Flat hole connection method by pulse laser impact, and device and application of the same

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, specifically to a method for flat hole connection by pulsed laser shock and its device and application. [Background technology]

[0002] The disclosure of such background information is not necessarily to be construed as an admission or in any manner suggesting 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 for fixing connections between plates include welding, crimping, and screw connections.

[0004] Traditional welding, as typified by fusion welding, involves the use of a high-temperature heat source to cause the material to be in a molten state, forming a metallurgical bond, which has high connection strength and high electrical conductivity. However, the fusion welding area may form a heat-affected zone, which may cause thermal deformation, the formation of non-uniform inclusions, and defects such as pores and cracks, which tend to reduce the fatigue resistance of the fusion welding joint. Laser impact welding is a new solid-state metallurgical bonding technology that avoids the adverse thermal effects of the fusion welding method, but still cannot significantly improve the fatigue resistance of the joint.

[0005] The crimping between plates includes crimping by rivets and rivetless crimping, both of which are usually performed at room temperature and therefore belong to the cold working category. Among them, rivetless crimping is connected only by the plastic deformation of the material itself and does not require rivets, so the processing speed is fast and it is easy to obtain a flat joint, and its application has become increasingly widespread in recent years. Compared with metallurgical bonding by welding, crimping belongs to mechanical bonding, and the fatigue resistance of the joint is good, but the shear strength and peel strength are low, and the conductive performance is poor. When connecting dissimilar materials with rivetless crimping, the different repulsion amounts of the dissimilar materials after deformation may loosen the joint and further reduce its conductivity.

[0006] The rivet welding composite connection technology combines the advantages of mechanical bonding of rivet and metallurgical bonding of welding, and to a certain extent solves the problems of low strength and low conductivity of simple rivet joints and low fatigue resistance of simple welded joints, so it has good application prospects in the field of connection of metal plate materials such as conductive plates. If welding is performed after rivet, rivet becomes more difficult due to the change in material performance caused during welding. If rivet is performed after welding, the position and angle of welding are limited due to the use of space in the rivet process, making welding more difficult. Therefore, the industry is making efforts to obtain a rivet welding composite joint by the simultaneous rivet welding process. A Chinese patent with application number 201510119083.0 discloses a method and apparatus for simultaneous rivet joining and welding joining of ultra-thin plate materials by laser. In this method, the upper and lower plates are stacked and placed together on a female mold, and the female mold is provided with a bottom mold. A pulsed laser beam is applied to the upper plate or the energy absorbing layer applied to the surface of the upper plate to form an explosion plasma, and the upper plate collides with the lower plate, and a plastic flow coupling with a high strain rate occurs between the upper plate and the lower plate. Under the constraint of the bottom mold, the upper plate and the lower plate are plastically formed into a rivet button shape together, thereby generating a mechanical mutual fastening and crimping joint. During plastic deformation, there is a compressive stress at the contact interface between the upper plate and the lower plate, so melting and atomic diffusion occur at the interface, and the upper plate and the lower plate are welded when they collide with the bottom mold together. However, the crimping weld joint of the extremely thin plate material realized by this method is mainly due to the joint plastic deformation of two layers of plate materials, so it is only suitable for connecting very thin plate materials with no significant difference in thickness.

[0007] In order to create the interlocking structure required for crimping, it is necessary to ensure that the directional flow of the two layers of plate materials is well combined, and both layers of plate materials must be able to produce very high deformation. Thick plate materials have high rigidity, and therefore the flow and filling performance of the material is low, making the directional flow of the material more difficult and less likely to produce large deformation. In general, additional measures must be taken, such as increasing the temperature to promote the flow of the material. In addition, when there is a large difference in thickness between the two layers of plate materials, the large thickness difference will cause poor flow coupling between the two layers of plate materials, making it easy for cracks to occur, and the connection quality will be poor. During deformation, the compressive stress at the connection interface mainly acts, and the large thickness difference will cause the pressure distribution during connection to be uneven, leading to local concentration of stress, deterioration of connection quality, and increasing the risk of connection instability and invalidation. 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 realize welding and crimping joints even for plate materials with a large thickness or a large difference in thickness, and has the characteristics of a flat joint, no protrusions, a large amount of mutual fastening, high joint strength, and good fatigue resistance and conductive 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 material with an hourglass-shaped through hole, an upper plate material, an absorbing 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; placing the hourglass-shaped through hole region at the center position of the spot of the pulsed laser light, and the pressure of the pulsed laser shock wave causes the upper plate material to undergo downward plastic deformation with a high strain rate, colliding with the upper inclined surface of the hourglass-shaped through hole of the lower plate material, causing high-speed shear deformation and producing a metallurgical welding joint effect; as the upper plate material continues to deform, the upper plate material flows into the cavity of the hourglass-shaped through hole of the lower plate material, and together with the lower inclined surface of the hourglass-shaped through hole of the lower plate material, forms an interlocking structure with a small top and a large bottom, producing a mechanical crimping joint effect; and completing a crimping welding composite connection in the shape of a flat hole, with the upper part utilizing welding and the lower part utilizing crimping. A method for connecting flat holes by pulsed laser impact is provided, comprising:

[0010] A second aspect of the present invention is an apparatus for implementing the above-mentioned 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 further including a laser for generating a pulsed laser.

[0011] The third aspect of the present invention provides the use of the method or the device for realizing the method in simultaneously performing crimping and welding on plates with large thicknesses or plates with large thickness differences. When the upper plate is thick, the upper plate is forced into the through-hole of the lower plate under the action of the laser impact force, the effect of which is similar to extrusion molding in the field of metal forming. When the lower plate is thick, through-holes of different sizes can be adopted to allow the upper plate to smoothly flow into the through-hole. When the lower plate is thin, small through-holes can be adopted, otherwise large through-holes are adopted.

[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 by having an upper taper and a lower taper. Before the laser impact, the upper plate and the upper inclined surface have a certain gap, 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, which generates high-speed shear deformation and can produce a metallurgical welding joint effect. As the upper plate continues to deform, the material further flows into the lower part 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 interlocking structure with a small upper part and a large lower part, which produces a mechanical crimping joint effect, 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.

[0013] (2) In the present invention, the upper plate undergoes plastic deformation under the laser impact, and the deformed upper plate flows into the hourglass-shaped through-hole of the lower plate, resulting in good directional flow of material. In addition, only the upper plate undergoes plastic strain under the laser impact, and there is no need to consider the problem of flow coupling between the two plate layers, so this application is suitable for simultaneous crimping and welding of plate materials with large thicknesses or plate materials with large thickness differences.

[0014] (3) The method provided by the present invention can be used for plate materials with small connection area, thick or large difference in thickness, and the crimped joint welded joint joint is flat hole type and has no geometric protrusion, solving the problem of crimped joint of 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 that the amount of mutual fastening is large and ensures high strength of the joint.

[0016] (5) In the upper plate material, high-strain plastic forming occurs due to the force effect of the laser shock wave, not due to a thermal effect, and the welding joint caused by high-speed collision and shear 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 material, so there are no issues due to 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, with a simple process and high processing efficiency.

[0018] The drawings in the specification, which form a part of the present invention, are intended to provide a further understanding of the present invention. The schematic examples of the present invention and the description thereof are intended to illustrate the present invention and are not to be construed as unduly limiting the present invention. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a schematic diagram of a flat hole connection device by pulsed laser impact in the present invention. [Diagram 2] 2 is a schematic diagram of an hourglass-shaped through hole in a lower layer plate material according to the present invention. FIG. [Diagram 3] FIG. 2 is a schematic diagram of an intermediate process of flat hole connection by pulsed laser shock in the present invention. [Figure 4] FIG. 2 is a schematic diagram showing the final completion of flat hole connection by pulsed laser shock in the present invention. [Diagram 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 PREFERRED EMBODIMENTS

[0020] The first exemplary embodiment of the present invention includes the steps of stacking the bottom mold, the lower plate with the hourglass-shaped through hole, the upper plate, the absorbing layer and the constraining layer in this order from the bottom, clamping each layer with a work clamping system and fixing it to a work table; placing the hourglass-shaped through hole area at the center position of the spot of the pulsed laser light, and the pressure of the pulsed laser shock wave causes the upper plate to undergo downward plastic deformation with a high strain rate, colliding with the upper inclined surface of the hourglass-shaped through hole of the lower plate, generating high-speed shear deformation and producing a metallurgical welding joint 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 interlocking structure with a small upper part and a large lower part, producing a mechanical crimping joint effect; and completing a crimping welding composite connection in the shape of a flat hole, with the upper part utilizing welding and the lower part utilizing crimping. A method for connecting flat holes by pulsed laser impact is provided, comprising:

[0021] In one or more embodiments, the bottom mold is used to limit deformation of the top 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, an upper inclined surface of the hourglass-shaped through hole of the lower layer plate is a welded inclined surface, and a lower inclined surface of the hourglass-shaped through hole of the lower layer plate is a crimped inclined surface.

[0024] In one or more embodiments, the value of the angle (acute angle) α between 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 between 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 angle α is greater than or equal to 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 board is H, and the vertical height of the lower inclined surface is h. α ≧x β The diameter of the connection between the upper and lower inclined surfaces is d=D-2×x α and d≧2×x β and

number

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

[0027] In one or more embodiments, in order to ensure the effect of simultaneously carrying out 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 the same or different plate materials, such as copper, aluminum, steel, titanium, and the like.

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

[0030] In one or more embodiments, the constraining layer is made of glass or water and is intended 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 in the direction of the plate material.

[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 spot and the pulse width of the laser.

[0032] Furthermore, the pulse width of the laser machine needs to be 20 ns or less so that the crimping and welding of the upper and lower plate materials can be completed 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 light spot, and the pulse width of the laser machine, it is possible to realize crimped joints of different material combinations, thickness combinations, and size standards.

[0035] A second exemplary embodiment of the present invention is an apparatus for implementing the above-mentioned 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 further including a laser for generating a pulsed laser.

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

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

[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 layers As shown in FIG. 5(a), the upper plate is a pure copper plate with a thickness of 0.05 mm, the lower plate is an aluminum alloy plate with a thickness of 0.15 mm, and the size of the hourglass-shaped through hole is D=0.35 mm, α=β=45°, h=0.075 mm, H=0.15 mm, x α =x β = 0.075mm, d = 0.2mm. The pulse width of the laser machine is 12ns, the diameter of the laser light spot is 2mm, and the laser energy is 5J. The hourglass-shaped through-hole area is placed at the center position of the pulsed laser light spot, and the pressure of the pulsed laser shock wave causes the upper plate material to undergo downward plastic deformation with a high strain rate, colliding with the upper inclined surface of the hourglass-shaped through-hole of the lower plate material, causing high-speed shear deformation, resulting in a metallurgical welding joint effect. As the upper plate material continues to deform, it flows into the cavity of the hourglass-shaped through-hole of the lower plate material, and together with the lower inclined surface of the hourglass-shaped through-hole of the lower plate material, forms an interlocking structure with a small top and a large bottom, resulting in a mechanical crimping joint effect. A crimping welding composite connection is completed, which is a flat hole-shaped hole with a welding upper part and a crimping lower part.

[0040] Example 2 As shown in FIG. 5(b), the upper plate is a 0.20 mm thick pure copper plate, the lower plate is an aluminum alloy plate, and the size of the hourglass-shaped through hole is D=0.7 mm, α=β=45°, h=0.10 mm, H=0.20 mm, x α =x β = 0.10mm, d = 0.5mm. The pulse width of the laser machine is 12ns, the diameter of the laser light spot is 2mm, and the laser energy is 10J. The hourglass-shaped through-hole area is placed at the center position of the pulsed laser light spot, and the pressure of the pulsed laser shock wave causes the upper plate material to undergo downward plastic deformation with a high strain rate, colliding with the upper inclined surface of the hourglass-shaped through-hole of the lower plate material, causing high-speed shear deformation, resulting in a metallurgical welding joint effect. As the upper plate material continues to deform, it flows into the cavity of the hourglass-shaped through-hole of the lower plate material, and together with the lower inclined surface of the hourglass-shaped through-hole of the lower plate material, forms an interlocking structure with a small top and a large bottom, resulting in a mechanical rivet joint effect. A rivet welding composite connection is completed, which is a flat hole shape, with the upper part using welding and the lower part using rivet.

[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. All 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. Bottom 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 absorbing layer and the constraint layer in this order from the bottom, clamping each layer with a work clamping system and fixing it to a work table; the step of placing the hourglass-shaped through hole region at the center position of the spot of the pulsed laser light, and the pressure of the pulsed laser shock wave causes the upper plate to undergo 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 joint 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, forming an interlocking 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, producing a mechanical crimping joint effect; and the step of completing a crimping welding composite connection in the shape of a flat hole, with the upper part utilizing welding and the lower part utilizing crimping. A method for connecting flat holes by pulsed laser impact, comprising:

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

3. an upper inclined surface of the hourglass-shaped through hole of the lower plate material is a welded inclined surface, and a lower inclined surface of the hourglass-shaped through hole of the lower plate material is a crimped inclined surface; Alternatively, the value of the angle α between the upper inclined surface of the hourglass-shaped through hole and the upper surface of the lower plate is in the range of 20 to 60°, the value of the angle β between the lower inclined surface of the hourglass-shaped through hole and the lower surface of the lower plate 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 α and d≧2×x β and [0025] The connecting method according to claim 1, characterized in that the large space on the upper inclined surface of the hourglass-shaped through hole of the lower plate can ensure the welding effect and make the material flow easily; and the combination of different parameters 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.

7. The connection 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 worktable is used to adjust the impact position.

10. Use of the connection method according to any one of claims 1 to 7 or the device according to any one of claims 8 to 9 in simultaneously performing crimping and welding on plate materials with a large thickness or plate materials with a large difference in thickness.

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