Flat-hole connection method by pulsed laser shock, its device and application

Abstract

To provide a flat hole connection method by pulse laser impact.SOLUTION: A flat hole connection method by pulse laser impact includes the steps of: laminating and arranging a bottom mold, a lower layer plate material with a sandglass-shaped through hole, an upper layer plate material, an absorption layer and a constrained layer in this order from below, and fixing each of the layers while sandwiching the layers with a workpiece sandwiching system; placing a sandglass-shaped through hole region at a central position of a spot of a pulse laser beam, generating plastic deformation of a high distortion rate in a downward direction in the upper layer plate material by a pressure of a pulse laser impulse wave, making the upper layer plate material collide with an upper inclined surface of the sandglass-shaped through hole of the lower layer plate material, generating high speed shear deformation, and generating a metallurgical weld joint effect; and making the upper layer plate material forming a mutually coupled structure having a small upper part and a large bottom together with a lower inclined surface of the sandglass-shaped through hole of the lower layer plate material, when making the upper layer plate material flow in a cavity of the sandglass-shaped through hole, as the upper layer plate material continues to be deformed, and generating a mechanical caulking and joining effect. The connection method is used in welding and joining or caulking and joining of a plate material having a large thickness difference.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention belongs to the technical field of advanced laser manufacturing, and particularly to a method for flat-hole connection by pulsed laser impact and its device and application. [Background technology]

[0002] The disclosure of such background information is not necessarily considered an admission or in any way an indication that such information constitutes prior art already known to those skilled in the art, but is merely intended to enhance understanding of the overall context of the present invention.

[0003] The main methods of fixing the plates together include welding, caulking, and screwing.

[0004] Traditional welding, such as fusion welding, involves using a high-temperature heat source to melt materials and form a metallurgical bond, resulting in high joint strength and high electrical conductivity. However, the fusion welding area can sometimes form a heat-affected zone, which can lead to thermal deformation, uneven inclusion formation, and defects such as porosity and cracks, reducing the fatigue resistance of the fusion-welded joint. Laser impact welding is a novel solid-state metallurgical joining technology that avoids the adverse thermal effects of fusion welding, but still fails to significantly improve the fatigue resistance of the joint.

[0005] Crimping between plates includes rivet-based and rivetless crimping, both of which are typically performed at room temperature and therefore fall under the category of cold working. Rivetless crimping, in particular, connects materials solely through plastic deformation of the materials themselves, eliminating the need for rivets, allowing for faster processing and easier production of flat joints, leading to increasingly widespread application in recent years. Compared with metallurgical joining by welding, crimping is a mechanical joint, resulting in better joint fatigue resistance but lower shear strength, peel strength, and poor electrical conductivity. When connecting dissimilar materials using rivetless crimping, the different repulsive forces of the dissimilar materials after deformation can loosen the joint and further reduce its electrical conductivity.

[0006] The crimp-weld hybrid connection technology combines the mechanical bonding advantages of crimping and the metallurgical bonding advantages of welding. It has some potential applications in the field of connecting metal sheets, such as conductive plates, by resolving, to a certain extent, the problems of low strength and conductivity of simple crimped joints and low fatigue resistance of simple welded joints. However, when welding is performed first and then crimping is more difficult due to changes in material properties that occur during welding. When crimping is performed first and then welding is more difficult due to the limited welding position and angle caused by the space required during the crimping process. For this reason, the industry is making efforts to achieve crimp-weld hybrid joints through simultaneous crimping and welding processes. Chinese patent application number 201510119083.0 discloses a method and apparatus for simultaneous laser crimping and welding of ultra-thin sheet materials. In this method, the upper and lower sheets are stacked and placed together on a female mold, which is equipped with a bottom mold. A pulsed laser beam is applied to the upper sheet or the energy-absorbing layer coated on the surface of the upper sheet, forming an explosive plasma, which causes the upper sheet to collide with the lower sheet, resulting in high-strain plastic flow coupling between the upper and lower sheets. Under the constraint of the bottom mold, the upper and lower sheets are plastically formed together into a rivet button shape, thereby creating a mechanical fastening and crimping joint. During plastic deformation, compressive stress is generated at the contact interface between the upper and lower sheets, causing melting and atomic diffusion at the interface, and the upper and lower sheets are welded together when they collide with the bottom mold. However, the crimping weld joint of ultra-thin sheets achieved by this method is mainly due to the joint plastic deformation of the two sheets, so it is only suitable for connecting very thin sheets with little difference in thickness.

[0007] To create the interlocking structure required for crimping, it is necessary to ensure good directional flow coupling between the two layers of material, while also ensuring that both layers are able to undergo very high deformation. Thick materials have high rigidity and poor material flow and filling properties, making directional flow more difficult and reducing the likelihood of large deformation. Therefore, additional measures, such as increasing the temperature to promote material flow, are generally required. Furthermore, when there is a large difference in thickness between the two layers of material, the large thickness difference can lead to poor flow coupling between the two layers, making cracks more likely to occur and reducing connection quality. During deformation, compressive stress acts primarily at the connection interface. Large thickness differences result in uneven pressure distribution during the connection, leading to localized stress concentrations, reduced connection quality, and increased risk of connection instability and failure. Summary of the Invention

[0008] In order to solve the above problems, the present invention provides a method for connecting flat holes by pulsed laser impact, which can simultaneously achieve welding and crimping joints for plate materials with large thicknesses or large differences in thickness, and which has the characteristics of a flat joint, no protrusions, a large amount of mutual fastening, high joint strength, and good fatigue resistance and conductivity performance, as well as an apparatus and application thereof.

[0009] The first aspect of the present invention includes the steps of stacking a bottom mold, a lower plate with an hourglass-shaped through hole, an upper plate, an absorption layer, and a constraint layer in this order from the bottom, clamping each layer with a work clamping system and fixing it to a work table; locating the hourglass-shaped through hole region at the center of the spot of the pulsed laser light, and causing the upper plate to undergo downward plastic deformation with a high strain rate due to the pressure of the pulsed laser shock wave, which causes it to collide with the upper inclined surface of the hourglass-shaped through hole of the lower plate, causing high-speed shear deformation and producing a metallurgical welding joining effect; as the upper plate continues to deform, the upper plate flows into the cavity of the hourglass-shaped through hole of the lower plate, and together with the lower inclined surface of the hourglass-shaped through hole of the lower plate, forms an interconnected structure with a small top and a large bottom, producing a mechanical crimping joining effect; and completing a crimping welding composite connection in the shape of a flat hole, where the top is welded and the bottom is crimped. A method for connecting flat holes by pulsed laser impact is provided, including:

[0010] A second aspect of the present invention is an apparatus for realizing the above method, comprising a bottom mold, a lower plate material with an hourglass-shaped through hole, an upper plate material, an absorption layer, and a constraint layer, which are stacked in this order from the bottom, and a work clamping system clamps each layer and fixes them to a work table; An apparatus is provided that further includes a laser machine for generating a pulsed laser.

[0011] A third aspect of the present invention provides the use of the above method or an apparatus for implementing the method in simultaneously performing crimping and welding on thick or significantly different thickness plates. When the upper plate is thick, the upper plate is forced into the through-hole of the lower plate under the action of a laser impact force, an effect similar to extrusion molding in the field of metal forming. When the lower plate is thick, through-holes of different sizes can be used to allow the upper plate to flow smoothly into the through-hole. When the lower plate is thin, smaller through-holes can be used, and otherwise, larger through-holes are used.

[0012] The beneficial effects of the present invention are as follows: (1) The lower plate has an hourglass-shaped through hole with an upper inclined surface and a lower inclined surface, with one upper taper and one lower taper. Before the laser impact, there is a certain gap between the upper plate and the upper inclined surface, which provides a certain flight distance for the laser impact area of ​​the upper plate. During the laser impact, the upper plate collides with the upper inclined surface of the lower plate at high speed, causing high-speed shear deformation and resulting in a metallurgical welding joint effect. As the upper plate continues to deform, more material flows into the bottom of the hourglass-shaped through hole of the lower plate, forming a small-top, large-bottom interconnection structure with the lower inclined surface of the hourglass-shaped through hole of the lower plate, resulting in a mechanical crimping joint effect, completing a crimping-welded composite connection like a flat hole, with the top welded and the bottom crimped.

[0013] (2) In the present invention, plastic deformation occurs in the upper layer plate material under laser impact, and the deformed upper layer plate material flows into the hourglass-shaped through-holes in the lower layer plate material, resulting in good directional flow of material. Furthermore, since plastic strain occurs only in the upper layer plate material under laser impact, there is no need to consider the issue of flow coupling between the two layers of plate material. Therefore, this application is suitable for simultaneously performing crimping and welding on plate materials with large thicknesses or plate materials with a large difference in thickness.

[0014] (3) The method provided by the present invention can be used for plate materials with small connection areas, thick plates, or plates with large thickness differences. In addition, the crimped welded joint is a flat hole with no geometric protrusions, solving the problem of crimped welded joints for plate materials with requirements for connection space.

[0015] (4) The method provided by the present invention can realize mechanical and metallurgical bonding, and has high strength, fatigue resistance, and electrical conductivity. In the present invention, the amount of mutual fastening depends on the macroscopic shape of the lower plate material, not on the deformation difference in the thickness direction, so the amount of mutual fastening is large and ensures high joint strength.

[0016] (5) The upper plate undergoes high-strain plastic forming due to the force effect of the laser shock wave, not due to a thermal effect. The high-speed collision and shear welding between the upper inclined surfaces of the through-holes in the upper and lower plate materials occurs instantaneously only on the surface of the plate, eliminating the problems associated with the heat-affected zone.

[0017] (6) The method provided by the present invention can realize the simultaneous completion of a composite connection of crimping and welding of plate materials under the action of laser pulses, and the process is simple and the processing efficiency is high.

[0018] The drawings in the specification, which form a part of this specification, are intended to provide a further understanding of the invention. The illustrative examples of the invention and their descriptions are intended to illustrate the invention and are not to be construed as an undue limitation on the invention. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram of a flat hole connection device by pulsed laser impact in the present invention. FIG. [Figure 2] 1 is a schematic diagram of an hourglass-shaped through hole in a lower layer plate material according to the present invention. [Figure 3] 1 is a schematic diagram of an intermediate process of flat hole connection by pulsed laser impact in the present invention. FIG. [Figure 4] FIG. 1 is a schematic diagram showing the final completion of flat hole connection by pulsed laser shock in the present invention. [Figure 5] 1A and 1B are schematic diagrams of the final connection member for flat hole connection by pulsed laser impact in the present invention, where (a) is a schematic diagram of the final connection member for plate materials with a large difference in thickness, and (b) is a schematic diagram of the final connection member for plate materials with a large thickness. DETAILED DESCRIPTION OF THE INVENTION

[0020] A first exemplary embodiment of the present invention includes the steps of stacking a bottom mold, a lower plate with an hourglass-shaped through hole, an upper plate, an absorption layer, and a constraint layer in this order from the bottom, clamping each layer with a work clamping system and fixing it to a work table; locating the hourglass-shaped through hole area at the center position of the spot of the pulsed laser light, and under the pressure of the pulsed laser shock wave, the upper plate undergoes downward plastic deformation with a high strain rate, colliding with the upper inclined surface of the hourglass-shaped through hole of the lower plate, causing high-speed shear deformation and producing a metallurgical welding joining effect; as the upper plate continues to deform, the upper plate flows into the cavity of the hourglass-shaped through hole of the lower plate, and together with the lower inclined surface of the hourglass-shaped through hole of the lower plate, forms an interconnected structure with a small top and a large bottom, producing a mechanical crimping joining effect; and completing a crimping welding composite connection in the shape of a flat hole, with the top using welding and the bottom using crimping. A method for connecting flat holes by pulsed laser impact is provided, including:

[0021] In one or more embodiments, the bottom mold is used to limit deformation of the upper plate material to form a flat-hole crimped welded joint.

[0022] In one or more embodiments, the upper plate material is a flat plate material.

[0023] In one or more embodiments, the upper inclined surface of the hourglass-shaped through hole of the lower plate material is a welding inclined surface, and the lower inclined surface of the hourglass-shaped through hole of the lower plate material is a caulking inclined surface.

[0024] In one or more embodiments, the value of the angle (acute angle) α formed by the upper inclined surface of the hourglass-shaped through hole and the upper surface (horizontal plane) of the lower plate material is in the range of 20 to 60°, and the value of the angle (acute angle) β formed by the lower inclined surface of the hourglass-shaped through hole and the lower surface (horizontal plane) of the lower plate material is in the range of 20 to 60°, and the angle α is greater than or equal to the angle β.

[0025] In one or more embodiments, the horizontal lengths of the upper inclined surface of the hourglass-shaped through hole of the lower plate material and the lower inclined surface of the hourglass-shaped through hole of the lower plate material are respectively x α , x β , the diameter of the upper opening is D, the thickness of the lower plate is H, and the vertical height of the lower inclined surface is h. α ≧x β The diameter d at the connection between the upper and lower inclined surfaces is D-2×x α and d≧2×x β and

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[0026] In one or more embodiments, the hourglass-shaped through holes in the lower plate may be achieved by drilling into both sides of the plate with a drill bit, or by laser drilling, which can create a natural taper and drill holes in hard, brittle materials.

[0027] In one or more embodiments, in order to ensure the effect of simultaneous welding and crimping, the thickness H of the lower plate material is 0.1 mm or more.

[0028] In one or more embodiments, the upper and lower plate materials may be made of the same or different materials, such as copper, aluminum, steel, or titanium.

[0029] In one or more embodiments, the absorption layer is made of black lacquer, graphite, or metal foil. When the absorption layer is irradiated with a laser, high-temperature, high-pressure plasma is generated within a very short time, continuously absorbing energy and forming laser shock waves, which act as a driving force to push the plate material and generate high-strain plastic deformation. In addition, the absorption layer also has the function of protecting the surface of the material from laser burns.

[0030] In one or more embodiments, the constraining layer is made of glass or water and serves to restrict the expansion of the plasma, thereby increasing the peak pressure of the shock wave and extending its duration. The constraining layer also propagates the shock wave toward the plate.

[0031] In one or more embodiments, the power density of the pulsed laser is greater than or equal to 1 GW / cm. 2 The specific value depends on the laser energy, the size of the laser light spot, and the pulse width of the laser.

[0032] Furthermore, the pulse width of the laser machine must be 20 ns or less so that the upper and lower plate materials can be joined by caulking and welding with a single laser.

[0033] Furthermore, in order to obtain laser energy close to a flat-top distribution, the size of the laser light spot must be at least 1.5 times the diameter D of the upper opening of the hourglass-shaped through-hole in the lower layer plate material.

[0034] Furthermore, by adjusting the laser energy, the size of the laser beam spot, and the pulse width of the laser machine, it is possible to realize crimped welding joints with different material combinations, thickness combinations, and size standards.

[0035] A second exemplary embodiment of the present invention is an apparatus for implementing the method, comprising: a bottom mold, a lower plate material with an hourglass-shaped through hole, an upper plate material, an absorption layer, and a constraint layer, which are stacked in this order from the bottom; a work clamping system clamps each layer and fixes them to a work table; An apparatus is provided that further includes a laser machine for generating a pulsed laser.

[0036] In one or more embodiments, the work table is used to adjust the impact location.

[0037] A third exemplary embodiment of the present invention provides the use of the method or the device for implementing the method in the simultaneous crimping and welding of plates with large thicknesses or plates with large thickness differences.

[0038] In order to make those skilled in the art understand the technical solution of the present invention more clearly, the technical solution of the present invention will be described in detail below through specific examples.

[0039] Example 1: When there is a large difference in thickness between the upper and lower plate materials As shown in FIG. 5(a), the upper plate material is a pure copper plate with a thickness of 0.05 mm, the lower plate material is an aluminum alloy plate with a thickness of 0.15 mm, and the dimensions of the hourglass-shaped through hole are D=0.35 mm, α=β=45°, h=0.075 mm, H=0.15 mm, x α =x β The dimensions were designed to be φ = 0.075 mm, d = 0.2 mm. The laser pulse width was 12 ns, the laser spot diameter was 2 mm, and the laser energy was 5 J. The hourglass-shaped through-hole area was positioned at the center of the pulsed laser spot. The pressure of the pulsed laser shock wave caused the upper plate to undergo downward plastic deformation at a high strain rate, colliding with the upper inclined surface of the hourglass-shaped through-hole in the lower plate, causing high-speed shear deformation and creating a metallurgical welding joint. As the upper plate continued to deform, it flowed into the cavity of the hourglass-shaped through-hole in the lower plate and formed an interconnected structure with the lower inclined surface of the hourglass-shaped through-hole in the lower plate, with a small top and a large bottom, creating a mechanical crimping joint. A crimping-welded hybrid connection was completed, with a flat hole shape, the top welded and the bottom crimped.

[0040] Example 2 As shown in FIG. 5(b), the upper plate material is a 0.20 mm thick pure copper plate, the lower plate material is a 0.20 mm thick aluminum alloy plate, and the dimensions of the hourglass-shaped through hole are D=0.7 mm, α=β=45°, h=0.10 mm, H=0.20 mm, x α =x β The dimensions were designed to be 0.10 mm, d = 0.5 mm. The laser pulse width was 12 ns, the laser spot diameter was 2 mm, and the laser energy was 10 J. The hourglass-shaped through-hole area was positioned at the center of the pulsed laser spot. The pressure of the pulsed laser shock wave caused the upper plate to undergo downward plastic deformation at a high strain rate, colliding with the upper inclined surface of the hourglass-shaped through-hole in the lower plate, causing high-speed shear deformation and creating a metallurgical welding joint. As the upper plate continued to deform, it flowed into the cavity of the hourglass-shaped through-hole in the lower plate and formed an interconnected structure with the lower inclined surface of the hourglass-shaped through-hole in the lower plate, with a small top and a large bottom, creating a mechanical crimping joint. A crimping-welded hybrid connection was completed, with a flat hole shape, the top welded and the bottom crimped.

[0041] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art can make various modifications and variations to the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention. [Explanation of symbols]

[0042] 1. Laser machine 2 Work clamping system 3 restraint layer 4 Absorbing layer 5 Upper plate material 6 Lower layer board with hourglass-shaped through holes 7 Bottom mold 8 Workbench

Claims

1. the step of stacking the bottom mold, the lower plate with the hourglass-shaped through hole, the upper plate, the absorption layer, and the constraint layer in this order from the bottom, and clamping each layer with a work clamping system and fixing it to a work table; the step of placing the hourglass-shaped through hole area at the center position of the spot of the pulsed laser light, and causing the upper plate to undergo downward plastic deformation with a high strain rate due to the pressure of the pulsed laser shock wave, causing it to collide with the upper inclined surface of the hourglass-shaped through hole of the lower plate, resulting in high-speed shear deformation and creating a metallurgical welding joining effect; the step of flowing the upper plate into the cavity of the hourglass-shaped through hole of the lower plate as the upper plate continues to deform, and forming an interconnected structure with a small top and a large bottom together with the lower inclined surface of the hourglass-shaped through hole of the lower plate, creating a mechanical crimping joining effect; the step of completing a crimping welding composite connection in the shape of a flat hole, with the upper part using welding and the lower part using crimping. A method for connecting flat holes by pulsed laser impact, comprising:

2. The connecting method according to claim 1, wherein the bottom mold is used to limit deformation of the upper plate material to form a flat-hole type crimped welded joint.

3. an upper inclined surface of the hourglass-shaped through hole of the lower plate material is a welding inclined surface, and a lower inclined surface of the hourglass-shaped through hole of the lower plate material is a caulking inclined surface; Alternatively, the value of the angle α formed by the upper inclined surface of the hourglass-shaped through hole and the upper surface of the lower plate material is in the range of 20 to 60°, the value of the angle β formed by the lower inclined surface of the hourglass-shaped through hole and the lower surface of the lower plate material is in the range of 20 to 60°, and the angle α is equal to or greater than the angle β; Alternatively, the horizontal lengths of the upper inclined surface of the hourglass-shaped through hole of the lower plate material and the lower inclined surface of the hourglass-shaped through hole of the lower plate material are respectively x α , x β , the diameter of the upper opening is D, the thickness of the lower plate is H, and the vertical height of the lower inclined surface is h. α ≧x β and the diameter d at the connection between the upper inclined surface and the lower inclined surface is D-2 x x α and d≧2×x β and [Equation 2] The connecting method of claim 1, characterized in that the large space on the upper inclined surface of the hourglass-shaped through hole of the lower plate ensures the welding effect and makes it easy for the material to flow, and different parameter combinations of the hourglass-shaped through hole of the lower plate can obtain composite joints with different performances and application scenarios.

4. 4. The connection method according to claim 3, wherein the thickness H of the lower plate material is 0.1 mm or more.

5. The upper and lower plate materials may be the same or different plate materials such as copper, aluminum, steel, titanium, etc. Alternatively, the absorbent layer is made of black lacquer, graphite or metal foil; Alternatively, the constraining layer is made of glass or water.

6. The power density of the pulsed laser is 1 GW / cm ２ 2. The connection method according to claim 1, wherein the first and second inputs are required to be larger than the first and second inputs.

7. The pulse width of the pulsed laser must be 20 ns or less. Alternatively, the connecting method according to claim 6, wherein the size of the spot of the laser light must be at least 1.5 times the diameter D of the upper opening of the hourglass-shaped through hole in the lower plate material.

8. An apparatus capable of implementing the connection method according to any one of claims 1 to 7, comprising a bottom mold, a lower plate material with an hourglass-shaped through hole, an upper plate material, an absorption layer, and a constraint layer, which are stacked in this order from the bottom, and each layer is clamped by a work clamping system and fixed to a work table; The apparatus further comprising a laser for generating a pulsed laser.

9. 9. The apparatus of claim 8, wherein the work table is used to adjust the impact position.

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