the punching area 53 can achieve precise piercing of the composite material, making the composite material punching process smoother.

[0029] The stamping die 4 is detachably equipped with a heating element for heating. The heating element includes a placement groove 8 opened on the stamping die 4. A heater 9 electrically connected to an external power supply unit is fixedly installed in the placement groove 8. When the heater 9 is working, heat is transferred to the rivet 5 and a heating zone is formed.

[0030] A cutting mold 6 is floatingly disposed within the lower mold 2. A support mold 7 for supporting the material is floatingly disposed within the cutting mold 6. A first floating groove 10 is provided in the lower mold 2. The cutting mold 6 is slidably connected within the first floating groove 10. A first spring 11 is disposed within the first floating groove 10. The two ends of the first spring 11 are respectively connected to the cutting mold 6 and the bottom wall of the first floating groove 10. A second floating groove 12 is provided at the upper part of the cutting mold 6. The support mold 7 is slidably connected within the second floating groove 12. A second spring 13 is disposed within the second floating groove 12. The two ends of the second spring 13 are respectively connected to the support mold 7 and the bottom wall of the second floating groove 12.

[0031] Here, the support mold 7 is a cylindrical structure that is slidably connected in the second floating groove 12 of the cutting mold 6. An annular step 14 is provided at the top, and the annular step 14 and the inner wall of the cutting mold 6 can form an annular nitrogen storage groove. The second spring 13 is located at the bottom of the second floating groove 12, and its two ends are respectively connected to the support mold 7 and the bottom wall of the floating groove. In the initial state, the upper surface of the support mold 7 is higher than the cutting mold 6, which is used to support the "metal plate-composite material" composite plate. When the rivet 5 is pressed down, the support mold 7 can first compress the second spring 13 and slide down. After the composite material is punched, the cutting mold 6 then compresses the first spring 11 and slides down.

[0032] Furthermore, the layered floating design of the support mold 7 enables an orderly process of "first punching the composite material, then lowering the cutting mold 6," reducing the possibility of incomplete punching of the composite material due to chaotic movements. In the initial state, the support mold 7 is higher than the cutting mold 6, which helps ensure that the composite plate is accurately positioned in the punching area. After riveting is completed, the second spring 13 can drive the support mold 7 to reset, pushing the composite material waste generated during punching out of the cutting mold 6, achieving "automatic waste removal" without the need for additional manual cleaning, which helps improve production efficiency.

[0033] The top of the support mold 7 is provided with an annular step 14. When the material abuts against the upper surface of the support mold 7, an annular storage area for containing liquid nitrogen is formed at the gap between the material and the annular step 14.

[0034] The support mold 7 is provided with a guide area for liquid nitrogen flow. The support mold 7 is connected to an external conveying unit through an air pipe that penetrates the outer shell of the lower mold 2. The guide area includes an axial air passage 15 opened in the support mold 7. The axial air passage 15 is arranged along the axis of the annular step 14. Horizontal air passages 16 are opened equidistantly in the annular shape in the support mold 7. The air outlet of the horizontal air passage 16 is connected to the protrusion of the annular step 14, and the air inlet of the horizontal air passage 16 is connected to the axial air passage 15.

[0035] Here, the annular nitrogen storage tank is formed by the annular step 14 at the top of the support mold 7, the composite material plate, and the inner wall of the cutting mold 6, and its volume can hold a certain amount of liquid nitrogen. The guiding area includes an axial air passage 15 and a horizontal air passage 16. The axial air passage 15 is opened along the axis of the support mold 7, and its lower end is connected to the external liquid nitrogen system through an air pipe (the air pipe is made of low-temperature resistant stainless steel, and a sealing structure is set at the point where it penetrates the lower mold shell to reduce liquid nitrogen leakage). The horizontal air passage 16 is opened equidistantly in the annular space inside the support mold 7, with one end connected to the axial air passage 15 and the other end connected to the annular nitrogen storage tank. The liquid nitrogen system adopts pulsed nitrogen supply (single nitrogen supply time is 2-3 seconds, with an interval of 1 second, for a total of 3 times), which can rapidly cool the composite material in the annular nitrogen storage tank.

[0036] Furthermore, pulsed nitrogen supply can achieve rapid cooling of composite materials (temperature can be reduced to below -50℃), significantly improving the brittleness of composite materials and helping them to fracture brittlely along the cutting edge of the die 6 during punching, greatly reducing defects such as fiber breakage, delamination, and degumming; the combination of axial air passage 15 and horizontal air passage 16 can make liquid nitrogen more evenly distributed in the annular nitrogen storage tank, reducing cooling dead zones, helping to ensure the uniform brittleness of the composite material punching area, further reducing the defect rate, and providing a guarantee for efficient punching of composite materials. Example

[0037] Component parameter selection Upper mold 1 and pressure ring 3: Upper mold 1 is made of Cr12MoV, pressure ring 3 has an inner diameter of 30mm and an outer diameter of 40mm, and the clamping force is set to 8kN.

[0038] Stamping die 4 and heating element: The outer diameter of stamping die 4 is 29.9mm, and the heater 9 is a 400W electric heating wire with a temperature control accuracy of ±5℃ and an operating temperature of 150℃ (suitable for aluminum alloy plates).

[0039] Rivet 5: Material: 6061-T6 aluminum alloy; Flange 51: Diameter 12mm, Thickness 2mm; Necked Area 52: Diameter 6mm, Length 8mm; Riveted Area 53: Tip Hardness HV320.

[0040] Lower mold 2 and cutting mold 6: The outer shell of the lower mold is made of Cr12MoV, the first floating groove 10 has a diameter of 40mm and a depth of 35mm; the inner diameter of the cutting mold 6 is 6.3mm, the cutting edge angle is 45°, and the stiffness of the first spring 11 is 50N / mm.

[0041] Support mold 7 and second spring 13: Support mold 7 has a diameter of 6.2mm, annular step 14 has a height of 2.5mm and a width of 1.8mm; second floating groove 12 has a diameter of 6.3mm and a depth of 25mm, and second spring 13 has a stiffness of 20N / mm.

[0042] Liquid nitrogen system: 4mm diameter air tube, 4.5mm diameter axial airway 15, 2.5mm diameter horizontal airway 16 (4 in total); pulse nitrogen supply every 2 seconds, with a 1-second interval, for a total of 3 pulses; liquid nitrogen temperature -196℃.

[0043] Composite panel specifications: Composite panel: upper layer 2mm thick 5052 aluminum alloy plate, lower layer 3mm thick carbon fiber reinforced epoxy resin matrix composite panel.

[0044] Working principle and usage process of this utility model: A: Placing the composite plate: Align the upper metal plate (such as a 2mm thick aluminum alloy plate) with the lower composite material plate (such as a 3mm thick carbon fiber reinforced composite material plate) and place it on top of the support mold 7, so that the composite material plate covers the annular nitrogen storage tank area as much as possible.

[0045] B: Edge clamping and positioning: Drive the upper die edge clamping ring 3 to press down and clamp the combined plate; as the pressure increases, the second spring 13 is compressed, and the support die 7 slides down until the upper end face of the support die 7 is flush with the upper end face of the cutting die 6, so that the combined plate is stably fixed.

[0046] CD: Pulsed nitrogen cooling: The external liquid nitrogen system is turned on, and liquid nitrogen enters the annular nitrogen storage tank through the gas pipe, axial gas channel 15, and horizontal gas channel 16. The composite material is cooled by a pulsed nitrogen supply method, which significantly improves its brittleness.

[0047] E: Heating and punching: Start heater 9 to heat rivet 5 and upper metal plate; drive punching die 4 to press down rivet 5, rivet 5 punching area 53 pierces composite material plate, and completes punching with cutting edge of cutting die 6; during punching process, support die 7 continues to compress second spring 13 and slides down to the bottom, composite material waste is embedded in cutting die 6.

[0048] F: Metal flange and interlock: Continue to apply pressure, the first spring 11 is compressed, the cutting die 6 slides down, and a gap is formed between it and the composite material plate; the upper metal plate expands the flange along the gap under heating state, wrapping the opening area of ​​the composite material, while the metal plate is embedded in the necking area 52 of the rivet 5, and the flange 51 of the rivet 5 is completely attached to the metal plate.

[0049] G: Unloading and waste removal: Unloading the upper mold pressure, the first spring 11 and the second spring 13 are reset, driving the cutting mold 6 and the support mold 7 to move upward. The support mold 7 pushes out the composite material waste, completing the riveting.

[0050] The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​this utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made to this utility model without departing from the principle of this utility model, and these improvements and modifications also fall within the protection scope of the claims of this utility model.

Claims

1. A rivet and device for self-piercing riveting of metal and composite materials, comprising an upper die (1) for punching and a lower die (2) for cutting, characterized in that: Also includes: A pressing ring (3) for pressing the plate is fixedly installed on the upper mold (1). A punching die (4) for punching is coaxially slidable inside the pressing ring (3). A rivet (5) is fixedly installed at the end of the punching die (4). A heating element for heating is detachably installed inside the punching die (4). A cutting mold (6) is floating inside the lower mold (2). A support mold (7) for supporting the material is floating inside the cutting mold (6). A guide area for liquid nitrogen flow is provided inside the support mold (7). The support mold (7) is connected to an external conveying unit through an air pipe that penetrates the outer shell of the lower mold.

2. The rivet and device for self-piercing riveting of metals and composite materials according to claim 1, characterized in that: The rivet (5) is a solid flange structure, and the rivet (5) is provided with a flange (51), a necking area (52) and a riveting area (53) in sequence along its axis.

3. The rivet and device for self-piercing riveting of metals and composite materials according to claim 1, characterized in that: The heating element includes a placement groove (8) opened on the stamping die (4), and a heater (9) electrically connected to an external power supply unit is fixedly installed in the placement groove (8). When the heater (9) is working, heat is transferred to the rivet (5) and a heating zone is formed.

4. The rivet and device for self-piercing riveting of metals and composite materials according to claim 1, characterized in that: The lower mold (2) has a first floating groove (10) inside. The cutting mold (6) is slidably connected in the first floating groove (10). The first floating groove (10) is provided with a first spring (11). The two ends of the first spring (11) are respectively connected to the cutting mold (6) and the bottom wall of the first floating groove (10).

5. The rivet and device for self-piercing riveting of metals and composite materials according to claim 4, characterized in that: The upper part of the cutting die (6) is provided with a second floating groove (12), and the support die (7) is slidably connected in the second floating groove (12). A second spring (13) is provided in the second floating groove (12), and the two ends of the second spring (13) are respectively connected to the support die (7) and the bottom wall of the second floating groove (12).

6. The rivet and device for self-piercing riveting of metals and composite materials according to claim 1, characterized in that: The top of the support mold (7) is provided with an annular step (14). When the material abuts against the upper surface of the support mold (7), an annular storage area for containing liquid nitrogen is formed at the gap between the material and the annular step (14).

7. The rivet and device for self-piercing riveting of metals and composite materials according to claim 1, characterized in that: The guiding area includes an axial air passage (15) opened in the support mold (7). The axial air passage (15) is arranged along the axis of the annular step (14). Horizontal air passages (16) are opened equidistantly in the annular shape in the support mold (7). The air outlet of the horizontal air passage (16) is connected to the protrusion of the annular step (14), and the air inlet of the horizontal air passage (16) is connected to the axial air passage (15).

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