Grading numerical simulation method for the connection performance of metal UE sealing flanges

Abstract

The hierarchical numerical simulation method for the connection performance of metal U-E sealing flanges of the present invention is based on the structure and load characteristics of the metal U-E sealing flanges. It provides a simplified strategy for establishing a four-level model in the finite element software ABAQUS, a method for setting materials, boundaries, loads, and contact relationships, meshing principles, and requirements for outputting calculation results. A specific method for using the four-level model to respectively obtain the compression-rebound performance of the sealing ring itself, the contact performance of the sealing ring itself, and the stress, strain, and deformation response of the sealing flange connection structure under preload and working conditions is established, forming a complete hierarchical numerical simulation method for the connection performance of metal U-E sealing flanges.

Description

Technical Field

[0001] The invention relates to a hierarchical numerical simulation method for the connection performance of a metal UE sealing flange. Background Art

[0002] The metal UE seal consists of a U-shaped (main) seal and an E-shaped (secondary) seal. During operation, the medium is filled between the main seal legs. It has a self-tightening function under the premise of ensuring that the opening amount of the sealing channel is less than the sealing rebound amount under the working condition. After the main seal fails, the secondary seal has a certain secondary sealing ability, which is common in liquid rocket engine high-temperature and high-pressure pipeline systems. Sealing leakage is the most common failure form of the metal UE sealing flange connection structure. Accurately evaluating its connection performance (sealing, strength, and stiffness) is extremely important for the safety of the engine pipeline system. The sealing performance of the metal sealing ring needs to be determined based on the compression-rebound response, contact pressure, and contact width changes when the sealing ring is pre-tightened to the working state. The soft metal coating on the surface of the sealing ring has little effect on the compression-rebound performance, but strongly affects the contact performance. The coating thickness (10 -2 There is a significant scale difference between the flange connection structure and the flange connection structure (mm level). It is difficult to strike a balance between calculation accuracy and calculation cost using conventional calculation strategies. Summary of the Invention

[0003] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology, based on the structural characteristics and load conditions of the metal UE sealing flange, establish a specific method using a four-level model to obtain the compression-rebound performance of the sealing ring itself, the contact performance of the sealing ring itself, and the stress, strain and deformation response of the sealing flange connection structure under pre-tightening and working conditions, forming a complete set of graded numerical simulation methods for the connection performance of metal UE sealing flanges.

[0004] The technical solution of the present invention is: a hierarchical numerical simulation method for the connection performance of metal UE sealing flanges, comprising:

[0005] Establish a Level I model and perform compression-rebound performance calculations on the sealing ring; in the Level I model, no coating is built, and the sealing ring is compressed by a rigid surface; compress the sealing ring to a given compression amount and then unload it, and calculate the axial load-displacement curve of the sealing ring during the loading and unloading process; modify the compression amount and repeat the calculation N times to obtain the axial load-displacement curves of the sealing ring during the loading and unloading process with N different compression amounts; and draw a rebound-compression curve;

[0006] Establish a Level II model and carry out contact performance calculation of the sealing ring; establish a coating in the Level II model, consider the influence of the mechanical properties and thickness of the coating on the contact characteristics, and compress the sealing ring by the rigid surface; compress the sealing ring to a given compression amount and then unload it, calculate the contact pressure distribution along the path on the sealing lip when compressed in place, and the contact pressure distribution along the path on the sealing lip under different opening amounts during the compression unloading process; modify the compression amount, repeat the calculation M times, and plot the average contact pressure-compression displacement curve of the sealing lip and the sealing lip contact width-compression displacement curve of the obtained M groups of calculation results; plot the average contact pressure-opening displacement curve of the sealing lip and the sealing lip contact width-opening displacement curve for each compression amount;

[0007] A Level III model was established to conduct a two-dimensional axisymmetric stress, strain, and deformation response analysis of the sealing ring and flange. The Level III model omitted plating and bolts, ignored flange lightening holes and bolt holes, and used a pair of equal forces to simulate the compression of the bolts on the upper and lower flanges. The compression, contact force, stress, and strain distribution of the sealing ring in the preloaded state were calculated, as were the contact force, stress, and strain distribution of the sealing ring in the working state, as well as the flange opening, stress, and strain distribution in the working state.

[0008] A Level IV model is established to carry out three-dimensional stress, strain and deformation response analysis of the sealing ring-flange-fastener; no coating is built in the Level IV model, but bolts are built; the compression, contact force, stress and strain distribution of the sealing ring in the pre-tightened state, the contact force, stress and strain distribution of the sealing ring in the working state, the flange opening, stress and strain distribution in the working state, and the axial load, stress and strain distribution of the fastener in the working state are calculated.

[0009] The establishment of the Level I model and the calculation of the compression-rebound performance of the sealing ring include:

[0010] Step 101: Extract the annular cross-section of the sealing ring. The UE sealing ring still has a symmetrical surface along the axial direction. Only the lower half of the sealing ring model is retained. A straight line tangent to the lower primary and secondary sealing lips is drawn as the rigid surface of the compression sealing ring.

[0011] Step 102 , establishing the sealing ring material properties, inputting the elastic modulus, Poisson's ratio, and true stress-strain curve of the sealing ring base material;

[0012] Step 103: Set the contact relationship. Set a contact pair between the sealing ring and the rigid surface. Set the rigid surface as the primary contact surface, and the sealing lip and sealing ring limit surfaces as the secondary contact surfaces. Select "Limited Slip" for the slip equation and "Node-to-Phase" for the discretization method.

[0013] Step 104 , meshing the sealing ring geometric model using a quadrilateral axisymmetric linear reduced integration unit;

[0014] Step 105, constraining the axial displacement of the axially symmetric surface of the sealing ring; establishing two static analysis steps: the first step is used to apply axial compression displacement at the reference point of the rigid surface, and the second step is used to remove all axial compression displacement;

[0015] Step 106: Generate a job and run the model calculation. After the calculation is completed, output the axial load-displacement curves of the loading and unloading history for each of the primary and secondary sealing lips. Calculate the rebound amount of each of the primary and secondary sealing lips after the compression displacement is completely removed at the current compression amount. Rebound amount = compression amount - remaining compression amount after unloading.

[0016] Step 107, modify the compression amount, repeat step 106 N times; based on the calculation results, draw the rebound amount-compression amount curve of the primary and secondary sealing lips respectively.

[0017] In the calculation of compression-rebound performance, N different compression amounts are used to load and unload the rigid surface in the Level I model, where the maximum compression amount = the maximum axial height of the sealing ring - the axial height of the limit surface, 0.25×maximum compression amount ≤ minimum compression amount ≤ 0.5×maximum compression amount, and intermediate values ​​can be evenly set between the maximum and minimum values.

[0018] The requirements to be met when performing grid division in step 104 include:

[0019] There are enough nodes near the sealing lip to describe the arc-shaped profile of the sealing lip;

[0020] There are enough unit layers along the thickness direction at the root of the sealing leg to describe the stress and strain gradient at the root of the sealing leg;

[0021] The rigid surface is set as an analytical rigid body and no meshing is performed.

[0022] The establishment of the Level II model and the calculation of the contact performance of the sealing ring include:

[0023] Step 201: Establish a two-dimensional axisymmetric geometric model according to step 101; cut out a strip area with a width equal to the coating thickness in the area where the sealing lip may come into contact with the rigid surface along the contour line of the sealing lip;

[0024] Step 202 , establishing the sealing ring material properties, inputting the elastic modulus, Poisson's ratio, and true stress-strain curve of the sealing ring substrate and the coating material;

[0025] Step 203: Set the contact relationship. Set a contact pair between the sealing ring and the rigid surface. Set the rigid surface as the primary contact surface, and the sealing lip and sealing ring limit surfaces as the secondary contact surfaces. Select "Limited Slip" for the slip equation and "Node-to-Phase" for the discretization method.

[0026] Step 204 , meshing the sealing ring geometric model using a quadrilateral axisymmetric linear reduced integration unit;

[0027] Step 205: constraining the axial displacement of the axially symmetric surface of the sealing ring; establishing two static analysis steps: the first step is used to apply a given axial compression amount at the reference point of the rigid surface, and the second step is used to remove all axial compression displacements;

[0028] Step 206: Generate a job and run the model calculation. After the calculation is completed, output the contact pressure along the outer contour of the sealing lip at the end of the first analysis step, and the contact pressure along the paths on the primary and secondary sealing lips of the sealing ring when the axial compression is released by a certain amount in the second analysis step.

[0029] Step 207, modify the compression amount, repeat step 206 M times, and draw contact pressure-position curves along the outer contour lines of the primary and secondary sealing lips under different compression amounts.

[0030] The step 207 draws contact pressure-position curves of the paths along the outer contour lines of the main and auxiliary sealing lips under different compression amounts, including: for each compression amount, drawing contact pressure-distance curves of the paths along the outer contour lines of the main and auxiliary sealing lips under different opening displacements during the compression unloading process; based on the obtained M groups of calculation results, drawing the average contact pressure-compression displacement curve of the main sealing lip, the contact width-compression displacement curve of the main sealing lip, the average contact pressure-compression displacement curve of the auxiliary sealing lip, and the contact width-compression displacement curve of the auxiliary sealing lip; for each compression amount, drawing the average contact pressure-opening displacement curve of the main sealing lip, the contact width-opening displacement curve of the main sealing lip, the average contact pressure-opening displacement curve of the auxiliary sealing lip, and the contact width-opening displacement curve of the auxiliary sealing lip.

[0031] The requirements for meshing in step 204 include:

[0032] The unit size in the coating area is 0.001~0.01mm, and is not less than 5 layers of units along the coating thickness direction. The size of the coating unit along the thickness direction is twice that along the contour line direction;

[0033] The unit size of the rest of the sealing ring is 0.05 to 0.1 mm;

[0034] The coating unit and the base unit are treated as common nodes; the rigid surface adopts analytical rigid body and no meshing is performed.

[0035] The establishment of the Level III model and the implementation of the two-dimensional axisymmetric stress, strain and deformation response analysis of the sealing ring and flange include:

[0036] Step 301: Delete the bolt holes on the flange and extract the annular cross-section of the upper and lower flanges and the sealing ring passing through the bolt axis.

[0037] Step 302: Establish the material properties of the sealing ring and flange, and input the elastic modulus, Poisson's ratio, and true stress-strain curve of the sealing ring base and flange materials respectively;

[0038] Step 303: Set the contact relationship. Set contact pairs between the sealing ring and the flange groove, and between the upper and lower flange mating positions. In the contact pair between the sealing ring and the flange groove, the sealing ring is the secondary contact surface, the flange groove is the primary contact surface, the sliding equation is "limited slip", and the discrete method is "node face to face". For the contact pair between the upper and lower flange mating positions, the sliding equation is "limited slip", and the discrete method is "face to face".

[0039] Step 304: Use quadrilateral axisymmetric linear reduced integration elements to perform finite element meshing on the sealing ring and flange geometric models. Locally refine the finite element meshes near the sealing ring and flange grooves. The mesh size requirements for the sealing ring are the same as those for the Level I model. The mesh sizes of the master and slave surfaces of the contact pair are the same.

[0040] Step 305: Set the flange boundary based on the stiffness of the actual piping system in which the flange is located. Establish two static analysis steps: the first step is used to apply a preload. A gasket diameter area is cut out on the upper flange and bolt gasket compression surface, and a bolt hole area is cut out on the lower flange limit surface. A pair of equal forces are applied to simulate the preload. The second step is used to apply the working load.

[0041] Step 306: Generate a job and run the model calculation. After the calculation is completed, output the compression amount and contact force at the primary and secondary sealing lips, and the stress and strain distribution of the sealing ring at the end of the first step. Output the contact force at the primary and secondary sealing lips, and the stress and strain distribution of the sealing ring at the end of the second step. Output the opening amount of the contact position between the flange and the primary and secondary sealing lips, and the stress and strain distribution of the upper and lower flanges at the end of the second step.

[0042] The establishment of the IV level model and the three-dimensional stress, strain and deformation response analysis of the sealing ring-flange-fastener are carried out, including:

[0043] Step 401: cut out a periodically symmetrical sector containing a bolt from the seal-flange-fastener three-dimensional geometric model and perform geometric cleaning on it;

[0044] Step 402: Establish the material properties of the sealing ring and flange, and input the elastic modulus, Poisson's ratio, and true stress-strain curve of the sealing ring base and flange materials, respectively.

[0045] Step 403: Set contact relationships. Set contact pairs between the sealing ring and the flange sealing ring groove, between the upper flange and the lower flange mating surfaces, between the bolt and the bolt hole wall, between the bolt and the gasket, and between the gasket and the upper flange. For the contact alignment between the sealing ring and the flange ring groove, the sealing ring is the secondary contact surface and the flange ring groove is the primary contact surface. Select "Limited Slip" for the slip equation and "Node Face to Face" for the discretization method. Select "Limited Slip" for the slip equation and "Face to Face" for the discretization method.

[0046] Step 404 , using second-order tetrahedral elements combined with hexahedral linear reduced integration elements to perform finite element meshing on the sealing ring-flange-fastener three-dimensional geometric model, and locally refine the finite element meshes near the sealing ring and flange groove;

[0047] Step 405: Set the flange boundary according to the stiffness of the actual pipeline system where the flange is located, and apply a periodic symmetric boundary; establish two static analysis steps: the first step is used to apply the bolt preload; the second step is used to apply the working load;

[0048] Step 406: Generate a job and run the model calculation. After the calculation is completed, output the compression amount and contact force at the primary and secondary sealing lips, and the stress and strain distribution of the sealing ring at the end of the first step. Output the contact force at the primary and secondary sealing lips, and the stress and strain distribution of the sealing ring at the end of the second step. Output the opening amount of the contact position between the flange and the primary and secondary sealing lips, and the stress and strain distribution of the upper and lower flanges at the end of the second step. Output the axial load of the bolt at the end of the second step.

[0049] Said N=4-10; M=4-10.

[0050] The beneficial effects of the present invention are as follows: the Class I model established by the present invention can accurately calculate the compression-rebound performance of the sealing ring itself; the Class II model established can accurately calculate the contact performance of the sealing ring itself; the Class III model established can quickly calculate the deformation and stress state of the sealing ring-flange structure in pre-tightening and operating conditions; the Class IV model established is a three-dimensional periodic symmetric model including fasteners, which can reflect the changes in the clamping force of the fasteners on the upper and lower flanges from pre-tightening to working conditions, the differences in the circumferential compression, opening, stress, strain, etc. of the sealing ring-flange structure, and the stress concentration caused by the bolt holes and weight reduction holes, thereby accurately calculating the deformation and stress state of the sealing ring-flange-fastener structure in pre-tightening and operating conditions. According to the four-level modeling and analysis method proposed by the present invention, the contact pressure distribution and contact width of the metal sealing flange under pre-tightening and working conditions can be accurately calculated, and the sealing performance can be comprehensively evaluated; after formulating the execution process of the four-level analysis, the connection performance of the metal UE sealing flange structure can be evaluated and optimized layer by layer, and the structural design can be completed with as few iterations and as small a calculation scale as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a diagram of the level I finite element model;

[0052] Figure 2 The main sealing lip axial load-displacement curve;

[0053] Figure 3 is the auxiliary sealing lip axial load-displacement curve;

[0054] Figure 4 The rebound-compression curve of the main and auxiliary sealing lips;

[0055] Figure 5 It is the local mesh near the sealing lip of the level II finite element model and the diagram of path-1 along the sealing lip;

[0056] Figure 6 The contact pressure-path distance curve along the outer contour of the main sealing lip under different compression amounts;

[0057] Figure 7 The contact pressure-path distance curve along the outer contour of the auxiliary sealing lip under different compression amounts;

[0058] Figure 8 The contact pressure-path distance curve along the outer contour of the main sealing lip under different opening amounts;

[0059] Figure 9 The contact pressure-path distance curve along the outer contour of the auxiliary sealing lip under different opening amounts;

[0060] Figure 10 Main sealing lip contact pressure mean-compression curve, contact width-compression curve;

[0061] Figure 11 The secondary seal lip contact pressure mean-compression curve, contact width-compression curve;

[0062] Figure 12 Main sealing lip contact pressure mean-opening curve, contact width-opening curve;

[0063] Figure 13 The secondary sealing lip contact pressure mean-opening curve, contact width-opening curve;

[0064] Figure 14 It is a diagram of the level III finite element model;

[0065] Figure 15 It is a diagram of the level IV finite element model; DETAILED DESCRIPTION

[0066] A Level I finite element (axisymmetric compression-rebound performance analysis) model was established in the finite element software ABAQUS, and a Level I numerical simulation was performed, including steps 101 to 107:

[0067] (1) Step 101, extract the annular cross section of the sealing ring. The UE sealing ring still has a symmetrical surface along the axial direction. Only the lower half model of the sealing ring is retained. A straight line tangent to the lower main and auxiliary sealing lips is drawn as the rigid surface of the compression sealing ring, as shown in the attached figure. Figure 1 As shown;

[0068] (2) Step 102, establishing the sealing ring material properties, inputting the elastic modulus, Poisson's ratio and true stress-strain curve of the sealing ring base material;

[0069] (3) Step 103: Set the contact relationship. Set a contact pair between the sealing ring and the rigid surface. Set the rigid surface as the primary contact surface, and the sealing lip and sealing ring limit surfaces as the secondary contact surfaces. Select "limited slip" for the slip equation and "node-to-face" for the discretization method.

[0070] (4) Step 104: Use the quadrilateral axisymmetric linear reduced integration element (CAX4R) to mesh the sealing ring geometry model, with the following requirements:

[0071] 1) There are enough nodes near the sealing lip to describe the arc-shaped profile of the sealing lip;

[0072] 2) There are enough unit layers along the thickness direction at the root of the sealing leg to describe the stress and strain gradients at the root of the sealing leg;

[0073] 3) The rigid surface is set as an analytical rigid body and does not need to be meshed;

[0074] (5) Step 105, constraining the axial displacement of the axially symmetric surface of the sealing ring; establishing two static analysis steps: the first step is used to apply axial compression displacement at the reference point of the rigid surface, and the second step is used to remove all axial compression displacement;

[0075] (6) Step 106: Generate a job and submit it for analysis. After the calculation is completed, the axial load-displacement curves of the loading and unloading processes of the main and auxiliary sealing lips are output respectively. The rebound amount of the main and auxiliary sealing lips after the compression displacement is completely removed under the current compression amount is calculated, as shown in the attached figure. Figure 2 and 3 As shown in the figure, the calculation method of the sealing lip rebound is:

[0076] Rebound amount = compression amount - remaining compression amount after unloading;

[0077] (7) Step 107, modify the compression amount, repeat step 106 N times; based on the calculation results, draw the rebound amount-compression amount curve of the main and auxiliary sealing lips respectively, as shown in the attached figure. Figure 4 As shown;

[0078] In the compression-rebound performance calculation, N different compression amounts are used to load and unload the rigid surface in the Level I model, where the maximum compression amount = the maximum axial height of the sealing ring - the axial height of the limit surface, 0.25×the maximum compression amount ≤ the minimum compression amount ≤ 0.5×the maximum compression amount, and intermediate values ​​between the maximum and minimum values ​​can be evenly set; the N value is 4 to 10.

[0079] A Level II finite element (axisymmetric contact performance analysis) model was established in the finite element software ABAQUS, and a Level II numerical simulation was performed, including steps 201 to 207:

[0080] (8) Step 201: Establish a two-dimensional axisymmetric geometric model according to step 101; along the contour line of the sealing lip, cut out a strip area with a width equal to the thickness of the coating in the area where it may come into contact with the rigid surface, as shown in the attached figure. Figure 5 As shown;

[0081] (9) Step 202, establishing the sealing ring material properties, inputting the elastic modulus, Poisson's ratio and true stress-strain curve of the sealing ring substrate and the coating material;

[0082] (10) Step 203: Set the contact relationship. Set a contact pair between the sealing ring and the rigid surface. Set the rigid surface as the primary contact surface, and the sealing lip and sealing ring limit surfaces as the secondary contact surfaces. Select "limited slip" for the slip equation and "node-to-face" for the discrete mode.

[0083] (11) Step 204, meshing the sealing ring geometry model using a quadrilateral axisymmetric linear reduced integration element (CAX4R), with the following requirements:

[0084] 1) The unit size in the coating area is 0.001~0.01mm, and is not less than 5 layers of units along the coating thickness direction. The size of the coating unit along the thickness direction is twice that along the contour line direction;

[0085] 2) The unit size of the rest of the sealing ring is 0.05-0.1 mm, which makes the grid transition reasonable and the model scale appropriate;

[0086] 3) The coating unit and the base unit are treated as a common node;

[0087] 4) Rigid surfaces use analytical rigid bodies and do not require meshing;

[0088] (12) Step 205, constraining the axial displacement of the axially symmetric surface of the sealing ring; establishing two static analysis steps: the first step is used to apply a given axial compression amount at the reference point of the rigid surface, and the second step is used to remove all axial compression displacements;

[0089] (13) Step 206, generate the job and submit it for analysis; after the calculation is completed, output the path along the outer contour line of the sealing lip at the end of the first step (path -1, as shown in the attached figure). Figure 5 The contact pressure along the path on the primary and secondary sealing lips of the sealing ring when the axial compression in the second step is relieved by a certain amount (that is, when the sealing ring is opened by a certain amount relative to the compressed state);

[0090] (14) Step 207, modify the compression amount, repeat step 206 M times, and draw the contact pressure-position curves along the outer contour lines of the main and auxiliary sealing lips under different compression amounts, as shown in the attached figure. Figure 6 and 7 As shown in the figure; for each compression amount, the contact pressure-distance curve along the outer contour line of the main and auxiliary sealing lips under different opening displacements during the compression unloading process is drawn, as shown in the attached figure. Figure 8 and 9 As shown; Based on the obtained M group calculation results, the main sealing lip average contact pressure-compression displacement curve, the main sealing lip contact width-compression displacement curve, the auxiliary sealing lip average contact pressure-compression displacement curve, and the auxiliary sealing lip contact width-compression displacement curve are plotted; for each compression amount, the main sealing lip average contact pressure-opening displacement curve, the main sealing lip contact width-opening displacement curve, the auxiliary sealing lip average contact pressure-opening displacement curve, and the auxiliary sealing lip contact width-opening displacement curve are plotted, as shown in the attached figure. Figures 10-13 shown.

[0091] A Level III finite element model is established in the finite element software ABAQUS, and a Level III numerical simulation is performed, including steps 301 to 306:

[0092] (15) Step 301, delete the bolt holes on the flange, extract the annular section of the (upper and lower) flange and the sealing ring through the bolt axis position, as shown in the attached figure. Figure 14 As shown;

[0093] (16) Step 302, establishing the material properties of the sealing ring and flange, inputting the elastic modulus, Poisson's ratio and true stress-strain curve of the sealing ring base and flange materials respectively;

[0094] (17) Step 303, set the contact relationship, set the contact pairs between the sealing ring and the flange ring groove, and between the upper and lower flange matching positions; in the contact pair between the sealing ring and the flange ring groove, the sealing ring is the secondary contact surface, the flange ring groove is the primary contact surface, the sliding equation is selected as "finite slip", and the discrete method is selected as "node face to face"; for the contact pair between the upper and lower flange matching positions, the sliding equation is selected as "finite slip", and the discrete method is selected as "face to face";

[0095] (18) Step 304: Use the quadrilateral axisymmetric linear reduced integration element (CAX4R) to perform finite element meshing on the sealing ring and flange geometric model. Locally refine the finite element mesh near the sealing ring and flange ring groove. The mesh size requirement for the sealing ring is the same as that of the Level I model. The mesh size of the master and slave surfaces of the contact pair is the same.

[0096] (19) Step 305, set the flange boundary according to the stiffness of the actual pipeline system where the flange is located; establish two static analysis steps: the first step is to apply the preload, cut out the gasket diameter area on the upper flange and the bolt gasket pressing surface, cut out the bolt hole area on the lower flange limit surface, and apply a pair of equal forces to simulate the preload; the second step is to apply the working load, and the medium pressure application area is as shown in the attached figure. Figure 14 shown.

[0097] (20) Step 306, generate the job and submit it for analysis; after the calculation is completed, output the compression amount and contact force at the primary and secondary sealing lips, the stress and strain distribution of the sealing ring at the end of the first step; output the contact force at the primary and secondary sealing lips, the stress and strain distribution of the sealing ring at the end of the second step; output the opening amount of the contact position between the flange and the primary and secondary sealing lips at the end of the second step, and the stress and strain distribution of the upper and lower flanges.

[0098] A Level IV finite element model is established in the finite element software ABAQUS, and a Level IV numerical simulation is performed, including steps 401 to 406:

[0099] (21) Step 401, cutting out a periodically symmetrical sector containing a bolt from the seal-flange-fastener three-dimensional geometric model and performing geometric cleaning on it;

[0100] (22) Step 402, establishing the material properties of the sealing ring and flange, inputting the elastic modulus, Poisson's ratio and true stress-strain curve of the sealing ring base and flange materials respectively;

[0101] (23) Step 403, set the contact relationship, and set contact pairs between the sealing ring and the flange sealing ring groove, between the upper flange and the lower flange mating surface, between the bolt and the bolt hole wall, between the bolt and the gasket, and between the gasket and the upper flange. In the contact alignment between the sealing ring and the flange ring groove, the sealing ring is the secondary contact surface, the flange ring groove is the primary contact surface, the slip equation is selected as "finite slip", and the discrete method is selected as "node face to face"; the slip equation is selected as "finite slip", and the discrete method is selected as "face to face";

[0102] (24) Step 404, the second-order tetrahedral element (C3D10) combined with the hexahedral linear reduced integration element (C3D8R) is used to perform finite element meshing on the sealing ring-flange-fastener three-dimensional geometric model, and the finite element mesh near the sealing ring and flange ring groove is locally refined, as shown in the attached figure. Figure 15 As shown;

[0103] (25) Step 405: Set the flange boundary according to the stiffness of the actual pipeline system where the flange is located, and apply a periodic symmetric boundary; establish two static analysis steps: the first step is used to apply the bolt preload; the second step is used to apply the working load;

[0104] (26) Step 406, generate the job and submit it for analysis; after the calculation is completed, output the compression amount and contact force at the primary and secondary sealing lips, the stress and strain distribution of the sealing ring at the end of the first step; output the contact force at the primary and secondary sealing lips, the stress and strain distribution of the sealing ring at the end of the second step; output the opening amount of the contact position between the flange and the primary and secondary sealing lips at the end of the second step, the stress and strain distribution of the upper and lower flanges, and output the axial load of the bolt at the end of the second step.

Claims

1. A graded numerical simulation method for the connection performance of metal UE sealing flanges, characterized by include: Establish a Level I model and perform compression-rebound performance calculations on the sealing ring; In the Level I model, no coating is built, and the sealing ring is compressed by the rigid surface; the sealing ring is compressed to a given compression amount and then unloaded, and the axial load-displacement curve of the sealing ring during the loading and unloading process is calculated; Modify the compression amount and repeat the calculation N times to obtain the axial load-displacement curves of the sealing ring during the loading and unloading processes with N different compression amounts; draw the rebound amount-compression amount curve; Establish a Level II model and carry out contact performance calculation of the sealing ring; establish a coating in the Level II model, consider the influence of the mechanical properties and thickness of the coating on the contact characteristics, and compress the sealing ring by the rigid surface; compress the sealing ring to a given compression amount and then unload it, calculate the contact pressure distribution along the path on the sealing lip when compressed in place, and the contact pressure distribution along the path on the sealing lip under different opening amounts during the compression unloading process; modify the compression amount, repeat the calculation M times, and plot the average contact pressure-compression displacement curve of the sealing lip and the sealing lip contact width-compression displacement curve of the obtained M groups of calculation results; plot the average contact pressure-opening displacement curve of the sealing lip and the sealing lip contact width-opening displacement curve for each compression amount; A Level III model was established to conduct a two-dimensional axisymmetric stress, strain, and deformation response analysis of the sealing ring and flange. The Level III model omitted plating and bolts, ignored flange lightening holes and bolt holes, and used a pair of equal forces to simulate the compression of the bolts on the upper and lower flanges. The compression, contact force, stress, and strain distribution of the sealing ring in the preloaded state were calculated, as were the contact force, stress, and strain distribution of the sealing ring in the working state, as well as the flange opening, stress, and strain distribution in the working state. Establish a Level IV model and conduct a three-dimensional stress, strain, and deformation response analysis of the sealing ring-flange-fastener; the Level IV model does not include a coating, but establishes bolts; Calculate the compression, contact force, stress and strain distribution of the sealing ring in the preloaded state; the contact force, stress and strain distribution of the sealing ring in the working state; the flange opening, stress and strain distribution in the working state; and the axial load, stress and strain distribution of the fastener in the working state.

2. The hierarchical numerical simulation method for the connection performance of metal UE sealing flanges according to claim 1 is characterized in that: The establishment of the Level I model and the calculation of the compression-rebound performance of the sealing ring include: Step 101: Extract the annular cross-section of the sealing ring. The UE sealing ring still has a symmetrical surface along the axial direction. Only the lower half of the sealing ring model is retained. A straight line tangent to the lower primary and secondary sealing lips is drawn as the rigid surface of the compression sealing ring. Step 102 , establishing the sealing ring material properties, inputting the elastic modulus, Poisson's ratio, and true stress-strain curve of the sealing ring base material; Step 103: Set the contact relationship. Set a contact pair between the sealing ring and the rigid surface. Set the rigid surface as the primary contact surface, and the sealing lip and sealing ring limit surfaces as the secondary contact surfaces. Select "Limited Slip" for the slip equation and "Node-to-Pair" for the discretization method. Step 104 , meshing the sealing ring geometric model using a quadrilateral axisymmetric linear reduced integration unit; Step 105, constraining the axial displacement of the axially symmetric surface of the sealing ring; establishing two static analysis steps: the first step is used to apply axial compression displacement at the reference point of the rigid surface, and the second step is used to remove all axial compression displacement; Step 106: Generate a job and run the model calculation. After the calculation is completed, output the axial load-displacement curves of the loading and unloading history for each of the primary and secondary sealing lips. Calculate the rebound amount of each of the primary and secondary sealing lips after the compression displacement is completely removed at the current compression amount. Rebound amount = compression amount - remaining compression amount after unloading. Step 107, modify the compression amount, repeat step 106 N times; based on the calculation results, draw the rebound amount-compression amount curve of the primary and secondary sealing lips respectively.

3. The hierarchical numerical simulation method for the connection performance of metal UE sealing flanges according to claim 2 is characterized in that: In the compression-rebound performance calculation, N different compression amounts are used to load and unload the rigid surface in the Level I model, where the maximum compression amount = the maximum axial height of the sealing ring - the axial height of the limit surface, 0.25×maximum compression amount ≤ minimum compression amount ≤ 0.5×maximum compression amount, and intermediate values ​​can be evenly set between the maximum and minimum values.

4. The hierarchical numerical simulation method for the connection performance of metal UE sealing flanges according to claim 2 is characterized in that: The requirements to be met when performing grid division in step 104 include: There are enough nodes near the sealing lip to describe the arc-shaped profile of the sealing lip; There are enough unit layers along the thickness direction at the root of the sealing leg to describe the stress and strain gradient at the root of the sealing leg; The rigid surface is set as an analytical rigid body and no meshing is performed.

5. The hierarchical numerical simulation method for the connection performance of metal UE sealing flanges according to claim 2 is characterized in that: The establishment of the Level II model and the calculation of the contact performance of the sealing ring include: Step 201: Establish a two-dimensional axisymmetric geometric model according to step 101; cut out a strip area with a width equal to the coating thickness in the area where the sealing lip may come into contact with the rigid surface along the contour line of the sealing lip; Step 202 , establishing the sealing ring material properties, inputting the elastic modulus, Poisson's ratio, and true stress-strain curve of the sealing ring substrate and the coating material; Step 203: Set the contact relationship. Set a contact pair between the sealing ring and the rigid surface. Set the rigid surface as the primary contact surface, and the sealing lip and sealing ring limit surfaces as the secondary contact surfaces. Select "Limited Slip" for the slip equation and "Node-to-Pair" for the discretization method. Step 204 , meshing the sealing ring geometric model using a quadrilateral axisymmetric linear reduced integration unit; Step 205: constraining the axial displacement of the axially symmetric surface of the sealing ring; establishing two static analysis steps: the first step is used to apply a given axial compression amount at the reference point of the rigid surface, and the second step is used to remove all axial compression displacements; Step 206: Generate a job and run the model calculation. After the calculation is completed, output the contact pressure along the outer contour of the sealing lip at the end of the first analysis step, and the contact pressure along the paths on the primary and secondary sealing lips of the sealing ring when the axial compression is released by a certain amount in the second analysis step. Step 207, modify the compression amount, repeat step 206 M times, and draw contact pressure-position curves along the outer contour lines of the primary and secondary sealing lips under different compression amounts.

6. The hierarchical numerical simulation method for the connection performance of metal UE sealing flanges according to claim 5 is characterized in that: The step 207 draws contact pressure-position curves of the paths along the outer contour lines of the main and auxiliary sealing lips under different compression amounts, including: for each compression amount, drawing contact pressure-distance curves of the paths along the outer contour lines of the main and auxiliary sealing lips under different opening displacements during the compression unloading process; based on the obtained M groups of calculation results, drawing the average contact pressure-compression displacement curve of the main sealing lip, the contact width-compression displacement curve of the main sealing lip, the average contact pressure-compression displacement curve of the auxiliary sealing lip, and the contact width-compression displacement curve of the auxiliary sealing lip; for each compression amount, drawing the average contact pressure-opening displacement curve of the main sealing lip, the contact width-opening displacement curve of the main sealing lip, the average contact pressure-opening displacement curve of the auxiliary sealing lip, and the contact width-opening displacement curve of the auxiliary sealing lip.

7. The hierarchical numerical simulation method for the connection performance of metal UE sealing flanges according to claim 5 is characterized in that: The requirements for meshing in step 204 include: The unit size in the coating area is 0.001~0.01mm, and is not less than 5 layers of units along the coating thickness direction. The size of the coating unit along the thickness direction is twice that along the contour line direction; The unit size of the rest of the sealing ring is 0.05 to 0.1 mm; The coating unit and the base unit are treated as common nodes; the rigid surface adopts analytical rigid body and no meshing is performed.

8. The hierarchical numerical simulation method for the connection performance of metal UE sealing flanges according to claim 1 is characterized in that: The establishment of the Level III model and the implementation of the two-dimensional axisymmetric stress, strain and deformation response analysis of the sealing ring and flange include: Step 301: Delete the bolt holes on the flange and extract the annular cross-section of the upper and lower flanges and the sealing ring passing through the bolt axis. Step 302: Establish the material properties of the sealing ring and flange, and input the elastic modulus, Poisson's ratio, and true stress-strain curve of the sealing ring base and flange materials respectively; Step 303: Set contact relationships. Set contact pairs between the sealing ring and the flange groove, and between the upper and lower flange mating positions. In the contact pair between the sealing ring and the flange groove, the sealing ring is the secondary contact surface, the flange groove is the primary contact surface, and the sliding equation is "Limited Slip" and the discrete method is "Node Face to Face." For the contact pair between the upper and lower flange mating positions, select "Limited Slip" for the sliding equation and "Face to Face" for the discrete method. Step 304: Use quadrilateral axisymmetric linear reduced integration elements to perform finite element meshing on the sealing ring and flange geometric models. Locally refine the finite element meshes near the sealing ring and flange grooves. The mesh size requirements for the sealing ring are the same as those for the Level I model. The mesh sizes of the master and slave surfaces of the contact pair are the same. Step 305: Set the flange boundary based on the stiffness of the actual piping system in which the flange is located. Establish two static analysis steps: the first step is used to apply a preload. A gasket diameter area is cut out on the upper flange and bolt gasket compression surface, and a bolt hole area is cut out on the lower flange limit surface. A pair of equal forces are applied to simulate the preload. The second step is used to apply the working load. Step 306: Generate a job and run the model calculation. After the calculation is completed, output the compression amount and contact force at the primary and secondary sealing lips, and the stress and strain distribution of the sealing ring at the end of the first step. Output the contact force at the primary and secondary sealing lips, and the stress and strain distribution of the sealing ring at the end of the second step. Output the opening amount of the contact position between the flange and the primary and secondary sealing lips, and the stress and strain distribution of the upper and lower flanges at the end of the second step.

9. The hierarchical numerical simulation method for the connection performance of metal UE sealing flanges according to claim 1 is characterized in that: The establishment of the IV level model and the three-dimensional stress, strain and deformation response analysis of the sealing ring-flange-fastener are carried out, including: Step 401: cut out a periodically symmetrical sector containing a bolt from the seal-flange-fastener three-dimensional geometric model and perform geometric cleaning on it; Step 402: Establish the material properties of the sealing ring and flange, and input the elastic modulus, Poisson's ratio, and true stress-strain curve of the sealing ring base and flange materials, respectively. Step 403: Set contact relationships. Set contact pairs between the sealing ring and the flange sealing ring groove, between the upper flange and the lower flange mating surfaces, between the bolt and the bolt hole wall, between the bolt and the gasket, and between the gasket and the upper flange. The sealing ring and the flange ring groove are aligned, with the sealing ring as the secondary contact surface and the flange ring groove as the primary contact surface. Select "Limited Slip" for the slip equation and "Node Face to Face" for the discretization method. Select "Limited Slip" for the slip equation and "Face to Face" for the discretization method. Step 404 , using second-order tetrahedral elements combined with hexahedral linear reduced integration elements to perform finite element meshing on the sealing ring-flange-fastener three-dimensional geometric model, and locally refine the finite element meshes near the sealing ring and flange groove; Step 405: Set the flange boundary according to the stiffness of the actual pipeline system where the flange is located, and apply a periodic symmetric boundary; establish two static analysis steps: the first step is used to apply the bolt preload; the second step is used to apply the working load; Step 406: Generate a job and run the model calculation. After the calculation is completed, output the compression amount and contact force at the primary and secondary sealing lips, and the stress and strain distribution of the sealing ring at the end of the first step. Output the contact force at the primary and secondary sealing lips, and the stress and strain distribution of the sealing ring at the end of the second step. Output the opening amount of the contact position between the flange and the primary and secondary sealing lips, and the stress and strain distribution of the upper and lower flanges at the end of the second step. Output the axial load of the bolt at the end of the second step.

10. The hierarchical numerical simulation method for the connection performance of a metal UE sealing flange according to any one of claims 1 to 9, characterized in that: Said N=4-10; M=4-10.

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