Pulse laser shock flat hole connection method, device and application thereof

Abstract

The application belongs to the field of laser advanced manufacturing technology, and particularly relates to a method for connecting flat holes by pulse laser impact, a device thereof and application. The method for connecting flat holes by pulse laser impact comprises the following steps: placing bottom die, lower layer plate with sandglass-shaped through hole, upper layer plate, absorbing layer and constraint layer in sequence from bottom to top; clamping and fixing each layer by using a workpiece clamping system; placing the sandglass-shaped through hole region at the center of the pulse laser spot; under the pressure of the pulse laser impact wave, the upper layer plate is plastically deformed at high strain rate and impacts the upper inclined surface of the sandglass-shaped through hole of the lower layer plate, so that high-speed shear deformation occurs, thereby generating a metallurgical welding effect; with the continuous deformation of the upper layer plate, when the upper layer plate flows into the cavity of the sandglass-shaped through hole, an interlocking structure with small upper part and large bottom part is formed between the upper layer plate and the lower inclined surface of the sandglass-shaped through hole of the lower layer plate, thereby generating a mechanical riveting effect; the method provided by the application is used for welding and riveting of thicker or larger-thickness-difference plates.

Description

Technical Field

[0001] This invention belongs to the field of advanced laser manufacturing technology, specifically relating to a method, apparatus and application of flat hole connection by pulsed laser impact. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] The main static connection methods between plates include welding, riveting, and threaded connection.

[0004] Traditional welding, represented by fusion welding, involves applying a high-temperature heat source to materials until they reach a molten state, forming a metallurgical bond. This results in high joint strength and electrical conductivity. However, the fusion weld area creates a heat-affected zone, which is prone to thermal deformation, the formation of uneven inclusions, and defects such as porosity and cracks, leading to lower fatigue resistance in the welded joint. Laser shock welding is an emerging solid-state metallurgical bonding technology that avoids the adverse thermal effects of fusion welding, but the fatigue resistance of the joint still cannot be significantly improved.

[0005] Riveting between sheet metal includes rivet riveting and rivetless riveting, both typically performed at room temperature and thus considered cold working. Rivetless riveting relies solely on the plastic deformation of the materials themselves for connection. Because it eliminates the need for rivets, it offers faster processing speeds and easily produces smooth joints, leading to its increasingly widespread application in recent years. Compared to the metallurgical bond formed by welding, riveting is a mechanical bond with good fatigue resistance, but lower shear strength, peel strength, and electrical conductivity. When riveting dissimilar materials, the varying springback rates after deformation can cause the joint to loosen, further weakening its conductivity.

[0006] The riveting and welding composite connection technology has the advantages of mechanical combination of riveting and metallurgical combination of welding, and to some extent solves the problems of low strength and poor electrical conductivity of pure riveting joint and poor fatigue resistance of pure welding joint, and thus has good application prospect in the field of connection of metal plates such as conductive plates. The material property change caused by the welding process increases the difficulty of riveting in the riveting first and then welding process, and the space occupied by the riveting process limits the position and angle of welding in the welding first and then riveting process, thereby increasing the difficulty of welding. Therefore, the synchronous riveting and welding process is always the direction of the industry to obtain the riveting and welding composite joint. The Chinese patent document with the application number 201510119083.0 discloses a method and device for laser synchronous riveting and welding of ultra-thin plates. The method stacks the upper plate and the lower plate together and places them on a concave die, the concave die is provided with a bottom die, a pulsed laser beam is used to act on the upper plate or the energy absorption layer coated on the surface of the upper plate to form an explosive plasma, the upper plate is thereby impacted on the lower plate, the upper plate and the lower plate are coupled by high strain rate plastic flow, and under the constraint of the bottom die, the upper plate and the lower plate are jointly plastic formed into a rivet shape, thereby producing mechanical interlocking to rivet. During the plastic deformation process, there is a compressive stress on the contact interface between the upper plate and the lower plate, the interface thus melts and atomically diffuses, and when the upper plate and the lower plate jointly impact on the bottom die, the upper plate and the lower plate are welded together. However, the riveting and welding joint of the ultra-thin plate realized by the method mainly relies on the joint plastic deformation of the double-layer plates, and thus is only suitable for connecting very thin plates and plates with small thickness difference.

[0007] The creation of the interlocking structure required for riveting needs to ensure that the directional flow of the two layers of plates is well matched, and at the same time, both layers of plates need to produce a large amount of deformation. For thicker plates, they have higher stiffness, and thus the flow performance and filling performance of the material are poor, which increases the difficulty of directional flow of the material and makes it difficult to produce a large amount of deformation, and generally requires additional measures such as increasing the temperature to promote the flow of the material. At the same time, if the thickness difference between the two layers of plates is large, the large thickness difference will lead to poor flow matching between the two layers of plates, and it is easy to produce cracks and poor connection quality. During the deformation process, the compressive stress on the connection interface is dominant, and the large thickness difference will also lead to uneven pressure distribution during connection, causing local stress concentration, reducing the connection quality, and increasing the fragility and failure risk of the connection. SUMMARY

[0008] In order to overcome the above problems, the present application provides a pulsed laser impact flat hole connection method, device and application. For plates with large thickness or large thickness difference, welding and riveting can also be realized at the same time, and the joint is flat, without protrusions, has large interlocking amount, high joint strength, good fatigue resistance and electrical conductivity, etc.

[0009] In a first aspect of the present application, a pulsed laser impact flat hole connection method is provided, the method comprising:

[0010] The bottom mold, the lower layer plate with the sandglass-shaped through hole, the upper layer plate, the absorbing layer and the constraint layer are placed in sequence from bottom to top, each layer is clamped and fixed on the workbench by using a workpiece clamping system; the sandglass-shaped through hole region is placed at the center of the pulsed laser spot, under the pressure of the pulsed laser shock wave, the upper layer plate is subjected to high strain rate plastic deformation downward, impacts the upper inclined surface of the sandglass-shaped through hole of the lower layer plate, and is subjected to high-speed shear deformation, so that a metallurgical welding effect is generated; as the upper layer plate continues to deform, when the upper layer plate flows into the cavity of the sandglass-shaped through hole of the lower layer plate, an upper-small-bottom-large interlocking structure is formed with the lower inclined surface of the sandglass-shaped through hole of the lower layer plate, so that a mechanical riveting effect is generated; the riveting and welding composite connection of the flat hole, upper welding and lower riveting is completed.

[0011] The second aspect of the present application provides a device for implementing the above method, the device comprising: a bottom mold, a lower layer plate with a sandglass-shaped through hole, an upper layer plate, an absorbing layer and a constraint layer placed in sequence from bottom to top, and each layer is clamped and fixed on the workbench by using a workpiece clamping system.

[0012] The device further comprises a laser for generating pulsed laser.

[0013] The third aspect of the present application provides the above method or the device for implementing the above method for synchronously riveting and welding the plate with large thickness or the plate with large difference in thickness. When the upper layer plate is thick, under the action of laser impact force, the upper layer plate is extruded into the through hole of the lower layer plate, and the effect is similar to that of extrusion forming in the field of metal forming. When the lower layer plate is thick, different sizes of through holes can be adopted to make the upper layer plate flow into the through hole smoothly. When the lower layer plate is thin, smaller through holes can be adopted, otherwise, larger through holes can be adopted.

[0014] The present application has the following beneficial effects:

[0015] (1) The sandglass-shaped through hole is formed on the lower layer plate, the through hole has an upper taper and a lower taper, so that the sandglass-shaped through hole of the lower layer plate has an upper inclined surface and a lower inclined surface; before laser impact, the upper layer plate has a certain gap with the upper inclined surface, the gap provides a certain flight distance for the laser impact region of the upper layer plate, when laser impact, the upper layer plate can impact the upper inclined surface of the lower layer plate at high speed, and high-speed shear deformation occurs, so that a metallurgical welding effect is generated, as the upper layer plate continues to deform, the material will further flow into the lower part of the sandglass-shaped through hole of the lower layer plate, and an upper-small-bottom-large interlocking structure is formed with the lower inclined surface of the sandglass-shaped through hole of the lower layer plate, so that a mechanical riveting effect is generated, thereby completing the riveting and welding composite connection of the flat hole, upper welding and lower riveting.

[0016] (2) The upper layer plate in the application is plastically deformed under laser impact, and the deformed upper layer plate flows into the hourglass-shaped through hole of the lower layer plate, so that the material directional flow is good. At the same time, only the upper layer plate is plastically deformed under laser impact, and the flow matching problem between the two layer plates does not need to be considered, so the application is suitable for synchronous riveting and welding of plates with large welding thickness or plates with large thickness difference.

[0017] (3) The method provided by the application has small connection area and can be used for plates with large thickness or large thickness difference; at the same time, the riveting and welding joint is a flat hole, and there is no geometric protrusion, so the problem of riveting and welding connection of plates with space requirements is solved.

[0018] (4) The method provided by the application can realize mechanical combination and metallurgical combination, and has high strength, fatigue resistance and electrical conductivity; in the application, the interlocking amount depends on the macro shape of the lower layer plate rather than the thickness direction deformation difference, so the interlocking amount is large, and the high strength of the joint is ensured.

[0019] (5) The upper layer plate is plastically formed at high strain rate under the force effect of laser impact wave rather than the thermal effect, and the welding formed by high-speed impact and shearing of the upper inclined surface of the through hole of the upper layer plate and the lower layer plate also only occurs at the moment and the surface layer of the plate, so there is no problem of heat affected zone.

[0020] (6) The method provided by the application can realize synchronous completion of riveting and welding of the plate under the action of laser pulse, and has simple process and high processing efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0021] The drawings accompanying the specification of the application form a part of the application and serve to further provide a further understanding of the application, the illustrative embodiments of the application and the explanations thereof serve to explain the application, and do not constitute an improper limitation of the application.

[0022] Figure 1 It is a schematic diagram of the flat hole connection device of pulse laser impact in the application;

[0023] Figure 2 It is a schematic diagram of the hourglass-shaped through hole of the lower layer plate in the application;

[0024] Figure 3 It is a schematic diagram of the intermediate process of the flat hole connection of pulse laser impact in the application;

[0025] Figure 4 It is a schematic diagram of the final completion of the flat hole connection of pulse laser impact in the application;

[0026] Figure 5 It is a schematic diagram of the final connection of the flat hole connection of pulse laser impact in the application, a is a schematic diagram of the final connection of the plate with large thickness difference, and b is a schematic diagram of the final connection of the plate with large thickness.

[0027] Wherein, 1 is a laser, 2 is a workpiece clamping system, 3 is a constraint layer, 4 is an absorbing layer, 5 is an upper layer plate, 6 is a lower layer plate with a sandglass-shaped through hole, 7 is a bottom die, and 8 is a workbench. DETAILED DESCRIPTION

[0028] In a first typical embodiment of the present application, a method for connecting a flat hole by pulsed laser impact is provided, the method comprising:

[0029] The bottom die, the lower layer plate with a sandglass-shaped through hole, the upper layer plate, the absorbing layer and the constraint layer are sequentially stacked from bottom to top, and each layer is clamped and fixed on the workbench by the workpiece clamping system; the sandglass-shaped through hole region is placed at the center of the pulsed laser spot, and under the pressure of the pulsed laser impact wave, the upper layer plate is subjected to high strain rate plastic deformation and impacts the upper inclined surface of the sandglass-shaped through hole of the lower layer plate to generate high-speed shear deformation, thereby generating a metallurgical welding effect; as the deformation of the upper layer plate continues, when the upper layer plate flows into the cavity of the sandglass-shaped through hole of the lower layer plate, an interlocking structure with a small upper part and a large lower part is formed between the upper inclined surface of the sandglass-shaped through hole of the lower layer plate, thereby generating a mechanical riveting effect; and a riveting and welding composite connection of a flat hole, upper welding and lower riveting is completed.

[0030] In one or more embodiments, the bottom die is used to limit the deformation of the upper layer plate to form a flat hole riveting and welding joint.

[0031] In one or more embodiments, the upper layer plate is a flat plate.

[0032] In one or more embodiments, the upper inclined surface of the sandglass-shaped through hole of the lower layer plate is a welding inclined surface; and the lower inclined surface of the sandglass-shaped through hole of the lower layer plate is a riveting inclined surface.

[0033] In one or more embodiments, the included angle (acute angle) α between the upper inclined surface of the sandglass-shaped through hole and the upper surface (horizontal plane) of the lower layer plate is in the range of 20-60°; the included angle (acute angle) β between the lower inclined surface of the sandglass-shaped through hole and the lower surface (horizontal plane) of the lower layer plate is in the range of 20-60°; and the angle of the included angle α is greater than the angle of the included angle β.

[0034] In one or more embodiments, the horizontal length of the upper inclined surface of the sandglass-shaped through hole of the lower layer plate and the horizontal length of the lower inclined surface of the sandglass-shaped through hole of the lower layer plate are respectively x α and x β , the diameter of the upper opening is D, the thickness of the lower layer plate is H, and the vertical height of the lower inclined surface is h, wherein x α ≥ x β ; the diameter d of the transition between the upper inclined surface and the lower inclined surface is D-2×x α , and d≥2×x β ; and h≤ The space at the upper inclined surface of the lower layer plate hourglass-shaped through hole ensures the welding effect and is beneficial to material flow. Different parameter combinations of the lower layer plate hourglass-shaped through hole can obtain composite joints with different properties and application scenarios.

[0035] In one or more embodiments, the hourglass-shaped through hole in the lower layer plate with the hourglass-shaped through hole can be drilled on both sides of the plate by a drill bit, or can be achieved by laser drilling, which has a natural taper and can drill holes on hard and brittle materials.

[0036] In one or more embodiments, to ensure synchronous welding and riveting effect, the thickness H of the lower layer plate is not less than 0.1 mm.

[0037] In one or more embodiments, the upper layer plate and the lower layer plate can be homogeneous plates or heterogeneous plates of copper, aluminum, steel, titanium, etc.

[0038] In one or more embodiments, the absorbing layer is black paint, graphite or metal foil; laser irradiation on the absorbing layer generates high temperature and high pressure plasma in a very short time, continues to absorb energy to form a laser shock wave, thereby serving as a driving force to push the plate to high strain rate plastic deformation; In addition, the absorbing layer also has the effect of protecting the material surface from laser burns.

[0039] In one or more embodiments, the constraint layer is glass or water, which aims to limit the expansion of the plasma, thereby increasing the peak pressure of the shock wave and prolonging the action time; At the same time, the constraint layer makes the shock wave propagate towards the plate.

[0040] In one or more embodiments, the power density of the pulsed laser should be greater than 1 GW / cm 2 The specific value depends on the laser energy, laser spot size and pulse width of the laser.

[0041] Further, in order to enable the upper and lower plates to complete riveting and welding under the action of laser once, the pulse width of the laser should be not more than 20 ns.

[0042] Further, in order to obtain approximately flat-top distributed laser energy, the laser spot size should be not less than 1.5 times the maximum opening diameter D of the lower layer plate hourglass-shaped through hole.

[0043] Further, by adjusting the laser energy, laser spot size and pulse width of the laser, riveting and welding joints of different material combinations, thickness combinations and size specifications can be achieved.

[0044] A second typical embodiment of the present invention provides an apparatus for implementing the above method, the apparatus comprising: a bottom mold, a lower plate with an hourglass-shaped through hole, an upper plate, an absorption layer and a constraint layer stacked from bottom to top, and using a workpiece clamping system to clamp and fix each stacked layer on a worktable.

[0045] The device also includes a laser for generating pulsed laser light.

[0046] In one or more embodiments, the worktable is used to adjust the impact position.

[0047] A third typical embodiment of the present invention provides the above method or the apparatus for implementing the above method for synchronously riveting and welding plates with a large thickness or plates with a large difference in thickness.

[0048] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0049] Example 1: The thickness difference between the upper and lower layers of the substrate is significant.

[0050] like Figure 5 As shown in Figure (a), the upper plate is a 0.05 mm thick pure copper plate, and the lower plate is a 0.15 mm thick aluminum alloy plate. The dimensions of the hourglass-shaped through-hole are designed as follows: D = 0.35 mm, α = β = 45°, h = 0.075 mm, H = 0.15 mm, x α =x β =0.075mm, d=0.2 mm. The laser pulse width is 12 ns, the laser spot diameter is 2 mm, and the laser energy is 5 J. The hourglass-shaped through-hole area is placed at the center of the pulsed laser spot. Under the pressure of the pulsed laser shock wave, the upper plate undergoes high strain rate plastic deformation downward, impacting the upper inclined surface of the hourglass-shaped through-hole in the lower plate, resulting in high-speed shear deformation and thus producing a metallurgical welding effect. As the upper plate continues to deform, when it flows into the cavity of the hourglass-shaped through-hole in the lower plate, it forms an interlocking structure with the lower inclined surface of the hourglass-shaped through-hole in the lower plate, resulting in a mechanical riveting effect. This completes the flat hole-shaped, upper welded and lower riveted composite connection.

[0051] Example 2

[0052] like Figure 5 As shown in (b), the upper plate is a 0.20 mm thick pure copper plate, and the lower plate is a 0.20 mm thick aluminum alloy plate. The dimensions of the hourglass-shaped through hole are designed as follows: D = 0.7 mm, α = β = 45°, h = 0.10 mm, H = 0.20 mm, x α =x β=0.10 mm, d=0.5 mm. The pulse width of the laser is 12 ns, the laser spot diameter is 2 mm, and the laser energy is 10 J. The sandglass-shaped hole region is placed at the center of the pulsed laser spot, and under the pressure of the pulsed laser shock wave, the upper plate deforms plastically at a high strain rate and impacts the upper inclined surface of the sandglass-shaped hole of the lower plate, thereby producing a high-speed shear deformation and a metallurgical welding effect; as the deformation of the upper plate continues, when the upper plate flows into the cavity of the sandglass-shaped hole of the lower plate, an interlocking structure with a small upper bottom and a large lower bottom is formed with the lower inclined surface of the sandglass-shaped hole of the lower plate, thereby producing a mechanical riveting effect; and a rivet-weld composite connection with a flat hole, upper welding and lower riveting is completed.

[0053] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of hole connection by pulsed laser impact, characterized in that, The method comprises: From bottom to top, the bottom die, the lower layer plate with sand hour-shaped through hole, the upper layer plate, the absorption layer and the constraint layer are placed in sequence, and each layer is clamped and fixed on the workbench by using a workpiece clamping system; the sand hour-shaped through hole area is placed at the center of the pulsed laser spot, under the pressure of the pulsed laser shock wave, the upper layer plate occurs high strain rate plastic deformation downward, impacts the upper inclined surface of the sand hour-shaped through hole of the lower layer plate, and high-speed shear deformation occurs, so that the metallurgical welding effect is generated; with the continuous deformation of the upper layer plate, when the upper layer plate flows into the cavity of the sand hour-shaped through hole of the lower layer plate, the lower inclined surface of the sand hour-shaped through hole of the lower layer plate forms an upper-small-bottom-large interlocking structure, so that the mechanical riveting effect is generated; the riveting and welding composite connection of the flat hole, the upper welding and the lower riveting is completed.

2. The method of joining as defined in claim 1, wherein, The bottom die is used to limit the deformation of the upper layer plate, and form a flat hole riveting and welding joint.

3. The method of joining as defined in claim 1, wherein, The upper inclined surface of the sand hour-shaped through hole of the lower layer plate is a welding inclined surface; and the lower inclined surface of the sand hour-shaped through hole of the lower layer plate is a riveting inclined surface. Or, the included angle α between the upper inclined surface of the sand hour-shaped through hole and the upper surface of the lower layer plate is in the range of 20-60°; the included angle β between the lower inclined surface of the sand hour-shaped through hole and the lower surface of the lower layer plate is in the range of 20-60°; and the angle of the included angle α is greater than the angle of the included angle β. Or, the horizontal length of the upper inclined surface of the lower layer plate hourglass-shaped hole and the lower inclined surface of the lower layer plate hourglass-shaped hole is x α and x β , the upper hole diameter is D, the thickness of the lower layer plate is H, the vertical height of the lower inclined surface is h, wherein x α ≥x β ; the hole diameter d at the transition of the upper inclined surface and the lower inclined surface is D-2x α , and d≥2x β ; h≤ ; the space at the upper inclined surface of the larger lower layer plate hourglass-shaped hole ensures the welding effect and is conducive to material flow; different parameter combinations of the lower layer plate hourglass-shaped hole can obtain composite joints with different properties and application scenarios.

4. The method of joining as defined in claim 3, wherein, The thickness H of the lower layer plate is not less than 0.1 mm.

5. The method of joining as defined in claim 1 wherein, The upper layer plate and the lower layer plate can be copper, aluminum, steel, titanium homogenous plate or heterogeneous plate. Or, the absorption layer is black paint, graphite or metal foil. Or, the constraint layer is glass or water.

6. The method of joining as defined in claim 1, wherein, The power density of the pulsed laser should be greater than 1 GW / cm 2 .

7. The method of joining as defined in claim 6, wherein, The pulse width of the pulsed laser should be not greater than 20 ns. Or, the laser spot size should be not less than 1.5 times of the maximum opening diameter D of the sand hour-shaped through hole of the lower layer plate.

8. An apparatus capable of implementing the connection method according to any one of claims 1 to 7, characterized in that, The device comprises: a bottom die, a lower layer plate with a sand hour-shaped through hole, an upper layer plate, an absorption layer and a constraint layer placed in sequence from bottom to top, and each layer is clamped and fixed on the workbench by using a workpiece clamping system; The device further comprises a laser for generating pulsed laser.

9. The apparatus of claim 8, wherein, The workbench is used for adjusting the impact position.

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