Rivet and device for riveting metal to composite material

Abstract

The utility model discloses a metal and composite material riveting is with rivet and device in the technical field of metal and composite material connection, including setting on the work table for the first die and for riveting second die of blanking, still include: the first die is by setting on the upper die punch material die and can detachably set on the lower die cut material die and is formed, fixed mounting on the upper die for the edge ring of pressing plate material, the punch material die coaxial setting in the annular inner chamber of edge ring, and punch material die and the sliding adaptation of annular inner chamber of edge ring. The utility model discloses through the collaborative design of rivet and double sequence die, need not to carry out the prefabricated hole processing to composite material, cut material die cambered surface optimization blanking stress distribution, spring and floating die guarantee the plate material adhesion in blanking process simultaneously with the aid of, effectively reduce the fiber breakage, matrix cracking and delamination etc. Defects when composite material blanking, solved the problem that the prior art " prefabricated hole relies on increasing process " and " blanking defect frequently occurs reduces joint quality " is difficult to take into account.

Description

Technical Field

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

[0002] Carbon fiber reinforced composites have become a core material for automotive lightweighting and aerospace structural weight reduction due to their advantages such as high specific strength, high specific modulus, good fatigue resistance, low coefficient of thermal expansion and good corrosion resistance. They are often paired with metal materials such as aluminum alloys and connected by riveting.

[0003] However, composite materials currently exhibit poor plasticity, making them prone to fiber breakage, matrix cracking, interface delamination, and delamination during traditional riveting processes. This directly leads to decreased joint performance or even failure. Furthermore, traditional riveting requires pre-drilled holes in the composite material before it can be mated with the metal plate, increasing the riveting process and creating difficulties in aligning tooling and holes, further reducing production efficiency and joint consistency. Existing riveting devices are mostly single-function molds (only punching or only riveting), and the dimensional compatibility between rivets and molds lacks clear design. This fails to simultaneously address the three core issues of "pre-drilled hole dependence," "punching defects," and "insufficient joint strength," making it difficult to meet the integrated riveting requirements of metal-composite materials. Therefore, we urgently need rivets and devices for metal-composite material riveting to solve these problems. Utility Model Content

[0004] To address the shortcomings of existing technologies, this utility model provides a rivet and device for riveting metal and composite materials. By using a dual-sequence mold with a shared upper mold, a special rivet structure working together, and optimizing the punching stress with a cutting mold, and ensuring the fit of the sheet metal with a spring and a floating mold, it achieves the elimination of pre-drilled holes in composite materials, reduces punching defects, adapts to sheets of different thicknesses, and improves the efficiency of the riveting process and the static tensile and fatigue performance of the joint.

[0005] The purpose of this utility model is achieved as follows: it includes a first die for punching and a second die for riveting, both mounted on a workbench; the first die consists of a punching die mounted on an upper die and a cutting die detachably mounted on a lower die; a pressure ring fixedly mounted on the upper die for pressing the sheet metal, the punching die being coaxially disposed in the annular cavity of the pressure ring, and the punching die slidingly adapted to the annular cavity of the pressure ring; a rivet for punching material, mounted on the end of the punching die; a cavity formed in the cutting die, the bottom wall of which is slidably connected to a floating die for discharging material, a spring being disposed in the cavity, and the two ends of the spring abutting against the floating die and the inner wall of the cavity, respectively; the second die consists of a support die detachably mounted on the lower die and an upper die identical to that in the first die; and a riveting die fixedly mounted in the support die for riveting.

[0006] Optionally, the rivet consists of a flange, a neck, and a self-punching end. The flange is fixedly installed to the end of the punching die, the neck is located in the middle of the rivet, and the self-punching end is located at the bottom of the rivet.

[0007] Optionally, the angle between the lower part of the flange and the necked sidewall is in the range of 15°-30°.

[0008] Optionally, the diameter ratio between the flange, the self-piercing end, and the neck is 6:4:3.

[0009] Optionally, the end of the self-punching end is provided with a groove, and the end face of the riveting die is provided with a protrusion that matches the groove.

[0010] Optionally, the upper part of the cutting die is provided with an arc surface for reducing punching stress.

[0011] Compared with the prior art, the beneficial effects of this utility model are as follows: 1. This utility model, through the collaborative design of "rivets and dual-sequence molds", eliminates the need for pre-drilled holes in composite materials. At the same time, it optimizes the stress distribution during punching by utilizing the arc surface of the cutting die, and ensures the fit of the sheet material during punching by using springs and floating dies. This effectively reduces defects such as fiber breakage, matrix cracking, and delamination during composite material punching, and solves the problem in the prior art that it is difficult to balance "pre-drilled holes rely on additional processes" with "frequent punching defects reduce joint quality".

[0012] 2. By specifying the diameter ratio of each component of the rivet (flange: self-punching end: necking = 6:4:3) and the size ratio of the cavity to the self-punching end (1.4:1 or 1.8:1), this utility model can flexibly adapt to upper metal plates and lower composite material plates of different thicknesses. It eliminates the need to develop molds separately for a single specification. At the same time, the two-stage molds share the upper mold, which greatly reduces the mold switching and adjustment time. This not only solves the problems of poor compatibility between rivets and molds and narrow application range in the prior art, but also improves the process efficiency of metal-composite material riveting and is more suitable for industrial mass production needs. Attached Figure Description

[0013] 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.

[0014] Figure 1 This is a schematic diagram of the upper mold and punching mold structure provided by this utility model.

[0015] Figure 2This is a schematic diagram of the lower mold and support mold structure provided by this utility model.

[0016] Figure 3 This is a schematic diagram of the half-section structure of the cutting die and punching die provided by this utility model.

[0017] Figure 4 This is a schematic diagram of the half-section structure of the punching die and support die provided by this utility model.

[0018] Figure 5 This is a schematic diagram of the rivet structure provided by this utility model.

[0019] Figure 6 This is a partially enlarged structural schematic diagram provided by this utility model.

[0020] Figure 7 This is a schematic diagram of the riveting effect provided by this utility model.

[0021] Figure 8 This is a schematic diagram of the punching and riveting process structure provided by this utility model.

[0022] In the diagram: 1. Stamping die; 11. Blank holder ring; 12. Rivet; 121. Flange; 122. Necking; 123. Self-punching end; 124. Groove; 2. Cutting die; 21. Cavity; 22. Floating die; 23. Spring; 3. Support mold; 31. Riveting mold; 4. Protrusion; 5. Curved surface. Detailed Implementation

[0023] 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.

[0024] like Figure 1-8 As shown in the figure, the present invention provides a rivet 12 and device for riveting metal and composite materials, including a first die for punching and a second die for riveting, which are set on a workbench.

[0025] It also includes a first mold consisting of a punching die 1 mounted on an upper mold and a cutting die 2 detachably mounted on a lower mold.

[0026] The second mold consists of a support mold 3 that can be detachably mounted on the lower mold and an upper mold identical to that in the first mold.

[0027] Here, the first die is responsible for punching: the pressure ring 11 first presses down to clamp the upper metal plate and the lower composite material plate, reducing the displacement of the plate during punching; the punching die 1 drives the rivet 12 to punch downward, so that the composite material is punched along the cavity 21 of the cutting die 2, the floating die 22 moves down synchronously with the punching process, and the spring 23 is compressed; after the punching is completed, the spring 23 returns to its original position and pushes the floating die 22 up, pushing the composite material waste out of the cavity 21, which helps to achieve automatic unloading. The second die is responsible for riveting: there is no need to replace the upper die (punching die 1 and pressure ring 11), only the cutting die 2 of the lower die needs to be replaced with the support die 3, and the riveting die 31 presses the metal plate upward, so that the metal plate deforms and flows towards the punching edge of the composite material, forming a mechanical interlock.

[0028] Furthermore, the design of a shared upper mold and a detachable lower mold eliminates the need for repeated adjustments to the upper mold positioning, which helps reduce mold switching time and improve process efficiency. At the same time, the sliding fit between the pressure ring 11 and the punching die 1 helps to transmit pressure coaxially during punching and riveting, reducing uneven deformation of the metal sheet or cracking of composite materials caused by force offset.

[0029] A pressure ring 11 is fixedly installed on the upper mold for pressing the sheet metal. A punching die 1 is coaxially arranged in the annular inner cavity of the pressure ring 11, and the punching die 1 and the annular inner cavity of the pressure ring 11 are slidably adapted.

[0030] A rivet 12 for punching is provided on the end of the punching die 1. The rivet 12 is composed of a flange 121, a neck 122 and a self-punching end 123. The flange 121 is fixedly installed on the end of the punching die 1. The neck 122 is located in the middle of the rivet 12 and the self-punching end 123 is located at the bottom of the rivet 12.

[0031] Here, the flange 121 is disc-shaped with an area larger than the end contact surface of the stamping die 1, which helps to evenly transmit the downward pressing force of the stamping die 1 to the entire rivet 12 and reduce the risk of local stress concentration; the neck 122 is a cylindrical section with a diameter smaller than that of the flange 121 and the self-punching end 123, which is used to reserve space for the deformation of the metal plate during the second-order riveting; the self-punching end 123 is the punched section at the bottom of the rivet 12, and the end face is designed to be concave to fit the protrusion 4 of the riveting die 31, which helps to ensure that the riveting force is evenly transmitted.

[0032] Furthermore, the force transmission design of flange 121 can reduce the risk of breakage caused by excessive local stress on rivet 12 during punching; the size design of neck 122 provides sufficient space for metal plate deformation, which helps the metal plate to better wrap the punched edge of composite material during secondary riveting; the concave structure of self-punching end 123 provides a reference for the positioning of riveting die 31, which helps to improve riveting accuracy.

[0033] The angle between the lower part of flange 121 and the side wall of neck 122 ranges from 15° to 30°.

[0034] Here, when rivet 12 is pressed down, the lower part of flange 121 contacts the surface of the metal plate. If the included angle is too small (<15°), the edge of flange 121 may embed into the metal plate, potentially causing scratches. If the included angle is too large (>30°), the contact area decreases, easily leading to localized stress concentration and indentation in the metal plate. Choosing a 20° included angle ensures both the contact area between flange 121 and the metal plate and reduces edge scratches or stress concentration.

[0035] Furthermore, a head tilt angle of 15°-30° can reduce stress concentration at the contact point between the rivet 12 and the metal plate, reducing the risk of scratches, dents, and other defects in the metal plate during the punching process. At the same time, it helps to improve the fit between the rivet 12 and the metal plate, laying the foundation for the force transmission of subsequent riveting.

[0036] The diameter ratio between flange 121, self-piercing end 123 and neck 122 is 6:4:3.

[0037] Here, taking a base size of 1mm as an example, the flange 121 has a diameter of 6mm, providing a stable force transmission base; the self-punching end 123 has a diameter of 4mm, which matches the aperture of the cutting die 2 cavity 21, ensuring that the composite material is accurately cut during punching; the necking end 122 has a diameter of 3mm, reserving sufficient space for the deformation of the metal sheet. If the ratio deviates from 6:4:3, if the diameter of the necking end 122 is too large (>3mm), the deformation space of the metal sheet will be insufficient, making it difficult to wrap the composite material; if the diameter of the self-punching end 123 is too small (<4mm), the punching efficiency will be reduced, easily leading to tearing of the composite material.

[0038] Furthermore, the 6:4:3 diameter ratio ensures that the dimensions of all components of the rivet 12 are coordinated, eliminating the need for separate design for a single specification. By adjusting the base dimensions (e.g., when the base dimension is 1.5mm, the flange is 9mm, the self-punching end is 6mm, and the necking is 4.5mm), it can be adapted to metal plates of different thicknesses (2-5mm), which helps to reduce mold development costs. At the same time, this ratio takes into account both the strength of the rivet 12 itself and the deformation requirements of the metal plate, reducing the possibility of rivet 12 breaking or insufficient deformation of the metal plate during riveting.

[0039] The end of the punch 123 has a groove 124 and is fixedly installed in the support mold 3 for riveting. The end face of the riveting mold 31 is provided with a protrusion 4 that matches the groove 124.

[0040] Here, during the second-order riveting, the support mold 3 drives the riveting mold 31 to move upward, and the protrusion 4 is embedded in the groove 124. This allows the riveting force to be transmitted to the rivet 12 through the surface contact between the protrusion 4 and the groove 124, and then from the rivet 12 to the metal plate, reducing local stress concentration caused by point contact. If the groove 124 and the protrusion 4 do not match, such as if the diameter of the protrusion 4 is smaller than that of the groove 124, it may cause the riveting force to shift and the metal plate to deform unevenly; if the diameter of the protrusion 4 is larger than that of the groove 124, it may cause the rivet 12 to crack.

[0041] Furthermore, the matching structure of "groove 124 - protrusion 4" helps to ensure that the riveting force is evenly transmitted along the axis, reducing the situation where the metal plate is excessively deformed or not deformed locally due to uneven force. At the same time, it helps to ensure the consistency of deformation of the metal plate towards the punched edge of the composite material and improve the interlocking stability of the joint.

[0042] A cavity 21 is formed inside the cutting die 2. A floating die 22 for discharging material is slidably connected to the bottom wall of the cavity 21. A spring 23 is provided inside the cavity 21, and the two ends of the spring 23 abut against the floating die 22 and the inner wall of the cavity 21, respectively.

[0043] The upper part of the cutting die 2 is provided with an arc surface 5 for reducing punching stress, and the radius of the arc surface 5 is in the range of 5mm to 10mm.

[0044] Here, the stress in the conventional planar cutting die 2 is concentrated at the edge of the punching hole, which can easily lead to fiber breakage in the composite material. However, the 8mm radius arc surface 5 causes the punching stress to gradually decrease from the center of the cutting hole to the outer edge, reducing the area of ​​significant stress concentration. If the radius of the arc surface 5 is <5mm, the stress gradient change is too steep, and local concentration may still exist; if the radius is >10mm, the transition of the arc surface 5 is gentle, and the punching force may be insufficient, which can easily lead to incomplete punching of the composite material.

[0045] Furthermore, the 5mm to 10mm arc surface 5 can optimize the distribution of punching stress, reduce the risk of defects such as fiber breakage, matrix cracking or delamination during composite material punching, and at the same time help improve the flatness of the punching surface and reduce burr interference during subsequent riveting.

[0046] The ratio of the diameter of the opening at the top of the cavity 21 to the diameter of the self-punching end 123 is 1.4:1 or 1.8:1.

[0047] Here, the top of cavity 21 is used for cutting material. Its hole diameter is approximately equal to the diameter of the self-punching end 123 of rivet 12 plus 2 × the thickness of the upper metal plate. If the diameter of the self-punching end 123 is 4mm (corresponding to a ratio of 6:4:3), when the ratio is 1.4:1, the top hole diameter of cavity 21 is 4mm × 1.4 = 5.6mm. Substituting into the formula, we can get "the thickness of the upper metal plate is approximately (5.6mm - 4mm) / 2 = 0.8mm", which is suitable for thin metal plates (1-2mm).

[0048] When the ratio is 1.8:1, the top aperture of cavity 21 is 4mm × 1.8 = 7.2mm. Substituting into the formula, we can get "the thickness of the upper metal plate is approximately (7.2mm - 4mm) / 2 = 1.6mm", which is suitable for thick metal plates (2-4mm).

[0049] Furthermore, as the rivet 12 is pressed down and bends, it is less likely to be cut off by the aperture of the cavity 21; while the composite material is brittle and will be punched more precisely along the aperture of the cavity 21. If the ratio is <1.4:1, the aperture of the cavity 21 is too small, and the risk of the metal plate being cut off increases; if the ratio is >1.8:1, the aperture of the cavity 21 is too large, and the punching burr of the composite material may be too wide, affecting the riveting fit.

[0050] Furthermore, the ratio of 1.4:1 or 1.8:1, combined with the formula "cutting die 2 hole diameter ≈ rivet 12 self-punching end 123 diameter and 2 × upper metal plate thickness", can more accurately adapt to upper metal plates of different thicknesses. This helps to ensure that "the metal plate is not easily broken and the composite material can be cut well" during the punching process, while reserving appropriate space for subsequent riveting deformation of the metal plate and improving the integrity of the joint.

[0051] Working principle and usage process of this utility model: Materials to be riveted: The upper metal plate is a 0.8mm thick aluminum alloy plate, and the lower composite material plate is a 5mm thick carbon fiber reinforced composite material plate (T700 grade). Rivet 12 parameters: base size is 1mm, flange 121 diameter = 6mm, self-punching end 123 diameter = 4mm, necking end 122 diameter = 3mm (meets 6:4:3 ratio), head down tilt angle = 20°, self-punching end 123 groove 124 diameter = 4mm; Mold parameters: Cutting mold 2, arc surface 5, radius = 8mm; cavity 21, top hole diameter = 5.6mm (according to a 1.4:1 ratio, suitable for 0.8mm metal plate, conforming to the formula "5.6mm≈4mm+2×0.8mm"); riveting mold 31, protrusion 4, diameter = 4mm; support mold 3, height is the same as cutting mold 2.

[0052] First-order blanking (first die operation) A: Material placement: The upper aluminum alloy plate and the lower carbon fiber composite plate are stacked on the arc surface 5 of the cutting die 2 in sequence. The floating die 22 is pushed to the top of the cutting die 2 under the pre-compression of the spring 23, and is flush with the lower end surface of the composite material. B: Pressing and fixing: The upper mold moves down, and the pressure ring 11 first contacts the aluminum alloy plate, pressing the two layers of plates with 8MPa pressure to ensure no gaps and no displacement; C: Blanking and cutting: The blanking die 1 drives the rivet 12 to press downwards at a speed of 15mm / s, squeezing the aluminum alloy plate from the blanking end 123 (diameter 4mm) to bend and deform it (without cutting it off), and simultaneously pressing down on the composite material; the composite material is blanked along the 5.6mm diameter hole at the top of the cavity 21, and the floating die 22 moves down 7mm (total thickness of the plate) with the blanking, and the spring 23 is further compressed; D: Unloading and stripping: The punching die 1 and the pressure ring 11 move upward to unload, the spring 23 resets and pushes the floating die 22 upward to push the composite material waste (5.6mm in diameter) out of the cavity 21, completing the punching.

[0053] E: Second-order riveting (second mold operation) Mold switching: Remove the cutting mold 2 from the mold, install the support mold 3, and ensure that the protrusion 4 (4mm in diameter) of the riveting mold 31 is aligned with the groove 124 of the rivet 12; Maintain clamping: The pressure ring 11 moves down again to press the two layers of board with a pressure of 8MPa to maintain the clamping force; Riveting Forming: The support mold 3 drives the riveting mold 31 to move upward at a speed of 10mm / s. The protrusion 4 is embedded in the groove 124, and the aluminum alloy plate is extruded and deformed towards the blanking edge of the composite material. The aluminum alloy plate unfolds along the necking 122 (diameter 3mm), which better wraps the blanking edge of the composite material and forms a mechanical interlock. Processing completed: Riveting die 31 and pressure ring 11 are reset, and the riveted finished product is taken out. At this time, the slight burrs of the composite material punching hole are covered by the aluminum alloy plate, and the joint has no obvious defects.

[0054] 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 riveting metal and composite materials, characterized in that: It includes a first die for punching and a second die for riveting, both mounted on the worktable, and also includes: The first mold consists of a punching die (1) mounted on the upper mold and a cutting die (2) detachably mounted on the lower mold; A pressing ring (11) is fixedly installed on the upper mold for pressing the sheet metal. The punching die (1) is coaxially arranged in the annular cavity of the pressing ring (11), and the punching die (1) and the annular cavity of the pressing ring (11) are slidably adapted. A rivet (12) for punching is provided on the end of the punching die (1). A cavity (21) is formed in the cutting mold (2). A floating mold (22) for discharging material is slidably connected to the bottom wall of the cavity (21). A spring (23) is provided in the cavity (21), and the two ends of the spring (23) abut against the floating mold (22) and the inner wall of the cavity (21) respectively. The second mold consists of a support mold (3) that is detachably mounted on the lower mold and an upper mold identical to that in the first mold; A riveting mold (31) is fixedly installed inside the support mold (3) for riveting.

2. The rivet and device for riveting metal and composite materials according to claim 1, characterized in that: The rivet (12) consists of a flange (121), a neck (122) and a self-punching end (123). The flange (121) is fixedly installed at the end of the punching die (1). The neck (122) is located in the middle of the rivet (12), and the self-punching end (123) is located at the bottom of the rivet (12).

3. The rivet and device for riveting metal and composite materials according to claim 2, characterized in that: The angle between the lower part of the flange (121) and the side wall of the neck (122) is in the range of 15°-30°.

4. The rivet and device for riveting metal and composite materials according to claim 3, characterized in that: The diameter ratio between the flange (121), the self-piercing end (123), and the neck (122) is 6:4:

3.

5. The rivet and device for riveting metal and composite materials according to claim 3, characterized in that: The end of the self-punching end (123) is provided with a groove (124), and the end face of the riveting die (31) is provided with a protrusion (4) that matches the groove (124).

6. The rivet and device for riveting metal and composite materials according to claim 1, characterized in that: The upper part of the cutting die (2) is provided with an arc surface (5) for reducing punching stress.

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