A free bending stress regulation device and method based on ring-type ultrasonic excitation

Abstract

The application discloses a free bending stress regulation device and method based on annular ultrasonic excitation, and belongs to the technical field of pipe free bending forming, and comprises an annular mounting seat, which is located at the front end of a guide mechanism in a free bending device and is provided with a central through hole in the middle; a plurality of ultrasonic excitation units are uniformly distributed on the annular mounting seat in the circumferential direction; a plurality of vibration transmission pieces correspond to the ultrasonic excitation units one by one, and the corresponding ultrasonic excitation units and vibration transmission pieces form a group of ultrasonic action assemblies; an ultrasonic power supply is electrically connected with the ultrasonic excitation units and is used for driving the ultrasonic excitation units to generate ultrasonic vibration. The ultrasonic action assemblies are arranged at the front end of the guide mechanism in the free bending device, and the ultrasonic action assemblies at corresponding positions can work according to the current bending direction, the regulation and control of the stretching concentration on the outer side and the compression accumulation on the inner side of the pipe during bending are realized, and the defects, such as wrinkling, rupture, wall thickness thinning and cross-section distortion, in the free bending process can be effectively reduced.

Description

Technical Field

[0001] This invention belongs to the field of free bending forming technology of pipes, specifically relating to a free bending stress control device and method based on circumferential ultrasonic excitation. Background Technology

[0002] Free bending forming technology is one of the important methods for achieving flexible manufacturing of complex bent pipe components. This technology combines continuous pipe feeding with spatial orientation adjustment of the bending die, allowing the pipe to enter the bending transition section near the exit of the guide mechanism and undergo continuous bending deformation under the constraint of the bending die. Compared with traditional bending and pressing processes, free bending forming does not require frequent changes of special dies for different bending radii and directions. It can achieve continuous forming of two-dimensional, three-dimensional, and variable curvature pipe components, and has advantages such as high flexibility and strong adaptability.

[0003] However, during the free bending process of the pipe, the area between the guide mechanism outlet and the bending die is the main deformation zone. Within this zone, the circumferential stress state of the pipe cross-section is significantly uneven: the outer side of the pipe bend mainly bears tensile stress, which easily leads to excessive wall thinning and cracking; the inner side of the pipe bend mainly bears compressive stress, which easily leads to material accumulation, local instability, and wrinkling; the two sides of the pipe may also experience ellipticization or distortion of the cross-section due to uneven circumferential material flow. These defects are even more pronounced in thin-walled pipes, high-strength material pipes, and complex spatial bends.

[0004] Currently, methods to reduce the aforementioned defects typically include adjusting the feeding speed, optimizing the guide clearance, changing the bending die offset, improving lubrication conditions, or adding subsequent straightening processes. While these methods can improve forming quality to some extent, they mainly rely on adjusting overall process parameters and lack targeted control over the stress state on the outer and inner sides of the pipe bend, making it difficult to simultaneously suppress outer cracking and inner wrinkling.

[0005] Ultrasonic vibration-assisted forming can reduce friction, improve local material flow, and enhance forming stability. If ultrasonic excitation can be arranged at the front end of the free bending guide mechanism or in the guide exit area, and the ultrasonic excitation units at different positions around the pipe can be selectively operated according to the bending direction, the tensile state on the outer bending side and the compressive state on the inner bending side can be controlled after the pipe enters the bending transition section, thereby reducing defects such as wrinkling, cracking, and cross-sectional distortion.

[0006] Based on this, this application proposes a free bending stress control device and method based on circumferential ultrasonic excitation. By arranging an ultrasonic action component at the front end of the guide mechanism of the free bending equipment and applying ultrasonic vibration to different positions in the circumference of the pipe according to the current bending direction, the tension concentration on the outer side and the compression accumulation on the inner side of the pipe bend can be controlled, which can effectively reduce defects such as wrinkling, cracking, wall thickness reduction and cross-sectional distortion during the free bending process. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a free bending stress control device based on circumferential ultrasonic excitation.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A free bending stress control device based on circumferential ultrasonic excitation, comprising: An annular mounting base is located at the front end of the guide mechanism in the free bending device, and a central through hole for the pipe to pass through is provided in the middle of the annular mounting base; Several ultrasonic excitation units are evenly distributed on the annular mounting base along the circumference; Several vibration transmission components correspond one-to-one with ultrasonic excitation units. One end of each vibration transmission component is connected to the ultrasonic excitation unit, and the other end is in contact with the outer wall of the pipe. The corresponding ultrasonic excitation unit and vibration transmission component form a set of ultrasonic action components. An ultrasonic power supply, electrically connected to the ultrasonic excitation unit, is used to drive the ultrasonic excitation unit to generate ultrasonic vibrations. The ultrasonic excitation unit can selectively operate according to the current bending direction of the pipe, so that the outer side of the pipe bend, the inner side of the bend, and the circumferential lateral area between the outer side of the bend and the inner side of the bend are subjected to ultrasonic excitation at different positions and intensities.

[0009] Preferably, the outer side of the bend, the inner side of the bend, and the circumferential lateral region between the outer side and the inner side of the bend in the current bending direction of the pipe all correspond to the corresponding ultrasonic action components.

[0010] Preferably, the ultrasonic excitation unit includes a connected ultrasonic transducer and an ultrasonic amplitude transformer.

[0011] Preferably, the vibration transmission component is any one or more combinations of a vibration head, a vibration contact block, a guide block, a rolling contact component, and an elastic clamping component.

[0012] Preferably, the number of ultrasonic excitation units is at least four and is an even number.

[0013] The present invention also provides a method for controlling free bending stress based on circumferential ultrasonic excitation.

[0014] A method for controlling free bending stress based on circumferential ultrasonic excitation is implemented by means of the following steps: Step 1: Install the annular mounting base at the front end of the guide mechanism of the free bending equipment, so that the pipe passes through the central through hole of the annular mounting base; Step 2: Based on the bending direction of the pipe, determine the outer side, inner side, and circumferential lateral area of ​​the section of pipe to be bent. Step 3: Determine the corresponding ultrasonic action components for the outer side of the bend, the inner side of the bend, and the circumferential lateral region, as the working ultrasonic action components; Step 4: Determine the ultrasonic amplitude of each working ultrasonic component; Step 5: After the pipe is fed and enters the bending transition section, start each working ultrasonic component to apply ultrasonic vibration to the outer periphery of the pipe.

[0015] Preferably, step 3 includes the following sub-steps: Step 31: The ends of all vibration transmission components away from the ultrasonic excitation unit are located on the same plane, and the portion of this plane located inside the outer wall of the tube is a circular surface. Step 32: Determine the intersection point of the pipe's central axis and the circular surface. Determine the first straight line along the pipe's bending direction through the intersection point. The two intersection points of the first straight line and the circular surface outline are the first intersection point and the second intersection point. The first intersection point is located on the outer side of the pipe section to be bent, and the second intersection point is located on the inner side of the pipe section to be bent. A second line perpendicular to the first line is determined through the intersection point, and the two intersection points of the second line with the circular outline are the third and fourth intersection points; Step 33: Select one or two ultrasonic action components closest to the first intersection point as the working ultrasonic action components corresponding to the outer side of the bend; Use the one or two ultrasonic components closest to the second intersection point as the working ultrasonic components corresponding to the inner side of the bend; Use the one or two ultrasonic action components closest to the third intersection point as the working ultrasonic action components corresponding to the circumferential lateral region on one side; Use the one or two ultrasonic action components closest to the fourth intersection point as the working ultrasonic action components corresponding to the other side circumferential lateral region.

[0016] Preferably, in step 4, the formula for determining the ultrasonic amplitude of each working ultrasonic component is as follows: ; ; ; in, The ultrasonic amplitude corresponds to the ultrasonic action component working on the curved outer side; The excitation proportionality coefficient corresponding to the outer side of the bend is 0.1 to 5; This corresponds to the ultrasonic amplitude of the ultrasonic action component working on the inner side of the bend; The excitation proportionality coefficient corresponding to the inner side of the bend is 0.1 to 5; The ultrasonic amplitude corresponds to the ultrasonic action component operating in the circumferential lateral region; The excitation proportionality coefficient corresponding to the circumferential lateral region takes a value of 0.1 to 5; The value is not greater than , The value; Basic ultrasonic amplitude; The yield strength of the pipe material; The elastic modulus of the pipe material; The outer diameter of the pipe; The target bending radius.

[0017] Preferably, when the outer bend of the pipe is prone to wall thinning or cracking, This enhances the ultrasonic amplitude corresponding to the ultrasonic action component working on the curved outer side; When compression wrinkling is prone to occur on the inner bend side of the pipe. To enhance the ultrasonic amplitude of the ultrasonic component corresponding to the inner side of the bend; When the cross-section of the pipe is prone to distortion, increase The value of enhances the ultrasonic amplitude of the ultrasonic component corresponding to the circumferential lateral region.

[0018] Preferably, the ultrasonic frequency of the working ultrasonic actuator is 15kHz to 80kHz, and the basic ultrasonic amplitude is... The value ranges from 1μm to 50μm.

[0019] The beneficial effects of this invention are: (1) By arranging an ultrasonic component at the front end of the guide mechanism of the free bending device, the pipe is subjected to high-frequency micro-amplitude ultrasonic vibration after entering the bending transition section, which can reduce the local frictional resistance between the pipe and the guide mechanism and improve the material flow state of the pipe in the bending transition section. (2) By arranging several ultrasonic action components along the circumference of the pipe, the ultrasonic excitation effect can be distributed around the circumference of the pipe, and the ultrasonic action components at the corresponding positions can be selected to work according to the current bending direction, so as to realize the control of the tension concentration on the outside of the pipe bending and the compression accumulation on the inside, which can effectively reduce defects such as wrinkling, cracking, wall thickness reduction and cross-sectional distortion during free bending. (3) In this invention, ultrasonic excitation corresponding to the outer side of the bend can reduce the risk of tensile concentration and breakage on the outer side of the bend, ultrasonic excitation corresponding to the inner side of the bend can reduce the risk of compression accumulation and wrinkling on the inner side of the bend, and ultrasonic excitation corresponding to the circumferential lateral region can improve cross-sectional distortion. (4) This invention can be installed as an additional functional module at the front end of the guide mechanism of the existing free bending equipment without changing the original feeding and bending die deflection method of the free bending equipment. It has the advantages of simple structure, convenient implementation, strong adaptability and high forming quality. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0021] Figure 1 This is a schematic diagram of the structure of the free bending stress control device based on circumferential ultrasonic excitation of the present invention installed at the front end of the guide mechanism of the free bending equipment; Figure 2 This is a schematic diagram of the ultrasonic action component arranged along the circumference of the pipe in this invention; Figure 3 This is a schematic diagram of the structure of the free bending stress control device based on circumferential ultrasonic excitation of the present invention, which is arranged along the circumference of the pipe during bending. Figure 4 This is a schematic diagram of determining the working ultrasonic action component in Embodiment 3 of the present invention; Figure 5 This is a schematic diagram of the working ultrasonic action component being determined during the forming of the first and second curved sections in Embodiment 4 of the present invention; in: 1. Annular mounting base; 2. Ultrasonic excitation unit; 3. Vibration transmission component; 4. Ultrasonic power supply; 5. Guide mechanism; 6. Bending mold; 7. Pipe; 8. Circular surface; 9. Intersection point; 10. First straight line; 11. First intersection point; 12. Second intersection point; 13. Second straight line; 14. Third intersection point; 15. Fourth intersection point. Detailed Implementation

[0022] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0023] 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 exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. 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.

[0024] In this invention, terms such as "upper," "lower," "bottom," and "top" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are merely relational terms determined for the convenience of describing the structural relationship of the various components or elements of this invention, and do not specifically refer to any component or element in this invention, and should not be construed as limiting this invention.

[0025] In this invention, terms such as "connected" and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of these terms in this invention based on the specific circumstances, and they should not be construed as limitations on the invention.

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] Example 1: like Figures 1-3 As shown, a free bending stress control device based on circumferential ultrasonic excitation includes... The annular mounting base 1 is located at the front end of the guide mechanism 5 in the free bending device, that is, in the guide outlet area of ​​the guide mechanism 5, wherein the front end of the guide mechanism 5 faces the bending die 6. Figure 1 The diagram shown is a schematic of the annular mounting base 1 located at the front end of the guide mechanism 5. The guide mechanism 5 is used to guide the pipe 7, and the bending die 6 is used to bend the pipe 7. When the pipe 7 is fed, the pipe 7 moves from the rear end to the front end of the guide mechanism 5. The free bending device and its guide mechanism 5 and bending die 6 are existing technologies, and their specific structures will not be described in detail here. The annular mounting base 1 is fixedly connected to the guide mechanism 5, detachably connected, or integrally formed. For example, the annular mounting base 1 can be threaded to the guide outlet of the guide mechanism 5. The annular mounting base 1 has a central through hole in the middle for the pipe 7 to pass through. Several ultrasonic excitation units 2 are evenly distributed on the annular mounting base 1 along the circumferential direction; Several vibration transmission components 3 correspond one-to-one with ultrasonic excitation units 2. One end of each vibration transmission component 3 is connected to the ultrasonic excitation unit 2 and the other end is in contact with the outer wall of the pipe 7. The corresponding ultrasonic excitation unit 2 and vibration transmission component 3 form a set of ultrasonic action components. The ultrasonic power supply 4 is electrically connected to the ultrasonic excitation unit 2 and is used to drive the ultrasonic excitation unit 2 to generate ultrasonic vibration. The ultrasonic excitation unit 2 can selectively operate according to the current bending direction of the pipe 7, so that the outer side of the pipe bend, the inner side of the bend, and the circumferential lateral area between the outer side of the bend and the inner side of the bend are subjected to ultrasonic excitation at different positions and intensities, thereby regulating the circumferential stress state of the pipe 7 during the free bending process.

[0028] Preferably, the outer side of the bend, the inner side of the bend, and the circumferential lateral region between the outer side and the inner side of the bend in the current bending direction of the pipe 7 all correspond to corresponding ultrasonic action components. Specifically, the ultrasonic action component corresponding to the outer side of the bend of the pipe 7 is used to reduce tensile concentration and the risk of breakage on the outer bend side; the ultrasonic action component corresponding to the inner side of the bend of the pipe 7 is used to reduce compression buildup and the risk of wrinkling on the inner bend side; and the ultrasonic action component corresponding to the circumferential lateral region of the pipe 7 is used to reduce cross-sectional distortion.

[0029] Preferably, the ultrasonic excitation unit 2 includes a connected ultrasonic transducer and an ultrasonic amplitude transformer.

[0030] Preferably, the vibration transmission component 3 is any one or more combinations of a vibration head, a vibration contact block, a guide block, a rolling contact component, and an elastic clamping component.

[0031] Preferably, the number of ultrasonic excitation units 2 is at least 4 and is an even number, specifically 4, 6, 8, 12 or 16.

[0032] Example 2: A method for controlling free bending stress based on circumferential ultrasonic excitation, implemented using the free bending stress control based on circumferential ultrasonic excitation in Example 1, includes the following steps: Step 1: Install the annular mounting base 1 at the front end of the guide mechanism 5 of the free bending device, so that the pipe 7 passes through the central through hole of the annular mounting base 1. Step 2: Based on the bending direction of pipe 7, determine the outer side, inner side, and circumferential lateral area of ​​the section of pipe to be bent. Step 3: Determine the corresponding ultrasonic action components for the outer side of the bend, the inner side of the bend, and the circumferential lateral region, as the working ultrasonic action components; Step 4: Determine the ultrasonic amplitude of each working ultrasonic component; Step 5: After the pipe 7 is fed and enters the bending transition section, each working ultrasonic component is activated to apply ultrasonic vibration to the outer periphery of the pipe 7. In the subsequent process, the ultrasonic components work synchronously with the feeding process of the pipe 7, so that the pipe 7 is continuously subjected to circumferential ultrasonic excitation after entering the bending transition section.

[0033] Ultrasonic vibration improves the contact friction state between the pipe 7 and the guide mechanism 5, as well as the circumferential material flow state of the pipe, thereby reducing wrinkling, cracking, excessive wall thinning, and cross-sectional distortion defects during the free bending process of the pipe.

[0034] During the two-dimensional free bending forming process, the outer side of the bend, the inner side of the bend, and the circumferential lateral region remain unchanged in the 7-circumferential upward position of the tube, and the corresponding working ultrasonic action components work continuously or intermittently.

[0035] During the free bending and forming process in three-dimensional space, when the bending direction of the pipe 7 changes, the positions of the outer side of the bend, the inner side of the bend, and the circumferential lateral region in the circumferential direction of the pipe 7 change accordingly, and the ultrasonic action component at the corresponding circumferential position is switched as the working ultrasonic action component.

[0036] Preferably, step 3 includes the following sub-steps: Step 31: The ends of all vibration transmission components 3 away from the ultrasonic excitation unit 2 are located on the same plane, and the part of this plane located inside the outer wall of the tube 7 is a circular surface 8; Step 32: Determine the intersection point 9 of the central axis of the pipe 7 and the circular surface 8. Determine the first straight line 10 along the bending direction of the pipe 7 through the intersection point 9. The two intersection points of the first straight line 10 and the outline of the circular surface 8 are the first intersection point 11 and the second intersection point 12. The first intersection point 11 is located on the outside of the bend of the section of the pipe 7 to be bent, and the second intersection point 12 is located on the inside of the bend of the section of the pipe 7 to be bent. The second line 13, which is perpendicular to the first line 10, is determined through the intersection point 9. The two intersection points of the second line 13 and the outline of the circular surface 8 are the third intersection point 14 and the fourth intersection point 15. Step 33: Select one or two ultrasonic action components closest to the first intersection point 11 as the working ultrasonic action components corresponding to the outer side of the bend; Use the one or two ultrasonic action components closest to the second intersection point 12 as the working ultrasonic action components corresponding to the inner side of the bend; Use the one or two ultrasonic action components closest to the third intersection point 14 as the working ultrasonic action components corresponding to the circumferential lateral region on one side; Use the one or two ultrasonic action components closest to the fourth intersection point 15 as the working ultrasonic action components corresponding to the other side circumferential lateral region.

[0037] In this application, when the intersection point is located between two corresponding ultrasonic action components, and one of the ultrasonic action components is closer to the intersection point, the closer ultrasonic action component is designated as the working ultrasonic action component; when the intersection point is located between two corresponding ultrasonic action components, and the two ultrasonic action components are at the same distance from the intersection point, both ultrasonic action components are designated as working ultrasonic action components; when the intersection point is directly opposite an ultrasonic action component, the directly opposite ultrasonic action component is designated as the working ultrasonic action component.

[0038] Preferably, in step 4, the formula for determining the ultrasonic amplitude of each working ultrasonic component is as follows: ; ; ; in, The ultrasonic amplitude corresponds to the ultrasonic action component working on the curved outer side; The excitation proportionality coefficient corresponding to the outer side of the bend is 0.1 to 5; This corresponds to the ultrasonic amplitude of the ultrasonic action component working on the inner side of the bend; The excitation proportionality coefficient corresponding to the inner side of the bend is 0.1 to 5; The ultrasonic amplitude corresponds to the ultrasonic action component operating in the circumferential lateral region; The excitation proportionality coefficient corresponding to the circumferential lateral region takes a value of 0.1 to 5; The value is not greater than , The value; Basic ultrasonic amplitude; The yield strength of pipe 7 is the material yield strength. The elastic modulus of pipe 7; The outer diameter of pipe 7; The target bending radius.

[0039] Preferably, when the outer bend of the pipe 7 is prone to wall thinning or cracking, This enhances the ultrasonic amplitude corresponding to the ultrasonic action component working on the curved outer side; When compression wrinkling is prone to occur on the inner bend side of pipe 7 To enhance the ultrasonic amplitude of the ultrasonic component corresponding to the inner side of the bend; When the 7-section of the pipe is prone to distortion, increase Specifically, the value of is in the range of 0.1 to 5 and satisfies . The value is not greater than , Increase the value under the condition of The value of enhances the ultrasonic amplitude of the ultrasonic component corresponding to the circumferential lateral region.

[0040] Preferably, the ultrasonic frequency of the working ultrasonic actuator is 15kHz to 80kHz, and the basic ultrasonic amplitude is... The value ranges from 1μm to 50μm.

[0041] Example 3: The implementation process of the free bending stress control method based on circumferential ultrasonic excitation of the present invention is illustrated using two-dimensional free bending of a circular tube as an example. The tube to be formed, 7, is a circular tube with an outer diameter of... The thickness is 20mm, the wall thickness is t=1.5mm, and the material yield strength is... The material's elastic modulus is 350 MPa. The target bending radius is 210 GPa. It is 60mm.

[0042] The annular mounting base 1 is installed at the front end of the guide mechanism 5 of the free bending equipment. The pipe 7 enters the bending transition section after passing through the central through hole of the annular mounting base 1. Six ultrasonic action components are evenly arranged around the circumference of the pipe 7 in the annular mounting base 1, and the circumferential angle between two adjacent ultrasonic action components is 60°.

[0043] During forming, according to the current bending direction, such as Figure 4 As shown, the first intersection point 11 is directly opposite an ultrasonic actuator, which is designated as the working ultrasonic actuator corresponding to the outer side of the bend. The second intersection point 12 is directly opposite an ultrasonic actuator, which is designated as the working ultrasonic actuator corresponding to the inner side of the bend. The third intersection point 14 and the fourth intersection point 15 are located at the midpoints of two ultrasonic actuators, respectively. Therefore, the two ultrasonic actuators on either side of the third intersection point 14 are designated as working ultrasonic actuators corresponding to the circumferential and lateral regions on that side, and the two ultrasonic actuators on either side of the fourth intersection point 15 are designated as working ultrasonic actuators corresponding to the circumferential and lateral regions on that side. That is, in this embodiment, all six ultrasonic actuators are used as working ultrasonic actuators.

[0044] In this embodiment, the basic ultrasonic amplitude The value is 8μm. The value is 1.2. The value is 1.0. The value is set to 0.5. The ultrasonic amplitude of each working ultrasonic component is then determined as follows: ; ; ; Among them, ultrasonic amplitude , , The units are all in μm.

[0045] As shown in the above calculations, under the conditions of the selected material and bending radius in this embodiment, the ultrasonic amplitude required for the outer bending region is slightly larger than that for the inner bending region, while the ultrasonic amplitude required for the circumferential lateral region is the smallest. In actual forming, the ultrasonic amplitude corresponding to the working ultrasonic component on the outer bending region can be set to 8.0 μm to 8.1 μm, the ultrasonic amplitude corresponding to the working ultrasonic component on the inner bending region can be set to 8.0 μm, and the ultrasonic amplitude corresponding to the working ultrasonic component in the circumferential lateral region can be set to 8.0 μm. Each working ultrasonic component operates continuously or intermittently.

[0046] During the forming process, the tube 7 is fed axially and enters the bending transition section. The ultrasonic action component corresponding to the outer side of the bend applies ultrasonic vibration to the outer side of the tube 7 to reduce tensile concentration and wall thickness reduction on the outer bend side; the ultrasonic action component corresponding to the inner side of the bend applies ultrasonic vibration to the inner side of the tube 7 to reduce compression buildup and wrinkling on the inner bend side; the ultrasonic action component corresponding to the circumferential lateral region applies auxiliary ultrasonic vibration to both sides of the tube 7 to improve cross-sectional distortion.

[0047] In this way, ultrasonic-assisted control of the stress state and material flow state of the bending transition section of the pipe can be achieved without changing the original feeding and bending die deflection methods of the free bending equipment.

[0048] Example 4: The implementation process of the free bending stress control method based on circumferential ultrasonic excitation of this invention is illustrated using the change in the spatial bending direction of a circular tube as an example. The tube to be formed, 7, is a circular tube with an outer diameter of... The thickness is 20mm, the wall thickness is t=1.5mm, and the material yield strength is... The material's elastic modulus is 350 MPa. The target bending radius is 210 GPa; it includes two consecutive bending sections, with the first bending section having a target bending radius of 210 GPa. The target bending radius of the second bending section is 60mm. The second bending section is 45mm long, and its bending direction is rotated 50° clockwise around the axis of the pipe 7 relative to the bending direction of the first bending section.

[0049] The annular mounting base 1 is installed at the front end of the guide mechanism 5 of the free bending equipment. The pipe 7 enters the bending transition section after passing through the central through hole of the annular mounting base 1. Eight ultrasonic action components are evenly arranged around the circumference of the pipe 7 on the annular mounting base 1. The circumferential angle between two adjacent ultrasonic action components is 45°. The positions of the eight ultrasonic action components are defined by the clockwise circumferential angle, with the uppermost ultrasonic action component at the 0° position. Along the clockwise direction, the positions of the remaining ultrasonic action components are 45°, 90°, 135°, 180°, 225°, 270°, and 315°, respectively.

[0050] When the first curved section is formed, as Figure 5As shown, the first intersection point 11 is directly opposite the ultrasonic component at the top 0° position, and the ultrasonic component at the 0° position is used as the working ultrasonic component corresponding to the outer side of the bend. The second intersection point 12 is directly opposite the ultrasonic component at the bottom 180° position, and the ultrasonic component at the 180° position is used as the working ultrasonic component corresponding to the inner side of the bend. The third intersection point 14 is directly opposite the ultrasonic component at the 90° position, and the ultrasonic component at the 90° position is used as the working ultrasonic component corresponding to the lateral region of that side. The fourth intersection point 15 is directly opposite the ultrasonic component at the 270° position, and the ultrasonic component at the 270° position is used as the working ultrasonic component corresponding to the lateral region of that side. In this embodiment, when the first bend segment is formed, four ultrasonic components are used as working ultrasonic components.

[0051] When the first curved section is formed, the basic ultrasonic amplitude The value is 8μm. The value is 1.2. The value is 1.0. The value is set to 0.5. Therefore, the ultrasonic amplitude of each working ultrasonic component during the forming of the first bending section is determined as follows: ; ; ; Among them, the ultrasonic amplitude corresponding to the formation of the first curved segment , , The units are all in μm.

[0052] When the second bending segment is formed, such as Figure 5As shown, the bending direction of the second bending segment rotates 50° clockwise around the axis of the pipe 7 relative to the bending direction of the first bending segment. That is, the first straight line 10 corresponding to the second bending segment rotates 50° clockwise around the axis of the pipe 7 relative to the first straight line 10 corresponding to the first bending segment. Therefore, during the formation of the second curved section, the first intersection 11 is located between the ultrasonic action components at the 45° position and the ultrasonic action components at the 90° position, and is closer to the ultrasonic action component at the 45° position. The ultrasonic action component at the 45° position is used as the working ultrasonic action component corresponding to the outer side of the bend. The second intersection 12 is located between the ultrasonic action components at the 225° position and the ultrasonic action components at the 270° position, and is closer to the ultrasonic action component at the 225° position. The ultrasonic action component at the 225° position is used as the working ultrasonic action component corresponding to the inner side of the bend. The third intersection 14 is located between the ultrasonic action components at the 135° position and the ultrasonic action components at the 180° position, and is closer to the ultrasonic action component at the 135° position. The ultrasonic action component at the 135° position is used as the working ultrasonic action component corresponding to the lateral region of that side. The fourth intersection 15 is located between the ultrasonic action components at the 315° position and the ultrasonic action components at the 0° position, and is closer to the ultrasonic action component at the 315° position. The ultrasonic action component at the 315° position is used as the working ultrasonic action component corresponding to the lateral region of that side. In this embodiment, when the second bending segment is formed, four ultrasonic action components are used as working ultrasonic action components.

[0053] When the second bending segment is formed, its bending radius is smaller than that of the first bending segment, increasing the risk of defects and affecting the basic ultrasonic amplitude. The value is 8μm. The value is 1.6. The value is 1.3. The value is set to 0.7. Therefore, the ultrasonic amplitude of each working ultrasonic component during the forming of the second bending section is determined as follows: ; ; ; Among them, the ultrasonic amplitude corresponding to the formation of the second curved segment , , The units are all in μm.

[0054] Therefore, during the forming of the second bending section, the ultrasonic amplitude of the ultrasonic component at the 45° position is set to 8.005 μm, the ultrasonic amplitude of the ultrasonic component at the 225° position is set to 8.004 μm, and the ultrasonic amplitude of the ultrasonic components at the 135° and 315° positions is set to approximately 8.002 μm.

[0055] This embodiment shows that in three-dimensional free bending, when the bending direction changes, it is not necessary to change the main structure of the free bending device. It is only necessary to switch the ultrasonic action components at the corresponding positions of the pipe 7 circumferentially according to the new bending direction, so that the ultrasonic excitation always acts on the outer, inner and circumferential lateral regions of the current bend, thereby realizing the dynamic control of the stress state during the spatial bending process.

[0056] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, they are not intended to limit the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A free bending stress control device based on circumferential ultrasonic excitation, characterized in that, include An annular mounting base is located at the front end of the guide mechanism in the free bending device, and a central through hole for the pipe to pass through is provided in the middle of the annular mounting base; Several ultrasonic excitation units are evenly distributed on the annular mounting base along the circumference; Several vibration transmission components correspond one-to-one with ultrasonic excitation units. One end of each vibration transmission component is connected to the ultrasonic excitation unit, and the other end is in contact with the outer wall of the pipe. The corresponding ultrasonic excitation unit and vibration transmission component form a set of ultrasonic action components. An ultrasonic power supply, electrically connected to the ultrasonic excitation unit, is used to drive the ultrasonic excitation unit to generate ultrasonic vibrations. The ultrasonic excitation unit can selectively operate according to the current bending direction of the pipe, so that the outer side of the pipe bend, the inner side of the bend, and the circumferential lateral area between the outer side of the bend and the inner side of the bend are subjected to ultrasonic excitation at different positions and intensities.

2. The free bending stress control device based on circumferential ultrasonic excitation as described in claim 1, characterized in that, The outer side of the current bending direction of the pipe, the inner side of the bending direction, and the circumferential lateral area between the outer side and the inner side of the bending direction all correspond to the corresponding ultrasonic action components.

3. The free bending stress control device based on circumferential ultrasonic excitation as described in claim 1, characterized in that, The ultrasonic excitation unit includes a connected ultrasonic transducer and an ultrasonic amplitude transformer.

4. The free bending stress control device based on circumferential ultrasonic excitation as described in claim 1, characterized in that, The vibration transmission component is any one or more combinations of a vibration head, a vibration contact block, a guide block, a rolling contact component, and an elastic clamping component.

5. The free bending stress control device based on circumferential ultrasonic excitation as described in claim 1, characterized in that, The number of ultrasonic excitation units is at least 4 and is an even number.

6. A method for controlling free bending stress based on circumferential ultrasonic excitation, implemented using the free bending stress control method based on circumferential ultrasonic excitation as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Install the annular mounting base at the front end of the guide mechanism of the free bending equipment, so that the pipe passes through the central through hole of the annular mounting base; Step 2: Based on the bending direction of the pipe, determine the outer side, inner side, and circumferential lateral area of ​​the section of pipe to be bent. Step 3: Determine the corresponding ultrasonic action components for the outer side of the bend, the inner side of the bend, and the circumferential lateral region, as the working ultrasonic action components; Step 4: Determine the ultrasonic amplitude of each working ultrasonic component; Step 5: After the pipe is fed and enters the bending transition section, start each working ultrasonic component to apply ultrasonic vibration to the outer periphery of the pipe.

7. The method for controlling free bending stress based on circumferential ultrasonic excitation as described in claim 6, characterized in that, Step 3 includes the following sub-steps: Step 31: The ends of all vibration transmission components away from the ultrasonic excitation unit are located on the same plane, and the portion of this plane located inside the outer wall of the tube is a circular surface. Step 32: Determine the intersection point of the pipe's central axis and the circular surface. Determine the first straight line along the pipe's bending direction through the intersection point. The two intersection points of the first straight line and the circular surface outline are the first intersection point and the second intersection point. The first intersection point is located on the outer side of the pipe section to be bent, and the second intersection point is located on the inner side of the pipe section to be bent. A second line perpendicular to the first line is determined through the intersection point, and the two intersection points of the second line with the circular outline are the third and fourth intersection points; Step 33: Select one or two ultrasonic action components closest to the first intersection point as the working ultrasonic action components corresponding to the outer side of the bend; Use the one or two ultrasonic components closest to the second intersection point as the working ultrasonic components corresponding to the inner side of the bend; Use the one or two ultrasonic action components closest to the third intersection point as the working ultrasonic action components corresponding to the circumferential lateral region on one side; Use the one or two ultrasonic components closest to the fourth intersection point as the working ultrasonic components corresponding to the other side circumferential lateral region.

8. The method for controlling free bending stress based on circumferential ultrasonic excitation as described in claim 6, characterized in that, In step 4, the formula for determining the ultrasonic amplitude of each working ultrasonic component is as follows: ； ； ； in, The ultrasonic amplitude corresponds to the ultrasonic action component working on the curved outer side; The excitation proportionality coefficient corresponding to the outer side of the bend is 0.1 to 5; This corresponds to the ultrasonic amplitude of the ultrasonic action component working on the inner side of the bend; The excitation proportionality coefficient corresponding to the inner side of the bend is 0.1 to 5; The ultrasonic amplitude corresponds to the ultrasonic action component operating in the circumferential lateral region; The excitation proportionality coefficient corresponding to the circumferential lateral region takes a value of 0.1 to 5; The value is not greater than , The value; Basic ultrasonic amplitude; The yield strength of the pipe material; The elastic modulus of the pipe material; The outer diameter of the pipe; The target bending radius.

9. The method for controlling free bending stress based on circumferential ultrasonic excitation as described in claim 8, characterized in that, When the outer bend of the pipe is prone to wall thinning or cracking This enhances the ultrasonic amplitude corresponding to the ultrasonic action component working on the curved outer side; When compression wrinkling is prone to occur on the inner bend side of the pipe. To enhance the ultrasonic amplitude of the ultrasonic component corresponding to the inner side of the bend; When the cross-section of the pipe is prone to distortion, increase The value of enhances the ultrasonic amplitude of the ultrasonic component corresponding to the circumferential lateral region.

10. The method for controlling free bending stress based on circumferential ultrasonic excitation as described in claim 8, characterized in that, The ultrasonic frequency of the working ultrasonic actuator is 15kHz to 80kHz, and the basic ultrasonic amplitude is... The value ranges from 1μm to 50μm.

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