JP2025029599A - Flat hole connection method by pulsed laser shock and its device and application - Google Patents

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

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.

The disclosure of this background information is not necessarily intended to be an admission or in any manner suggestion that the information constitutes prior art already known to those skilled in the art, but is merely intended to enhance understanding of the overall background of the present invention.

The main methods for fixing connections between plates include welding, crimping, and screw connections.

Traditional welding, as typified by fusion welding, involves applying a high-temperature heat source to materials to cause them to become molten, forming a metallurgical bond, which provides high connection strength and high electrical conductivity. However, heat-affected zones may form in the fusion welding area, which can 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-welded joint. Laser impact welding is a novel solid-state metallurgical bonding technology that avoids the adverse thermal effects of fusion welding methods, but still fails to significantly improve the fatigue resistance of the joint.

Fastening between plate materials includes fastening with rivets and rivetless fastening, both of which are usually performed at room temperature and therefore belong to the category of cold working. Rivetless fastening, in particular, connects only through the plastic deformation of the material itself and does not require rivets, so it is fast to process and easy to obtain flat joints, and its application has become increasingly widespread in recent years. Compared to metallurgical bonding by welding, fastening belongs to mechanical bonding and the fatigue resistance of the joint is good, but the shear strength and peel strength are low, and the electrical conductivity is poor. When connecting dissimilar materials with rivetless fastening, the different repulsion amounts of the different materials after deformation can loosen the joint and further reduce its electrical conductivity.

The rivet welding composite connection technology combines the advantages of mechanical bonding of rivets 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 prospects for application in the field of connection of metal plate materials such as conductive plates. If welding is performed after rivet application, rivet becomes more difficult due to the change in material performance caused during welding. If rivet application 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 ultra-thin plate material realized by this method is mainly due to the joint plastic deformation of two layers of plate material, so it is only suitable for connecting very thin plate materials with no significant difference in thickness.

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 deformations. Thick plate materials have high rigidity, and therefore have low material flow and filling performance, making the directional flow of the material more difficult and less likely to produce large deformations. 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 them more likely to crack, and resulting in poor connection quality. During deformation, the compressive stress at the connection interface is the main force, and the large thickness difference will cause uneven pressure distribution during connection, leading to localized stress concentration, reduced connection quality, and increased risk of connection instability and invalidation.

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 even 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 electrical conductivity, as well as an apparatus and application thereof.

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 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; 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.
The present invention provides a method for connecting flat holes by pulsed laser impact, comprising:

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.

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 thick plates or plates with a large difference in thickness. 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 flow smoothly into the through-hole. When the lower plate is thin, small through-holes can be adopted, otherwise large through-holes are adopted.

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.

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

(3) The method provided by the present invention can be used for plate materials with a small connection area and a large difference in thickness. In addition, the crimped welded joint joint is flat hole-shaped and has no geometric protrusions, solving the problem of crimped welded joints for plate materials that have requirements for connection space.

(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 high strength of the joint is ensured.

(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, and the welding joint caused by high-speed collision and shearing between the upper inclined surfaces of the through holes in the upper and lower plates occurs instantaneously only on the surface of the plate, so there are no issues due to the heat-affected zone.

(6) The method provided by the present invention can achieve 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.

The drawings in the specification, which form part of the present invention, are intended to provide a further understanding of the present invention. The schematic examples of the present invention and their explanations are intended to aid in the interpretation of the present invention and do not constitute undue limitations on the present invention.

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

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 top and a large bottom, producing a mechanical crimping joint effect; 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;
The present invention provides a method for connecting flat holes by pulsed laser impact, comprising:

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

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

In one or more embodiments, the upper inclined surface of the hourglass-shaped through hole in the lower plate material is a welded inclined surface, and the lower inclined surface of the hourglass-shaped through hole in the lower plate material is a crimped inclined surface.

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 surface) of the lower plate material is in the range of 20 to 60°, the value of the angle (acute angle) β between the lower inclined surface of the hourglass-shaped through hole and the lower surface (horizontal surface) 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.

であり、下層板材の砂時計状スルーホールの上傾斜面における大きな空間により、溶接効果を確保し、材料を流動させやすくし、下層板材の砂時計状スルーホールの異なるパラメータの組合せにより、異なる性能及び適用場面を有する複合継手を得ることができる。 In one or more embodiments, the horizontal lengths of the upper inclined surface of the hourglass-shaped through hole in the lower plate material and the lower inclined surface of the hourglass-shaped through hole in the lower plate material are x _α and x _β , respectively, the diameter of the upper opening is D, the thickness of the lower plate material is H, and the vertical height of the lower inclined surface is h, then x _α ≧x _β , the diameter d at the connection part between the upper inclined surface and the lower inclined surface is D−2×x _α and d≧2×x _β ,

The large space on the upper inclined surface of the hourglass-shaped through hole of the lower plate ensures the welding effect and makes the material flow easily. Through the combination of different parameters of the hourglass-shaped through hole of the lower plate, composite joints with different performances and application scenarios can be obtained.

In one or more embodiments, the hourglass-shaped through holes in the lower 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.

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.

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, etc.

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 an extremely short time, and continues to absorb energy, forming laser shock waves that act as a driving force to push the plate material so as to generate plastic deformation with a high strain rate. In addition, the absorption layer further has the effect of protecting the surface of the material from laser burns.

In one or more embodiments, the constraining layer is made of glass or water, and aims to increase the peak pressure of the shock wave and extend its duration by restricting the expansion of the plasma. The constraining layer also propagates the shock wave in the direction of the plate material.

In one or more embodiments, the power density of the pulsed laser needs to be greater than 1 GW/ ^cm2 , with the specific value depending on the laser energy, the size of the laser light spot, and the pulse width of the laser machine.

Furthermore, the pulse width of the laser machine must 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.

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 plate material.

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 welding joints with different material combinations, thickness combinations, and size standards.

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.

In one or more embodiments, the worktable is used to adjust the impact position.

A third exemplary embodiment of the present invention provides for the use of the method or an apparatus for implementing the method in the simultaneous crimping and welding of plate materials having a large thickness or plate materials having a large difference in thickness.

In order to allow those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with specific examples.

Example 1: Case where there is a large difference in thickness between the upper and lower plate materials As shown in (a) of FIG. 5, the upper plate material is a 0.05 mm thick pure copper plate, the lower plate material is a 0.15 mm thick aluminum alloy plate, and the size of the hourglass-shaped through hole is designed to be D = 0.35 mm, α = β = 45 °, h = 0.075 mm, H = 0.15 mm, x _α = x _β = 0.075 mm, d = 0.2 mm. The pulse width of the laser machine is 12 ns, the diameter of the laser light spot is 2 mm, and the laser energy is 5 J. The hourglass-shaped through hole region is placed at the center position of the pulse laser light spot, and the pressure of the pulse laser shock wave causes the upper plate material to undergo plastic deformation with a high strain rate downward, 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 joining effect. As the upper plate continues to deform, it flows into the cavity of the hourglass-shaped through hole of the lower plate, forming a mutual fastening 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, resulting in a mechanical crimping joint effect. A crimping-welded composite connection is completed, with a flat hole-like shape, the top using welding and the bottom using crimping.

Example 2
As shown in (b) of Fig. 5, the upper plate material is a 0.20mm thick pure copper plate, the lower plate material is an aluminum alloy plate, and the size of the hourglass-shaped through hole is designed to be D = 0.7mm, α = β = 45°, h = 0.10mm, H = 0.20mm, _xα = _xβ = 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 pulse laser light spot, and the pressure of the pulse laser shock wave causes the upper plate material to undergo downward plastic deformation with a high strain rate, which collides 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 joining effect. As the upper plate continues to deform, it flows into the cavity of the hourglass-shaped through hole of the lower plate, forming a mutual fastening 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, resulting in a mechanical crimping joint effect. A crimping-welded composite connection is completed, with a flat hole-like shape, the top using welding and the bottom using crimping.

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 may make various modifications and variations to the present invention. All modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

REFERENCE SIGNS LIST 1 Laser machine 2 Work clamping system 3 Constraint layer 4 Absorption layer 5 Upper plate material 6 Lower plate material with hourglass-shaped through hole 7 Bottom mold 8 Work table

Claims (10)

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 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, 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 joining 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: The connection method described in claim 1, characterized in that the bottom mold is used to limit deformation of the upper plate material and form a flat-hole shaped crimped welded joint. 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, if the horizontal lengths of the upper inclined surface of the hourglass-shaped through hole in the lower plate material and the lower inclined surface of the hourglass-shaped through hole in the lower plate material are x _α and x _β , respectively, the diameter of the upper opening is D, the thickness of the lower plate material is H, and the vertical height of the lower inclined surface is h, then x _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 ;

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. The connection method according to claim 3, characterized in that the thickness H of the lower layer plate material is 0.1 mm or more. 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. The connection method according to claim 1 , wherein the power density of the pulsed laser needs to be greater than 1 GW/cm ² . 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. 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. The device according to claim 8, characterized in that the worktable is used to adjust the impact position. 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 large thicknesses or plate materials with large differences in thickness.

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