Method for evaluating sealing performance of pipe joint

Abstract

The invention discloses a method for evaluating the sealing performance of a pipe joint, and the method avoids the defect that the visual inspection of tiny seepage is easy to omit through building the relation between a leakage rate value and an actual leakage phenomenon. Based on a numerical calculation method, the time period and the cost waste of physical verification are saved, the sealing performance can be pre-judged during product design by adopting the method, and the stress index and the sealing contact width index of main structure parameter design are reversely solved according to the sealing performance index; and traceability can be carried out when a leakage fault is sent, a weak link of contact pressure is found, and guidance is brought to improvement of sealing performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of pipeline sealing performance evaluation, and particularly relates to a method for evaluating the sealing performance of a pipe joint. Background Art

[0002] The sealing performance of the pipeline system of an aircraft affects the use functions and performance of the aircraft, and is a key process link that needs to be controlled during the aircraft manufacturing process. The assessment of the sealing performance of pipe joints is mostly carried out through physical verification, and whether there is a leakage phenomenon in the pipe joints under test conditions is used as the judgment basis. With the development of numerical methods and the improvement of computing power, more and more researchers use the finite element method to study the static sealing performance of structures based on design experience. Such methods comprehensively judge by reading the contact pressure and sealing width information of the sealing interface and combining the test verification situation. Both physical verification and numerical calculation methods have the following deficiencies in the evaluation of sealing performance: (1) The evaluation period of physical verification is long and the cost is high. There is a lack of quantitative evaluation indicators for judging whether there is leakage through visual observation. (2) The sources of the sealing width and contact pressure indicators evaluated by the numerical calculation and simulation method are not clear. Most of them are determined by tests or experience, lacking a scientific basis, and it is difficult to establish a direct connection with the actual leakage phenomenon.

[0003] Therefore, in order to evaluate the sealing performance of pipe joints through direct quantitative indicators, the present invention discloses a method for evaluating the sealing performance of pipe joints. Summary of the Invention

[0004] The present invention discloses a method for evaluating the sealing performance of a pipe joint, which can directly and quickly and accurately quantitatively evaluate the structural sealing performance of the pipe joint, and can form an accurate quantitative evaluation system for the sealing performance at the beginning of the design of the pipe joint, thereby providing guarantee for the sealing performance of the subsequently designed pipe joint.

[0005] The present invention is realized through the following technical solutions: A method for evaluating the sealing performance of a pipe joint, the pipe joint includes an extrusion ring, a joint and a conduit, and comprises the following steps: Step 1: Construct an axisymmetric finite element model of the pipe joint with the central axis of the conduit as the reference; Step 2: Apply loads and constraint conditions to the axisymmetric finite element model; Step 3: Set a contact path at the sealing interface of the axisymmetric finite element model, analyze the contact pressure received by the sealing interface, and obtain a pressure curve distributed along the contact path; Step 4: Intercept the sealing width along the contact path according to the pressure value mutation points on the pressure curve, and calculate the average contact pressure within the sealing width range; Step 5: Establish a sealing performance calculation model based on the average contact pressure, calculate the sealing performance index within the current sealing width range through the sealing performance calculation model, and evaluate the sealing performance of the pipe joint based on the sealing performance index.

[0006] In order to better implement the present invention, further, the step 4 specifically includes: Step 4.1, selecting a pressure mutation starting point and a pressure mutation ending point on the pressure curve, and intercepting a pressure mutation area between adjacent pressure mutation starting points and pressure mutation ending points, and calculating the width of the pressure mutation area as the sealing width; Step 4.2, reading all contact pressure data within the sealing width range, and cleaning the contact pressure data; Step 4.3: Calculate the average contact pressure within the sealing width based on the contact pressure data after cleaning.

[0007] In order to better implement the present invention, further, the calculation formula of the average contact pressure within the sealing width range is as follows: ; Where: PS represents the average contact pressure within the seal width; n represents the number of items of contact pressure data after cleaning; Represents the i-th contact pressure data value, 1≤i≤n.

[0008] In order to better implement the present invention, further, cleaning the contact pressure data specifically includes the following steps: Step A1, reading all contact pressure data within the sealing width range to form a data set P, calculating an average value of the contact pressure based on the data set P, and calculating a standard deviation based on the average value of the contact pressure; Step A2, calculating the cleaning threshold value according to the standard deviation, calculating the difference between the contact pressure data and the average value, and if the difference between the contact pressure data and the average value is greater than the cleaning threshold value, filtering the corresponding contact pressure data to form a data set Q; Step A3, remove the elements in the data set P that belong to the data set Q, and execute steps A1 to A2 on the removed data set P; Step A4: Repeat the above steps A1 to A3 until the number of elements in the data set Q is 0.

[0009] In order to better implement the present invention, further, the selection rule of the starting point of the pressure mutation in step 4.1 is: ; in: Indicates the starting point of pressure mutation The next adjacent sampling point The pressure mutation value between Indicates the starting point of pressure mutation The previous sampling point adjacent to it The pressure mutation value between them; The selection rule for the ending point of pressure mutation in step 4.1 is as follows: ; Where: Indicates the ending point of pressure mutation The previous sampling point adjacent to it The pressure mutation value between them; Indicates the ending point of pressure mutation The next sampling point adjacent to it The pressure mutation value between them.

[0010] In order to better implement the present invention, further, the sealing performance calculation model in step 5 is specifically: ; Where: Q represents the sealing performance index; C represents the sealing medium performance index coefficient; D represents the initial diameter of the conduit when it is not under pressure within the sealing width range; H represents the roughness of the conduit wall; w Represents the sealing width; e Represents the natural constant; k represents the sealing material performance coefficient; PS represents the average contact pressure within the sealing width range; Represents the pressure difference between the inside and outside of the pipe joint.

[0011] In order to better implement the present invention, further, step 2 specifically includes: Step 2.1: Apply an axial displacement load to one end of the extrusion ring away from the joint, apply a spring constraint to one end of the conduit close to the axial displacement load, and apply a fixed constraint to one end of the joint away from the axial displacement load; Step 2.2: Preset the stiffness value of the spring constraint, and calculate the reaction force of the spring constraint according to the preset stiffness value; Step 2.3: Adjust the stiffness value according to the reaction force until 5N ≤ reaction force ≤ 10N; Step 2.4: Cancel the spring constraint, cancel the axial displacement load, and retain the fixed constraint to make the axisymmetric finite element model freely rebound.

[0012] In order to better implement the present invention, further, step 3 specifically includes: Step 3.1: Set the contact surface between the joint and the conduit as the sealing interface; Step 3.2: Set a contact path parallel to the central axis of the conduit on the sealing interface; Step 3.3: Read the contact pressure between the joint and the catheter to form a pressure curve distributed along the contact path.

[0013] To better implement the present invention, further, in the step 1, the axisymmetric finite element model is meshed, the global size of the mesh is less than or equal to 0.08 mm, and the size of the mesh for the contact part between the joint and the catheter is greater than or equal to 0.03 mm.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects: The present invention can realize the quantitative evaluation of the sealing performance of the joint structure, establish the connection between the leakage rate value and the actual leakage phenomenon, and avoid the drawback of easy omission in the visual inspection of micro-seepage; based on the numerical calculation method, the present invention saves the time cycle and cost waste of physical verification. By using this method, the sealing performance can be pre-judged during the product design, and the stress index and the sealing contact width index of the main structure parameters design can be inversely obtained according to the sealing performance index; it can also trace the source when a leakage failure occurs, find the weak link of the contact pressure, and provide guidance for improving the sealing performance. Description of the Drawings

[0015] Figure 1 It is a schematic diagram of the flow steps of the sealing performance evaluation method for the pipe joint; Figure 2 It is a schematic diagram of the axisymmetric finite element model; Figure 3 It is a schematic diagram of the pressure curve; Figure 4 It is a schematic diagram of the intercepted sealing width.

[0016] Wherein: 1 - extrusion ring; 2 - joint; 3 - catheter. Detailed Embodiments

[0017] Embodiment 1: A method for evaluating the sealing performance of a pipe joint in this embodiment, the pipe joint includes an extrusion ring 1, a joint 2, and a catheter 3. As Figure 1 shown, it includes the following steps: Step 1: Construct an axisymmetric finite element model of the pipe joint based on the central axis of the catheter 3. The axisymmetric finite element model is as Figure 2 shown; Step 2: Apply loads and constraint conditions to the axisymmetric finite element model; Step 3: Set a contact path at the sealing interface of the axisymmetric finite element model, analyze the contact pressure received by the sealing interface, and obtain a pressure curve distributed along the contact path; Step 4: Intercept the sealing width along the contact path according to the pressure value mutation point on the pressure curve, and calculate the average contact pressure within the sealing width range. Step 5: Establish a sealing performance calculation model based on the average contact pressure, calculate the sealing performance index within the current sealing width range through the sealing performance calculation model, and evaluate the sealing performance of the pipe joint according to the sealing performance index.

[0018] Example 2: A method for evaluating the sealing performance of a pipe joint in this example is improved on the basis of Example 1. Specifically: Step 1: Construct an axisymmetric finite element model of the pipe joint with the central axis of the conduit 3 as the reference. In Step 1, mesh division is performed on the axisymmetric finite element model. The global size of the mesh division is less than or equal to 0.08 mm, and the size of the mesh division at the contact part between the joint 2 and the conduit 3 is greater than or equal to 0.03 mm.

[0019] Step 2: Apply loads and constraint conditions to the axisymmetric finite element model; Step 2 is specifically as follows: Step 2.1: Apply an axial displacement load to the end of the extrusion ring 1 far from the joint 2, apply a spring constraint to the end of the conduit 3 close to the axial displacement load, and apply a fixed constraint to the end of the joint 2 far from the axial displacement load; Step 2.2: Preset the stiffness value of the spring constraint to 50, and calculate the reaction force of the spring constraint according to the preset stiffness value; Step 2.3: Adjust the stiffness value according to the reaction force until 5 N ≤ reaction force ≤ 10 N; Step 2.4: Cancel the spring constraint, cancel the axial displacement load, and retain the fixed constraint to make the axisymmetric finite element model freely rebound.

[0020] Step 3: Set a contact path at the sealing interface of the axisymmetric finite element model, analyze the contact pressure received by the sealing interface, and obtain a pressure curve distributed along the contact path; Step 3 is specifically as follows: Step 3.1: Set the contact surface between the joint 2 and the conduit 3 as the sealing interface; Step 3.2: Set a contact path parallel to the central axis of the conduit 3 on the sealing interface. The direction of the contact path has no influence on the analysis result, and it only needs to ensure that the contact path is parallel to the central axis of the conduit 3; Step 3.3: Read the contact pressure between the joint 2 and the conduit 3 along the contact path to form a pressure curve distributed along the contact path.

[0021] Step 4: Intercept the sealing width along the contact path according to the pressure value mutation point on the pressure curve, and calculate the average contact pressure within the sealing width range; Step 4 is specifically as follows: Step 4.1, selecting a pressure mutation starting point and a pressure mutation ending point on the pressure curve, and intercepting a pressure mutation area between adjacent pressure mutation starting points and pressure mutation ending points, and calculating the width of the pressure mutation area as the sealing width; Step 4.2, reading all contact pressure data within the sealing width range, and cleaning the contact pressure data; Step 4.3: Calculate the average contact pressure within the sealing width based on the contact pressure data after cleaning.

[0022] Furthermore, the calculation formula of the average contact pressure within the sealing width range is as follows: ; Where: PS represents the average contact pressure within the seal width; n represents the number of items of contact pressure data after cleaning; Represents the i-th contact pressure data value, 1≤i≤n.

[0023] Furthermore, cleaning the contact pressure data specifically includes the following steps: Step A1, reading all contact pressure data within the sealing width range to form a data set P, calculating an average value of the contact pressure based on the data set P, and calculating a standard deviation based on the average value of the contact pressure; Step A2, calculating the cleaning threshold value according to the standard deviation, calculating the difference between the contact pressure data and the average value, and if the difference between the contact pressure data and the average value is greater than the cleaning threshold value, filtering the corresponding contact pressure data to form a data set Q; Step A3, remove the elements in the data set P that belong to the data set Q, and execute steps A1 to A2 on the removed data set P; Step A4: Repeat the above steps A1 to A3 until the number of elements in the data set Q is 0.

[0024] Furthermore, the selection rule of the starting point of the pressure mutation in step 4.1 is: ; in: Indicates the starting point of pressure mutation The next adjacent sampling point The pressure mutation value between Indicates the starting point of pressure mutation The previous sampling point adjacent to it The pressure mutation value between The selection rule of the pressure mutation end point in step 4.1 is: ; in: Indicates the end point of the pressure mutation The previous sampling point adjacent thereto The pressure mutation value therebetween; Indicates the end point of pressure mutation The next sampling point adjacent thereto The pressure mutation value therebetween.

[0025] Step 5: Establish a sealing performance calculation model based on the average contact pressure, calculate the sealing performance index within the current sealing width range through the sealing performance calculation model, and evaluate the sealing performance of the pipe joint according to the sealing performance index.

[0026] The sealing performance calculation model in the said Step 5 is specifically: ; Wherein: Q represents the sealing performance index; C represents the sealing medium performance index coefficient; D represents the initial diameter of the conduit when not under pressure within the sealing width range; H represents the roughness of the conduit wall; w Represents the sealing width; e Represents the natural constant; k represents the sealing material performance coefficient; PS represents the average contact pressure within the sealing width range; Represents the pressure difference between inside and outside of the pipe joint.

[0027] Compare the calculated sealing performance index Q with the sealing performance target index QS. If Q > QS, it indicates that the structure within the current sealing width range does not meet the sealing performance requirements; if Q ≤ QS, it indicates that the structure within the current sealing width range meets the sealing performance requirements.

[0028] Example 3: A method for evaluating the sealing performance of a pipe joint in this example is improved on the basis of Example 2, specifically: The pipe joint includes an extrusion ring 1, a joint 2, and a conduit 3. The assembly structure among the three is as Figure 2 shown. The extrusion ring 1 moves axially under the external axial extrusion action. The extrusion ring 1 extrudes the joint 2, and then the joint 2 extrudes the conduit 3, and finally the extrusion is completed to form the final permanent assembly structure.

[0029] Based on the structure of the pipe joint, an axisymmetric finite element model of the pipe joint is constructed with the central axis of the conduit 3 as the reference, and mesh division is performed on the axisymmetric finite element model. In finite element simulation, simulation result data such as stress and pressure are closely related to the mesh size. The smaller the mesh, the higher the calculation accuracy, and the corresponding calculation efficiency will also become lower. In the present invention, considering the calculation efficiency and calculation accuracy, the global mesh size is set to be less than or equal to 0.08 mm; the mesh at the contact part between the conduit 3 and the joint 2 needs to be appropriately refined, and the refinement range is within 2 mm before and after the inner wall groove of the joint 2. Loads and constraint conditions are applied to the axisymmetric finite element model. Apply loads and constraint conditions to the axisymmetric finite element model; Set a spring constraint on one side of the conduit 3, with the initial stiffness value of the spring constraint taken as 50, set a fixed constraint on one side of the joint 2, and apply an axial displacement load at one end of the extrusion ring 1, with the displacement amount being the distance from the outer extrusion end face to the flange end face of the joint.

[0030] Cancel the spring constraint and the axial displacement load, so that the axially extruded part of the axisymmetric finite element model rebounds freely, to simulate the local rebound of the pipe joint as a whole after the external force is removed after the docking of the pipe joint is completed. Canceling the spring constraint and the axial displacement load is the rebound process after the installation of the model pipe joint is completed, and at this time, the stress state of the whole pipe joint will change.

[0031] Set a contact path at the sealing interface of the axisymmetric finite element model, analyze the contact pressure received by the sealing interface, and obtain the pressure curve distributed along the contact path; The area between the conduit 3 and the joint 2 is the sealing evaluation area. Establish a sealing interface in the sealing evaluation area and evaluate the sealing performance based on the sealing pressure of the sealing interface. By reading the contact pressure data between the joint 2 and the conduit 3, the pressure curve distributed along the contact path is obtained as Figure 3 shown.

[0032] Determine the sealing width; According to the obtained pressure curve, read the sealing width of the contact part between the groove part of the joint 2 and the conduit 3. The specific rule for selecting the sealing width is: Select the area width between adjacent pressure mutation starting points and pressure mutation ending points as the sealing width.

[0033] Where: Pressure mutation starting point The selection rule is: ; Pressure mutation ending point The selection rule is: ; As Figure 4 shown, in this embodiment, two sealing widths are selected according to the rules, and are respectively denoted as w 1, w 2, and w 1 = 0.42mm, w 2 = 0.43mm.

[0034] Calculate the sealing performance index of the part to be evaluated; Solve and calculate the average contact stress within the sealing width range. Taking the sealing width w 1 as an example: Take the sealing widthw All contact stress data points within the range of 1 are counted as , where m is the number of contact stress data points, and 1 ≤ i ≤ m; represents the contact pressure corresponding to the i-th contact stress data point.

[0035] Clean the contact stress data set, and the cleaning steps are as follows: Calculate the average value u and standard deviation of the calculated contact stress ; The formula for calculating the average value is: ; where: u represents the average value of the contact pressure; m represents the number of contact stress data points, and 1 ≤ i ≤ m; represents the contact pressure corresponding to the i-th contact stress data point.

[0036] The formula for calculating the standard deviation is: ; where: represents the standard deviation; u represents the average value of the contact pressure; m represents the number of contact stress data points, and 1 ≤ i ≤ m; represents the contact pressure corresponding to the i-th contact stress data point.

[0037] Screen the contact stress data points in the data set P that are greater than the cleaning threshold T to obtain the data set , where the value of T is as follows: ; Screen the data set P according to the number of elements in the data set Q. The specific rules are as follows: If the number of elements in the data set Q is 0, the elements in the data set P do not need to be excluded; if the number of elements in the data set Q is greater than 0, exclude the elements in the data set P that belong to the data set Q, and then repeat the calculation of the sealing performance index and the cleaning operation on the new data set P until the number of elements in the new data set Q is 0. The final formed contact stress data point data set is .

[0038] Based on the new data set Obtain the average contact pressure within the sealing width range:

[0039] where: PS represents the average contact pressure within the sealing width range; n represents the number of items of the contact pressure data after cleaning; represents the i-th contact pressure data value, and 1 ≤ i ≤ n.

[0040] Finally, calculate the sealing width wThe average contact pressure PS1 within the range 1 is 623.843.

[0041] The following sealing performance calculation model is established: ; Where: Q represents the sealing performance index; C represents the sealing medium performance index coefficient, which is related to the sealing medium and the working environment temperature. In this embodiment, helium is used as the working medium, the working environment temperature is taken as 20 °C, and the corresponding coefficient is taken as 1107.156 m / s; D represents the initial diameter of the conduit when it is not under pressure within the sealing width range. In this embodiment, D1 = 8 mm is taken; H represents the roughness of the conduit wall. In this embodiment, H = 0.8 ; w represents the sealing width; e represents the natural constant; k represents the sealing material performance coefficient, which is related to the sealing interface material. In this implementation, the material of the extrusion ring 1 is TC4, and the material of the joint 2 is TC4. In this embodiment, k = -0.023 MPa is taken -1 ; PS represents the average contact pressure within the sealing width range; represents the pressure difference between the inside and outside of the pipe joint. In this embodiment, = 2 Mpa.

[0042] is the pressure difference between the inside and outside of the joint. In this embodiment, the pressure difference between the inside and outside of the joint is 2 MPa.

[0043] Based on the above formula, substituting w 1 and w 2 values, that is, the w 1 = 0.42 mm calculated above, w 2 = 0.43 mm.

[0044] The pressure performance index corresponding to the pressure width w 1 is obtained as: Q1 = 1.48×10 -8 Pa∙m 3 / s; The pressure performance index corresponding to the pressure width w 2 is obtained as: Q2 = 5.18×10 -7 Pa∙m 3 / s; The calculated sealing performance index Q is compared with the sealing performance target index QS. Take QS = 1×10 -7 Pa∙m 3 / s.

[0045] Since Q1 < QS, it indicates that the structure within the pressure width w 1 meets the sealing performance requirements; If Q2 > QS, it indicates that the structure within the pressure width w 2 does not meet the sealing performance requirements.

[0046] Therefore, it is necessary to improve the structure within the pressure width w 2, for example, increasing the outer diameter size of the structure within the pressure width w 2, reducing the inner diameter size of the structure within the pressure width w 2, adjusting the interval or tolerance of the grooves in the structure within the pressure width w 2.

[0047] As described above, it is only a preferred embodiment of the present invention and does not impose any form of limitation on the present invention. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for evaluating the sealing performance of a pipe joint, the pipe joint comprising an extrusion ring (1), a joint (2), and a conduit (3), characterized in that, The following steps are involved: Step 1: construct an axisymmetric finite element model of the pipe joint based on the central axis of the conduit (3); Step 2, applying loads and constraints to the axisymmetric finite element model; Step 3: setting a contact path on the sealing interface of the axisymmetric finite element model, analyzing the contact pressure on the sealing interface, and obtaining a pressure curve distributed along the contact path; Step 4: intercept the sealing width along the contact path according to the pressure value mutation point on the pressure curve, and calculate the average contact pressure within the sealing width; Step 5: Establish a sealing performance calculation model based on the average contact pressure, calculate the sealing performance index within the current sealing width range through the sealing performance calculation model, and evaluate the sealing performance of the pipe joint based on the sealing performance index.

2. The sealing performance evaluation method of a pipe joint according to claim 1, characterized in that The step 4 specifically includes: Step 4.1, selecting a pressure mutation starting point and a pressure mutation ending point on the pressure curve, and intercepting a pressure mutation area between adjacent pressure mutation starting points and pressure mutation ending points, and calculating the width of the pressure mutation area as the sealing width; Step 4.2, reading all contact pressure data within the sealing width range, and cleaning the contact pressure data; Step 4.3: Calculate the average contact pressure within the sealing width based on the contact pressure data after cleaning.

3. The sealing performance evaluation method of a pipe joint according to claim 2, characterized in that, The average contact pressure within the seal width is calculated as follows: ； Where: PS represents the average contact pressure within the sealing width range; n represents the number of items of the contact pressure data after cleaning; represents the i-th contact pressure data value, where 1 ≤ i ≤ n.

4. The sealing performance evaluation method of a pipe joint according to claim 3, characterized in that, Cleaning the contact pressure data specifically includes the following steps: Step A1, reading all contact pressure data within the sealing width range to form a data set P, calculating an average value of the contact pressure based on the data set P, and calculating a standard deviation based on the average value of the contact pressure; Step A2, calculating the cleaning threshold value according to the standard deviation, calculating the difference between the contact pressure data and the average value, and if the difference between the contact pressure data and the average value is greater than the cleaning threshold value, filtering the corresponding contact pressure data to form a data set Q; Step A3, remove the elements in the data set P that belong to the data set Q, and execute steps A1 to A2 on the removed data set P; Step A4: Repeat the above steps A1 to A3 until the number of elements in the data set Q is 0.

5. The sealing performance evaluation method of a pipe joint according to claim 4, characterized in that, The selection rule of the starting point of the pressure mutation in step 4.1 is: ； Wherein: represents the starting point of pressure mutation and the subsequent sampling point adjacent thereto the pressure mutation value therebetween; represents the starting point of pressure mutation and the previous sampling point adjacent thereto the pressure mutation value therebetween; The selection rule of the pressure mutation end point in step 4.1 is: ； Wherein: Indicates the end point of pressure mutation The pressure mutation value between it and the previous adjacent sampling point ; Indicates the end point of pressure mutation The pressure mutation value between it and the next adjacent sampling point ; 6. A method for evaluating the sealing performance of a pipe joint according to any one of claims 1-5, characterized in that, The sealing performance calculation model in step 5 is specifically: ； Where: Q represents the sealing performance index; C represents the sealing medium performance index coefficient; D represents the initial diameter of the conduit when it is not under pressure within the sealing width; H represents the roughness of the conduit wall; w represents the sealing width; e represents the natural constant; k represents the sealing material performance coefficient; PS represents the average contact pressure within the sealing width; represents the pressure difference between inside and outside of the pipe joint.

7. A method for evaluating the sealing performance of a pipe joint according to any one of claims 1-5, characterized in that The step 2 specifically includes: Step 2.1, applying an axial displacement load to the end of the extrusion ring (1) away from the joint (2), applying a spring constraint to the end of the conduit (3) close to the axial displacement load, and applying a fixed constraint to the end of the joint (2) away from the axial displacement load; Step 2.2, preset the stiffness value of the spring constraint, and calculate the support reaction force of the spring constraint according to the preset stiffness value; Step 2.3, adjust the stiffness value according to the support reaction force until 5N≤support reaction force≤10N; Step 2.4, cancel the spring constraint, cancel the axial displacement load, retain the fixed constraint, and allow the axisymmetric finite element model to rebound freely.

8. A method for evaluating the sealing performance of a pipe joint according to any one of claims 1-5, characterized in that, The step 3 specifically includes: Step 3.1, setting the contact surface between the connector (2) and the catheter (3) as a sealing interface; Step 3.2, setting a contact path parallel to the central axis of the catheter (3) on the sealing interface; Step 3.3: Read the contact pressure between the joint (2) and the catheter (3) along the contact path to form a pressure curve distributed along the contact path.

9. A method for evaluating the sealing performance of a pipe joint according to any one of claims 1-5, characterized in that, In the said Step 1, mesh division is performed on the axisymmetric finite element model. The global dimension of the mesh division is less than or equal to 0.08 mm, and the dimension of the mesh division at the contact part between the joint (2) and the catheter (3) is greater than or equal to 0.03 mm.

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