Finite element analysis-based vibration stress state analysis method of support hanger

Abstract

The invention relates to the technical field of finite element simulation testing, in particular to a support hanger vibration stress state analysis method based on finite element analysis, which comprises the following steps: step 1, creating a three-dimensional model of a steam-water pipeline system comprising a support hanger; 2, finite element software is imported, a spring unit, thermal displacement boundary conditions and connection rigidity are finely defined, and a high-fidelity finite element model is established; 3, statics analysis and modal analysis are carried out, and stress, strain, inherent frequency and vibration mode under the action of gravitational acceleration, pipeline internal pressure, pipeline operation temperature and pipeline displacement load are obtained; and 4, based on the material strength and the vibration test frequency, judging the model precision and reliability, and if not, optimizing the model parameters. According to the method, boundary conditions and model parameters are finely defined, and verification and correction are performed by using experimental data, so that the simulation precision of the model is remarkably improved, and the model can be reliably used for identifying and analyzing the load of the support hanger.

Description

Technical Field

[0001] This invention relates to the field of finite element simulation and testing technology, and specifically to a method for analyzing the vibration stress state of supports and hangers based on finite element analysis. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Pipeline supports and hangers are critical supporting components in the piping systems of thermal power plants, and the accuracy of their load status directly affects the operational safety of the piping system. Currently, the main methods for analyzing support and hanger loads include empirical formulas, in-situ strain gauge testing, and general finite element analysis. Among these, empirical formulas have low calculation accuracy and cannot reflect the interactions within complex piping systems. In-situ strain gauge testing is difficult to implement, highly susceptible to environmental influences, and, being a point measurement, cannot comprehensively reflect the load distribution. Existing general finite element analysis methods are often overly idealistic in model construction, failing to consider the nonlinear stiffness characteristics of variable / constant force spring elements in the supports and hangers, neglecting the dynamic changes in the boundary conditions of the supports and hangers during thermal displacement of the pipeline, and improperly simplifying the connection stiffness between connecting members. These problems lead to significant deviations between the calculated structural dynamic characteristics and actual values, failing to provide a reliable calculation benchmark for accurate load inversion based on vibration testing. Summary of the Invention

[0004] This invention provides a method for analyzing the vibration stress state of supports and hangers based on finite element analysis. By refining the definition of boundary conditions and model parameters and using experimental data for verification and correction, the simulation accuracy of the model is significantly improved, enabling it to be reliably used for the identification and analysis of support and hanger loads. Specifically, the technical solution of this invention is as follows.

[0005] A method for analyzing the vibration stress state of supports and hangers based on finite element analysis includes the following steps: Step 1: Based on the structural parameter information of the steam and water pipe support system, create a 3D model of the steam and water pipe support system using 3D software, and save it to the specified working directory in a format that the finite element software can recognize.

[0006] Step 2: Import the three-dimensional model from Step 1 into the finite element software, set the finite element model according to the material performance parameters of the pipeline, and then apply refined boundary conditions and loads to the finite element model to perform static and modal analysis.

[0007] Step 3: Based on the static analysis described in Step 2, obtain the stress and strain distribution under the combined action of gravitational acceleration, pipeline internal pressure, pipeline operating temperature, and pipeline thermal displacement load.

[0008] Step 4: Based on the modal analysis described in Step 2, obtain the natural frequencies and corresponding mode shapes of the support system.

[0009] Step 5: Based on the strength limit of the spring in the support and the frequency data obtained from the vibration test of the support on site, determine whether the natural frequency and mode shape calculated in Step 4 meet the accuracy and design requirements.

[0010] Furthermore, in step 1, the structural parameters include: the outer diameter, wall thickness, length, and material grade of the pipe; and the installation position, type, and spring stiffness curve of the support.

[0011] Furthermore, in step 2, the material performance parameters include: elastic modulus, Poisson's ratio, density, and coefficient of thermal expansion.

[0012] Furthermore, in step 2, the refined boundary conditions include: (1) Use the spring element in the finite element software to simulate the elastic support of the support and input its stiffness-displacement curve.

[0013] (2) At the connection point between the support and the pipeline, the displacement of each support under different working conditions is obtained based on the pipeline thermal expansion analysis results, and the thermal displacement boundary conditions are defined as: axial displacement UX and radial displacement UY.

[0014] (3) Set up node coupling at the connection between the connecting pipe and the support to simulate the actual connection stiffness.

[0015] Furthermore, in step 3, the process of obtaining the stress and strain distribution through the static analysis includes: (i) Set the element type and material properties of the support in the finite element software.

[0016] (ii) Mesh the three-dimensional model and refine the mesh in the stress concentration region.

[0017] (iii) Apply gravitational acceleration, pipe internal pressure, operating temperature field and the thermal displacement boundary conditions described in step (2).

[0018] (iV) Select the static analysis type to solve the problem and obtain stress and strain contour maps.

[0019] Furthermore, in step 4, the process of obtaining the natural frequencies and mode shapes through the modal analysis includes: (a) Maintain the prestressed state after the static analysis is completed.

[0020] (b) Switch the analysis type to modal analysis and use the block-based Lanzos method for modal extraction.

[0021] (c) Solve the characteristic equations of the system to obtain the natural frequencies of each order and their corresponding mode shapes.

[0022] Furthermore, in step 5, if the on-site measurement results and the finite element model calculation results meet the aforementioned accuracy and design requirements, then the model construction is completed and can be used for theoretical analysis of the vibration stress state of the support and hanger.

[0023] Furthermore, in step 5, if the on-site measurement results and the finite element model calculation results do not meet the accuracy and design requirements, the model parameters are adjusted, and then steps 1 to 5 are repeated until the requirements are met.

[0024] Furthermore, if the error rate between the on-site measured results and the finite element model calculation results does not exceed 3%, it is determined that the accuracy and design requirements are met; otherwise, they are not met.

[0025] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: The method of this invention, by utilizing the stiffness-displacement curves and thermal displacement boundary conditions of spring elements, enables the obtained finite element model to accurately reflect the mechanical behavior of supports and hangers under actual working conditions. This establishes a standardized modeling and verification process, and addresses the pain point of insufficient accuracy in general models through "experiment-simulation" comparison and parameter inversion. The theoretical model constructed by the method of this invention can serve as a reliable basis for inverting the actual load of supports and hangers based on the vibration frequency method, effectively improving the accuracy and efficiency of safety monitoring of power plant pipeline systems, and providing key technical support for the safety assessment and optimized maintenance of pipeline systems. Attached Figure Description

[0026] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention and do not constitute an undue limitation of the invention.

[0027] Figure 1 The following is a flowchart of the vibration stress state analysis method for supports and hangers based on finite element analysis in the embodiments below.

[0028] Figure 2 The following is a schematic diagram of a three-dimensional model of the steam and water pipe support system in the embodiments below.

[0029] Figure 3 The following are the stiffness-displacement curves of the variable force spring hanger in the embodiments.

[0030] Figure 4The following examples show stress and strain contour plots obtained from static analysis.

[0031] Figure 5 The following are the first and sixth modal diagrams obtained from the modal analysis of the connecting rods in the embodiments. Detailed Implementation

[0032] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as those skilled in the art. The technical solutions of the present invention will now be further described with reference to specific embodiments.

[0033] like Figure 1 As shown, taking a single-rod variable-force spring support system for the main steam pipeline of a power plant as an example, this paper illustrates a method for analyzing the vibration stress state of supports based on finite element analysis, specifically including the following steps: Step 1: Based on the structural parameters of the steam and water pipe support system provided by the manufacturer, create a 3D model of the system (mainly including pipes, supports, etc., with the lower end of the connecting rods of the supports connected to the pipes) using the 3D software SolidWorks. Figure 2 As shown in the image, export the file as a .x_t file and save it to the specified working directory. The structural parameters include: pipe specifications Φ457×85mm (i.e., outer diameter 457mm, wall thickness 85mm), material P92 steel, length 5m; the supports are variable spring hangers, and their stiffness-displacement curves are provided by the manufacturer, such as... Figure 3 As shown.

[0034] Step 2: Open the finite element software ANSYS, import the 3D model from Step 1 into ANSYS, and set the finite element model according to the material properties of the pipe (including: material is P92 steel, elastic modulus, Poisson's ratio, density, and coefficient of thermal expansion at room temperature and 540℃, as shown in Table 1 below). Then, apply refined boundary conditions and loads to the finite element model and perform static and modal analyses. The refined boundary conditions include: (1) Use the spring element COMBIN39 in the finite element software to simulate the elastic support (variable force spring hanger) of the support and input its stiffness-displacement curve.

[0035] (2) At the connection point between the support and the pipeline (i.e., at the lifting point of the variable spring hanger), apply thermal displacement boundary conditions based on the pipeline thermal expansion analysis results: UX=8mm, UY=-3mm. UX and UY refer to the axial displacement and radial displacement of the pipeline caused by temperature changes, respectively.

[0036] (3) Using the CERIG command in the finite element software, node coupling is set at the connection between the support and the pipe to simulate the rigid connection area between the hanger and the connecting plate in the steam pipe support system.

[0037] Table 1

[0038] Step 3: Based on the static analysis described in Step 2, obtain the stress and strain distribution under the combined effects of gravitational acceleration, pipe internal pressure, pipe operating temperature, and pipe thermal displacement load. This specifically includes the following steps: (i) In the Preprocessor module of the finite element software ANSYS, set the element type and material properties of the support: the spring uses COMBIN39 element, the material is P92 steel, and the performance parameters are as follows: Figure 3 As shown.

[0039] (ii) The three-dimensional model is meshed, and the stress concentration areas such as the connection between the support and the pipe and the structural abrupt change area are refined.

[0040] (iii) Apply gravitational acceleration (9.80 m / s²), pipeline internal pressure (18 MPa), pipeline operating temperature (540 °C) and the thermal displacement boundary conditions described in step (2): UX = 15 mm, UY = -3 mm.

[0041] (iV) Select the static analysis type to solve the problem and obtain the stress and strain contour diagrams at the locations of the connecting members of the support and hanger, as shown below. Figure 4 As shown.

[0042] Step 4: Based on the modal analysis described in Step 2, obtain the natural frequencies and corresponding mode shapes of the support system. This specifically includes the following steps: (a) After the static analysis is completed, the prestressed state is maintained by using the PSTRES,ON command.

[0043] (b) Switch the analysis type to modal analysis and use the block-based Lanzos method for modal extraction.

[0044] (c) Solve the characteristic equations of the system to obtain the first 10 natural frequencies and their corresponding mode shapes. The first and sixth modes are as follows: Figure 5 As shown.

[0045] Step 5: Based on the strength limit of the variable-force spring in the support and the frequency data (34.1Hz) obtained from the field vibration test, compare this frequency data with the first-order frequency obtained from the modal analysis above. Figure 5As shown in the figure. The results show that the error rate between the two is less than 10%. This indicates that the finite element model constructed in this embodiment has high accuracy and can be used for theoretical analysis of the vibration stress state of subsequent supports and hangers. For example, after the vibration frequency of the support and hanger is measured on site, the load size can be adjusted on this model for iterative calculation. When the calculated frequency of the model is consistent with the measured frequency on site, the load applied by the model is the actual load of the support and hanger. This embodiment uses the stiffness-displacement curve and thermal displacement boundary conditions of the spring element to enable the obtained finite element model to accurately reflect the mechanical behavior of the support and hanger under the actual working state, thus forming a standardized modeling and verification process. The pain point of insufficient accuracy of general models is solved by "experiment-simulation" comparison and parameter inversion. The theoretical model constructed by the method of this invention can serve as a reliable basis for inverting the actual load of the support and hanger based on the vibration frequency method, providing a solid analytical foundation for vibration-based load identification, and effectively improving the accuracy and efficiency of power plant pipeline system safety monitoring.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., should be included within the protection scope of the present invention.

Claims

1. A method for analyzing the vibration stress state of supports and hangers based on finite element analysis, characterized in that, Includes the following steps: Step 1: Based on the structural parameter information of the steam and water pipe support system, create a 3D model of the steam and water pipe support system using 3D software, and save it to the specified working directory in a format that the finite element software can recognize. Step 2: Import the three-dimensional model from Step 1 into the finite element software, set the finite element model according to the material performance parameters of the pipeline, and then apply refined boundary conditions and loads to the finite element model to perform static analysis and modal analysis. Step 3: Based on the static analysis described in Step 2, obtain the stress and strain distribution under the combined action of gravitational acceleration, pipeline internal pressure, pipeline operating temperature, and pipeline thermal displacement load. Step 4: Based on the modal analysis described in Step 2, obtain the natural frequencies and corresponding mode shapes of the support system; Step 5: Based on the strength limit of the spring in the support and the frequency data obtained from the vibration test of the support on site, determine whether the natural frequency and mode shape calculated in Step 4 meet the accuracy and design requirements.

2. The method for analyzing the vibration stress state of supports and hangers based on finite element analysis according to claim 1, characterized in that, In step 1, the structural parameters include: the outer diameter, wall thickness, length, and material grade of the pipe; and the installation position, type, and spring stiffness curve of the support.

3. The method for analyzing the vibration stress state of supports and hangers based on finite element analysis according to claim 1, characterized in that, In step 2, the material performance parameters include: elastic modulus, Poisson's ratio, density, and coefficient of thermal expansion.

4. The method for analyzing the vibration stress state of supports and hangers based on finite element analysis according to claim 1, characterized in that, In step 2, the refined boundary conditions include: (1) Use the spring element in the finite element software to simulate the elastic support of the support and input its stiffness-displacement curve; (2) At the connection point between the support and the pipeline, the displacement of each support under different working conditions is obtained based on the pipeline thermal expansion analysis results, and the thermal displacement boundary conditions are defined as: axial displacement UX and radial displacement UY. (3) Set up node coupling at the connection between the connecting pipe and the support to simulate the actual connection stiffness.

5. The method for analyzing the vibration stress state of supports and hangers based on finite element analysis according to claim 1, characterized in that, Step 3, the process of obtaining the stress and strain distribution through the static analysis, includes: (i) Set the element type and material properties of the support and hanger in the finite element software; (ii) Mesh the three-dimensional model and refine the mesh in the stress concentration region; (iii) Apply gravitational acceleration, pipe internal pressure, operating temperature field and the thermal displacement boundary conditions described in step (2); (iV) Select the static analysis type to solve the problem and obtain stress and strain contour maps.

6. The method for analyzing the vibration stress state of supports and hangers based on finite element analysis according to claim 1, characterized in that, Step 4, the process of obtaining the natural frequencies and mode shapes through modal analysis, includes: (a) Maintain the prestressed state after completing the static analysis; (b) Switch the analysis type to modal analysis and use the block-based Lanzos method for modal extraction; (c) Solve the characteristic equations of the system to obtain the natural frequencies of each order and their corresponding mode shapes.

7. The method for analyzing the vibration stress state of supports and hangers based on finite element analysis according to any one of claims 1-6, characterized in that, In step 5, if the on-site measurement results and the finite element model calculation results meet the accuracy and design requirements, then the model construction is complete.

8. The method for analyzing the vibration stress state of supports and hangers based on finite element analysis according to any one of claims 1-6, characterized in that, In step 5, if the on-site measurement results and the finite element model calculation results do not meet the accuracy and design requirements, adjust the model parameters and repeat steps 1 to 5 until the requirements are met.

9. The method for analyzing the vibration stress state of supports and hangers based on finite element analysis according to any one of claims 1-6, characterized in that, If the error rate between the on-site measured results and the finite element model calculation results does not exceed 3%, it is determined that the accuracy and design requirements are met; otherwise, they are not met.

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