Thin-wall microtube drawing device and drawing method

Abstract

The invention relates to the technical field of thin-wall micropipe drawing, in particular to a thin-wall micropipe drawing device and method. Comprising a wedge block, a drawing die and two outer die ultrasonic transduction mechanisms and is used for providing a vibration field for the drawing die in the drawing forming process, and a certain included angle is formed between the forging stress of the vibration field and the central axis direction of the thin-wall micropipe; the core rod ultrasonic transduction mechanism is provided with a core rod, the core rod penetrates through the wedge block and extends into the forming cavity, and a gap is formed between the core rod and the drawing die; the guide column is installed on the guide column support and used for limiting the combined vibration direction of the two external mold ultrasonic transduction mechanisms to be in the vertical direction. The end cover makes contact with the bottom of the drawing die. Through the synergistic effect of the two outer mold ultrasonic transduction mechanisms and the core rod ultrasonic transduction mechanism, a vibration field is provided for the drawing mold in the drawing forming process, the single-pass deformation amount can be increased, microcosmic flow of materials is promoted, and generation of local cracks of a micropipe is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of thin-walled microtube drawing, and more particularly to a thin-walled microtube drawing device and a drawing method. Background Art

[0002] Magnesium alloys and titanium alloys have the characteristics of low density and high strength, and at the same time have good biocompatibility, making them good medical metallic materials.

[0003] However, magnesium alloys have poor plasticity, average formability, and are difficult to draw thin-walled microtubes, making it difficult to apply them in the manufacture of absorbable vascular stents. Titanium alloys have high strength, high deformation resistance during plastic processing, and relatively serious springback after processing. There is a chip adhesion problem during cutting, which has an adverse effect on the surface quality and dimensional accuracy of titanium products.

[0004] The magnesium alloys drawn by existing microtube drawing devices have poor plasticity, many cracks, and poor quality. Based on the existing drawing devices, the requirements for the drawing process of difficult-to-machine metals such as magnesium alloys cannot be met. Summary of the Invention

[0005] The present invention aims to at least improve one of the technical problems existing in the prior art. To this end, the present invention proposes a thin-walled microtube drawing device.

[0006] The technical solution of the present invention is as follows: A thin-walled microtube drawing device, which is installed on a moving platform, and the device includes: A wedge block, including: A first mounting portion, which is provided with a through hole and two limit holes; A second mounting portion, which is mounted on the surface of the first mounting portion and is in communication with the through hole, and the second mounting portion has a plurality of stepped portions; A drawing die, which is embedded in the stepped portion, and the drawing die has a forming cavity; Two external mold ultrasonic transducer mechanisms, which are connected to the first mounting portion and are used to provide a vibration field for the drawing die during the drawing forming process, and the forging stress of the vibration field forms a certain angle with the central axis direction of the thin-walled microtube; A mandrel ultrasonic transducer mechanism, which has a mandrel, and the mandrel passes through the through hole and extends into the forming cavity, and has a gap with the drawing die; A guide post, which is mounted on a guide post support and is adapted to the limit hole to limit the combined vibration direction of the two external mold ultrasonic transducer mechanisms to be in the vertical direction; An end cap, which is threadedly connected to the second mounting portion and is in contact with the bottom of the drawing die.

[0007] In a possible technical solution, further, the second mounting portion includes: Multiple kidney-shaped holes are spirally distributed in a single direction on the tube wall of the second mounting portion. The spiral distribution of the kidney-shaped holes in a single direction is beneficial for the kidney-shaped holes to play a synergistic role.

[0008] In a possible technical solution, further, the direction includes a left spiral vibration direction and a right spiral vibration direction, which is beneficial for the mandrel to generate a composite vibration in the torsional and vertical directions, and it can perform a left spiral movement or a right spiral movement.

[0009] In a possible technical solution, further, multiple kidney-shaped holes are located at the same height on the tube wall of the second mounting portion, in order to ensure the maximum displacement of the spiral vibration, and the spiral vibration direction of the wedge block will not produce large fluctuations, ensuring that the direction of vibration synthesis is always in the vertical direction.

[0010] In a possible technical solution, further, the kidney-shaped hole forms a 45° angle with the horizontal direction of the tube wall, avoiding too small or too large inclination angles resulting in too small horizontal direction components of the spiral vibration and the spiral vibration effect being not obvious.

[0011] In a possible technical solution, further, the outer mold ultrasonic transducer mechanism is symmetrically arranged with respect to the mandrel, so that when the amplitudes of vibration of the two outer mold ultrasonic transducer mechanisms are the same, the horizontal components of their vibrations can cancel each other out.

[0012] In a possible technical solution, further, the included angle range between the outer mold ultrasonic transducer mechanism and the mandrel is 45° to 75°, for balancing the installation space and the displacement on the central axis of the axial synthesis.

[0013] In a possible technical solution, further, the outer mold ultrasonic transducer mechanism includes: An ultrasonic transducer is connected to the first mounting portion. The ultrasonic transducer has a first rear cover, and a plurality of first piezoelectric wafers are provided between the front end of the ultrasonic transducer body and the first rear cover.

[0014] In a possible technical solution, further, the mandrel ultrasonic transducer mechanism includes: A mandrel; A mandrel ultrasonic transducer is connected to the mandrel. The mandrel ultrasonic transducer has a second rear cover, and a plurality of second piezoelectric wafers are provided between the front end of the mandrel ultrasonic transducer body and the second rear cover.

[0015] The thin-wall microtube drawing device according to the present invention has the following beneficial effects: Through the collaborative action of two external die ultrasonic transducer mechanisms and a mandrel ultrasonic transducer mechanism, a vibration field is provided for the drawing die during the drawing forming process. Compared with the vertical drawing process of traditional technology, the deformation amount per pass is increased, the micro-flow of the material is promoted, the local crack initiation of the microtube is reduced, and finally the purpose of efficiently preparing thin-walled microtubes with a short process is achieved. Specifically: 1. Through the collaboration of two external die ultrasonic transducer mechanisms and a mandrel ultrasonic transducer mechanism, the friction between the drawn workpiece and the drawing die and the forming force of drawing can be reduced, the forming ability and surface quality of the microtube material can be improved, and while reducing the wall thickness of the microtube, the number of processing passes can be further reduced.

[0016] 2. During the microtube forming process, through the two external die ultrasonic transducer mechanisms and the mandrel ultrasonic transducer mechanism, the stress state of the drawing die is changed from tensile stress to compressive stress and shear stress, that is, from drawing processing to forging processing. The high-frequency vibration of the drawing die and the mandrel causes periodic pressing and relaxation between the microtube material and the die and the mandrel. High-frequency microscopic plastic flow occurs on the surface of the microtube material, promoting the deformation of the microtube material in the compression zone, and finally reducing the risk of the microtube being pulled and broken.

[0017] 3. The contact stress between the microtube surface and the die and the mandrel decreases or even becomes zero, which is beneficial to the infiltration of lubricating oil and the maintenance of the lubrication state, effectively reducing the friction force and further reducing the initiation of surface microscopic cracks caused by friction.

[0018] 4. The grain boundaries or the interfaces of the second-phase particles of the microtube absorb the energy of the high-frequency vibration, resulting in an increase in the internal energy of the local microscopic region, reducing the energy barrier that the dislocation movement needs to overcome, promoting the dislocation movement, and finally reducing the deformation resistance.

[0019] A method for drawing thin-walled microtubes, wherein the above-mentioned device is used to draw the thin-walled microtubes, including the following contents: Press the drawing die tightly to the bottom of the end cover of the wedge block; After installing the device on the linear motion platform, remove the end cover; Flatten the front end of the microtube to reduce the front-end diameter, then sleeve it onto the mandrel, and re-insert it into the through-hole of the wedge block until it reaches inside the drawing die; Fix the flattened small head on the linear motion platform; Start the power supply, and according to the working parameters of the ultrasonic transducer and the mandrel ultrasonic transducer input by the device, the working parameters include: working frequency, amplitude, phase angle; Select different working modes according to the input working parameters, and the working modes include non-vibration mode, co-directional vibration mode, and reverse vibration mode; Start the linear motion platform, set the speed of the linear motion platform to draw the microtube to complete the drawing operation of the thin-walled microtube.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 is a schematic structural diagram of a thin-walled microtube drawing device of the present invention.

[0023] Figure 2 is a schematic diagram of the first kidney-shaped hole of the thin-walled microtube drawing device of the present invention.

[0024] Figure 3 is a schematic diagram of the second kidney-shaped hole of the thin-walled microtube drawing device of the present invention.

[0025] Figure 4 is a schematic diagram of a drawing die and a core rod of the thin-walled microtube drawing device of the present invention.

[0026] Figure 5 is a schematic diagram of different phases of the core rod and the wedge block; Figure 6 is a schematic diagram of different frequencies and amplitudes of the core rod and the wedge block; Figure 7 is a working schematic diagram of finite element vibration drawing simulation; Figure 8 is a general schematic diagram of drawing forces under different drawing conditions; Figure 9 is a partial schematic diagram of drawing forces at the same moment under different drawing conditions; Figure 10 is a stress nephogram of drawing forces at the same moment under different drawing conditions.

[0027] Reference Signs: Wedge block 1, first mounting portion 10, through hole 101, limiting hole 102, second mounting portion 11, stepped portion 110, kidney-shaped hole 111; Drawing die 2, forming cavity 21; External mold ultrasonic transducer mechanism 3, ultrasonic transducer 31, first rear cover 311, first piezoelectric wafer 312; Core rod ultrasonic transducer mechanism 4, core rod 41, core rod ultrasonic transducer 42, second rear cover 421, second piezoelectric wafer 422; Guide post 5; End cover 6; Guide post support 7. Specific implementation mode

[0028] The embodiments of the present invention will be described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0029] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can also be a middle element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be a middle element at the same time.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention in this specification are only for the purpose of describing specific implementation modes and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0031] The terms "first", "second", "third", etc. in the specification and claims of the present application and the accompanying drawings are used to distinguish different objects and are not used to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a series of steps or units are included, or optionally, steps or units not listed are also included, or optionally, other steps or units inherent to these processes, methods, products or devices are also included.

[0032] Only parts related to the present application are shown in the drawings, not all of the content. Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations (or steps) as sequential processes, many of the operations can be implemented in parallel, concurrently, or simultaneously. In addition, the order of the operations can be rearranged. When the operations are completed, the process can be terminated, but there can also be additional steps not included in the drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0033] As used in this specification, the terms "component", "module", "system", "unit", etc. are used to denote computer-related entities, hardware, firmware, combinations of hardware and software, software, or software in execution. For example, a unit may be, but is not limited to, a process running on a processor, a processor, an object, an executable, an execution thread, a program, and / or one or more computers distributed between two or more computers. In addition, these units may execute from various computer-readable media storing various data structures. A unit may, for example, communicate through local and / or remote processes according to signals having one or more data packets (e.g., data from a second unit interacting with another unit between a local system, a distributed system, and / or a network. For example, the Internet interacting with other systems through signals).

[0034] Embodiment 1 As Figures 1 to 9 shown, a thin-walled microtube drawing device, which is installed on a moving platform, and the device includes: A wedge block 1, including: A first mounting portion 10, which is provided with a through hole 101 and two limiting holes 102. The first mounting portion 10 is provided with two threaded holes, and the two threaded holes are symmetric about the through hole 101 and are arranged at an angle to the through hole 101; A second mounting portion 11, which is mounted on the surface of the first mounting portion 10 and is communicated with the through hole 101. The second mounting portion 11 has a plurality of stepped portions 110, and the inner diameter of the stepped portions 110 gradually decreases in the direction close to the through hole 101. In this embodiment, the second mounting portion 11 is an integral round tube; A drawing die 2, which is embedded in the stepped portion 110. The drawing die 2 has a forming cavity 21, and the forming cavity 21 is used for placing a workpiece to be formed; Two outer die ultrasonic transducer mechanisms 3, which are correspondingly mounted in the threaded holes and connected to the first mounting portion 10, and are used to provide a vibration field for the drawing die 2 during the drawing forming process. The forging stress of the vibration field forms a certain angle with the central axis direction of the thin-walled microtube. The outer die ultrasonic transducer mechanism 3 includes: An ultrasonic transducer 31 is connected to the first mounting portion 10. The ultrasonic transducer 31 has a first rear cover 311, and a plurality of first piezoelectric wafers 312 are provided between the front end of the ultrasonic transducer 31 body and the first rear cover 311.

[0035] A core rod ultrasonic transducer mechanism 4, which has a core rod 41. The core rod 41 passes through the through hole 101 and extends into the forming cavity 21, and has a gap with the drawing die 2; A guide post 5, which is mounted on a guide post support 7 and is adapted to the limiting holes 102 to limit the combined vibration direction of the two outer die ultrasonic transducer mechanisms 3 to be in the vertical direction; The end cap 6 is threadedly connected to the second mounting portion 11 and is in contact with the bottom of the drawing die 2.

[0036] It should be noted that in this embodiment, the wedge block 1 is an integrally formed wedge block.

[0037] It should be noted that a cooling device for cooling the microtube can be provided at the outlet of the end cap 6 to achieve heat treatment of the microtube.

[0038] It should be noted that a heating coil is provided in the second mounting portion 11 of the wedge block 1 to preheat the microtube.

[0039] It should be noted that the second mounting portion 11 includes: A plurality of waist-shaped holes 111 are spirally distributed in a single direction on the tube wall of the second mounting portion 11. The spiral distribution of the waist-shaped holes in a single direction is beneficial for the waist-shaped holes to play a synergistic role. If the distribution directions of the waist-shaped holes are inconsistent, the second mounting portion 11 cannot generate effective spiral vibration. The second mounting portion 11 has lower support stiffness in the normal direction of the spiral direction, prompting the wedge block to convert the axial vibration synthesized by the first mounting portion 10 into a direction perpendicular to the spiral direction of the waist-shaped holes. For example, if the waist-shaped holes are in the right spiral direction, the "lower end face" of the wedge block makes a left spiral vibration. In this embodiment, the spiral direction can be the left spiral vibration direction or the right spiral vibration direction, which is beneficial for the mandrel to generate a composite vibration of torsion and vertical direction, and can make a left spiral movement or a right spiral movement. In this embodiment, the spiral angle is the included angle between the waist-shaped hole 111 and the horizontal direction of the tube wall; A plurality of waist-shaped holes 111 are located at the same height on the tube wall of the second mounting portion 11 to ensure the maximum displacement of the spiral vibration and prevent large fluctuations in the spiral vibration direction of the wedge block, ensuring that the direction of vibration synthesis is always in the vertical direction.

[0040] It should be noted that the spiral angle of each waist-shaped hole 111 is 45°. From the formula where represents the displacement in the vertical direction, represents the displacement in the horizontal direction, represents the included angle between the waist-shaped hole and the horizontal direction; It can be calculated that 45° is the angle with the best spiral vibration effect. Too small or too large inclination angles result in too small horizontal direction components of the spiral vibration, and the spiral vibration effect is not obvious.

[0041] It should be noted that the outer die ultrasonic transducer mechanism 3 is symmetrically arranged with respect to the core rod 41. To ensure that the angles between the two outer die ultrasonic transducer mechanisms and the core rod are the same, when the amplitudes of vibration of the two outer die ultrasonic transducer mechanisms are the same, it is ensured that the horizontal components of the vibrations of the two outer die ultrasonic transducer mechanisms can cancel each other out.

[0042] It should be noted that the angle range between the outer die ultrasonic transducer mechanism 3 and the core rod 41 is 45° to 75°. To ensure that the angle between the outer die ultrasonic transducer mechanism 3 and the core rod 41 will not result in insufficient installation space due to a too small angle, nor will it cause a too small displacement on the central axis of the axial synthesis due to a too large angle.

[0043] It should be noted that in this embodiment, the core rod ultrasonic transducer mechanism 4 includes: The core rod 41; The core rod ultrasonic transducer 42 is connected to the core rod 41. The core rod ultrasonic transducer 42 has a second rear cover 421. A plurality of second piezoelectric wafers 422 are provided between the front end of the main body of the core rod ultrasonic transducer 42 and the second rear cover 421. In this embodiment, the core rod ultrasonic transducer 42 is threadedly connected to the core rod 41.

[0044] It should be noted that in this embodiment, the number of piezoelectric ceramics in the first piezoelectric wafer 312 and the second piezoelectric wafer 422 must be an even number, and its power is changed by changing the number of piezoelectric ceramics, or changing the voltage and current.

[0045] It should be noted that the guide post 5 is adapted to the limit hole 102 to limit the combined vibration direction of the two outer die ultrasonic transducer mechanisms 3 to be in the vertical direction. Specifically, the guide post 5 combines the vibrations generated by the two outer die ultrasonic transducer mechanisms 3 into a vertical vibration: because the two ultrasonic transducers 31 are connected to the same power supply and have the same frequency, but due to manufacturing and assembly reasons, there will be certain differences in the vibration dynamic characteristics of the two ultrasonic transducers 31, resulting in a slightly different amplitude, causing the combined vibration direction not to be in the vertical direction, and the design of the guide post 5 can prevent the combined vibration from deviating from the vertical direction.

[0046] It should be noted that in this embodiment, the ultrasonic transducer 31, the core rod ultrasonic transducer 42, and the wedge block 1 can use hard aluminum alloys, such as aluminum alloys of grades 6061 or 2024, etc.; the guide post 5, the support, and the rear cover can use alloy steels, such as 2Cr13, etc.; the drawing die 2 can use tungsten-based alloys, etc.; the core rod 41 uses alloy steels, such as 4Cr5MoSiV, 40Cr, etc.; the end cover 6 uses aluminum alloys, such as aluminum alloys of grades 6061 or 2024, etc.

[0047] The thin-walled microtube drawing device according to this embodiment has the following beneficial effects: Through the coordinated action of two external die ultrasonic transducer mechanisms and a mandrel ultrasonic transducer mechanism, a vibration field is provided for the drawing die during the drawing forming process. Compared with the vertical drawing process of traditional technology, the deformation amount per pass is increased, the micro-flow of the material is promoted, the initiation of local cracks in the micro-tube is reduced, and finally the purpose of efficiently preparing thin-walled micro-tubes with a short process is achieved. Specifically: 1. Through the coordination of two external die ultrasonic transducer mechanisms and a mandrel ultrasonic transducer mechanism, the friction force and the forming force between the drawn workpiece and the drawing die can be reduced, the forming ability and surface quality of the micro-tube material can be improved, and while reducing the wall thickness of the micro-tube, the number of processing passes can be further reduced.

[0048] 2. During the forming process of the micro-tube, through the two external die ultrasonic transducer mechanisms and the mandrel ultrasonic transducer mechanism, the stress state of the drawing die is changed from tensile stress to compressive stress and shear stress, that is, the drawing process is converted into a forging process. The high-frequency vibration of the drawing die and the mandrel causes periodic compaction and relaxation between the micro-tube material and the die and the mandrel. High-frequency microscopic plastic flow occurs on the surface of the micro-tube material, promoting the deformation of the micro-tube material in the compression zone, and finally reducing the risk of the micro-tube being pulled and broken.

[0049] 3. The contact stress between the surface of the micro-tube and the die and the mandrel decreases or even becomes zero, which is beneficial to the infiltration of lubricating oil and the maintenance of the lubrication state, effectively reducing the friction force and further reducing the initiation of surface microscopic cracks caused by friction.

[0050] 4. The grain boundaries or the interfaces of the second-phase particles of the micro-tube absorb the energy of the high-frequency vibration, resulting in an increase in the internal energy of the local microscopic region, reducing the energy barrier that needs to be overcome for dislocation movement, promoting dislocation movement, and finally reducing the deformation resistance.

[0051] Example 2 As Figures 1 to 9 shown, this embodiment provides a method for drawing a thin-walled micro-tube. Among them, the above device is used to draw the thin-walled micro-tube, including the following content: Press the drawing die tightly to the bottom of the end cover of the wedge block; After installing the device on the linear motion platform, remove the end cover, and then the micro-tube can be inserted and pulled out. The linear motion platform includes a ball screw slide, an electric push rod or a hydraulic cylinder push rod; Flatten the front end of the micro-tube to reduce the front-end diameter, then sleeve it onto the mandrel, and re-insert it into the through-hole of the wedge block until it reaches inside the drawing die; Fix the flattened small head on the linear motion platform; Start the power supply, and according to the working parameters of the ultrasonic transducer and the mandrel ultrasonic transducer input by the device, the working parameters include: working frequency, amplitude, and phase angle; Select different working modes according to the input working parameters, where the working modes include a non-vibrating mode, a co-directional vibrating mode, and a counter-directional vibrating mode. Start the linear motion platform, set the speed of the linear motion platform to draw the microtubule to complete the drawing operation of the thin-walled microtubule.

[0052] This embodiment provides the following analysis process to verify the effect of the present invention: Construct a mathematical model. The two ultrasonic transducers 31 have the same motion trajectory and vibrate at an included angle of 45° to 75°. Assume that the motion trajectory equation of each ultrasonic transducer is: Therefore, the motion trajectory equation of the two ultrasonic transducers superimposed on the wedge block is: Assume that the motion trajectory equation of the core rod ultrasonic transducer is: Where represents the amplitudes of the two ultrasonic transducers, represents the amplitude of the core rod ultrasonic transducer, where = = are the angular frequencies of the ultrasonic transducer and the core rod ultrasonic transducer respectively, represents the frequency of the ultrasonic transducer, represents the frequency of the core rod ultrasonic transducer, represents the workpiece processing time, represents the phase angle of the ultrasonic transducer, represents the phase angle of the core rod ultrasonic transducer, represents the displacements of the two ultrasonic transducers, represents the displacement of the wedge block 1, represents the displacement of the core rod ultrasonic transducer.

[0053] The ultrasonic transducer and the core rod ultrasonic transducer can vibrate at the same frequency, amplitude, and phase. This embodiment provides the following working modes. It should be noted that only several common vibration modes are shown below, and the working modes of the present invention include but are not limited to these several working modes.

[0054] First, when the vibration frequencies of the ultrasonic transducer and the core rod ultrasonic transducer are the same, different amplitudes can be input to the ultrasonic transducer and the core rod ultrasonic transducer, and the phase difference is set, that is, , and at this time takes values from 0° to 180°.

[0055] When ​​​​When the drawing die and the core rod ultrasonic transducers move in the same direction, the drawing die and the core rod vibrate in the same direction at this time; When the instantaneous velocity directions of the drawing die and the core rod ultrasonic transducers are opposite, that is, they vibrate in the reverse direction. At this time, the drawing die and the core rod vibrate in the reverse direction.

[0056] Second, when the vibration frequencies of the two are different, or ( is an even number). If is an odd number, the thin-walled microtube drawing device cannot obtain a stable vibration drawing state, that is, there is irregular movement, and this is irregular vibration at this time.

[0057] Third, when the vibration frequencies of the two are in multiples, different amplitudes can also be input to the ultrasonic transducer and the core rod ultrasonic transducer to obtain different vibration modes.

[0058] Connect two external ultrasonic power supplies to the thin-walled microtube drawing device in Embodiment 1. The operating frequency of the ultrasonic power supply is 19 kHz to 24 kHz. One of them drives the ultrasonic transducer 31. It should be noted that at this time, the two ultrasonic transducers 31 need to be connected in parallel so that their operating frequencies, amplitudes, and phase angles are the same. The other is used to drive the core rod ultrasonic transducer 42. The effective value of the driving voltage of the ultrasonic power supply is 0 V to 220 V.

[0059] Turn on the power supply, perform finite element vibration drawing simulation, and calculate the drawing force and stress nephogram in the non-vibration mode and three different vibration modes.

[0060] Adopt the axisymmetric model finite element simulation analysis as shown in Figure 7 . The respective boundary conditions in the non-vibration mode and three different vibration modes are described below: ① Non-vibration mode: Both the core rod and the drawing die are completely fixed, and the microtube drawing speed is 1 mm / s.

[0061] ② Boundary conditions for three different vibration modes: Reverse vibration, phase angle : The vibration frequencies of both the core rod and the drawing die are 20 kHz, the amplitudes are both 10 , the microtube drawing speed is 1 mm / s, and the amplitude curve is as shown in Figure 5 (a).

[0062] When the vibration frequencies are in multiples, 芯杆 外模 , 芯杆 外模: The core rod frequency is 20 kHz, the frequency of the drawing die is 10 kHz, and the amplitude of the core rod is 20 , and the amplitude of the drawing die is 10 . The drawing speed of the microtube is 1 mm / s, and the amplitude curve is as Figure 6 shown

[0063] Forward vibration, phase angle : The vibration frequencies of both the core rod and the drawing die are 20 kHz, and the amplitudes are both 10 . The drawing speed of the microtube is 1 mm / s, and the amplitude curve is as Figure 5 shown in (b) of

[0064] As Figure 8 shown is the general schematic diagram of the drawing force under different drawing conditions. According to Figure 8 , it can be seen that the average drawing force of non-vibrating drawing is between 1400 N and 1500 N, and the average drawing force of vibrating drawing is between 500 N and 600 N. The stress of vibrating drawing is much lower than that of non-vibrating drawing

[0065] As Figure 9 and Figure 10 shown, introducing high-frequency vibration can cause periodic extrusion and relaxation on the surface of the microtube, drawing force oscillation, and stress reduction. Among them Figure 9 , (a) in Figure 9 is the partial schematic diagram of the vibration drawing stress at the same moment in the non-vibrating mode. Among them Figure 9 , (b) in Figure 9 is the partial schematic diagram of the vibration drawing stress at the same moment in the reverse vibration mode. Among them , (c) in Figure 10 is the partial schematic diagram of the vibration drawing stress at the same moment when the vibration frequencies are in multiples. Among them Figure 10 , (d) in Figure 10 is the partial schematic diagram of the vibration drawing stress at the same moment in the forward vibration, phase angle Figure 10 mode ;

[0066] In summary, through finite element drawing simulation analysis, it can be known that the thin-walled microtube drawing device and its drawing method based on the present invention can effectively reduce the drawing force and stress of microtube drawing. Compared with the vertical drawing process of traditional technology, the deformation amount per pass is increased, the microscopic flow of materials is promoted, the generation of local cracks in microtubes is reduced, and finally the purpose of efficiently preparing thin-walled microtubes with a short process is achieved.

[0067] The thin-walled microtube drawing device and its drawing method according to this embodiment have the following beneficial effects: 1. Through the cooperation of the two outer die ultrasonic transducer mechanisms and the mandrel ultrasonic transducer mechanism, the friction between the drawn workpiece and the drawing die and the forming force of drawing can be reduced, the forming ability and surface quality of the microtube material can be improved, and while reducing the wall thickness of the microtube, the number of processing passes can be further reduced.

[0068] 2. During the microtube forming process, through the two outer die ultrasonic transducer mechanisms and the mandrel ultrasonic transducer mechanism, the stress state of the drawing die is changed from tensile stress to compressive stress and shear stress, that is, from drawing processing to forging processing. The high-frequency vibration of the drawing die and the mandrel causes periodic pressing and relaxation between the microtube material and the die and the mandrel. High-frequency microscopic plastic flow occurs on the surface of the microtube material, promoting the deformation of the microtube material in the compression zone, and finally reducing the risk of the microtube being pulled and broken.

[0069] 3. The contact stress between the microtube surface and the die and the mandrel decreases or even becomes zero, which is beneficial to the infiltration of lubricating oil and the maintenance of the lubrication state, effectively reduces the friction force, and further reduces the generation of surface microscopic cracks caused by friction.

[0070] 4. The grain boundaries or the interfaces of the second-phase particles of the microtube absorb the energy of high-frequency vibration, resulting in an increase in the internal energy of the local microscopic region, reducing the energy barrier that needs to be overcome for dislocation movement, promoting dislocation movement, and finally reducing the deformation resistance.

[0071] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0072] In the description of this specification, the descriptions with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example.

[0073] Obviously, the described embodiments are only a part of the embodiments of this application, rather than all embodiments. The mention of "embodiment" in this context means that the specific features, structures, or characteristics described in connection with the embodiment can be included in at least one embodiment of this application. The appearance of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. Those skilled in the art can explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0074] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A thin-walled microtube drawing device, characterized in that, Installed on a moving platform, the device includes: A wedge block (1), including: A first mounting portion (10) provided with a through hole (101) and two limiting holes (102); A second mounting portion (11) mounted on the surface of the first mounting portion (10) and communicating with the through hole (101), the second mounting portion (11) having a plurality of stepped portions (110); A drawing die (2) embedded in the stepped portion (110), the drawing die (2) having a forming cavity (21); Two outer die ultrasonic transducer mechanisms (3) connected to the first mounting portion (10) for providing a vibration field for the drawing die (2) during the drawing forming process, the forging stress of the vibration field forming a certain angle with the parallel central axis direction of the thin-walled microtube; A core rod ultrasonic transducer mechanism (4) having a core rod (41), the core rod (41) passing through the through hole (101) and extending into the forming cavity (21), having a gap with the drawing die (2); A guide post (5) mounted on a guide post support (7) and adapted to the limiting hole (102); An end cap (6) connected to the second mounting portion (11) and in contact with the drawing die (2).

2. The thin-walled microtube drawing device according to claim 1, characterized in that, The second mounting portion (11) includes: A plurality of waist-shaped holes (111) spirally distributed in a single direction on the tube wall of the second mounting portion (11).

3. The thin-walled microtube drawing device according to claim 2, characterized in that, The direction includes a left-handed spiral vibration direction and a right-handed spiral vibration direction.

4. The thin-walled microtube drawing device according to claim 2, characterized in that, The plurality of waist-shaped holes (111) are located at the same height on the tube wall of the second mounting portion (11).

5. The thin-walled microtube drawing device according to claim 4, wherein, The waist-shaped hole (111) forms a 45° angle with the horizontal direction of the tube wall.

6. The thin-walled microtube drawing device according to claim 1, characterized in that, The outer die ultrasonic transducer mechanism (3) is symmetrically arranged about the central axis of the core rod (41).

7. The thin-wall microtube drawing device according to claim 6, characterized in that, The included angle between the outer die ultrasonic transducer mechanism (3) and the core rod (41) ranges from 45° to 75°.

8. The thin-walled microtube drawing device according to claim 7, characterized in that, The outer die ultrasonic transducer mechanism (3) includes: An ultrasonic transducer (31) connected to the first mounting portion (10), the ultrasonic transducer (31) having a first rear cover (311), and a plurality of first piezoelectric wafers (312) are provided between the front end of the ultrasonic transducer (31) main body and the first rear cover (311).

9. The thin-walled microtube drawing device according to claim 1, wherein, The core rod ultrasonic transducer mechanism (4) includes: A core rod (41), a core rod ultrasonic transducer (42) connected to the core rod (41), the core rod ultrasonic transducer (42) having a second rear cover (421), and a plurality of second piezoelectric wafers (422) are provided between the front end of the core rod ultrasonic transducer (42) main body and the second rear cover (421).

10. A method for drawing a thin-walled microtube, characterized in that, Using the device according to any one of claims 1 to 9 to draw a thin-walled microtube, including the following steps: Press the drawing die tightly to the bottom of the end cap of the wedge block; After installing the device on the linear motion platform, remove the end cap; Flatten the front end of the microtube to reduce the front end diameter and then sleeve it onto the core rod, and reinsert it into the through hole of the wedge block until it reaches the inside of the drawing die; Fix the flattened small end on the linear motion platform; Turn on the power supply and input the working parameters of the ultrasonic transducer and the mandrel ultrasonic transducer according to the device. The working parameters include: working frequency, amplitude, and phase angle; Select different working modes according to the input working parameters. The working modes include non-vibration mode, co-directional vibration mode, and reverse vibration mode; Start the linear motion platform, set the speed of the linear motion platform to draw the microtube to complete the drawing operation of the thin-walled microtube.

Images