An analytical method for the ring stiffness of pipes

Abstract

This invention provides a method for analyzing the ring stiffness of pipes, belonging to the field of pipe design and analysis technology. It solves the technical problem of high cost in existing pipe ring stiffness testing methods for multi-layer composite pipes or irregularly shaped pipes. This method can perform ring stiffness analysis on irregularly shaped pipes or multi-layer composite pipes, shortening the new product development cycle, providing a basis for product design, and reducing waste caused by frequent mold and material trials.

Description

Technical Field

[0001] This invention belongs to the field of pipe analysis technology and relates to a method for analyzing the ring stiffness of pipes. Background Technology

[0002] The ring stiffness of a pipe is the force (kN) required for vertical deformation per unit length of pipe. It represents the pipe's resistance to ring deformation and is one of the important indicators for buried drainage pipes. The level of ring stiffness determines the burial depth of the pipe. The formula for calculating ring stiffness is: SP=EI / d3, where SP is the ring stiffness of the pipe (kN / ㎡), E is the elastic modulus of the pipe, I is the moment of inertia of the pipe section per unit length, and d is the cross-sectional diameter of the circular pipe. The elastic modulus E is an inherent property of the material.

[0003] Currently, for single materials, the elastic modulus E can be obtained through data lookup. For homogeneous composite materials (mixtures), it can be obtained through testing. The moment of inertia I is data related to the pipe's cross-sectional structure. Generally, during design, for solid-walled pipes, increasing the pipe wall thickness or selecting materials with a higher elastic modulus I is an effective way to improve ring stiffness. However, for structural wall pipes of homogeneous materials (mixtures), we need to use CAD software to analyze the axial cross-sectional moment of inertia I of the pipe. By using a specially designed axial cross-sectional structure to increase the pipe's cross-sectional moment of inertia I, and combining it with an appropriate elastic modulus, the required ring stiffness can be achieved. The above two methods are only effective for circular pipes with a single or homogeneous material composition. However, for irregularly shaped pipes, due to the non-uniformity of the axial cross-section, the cross-sectional moment of inertia I cannot be obtained, making it impossible to calculate the ring stiffness. Furthermore, for multi-layered composite pipes, since the material composition is not uniform, their elastic modulus cannot be obtained through lookup or testing, and the ring stiffness of the pipe cannot be calculated before production, resulting in long product development time and a large amount of waste material during trial production. Summary of the Invention

[0004] To address the aforementioned problems in existing technologies, this invention provides a method for analyzing the ring stiffness of pipes. The technical problem this invention aims to solve is: how to achieve ring stiffness analysis of irregularly shaped wall pipes or multi-layer composite pipes at low cost.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for analyzing the ring stiffness of pipes, characterized by comprising the following steps:

[0007] Step 1: In CAE software, model the pipe fitting according to the design dimensions of the product to be tested, set the material properties of the pipe fitting model, and save the model;

[0008] Step 2: In the CAE software, create two new horizontally positioned upper pressure plate models and lower pressure plate models, arranging them vertically opposite each other. Create two vertically positioned and horizontally spaced connecting rod models, with both connecting rod models fixedly constrained to the lower pressure plate model. The upper ends of the two connecting rod models should extend out of the upper pressure plate model, and the upper pressure plate model should be given a vertical degree of freedom. Set the friction between the upper pressure plate model and the two connecting rod models to 0. Set the material properties of the upper pressure plate model, lower pressure plate model, and connecting rod models to stainless steel, and save the model.

[0009] Step 3: Insert the above-mentioned pipe fitting model between the upper pressure plate model and the lower pressure plate model and center it. For the pipe fitting model with an outer arc surface, set the pipe fitting model to be tangent to the lower surface of the upper pressure plate model and the upper surface of the lower pressure plate model respectively. For the pipe fitting model with a plane on the outer periphery, set the plane on the outer periphery of the pipe fitting model to coincide with the upper surface of the lower pressure plate model, and set the pipe fitting model to coincide with or be tangent to the lower surface of the upper pressure plate model.

[0010] Step 4: Enter the stress analysis module of the CAE software, create a static analysis, and set the upper pressure plate model to be displaced downwards by a distance equal to 3% of the inner diameter of the above-mentioned pipe fitting model;

[0011] Step 5: Initiate stress analysis and view the reaction force data F of the upper pressure plate model. a (KN), according to S a =0.01935F a / L a y a ×10 6 To calculate the ring stiffness S of the pipe fitting model a (KN / m 2 L represents the ring stiffness of the pipe fitting model. a (mm) represents the length dimension of the pipe fitting model, y a (mm) represents the deformation amount when the pipe fitting model undergoes 3% deformation, and is saved as an analysis model.

[0012] This analytical method can simulate multi-layer composite pipes and irregularly shaped pipes in CAE software. By assigning material properties and designing upper pressure plate models, lower pressure plate models, and connecting rod models to interact with the pipe model, the pipe model is positioned between the upper and lower pressure plate models. Fixed constraints are set at the contact points between the pipe model and the upper and lower pressure plate models. This allows for the simulation of the pipe under pressure in CAE software, and the reaction parameters can be directly obtained by analyzing the force feedback of the upper pressure plate model for ring stiffness calculation. It is applicable to the ring stiffness analysis of multi-layer composite pipes and polygonal irregularly shaped pipes, and the calculation results are closer to the actual results. It can be used for product budgeting during new product development, providing guiding parameters, shortening the new product development cycle, reducing trial production waste, and saving development costs.

[0013] In the above method for analyzing the ring stiffness of pipes, in step one, the modeling dimension data of the pipe fitting to be tested is first entered into an Excel spreadsheet and saved. The Excel spreadsheet is then imported into CAE software, which generates the pipe fitting model based on the data in the Excel spreadsheet.

[0014] By making full use of Excel spreadsheets to import the specified data, pipe fitting models can be automatically generated in CAE software, which helps to reduce the modeling cycle and difficulty and improve analysis efficiency.

[0015] The above-mentioned method for analyzing the ring stiffness of pipes also includes:

[0016] Step Six: Compare the ring stiffness results with the expected design ring stiffness value. If it is lower than the design ring stiffness value, modify the composite layer thickness or increase the number of ribs in the Excel spreadsheet and save. Open the analysis model, import the modified Excel spreadsheet to update the analysis model according to the new parameters, enter the stress analysis module to start stress analysis, and view the reaction force data F of the upper pressure plate model. a (KN), according to S a =0.01935F a / L a y a ×10 6 Calculate the ring stiffness of the pipe.

[0017] In this way, when the ring stiffness measurement does not meet the design requirements, the pipe fitting model can be conveniently adjusted and optimized without affecting the pipe diameter. The updated pipe fitting model can be directly analyzed, eliminating the time required to reset constraints and model, thus greatly improving analysis efficiency while ensuring analysis accuracy.

[0018] In the above analysis method for pipe ring stiffness, the CAE software is Inventor, UG, Cero, Autodesk, or Midas.

[0019] This analysis method can be applied to various CAE software and has good versatility.

[0020] In the above analysis method for pipe ring stiffness, the two connecting rod models are respectively arranged at both ends of the pipe model along the axial direction.

[0021] This avoids stress interference between the connecting rod model and the pipe fitting model when they are under pressure, ensuring the accuracy of the analysis data.

[0022] In the above analysis method for pipe ring stiffness, in step four, the reaction force data F can be viewed by right-clicking the upper pressure plate model. a Or export the analysis results file to view the reaction force data F a .

[0023] Clicking directly on the upper pressure plate model to view the reaction force data is faster and more efficient. Viewing the reaction force data through the analysis result file helps to obtain the stress situation of other constraints and facilitates the overall analysis of the test data.

[0024] In the above-mentioned method for analyzing the ring stiffness of pipes, the inner diameter of the pipe fitting model in step four is generated by taking four inner diameter values ​​at 45-degree intervals around the pipe fitting model and calculating the arithmetic mean of the four inner diameter values.

[0025] This allows for a reasonable estimation of the test inner diameter of pipe fittings with irregular inner diameters, ensuring that the analysis results are closer to the actual test results.

[0026] In the above analysis method for pipe ring stiffness, the model is meshed in step three, the average element size of the model is set to 0.1, and the test environment condition is set to 23℃.

[0027] This approach allows for a closer approximation of the experimental environment when performing stress analysis on the entire model, thus ensuring that the analysis results are closer to the actual experimental results.

[0028] Technical effect

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] The method for analyzing the ring stiffness of this pipe can be used to analyze the ring stiffness of pipes with irregular wall structures or multi-layer composite pipes, shortening the development cycle of new products, providing a basis for product design, and helping to reduce the waste caused by frequent mold trials and material trials. Attached Figure Description

[0031] Figure 1 This is a flowchart of the method for analyzing the stiffness of this ring.

[0032] Figure 2 This is a diagram showing the stress analysis results of this embodiment. Detailed Implementation

[0033] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0034] like Figure 1 As shown, the method for analyzing the ring stiffness of this pipe includes the following steps:

[0035] Step 1: First, input the modeling dimensions of the pipe fitting to be tested, including length, outer diameter, inner diameter, wall thickness, and number of wall baffles, into an Excel spreadsheet and save it. Then, import the Excel spreadsheet into Inventor using existing code. Inventor is an existing modeling and analysis software. Inventor will automatically generate the pipe fitting model based on the data in the Excel spreadsheet. Set the material property of the pipe fitting model to HDPE and save the model.

[0036] Step 2: Create two new horizontally positioned upper and lower pressure plate models in Inventor, arranging them vertically opposite each other. Create two vertically positioned, horizontally spaced connecting rod models. The lower pressure plate model forms a fixed constraint 4, and both connecting rod models form fixed constraints 2 and 3 with the lower pressure plate model. The upper ends of the two connecting rod models extend out of the upper pressure plate model, and the upper pressure plate model is given a vertical degree of freedom. The friction between the upper pressure plate model and the two connecting rod models is set to 0. The material properties of the upper pressure plate model, lower pressure plate model, and connecting rod models are set to stainless steel. Save the model.

[0037] Step 3: Insert the above-mentioned pipe fitting model between the upper pressure plate model and the lower pressure plate model and center it. Arrange the two connecting rod models at the two ends of the axial direction of the pipe fitting model. Set the pipe fitting model to be tangent to the lower surface of the upper pressure plate model and the upper surface of the lower pressure plate model. Mesh the entire model. Set the average element size of the model to 0.1 and the test environment condition to 23℃.

[0038] Step 4: Enter the stress analysis module of Inventor, create a static analysis, and set a fixed displacement constraint of 1 for the upper pressure plate model to displace downwards by 3% of the inner diameter of the above-mentioned pipe fitting model.

[0039] Step 5, as shown in the table below. Figure 2 As shown, start the stress analysis, and export the analysis results file to view the reaction force data F of the upper pressure plate model. a (KN), according to S a =0.01935F a / L a y a ×10 6 S aThe ring stiffness (KN / m) of the pipe fitting model 2 ), L a The length dimension (mm) of the pipe fitting model is y. a Calculate the ring stiffness of the pipe when the pipe model is deformed by 3% (mm), and save the analysis model.

[0040]

[0041] Analysis of reaction force results at fixed constraints

[0042] Step Six: Modify the pipe fitting parameters in the Excel spreadsheet based on the ring stiffness results and save it. Open the analysis model to update it according to the parameters in the Excel spreadsheet. Enter the stress analysis module to start stress analysis and view the reaction force data F of the upper pressure plate model. a (KN), according to S a =0.01935F a / L a y a ×10 6 Calculate the ring stiffness of the pipe.

[0043] This analytical method simulates multi-layer composite pipe fittings and material properties in CAE software, and can calculate the ring stiffness of multi-layer composite pipes. The calculation results are close to the actual values ​​and have practical guiding significance. It can be used to budget products during new product development, propose guiding parameters, shorten the new product development cycle, and reduce waste materials in the trial production of new products.

[0044] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for analyzing the ring stiffness of pipes, characterized in that, Includes the following steps: Step 1: In CAE software, model the pipe fitting according to the design dimensions of the product to be tested, set the material properties of the pipe fitting model, and save the model; Step 2: In the CAE software, create two new horizontally positioned upper pressure plate models and lower pressure plate models, arranging them vertically opposite each other. Create two vertically positioned and horizontally spaced connecting rod models, with both connecting rod models fixedly constrained to the lower pressure plate model. The upper ends of the two connecting rod models should extend out of the upper pressure plate model, and the upper pressure plate model should be given a vertical degree of freedom. Set the friction between the upper pressure plate model and the two connecting rod models to 0. Set the material properties of the upper pressure plate model, lower pressure plate model, and connecting rod models to stainless steel, and save the model. Step 3: Insert the above-mentioned pipe fitting model between the upper pressure plate model and the lower pressure plate model and center it. For the pipe fitting model with an outer arc surface, set the pipe fitting model to be tangent to the lower surface of the upper pressure plate model and the upper surface of the lower pressure plate model respectively. For the pipe fitting model with a plane on the outer periphery, set the plane on the outer periphery of the pipe fitting model to coincide with the upper surface of the lower pressure plate model, and set the pipe fitting model to coincide with or be tangent to the lower surface of the upper pressure plate model. Step 4: Enter the stress analysis module of the CAE software, create a static analysis, and set the upper pressure plate model to be displaced downwards by a distance equal to 3% of the inner diameter of the above-mentioned pipe fitting model; Step 5: Initiate stress analysis and view the reaction force data F of the upper pressure plate model. a (KN), according to S a =0.01935F a / L a y a ×10 6 To calculate the ring stiffness of the pipe fitting model, where S a (KN / m 2 L represents the ring stiffness of the pipe fitting model. a (mm) represents the length dimension of the pipe fitting model, y a (mm) represents the deformation amount when the pipe fitting model undergoes 3% deformation, and is saved as an analysis model.

2. The method for analyzing the ring stiffness of pipes according to claim 1, characterized in that, In step one, first input the modeling dimension data of the pipe fitting product to be tested into an Excel spreadsheet and save it. Then import the Excel spreadsheet into the CAE software, so that the CAE software can automatically generate the pipe fitting model based on the data in the Excel spreadsheet.

3. The method for analyzing the ring stiffness of pipes according to claim 2, characterized in that, Also includes: Step Six: Compare the ring stiffness results with the expected design ring stiffness value. If it is lower than the design ring stiffness value, modify the composite layer thickness or increase the number of ribs in the Excel spreadsheet and save. Open the analysis model, import the modified Excel spreadsheet to update the analysis model according to the new parameters, enter the stress analysis module to start stress analysis, and view the reaction force data F of the upper pressure plate model. a (KN), according to S a =0.01935F a / L a y a ×10 6 Calculate the ring stiffness of the pipe.

4. The method for analyzing the ring stiffness of pipes according to claim 1, 2, or 3, characterized in that, CAE software includes Inventor, UG, Cero, Autodesk, or Midas.

5. The method for analyzing the ring stiffness of pipes according to claim 1, 2, or 3, characterized in that, The two connecting rod models are respectively arranged at both ends of the pipe model along the axial direction.

6. The method for analyzing the ring stiffness of pipes according to claim 1, 2, or 3, characterized in that, In step four, you can right-click on the upper pressure plate model to view its reaction force data F. a Or export the analysis results file to view the reaction force data F a .

7. The method for analyzing the ring stiffness of pipes according to claim 1, 2, or 3, characterized in that, In step four, the inner diameter of the pipe fitting model is generated by taking four inner diameter values ​​at 45-degree intervals around the pipe fitting model and calculating the arithmetic mean of the four inner diameter values.

8. The method for analyzing the ring stiffness of pipes according to claim 1, 2, or 3, characterized in that, In step three, the model is meshed, the average element size is set to 0.1, and the experimental environment is set to 23℃.

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