Method for adjusting the axial dimension of a u-shaped bellows

Abstract

A kind of U-shaped bellows axial size adjusting method, solve the problem that traditional method is difficult to avoid excessive stretching or compression, easily cause additional material damage inside bellows, affect service life.The U-shaped bellows axial size adjusting method carries out finite element simulation analysis according to material structure size and hydraulic forming process, and establishes the finite element model of stretching or compression deformation carried out by adjusting the axial height of bellows after hydraulic forming using the parameters of revised analysis model;In addition to using the conventional direct stretching or compression method, the deformation area during axial size adjustment is also controlled by applying internal pressure support and external constraint;And according to the finite element simulation result, the axial size adjustment effect is evaluated, and the stretching or compression amount and internal pressure size are revised.The method can obtain optimized bellows axial size adjustment process parameters, can realize accurate control of bellows deformation area, shorten the development cycle, reduce the development cost, and significantly improve the product quality.

Description

Technical Field

[0001] This invention belongs to the field of mechanical engineering technology, specifically relating to a method for adjusting the axial dimensions of a U-shaped bellows that can obtain optimized process parameters for bellows axial dimension adjustment, enabling precise control of the bellows deformation area, shortening the R&D cycle, reducing R&D costs, and significantly improving product quality. Background Technology

[0002] Currently, the manufacturing process of U-shaped metal bellows mainly employs hydroforming. However, after hydraulic unloading, the bellows inevitably spring back, causing changes in its axial dimensions. This results in the straight sections between the corrugations no longer maintaining perpendicularity to the axial direction. When this occurs during forming, reshaping is usually required, which involves stretching or compressing the metal bellows along its length to ensure the axial dimensions meet specifications. However, due to the inherent properties of metal materials, the bellows experience varying degrees of springback after each reshaping process. In actual production, multiple reshaping operations are frequently necessary, inevitably leading to overstretching or overcompression. This results in additional material damage inside the bellows, affecting its service life.

[0003] Furthermore, existing methods for adjusting the axial dimensions of bellows, lacking internal or external support, struggle to control the deformation area during tension or compression. This often results in localized deformation occurring only at the peaks or troughs of a few waves, and neglects the comprehensive performance adjustment achieved by adjusting only the axial dimensions at the peaks or troughs. Therefore, to shorten the development cycle and reduce costs during the R&D phase, and to effectively improve product quality and ensure its stability during mass production, it is necessary to improve existing methods for adjusting the axial dimensions of bellows. Summary of the Invention

[0004] This invention addresses the aforementioned problems by providing a method for adjusting the axial dimensions of a U-shaped bellows. This method allows for optimized process parameters for bellows axial dimension adjustment, enabling precise control of the bellows deformation area, shortening the R&D cycle, reducing R&D costs, and significantly improving product quality.

[0005] The technical solution adopted in this invention is as follows: the axial dimension adjustment method for the U-shaped bellows includes the following steps: Step 1: Based on the material and structural dimensions of the bellows product, as well as the structural dimensions and process parameters of the hydraulic forming mold, establish a finite element simulation analysis model that includes the steps of bellows hydraulic forming and unloading springback analysis, and perform finite element simulation analysis. Then, revise the finite element simulation analysis model based on experimental data. Step 2: Using the modified finite element simulation analysis model, add a bellows axial height adjustment tensile or compressive deformation analysis step between the hydraulic forming and unloading springback analysis steps; Step 3: When adjusting the axial dimensions of the bellows, in addition to using conventional direct stretching or compression operations, the deformation area is also controlled by applying internal pressure support and external constraints. Step 4: Evaluate the effect of axial dimension adjustment based on the finite element simulation results, and correct the amount of tension or compression and the magnitude of internal pressure so that the obtained axial dimensions of the bellows meet the requirements.

[0006] In step two, in the axial height adjustment tensile or compressive deformation analysis step of the simulation analysis model, an initial tensile or compressive amount ΔH0 is set for simulation calculation. ΔH0=α(H 算 -H 设 ) In the formula: H 算 —The axial height dimension of the bellows obtained from the simulation calculation of the corrected finite element model in step one; H 设 —Design value of the axial dimension of the bellows; α—a number greater than 1, used to adjust the iteration speed; generally, the value α = 1 + |ΔH| 设 / (H 算 -H 设 )|,ΔH 设 For design dimension H 设 The difference between the upper and lower limits of the tolerance.

[0007] The above-mentioned method for adjusting the axial dimension of the U-shaped bellows also includes step five: when adjustment is needed, the new axial dimension H of the bellows calculated in step four is extracted. 算新 Value, determine H 算新 Is it within the design dimension H? 设 The axial dimension error of the U-shaped bellows is considered to meet the requirements if it falls between the upper and lower limits; otherwise, the tensile or compressive amount ΔH0 in step four is corrected and the calculation is completed. 修 =α 新 (H) 算新 -H 设 ), where α 新 =1+|ΔH 设 / (H 算新 -H 设 |, that is, the new amount of stretching or compression ΔH 0新 =ΔH0+ΔH 修 .

[0008] The above-mentioned method for adjusting the axial dimension of the U-shaped bellows also includes step six, repeating the steps in step five until the axial dimension error of the U-shaped bellows meets the requirements, i.e., H. 设下限 ≤H 算新 ≤H 设上限 H 设上限 and H 设下限 The design dimensions H are respectively 设 Tolerance upper and lower limits.

[0009] In step three, when the bellows is axially compressed, adjustment plates can be inserted on the outside of the bellows and between two adjacent U-shaped corrugations for support. This will change the axial dimension of each U-shaped corrugation during compression and ensure that the corrugation spacing remains basically unchanged.

[0010] In step three, when the bellows is axially compressed, an adjusting mold can be used to constrain the bellows on the outside and on the outside of each U-shaped bellows. At the same time, internal pressure support is applied to the inside of the bellows by hydraulic pressure. Thus, during compression, the main change is the bellows spacing, while the axial dimension of each U-shaped bellows remains basically unchanged.

[0011] In step three, when the bellows is stretched axially, adjustment plates can be inserted on the outside of the bellows and between two adjacent U-shaped corrugations for support. At the same time, internal pressure support is applied to the inside of the bellows by hydraulic pressure. During stretching, the axial dimension of each U-shaped corrugation is mainly changed, while the corrugation spacing between the corrugations remains basically unchanged.

[0012] In step three, when the bellows is stretched axially, the mold can be adjusted on the outside of the bellows and on the outside of each U-shaped corrugation to constrain it. This will change the corrugation spacing between the corrugations during stretching, ensuring that the axial dimension of each U-shaped corrugation remains basically unchanged.

[0013] The adjusting template includes a template body, with a spacing retaining plug at the front end of the template body. The spacing retaining plug is inserted into the corrugation spacing of the bellows. This ensures that the corrugation spacing remains essentially constant during axial compression or tension of the bellows by adjusting the spacing retaining plug of the template.

[0014] The adjusting mold includes a mold body, and a corrugated retaining groove is provided at the front end of the mold body. The corrugated retaining groove is respectively engaged with the outer side of the U-shaped corrugations of the corrugated pipe. In order to ensure that the axial dimension of each U-shaped corrugation remains basically unchanged by adjusting the corrugated retaining groove of the mold during the axial compression or stretching of the corrugated pipe.

[0015] The beneficial effects of this invention are as follows: The axial dimension adjustment method for U-shaped bellows involves finite element simulation analysis based on the material structure dimensions of the bellows product and the hydroforming process, followed by modification of the finite element simulation analysis model using experimental data. Then, using the main parameters of the modified finite element simulation analysis model, a finite element model of the tensile or compressive deformation during axial height adjustment of the bellows after hydroforming is established. Simultaneously, in addition to conventional direct tension or compression methods, the deformation area during axial dimension adjustment is controlled by applying internal pressure support and external constraints. Finally, the axial dimension adjustment effect is evaluated based on the finite element simulation results, and the tension or compression amount and internal pressure magnitude are adjusted until the obtained bellows axial dimension meets the requirements. This invention allows for the acquisition of optimized bellows axial dimension adjustment process parameters through limited experimentation, and enables precise control of the bellows deformation area, shortening the R&D cycle, reducing R&D costs, and significantly improving product quality. Attached Figure Description

[0016] Figure 1 This is a flowchart of the method of the present invention.

[0017] Figure 2 This is a schematic diagram of a U-shaped corrugated pipe in the method of the present invention.

[0018] Figure 3 This is a schematic diagram of the structure of the adjustment module for the external constraint method in step three of the method of the present invention.

[0019] Figure 4 This is a schematic diagram of a mold for adjusting the external constraint method in step three of the method of the present invention.

[0020] Figure 5 This is a schematic diagram of the external constraint method of the present invention, which uses an adjusting template to limit the change of the corrugation spacing when the corrugated pipe is axially compressed.

[0021] Figure 6 This is a schematic diagram of the external constraint method of the present invention, which uses an adjusting mold and an internal pressure support to limit the deformation of the bellows when the bellows are axially compressed.

[0022] Figure 7 This is a schematic diagram of the external constraint method of the present invention, which uses adjusting plates and internal pressure supports to limit the change of corrugation spacing when the corrugated pipe is subjected to axial tension.

[0023] Figure 8 This is a schematic diagram of the external constraint method for limiting the deformation of the corrugated pipe by adjusting the mold when the corrugated pipe is subjected to axial tension according to the present invention.

[0024] The numbers in the diagram are explained as follows: 1. Corrugated pipe cavity, 2. U-shaped corrugation, 3. Corrugation spacing, 4. Straight section, 5. Mold body, 6. Spacing retaining plug, 7. Mold body, 8. Corrugation retaining slot, 9. Adjusting mold, 10. Adjusting mold. Detailed Implementation

[0025] In recent years, with the development of finite element simulation analysis technology, mold processing technology, and automation control technology, the application of finite element simulation for process optimization has significant practical value. Increasing the complexity of the mold to achieve precise control of the deformation area is an acceptable approach in terms of both production efficiency and economic benefits. The U-shaped bellows axial dimension adjustment method of this invention features a more rational dimension adjustment process, high production efficiency, and precise controllable deformation area. During the R&D phase, it can shorten the R&D cycle and reduce R&D costs. In mass production, it can not only effectively improve product quality but also significantly enhance product quality stability.

[0026] The specific steps of this invention are described in detail. The method for adjusting the axial dimension of the U-shaped bellows includes: Step 1: Based on the material of the corrugated pipe blank, the structural dimensions of the blank, the primary and secondary hydraulic forming pressures, the structural dimensions of the hydraulic forming die, and the process parameters, a finite element simulation analysis model is established, which includes multiple analysis steps such as corrugated pipe hydraulic forming and unloading springback. Finite element simulation analysis is then performed, and the finite element simulation analysis model is corrected based on experimental data.

[0027] The U-shaped bellows has an internal bellows cavity 1, and continuously arranged U-shaped corrugations 2 (crests) on the sidewalls of the bellows cavity 1. A corrugation spacing 3 (trough) is provided between two adjacent U-shaped corrugations 2. Straight sections 4 are also provided at both ends of the U-shaped bellows. The material of the U-shaped bellows can include various structural metal materials or other non-metallic materials that can be prepared using hydroforming processes. The bellows can be a single-layer or multi-layer structure.

[0028] Calculations were performed based on the aforementioned finite element simulation model, and experiments were conducted based on the aforementioned forming process conditions. The simulation calculations and experimental results were compared, for example, the outer diameter D and height H of the U-shaped corrugated pipe. Figure 2 As shown. If the simulation results differ significantly from the experimental results, adjust the material parameters, mesh size, element type, or friction coefficient until the error between the simulation results and the experimental results meets the requirements.

[0029] Step two involves using the modified finite element simulation analysis model's main parameters to add a bellows axial height adjustment tensile or compressive deformation analysis step between the hydraulic forming and unloading springback analysis steps.

[0030] Furthermore, in the axial height adjustment tensile or compressive deformation analysis step of the simulation analysis model, an initial tensile or compressive amount ΔH0 is set for simulation calculation: ΔH0=α(H 算 -H 设 ) In the formula: H 算 —The axial height dimension of the bellows obtained from the simulation calculation of the corrected finite element model in step one; H 设 —Design value of the axial dimension of the bellows; α—a number greater than 1, used to adjust the iteration speed; generally, the value α = 1 + |ΔH| 设 / (H 算 -H 设 )|,ΔH 设 For design dimension H 设 The difference between the upper and lower limits of the tolerance.

[0031] If ΔH0 is greater than 0, compression is required; if ΔH0 is less than 0, stretching is required; if H 算 Within the design dimension H 设 If the value is between the upper and lower limits, the axial dimension of the U-shaped corrugated pipe is considered to meet the requirements, and no adjustment of the axial height dimension is required, thus completing the calculation.

[0032] Step 3: When adjusting the axial dimensions of the bellows, in addition to using conventional direct stretching or compression, the deformation area during axial dimension adjustment is controlled by applying internal pressure support and external constraints.

[0033] For example, when axially compressing the bellows, adjusting plates 9 can be inserted on the outside of the bellows and between two adjacent U-shaped corrugations 2 for support (e.g., Figure 5 As shown in the figure, the axial dimension of each U-shaped corrugation 2 is changed mainly during compression, while ensuring that the corrugation spacing 3 between the corrugations remains basically unchanged.

[0034] When axially compressing the bellows, adjusting molds 10 can be used to constrain the bellows on the outside and on the outside of each U-shaped corrugation 2. Simultaneously, internal pressure support is applied to the inside of the bellows using hydraulic pressure (e.g., Figure 6 As shown in the figure, during compression, the main change is the corrugation spacing 3 between the corrugations, while the axial dimension of each U-shaped corrugation 2 remains basically unchanged.

[0035] When axially stretching the bellows, adjusting plates 9 can be inserted on the outside of the bellows and between two adjacent U-shaped corrugations 2 for support. Simultaneously, internal pressure support is applied to the inside of the bellows using hydraulic pressure (e.g., Figure 7 As shown in the figure, during stretching, the axial dimension of each U-shaped corrugation 2 is mainly changed, while the corrugation spacing 3 between the corrugations remains basically unchanged.

[0036] When axially stretching the bellows, constraints can also be applied to the outside of the bellows and to the outside of each U-shaped corrugation 2 by adjusting the mold 10 (e.g. Figure 8 As shown in the figure, the main change during stretching is the corrugation spacing 3 between the corrugations, which ensures that the axial dimension of each U-shaped corrugation 2 remains basically unchanged.

[0037] Furthermore, the adjusting mold 9 is composed of a mold body 5, with a spacing retaining plug 6 at the front end of the mold body 5. The spacing retaining plug 6 is inserted into the corrugation spacing 3 of the corrugated pipe. Thus, during the axial compression or stretching of the corrugated pipe, the spacing retaining plug 6 of the adjusting mold 9 ensures that the corrugation spacing 3 between the corrugations remains essentially unchanged. Simultaneously, the adjusting mold 10 is composed of a mold body 7, with a corrugation retaining groove 8 at the front end of the mold body 7. The corrugation retaining groove 8 is engaged with the outer side of the U-shaped corrugations 2 of the corrugated pipe. Thus, during the axial compression or stretching of the corrugated pipe, the corrugation retaining groove 8 of the adjusting mold 10 ensures that the axial dimension of each U-shaped corrugation 2 remains essentially unchanged.

[0038] Step four: Evaluate the effect of axial dimension adjustment based on the finite element simulation results, and correct the amount of tension or compression and the magnitude of internal pressure so that the obtained axial dimensions of the bellows meet the requirements.

[0039] Step 5: When adjustments are needed, extract the new axial dimension H of the bellows calculated in Step 4. 算新 Value, determine H 算新 Is it within the design dimension H? 设 The axial dimension error of the U-shaped bellows is considered to meet the requirements if it falls between the upper and lower limits; otherwise, the tensile or compressive amount ΔH0 in step four is corrected and the calculation is completed. 修 =α 新 (H) 算新 -H 设 ), where α 新 =1+|ΔH 设 / (H 算新 -H 设 |, that is, the new amount of stretching or compression ΔH 0新 =ΔH0+ΔH 修 .

[0040] Step six: Repeat step five until the axial dimension error of the U-shaped bellows meets the requirements, i.e., H. 设下限 ≤H 算新 ≤H 设上限 H 设上限 and H 设下限 The design dimensions H are respectively 设 Tolerance upper and lower limits.

Claims

1. A method for adjusting the axial dimension of a U-shaped corrugated pipe, characterized in that, Includes the following steps: Step 1: Based on the material and structural dimensions of the bellows product, as well as the structural dimensions and process parameters of the hydraulic forming mold, establish a finite element simulation analysis model that includes the steps of bellows hydraulic forming and unloading springback analysis, and perform finite element simulation analysis. Then, revise the finite element simulation analysis model based on experimental data. Step 2: Using the modified finite element simulation analysis model, add a bellows axial height adjustment tensile or compressive deformation analysis step between the hydraulic forming and unloading springback analysis steps; Step 3: When adjusting the axial dimensions of the bellows, in addition to using conventional direct stretching or compression operations, the deformation area is also controlled by applying internal pressure support and external constraints. Step 4: Evaluate the effect of axial dimension adjustment based on the finite element simulation results, and correct the amount of tension or compression and the magnitude of internal pressure so that the obtained axial dimensions of the bellows meet the requirements.

2. The method for adjusting the axial dimension of a U-shaped corrugated pipe according to claim 1, characterized in that: In step two, in the axial height adjustment tensile or compressive deformation analysis step of the simulation analysis model, an initial tensile or compressive amount ΔH0 is set for simulation calculation. ΔH0=α(H 算 -H 设 ) Where: H 算 —The axial height dimension of the bellows obtained from the simulation calculation of the corrected finite element model in step one; H 设 —Design value of the axial dimension of the bellows; α — used to adjust the iteration speed, with a value of α = 1 + |ΔH 设 / (H 算 -H 设 )|,ΔH 设 For design dimension H 设 The difference between the upper and lower limits of the tolerance.

3. The method for adjusting the axial dimension of a U-shaped corrugated pipe according to claim 1, characterized in that: This also includes step five, where, when adjustments are needed, the new axial dimension H of the bellows calculated in step four is extracted. 算新 Value, determine H 算新 Is it within the design dimension H? 设 The axial dimension error of the U-shaped bellows is considered to meet the requirements if it falls between the upper and lower limits; otherwise, the tensile or compressive amount ΔH0 in step four is corrected and the calculation is completed. 修 =α 新 (H) 算新 -H 设 ), where α 新 =1+|ΔH 设 / (H 算新 -H 设 |, that is, the new amount of stretching or compression ΔH 0新 =ΔH0+ΔH 修 .

4. The method for adjusting the axial dimension of a U-shaped corrugated pipe according to claim 3, characterized in that: The process also includes step six, which repeats the steps in step five until the axial dimensional error of the U-shaped bellows meets the requirements, i.e., H. 设下限 ≤H 算新 ≤H 设上限 H 设上限 and H 设下限 The design dimensions H are respectively 设 Tolerance upper and lower limits.

5. The method for adjusting the axial dimension of a U-shaped corrugated pipe according to claim 1, characterized in that: In step three, when the bellows is axially compressed, adjustment plates (9) are inserted on the outside of the bellows and between two adjacent U-shaped corrugations (2) for support, thereby changing the axial dimension of each U-shaped corrugation (2) during compression and ensuring that the corrugation spacing (3) between the corrugations remains unchanged.

6. The method for adjusting the axial dimension of a U-shaped corrugated pipe according to claim 1, characterized in that: In step three, when the bellows is axially compressed, an adjusting mold (10) is used to constrain the bellows on the outside and on the outside of each U-shaped corrugation (2). At the same time, internal pressure support is applied to the inside of the bellows by hydraulic pressure, thereby changing the corrugation spacing (3) between the corrugations during compression, while the axial dimension of each U-shaped corrugation (2) remains unchanged.

7. The method for adjusting the axial dimension of a U-shaped corrugated pipe according to claim 1, characterized in that: In step three, when the bellows is stretched axially, adjustment plates (9) are inserted on the outside of the bellows and between two adjacent U-shaped corrugations (2) for support. At the same time, internal pressure support is applied to the inside of the bellows by hydraulic pressure. During stretching, the axial dimension of each U-shaped corrugation (2) is changed, while the corrugation spacing (3) between the corrugations remains unchanged.

8. The method for adjusting the axial dimension of a U-shaped corrugated pipe according to claim 1, characterized in that: In step three, when the bellows is stretched axially, the mold (10) is adjusted to constrain the bellows on the outside of the bellows and on the outside of each U-shaped bellows (2), thereby changing the bellows spacing (3) during stretching to ensure that the axial dimension of each U-shaped bellows (2) remains unchanged.

9. The method for adjusting the axial dimension of a U-shaped corrugated pipe according to claim 5 or 7, characterized in that: The adjustment module (9) includes a module body (5), and a spacing retaining plug (6) is provided at the front end of the module body (5), and the spacing retaining plug (6) is inserted into the corrugated spacing (3) of the corrugated pipe.

10. The method for adjusting the axial dimension of a U-shaped corrugated pipe according to claim 6 or 8, characterized in that: The adjustment mold (10) includes a mold body (7), and the front end of the mold body (7) is provided with a corrugated retaining groove (8), and the corrugated retaining groove (8) is respectively locked on the outside of the U-shaped corrugation (2) of the corrugated pipe.

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