Electric pulse-ultrasonic multi-field coupling auxiliary incremental forming device and method suitable for plate dieless forming

Abstract

The invention provides an electric pulse-ultrasonic multi-field coupling auxiliary incremental forming device and method suitable for plate dieless forming. The electric pulse-ultrasonic multi-field coupling auxiliary incremental forming device comprises a rotating device, an external fixing device and a test piece supporting device. The rotating device comprises a connection transition disc with a handle and a supporting shell, and the connection transition disc with the handle comprises a long handle and a disc; the long handle is connected with the driving device, and an insulating sleeve is arranged between the driving device and the long handle; first air inlet holes with the same diameter are evenly distributed in the disc in the radial direction, and the periphery of the first air inlet holes right faces the annular cavity of the air distribution ring. The supporting shell is located in the disc, the top of the supporting shell is connected with the disc, and a second air inlet communicated with the first air inlet is formed in the side wall of the supporting shell; an air outlet is formed in the middle of the supporting shell and connected with the silencer, the piezoelectric ceramic transducer is vertically fixed to the center of the disc, the amplitude-change pole with the disc is connected with the supporting shell in an interference fit mode so as to guarantee reliable connection, and the amplitude-change pole with the disc is connected with the forming tool head.

Description

Technical Field

[0001] This invention relates to the field of metal plastic forming and processing, and specifically to an electrical pulse-ultrasound multi-field coupling assisted progressive forming device and method suitable for moldless forming of sheet metal. Background Technology

[0002] Lightweight sheet materials such as magnesium alloys and titanium alloys have broad application prospects due to their high specific strength / stiffness, good heat dissipation, and noise and vibration reduction properties. However, magnesium alloys have a close-packed hexagonal crystal structure, resulting in few slip systems at room temperature, poor plasticity, and difficulty in processing. While increasing the slip system by raising the temperature can improve the formability of the sheet material, it also brings problems such as high production costs, poor product surface quality, and reduced mold life. Furthermore, traditional forming processes involve expensive and time-consuming mold manufacturing. Therefore, developing low-cost, high-quality flexible sheet material manufacturing processes, improving the formability of magnesium alloy sheets, and shortening the research and development cycle are of great significance for the development of lightweight structures.

[0003] High-energy pulsed current loading is a rapid non-equilibrium process. The instantaneous introduction of electrical energy, thermal energy, and strain energy affects the microstructure and macroscopic properties of metallic materials. As an application of high-energy external field processing in plastic forming, high-energy pulsed current assisted forming can significantly reduce material deformation resistance, improve plasticity, improve the microstructure and properties of products, reduce residual stress, eliminate or reduce annealing, and reduce porosity or heal cracks. High-energy pulsed current assisted metal forming has attracted widespread attention from scholars both domestically and internationally.

[0004] Ultrasonic vibration-assisted forming involves applying ultrasonic vibrations to a workpiece or mold, causing periodic loading and unloading of the material. Due to the stress superposition and softening effects, this effectively reduces the forming force, improves the forming performance of the material, lowers the friction coefficient of the workpiece contact surface, and significantly improves forming accuracy and surface quality. In recent years, ultrasonic vibration-assisted technology has been widely applied in processes such as drawing, blanking, stamping, incremental forming, and surface modification.

[0005] Although high-energy pulsed current and ultrasonic vibration have different loading methods and energy forms, they share a similar characteristic: both are rapid, non-equilibrium loading processes that can quickly create a localized high-energy field acting on the area to be processed. Therefore, both auxiliary methods are suitable for incremental forming processes, significantly improving the forming performance and quality of incrementally formed parts. However, the combination of these two auxiliary methods is a complex nonlinear process involving electro-thermal-mechanical-ultrasonic multi-physics coupling. Its influence on the forming performance and microstructure of the sheet metal, as well as on forming forces, friction, and residual stress during processing, is also quite complex.

[0006] Patent CN202410427840.X discloses a device for localized thermal / electrical / ultrasonic multi-field coupling assisted progressive forming of titanium alloy plates and its usage method. The device consists of a forming platform, a motion control system, a heating power supply, a pulse current generator, a robotic arm, a pressure bolt, a pressure plate, a first insulating block, a second insulating block, a loading tool head, a heat insulation plate, a vibrator, an ultrasonic generator, a movable electrode head, a resistance heater, an insulating plate, a spring, an electrode head carrier, and an infrared temperature sensor. The device achieves two-stage heating through localized non-contact heating and pulse current self-resistance heating, and utilizes the "ultrasonic softening" effect of the ultrasonic field to reduce the material's deformation resistance, thereby realizing multi-field coupling assisted progressive forming. However, the above-mentioned devices have the following shortcomings in application: First, during the ultrasonic vibration-assisted progressive forming process, the piezoelectric ceramic transducer generates a large amount of heat during continuous high-frequency vibration. If heat dissipation is not timely, the transducer's operating temperature will rise, leading to the deterioration of the piezoelectric ceramic performance and unstable vibration output frequency and amplitude, which seriously affects the ultrasonic-assisted forming effect. Second, during the electric pulse-ultrasonic composite assisted forming process, a large amount of Joule heat is generated when the high-energy pulse current passes through the contact area between the tool head and the sheet metal. This heat is conducted through the tool head to the amplitude transformer and transducer, further aggravating the heat accumulation of the ultrasonic vibration system, causing the ultrasonic vibration system to heat up too quickly, making it difficult to ensure the stability of ultrasonic vibration output under long-term high-intensity forming conditions. Third, the existing devices lack effective cooling methods for the ultrasonic vibration system. As the forming time increases, the system's heat accumulation effect becomes increasingly significant, making it difficult to guarantee the consistency of the formed part's quality. Summary of the Invention

[0007] To address the technical problems existing in the prior art, this invention discloses a device suitable for dieless forming of sheet metal using electric pulse-ultrasound multi-field coupling assisted progressive forming / tension-compression testing. This device is mainly applicable to experimental research on the tensile / compression deformation mechanism of lightweight alloys such as magnesium alloys and titanium alloys using DC / electric pulse-ultrasound coupling, and experimental research on DC / electric pulse-ultrasound coupling assisted single-point progressive forming processes.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention proposes an electro-pulse-ultrasonic multi-field coupling assisted progressive forming device suitable for moldless forming of sheet metal, comprising a rotating device, an external fixing device, and a specimen support device; The rotating device includes a handle-connected transition plate and a supporting shell. The handle-connected transition plate includes a long handle and a disc. The long handle is connected to a driving device, and an insulating sleeve is provided between the driving device and the long handle. The disc has radially distributed first air inlets of equal diameter, with the first air inlets facing the annular cavity of the air distribution ring at its outer periphery. The supporting shell is located inside the disc and is connected to the disc at its top. A second air inlet communicating with the first air inlets is provided on the side wall of the supporting shell. An air outlet is provided in the middle of the supporting shell and is connected to a silencer. A piezoelectric ceramic transducer is vertically fixed at the center of the disc, and the piezoelectric ceramic transducer is connected to the disc-mounted amplitude transformer via a double-sided handle-mounted ceramic connecting layer. The disc-mounted amplitude transformer is connected to the supporting shell via an interference fit to ensure reliable connection, and the disc-mounted amplitude transformer is connected to a forming tool head.

[0009] This invention introduces an active cooling system into an electro-pulse-ultrasonic multi-field coupled assisted progressive forming device. By continuously cooling the piezoelectric ceramic transducer with a cooling airflow, heat conduction from the tool head is isolated, ensuring that the ultrasonic vibration system maintains a stable working state during long-term processing, thereby guaranteeing the consistency and reliability of the forming quality.

[0010] As a further technical solution, the air distribution ring is fixed on an external fixing device.

[0011] As a further technical solution, the pulse electrical signal input of the piezoelectric ceramic transducer is input through a fixed signal connector or an induction coil.

[0012] As a further technical solution, the primary coil of the induction coil is fixed on the bracket, and the secondary coil of the induction coil is fixed on the outer wall of the supporting shell. The secondary coil is connected to the piezoelectric ceramic transducer through a power line.

[0013] As a further technical solution, the fixed signal connector is fixed to the supporting housing.

[0014] As a further technical solution, a conductive copper ring with good conductivity is nested on the outer layer of the connection between the disc-type amplitude rod and the supporting shell. It is used in conjunction with the carbon brush. The conductive copper ring is used in conjunction with the conductive block, and the conductive block is connected to the pulse power line.

[0015] As a further technical solution, the forming tool head and the disc-type amplitude rod are connected by threads. To ensure that the two do not loosen due to vibration and rotational friction during processing, a double locking nut is added to the thread of the tool head to prevent loosening.

[0016] As a further technical solution, the external fixing device includes an internal support frame and an external support frame. The internal support frame is used to support the air distribution ring, and the external support frame is used to support the air pipe, conductive block, pulse power line and primary coil.

[0017] As a further technical solution, the specimen support device includes a fixed pressure plate, a support structure, a specimen, and an insulating pad; the bottom of the support structure is provided with an insulating pad; the top of the support structure is provided with a fixed pressure plate; the specimen is fixed between the support structure and the fixed pressure plate.

[0018] As a further technical solution, a triaxial force sensor is installed at the bottom of the specimen support device. This sensor can accurately measure and record the force values ​​of the specimen along the X, Y, and Z axes of the machine tool coordinate system during the forming process. This provides a scientific and reliable basis for evaluating the forming force and studying the mechanical condition of the processing position during the forming process.

[0019] As a further technical solution, a temperature sensor is also included. The temperature sensor is fixed to the bottom of the workpiece and is integrated into the control system, which controls the pulse electrical signal of the piezoelectric ceramic transducer.

[0020] Secondly, based on the aforementioned electrical pulse-ultrasound multi-field coupling assisted progressive forming device, the present invention also provides a forming method, as follows: Step 1, Installation and Debugging: Connect the rotating device to the machine tool spindle via the long handle of the transition plate with a handle, and achieve electrical isolation through the insulating sleeve; install the external fixing device on the stationary part of the machine tool, adjust the alignment of the air distribution ring and the first air inlet, and connect the cooling air source, pulse power supply and ultrasonic generator; fix the plate specimen to be formed on the support structure through the fixing plate, and set the insulating pad at the bottom of the support structure; Step 2, Parameter Setting: Based on the sheet material and forming requirements, set the output power and frequency of the ultrasonic generator, set the voltage, current, duty cycle, and other parameters of the pulse power supply, and set the target forming temperature of the control system. Step 3: Start the cooling system: Turn on the cooling air source. The cooling gas enters the support shell through the air pipe, the annular cavity of the air distribution ring, the first air inlet, and the second air inlet to cool the piezoelectric ceramic transducer. The airflow is finally discharged through the air outlet and the silencer. Step 4: Applying an auxiliary energy field: Start the ultrasonic generator and input a pulsed electrical signal to the piezoelectric ceramic transducer through a fixed signal connector or induction coil to excite it to generate ultrasonic mechanical vibration. This vibration is transmitted to the forming tool head through the ceramic connecting layer and the disc-shaped amplitude transformer. At the same time, start the pulse power supply. The current is conducted to the forming tool head through the conductive block, carbon brush, conductive copper ring, and disc-shaped amplitude transformer, forming a circuit with the specimen as the negative electrode, generating a pulsed current in the contact area between the tool head and the plate. Step 5, Progressive Forming: With the coupling assistance of ultrasonic vibration and pulsed current, the machine tool spindle is controlled to drive the rotating device to move according to the preset CNC trajectory, so that the forming tool head performs progressive forming of the sheet material layer by layer; during the forming process, the temperature of the sheet material is monitored in real time by a temperature sensor and fed back to the control system. The control system achieves dynamic control of the temperature of the forming area by adjusting the pulse power supply parameters or ultrasonic parameters. The beneficial effects of this invention compared to the prior art are: (1) By setting a cooling gas path inside the supporting shell, the present invention actively and forcibly cools the piezoelectric ceramic transducer with continuously supplied cooling gas, which effectively solves the problem of heat accumulation in the ultrasonic vibration system during long-term high-intensity operation, ensures the stable output of ultrasonic vibration frequency and amplitude, and thus ensures the consistency of ultrasonic auxiliary effect and the reliability of part forming quality during the forming process. (2) The present invention isolates the high-energy pulse current applied to the side of the forming tool head from the ultrasonic transducer through the ceramic connecting layer. At the same time, combined with the continuous heat dissipation of the cooling air path, it effectively prevents the electromagnetic interference generated by the pulse current and the Joule heat from interfering with and damaging the piezoelectric ceramic transducer, and realizes the long-term stable operation of the electric pulse-ultrasound composite assistance. (3) The present invention applies the combined auxiliary action of electric pulse and ultrasonic vibration to the deformation process of the sheet metal. The electroplastic effect and Joule heating effect generated by the electric pulse work synergistically with the ultrasonic softening effect and stress superposition effect to significantly reduce the deformation resistance of the sheet metal, improve the forming limit of the material, and effectively improve the forming performance and surface quality of the formed parts. (4) The present invention ensures the thermal balance of the ultrasonic vibration system through the active heat dissipation of the cooling air path, enabling the device to operate stably under the conditions of large-volume and long-term progressive forming processing, thereby improving the service life and processing efficiency of the device. Attached Figure Description

[0021] Figure 1 This is an overall schematic diagram of the device of the present invention; Figure 2 This is a schematic diagram of the specific mechanical structure corresponding to the present invention; Figure 3 This is a partial enlarged schematic diagram of the structure of the present invention; In the diagram: 1. Machine tool spindle end face; 2. Tool holder; 3. PEEK insulating sleeve; 4. Internal support frame; 5. Gas distribution ring; 6. External support frame; 7. Support shell; 8. Fixed pressure plate; 9. Support structure; 10. Specimen; 11. Forming tool head; 12. Double locking nut; 13. Amplitude rod with disc; 14. Conductive copper ring; 15. Carbon brush; 16. Conductive block; 17. External support frame; 18. Pulse power line; 19. Silencer; 20. Ultrasonic generator signal line; 21. Fixed signal connector; 22. Primary induction coil; 23. Secondary induction coil; 25. Handle connecting transition plate; 26. Clamp; 35. Piezoelectric ceramic transducer; 36. Ceramic connecting layer; 37. Insulating pad; 38. Cold air inlet; 39. Cold air outlet. Detailed Implementation It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. For ease of description, the words "up," "down," "left," and "right" appearing in this invention only indicate that they are consistent with the up, down, left, and right directions of the accompanying drawings themselves, and do not limit the structure. They are merely for the purpose of facilitating the description of this invention and simplifying the description, and do not indicate or imply that the device or component 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 invention.

[0023] This invention provides an electrical pulse-ultrasound multi-field coupling assisted progressive forming device for lightweight alloy sheets. This device can improve the local deformation capacity and reduce the deformation resistance of lightweight alloy materials by applying high-energy pulse current and ultrasonic vibration to the processing position to form a local high-energy field during the progressive forming process. It also utilizes the stress superposition and surface effect brought about by ultrasonic high-frequency vibration to improve the contact condition between the tool head and the workpiece surface, reduce wear, thereby improving the forming performance and obtaining high-quality formed parts.

[0024] The basic components of this device include: a CNC milling machine, a BT40 tool holder, an ultrasonic generator, and an electrical pulse-ultrasonic multi-field coupling assisted progressive forming tool head assembly (including...). Figure 1The instrument includes an ultrasonic transducer, an ultrasonic amplitude transformer, a forming tool head, a plate specimen, a specimen support frame, a triaxial force sensor, an infrared temperature probe and temperature control recorder, and a high-frequency pulse power supply. To meet experimental requirements, the ultrasonic generator outputs a 2kW high-frequency oscillating current to the transducer's piezoelectric ceramic plate. The amplitude is amplified by the amplitude transformer and applied to the plate. The high-frequency vibration direction of the tool head is as follows: Figure 1 As indicated by the black arrow in the middle, the overall natural frequency of the electrical pulse-ultrasound multi-field coupling assisted progressive forming tool head component is 25 kHz. (For the specific structure of the electrical pulse-ultrasound multi-field coupling assisted progressive forming tool head component within the dashed box, see...) Figure 3 。 The positive terminal of the pulse power supply is connected to the reserved interface position on the tool head component, and the negative terminal is connected to the fixing plate 8 of the workpiece, forming a current loop. The current flow direction is as follows: Figure 1 As indicated by the red arrow, this high-frequency pulse power supply can generate a peak current ≥5000 Amps, an output power of 100-800Hz, an output voltage of 0-60V, and a pulse width of 50-200 micrometers. When the pulse current passes through the contact area between the tool head and the workpiece, due to the limited contact area, a large amount of Joule heating and electroplastic effect are generated instantaneously, thus significantly improving the local forming performance of the workpiece. The low voltage and high current characteristics also ensure that the air will not break down and form sparks due to the possible tiny gaps between the workpiece and the tool head when the tool head vibrates, ensuring that there is no discharge corrosion on the upper surface of the workpiece.

[0025] Before forming, the lower surface of the sheet is sprayed with a high-temperature matte paint to achieve a matte finish. During forming, a long-wave infrared probe, stationary relative to the tool head, is positioned beneath the sheet to measure the temperature of the lower surface in real time. Since this progressive forming process primarily targets thin sheets of 0.5–1 mm, the temperatures of the upper and lower surfaces are almost identical. Therefore, the infrared temperature probe readings are used as the forming area temperature and input into a PLC / PID temperature controller for reliable temperature feedback. The PLC / PID temperature controller adjusts the power output to achieve real-time temperature control of the forming area.

[0026] The bottom of the specimen support frame is equipped with a triaxial force sensor, which can accurately measure and record the force values ​​of the specimen along the X, Y, and Z axes of the machine tool coordinate system during the forming process. This provides a scientific and reliable basis for evaluating the forming force and studying the mechanical condition of the processing position during the forming process.

[0027] By arranging an insulating layer at the mounting area and bottom of the BT40 tool holder ( Figure 1 The dense grid design achieves insulation between the experimental setup and the milling machine spindle and worktable, except for the milling machine itself. Meanwhile, the insulation layer in the middle of the support frame ensures that the pulse current will not affect the normal operation of the force sensor.

[0028] Specifically, the structural scheme of the electrical pulse-ultrasound multi-field coupling assisted progressive forming tool head component is as follows: Figure 2 , Figure 3 As shown. This tool head component can simultaneously rotate the tool head and apply ultrasonic vibration and electrical pulses to it. The specific structure of this device can be divided into the following three parts: The first part is the rotating part, which is the core part of this device, including: BT40-C32-85 tool holder 2, PEEK insulating sleeve 3, handle-connecting transition plate 25, support shell 7, silencer 19, disc-type amplitude transformer 13, ceramic connecting layer 36, piezoelectric ceramic transducer 35, fixed signal connector 21, double locking nut 12, forming tool head 11, conductive copper ring 14, and secondary induction coil 23; The second part is the external fixed part, including the pulse power line 18, the ultrasonic generator signal line 20, the air tube and connector 24, and a series of static insulating support components and auxiliary structures, including: machine tool spindle end face 1, inner support frame 4, air distribution ring 5, outer support frame 17, sealing ring 34, clamp 26, power line support frame 17, primary coil 22, conductive block 16, carbon brush 15; Thirdly, the specimen support part includes: a fixed pressure plate 8, a support structure 9, a specimen 10, and an insulating pad 37; the bottom of the support structure 9 is provided with an insulating pad 37; the top of the support structure 9 is provided with a fixed pressure plate 8; the specimen 10 is fixed on the top of the support structure 9 and then fixed by the fixed pressure plate 8.

[0029] The aforementioned shank-connected transition disc 25 includes a long shank and a large-diameter disc. A PEEK insulating sleeve 3 is nested around the long shank. The long shank wrapped with the insulating sleeve 3 is inserted into the BT40-C32-85 tool holder 2. The upper end of the tool holder 2 is inserted into the milling machine spindle end 1, thus fixing the rotating part of the tool head onto the milling machine spindle.

[0030] The handle-connecting transition plate 25 includes a large-diameter disc with evenly distributed circular air holes of equal diameter around its periphery. These circular air holes face the annular cavity of the air distribution ring 5. Airtight rings 34 are arranged above and below the cavity to prevent excessive leakage of cooling airflow from the air pipe 24. Sufficient cold air enters through the annular cavity of the air distribution ring 5 and the evenly distributed air holes of the handle-connecting transition plate 25, ultimately entering the cavity containing the piezoelectric ceramic transducer 35. A cold air inlet 38 is also provided on the supporting housing 7. The cold air inlet 38 corresponds to the circular air holes on the handle-connecting transition plate 25. Additionally, an air outlet 39 is provided on the supporting housing 7. The air outlet 39 is connected to a silencer 19. Hot air is smoothly discharged through the exhaust port of the silencer 19 located above the partition in the middle of the supporting housing 7, thereby ensuring the cooling effect of the ceramic plate, isolating heat from the tool head, and maintaining stable ultrasonic vibration output during operation. A piezoelectric ceramic transducer 35 is vertically fixed at the center of the large-diameter disk. The piezoelectric ceramic transducer 35 is connected to the disk-mounted amplitude transformer 13 via a double-sided ceramic connecting layer 36 with a handle. To ensure vibration transmission efficiency, the piezoelectric ceramic transducer 35 and the ceramic connecting layer 36, as well as the ceramic connecting layer 36 and the disk-mounted amplitude transformer 13, are all interference-fitted connections. The ceramic connecting layer 36 can isolate the high-energy pulse power supply applied to the tool head side, avoiding interference from the high-energy pulse current to the piezoelectric ceramic during ultrasonic-electric pulse assisted machining.

[0031] Meanwhile, the signal connectors and other electrical components used in the piezoelectric ceramic transducer 35 must also be wrapped with an insulating outer sheath containing a metal core to prevent electromagnetic interference generated by the pulse current from affecting the signal input of the piezoelectric ceramic transducer 35. The piezoelectric ceramic transducer 35 has two pulse signal input methods, one of which is a fixed signal connector 21, used for signal input under non-rotating conditions. Figure 3 (As shown by the dashed line in the middle). Another method is to achieve non-contact electrical signal transmission through an induction coil, which is suitable for rotating conditions. The secondary coil of the induction coil is nested on the support housing 7 and rotates together with the tool head, while the primary coil is fixed to the end face 1 of the machine tool spindle by the external support frame 17 and the clamp 26 to remain stationary.

[0032] The disc-type amplitude transformer 13 is connected to the support housing 7 by an interference fit to ensure a reliable connection. The disc position of the disc-type amplitude transformer 13 is selected at a position where the amplitude value of the amplitude transformer is zero when the cointegration frequency is 25KHz, to ensure that the support housing 7 and other components do not vibrate simultaneously.

[0033] A conductive copper ring 14 with good conductivity is nested around the connection between the disc-type amplitude transformer 13 and the supporting housing 7. This ring, in conjunction with the carbon brush 15, ensures that the pulse current, during tool head rotation, can form a circuit through the pulse power line 18, conductive block 16, carbon brush 15, conductive copper ring 14, amplitude transformer 13, forming tool head 11, test piece 10, and fixed pressure plate 8, connecting to the negative terminal of the power supply. The forming tool head 11 and the disc-type amplitude transformer 13 are connected by threads. To prevent loosening due to vibration and rotational friction during processing, a double locking nut 12 is added to the tool head thread to prevent loosening.

[0034] Based on the aforementioned electrical pulse-ultrasound multi-field coupling assisted progressive forming device, this embodiment also provides a forming method, as detailed below: Step 1, Installation and Debugging: Connect the rotating device to the machine tool spindle via the long handle of the transition plate with a handle, and achieve electrical isolation through the insulating sleeve; install the external fixing device on the stationary part of the machine tool, adjust the alignment of the air distribution ring and the first air inlet, and connect the cooling air source, pulse power supply and ultrasonic generator; fix the plate specimen to be formed on the support structure through the fixing plate, and set the insulating pad at the bottom of the support structure; Step 2, Parameter Setting: Based on the sheet material and forming requirements, set the output power and frequency of the ultrasonic generator, set the voltage, current, duty cycle, and other parameters of the pulse power supply, and set the target forming temperature of the control system. Step 3: Start the cooling system: Turn on the cooling air source. The cooling gas enters the support shell through the air pipe, the annular cavity of the air distribution ring, the first air inlet, and the second air inlet to cool the piezoelectric ceramic transducer. The airflow is finally discharged through the air outlet and the silencer. Step 4: Applying an auxiliary energy field: Start the ultrasonic generator and input a pulsed electrical signal to the piezoelectric ceramic transducer through a fixed signal connector or induction coil to excite it to generate ultrasonic mechanical vibration. This vibration is transmitted to the forming tool head through the ceramic connecting layer and the disc-shaped amplitude transformer. At the same time, start the pulse power supply. The current is conducted to the forming tool head through the conductive block, carbon brush, conductive copper ring, and disc-shaped amplitude transformer, forming a circuit with the specimen as the negative electrode, generating a pulsed current in the contact area between the tool head and the plate. Step 5, Progressive Forming: With the coupling assistance of ultrasonic vibration and pulsed current, the machine tool spindle is controlled to drive the rotating device to move according to the preset CNC trajectory, so that the forming tool head performs progressive forming of the sheet material layer by layer; during the forming process, the temperature of the sheet material is monitored in real time by a temperature sensor and fed back to the control system. The control system achieves dynamic control of the temperature of the forming area by adjusting the pulse power supply parameters or ultrasonic parameters. Step 6: End of forming: After the forming reaches the predetermined depth, turn off the pulse power supply, ultrasonic generator and cooling air source in sequence, retract the forming tool head to the safe position and remove the formed specimen.

[0035] This invention solves the problem of heat accumulation in ultrasonic vibration systems during long-term high-intensity operation by setting a cooling gas path inside the supporting shell and using continuously introduced cooling gas to actively and forcibly cool the piezoelectric ceramic transducer. This ensures the stable output of ultrasonic vibration frequency and amplitude, thereby guaranteeing the consistency of ultrasonic assistance effect and the reliability of part forming quality during the forming process. This invention isolates the high-energy pulse current applied to the forming tool head from the ultrasonic transducer through a ceramic connecting layer. At the same time, combined with the continuous heat dissipation of the cooling air path, it effectively prevents the electromagnetic interference generated by the pulse current and the Joule heat from interfering with and damaging the piezoelectric ceramic transducer, thus realizing the long-term stable operation of the electric pulse-ultrasound composite assistance. This invention utilizes the combined assistance of electrical pulses and ultrasonic vibrations to enhance the deformation process of sheet metal. The electroplastic and Joule heating effects generated by the electrical pulses, along with the ultrasonic softening effect and stress superposition effect, work synergistically to significantly reduce the deformation resistance of the sheet metal, improve the forming limit of the material, and effectively improve the forming performance and surface quality of the formed parts. This invention ensures the thermal balance of the ultrasonic vibration system through active heat dissipation of the cooling air path, enabling the device to operate stably and continuously under large-volume, long-term progressive forming processing conditions, thereby improving the service life and processing efficiency of the device.

[0036] Finally, it should be noted that relational terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electropulse-ultrasonic multi-field coupling assisted progressive forming device suitable for moldless forming of sheet metal, comprising a rotating device, an external fixing device, and a specimen support device; characterized in that: The rotating device includes a handle-connected transition plate and a supporting shell. The handle-connected transition plate includes a long handle and a disc. The long handle is connected to a driving device, and an insulating sleeve is provided between the driving device and the long handle. The disc has radially distributed first air inlets of equal diameter, with the first air inlets facing the annular cavity of the air distribution ring at its outer periphery. The supporting shell is located inside the disc and is connected to the disc at its top. A second air inlet communicating with the first air inlets is provided on the side wall of the supporting shell. An air outlet is provided in the middle of the supporting shell and is connected to a silencer. A piezoelectric ceramic transducer is vertically fixed at the center of the disc, and the piezoelectric ceramic transducer is connected to the disc-mounted amplitude transformer via a double-sided handle-mounted ceramic connecting layer. The disc-mounted amplitude transformer is connected to the supporting shell via an interference fit to ensure reliable connection, and the disc-mounted amplitude transformer is connected to a forming tool head.

2. The electropulse-ultrasonic multi-field coupling assisted progressive forming device for dieless forming of sheet metal as described in claim 1, characterized in that: The outer layer of the connection between the disc-type amplitude rod and the supporting shell is nested with a conductive copper ring with good conductivity. It is used in conjunction with the carbon brush. The conductive copper ring is used in conjunction with the conductive block, and the conductive block is connected to the pulse power line.

3. The electropulse-ultrasonic multi-field coupling assisted progressive forming device for dieless forming of sheet metal as described in claim 1, characterized in that: The specimen support device includes a fixed pressure plate, a support structure, a specimen, and an insulating pad; the bottom of the support structure is provided with an insulating pad; the top of the support structure is provided with a fixed pressure plate. The specimen is fixed between the supporting structure and the fixed pressure plate.

4. The electropulse-ultrasonic multi-field coupling assisted progressive forming device for dieless forming of sheet metal as described in claim 1, characterized in that: A triaxial force sensor is installed at the bottom of the specimen support device to measure and record the force values ​​of the specimen along the X, Y, and Z axes of the machine tool coordinate system during the forming process.

5. The electropulse-ultrasonic multi-field coupling assisted progressive forming device for dieless forming of sheet metal as described in claim 1, characterized in that: It also includes a temperature sensor, which is fixed to the bottom of the workpiece. The temperature sensor is integrated into the control system, which controls the pulse electrical signal of the piezoelectric ceramic transducer.

6. The electropulse-ultrasonic multi-field coupling assisted progressive forming device for dieless forming of sheet metal as described in claim 1, characterized in that: The pulse electrical signal input of the piezoelectric ceramic transducer is input through a fixed signal connector or an induction coil.

7. The electropulse-ultrasonic multi-field coupling assisted progressive forming device for dieless forming of sheet metal as described in claim 6, characterized in that: The primary coil of the induction coil is fixed on an external fixing device, and the secondary coil of the induction coil is fixed on the outer wall of the supporting shell. The secondary coil is connected to the piezoelectric ceramic transducer through a power line.

8. The electropulse-ultrasonic multi-field coupling assisted progressive forming device for dieless forming of sheet metal as described in claim 7, characterized in that: The external fixing device includes an internal support frame and an external support frame. The internal support frame is used to support the air distribution ring; the external support frame is used to support the air pipe, conductive block, pulse power line and coil.

9. The electropulse-ultrasonic multi-field coupling assisted progressive forming device for dieless forming of sheet metal as described in claim 1, characterized in that: The forming tool head and the disc-type amplitude rod are connected by threads, and double locking nuts are added to the threaded part of the tool head to prevent loosening.

10. The processing method of the electropulse-ultrasonic multi-field coupling assisted progressive forming device for dieless forming of sheet metal as described in any one of claims 1-9, characterized in that: Step 1: Connect the rotating device to the machine tool spindle via the long handle of the transition plate with a handle, and achieve electrical isolation through the insulating sleeve; install the external fixing device on the stationary part of the machine tool, adjust the alignment of the air distribution ring and the first air inlet, and connect the cooling air source, pulse power supply and ultrasonic generator; fix the plate specimen to be formed on the specimen support device. Step 2: Based on the sheet material and forming requirements, set the output power and frequency of the ultrasonic generator and related parameters, and set the target forming temperature of the control system; Step 3: Turn on the cooling gas source. The cooling gas enters the support shell through the air pipe, the annular cavity of the air distribution ring, the first air inlet, and the second air inlet to cool the piezoelectric ceramic transducer. The airflow is finally discharged through the air outlet and the silencer. Step 4: Start the ultrasonic generator and input a pulsed electrical signal to the piezoelectric ceramic transducer through a fixed signal connector or induction coil to excite it to generate ultrasonic frequency mechanical vibration. This vibration is transmitted to the forming tool head through the ceramic connecting layer and the disc-shaped amplitude transformer. At the same time, start the pulse power supply. The current is transmitted to the forming tool head through the conductive block, carbon brush, conductive copper ring, and disc-shaped amplitude transformer, forming a circuit with the specimen as the negative electrode, generating a pulsed current in the contact area between the tool head and the plate. Step 5: With the coupling assistance of ultrasonic vibration and pulsed current, control the machine tool spindle to drive the rotating device to move according to the preset CNC trajectory, so that the forming tool head can perform layer-by-layer progressive forming of the sheet material. During the forming process, the temperature of the sheet material is monitored in real time by a temperature sensor and fed back to the control system. The control system dynamically controls the temperature of the forming area by adjusting the pulse power supply parameters or ultrasonic parameters.

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