Design method and system for pipe orifice sealing head of bulging forming pipe and pipe orifice sealing head

Abstract

The invention relates to the technical field of bulging forming, in particular to a method and system for designing a pipe orifice sealing head of a bulging forming pipe and the pipe orifice sealing head. The method comprises the following steps that three-dimensional shape data of the end of a pipe orifice after a pipe fitting is subjected to a preorder machining procedure are obtained through computer simulation; on the basis of the three-dimensional shape data, determining an opening taper tolerance zone of the pipe opening; calculating the excess material volume of the pipe orifice relative to the tolerance reference under the offset tolerance zone based on the offset tolerance zone; the shape of a sealing head is designed based on the three-dimensional shape data and the volume of the redundant material, the sealing head comprises a guiding section, a shaping section, a special-shaped sealing section and a pushing section which are sequentially connected, the special-shaped sealing section is provided with a storage tank, and the volume of the storage tank is determined according to the volume of the redundant material; by means of the method, the pipe fitting with the special-shaped pipe opening after the pipe bending and pre-forming procedures can be effectively sealed, and the material supplementing stability and the pipe opening defect repairing capacity in the bulging forming process are improved.

Description

Technical Field

[0001] This invention relates to the field of expansion forming technology, and in particular to a design method, system and sealing head for an expansion forming tube. Background Technology

[0002] Expansion forming processes (such as hydroforming) involve placing the pipe fitting into a mold, applying a clamping force to close the upper and lower molds, and then injecting a liquid or other medium from both ends of the pipe fitting to bring the internal pressure to a set value, thereby achieving high-pressure expansion of the pipe fitting. During this process, it is crucial to ensure a stable increase in internal pressure, and the sealing performance of the sealing heads at the pipe fitting ends is a key factor in ensuring this pressure stability.

[0003] Currently, conventional expansion forming pipe end sealing heads typically consist of four parts: a guide section, a support section, a sealing section, and a pusher section. Each section has a regular planar structure. The sealing principle involves the guide section guiding the material into the pipe end, followed by the support and sealing sections pushing it into the pipe wall to form a stepped embedding shape, thereby achieving a pipe end seal. However, in actual production, pipe fittings need to undergo pre-forming processes such as bending and pre-forming. These processes can easily cause deformation at the pipe end, resulting in irregular bevels or irregular shapes. When faced with such deformed pipe ends, or pipe fittings that require flaring before expansion forming, the regular planar structure of conventional sealing heads cannot fit snugly against the irregular pipe end face, making it difficult to achieve an effective seal. This can lead to pressure leakage during the expansion process, affecting the forming effect and even causing product scrap. Summary of the Invention

[0004] This invention provides a design method, system, and sealing head for a tube end of an expanded tube, so as to effectively seal tubes with irregular shapes at the tube end after bending and preforming processes, and improve the stability of material replenishment and the ability to repair tube end defects during the expansion forming process.

[0005] This invention provides a method for designing a sealing head for the nozzle of an expanded tube, comprising the following steps: Deformation data acquisition steps: Obtain the three-dimensional morphological data of the pipe end after the previous processing steps through computer simulation; Tolerance evaluation steps: Determine the pipe end bevel tolerance zone based on the three-dimensional morphological data; Volume calculation steps: Calculate the excess material volume of the pipe end relative to the tolerance datum under the bevel tolerance zone based on the bevel tolerance zone; Sealing head design steps: Design the shape of the sealing head based on the three-dimensional morphological data and the excess material volume. The sealing head includes a guide section, a shaping section, a shaped sealing section and a pushing section connected in sequence. The shaped sealing section is provided with a storage tank, and the volume of the storage tank is determined based on the excess material volume.

[0006] In one embodiment of the present invention, the deformation data acquisition step includes: The bending and preforming processes of the pipe fittings were simulated using finite element analysis software to obtain three-dimensional morphological data of the pipe end.

[0007] In one embodiment of the present invention, the tolerance evaluation step includes: Extract the highest and lowest points of the three-dimensional topography data, and calculate the range value as the oblique length L; Based on the ideal state where the bevel is 0, and combined with the bevel length L, the bevel tolerance zone is determined to be (0, +L).

[0008] In one embodiment of the present invention, the volume calculation step includes: A reference plane is established based on the lower tolerance of the oblique tolerance zone, and the three-dimensional topography data is segmented to obtain the oblique scrap model; The volume of the oblique scrap model is calculated as the volume of the excess material.

[0009] In one embodiment of the present invention, the sealing head design step includes: The front end profile dimension of the guide section is smaller than the inner profile dimension of the pipe opening, and the design gap between the guide section and the inner wall of the pipe opening is not less than 2.5mm. The shaping section is configured to fit against the inner wall of the pipe opening, with a design gap of no more than 0.2 mm.

[0010] In one embodiment of the present invention, the end face of the guide segment and the connection between the shaping segment and the guide segment are provided with a rounded corner transition structure.

[0011] In one embodiment of the present invention, the shaping section is configured to shape and repair concave defects at the nozzle during the bulging process.

[0012] The present invention also provides a pipe end sealing head design system for an expanded forming tube, used to implement the pipe end sealing head design method for the expanded forming tube, the system comprising: The data acquisition module is used to acquire the three-dimensional morphological data of the pipe end after the pipe fitting has undergone the previous processing steps through computer simulation; The processing module, electrically connected to the data acquisition module, is used to determine the oblique tolerance zone based on the three-dimensional topography data, and to calculate the excess material volume of the pipe mouth relative to the tolerance datum under the oblique tolerance zone based on the oblique tolerance zone. The design module, which is communicatively connected to the processing module, is used to generate a three-dimensional model of the sealing head based on the three-dimensional topographic data and the volume of the excess material. The irregular sealing section of the sealing head is provided with a storage tank whose volume is determined according to the volume of the excess material.

[0013] In one embodiment of the present invention, the data acquisition module is configured to call finite element analysis software to perform simulation calculations.

[0014] In one embodiment of the present invention, the system further includes an output module for outputting the generated three-dimensional model to a CNC machining equipment.

[0015] The present invention also provides a pipe sealing head, comprising a guide section, a shaping section, a shaped sealing section and a pushing section connected sequentially along the axial direction; The shaping section is used to shape the inner wall of the target pipe opening; The sealing end face of the irregularly shaped sealing section is an irregularly shaped curved surface that matches the contour of the end of the target pipe opening; the irregularly shaped sealing section is provided with a storage tank for accommodating excess material; The front end profile dimension of the guide section is smaller than the inner profile dimension of the target nozzle, so as to form an inlet gap between the two.

[0016] In one embodiment of the present invention, the volume of the storage tank is configured to accommodate excess material volume determined by the space between the three-dimensional irregular curved surface at the end of the target nozzle and an ideal reference plane.

[0017] In one embodiment of the present invention, the outer contour size of the shaping segment is adapted to the inner contour size of the target nozzle to form a shaping fit between the two.

[0018] The beneficial effects of this invention are as follows: This invention proposes a method, system, and sealing head design for a pipe end of an expanded forming pipe. By setting a deformation data acquisition step, this application utilizes computer simulation to accurately acquire the three-dimensional morphological data of the pipe end after bending and pre-forming processes, providing a realistic pipe end morphological benchmark for customized sealing head design and avoiding the problem of mismatch between the sealing head and the actual pipe end morphology. Through a tolerance evaluation step, the pipe end bevel tolerance zone is determined based on the three-dimensional morphological data, ensuring that the designed sealing head can cover the possible deformation range of the pipe end and adapt to qualified pipes with different deformation degrees. This eliminates the need to design a separate sealing head for pipe ends with a single deformation degree, improving the versatility of the sealing head. Through a volume calculation step, the excess material volume of the pipe end relative to the tolerance benchmark under the bevel tolerance zone is calculated based on the bevel tolerance zone, providing a basis for the subsequent design of the storage tank in the irregular sealing section of the sealing head. The design provides precise volume data, avoiding issues such as wasted space due to excessively large storage tank volume or material accumulation that damages the sealing surface due to insufficient volume. Finally, in the sealing head design step, based on the aforementioned three-dimensional topographic data and excess material volume, a sealing head is designed comprising a guide section, a shaping section, a shaped sealing section, and a pushing section connected in sequence. The storage tank volume of the shaped sealing section is determined based on the excess material volume, fully accommodating the excess material at the pipe opening and ensuring a tight fit between the sealing head and the pipe end face. Simultaneously, the shaping section fits against the inner wall of the pipe opening, repairing defects such as pipe opening depressions during material replenishment. This ensures a perfect match between the sealing head and the pipe end, guaranteeing uniform stress on the pipe end face and stable material replenishment during the expansion forming process. This effectively improves the pipe opening sealing performance, preventing wrinkling of the formed part's end or product scrap due to pipe opening seal failure, thus supporting the stable and effective implementation of the expansion forming process. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0020] In the attached diagram: Figure 1 This is a schematic diagram of the side structure of the pipe sealing head before the improvement of the present invention; Figure 2 This is a three-dimensional structural diagram of the pipe sealing head prior to an improvement of the present invention; Figure 3 This is a schematic diagram of the structure of the pipe end sealing head and the pipe end of the hydraulically formed pipe before the improvement of the present invention; Figure 4 This is a schematic diagram of the side structure of the pipe sealing head provided in one embodiment of the present invention; Figure 5 This is a three-dimensional structural diagram of a pipe sealing head provided in one embodiment of the present invention; Figure 6 This is a schematic diagram of the nozzle structure of a hydraulically formed tube according to an embodiment of the present invention; Figure 7 This is a schematic diagram showing the position of the storage tank when the pipe sealing head provided in one embodiment of the present invention is engaged with the pipe opening of the hydraulic forming pipe; Figure 8 This is a flowchart of a method for designing a sealing head for an expanded forming tube according to an embodiment of the present invention; The attached diagram is labeled as follows: hydraulic forming tube 10, guide section 1, support section 2, sealing section 3, pushing section 4, shaping section 2X, irregular sealing section 3X, and storage tank F. Detailed Implementation

[0021] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0022] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0023] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0024] This invention relates to a method for designing a sealing head for a hydroformed pipe. The hydroformation process involves placing the pipe fitting into a mold, applying the required clamping force to close the upper and lower molds, and injecting liquid into both ends of the pipe to bring the internal pressure to a set value, thereby achieving a high-pressure internal expansion effect. During the hydroformation process, ensuring a stable pressure rise is crucial, and the water-sealing performance of the sealing head at the pipe end is a key factor.

[0025] Please see Figure 1-2A typical sealing head is basically divided into four parts: guide section 1, support section 2, sealing section 3, and pusher section 4. Each section is a regular plane. The sealing principle is that the material is guided into the pipe opening by the guide section 1, and the support section 2 and sealing section 3 push against the pipe wall to create a stepped embedding shape, thereby achieving a sealing effect. Figure 3 As shown. However, in actual production, pipe fittings undergo pre-processes such as bending, pre-forming, and flaring, resulting in irregular bevels or irregular shapes at the openings. Conventional sealing heads cannot achieve sealing of irregular end faces.

[0026] like Figure 4-8 As shown, the present invention provides a method for designing a sealing head for an expanded tube, comprising the following steps: S1: Deformation data acquisition steps: Obtain the three-dimensional morphological data of the pipe end after the pipe fitting has undergone the previous processing steps through computer simulation; The deformation data acquisition step specifically includes: S11: Simulating the pipe bending process and pre-forming process of the pipe fitting using finite element analysis software to obtain the three-dimensional morphology data of the pipe end; the preceding processing is, for example, the pipe bending process and the pre-forming process. S2: Tolerance evaluation steps: Based on the three-dimensional topography data, determine the orifice bevel tolerance zone; The tolerance evaluation steps specifically include: S21: extracting the highest and lowest points of the three-dimensional topography data and calculating the range value as the bevel length L; S22: taking the ideal state with a bevel of 0 as the benchmark, and combining the bevel length L, determining the bevel tolerance zone as (0, +L). S3: Volume calculation step: Based on the oblique tolerance zone, calculate the volume of excess material at the pipe opening relative to the lower tolerance datum of the oblique tolerance zone; the volume calculation step specifically includes: S31: Establish a reference plane with the lower tolerance of the oblique tolerance zone as the datum, segment the three-dimensional topography data, and obtain the oblique excess material model; S32: Calculate the volume of the oblique scrap model as the volume of the excess material.

[0027] S4: Sealing head design steps: Based on the three-dimensional topography data and the volume of excess material, design the shape of the sealing head. The sealing head includes a guide section 1, a shaping section 2X, a shaped sealing section 3X, and a pushing section 4 connected in sequence. The shaped sealing section 3X is provided with a storage tank F. The volume of the storage tank F is determined according to the volume of excess material. The volume of the storage tank F is equal to the volume of excess material or 5%-10% larger than the volume of excess material (to reserve material deformation redundancy).

[0028] In the sealing head design steps: the front end diameter of the guide section 1 is smaller than the inner diameter of the pipe opening, and the design gap between it and the inner wall of the pipe opening is not less than 2.5mm; the shaping section 2X is configured to fit against the inner wall of the pipe opening, and the design gap is not greater than 0.2mm.

[0029] Furthermore, the end face of the guide segment 1 and the connection between the shaping segment 2X and the guide segment 1 are provided with rounded corner transition structures.

[0030] Furthermore, the shaping segment 2X is configured to reshape and repair concave defects at the nozzle during the bulging process.

[0031] As an optional embodiment of the present invention, the method for designing the sealing head of the tube end of the bulging forming tube described in this case includes: ① Deformation data acquisition: During the part process design stage, the blanking length a and the coordinates (X, Y, Z) of the bend inflection point are input through CAE simulation software (specifically finite element analysis software) to generate the bend centerline and determine the bending angle θ; then the pipe bending process is simulated to obtain simulated bend data A; data A is imported into the preforming process mold surface, and the mold closing pressure T is input at the same time to continue simulating the preforming process to obtain preforming simulation data B; the three-dimensional morphology data of the pipe end of the part is extracted from data B.

[0032] ② Orifice skewness tolerance assessment: Based on the extracted three-dimensional morphology data of the pipe end, select the lowest and highest points of the pipe end and calculate the range between them. This range is determined as the orifice skewness length L. Based on the lower limit value of the orifice skewness length L, the orifice skewness tolerance zone of the pipe end is determined to be (0, +L).

[0033] ③ Calculation of excess material volume: Based on the determined oblique tolerance zone (0, +L), establish a reference plane with the lower tolerance of the tolerance zone as the benchmark; divide the pipe opening through the reference plane to obtain the oblique excess material; calculate the volume of the oblique excess material and determine it as the excess material volume E.

[0034] ④ Sealing head design: Based on the three-dimensional topographic data of the pipe end, generate the irregular cross section of the pipe end before the sealing head enters the pipe, and then design the shape of the sealing head (the sealing head includes the guide section 1, shaping section 2X, irregular sealing section 3X and push section 4 connected in sequence): the front end dimension of the guide section 1 is smaller than the inner diameter of the pipe, the design gap between it and the inner wall of the pipe is ≥2.5mm, and the end face of the guide section 1 adopts R5 rounded corner transition; the shaping section 2X fits against the inner wall of the pipe, the design gap between it and the inner wall of the pipe is ≤0.2mm, and the connection between the shaping section 2X and the guide section 1 adopts R5 rounded corner transition; at the same time, design the irregular sealing section 3X based on the irregular cross section of the pipe end after the sealing head enters the pipe, and design the storage tank F of the irregular sealing section 3X according to the excess material volume E calculated in step ③ (the volume of the storage tank F is equal to the excess material volume E).

[0035] Please see Figure 4-8 This embodiment takes the design of the pipe end sealing head of 10 aluminum alloy expanded forming tubes for a certain automobile chassis (using a hydroforming process) as an example to explain in detail the specific implementation process of the pipe end sealing head design method of the expanded forming tube described in this invention. At the same time, it also explains the design system for implementing the method and the pipe end sealing head structure obtained therefrom.

[0036] In this embodiment, the aluminum alloy tube to be processed needs to undergo a bending process and a pre-forming process before entering the hydraulic expansion forming process. To ensure stable pressure inside the tube during expansion forming, a sealing head adapted to the tube opening needs to be designed. The specific design steps are as follows: The first step is to acquire deformation data: obtain the three-dimensional morphological data of the pipe end after the pipe has undergone bending and pre-forming processes through computer simulation. In this embodiment, conventional finite element analysis software (such as ABAQUS and ANSYS) is used as the simulation tool. First, the basic process parameters of the aluminum alloy tube are input into the software: blanking length a, bending inflection point coordinates (X,Y,Z), and bending angle θ. The software automatically generates the bending centerline model of the tube based on the above parameters. Then, the bending process simulation is started to simulate the bending process of the tube on the bending equipment, and the tube shape data A after bending is obtained. Next, data A is imported into the mold surface model of the preforming process, and the mold closing pressure T required for preforming is input. The preforming process simulation is started again to simulate the pre-compression shaping process of the tube after bending by the mold closing, and the tube shape data B after preforming is obtained. Finally, the feature extraction function of the finite element analysis software is used to filter out the three-dimensional point cloud data of the tube end area from data B. After noise reduction and fitting processing, the three-dimensional morphology data of the tube end is obtained. This data can clearly reflect the irregular shape of the tube end after preforming (such as local slopes and slight depressions).

[0037] After acquiring the deformation data, the tolerance evaluation step is performed: based on the three-dimensional topography data, the bevel tolerance zone of the pipe opening is determined. Specifically, the axial section view of the three-dimensional topography data at the pipe opening end is first called in the finite element analysis software. Multiple feature points distributed along the circumference of the pipe opening edge are selected (ensuring full coverage of the pipe opening). Using the software's dimensional measurement function, the vertical distance from each feature point to the pipe fitting's reference axis (determined by the axis of the pipe fitting's central hole) is calculated. From the measured distance values, the maximum value (i.e., the distance corresponding to the highest point) and the minimum value (i.e., the distance corresponding to the lowest point) are selected, and the range between them is calculated. This range is determined as the bevel length L. Then, referring to the machining accuracy requirements of this type of aluminum alloy pipe fitting, the lower limit value of the bevel length L is determined. Using this lower limit value as a benchmark, the bevel tolerance zone of the pipe opening is finally determined to be (0, +L), meaning the actual bevel amount of the pipe opening will not exceed the range of 0 to L. Subsequent sealing head design must cover this tolerance range.

[0038] Next, the volume calculation step is performed: based on the aforementioned oblique tolerance zone, the excess material volume of the pipe opening relative to the lower tolerance datum of the oblique tolerance zone is calculated. In this embodiment, firstly, using the lower tolerance of the oblique tolerance zone (i.e., the state when the oblique amount is 0) as the datum, a reference plane is established in 3D modeling software (such as SolidWorks). This reference plane is perpendicular to the datum axis of the pipe fitting and coincides with the end face of the pipe opening when the oblique amount is 0. Then, the previously acquired 3D topographic data of the pipe opening end is imported into the 3D modeling software. Using the software's "section segmentation" function, the 3D topographic model of the pipe opening is segmented using the established reference plane as the segmentation surface. The material model outside the reference plane (i.e., the part exceeding the end face when the oblique amount is 0) is retained, and this model is the oblique excess material model. Finally, the software's "volume calculation" function is called to calculate the volume of the oblique excess material model to obtain the excess material volume of the pipe opening. This volume value will serve as the core basis for the subsequent design of the sealing head storage tank F.

[0039] Finally, the sealing head design step is carried out: Based on the three-dimensional topographic data and the volume of excess material, the shape of the sealing head is designed. The sealing head includes a guide section 1, a shaping section 2X, a shaped sealing section 3X, and a pusher section 4 connected in sequence. The specific design process is as follows: For the guide section 1, the outer diameter of the front end of the guide section 1 is determined according to the actual inner diameter of the pipe opening, so that the design gap between the guide section 1 and the inner wall of the pipe opening is not less than 2.5mm; at the same time, a rounded corner structure is processed on the front end face of the guide section 1 to avoid scratching the inner wall of the pipe opening when the sealing head is introduced into the pipe opening. For the shaping section 2X, the outer diameter of the shaping section 2X is designed based on the contour dimensions of the inner wall of the pipe opening in the three-dimensional topography data of the pipe opening end, so that the design gap between the shaping section 2X and the inner wall of the pipe opening is no more than 0.2mm, and the rounded corner structure is also processed at the connection between the shaping section 2X and the guide section 1; during the subsequent expansion forming process, when the sealing head enters the pipe opening, the outer wall of the shaping section 2X can fit tightly with the inner wall of the pipe opening (including the local depressions), and the depression defects are squeezed and shaped under the action of the pushing force, so as to realize the shaping and repair of the pipe opening depressions. For the irregular sealing section 3X, the contour of its sealing end face is designed entirely based on the three-dimensional topographic data of the pipe end. That is, the sealing end face is an irregular curved surface that perfectly matches the irregular contour (such as a local slope) of the pipe end. At the same time, a material storage groove F is opened on the end face of the irregular sealing section 3X. The volume of the material storage groove F is equal to the previously calculated volume of excess material, ensuring that the excess material of the pipe end can be completely contained in the material storage groove F during expansion forming, avoiding material accumulation that affects the sealing effect. For the pushing section 4, a conventional cylindrical structure design is adopted, and its dimensions are determined according to the installation and force transmission requirements of the hydraulic forming equipment for the pushing action of the sealing head.

[0040] The present invention also provides a pipe end sealing head design system for an expanded forming tube, used to implement the pipe end sealing head design method for the expanded forming tube, the system comprising: The data acquisition module is used to acquire the three-dimensional morphological data of the pipe end after the pipe fitting has undergone the previous processing steps through computer simulation; The processing module, electrically connected to the data acquisition module, is used to determine the oblique tolerance zone based on the three-dimensional topography data, and to calculate the excess material volume of the pipe mouth relative to the tolerance datum under the oblique tolerance zone based on the oblique tolerance zone. The design module, which is communicatively connected to the processing module, is used to generate a three-dimensional model of the sealing head based on the three-dimensional topographic data and the volume of the excess material. The irregular sealing section 3X of the sealing head is provided with a storage tank F whose volume is determined according to the volume of the excess material.

[0041] The system includes a data acquisition module, a processing module, a design module, and an output module. The data acquisition module is configured to call the aforementioned conventional finite element analysis software to acquire 3D topographic data of the pipe end through simulation calculations. The processing module is electrically connected to the data acquisition module. It first receives the 3D topographic data transmitted by the data acquisition module, determines the oblique tolerance zone through a built-in tolerance calculation algorithm, and then calculates the volume of excess material in the pipe end model using a volume calculation algorithm. The design module is communicatively connected to the processing module. Based on the 3D topographic data and excess material volume output by the processing module, it automatically generates a 3D model of the sealing head using a 3D modeling algorithm. The volume of the storage tank F of the irregular sealing section 3X in the model is consistent with the volume of excess material. The output module is connected to the design module. It converts the generated 3D model of the sealing head into code (such as G-code) recognizable by CNC machining equipment and transmits it to CNC lathes, milling machines, and other machining equipment for direct machining to obtain the actual pipe end sealing head.

[0042] The present invention also provides a pipe sealing head, comprising a guide section 1, a shaping section 2X, a non-shaped sealing section 3X, and a pusher section 4 connected sequentially along the axial direction; The shaping section 2X is used to shape the inner wall of the target pipe opening; The sealing end face of the irregular sealing section 3X is an irregular curved surface that matches the contour of the end of the target pipe opening; the irregular sealing section 3X is provided with a storage tank F for accommodating excess material; The front end contour dimension of the guide section 1 is smaller than the inner contour dimension of the target nozzle, so as to form an inlet gap between the two.

[0043] Furthermore, the volume of the storage tank F is configured to accommodate the excess material volume determined by the space between the three-dimensional irregular curved surface at the end of the target nozzle and an ideal reference plane.

[0044] Furthermore, at least the irregular sealing section 3X of the shaping section 2X and the irregular sealing section 3X is inclined to adapt to the oblique opening of the pipe mouth of the hydraulically formed pipe 10.

[0045] The pipe sealing head obtained by the above design method is connected axially in sequence with guide section 1, shaping section 2X, irregular sealing section 3X and push section 4: the outer contour dimension of shaping section 2X is adapted to the inner contour dimension of the target pipe opening to form a shaping fit between the two, which can shape the inner wall of the pipe opening during expansion forming; the sealing end face of irregular sealing section 3X is an irregular curved surface that perfectly matches the end contour of the target pipe opening, and the volume of the storage groove F opened on it is configured to accommodate the excess material volume determined by the space between the three-dimensional irregular curved surface of the end of the target pipe opening and the tolerance reference plane under the oblique tolerance zone (i.e., the above reference plane); the front end contour dimension of guide section 1 is smaller than the inner contour dimension of the target pipe opening to form an inlet gap between the two, ensuring that the sealing head can be smoothly pushed into the pipe opening.

[0046] In practical hydraulic bulging forming applications, the sealing head designed and processed above is installed on the end cap of the hydraulic forming equipment. After the equipment closes the mold, the sealing head is pushed into the pipe opening by the pushing mechanism: the guide section 1 smoothly enters the pipe opening through the guide gap, avoiding collision with the inner wall of the pipe opening; the shaping section 2X fits tightly against the inner wall of the pipe opening, and under the action of the pushing force, it squeezes and flattens the local depressions of the pipe opening, completing the defect repair; the sealing end face of the irregular sealing section 3X fits completely with the irregular contour of the pipe opening end, while the excess material of the pipe opening flows into the storage tank F, avoiding material accumulation that could cause misalignment of the sealing surface; finally, the pushing section 4 continues to apply the pushing force, which, together with the liquid pressure injected into the pipe, achieves stable bulging of the pipe fitting. Throughout the process, the pipe opening has good sealing performance, with no pressure leakage, and the formed pipe end has no defects such as wrinkles or depressions.

[0047] Compared to conventional hydraulic forming sealing heads, the pipe end sealing head of the expanded forming tube obtained by the design method of this invention can perfectly match the pipe end; during the expansion forming and feeding process, the pipe end face is subjected to more uniform force, the feeding is more stable, and the feeding effect and sealing performance are greatly improved. In addition, the shaping section 2X of the pipe end sealing head can also repair the pipe end concave defects during the feeding process.

[0048] During the hydraulic forming process, this pipe end sealing head can prevent wrinkling or product scrapping caused by the pipe inlet being skewed or recessed, thereby achieving the effect of cost reduction and efficiency improvement.

[0049] The pipe end sealing head obtained by the design method of this invention can be applied to pipe ends of any shape; the pipe end sealing head design scheme of the expansion forming pipe provided by this invention can be developed in both forward and reverse directions; at the same time, the pipe end sealing head obtained by the design method of this invention is not only applicable to the pipe end sealing of hydroformed pipes, but also applicable to other expansion forming processes that require mouth sealing, such as hot gas expansion.

[0050] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for designing a sealing head for the nozzle of an expanded forming tube, characterized in that, Includes the following steps: Three-dimensional morphological data of the pipe end after the pipe fitting has undergone the previous processing steps are obtained through computer simulation. Based on the three-dimensional topography data, the nozzle bevel tolerance zone is determined; Based on the aforementioned oblique tolerance zone, the excess material volume of the pipe opening relative to the tolerance datum under the oblique tolerance zone is calculated; based on the three-dimensional topography data and the excess material volume, the shape of the sealing head is designed, the sealing head including a guide section, a shaping section, a shaped sealing section and a pushing section connected in sequence, wherein the shaped sealing section is provided with a storage tank, the volume of which is determined according to the excess material volume.

2. The method for designing a sealing head for the nozzle of an expanded forming tube according to claim 1, characterized in that, The step of obtaining the three-dimensional morphological data of the pipe end after the previous processing steps through computer simulation includes: The bending and preforming processes of the pipe fittings were simulated using finite element analysis software to obtain three-dimensional morphological data of the pipe end.

3. The method for designing a sealing head for the nozzle of an expanded forming tube according to claim 1, characterized in that, The step of determining the nozzle bevel tolerance zone based on the three-dimensional topography data includes: Extract the highest and lowest points of the three-dimensional topography data, and calculate the range value as the oblique length L; Based on the ideal state where the slant is 0, the slant tolerance zone is determined to be (0, +L).

4. The method for designing a sealing head for the tube end of an expanded forming tube according to claim 3, characterized in that, The step of calculating the excess material volume of the nozzle relative to the tolerance datum under the nozzle deviation tolerance zone, based on the nozzle deviation tolerance zone, includes: A reference plane is established based on the lower tolerance of the oblique tolerance zone, and the three-dimensional topography data is segmented to obtain the oblique scrap model; The volume of the oblique scrap model is calculated as the volume of the excess material.

5. The method for designing a sealing head for the nozzle of an expanded forming tube according to claim 1, characterized in that, In the step of designing the shape of the sealing head based on the three-dimensional topography data and the excess material volume: The front end profile dimension of the guide section is smaller than the inner profile dimension of the pipe opening, and the design gap between the guide section and the inner wall of the pipe opening is not less than 2.5mm. The shaping section is configured to fit against the inner wall of the pipe opening, with a design gap of no more than 0.2 mm.

6. The method for designing a sealing head for the nozzle of an expanded forming tube according to claim 5, characterized in that, The shaping section is configured to reshape and repair concave defects at the nozzle during the bulging process.

7. A pipe end sealing head design system for an expanded forming tube, characterized in that, The system is used to implement the nozzle sealing head design method for the expanded forming tube as described in any one of claims 1 to 6, the system comprising: The data acquisition module is used to acquire the three-dimensional morphological data of the pipe end after the pipe fitting has undergone the previous processing steps through computer simulation; The processing module, electrically connected to the data acquisition module, is used to determine the oblique tolerance zone based on the three-dimensional topography data, and to calculate the excess material volume of the pipe mouth relative to the tolerance datum under the oblique tolerance zone based on the oblique tolerance zone. The design module, which is communicatively connected to the processing module, is used to generate a three-dimensional model of the sealing head based on the three-dimensional topographic data and the volume of the excess material. The irregular sealing section of the sealing head is provided with a storage tank whose volume is determined according to the volume of the excess material.

8. The tube end sealing head design system for the expanded forming tube according to claim 7, characterized in that, The data acquisition module is configured to call finite element analysis software for simulation calculation, and / or the system also includes an output module for outputting the generated three-dimensional model to CNC machining equipment.

9. A pipe end sealing head, characterized in that, It includes a guide section, a shaping section, a shaped sealing section and a pushing section connected sequentially along the axial direction; The shaping section is used to shape the inner wall of the target pipe opening; The sealing end face of the irregularly shaped sealing section is an irregularly shaped curved surface that matches the contour of the end of the target pipe opening; the irregularly shaped sealing section is provided with a storage tank for accommodating excess material; The front end profile dimension of the guide section is smaller than the inner profile dimension of the target nozzle, so as to form an inlet gap between the two.

10. The pipe sealing head according to claim 9, characterized in that, The volume of the storage tank is configured to accommodate excess material volume determined by the space between the three-dimensional irregular curved surface at the end of the target nozzle and an ideal reference plane.

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