Laser assisted clinch apparatus and method for resin based composites and metal materials

Abstract

A laser-assisted rivet-free riveting device for resin-based composite material and metal material, comprising: oppositely arranged concave die mechanism with laser generator and convex die mechanism below the plate, the concave die mechanism comprising: a box body and sequentially arranged inside the box body: a core block, a concave die counter top, a concave die outer cylinder and a laser generator, wherein: the concave die outer cylinder is sleeved with the concave die counter top, the laser generator is sequentially passed through the core block and the concave die counter top and eccentrically arranged in the convex die mechanism, the annular cutting is realized by laser rotary cutting, and the composite material and the metal material are sequentially arranged between the concave die counter top and the convex die mechanism. The application utilizes the difference in the absorption capacity of resin-based composite material and metal material for specific laser waveband laser energy, realizes the continuous process of plastic deformation of laser cutting composite material and metal material, the composite material cutting section quality is high, the residual heat generated by laser cutting can heat soften the connected metal material, and the plastic deformation ability of the metal material is improved to a certain extent.

Description

Technical Field

[0001] This invention relates to a technology in the field of joining dissimilar plates, specifically a laser-assisted rivetless riveting device and method for joining resin-based composite materials and metal materials. Background Technology

[0002] Thin-plate joining of resin-based composite materials and metallic materials is widely used in the automotive, rail transportation, and aerospace industries. However, due to differences in electrical resistance, melting point, and thermal conductivity between dissimilar materials, a homogeneous weld nugget cannot be formed during welding, thus hindering effective and safe connections. Currently, mechanical joining methods are predominantly used for joining dissimilar materials. Rivetless joining, with its advantages of no fasteners, no workpiece surface damage, and excellent fatigue resistance and sealing properties, has become the most economical mechanical joining process. However, the application of traditional rivetless joining is limited by the insufficient plastic deformation capacity of resin-based carbon fiber composites.

[0003] Existing laser-assisted interlocking connection technology for resin-based thermoplastic composites and lightweight alloys involves processing corresponding feature patterns on one side of the connecting plates, assembling the two, and then using a oscillating laser to scan the surface of the lightweight alloy plate. Under pressure, a riveting structure of extremely high strength is formed between the resin-based thermoplastic composite and the lightweight alloy. However, the preparation cost of the feature patterns on the plate surface is high, making it unsuitable for mass commercial production. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by proposing a laser-assisted rivetless riveting device for resin-based composite materials and metal materials. Utilizing the difference in absorption capacity of resin-based composite materials and metal materials for specific laser wavelengths, it achieves a continuous process of plastic deformation during laser cutting of both materials, thus enabling rivetless riveting without pre-drilled holes. This avoids the complex process of positioning riveting die holes in processes with pre-drilled holes. The laser cutting process designed in this invention is suitable for composite materials with both thermoplastic and thermosetting matrices, solving the problem that thermosetting resin-based composite materials cannot be thermally softened to improve riveting performance. The composite material has a high-quality cut surface, and the residual heat generated by laser cutting can thermally soften the connected metal material, improving its plastic deformation capacity to a certain extent. This invention significantly reduces the complexity of rivetless riveting processes between resin-based composite materials and metal materials, broadening the application range of rivetless riveting.

[0005] This invention is achieved through the following technical solution:

[0006] This invention relates to a laser-assisted rivetless riveting device for resin-based composite materials and metal materials, comprising: a concave mold mechanism with a laser generator arranged opposite to each other and a convex mold mechanism located below the sheet metal. The concave mold mechanism includes: a housing and a core block, a concave mold top, a concave mold outer cylinder, and a laser generator arranged sequentially inside the housing, wherein: the concave mold outer cylinder is sleeved with the concave mold top, the laser generator passes through the core block and the concave mold top in sequence and faces the convex mold mechanism, and the composite material and the metal material are arranged sequentially between the concave mold top and the convex mold mechanism.

[0007] The outer die cylinder includes: an outer die cylinder base and an outer die cylinder extension block connected thereto, wherein: the outer die cylinder base and the die backing are fitted together with clearance and are sleeved on the die backing through axial bearings and radial bearings, and the outer die cylinder extension block is located at the lowest end of the die mechanism and is in contact with the plate.

[0008] The aforementioned die reversal mechanism includes a laser channel and a rotating mechanism, wherein the laser channel is an eccentric through hole, and the rotating mechanism can ensure that the die reversal mechanism can rotate independently when the outer cylinder of the die is locked.

[0009] This invention relates to a laser-assisted rivetless riveting method for composite materials and metal materials based on the above-mentioned device. First, the composite material is stacked on the metal material and placed on the pressure ring. After the connecting plate is pre-tightened by pressing down the die, the laser generator located in the back of the die emits a laser beam and rotates to cut holes in the composite material. Under the forming force of the upward movement of the punch, the metal material is plastically deformed and rivetless riveting is formed in the cut hole of the composite material.

[0010] The laser beam has a spot width of less than or equal to 0.3 mm, a laser source power of P = at⁴ - b, where a = 120 W / mm and b = 60 W, and the rotational scanning speed is... , n = 40mm / s, where: t4 is the diameter of the cut hole, and t4 is the thickness of the composite material.

[0011] During the hole-cutting process, the maximum temperature T of the composite material satisfies: et4 + 140 ℃ < T < et4 + 190℃, e = 30℃ / mm. If the maximum temperature exceeds the range, the hole-cutting is unqualified and the process ends.

[0012] Technical effect

[0013] This invention integrates a laser generator inside the die end of a concave mold. It utilizes a point-like laser beam to perform rotational scanning and hole cutting on composite materials stacked with metal. After the outer cylinder of the concave mold presses down on the pre-tightened connecting plate, a laser protective chamber is formed, thus enabling rivetless joining of resin-based composite materials and metal materials without pre-drilled holes. Compared to heat-softening assisted riveting, this reduces process time by 70%-85%. The point-like laser circular scanning allows for cutting of the composite material without damaging the metal surface. The residual heat generated from laser circumferential cutting of the composite material can, to some extent, improve the plastic deformation capacity of the metal material, enhancing the connection quality. Attached Figure Description

[0014] Figure 1 A cross-sectional schematic diagram of an integrated laser-assisted rivetless upper mold;

[0015] Figure 2 A schematic diagram of the laser-assisted rivetless joining process.

[0016] Figure 3 This is a schematic diagram showing the dimensions of a rivetless joint mold and laser cutting.

[0017] Figure 4 A schematic diagram of a laser-assisted rivetless connector (the bottom of the metal material is higher than the bottom surface of the composite material);

[0018] Figure 5 A schematic diagram of a laser-assisted rivetless connector (the bottom of the metal material is aligned with the bottom surface of the composite material);

[0019] Figure 6 A schematic diagram of a laser-assisted rivetless connector (the bottom of the metal material is lower than the bottom surface of the composite material);

[0020] In the figure: 1. Outer cylinder of the die cavity, 11. Extension block of the outer cylinder of the die cavity, 12. Base of the outer cylinder of the die cavity, 121. Axial bearing, 122. Radial bearing, 2. Die cavity counter-top, 21. Lower cover plate, 211. Die cavity core block, 212. Die cavity box, 3. Laser generator, 31. Upper cover plate, 2121. Box flange, 4. Composite material, 5. Metal material, 6. Punch, 7. Pressure ring, 8. Thermistor, 9. Laser beam, 10. Composite waste, 51. Connecting head and neck, 52. Interlock value, 53. Bottom of metal material, 41. Through hole of composite material, 42. Bottom surface of composite material;

[0021] Figure 7 Image of a laser-cut sample of a composite material;

[0022] Figure 8 The results of temperature acquisition on the surface of metal materials during laser cutting are shown in the following: a) Schematic diagram of temperature change in the overlapping area of ​​the metal material; b) Temperature cloud map acquired by thermal imager at t = 5s.

[0023] Figure 9 This is a cross-sectional view of the joint between rivetless metal materials and composite materials. Detailed Implementation

[0024] like Figure 1 As shown, this embodiment relates to an integrated laser-assisted rivetless riveting device, including: a concave mold mechanism with a laser generator 3 arranged opposite to each other and a convex mold mechanism located below the sheet metal. The concave mold mechanism includes: a housing 212 and a core block 211, a concave mold top 2, a concave mold outer cylinder 1 and the laser generator 3 arranged sequentially inside it, wherein: the concave mold outer cylinder 1 is sleeved with the concave mold top, the laser generator passes through the core block 211 and the concave mold top 2 in sequence and faces the convex mold mechanism, and the composite material 4 and the metal material 5 are arranged sequentially between the concave mold top 2 and the convex mold mechanism.

[0025] The composite material 4 is a carbon fiber or glass fiber composite material with thermoplastic or thermosetting resin as the matrix, and its thickness t4 = 0.5 - 5.0 mm; no surface pretreatment is required on the connecting plates before connection.

[0026] The metal material 5 is a metal that is easily deformable and has a thickness t5 = 0.5 - 5.0 mm.

[0027] The outer cylinder of the die includes: a die outer cylinder base 12 and a die outer cylinder extension block 11 connected thereto, wherein: the die outer cylinder base 12 and the die backing 2 are fitted together with clearance and are sleeved on the die backing through an axial bearing 121 and a radial bearing 122, and the die outer cylinder extension block 11 is located at the lowest end of the die mechanism and is in contact with the plate.

[0028] The axial bearing 121 is fixedly connected to the die backing 2 via the lower cover plate 21.

[0029] The laser generator 3 is eccentrically positioned within the concave mold core block 211 and connected to the housing 212 via the upper cover plate 31.

[0030] The upper end of the die housing 212 is connected to the rotary power unit via flange 2121. The rotary power unit drives the die back ejector 2 and the laser generator 3 to achieve a rotational speed of 10-50 mm / s to realize rotational scanning. The scanning speed v satisfies the following relationship: ,in For the diameter of the hole, The recommended scanning speed is 10 mm / s. If the thickness of the composite material is greater than 2 mm, the scanning speed can be appropriately reduced.

[0031] The distance between the concave mold ejector 2 and the composite material 4 is d = t4 ± k, where t4 is the thickness of the composite material 4 and k is the interlocking value, which is 0.4 mm in this embodiment.

[0032] The laser generator 3 is a CO2 laser generator with an output power P = 120W / mm·t4 - 60W. For example, the recommended power for a composite material with a thickness t4 = 2mm is 180W. A reasonable laser cutting process must meet the following conditions: 30℃ / mm·t4 + 140℃ < T < 30℃ / mm·t4 + 190℃, where T is the real-time temperature measured by a thermistor.

[0033] The punch mechanism includes a pressure ring 7 and a punch 6 disposed therein, wherein the punch 6 and the pressure ring 7 are in clearance fit, and the maximum clearance does not exceed 0.14mm.

[0034] The diameter of the punch 6 The punch angle β is 2° to 10°.

[0035] The pressure ring 7 integrates a thermistor 8 to detect the surface temperature T of the metal material 5 and to define the process window for laser cutting of the composite material.

[0036] like Figure 2 As shown, this embodiment relates to a laser-assisted rivetless riveting method based on the aforementioned device. The method involves placing the composite material and metal material in a rational sequence at the riveting station; pre-tightening the connecting plates with the pressure ring and the outer cylinder of the die; achieving hole cutting in the composite material through the rotation of the laser generator integrated within the die's anti-reverse ejector; under the action of the forming force of the punch, the punch 6 moves towards the connecting plate and applies forming force, causing the metal material 5 to undergo plastic deformation towards the die under the pressure of the punch 6, while the composite scrap 10 is ejected by the deformed metal material; the height of the ejected composite scrap 10 is limited by the position of the die's anti-reverse ejector 2; after the composite scrap 10 contacts the die's anti-reverse ejector 2, both provide support for the metal material 5; under the combined action of the forming force and the support force, the metal material 5 is thinned at the bottom to 20%t5 - 50%t5.

[0037] The thinning of the metal material 5 results in a certain amount of radial material flow: when the thickness of the composite material 4 is close to the thickness of the metal material 5, the bottom of the plastically deformed metal material 5 may be as follows: Figure 6 As shown, below the bottom surface of composite material 4 or as Figure 5 As shown, the metal material 5, after plastic deformation, forms a tight fit with the bottom surface of the composite material 4, flush with it. When the thickness of the metal material 5 is much greater than the thickness of the composite material 4, the plastically deformed metal material 5 may be flush with or higher than the bottom surface of the composite material 4, such as... Figure 4 As shown, the metal material 5, which is higher than the bottom surface of the composite material 4, can undergo greater radial deformation due to the forming force, thereby forming a greater mechanical engagement.

[0038] During laser cutting, laser generator 3 emits laser beam 9, which remains perpendicular to the surface of composite material 4 throughout the scanning process. The beam diameter is less than or equal to 0.3 mm, thereby locally vaporizing the composite material to achieve the cutting process. The angle α between the resulting cut surface and the surface of the composite material satisfies: 120° > α > 60°.

[0039] In order to reduce the heat-affected zone of the composite material during laser cutting, the laser generator 3 should reduce the number of scan passes during the cutting of the composite material 4.

[0040] The material placement order during connection meets the following requirements: composite material 4 faces the concave mold, and metal material 5 faces the convex mold; after the connection process begins, the pressure ring 7 pre-tightens and fixes the connecting plates. Its function is to ensure that composite material 4 and metal material 5 form a tight fit during the connection process. The pre-tightening pressure can be set as q·(t4+t5) based on the total thickness of the connecting materials, where q = 0.125mm / MPa.

[0041] Depending on the properties of the connecting metal materials, especially high-strength aluminum alloys, the scanning speed and laser energy can be appropriately reduced. While ensuring cutting performance, the residual heat from cutting can be fully utilized to soften the aluminum alloy material and improve the plastic deformation capacity of the connecting material.

[0042] Through specific practical experiments, thermoplastic carbon fiber composite plate CF-PA66 with a thickness of t4 = 2mm and five-series aluminum alloy rolled plate AA5182 with a thickness of t5 = 2mm were used. At the riveting station, the outer cylinder of the die 1 and the die ejector 2 were on top, the punch 6 and the pressure ring 7 were on the bottom, the metal material 5 was placed on the punch end, and the composite material 4 was placed on the die end with the die ejector depth d preset to 2.1mm. First, the outer cylinder of the die 1 and the die ejector 2 were set to press down rapidly and synchronously at 50mm / s. When approaching the connecting material, the speed was reduced to 20mm / s and pressed down slowly and synchronously until the composite material 4 was completely adhered to the surface. The outer cylinder of the die was subjected to a pre-tightening pressure of 2MPa. The laser generator 3 was set to a power of 300W (60%) and a frequency of 9 kHz. The rotation speed of the die ejector 2 was 10mm / s. The laser beam 9 was always perpendicular to the surface of the composite material and rotated one revolution. As the composite material 4 was vaporized by the laser beam 9, the temperature of the corresponding overlapping area of ​​the metal material rose rapidly. Figure 8 As shown, the maximum temperature of 244.2℃ was reached within 0.4s. The laser cutting lasted 3.2s, during which the temperature of the corresponding overlapping areas of the metal material remained above 200℃. Figure 7As shown, laser cutting creates regular holes in the carbon fiber composite board, with a hole diameter of 5mm. The forming force is determined by the temperature measured by the thermistor 8 within the pressure ring 7. When the measured temperature drops by 5%, the 3mm diameter punch 6 feeds upwards at a speed of 30mm / s to apply forming force. Under the combined compression of the punch 6 and the composite scrap 10, the bottom 13 of the metal material is thinned to 20% of the original thickness. This thinning of the metal material results in a certain amount of radial material flow, thus forming a tight fit at the rivet joint. The connector slice is shown below. Figure 9 As shown.

[0043] This invention utilizes the difference in absorption capacity between resin-based composite materials and metal materials for specific laser wavelengths to achieve laser cutting of composite materials without damaging the metal materials. Through continuous plastic deformation of the metal materials, rivetless riveting of the composite materials and metal materials is achieved without pre-drilled holes. The laser generator 3 is built into the cavity mold ejector 2, enabling the laser cutting process while ensuring safety during laser use under the protection of the cavity mold outer cylinder 1. The composite material waste 10 generated after laser cutting is naturally ejected during the riveting process, assisting the cavity mold ejector 2 in providing the necessary support force for riveting. The ejected composite material waste 10 can be conveniently collected and disposed of after riveting.

[0044] Through specific experimental verification, when riveting identical metal materials and composite materials together, the laser-assisted riveting process proposed in this institute has advantages over existing riveting processes, including shorter connection time, no need for material pretreatment, and applicability to different composite material types. The thermal effect generated by laser cutting can effectively heat the metal materials being joined. Especially when joining aluminum alloys, the temperature generated can soften aged aluminum alloys and high-strength aluminum alloys, improving the material's plastic deformation capacity and enhancing the connection quality. Specific data are shown in the table below:

[0045]

[0046] Compared with existing technologies, this invention utilizes the difference in absorption capacity of resin-based composite materials and metal materials for laser energy in specific laser bands to achieve a continuous process of plastic deformation in laser cutting of composite and metal materials, thereby realizing riveting of composite and metal materials without pre-drilled holes. The laser generator 3 is built into the cavity mold ejector 2, which can realize the laser cutting process and ensure the safety of laser use under the protection of the outer cylinder 1 of the cavity mold. The composite waste 10 generated after laser cutting is naturally ejected during the riveting process and assists the cavity mold ejector 2 in providing the support force required for riveting. The ejected composite waste 10 can be conveniently collected and processed after riveting.

[0047] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. An integrated laser-assisted rivetless joining device, characterized in that, include: A die mechanism with a laser generator and a punch mechanism located below the sheet metal are arranged opposite to each other. The die mechanism includes: a housing and a core block, a die backing, a die outer cylinder, and a laser generator for rotating to achieve annular cutting of the composite material, wherein: the die outer cylinder is sleeved with the die backing, the laser generator passes through the core block and the die backing in sequence and faces the punch mechanism, and the composite material and metal material are arranged between the die backing and the punch mechanism in sequence.

2. The integrated laser-assisted rivetless joining device according to claim 1, characterized in that, The outer die cylinder includes: an outer die cylinder base and an outer die cylinder extension block connected thereto, wherein: the outer die cylinder base and the die backing are fitted together with clearance and are sleeved on the die backing through axial bearings and radial bearings, and the outer die cylinder extension block is located at the lowest end of the die mechanism and is in contact with the plate.

3. The integrated laser-assisted rivetless joining device according to claim 1, characterized in that, The laser generator is eccentrically positioned inside the concave mold core block and connected to the housing via the upper cover plate.

4. The integrated laser-assisted rivetless joining device according to claim 1, characterized in that, The punch mechanism includes a blank holder and a punch disposed therein, wherein the punch and the blank holder are in clearance fit, and the blank holder integrates a thermistor to detect the surface temperature of the metal material.

5. The integrated laser-assisted rivetless joining device according to claim 4, characterized in that, The diameter of the punch ,in The diameter of the hole is β, and the punch angle is β = 2°~10°.

6. A laser-assisted rivetless riveting method for composite materials and metal materials based on the device described in claim 4 or 5, characterized in that, First, the composite material is stacked on the metal material and placed on the pressure ring. After the connecting plate is pre-tightened by pressing down the die, the laser generator located in the reverse top of the die emits a laser beam and rotates to achieve a ring cut on the composite material. Under the forming force of the upward movement of the punch, the metal material is plastically deformed and a rivetless joint is formed by cutting holes in the composite material.

7. The laser-assisted rivetless joining method for composite materials and metal materials according to claim 6, characterized in that, The laser beam has a spot width of less than or equal to 0.3 mm, an annular spot diameter of less than or equal to 10 mm, and a laser source power P = at⁴ - b, where a = 120 W / mm and b = 60 W. The rotational scanning speed is... , n = 40mm / s, where: t4 is the diameter of the cut hole, and t4 is the thickness of the composite material.

8. The laser-assisted rivetless joining method for composite materials and metal materials according to claim 6, characterized in that, During the circumferential cutting process, the maximum temperature T of the composite material satisfies: et4 + 140 ℃ < T < et4 + 190 ℃, e = 30℃ / mm. When the maximum temperature exceeds the range, the circumferential cutting is unqualified and the process ends.

9. The laser-assisted rivetless joining method for composite materials and metal materials according to claim 6, characterized in that, The angle α between the cut surface formed by the ring cut and the surface of the composite material plate satisfies: 120° > α > 60°.

Images