A plastic forming method and device with adjustable local impact load field

Abstract

The application belongs to the field of material forming, and specifically discloses a plastic forming method and device with adjustable local impact load field; the method comprises the following steps: placing a base material on a concave die with a target forming feature cavity and clamping the base material with a blank holder, placing the device in a liquid chamber and injecting a liquid medium to cover the upper surface of the base material; setting positive and negative electrodes above the base material in the liquid chamber and applying a preset voltage lower than the breakdown threshold of the liquid medium; shaping a laser beam into a preset spatial form by a laser shaping device, focusing the laser beam to be incident into the liquid medium between the electrodes, and inducing an initial plasma channel; the plasma channel triggers the preset high-voltage electric energy between the electrodes to occur pulse discharge along the channel, and generates an impact wave matched with the plasma channel form and energy distribution; the impact wave drives the base material to occur high-strain-rate plastic deformation, and accurately fills the cavity in the concave die. The application can realize active regulation of the three-dimensional spatial distribution of the impact load field, and improve the deformation uniformity and mold filling accuracy.

Description

Technical Field

[0001] This application belongs to the field of materials forming technology, and more specifically, relates to a plastic forming method and apparatus with adjustable local impact load field. Background Technology

[0002] Complex metallic structural components (such as microchannel bipolar plates for proton exchange membrane fuel cells and microchannel heat exchangers) are core functional parts in the fields of new energy, biomedicine, and high-end equipment. Their forming accuracy, surface quality, and structural consistency directly determine the performance and service life of the equipment. These parts often have complex microstructural features (such as microchannels and microgrooves), making them prone to problems such as cracking, excessive springback, and insufficient filling during the forming process. High strain rate impact forming technologies (such as explosive forming, electromagnetic forming, laser shock forming, laser cavitation impact forming, and electro-hydraulic forming) have attracted much attention due to their significant plasticizing effect. However, existing impact forming technologies have fixed load patterns, and the impact load field is difficult to control as needed. This leads to a geometric mismatch between the impact pressure field and complex forming features (such as curved channels, irregular grooves, and asymmetric structures), resulting in uneven deformation, local overload cracking, or insufficient filling. Therefore, there is an urgent need to develop a novel impact forming method that can actively control the spatial morphology of the impact load field. Summary of the Invention

[0003] In response to the deficiencies or improvement needs of existing technologies, this application provides a plastic forming method and apparatus with adjustable local impact load field. It aims to solve the problem of mismatch between load field and complex forming structure caused by fixed impact source shape in existing technologies, and achieve a high degree of adaptation between the three-dimensional spatial shape of impact load field and complex target component structure, thereby improving forming quality and accuracy.

[0004] The above-mentioned technical objectives of this application are mainly achieved through the following technical solutions.

[0005] On the one hand, this application provides a plastic forming method with adjustable local impact load field, which includes the following steps: Step S10: Provide a die with a cavity for forming the target features, place the substrate to be formed on the die, and clamp the edges using a pressing device.

[0006] Step S20: Place the die and the substrate in the liquid chamber, and make the liquid medium in the liquid chamber completely cover the upper surface of the substrate.

[0007] Step S30: At least one pair of positive and negative electrodes connected to a high-voltage pulse power supply are disposed above the substrate in the liquid chamber, and a preset voltage lower than the breakdown threshold of the liquid medium is applied to the positive and negative electrodes.

[0008] Step S40: The laser beam is shaped into a preset spatial shape by a laser shaping device, and the shaped laser beam is focused and incident on the liquid medium between the positive and negative electrodes to induce the generation of an initial plasma channel with a preset shape and energy density distribution. The initial plasma channel triggers a preset high voltage between the positive and negative electrodes to generate a pulse discharge along the initial plasma channel, thereby generating a shock wave that matches the shape of the initial plasma channel. The shock wave drives the substrate to undergo high strain rate plastic deformation to fill the cavity of the mold.

[0009] Step S50: Demolding to obtain a component with the desired shaped form.

[0010] This application uses a laser shaping device to shape a laser beam into a spatial form that matches the geometry of the cavity of the target forming feature. This induces the generation of an initial plasma channel with a corresponding shape and energy density distribution in a liquid medium. This channel serves as a preferential discharge path, triggering high-voltage pulsed electrical energy to pulse and discharge along the channel, generating a shock wave that matches the shape and energy distribution of the plasma channel. This enables active control of the three-dimensional spatial distribution of the impact load field, allowing the shock wave pressure field to be highly adapted to the complex forming feature, significantly improving deformation uniformity and filling accuracy.

[0011] In a preferred embodiment of this application, step S40 further includes real-time monitoring of the shock wave pressure distribution using a shock wave pressure acquisition system and a camera, and feeding the monitoring data back to a computer control system. The computer control system compares the detected actual pressure distribution with the ideal spatial shock wave pressure field distribution. If the deviation exceeds a preset threshold, the preset voltage in step S30 and / or the energy parameters of the laser beam in step S40 are adjusted to match the shock wave pressure field with the target forming feature. This closed-loop feedback control mechanism can optimize the shock wave pressure field distribution in real time, ensuring the stability and consistency of the forming quality.

[0012] In a preferred embodiment of this application, the ideal spatial shock wave pressure field distribution is calculated using geometric parameters at coordinates within the cavity, including parameters such as the bidirectional stress state coefficient, the dynamic flow stress of the substrate, the thickness of the substrate, the two principal radii of curvature at coordinates within the cavity, and inertial forces. Specifically, the ideal spatial shock wave pressure field distribution satisfies the following function: ; in, The ideal local peak pressure required to force the substrate to fully adhere to the mold at coordinates (x, y) within the cavity; It is the bidirectional stress state coefficient; The dynamic flow stress of the substrate at coordinates (x, y) within the cavity; Let be the thickness of the substrate at coordinates (x, y) within the cavity; and These are the two principal radii of curvature at coordinates (x, y) within the cavity; Let be the inertial force of the substrate at coordinates (x, y) within the cavity.

[0013] The aforementioned ideal spatial shock wave pressure field distribution provides a clear target reference for the closed-loop control system, enabling the shock wave pressure field to accurately match the local geometric requirements of complex forming features.

[0014] In a preferred embodiment of this application, the laser shaping device shapes the laser beam into a preset spatial shape using a preset phase function. This phase function is calculated through inverse Fourier transform and the focal plane approximation phase, and involves parameters such as the phase angle at the cavity coordinates, the target light intensity at the laser spot, the focal plane approximation phase, and the position coordinates on the focal plane. Specifically, the phase function of the laser shaping device is: ; in, Let be the phase angle at coordinates (x, y) within the cavity; This indicates the phase angle for extracting complex numbers; Indicates the inverse Fourier transform; Let be the target light intensity at coordinates (u, v) on the focal plane; It represents the approximate phase at coordinates (u, v) on the focal plane.

[0015] The aforementioned phase function design method establishes a mapping relationship from the geometry of the target forming feature cavity to the spatial distribution of the laser, providing a theoretical basis and technical means for the active control of the impact load field.

[0016] In a preferred embodiment of this application, the substrate to be formed is a metal foil, a non-metal foil, a composite sheet, or a sheet; the metal foil includes metals such as stainless steel, titanium alloy, aluminum alloy, or copper. The preparation method of this application is applicable to various material systems, and the dynamic flow stress and forming performance of different materials can be adapted by adjusting the preset voltage and the energy parameters of the laser beam.

[0017] In a preferred embodiment of this application, the liquid medium is a suitable insulating liquid medium such as deionized water or silicone oil. The selection of the liquid medium must meet the insulation performance requirements to ensure the stability and controllability of the laser-induced optical breakdown and high-voltage pulse discharge process.

[0018] In a preferred embodiment of this application, the laser shaping device is a diffractive optical element, a spatial light modulator, a microlens array, or other elements capable of adjusting the spatial distribution of the laser beam. These devices can all achieve precise control of the spatial shape of the laser beam. Among them, the spatial light modulator has the advantage of being dynamically adjustable, and can be adapted to different shaping features without changing the physical components.

[0019] In a preferred embodiment of this application, the geometry of the initial plasma channel can be adjusted by the laser shaping device to be a straight line, serpentine, wavy, ring-shaped, or any two-dimensional / three-dimensional shape, and the energy density and spatial distribution of the laser beam can be controlled to regulate the geometric accuracy and energy deposition density distribution of the initial plasma channel, adapting to target forming features of different shapes. This flexible shape control capability is a key technical feature for realizing active control of the impact load field.

[0020] In a preferred embodiment of this application, the shock wave in step S40 is a single impact or a multiple cyclic impact; when it is a multiple cyclic impact, step S40 is repeated before each discharge to accumulate plastic deformation. The multiple cyclic impact method is suitable for forming features with large depth or complex shape, and can achieve a greater forming depth while avoiding single overload fracture.

[0021] On the other hand, this application also provides a plastic forming apparatus with adjustable local impact load field for implementing the above method, comprising: a liquid chamber for containing a liquid medium; a die, the upper surface of which is provided with a cavity including a target forming feature and an vent hole; a pressing device for fixing a substrate to be formed onto the die; a power supply unit, the power supply unit including a high-voltage pulse power supply and at least one pair of positive and negative electrodes electrically connected to the high-voltage pulse power supply, the positive and negative electrodes being disposed opposite each other in the liquid chamber and above the substrate; and a laser unit for shaping a laser beam into a preset shape and incident it onto the positive and negative electrodes. In the liquid medium between the electrodes; a monitoring unit, the monitoring unit including a camera and a shock wave pressure acquisition system, the camera being used to capture the plasma channel and shock wave shape, the shock wave pressure acquisition system being used to acquire and process the evolution and distribution of shock wave pressure magnitude; a control unit, the control unit being electrically connected to the power supply unit, the laser unit and the monitoring unit, the control unit being configured to adjust the preset voltage of the power supply unit and / or the energy parameters of the laser beam based on the comparison results of the actual acquired shock wave pressure distribution and the ideal spatial shock wave pressure field distribution, so as to match the shock wave pressure field with the target forming characteristics.

[0022] In a preferred embodiment of this application, the laser unit includes a laser for generating a laser beam; a reflector for adjusting the direction of the laser beam; a laser shaping device for shaping the laser beam into a preset shape; and a focusing lens for focusing the shaped laser beam into the liquid medium between the positive and negative electrodes, thus providing a flexible technical means for the active control of the impact load field.

[0023] In a preferred embodiment of this application, the liquid chamber is connected to a storage tank via an inlet pipe and an outlet pipe. The storage tank stores the liquid medium. A pressure pump is installed on the inlet pipe, and a drain valve is installed on the outlet pipe, thereby realizing the recycling and precise control of the liquid medium.

[0024] In summary, compared with the prior art, the technical solutions conceived in this application mainly possess the following technical features and advantages: 1. This application combines the precise shape control capability of laser with the high energy and efficiency advantages of electro-hydraulic effect. By using a laser shaping device, the laser beam is shaped into a spatial form that matches the geometry of the target forming feature cavity. An initial plasma channel with a corresponding shape and energy density distribution is induced in the liquid medium. This channel triggers a high-voltage pulse discharge to generate an adjustable shock wave that matches the channel shape, thereby realizing the active control of the three-dimensional spatial distribution of the impact load field. This solves the technical problem of fixed shock wave shape and mismatch with complex geometric components in existing impact forming technology, and significantly improves the deformation uniformity and filling accuracy of complex structures.

[0025] 2. The forming method of this application is a non-contact forming method, which avoids damage to the substrate surface caused by the rigid die and ensures the surface quality of the formed part. High strain rate loading can effectively stimulate the inertial effect and multiple slip systems of the material, suppress necking and cracking, improve the forming limit, reduce springback, and obtain metal components with high surface quality and excellent mechanical properties. Compared with traditional quasi-static forming methods, the forming method of this application has significant advantages in forming limit, surface quality and dimensional accuracy, and is particularly suitable for the precision plastic forming of ultra-thin metal foils.

[0026] 3. The forming method of this application can flexibly change the shape of the initial plasma channel by replacing the laser shaping device or adjusting the laser parameters, thereby quickly adapting to forming features of different shapes and greatly improving the adaptability and flexibility of the process. Compared with traditional forming methods that require the design and manufacture of special dies for different products, the forming method of this application only requires replacing or adjusting the laser shaping device to achieve product switching, significantly reducing die cost and production preparation time, and is particularly suitable for multi-variety, small-batch production modes. Attached Figure Description

[0027] Figure 1 This is a flowchart of the steps of the plastic forming method with adjustable local impact load field described in this application; Figure 2 This is a schematic diagram of the structure of the plastic forming device with adjustable local impact load field described in this application; Figure 3 This is a partial side view illustrating the process of forming a corrugated microchannel structure provided in the embodiments of this application; Figure 4 This is a partial top view illustrating the process of forming a corrugated microchannel structure provided in the embodiments of this application; Figure 5 A schematic diagram of the initial plasma channel with a corrugated shape; Figure 6 This is a three-dimensional outline diagram of the corrugated microchannel structure after it has been formed.

[0028] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1. Substrate; 101. Substrate forming structure; 2. Die; 201. Cavity; 202. Vent hole; 3. Edge pressing device; 4. Liquid chamber; 5. Liquid medium; 6. Quartz glass cover plate; 7. Positive electrode; 8. Negative electrode; 9. Plasma channel; 10. Shock wave; 11. Working platform; 12. Liquid storage tank; 13. Drain valve; 14. Pressure pump; 15. High-voltage pulse power supply; 16. Lighting system; 17. Shock wave pressure acquisition system; 18. Focusing lens; 19. Laser shaping device; 20. Laser beam; 21. Reflector; 22. Laser; 23. Computer; 24. Camera. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0030] Implementation Method 1: This application provides a plastic forming apparatus with adjustable local impact load field, which is used to prepare metal microchannel structures, metal microstructure arrays, complex curved surface metal thin-walled parts, or precision metal irregular parts. Figure 2 As shown, the plastic forming device includes a liquid chamber 4, a die 2, a pressing device 3, a power supply unit, a laser unit, a monitoring unit, a control unit, and a liquid circuit system. Each part will be described in detail below.

[0031] Liquid chamber 4 is used to contain liquid medium 5. Liquid chamber 4 is equipped with a light-transmitting window or adopts a fully transparent structure, and is covered with a quartz glass cover plate 6 on top, so that the laser beam 20 can pass through the quartz glass cover plate 6 into the interior of liquid chamber 4, ensuring that the laser beam 20 can be smoothly incident into liquid medium 5. Preferably, liquid medium 5 is a suitable insulating liquid medium such as deionized water or silicone oil. The selection of liquid medium 5 must meet the insulation performance requirements to ensure the stability and controllability of laser-induced optical breakdown and high-voltage pulse discharge processes.

[0032] The upper surface of the die 2 is provided with a cavity 201 including the target forming features and an exhaust hole 202. The exhaust hole 202 is used to discharge the gas in the cavity 201 during the forming process, so as to avoid the gas from hindering the filling of the substrate 1 and ensure that the substrate 1 can completely fit the cavity 201.

[0033] The edge-pressing device 3 is used to fix the substrate 1 to be formed on the die 2 and clamp the edge of the substrate 1 to prevent the substrate 1 from shifting during the forming process. Preferably, the substrate 1 to be formed is a metal foil, a non-metal foil, a composite material sheet or plate; the material of the metal foil can be stainless steel, titanium alloy, aluminum alloy or copper, etc.

[0034] The power supply unit includes a high-voltage pulse power supply 15 and at least one pair of positive and negative electrodes, including a positive electrode 7 and a negative electrode 8. The high-voltage pulse power supply 15 is electrically connected to the positive electrode 7 and the negative electrode 8 and is used to apply a preset voltage to the electrodes. The positive electrode 7 and the negative electrode 8 are disposed opposite each other in the liquid chamber 4 and above the substrate 1. The liquid medium 5 in the liquid chamber 4 submerges the positive electrode 7 and the negative electrode 8, forming a discharge gap between the two electrodes. The discharge gap region is directly above the target forming feature cavity 201.

[0035] The laser unit is used to shape the laser beam 20 into a preset shape and incident it into the liquid medium 5 between the positive and negative electrodes. It includes a laser 22, a reflector 21, a laser shaping device 19, and a focusing lens 18. The laser 22 is used to generate the laser beam 20; the reflector 21 is used to adjust the propagation direction of the laser beam 20; the laser shaping device 19 is disposed in the output optical path of the laser 22 and is used to shape the laser beam 20 into a preset spatial shape. The laser shaping device 19 can be a diffractive optical element (DOE), a spatial light modulator (SLM), or a microlens array; the focusing lens 18 is used to focus the shaped laser beam 20 into the liquid medium 5 between the positive electrode 7 and the negative electrode 8.

[0036] The monitoring unit includes a camera 24 and a shock wave pressure acquisition system 17. The camera 24 works in conjunction with the illumination system 16 to capture the shape and evolution of the plasma channel 9 and the shock wave 10; the shock wave pressure acquisition system 17 is used to acquire and process the pressure magnitude evolution and distribution of the shock wave 10.

[0037] The control unit is a computer 23, which is electrically connected to the power supply unit, the laser unit and the monitoring unit. The control unit is configured to adjust the preset voltage of the power supply unit and / or the energy parameters of the laser beam 20 based on the comparison results between the shock wave pressure distribution actually collected by the shock wave pressure acquisition system 17 and the ideal space shock wave pressure field distribution, so as to match the shock wave pressure field with the target forming features.

[0038] The liquid circuit system includes a storage tank 12, a pressure pump 14, and a drain valve 13. The liquid chamber 4 is connected to the storage tank 12 via an inlet pipe, on which the pressure pump 14 is installed to input the liquid medium 5 from the storage tank 12 into the liquid chamber 4. The liquid chamber 4 is also connected to the storage tank 12 via an outlet pipe, on which the drain valve 13 is installed to discharge the liquid medium 5 from the liquid chamber 4, thereby realizing the recycling and precise control of the liquid medium 5.

[0039] Furthermore, the plastic forming device also includes a working platform 11, which is used to support the entire forming device. The die 2, the liquid chamber 4, and the pressing device 3 are all installed on the working platform 11.

[0040] Implementation Method Two: This application also provides a plastic forming method with adjustable local impact load field. The method uses a laser shaping device to shape the laser beam 20 into a corrugated distribution, induces the generation of corrugated plasma channels in the liquid medium 5, triggers high-voltage pulse discharge to generate corrugated shock waves, and drives the substrate 1 to fill the corrugated cavity 201.

[0041] The following detailed description of the plastic forming method of this application, using the plastic forming apparatus provided in Embodiment 1 as an example, illustrates the forming of a corrugated microchannel structure from 0.1 mm thick TC4 titanium foil. Figures 1 to 4 As shown, the specific steps are as follows: Step S10: Select 0.1mm thick TC4 titanium foil as substrate 1, design and process a cavity 201 with the same shape as the target corrugated microchannel, cover the substrate 1 (TC4 titanium foil) on the cavity 2, and fix it with the edge clamping device 3 to clamp the edge.

[0042] Step S20: Place the die 2 and the substrate 1 into the liquid chamber 4, start the pressure pump 14, and inject deionized water (liquid medium 5) from the storage tank 12 into the liquid chamber 4 through the inlet pipe to ensure that the upper surface of the substrate 1 is completely immersed in the deionized water. Cover the liquid chamber 4 with a quartz glass cover plate 6 so that the laser beam 20 can pass through and enter the interior of the liquid chamber 4.

[0043] Step S30: A pair of parallel plate electrodes are placed above the substrate 1 in the liquid chamber 4, and the parallel plate electrodes are placed in deionized water. The parallel plate electrodes include a positive electrode 7 and a negative electrode 8, with a gap of 18 mm between the two electrodes. The discharge gap area is directly above the corrugated microfluidic cavity 201. The high-voltage pulse power supply 15 is activated to apply a preset voltage to the positive electrode 7 and the negative electrode 8. Experimentally, the breakdown voltage of deionized water under the conditions of this embodiment is approximately 30 kV. Therefore, the preset voltage is set to 26 kV, which is approximately 87% of the breakdown voltage, to ensure that the electrodes are in a pre-charged state and do not spontaneously discharge.

[0044] Step S40: Based on the geometry of the target corrugated microchannel, a diffractive optical element (DOE) with a corresponding phase modulation pattern is customized as a laser shaping device 19. The laser 22 emits a laser beam 20, which, after its propagation direction is adjusted by the reflector 21, is shaped by the laser shaping device 19 to obtain a laser beam 20 with a spatially corrugated distribution. The shaped laser beam 20 is focused by the focusing lens 18 and precisely incident into the deionized water between the positive electrode 7 and the negative electrode 8, inducing the generation of an initial plasma channel 9 with a corrugated shape and a corresponding energy density distribution.

[0045] like Figure 4 As shown, the initial plasma channel 9 has a corrugated distribution, and its shape matches the geometry of the target corrugated microchannel cavity 201, serving as a preferential discharge path and reducing the discharge impedance along the channel direction. The initial plasma channel 9 triggers a pulsed discharge of the pre-set high-voltage electrical energy between the positive electrode 7 and the negative electrode 8 along the channel, generating an electro-hydraulic effect and releasing a corrugated shock wave 10 that matches the shape of the initial plasma channel 9. Figure 3 As shown, the shock wave 10 drives the substrate 1 (TC4 titanium foil) to undergo high strain rate plastic deformation, so that the substrate fits tightly into the corrugated cavity 201 of the die 2, and the vent 202 simultaneously discharges the gas in the cavity 201 to avoid the gas from hindering the filling of the substrate 1.

[0046] Furthermore, the laser shaping device 19 shapes the laser beam 20 into a preset spatial shape using a preset phase function. This phase function is calculated through inverse Fourier transform and focal plane approximation phase, involving parameters such as the phase angle at the cavity coordinates, the target light intensity at the laser spot, the focal plane approximation phase, and the position coordinates on the focal plane. This phase function design method establishes a mapping relationship from the target forming feature cavity geometry to the laser spatial distribution, providing a theoretical basis and technical means for the active control of the impact load field.

[0047] Specifically, the phase function of the laser shaping device 19 is: (1); In formula (1), Let be the phase angle at coordinates (x, y) within the cavity; This represents the phase angle for extracting complex numbers; Indicates the inverse Fourier transform; Let be the target light intensity at coordinates (u, v) on the focal plane; It represents the approximate phase at coordinates (u, v) on the focal plane.

[0048] The specific expression is: (2); In formula (2), This is the geometric scaling factor for the focusing system; The laser pulse width; Optical breakdown efficiency (the ratio of laser energy to plasma energy); The specific expression for the energy deposition density distribution in the plasma channel is as follows: (3); In formula (3), , The coefficients calibrated through experiments ( Usually, 1 to 2 are taken); This is the breakdown voltage of the liquid dielectric. Electrode voltage; The ideal spatial shock wave pressure field distribution can be calculated using formula (4) described below; The pressure attenuation coefficient of the liquid medium; This is the distance between the plasma channel and the upper surface of the substrate. This represents the characteristic lateral dimension of the plasma channel.

[0049] Preferably, during step S40, the pressure distribution of the shock wave 10 can be monitored in real time by the shock wave pressure acquisition system 17 and the camera 24, and the monitoring data can be fed back to the computer 23 (control unit). The computer 23 compares the actual pressure distribution with the ideal spatial shock wave pressure field distribution. If the deviation exceeds a preset threshold (e.g., the deviation exceeds 5%), the preset voltage (adjustment range ±2kV) and / or the energy parameters of the laser beam 20 (adjustment range ±10%) are automatically adjusted. After 2 to 3 iterative adjustments, the shock wave pressure field achieves optimal matching with the target forming features.

[0050] Furthermore, the ideal spatial shock wave pressure field distribution is calculated using geometric parameters at the coordinates within the cavity, involving parameters such as the bidirectional stress state coefficient, the dynamic flow stress of the substrate, the thickness of the substrate, the two principal radii of curvature at the coordinates within the cavity, and inertial forces. This ideal spatial shock wave pressure field distribution provides a clear target reference for the closed-loop control system, enabling the shock wave pressure field to accurately match the local geometric requirements of complex forming features.

[0051] Specifically, the ideal space shock wave pressure field distribution satisfies the following function: (4); In the above formula (4), The ideal local peak pressure required to force the substrate to fully adhere to the mold at coordinates (x, y) within the cavity; It is the bidirectional stress state coefficient; The dynamic flow stress of the substrate at coordinates (x, y) within the cavity; Let be the thickness of the substrate at coordinates (x, y) within the cavity; and These are the two principal radii of curvature at coordinates (x, y) within the cavity; The inertial force of the substrate at coordinates (x, y) within the cavity is expressed as follows: (5); In formula (5), The density of the substrate; This refers to the thickness distribution of the substrate, that is, the thickness of the substrate at coordinates (x, y) within the cavity; The base material is located at coordinates (x, y) within the cavity, and the deformation time is... Displacement along the lower normal direction; The deformation time of the substrate.

[0052] Step S50: Demolding to obtain a high-quality corrugated microchannel structure, namely substrate forming structure 101.

[0053] For forming features with significant depth or complex shapes, a multi-cycle impact method can be used. After the first impact completes the initial forming, the substrate 1 is kept on the die 2, and step S40 is repeated before each discharge to perform the second and third impacts, achieving cumulative plastic deformation. Experimental results show that using the multi-cycle impact method increases the final mold filling depth by more than 30% compared to a single impact, and effectively avoids the risk of breakage caused by a single overload.

[0054] To further illustrate the specific forming process of the plastic forming method with adjustable local impact load field of this application, a specific embodiment will be described below.

[0055] This embodiment uses a 0.1mm thick TC4 titanium foil as the substrate 1 and deionized water as the liquid medium to form a corrugated microfluidic structure as an example to describe in detail the plastic forming method with adjustable local impact load field of this application.

[0056] TC4 titanium foil was cut into 50mm × 50mm square specimens. Before the test, the titanium foil was ultrasonically cleaned in anhydrous ethanol for 5 minutes to remove surface oil and oxide layer, and then allowed to air dry at room temperature for later use.

[0057] Design and fabricate a Cr12MoV mold steel die cavity 2 (hardness HRC58~62 after quenching and tempering). The upper surface of the die cavity 2 is machined with a target corrugated microchannel cavity 201. The geometric parameters of cavity 201 are as follows: channel width... w =1.02mm, channel depth d =0.4mm, the corrugation shape satisfies the sine function y =1.0 sin(π (x / 8). The surface roughness Ra of the bottom and sidewall of cavity 201 is ≤0.3μm. A vent hole 202 with a diameter of 0.5mm is provided at the lowest point of cavity 201, and the vent hole 202 extends to the bottom surface of die 2.

[0058] Fix the die 2 onto the work platform 11, cover the die 2 with TC4 (substrate 1), and clamp the edge of the TC4 foil using the edge clamping device 3. Place the assembled die 2 and substrate 1 into the liquid chamber 4.

[0059] Start the pressure pump 14 to inject deionized water from the storage tank 12 into the liquid chamber 4 until the liquid level is 25mm above the upper surface of the substrate 1, and then cover it with the quartz glass cover plate 6.

[0060] A pair of parallel plate electrodes are disposed above the substrate 1 inside the liquid chamber 4. The parallel plate electrodes include a positive electrode 7 and a negative electrode 8. The distance between the two electrodes is 14 mm. According to calibration, the natural breakdown voltage of water at room temperature is about 30 kV at this distance. The center of the discharge gap region is directly above the corrugated microchannel cavity 201, and the lower end of the electrode is about 5 mm away from the upper surface of the substrate 1.

[0061] To ensure that the electrodes are in a pre-charged state and do not spontaneously discharge, while ensuring that the laser-induced plasma channel can reliably trigger discharge, the preset voltage is set to 85% of the breakdown voltage, i.e., 26kV.

[0062] A Nd:YAG pulsed laser 22 (wavelength 532nm, pulse width 8ns) was selected. The laser beam, after being shaped into a wavy spatial distribution by a DOE, was focused by a focusing lens 18 and incident on the deionized water between the positive electrode 7 and the negative electrode 8. In preliminary experiments, the plasma channel formation effect and trigger discharge success rate were tested at five energy levels: 50mJ, 80mJ, 110mJ, 140mJ, and 170mJ. The results are as follows: at 50mJ, the plasma channel was incomplete, and the trigger discharge success rate was only about 40%; at 80mJ, a complete plasma channel could be formed, with a trigger discharge success rate of about 88%; at 110mJ, the channel was clear and stable, and the trigger discharge success rate was greater than 98%; above 140mJ, the channel showed branching and disorder, which led to a decrease in the uniformity of the shock wave spatial distribution. Therefore, in this embodiment, a laser single pulse energy of 110mJ was selected.

[0063] Computer 23 calculates the ideal space shock wave pressure field distribution based on the geometric parameters of cavity 201 in mold 2. In this embodiment, the principal radius of curvature R1=6.48mm and R2=∞ at the crest of the corrugated microchannel cavity 201. The TC4 titanium foil is subjected to a strain rate of approximately 10... 4 s - Dynamic flow stress under ¹ σ dyn The strength is 880 MPa, and the foil thickness is... t 0 is 0.1 mm, and the bidirectional stress state coefficient λ is taken as 1.15. Inertial force term. P inertia Estimated by formula (5), under high strain rate forming conditions, the substrate density is taken as... ρ =4.43 g / cm³, deformation time approximately 25 μs, then P inertia The ideal local peak pressure at the crest of the corrugated flow channel is approximately 213 MPa. P ideal Approximately 340 MPa. In this embodiment, the ideal local peak pressure along the cavity flow channel direction is approximated as substantially uniform, approximately 340 MPa.

[0064] The high-voltage pulse power supply 15 is activated, applying a preset voltage of 26kV to the positive electrode 7 and the negative electrode 8. The control program of the computer 23 is triggered, and a laser trigger signal is emitted. The laser 22 emits a pulsed laser beam 20 (wavelength 532nm, pulse width 8ns, energy 110mJ), which, after its propagation direction is adjusted by the reflector 21, is shaped by a custom-designed diffractive optical element (DOE) as a laser shaping device 19. The phase pattern of this diffractive optical element is calculated and generated according to formula (1). After shaping, the laser induces optical breakdown in deionized water, forming a structure like... Figure 5The initial plasma channel 9 has a corrugated shape. Pre-set high-voltage electrical energy pulses along this channel, forming the main discharge and generating a violent electro-hydraulic effect within the channel. The shock wave 10 propagates rapidly through deionized water towards the substrate 1, acting on the upper surface of the TC4 titanium foil (substrate 1), driving the substrate 1 to undergo high strain rate plastic deformation to fill the corrugated cavity 201. The vent 202 simultaneously discharges the gas from the cavity 201, preventing gas from hindering the filling of the substrate 1.

[0065] After the discharge is complete, hold for 10 seconds and then open the drain valve 13 to drain the deionized water from the liquid chamber 4. Open the liquid chamber 4, remove the die 2 and the molded part, and perform a demolding operation to obtain the substrate molding structure 101.

[0066] The three-dimensional profile of the formed corrugated microchannel structure was measured using a laser confocal microscope. The measurement results are as follows: Figure 6 As shown, the forming depth is 366.4 μm.

[0067] The forming method described in this application is applicable to various substrate types. TC4 titanium foil can be replaced with 304 stainless steel foil (0.05 mm thick) or 1060 aluminum alloy foil (0.08 mm thick). By adjusting the preset voltage and the energy parameters of the laser beam 20 according to the dynamic flow stress and forming performance of different materials, microchannel structures can be successfully formed with good surface quality. Furthermore, the forming method described in this application is also applicable to non-metallic foils and composite material sheets or plates.

[0068] In addition to the diffractive optical element (DOE), the laser shaping device 19 in this application can also be replaced with a spatial light modulator (SLM). When using a spatial light modulator, the phase distribution of the SLM can be dynamically adjusted by the computer 23, which can realize real-time adjustment of the spatial shape of the laser beam. Different shapes can be quickly adapted without changing physical components, greatly improving process flexibility.

[0069] It should be understood that expressions such as "comprising" and "may include" as used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as "comprising" and / or "having" may be interpreted as indicating a specific characteristic, number, operation, constituent element, component, or combination thereof, but should not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0070] It should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0071] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0072] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0073] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for plastic forming with a locally adjustable impact load field, characterized in that, include: Step S10: Provide a die with a cavity for forming the target features, place the substrate to be formed on the die, and clamp the edges using a pressing device; Step S20: Place the die and the substrate in the liquid chamber, and make the liquid medium in the liquid chamber completely cover the upper surface of the substrate; Step S30: At least one pair of positive and negative electrodes connected to a high-voltage pulse power supply are disposed above the substrate in the liquid chamber, and a preset voltage lower than the breakdown threshold of the liquid medium is applied to the positive and negative electrodes; Step S40: The laser beam is shaped into a preset spatial shape by a laser shaping device, and the shaped laser beam is focused and incident into the liquid medium between the positive and negative electrodes, inducing the generation of an initial plasma channel with a preset shape and energy density distribution. The initial plasma channel triggers a preset high voltage between the positive and negative electrodes to generate a pulsed discharge along the initial plasma channel, thereby generating a shock wave that matches the shape of the initial plasma channel. The shock wave drives the substrate to undergo high strain rate plastic deformation to fill the cavity of the mold. Step S50: Demolding to obtain a component with the target shaped form; In step S40, the shock wave pressure distribution is monitored in real time by a shock wave pressure acquisition system and a camera, and the monitoring data is fed back to the computer control system. The computer control system compares the detected actual pressure distribution with the ideal spatial shock wave pressure field distribution. If the deviation exceeds a preset threshold, the preset voltage in step S30 and / or the energy parameters of the laser beam in step S40 are adjusted so that the shock wave pressure field matches the target forming feature.

2. The plastic forming method with adjustable local impact load field according to claim 1, characterized in that, The ideal spatial shock wave pressure field distribution satisfies the following function: ； in, The ideal local peak pressure required to force the substrate to fully adhere to the mold at coordinates (x, y) within the cavity; It is the bidirectional stress state coefficient; The dynamic flow stress of the substrate at coordinates (x, y) within the cavity; Let be the thickness of the substrate at coordinates (x, y) within the cavity; and These are the two principal radii of curvature at coordinates (x, y) within the cavity; Let be the inertial force of the substrate at coordinates (x, y) within the cavity.

3. The plastic forming method with adjustable local impact load field according to claim 1, characterized in that, The laser shaping device shapes the laser beam into a preset spatial shape using a preset phase function, wherein the phase function is: ； in, Let be the phase angle at coordinates (x, y) within the cavity; This represents the phase angle for extracting complex numbers; Indicates the inverse Fourier transform; Let be the target light intensity at coordinates (u, v) on the focal plane; It represents the approximate phase at coordinates (u, v) on the focal plane.

4. The plastic forming method with adjustable local impact load field according to claim 1, characterized in that, The substrate to be formed is a metal foil, a non-metal foil, a composite sheet or plate; the metal foil includes stainless steel, titanium alloy, aluminum alloy or copper; And / or, the liquid medium is deionized water or silicone oil.

5. The plastic forming method with adjustable local impact load field according to claim 1, characterized in that, The laser shaping device is a diffractive optical element, a spatial light modulator, or a microlens array. And / or, the geometry of the initial plasma channel can be adjusted by the laser shaping device to be straight, serpentine, corrugated, or ring-shaped.

6. The plastic forming method with adjustable local impact load field according to claim 1, characterized in that, The shock wave in step S40 is a single impact or multiple cyclic impacts. When it is a multiple cyclic impact, step S40 is repeated before each discharge to accumulate plastic deformation.

7. A plastic forming apparatus with adjustable local impact load field, used for implementing the plastic forming method with adjustable local impact load field according to any one of claims 1 to 6, characterized in that, The locally adjustable impact load field plastic forming device includes: Liquid chamber (4), the liquid chamber (4) is used to contain liquid medium (5); The upper surface of the die (2) is provided with a cavity (201) including the target forming features and an exhaust hole (202). The edge pressing device (3) is used to fix the substrate (1) to be formed onto the die (2); The power supply unit includes a high-voltage pulse power supply (15) and at least one pair of positive and negative electrodes electrically connected to the high-voltage pulse power supply (15). The positive and negative electrodes are disposed opposite to each other in the liquid chamber (4) and above the substrate (1). A laser unit is used to shape a laser beam (20) into a preset shape and incident it into the liquid medium (5) between the positive and negative electrodes; The monitoring unit includes a camera (24) and a shock wave pressure acquisition system (17). The camera (24) is used to capture the plasma channel and the shape of the shock wave, and the shock wave pressure acquisition system (17) is used to acquire and process the evolution and distribution of the shock wave pressure magnitude. The control unit is electrically connected to the power supply unit, the laser unit and the monitoring unit. The control unit is configured to adjust the preset voltage of the power supply unit and / or the energy parameters of the laser beam (20) based on the comparison results of the actual collected shock wave pressure distribution and the ideal space shock wave pressure field distribution, so as to match the shock wave pressure field with the target forming features.

8. The plastic forming apparatus with adjustable local impact load field according to claim 7, characterized in that, The laser unit includes: Laser (22), said laser (22) is used to generate laser beam (20); A reflector (21) is used to adjust the direction of the laser beam (20); A laser shaping device (19) is used to shape a laser beam (20) into a preset shape; A focusing lens (18) is used to focus the shaped laser beam (20) into the liquid medium (5) between the positive and negative electrodes.

9. The plastic forming apparatus with adjustable local impact load field according to claim 7, characterized in that, The liquid chamber (4) is connected to the storage tank (12) through the inlet pipe and the outlet pipe. The storage tank (12) stores the liquid medium (5). The inlet pipe is equipped with a pressure pump (14) and the outlet pipe is equipped with a drain valve (13).

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