A stiffness calculation method for diaphragm coupling considering service status

Abstract

The present invention specifically relates to a method for calculating the stiffness of a diaphragm coupling taking into account the service state. For an idealized diaphragm coupling model, by introducing defects and setting restarts, the model is guided to produce common plastic deformation forms in the actual service process, and the restart information of the plastic deformation model with different service degrees is derived. Then, based on the plastic deformation model, the working torque of the diaphragm coupling during service is considered, and the stiffness performance of the diaphragm coupling under different service states is analyzed to form an isotropic stiffness calculation method. At the same time, the modeling process performs a grid independence check, and a reasonable grid size is selected to ensure the effectiveness of the model grid size and the speed of solution. The stiffness calculation method of the diaphragm coupling is reasonable, the stiffness calculation model is reliable, and it can consider the service state of the coupling and the actual transmission torque value to analyze its various stiffness performances, which is of great significance for evaluating the mechanical properties of the diaphragm coupling after service.

Description

Technical Field

[0001] The invention relates to the field of coupling mechanics, and in particular to a method for calculating the stiffness of a diaphragm coupling taking into account a service state. Background Art

[0002] Diaphragm couplings are widely used in shaft transmissions such as steam turbines, compressors, marine and aviation equipment. They are flexible components that compensate for various offsets between transmission shafts through the deformation of metal diaphragm groups. They have the advantages of compact structure, reliable connection, no need for lubrication, strong ability to withstand bias pressure, and good environmental adaptability. Diaphragm couplings play an important role in mechanical power transmission, and their mechanical properties are directly related to the safety and stability of shaft transmission; in addition, the stiffness characteristics of diaphragm couplings reflect their ability to compensate for misalignment between shafts, which is a basic indicator that must be considered when evaluating coupling characteristics and selecting coupling models.

[0003] Establishing a finite element model of a diaphragm coupling through finite element simulation method and studying the isotropic stiffness performance of the diaphragm coupling are of great significance for shaft transmission and coupling selection. At present, the simulation calculation of the isotropic stiffness of the diaphragm coupling is mostly based on the idealized finite element model of the diaphragm coupling, and the solution is obtained by directly applying displacement / angular displacement and extracting the corresponding support reaction force / support reaction torque. The influence of the working torque of the coupling during service and the plastic deformation after service on its isotropic stiffness is not considered. However, the actual application condition of the diaphragm coupling is in the service environment where the coupling bears torque and transmits torque. The stiffness obtained by ignoring the working torque of the coupling cannot fully reflect the stiffness performance of the diaphragm coupling during service. At the same time, the diaphragm coupling will undergo plastic deformation to varying degrees during actual service, resulting in changes in its stiffness performance, and it does not always operate in an ideal state.

[0004] In the process of transmitting torque, the diaphragm coupling is in different stress states because the diaphragm arc segment between the active end flange bushing and the driven end flange bushing is under tension in the torsional direction and the diaphragm arc segment between the driven end flange bushing and the active end flange bushing is under compression. The diaphragm coupling usually operates within the nominal torque range, but in complex and harsh environments, the torsional torque transmitted by the coupling may suddenly change, causing the compressed diaphragm arc segment to buckle and become unstable, and plastic deformation phenomena such as delamination and opening occur between the diaphragms, resulting in changes in the stiffness of the diaphragm coupling. The stiffness calculation based on the idealized finite element model of the diaphragm coupling does not consider the influence of the service state of the coupling on its stiffness performance. The stiffness data obtained by simulation is directly applied to the research and design of the shaft system, which not only leads to certain errors in the research results, but also poses a great hidden danger to the safety of the shaft system transmission. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for calculating the stiffness of a diaphragm coupling taking into account the service status. The purpose is to consider the influence of the plastic deformation that occurs after the diaphragm coupling is put into service and the service environment that bears torque on its stiffness performance, so as to form an effective stiffness calculation method, solve the isotropic stiffness of the diaphragm coupling, and avoid the problem that the stiffness value solved by the idealized diaphragm coupling model is too large and the solution time is too long.

[0006] A method for calculating the stiffness of a diaphragm coupling taking into account a service state comprises the following steps.

[0007] S1. Establish a geometric model of the diaphragm coupling in the finite element analysis software, make pre-processing settings, and perform a grid independence check to obtain an initial finite element model of the diaphragm coupling;

[0008] S2, copying the initial finite element model of the diaphragm coupling, setting the load boundary conditions and displacement boundary conditions for generating the initial defects, setting the displacement output keyword, and outputting the node displacement information of the initial defects of the diaphragm coupling;

[0009] S3, copying the initial finite element model of the diaphragm coupling, setting the defect introduction keyword, integrating the initial defect into the initial finite element model of the diaphragm coupling, obtaining the torsional defect model of the diaphragm coupling, setting the load boundary conditions and displacement boundary conditions of the torsional analysis, solving the ultimate bearing moment in the torsional direction and the torsional angular displacement corresponding to the ultimate bearing moment;

[0010] S4, copying the torsional defect model of the diaphragm coupling, resetting the displacement boundary conditions of the torsional analysis based on the torsional angular displacement solved in step S3, and setting a restart output request, so that the restart information of the plastic deformation model with different service degrees is output after the diaphragm coupling yields;

[0011] S5. Copy the initial finite element model of the diaphragm coupling, set the restart attribute, import the restart information of the plastic deformation model of a certain service level, determine the stiffness analysis task, consider the service state and transmission torque value of the diaphragm coupling, and establish the isotropic stiffness analysis model of the diaphragm coupling after plastic deformation;

[0012] S6. Complete the modeling, check the stiffness analysis model, extract the coupling point data from the calculation results of the stiffness analysis model, draw the load-displacement curve, and solve the isotropic stiffness values ​​of the diaphragm coupling under different service levels.

[0013] Step S1 specifically includes the following process:

[0014] S1.1. In the finite element analysis software, establish the geometric model of the diaphragm, gasket, and flange bushing, set the elastic modulus, Poisson's ratio, and plastic properties, and assemble and establish the geometric model of the diaphragm coupling to determine the positions of the active end flange bushing and the driven end flange bushing;

[0015] S1.2. Perform regional cutting of the diaphragm, flange bushing, and gasket, and set the mesh density through the global seed. Set the mesh type of the diaphragm to C3D8I, the mesh type of the gasket and flange bushing to C3D8R, use the hexahedral meshing method, and perform meshing quality check;

[0016] S1.3, set the analysis step, field output, and history output;

[0017] S1.4. Create coupling points RP1 and RP2, and set the interaction and constraint relationships among the diaphragm, flange bushing, and gasket;

[0018] S1.5. Set the load boundary conditions and displacement boundary conditions for mesh independence check;

[0019] S1.6, set the diaphragm grid size variable group, only change the diaphragm grid size, establish the diaphragm coupling finite element model group, and perform grid independence check;

[0020] S1.7. Select a reasonable diaphragm mesh size to obtain the initial finite element model of the diaphragm coupling.

[0021] Furthermore, the regional cutting of the diaphragm in step S1 forms a load-bearing area for distributed loads in the waist section of the diaphragm, and increases the number of grid seed lines to coordinate the grid distribution of the diaphragm; the regional cutting of the flange bushing forms a bolt preload application section in the middle position of the flange bushing; the regional cutting of the gasket matches the grid seed lines of the flange bushing and coordinates the grid distribution.

[0022] Furthermore, the interaction relationship in step S1 includes the separable friction contact between the contact planes of the diaphragm and the diaphragm, the non-separable friction contact between the contact planes of the diaphragm and the flange bushing, the non-separable friction contact between the contact cylinder of the diaphragm and the flange bushing, and the non-separable friction contact between the contact planes of the diaphragm and the gasket; the constraint relationship includes the binding constraint between the flange bushing and the gasket contact cylinder, the coupling constraint between the coupling point RP1 and the inner cylindrical node of the active end flange bushing, and the coupling constraint between the coupling point RP2 and the inner cylindrical node of the fixed end flange bushing. The separable friction contact between the diaphragm and the diaphragm surface allows the contact surface to separate during the analysis process, which is an important setting for the diaphragm coupling model to produce common plastic deformation forms during the analysis process.

[0023] Furthermore, the load boundary condition for the grid independence check in step S1 is the bolt preload applied to the flange bushing section; the displacement boundary condition for the grid independence check includes setting the torsional angular displacement of the coupling point RP1 and fixing other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2.

[0024] Furthermore, the grid independence check described in step S1 is performed, and the diaphragm coupling finite element model group established based on the diaphragm grid size variable group is analyzed to make the torsional angular displacement of the diaphragm coupling finite element model group at the coupling point RP1 consistent, and the convergence of the support reaction torque at the coupling point RP2 is checked. If the support reaction torque change of the diaphragm coupling finite element model of adjacent diaphragm grid sizes is less than 1%, it is considered to be converged, and the diaphragm grid sizes that meet the convergence of the support reaction torque are considered independent.

[0025] Furthermore, the reasonable diaphragm grid size satisfies the diaphragm grid size independence, and the maximum diaphragm grid size in the diaphragm grid size group is taken to obtain the initial finite element model of the diaphragm coupling. The selection of a reasonable grid size not only ensures the effectiveness of the model in terms of grid size, but also improves the speed of solution.

[0026] Furthermore, the load boundary conditions for generating the initial defect in step S2 include the bolt preload applied to the flange bushing section and the distributed load applied to the diaphragm waist section bearing area from the active end flange bushing to the driven end flange bushing in the torsion direction; the displacement boundary conditions for generating the initial defect include all degrees of freedom of the fixed coupling point RP1 and the coupling point RP2. The distributed load applied to the diaphragm waist section bearing area causes the common delamination phenomenon between the diaphragms during actual service, and the node displacement information of the displacement result is output as the initial defect.

[0027] Furthermore, the displacement output keyword is set in step S2 to output the node displacement information of the initial defect of the diaphragm coupling. The displacement output keyword is

[0028] *NODE FILE

[0029] U .

[0030] Furthermore, the defect introduction keyword in step S3 is used to import the node displacement information of the initial defect of the diaphragm coupling output in step S2 to establish a torsional defect model of the diaphragm coupling. The keywords are as follows:

[0031] *IMPERFECTION,FILE=filename,STEP=a,INC=b

[0032] 1,c

[0033] Among them, step S3 outputs the node displacement information of the initial defect of the diaphragm coupling by executing a job, filename is the name of the job, and the job is executed in the order of analysis steps, each analysis step is executed in the order of incremental steps, a is the number of analysis steps introduced by the defect, b is the number of incremental steps introduced by the defect, and c is the proportional value of the defect introduction. Under the guidance of the node displacement information of the initial defect, stratification occurs between the diaphragms during the torsion analysis process, forming a common plastic deformation form of the diaphragm coupling during service.

[0034] Furthermore, the load boundary condition of the torsion analysis in step S3 is the bolt preload applied to the flange bushing section; the displacement boundary condition of the torsion analysis includes setting the torsion angular displacement θ of the coupling point RP1 and fixing other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2; the torsion angular displacement θ of the coupling point RP1 should make the diaphragm coupling reach the ultimate bearing torque in the torsion direction, yield and produce plastic deformation.

[0035] Furthermore, the resetting of the displacement boundary conditions for the torsion analysis in step S4 includes setting the torsion angular displacement β of the coupling point RP1 and fixing other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2; and β=α+n*Δ, wherein α is the torsion angular displacement solved in step S3, n is the number of plastic deformation models of different service degrees of the diaphragm coupling required, and Δ is the differentiation amount of the degree of plastic deformation, which is 0.1°~0.3°.

[0036] Furthermore, the restart output request described in step S4 outputs the node information of displacement, stress and strain of the torsional defect model of the diaphragm coupling under different torsional angular displacements, which serves as the restart information of the plastic deformation model of the diaphragm coupling at different service levels, so as to consider the service status of the coupling for subsequent stiffness calculation.

[0037] Step S5 specifically includes the following process:

[0038] S5.1, copy the initial finite element model of the diaphragm coupling in step S1 as the basic setting model;

[0039] S5.2. Set the restart properties of the model and import the restart information of the plastic deformation model of a certain service level;

[0040] S5.3, determine the stiffness analysis task;

[0041] S5.4, set the unloading analysis step and stiffness analysis step;

[0042] S5.5. Set the load boundary conditions and displacement boundary conditions for stiffness analysis, and establish the stiffness analysis model of the diaphragm coupling after service.

[0043] Furthermore, the model restart attribute described in step S5 is used to import the restart information output by step S4, determine the incremental step by the torsional angular displacement that forms the plastic deformation model of a certain service level, use the restart information of the incremental step as the node result information of the plastic deformation model, and set the starting state of the stiffness analysis model.

[0044] Furthermore, there are four stiffness analysis tasks in step S5, which are based on a plastic deformation model of a certain service level, and consider the influence of the service state of the diaphragm coupling on its stiffness performance, and perform torsional stiffness analysis, axial stiffness analysis, angular stiffness analysis, and radial stiffness analysis respectively.

[0045] Furthermore, the unloading analysis step described in step S5 is the first analysis step for restarting the stiffness analysis model, which releases the torsional degree of freedom of the coupling point RP1 and fixes other degrees of freedom of the coupling point RP1, realizes automatic unloading of the torsional support reaction torque, and retains plastic deformation; the stiffness analysis step is used to set the load boundary conditions and displacement boundary conditions of the stiffness analysis, and solves the isotropic stiffness of the diaphragm coupling after service.

[0046] Furthermore, the load boundary conditions for torsional stiffness analysis include the bolt preload applied to the flange bushing section, the torsional moment amplitude M applied to the coupling point RP1, and the max ; The torsional moment amplitude M max =1.1M1, M1 is the nominal torque value of the diaphragm coupling; the displacement boundary condition of the torsional stiffness analysis includes releasing the torsional degree of freedom of the coupling point RP1 and fixing the other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2.

[0047] Furthermore, the load boundary conditions of the axial stiffness analysis, angular stiffness analysis, and radial stiffness analysis are the same, including the bolt preload applied to the flange bushing section and the torsional moment amplitude M1 applied to the coupling point RP1; the torsional moment amplitude M1 is the nominal torque value of the diaphragm coupling, which is used as the working torque actually borne by the coupling during the stiffness analysis; the displacement boundary conditions of the axial stiffness analysis, angular stiffness analysis, and radial stiffness analysis include setting only one degree of freedom displacement value of the coupling point RP1 and fixing the other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2; for the axial stiffness analysis, the axial degree of freedom displacement value x of the coupling point RP1 is set; for the angular stiffness analysis, the angular degree of freedom displacement value δ of the coupling point RP1 is set; for the radial stiffness analysis, the radial degree of freedom displacement value y of the coupling point RP1 is set.

[0048] Furthermore, the coupling point data of the torsional stiffness analysis in step S6 include the displacement data of the coupling point RP1 and the torque data of the coupling point RP2 within the torque loading range of 0.9M1 to 1.1M1, so as to draw the load-displacement curve and solve the tangent stiffness to obtain the torsional stiffness of the diaphragm coupling when it is subjected to the working torque after considering the service state.

[0049] Furthermore, step S6 analyzes the coupling point data of axial stiffness analysis, angular stiffness analysis, and radial stiffness analysis, including the displacement / angular displacement data of coupling point RP1 and the support reaction force / support reaction torque data of coupling point RP2, so as to draw the load-displacement curve and solve the tangent stiffness to obtain the axial stiffness, angular stiffness, and radial stiffness of the diaphragm coupling when it is subjected to the working torque after considering the service state.

[0050] The present invention provides a method for calculating the stiffness of a diaphragm coupling taking into account the service state, which has the following beneficial effects:

[0051] 1) Compared with the existing technology, the present invention provides a method for calculating the stiffness of a diaphragm coupling taking into account the service state. First, an initial finite element model of the diaphragm coupling is established. According to the common plastic deformation forms of the diaphragm coupling during its service, a distributed load that produces initial defects is set for analysis, and the node displacement information of the initial defects is output; through the defect introduction method, the diaphragm coupling model is guided to undergo common plastic deformation during the torsion process, thereby obtaining a plastic deformation model, and considering the service state of the coupling, its various stiffnesses are analyzed. The stiffness calculation method is reasonable, the stiffness calculation model is reliable, and it can consider the different degrees of service state of the coupling to analyze its various stiffnesses, solving the problem of the idealized coupling model stiffness calculation result being too large.

[0052] 2) The mesh independence of the finite element model of the diaphragm coupling was checked, and a reasonable mesh size was selected to avoid the impact of too large a mesh size on the solution accuracy, ensuring the effectiveness of the model in terms of mesh size, and avoiding the problem of too many meshes due to too small a mesh size, resulting in too long a solution time.

[0053] 3) Apply a torsional angular displacement of β to the diaphragm coupling through the coupling point RP1, and use the restart setting to output the node result information of the plastic deformation model under the corresponding torsional angular displacement. Only one torsional analysis is required to obtain n plastic deformation models of different degrees, which greatly reduces the calculation time for generating plastic deformation models of different degrees. In addition, for the plastic deformation models under different torsional angular displacements, the torsional support reaction torque can be automatically unloaded by releasing the torsional degree of freedom, while retaining the plastic deformation of the coupling without separate processing, which improves the versatility of the model.

[0054] 4) When solving the stiffness, the nominal torque value M1 of the diaphragm coupling is applied at the coupling point RP1 to simulate the working torque of the coupling, so as to solve the axial stiffness, angular stiffness and radial stiffness of the coupling after service, which fully reflects the stiffness performance of the diaphragm coupling during operation; at the same time, for the solution of torsional stiffness, the coupling point data within the torque loading range of 0.9M1 to 1.1M1 are extracted for analysis, which can also reflect the torsional stiffness value near the working torque of the coupling, avoiding ignoring the influence of the service environment of the coupling bearing torque and transmitting torque on the solutions of various stiffness. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a flow chart of a method for calculating the stiffness of a diaphragm coupling taking into account the service status provided in this embodiment.

[0056] Figure 2 It is a schematic diagram of the step S1 process provided in this embodiment.

[0057] Figure 3 It is a schematic diagram of the composition of the diaphragm coupling provided in this embodiment.

[0058] Figure 4 It is a schematic diagram of the regional cutting of the diaphragm, flange bushing, and gasket provided in this embodiment.

[0059] Figure 5 It is a schematic diagram of the interaction and constraint relationship among the diaphragm, flange bushing, and gasket provided in this embodiment.

[0060] Figure 6 It is a schematic diagram of the coupling constraint relationship between the coupling point RP1 and the coupling point RP2 provided in this embodiment.

[0061] Figure 7 It is a schematic diagram of load boundary conditions and displacement boundary conditions for mesh independence check and torsion analysis provided in this embodiment.

[0062] Figure 8 Schematic diagram of the mesh division of the diaphragm coupling provided in this embodiment.

[0063] Fig. 9 This is a schematic diagram of load boundary conditions and displacement boundary conditions for generating initial defects provided in this embodiment.

[0064] Fig.10 It is the displacement cloud map calculated in step S2 provided in this embodiment.

[0065] Fig.11 It is a schematic diagram of the relationship between the bearing moment and the torsional angular displacement in the torsional direction provided by this embodiment.

[0066] Fig.12It is the displacement cloud map calculated in step S3 provided in this embodiment.

[0067] Fig.13 Schematic diagram of two plastic deformation models with different service levels provided in this embodiment.

[0068] Fig.14 It is a schematic diagram of the process of step S5 provided in this embodiment.

[0069] Fig.15 It is a schematic diagram of load boundary conditions and displacement boundary conditions for four types of stiffness analysis provided in this embodiment. DETAILED DESCRIPTION

[0070] In order to more clearly describe the purpose, technical solutions and advantages of the specific embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0071] This embodiment proposes a method for calculating the stiffness of a diaphragm coupling taking into account the service state. The stiffness calculation of the diaphragm coupling is performed on the Abaqus finite element simulation software. Figure 3 and Figure 4 , which is a schematic diagram of the diaphragm coupling, the research object of the stiffness calculation method, including a diaphragm 1, a flange bushing 2, and a gasket 3. A plurality of diaphragms 1 are stacked to form a diaphragm group, and a through hole is opened on the surface of the diaphragm. The diaphragm group is fastened by the interference fit of the flange bushing 2 and the gasket 3 at the diaphragm through hole. The assembly direction of the flange bushing 2 and the gasket 3 changes alternately along the circumferential direction of the diaphragm 1; the contact between the diaphragm 1 and the surface of the diaphragm 1, the diaphragm 1 and the surface of the flange bushing 2, and the diaphragm 1 and the surface of the gasket 3 are all friction contacts.

[0072] This embodiment proposes a method for calculating the stiffness of a diaphragm coupling taking into account the service state, see Figure 1 , the method comprises the following steps:

[0073] S1. Establish the geometric model of the diaphragm coupling in the finite element analysis software, make pre-processing settings, and perform mesh independence check to obtain the initial finite element model of the diaphragm coupling. Figure 2 , step S1 specifically includes steps S1.1 to S1.7:

[0074] S1.1. In the finite element analysis software, establish the geometric model of the diaphragm, gasket, and flange bushing, set the elastic modulus, Poisson's ratio, and plastic properties, and assemble and establish the geometric model of the diaphragm coupling to determine the positions of the active end flange bushing and the driven end flange bushing. Figure 3 , is a schematic diagram of the composition of the diaphragm coupling of this embodiment.

[0075] S1.2. Perform regional cutting of the diaphragm, flange bushing, and gasket, and set the mesh density through the global seed. Set the mesh type of the diaphragm to C3D8I, the mesh type of the gasket and flange bushing to C3D8R, use the hexahedral meshing method, and perform meshing quality check. Figure 4 , is a schematic diagram of the regional cutting of the diaphragm, flange bushing, and gasket of this embodiment. By performing regional cutting on the diaphragm, a load-bearing area for distributed load is formed in the waist section of the diaphragm, and the number of grid seed lines is increased to coordinate the grid distribution of the diaphragm; by performing regional cutting on the flange bushing, a bolt preload application section is formed in the middle position of the flange bushing; by performing regional cutting on the gasket, the grid seed lines of the flange bushing are matched and the grid distribution is coordinated.

[0076] S1.3, set the analysis step, field output, and history output;

[0077] S1.4. Create coupling points RP1 and RP2, and set the interaction and constraint relationships among the diaphragm, flange bushing, and gasket. Figure 5 , Figure 6 The interaction relationships include the separable friction contact between the contact planes of the diaphragms and the diaphragms, the non-separable friction contact between the contact planes of the diaphragms and the flange bushings, the non-separable friction contact between the contact cylinders of the diaphragms and the flange bushings, and the non-separable friction contact between the contact planes of the diaphragms and the gaskets; the constraint relationships include the binding constraint between the contact cylinders of the flange bushings and the gaskets, the coupling constraint between the coupling point RP1 and the inner cylindrical node of the active end flange bushing, and the coupling constraint between the coupling point RP2 and the inner cylindrical node of the fixed end flange bushing.

[0078] Specifically, the separable friction contact allows the contact surfaces to separate during the analysis process. When the contact pressure perpendicular to the unit action surface decreases to zero, the two contact surfaces separate. When the gap between the separated surfaces decreases to zero, the contact is reestablished. The separable friction contact between the diaphragm and the diaphragm surface is an important setting that enables the coupling model to produce common plastic deformation forms during the analysis process.

[0079] S1.5. Set the load boundary conditions and displacement boundary conditions for mesh independence check. Figure 7The load boundary condition for the mesh independence check is the bolt preload applied to the flange bushing section; the displacement boundary condition for the mesh independence check includes setting the torsional angular displacement of the coupling point RP1 and fixing the other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2.

[0080] S1.6. Set the diaphragm grid size variable group, only change the diaphragm grid size, establish the diaphragm coupling finite element model group, and perform grid independence check. The diaphragm coupling finite element model group established based on the diaphragm grid size variable group is analyzed to make the torsional angular displacement of the diaphragm coupling finite element model group at the coupling point RP1 consistent, check the convergence of the support reaction torque at the coupling point RP2, and the support reaction torque of the diaphragm coupling finite element model of adjacent diaphragm grid sizes is considered to be converged if the change is less than 1%, and the diaphragm grid size that meets the convergence of the support reaction torque is considered to be independent.

[0081] S1.7. Select a reasonable diaphragm grid size to obtain the initial finite element model of the diaphragm coupling. A reasonable diaphragm grid size, on the one hand, needs to satisfy the diaphragm grid size independence, and on the other hand, it should be the largest size in the diaphragm grid size group, which can avoid errors in the analysis results due to too large a grid size, and avoid too small a grid size resulting in too many grids and a long solution time, thereby improving the solution rate. Figure 8 , which is a schematic diagram of the mesh division of the diaphragm coupling of this embodiment. By cutting the area in step S1.2, setting the mesh seed line, and coordinating the mesh distribution, a standard and normative mesh distribution is obtained.

[0082] S2: Copy the initial finite element model of the diaphragm coupling, set the load boundary conditions and displacement boundary conditions that generate the initial defects, set the displacement output keyword, and then output the node displacement information of the initial defects of the diaphragm coupling.

[0083] For details, see Fig. 9 The load boundary conditions that generate the initial defect include the bolt preload applied to the flange bushing section and the distributed load applied to the diaphragm waist section bearing area from the active end flange bushing to the driven end flange bushing in the torsion direction; the displacement boundary conditions that generate the initial defect include all degrees of freedom of the fixed coupling point RP1 and the coupling point RP2. The distributed load applied to the diaphragm waist section bearing area causes the common delamination phenomenon of the diaphragm coupling in the actual service process to occur between the diaphragms, and the node displacement information of the result is output as the initial defect.

[0084] Specifically, by setting the displacement output keyword, the node displacement information of the initial defect of the diaphragm coupling is output. Fig.10, is the displacement cloud diagram obtained by finite element software calculation after setting the displacement output keyword in step S2. The distributed load applied to the bearing area of ​​the diaphragm waist section makes the diaphragm coupling appear in the ideal state of plastic deformation shape, and the node displacement information of this shape is output as the initial defect. The displacement output keywords are as follows

[0085] *NODE FILE

[0086] U .

[0087] S3: Copy the initial finite element model of the diaphragm coupling, set the defect introduction keyword, integrate the initial defect into the initial finite element model of the diaphragm coupling, obtain the torsional defect model of the diaphragm coupling, set the load boundary conditions and displacement boundary conditions of the torsional analysis, and solve the ultimate bearing moment in the torsional direction and the torsional angular displacement corresponding to the ultimate bearing moment.

[0088] Specifically, the defect introduction keyword is used to import the node displacement information of the initial defect of the diaphragm coupling output in step S2, establish the torsional defect model of the diaphragm coupling, guide the stratification between the diaphragms, and form a common plastic deformation form. The keyword is as follows

[0089] *IMPERFECTION,FILE=filename,STEP=a,INC=b

[0090] 1,c

[0091] Among them, step S2 outputs the node displacement information of the initial defect of the diaphragm coupling by executing the job, filename is the name of the job, and the job is executed in the order of analysis steps, each analysis step is executed in the order of incremental steps, a is the number of analysis steps introduced by the defect, b is the number of incremental steps introduced by the defect, and c is the proportional value of the defect introduction.

[0092] Specifically, the load boundary condition of the torsion analysis is the bolt preload applied to the flange bushing section; the displacement boundary condition of the torsion analysis includes setting the torsion angular displacement θ of the coupling point RP1 and fixing the other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2; the torsion angular displacement θ of the coupling point RP1 should make the diaphragm coupling reach the ultimate bearing moment in the torsion direction, yield and produce plastic deformation. Figure 7 , which is similar to the load boundary condition and displacement boundary condition of step S1, except that the torsional angular displacement θ of the coupling point RP1 in the displacement boundary condition of torsion analysis should be large enough to enable the diaphragm coupling to reach the ultimate bearing moment in the torsional direction, yield and produce plastic deformation.

[0093] Specifically, step S3 calculates the ultimate bearing moment in the torsion direction and the torsion angular displacement corresponding to the ultimate bearing moment. Fig.11 , is a schematic diagram of the relationship between the bearing torque and the torsional angular displacement in the torsional direction of this embodiment. When the torsional angular displacement is α, the diaphragm coupling reaches the ultimate bearing torque M in the torsional direction. Then, as the torsional angular displacement increases, the bearing torque of the diaphragm coupling decreases. Fig.12 , which is the displacement cloud map calculated based on the torsional defect model of the diaphragm coupling. Under the guidance of the node displacement information of the initial defect, the diaphragm coupling model with the initial defect undergoes diaphragm delamination, forming a common plastic deformation form of the diaphragm coupling during its service.

[0094] S4. Copy the torsional defect model of the diaphragm coupling, reset the displacement boundary conditions of the torsional analysis based on the torsional angular displacement solved in step S3, and set a restart output request so that the restart information of the plastic deformation model with different service degrees is output after the diaphragm coupling yields.

[0095] Specifically, based on the torsional angular displacement solved in step S3.4, the displacement boundary conditions of the torsional analysis are reset, including setting the torsional angular displacement β of the coupling point RP1 and fixing other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2; and β=α+n*Δ, wherein α is the torsional angular displacement solved in step S3, n is the number of plastic deformation models of different service degrees of the diaphragm coupling required, and Δ is the differentiation amount of the degree of plastic deformation, which is taken as 0.1°~0.3°.

[0096] Specifically, the restart output request of step S4 outputs the node information of displacement, stress, and strain of the torsional defect model of the diaphragm coupling under different torsional angular displacements as the restart information of the plastic deformation model of the diaphragm coupling at different service levels. The restart output request retains the node information of the plastic deformation such as displacement, stress, and strain of the torsional defect model of the diaphragm coupling under different torsional angular displacements, so as to consider the service status of the diaphragm coupling for subsequent stiffness calculation. Fig.13 , which is a schematic diagram of the plastic deformation model with two different service levels.

[0097] S5: Copy the initial finite element model of the diaphragm coupling, set the restart attributes, import the restart information of the plastic deformation model of a certain service level, determine the stiffness analysis task, consider the service status and transmission torque value of the diaphragm coupling, and establish the isotropic stiffness analysis model of the diaphragm coupling after plastic deformation. Fig.14 , step S5 specifically includes steps S5.1 to S5.5:

[0098] S5.1, copy the initial finite element model of the diaphragm coupling in step S1 as the basic setting model;

[0099] S5.2. Set the restart properties of the model and import the restart information of the plastic deformation model of a certain service level. Determine the incremental step by the torsion angular displacement that forms the plastic deformation model of a certain service level, use the restart information of the incremental step as the node result information of the plastic deformation model, and set the initial state of the stiffness analysis model.

[0100] S5.3. Determine the stiffness analysis tasks. There are 4 stiffness analysis tasks for the diaphragm coupling. Based on the plastic deformation model of a certain service level, the influence of the service state of the diaphragm coupling on its stiffness performance is considered, and torsional stiffness analysis, axial stiffness analysis, angular stiffness analysis, and radial stiffness analysis are performed respectively.

[0101] S5.4. Set the unloading analysis step and the stiffness analysis step; the unloading analysis step is the first analysis step for restarting the stiffness analysis model, which releases the torsional degree of freedom of the coupling point RP1 and fixes the other degrees of freedom of the coupling point RP1, realizes the automatic unloading of the torsional support reaction torque, and retains the plastic deformation; the stiffness analysis step is used to set the load boundary conditions and displacement boundary conditions of the stiffness analysis, and solves the various stiffnesses of the diaphragm coupling after service.

[0102] S5.5. Set the load boundary conditions and displacement boundary conditions for stiffness analysis, and establish the stiffness analysis model of the diaphragm coupling after service. Fig.15 , which is a schematic diagram of load boundary conditions and displacement boundary conditions for four types of stiffness analysis in this embodiment.

[0103] Specifically, the load boundary conditions for torsional stiffness analysis include the bolt preload applied to the flange bushing section, the torsional moment amplitude M applied to the coupling point RP1, and the max Among them, the torsional moment amplitude M max =1.1M1, M1 is the nominal torque value of the diaphragm coupling. The displacement boundary conditions of the torsional stiffness analysis include releasing the torsional degree of freedom of the coupling point RP1 and fixing the other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2. By analyzing the calculation data within the torque loading range of 0.9M1 to 1.1M1, the torsional stiffness value of the coupling near the working torque is solved.

[0104] Specifically, the load boundary conditions for axial stiffness analysis, angular stiffness analysis, and radial stiffness analysis are the same, including the bolt preload applied to the flange bushing section and the torsional moment amplitude M1 applied to the coupling point RP1; the torsional moment amplitude M1 is the nominal torque value of the diaphragm coupling, which is the actual working torque borne by the coupling during stiffness analysis. The displacement boundary conditions for axial stiffness analysis, angular stiffness analysis, and radial stiffness analysis include setting only one degree of freedom displacement value of the coupling point RP1 and fixing the other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2; for axial stiffness analysis, set the axial degree of freedom displacement value x of the coupling point RP1; for angular stiffness analysis, set the angular degree of freedom displacement value δ of the coupling point RP1; for radial stiffness analysis, set the radial degree of freedom displacement value y of the coupling point RP1. By applying the nominal torque value M1 at the coupling point RP1, the working torque of the diaphragm coupling is simulated, so as to solve the axial stiffness, angular stiffness and radial stiffness of the diaphragm coupling after service, which fully reflects the stiffness performance of the diaphragm coupling when it is working.

[0105] S6. Complete the modeling, check the stiffness analysis model, extract the coupling point data from the calculation results of the stiffness analysis model, draw the load-displacement curve, and solve the isotropic stiffness values ​​of the diaphragm coupling under different service levels.

[0106] Specifically, the coupling point data for torsional stiffness analysis include the displacement data of coupling point RP1 and the torque data of coupling point RP2 within the torque loading range of 0.9M1 to 1.1M1, and the load-displacement curve is drawn to solve the tangent stiffness, and the torsional stiffness of the diaphragm coupling when it is subjected to working torque after considering the service state is obtained. The coupling point data for axial stiffness analysis, angular stiffness analysis, and radial stiffness analysis include the displacement / angular displacement data of coupling point RP1 and the support reaction force / support reaction torque data of coupling point RP2, and the load-displacement curve is drawn to solve the tangent stiffness, and the axial stiffness, angular stiffness, and radial stiffness of the diaphragm coupling when it is subjected to working torque after considering the service state are obtained.

[0107] The stiffness calculation method for a diaphragm coupling taking into account the service status proposed in this embodiment is reasonable, the stiffness calculation model is reliable, and it can form plastic deformation models of different degrees. The service status of the coupling and the actual transmitted torque value are considered to solve its various stiffnesses, which solves the problem of the idealized coupling model stiffness calculation results being too large, improves the effectiveness of the simulation results, and is of great significance for evaluating the mechanical properties of the coupling after service.

[0108] It is obvious to those skilled in the art that the present invention is not limited to the details of the above embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description.

[0109] The embodiments described above are only some embodiments of the present invention, not all embodiments, and the protection scope of the present invention is not limited thereto. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for calculating the stiffness of a diaphragm coupling considering the service state, characterized in that: The following steps are involved: S1. Establish a geometric model of the diaphragm coupling in the finite element analysis software, make pre-processing settings, and perform a grid independence check to obtain an initial finite element model of the diaphragm coupling; S2, copying the initial finite element model of the diaphragm coupling, setting the load boundary conditions and displacement boundary conditions for generating the initial defects, setting the displacement output keyword, and outputting the node displacement information of the initial defects of the diaphragm coupling; S3, copying the initial finite element model of the diaphragm coupling, setting the defect introduction keyword, integrating the initial defect into the initial finite element model of the diaphragm coupling, obtaining the torsional defect model of the diaphragm coupling, setting the load boundary conditions and displacement boundary conditions of the torsional analysis, solving the ultimate bearing moment in the torsional direction and the torsional angular displacement corresponding to the ultimate bearing moment; S4, copying the torsional defect model of the diaphragm coupling, resetting the displacement boundary conditions of the torsional analysis based on the torsional angular displacement solved in step S3, and setting a restart output request, so that the restart information of the plastic deformation model with different service degrees is output after the diaphragm coupling yields; S5. Copy the initial finite element model of the diaphragm coupling, set the restart attribute, import the restart information of the plastic deformation model of a certain service level, determine the stiffness analysis task, consider the service state and transmission torque value of the diaphragm coupling, and establish the isotropic stiffness analysis model of the diaphragm coupling after plastic deformation; S6. Complete the modeling, check the stiffness analysis model, extract the coupling point data from the calculation results of the stiffness analysis model, draw the load-displacement curve, and solve the isotropic stiffness values ​​of the diaphragm coupling under different service levels.

2. The method for calculating the stiffness of a diaphragm coupling considering the service state according to claim 1 is characterized in that: Step S1 specifically includes: S1.

1. In the finite element analysis software, establish the geometric model of the diaphragm, gasket, and flange bushing, set the elastic modulus, Poisson's ratio, and plastic properties, and assemble and establish the geometric model of the diaphragm coupling to determine the positions of the active end flange bushing and the driven end flange bushing; S1.

2. Perform regional cutting of the diaphragm, flange bushing, and gasket, and set the mesh density through the global seed. Set the mesh type of the diaphragm to C3D8I, the mesh type of the gasket and flange bushing to C3D8R, use the hexahedral meshing method, and perform meshing quality check; S1.3, set the analysis step, field output, and history output; S1.

4. Create coupling points RP1 and RP2, and set the interaction and constraint relationships among the diaphragm, flange bushing, and gasket; S1.

5. Set the load boundary conditions and displacement boundary conditions for mesh independence check; S1.6, set the diaphragm grid size variable group, only change the diaphragm grid size, establish the diaphragm coupling finite element model group, and perform grid independence check; S1.

7. Select a reasonable diaphragm mesh size to obtain the initial finite element model of the diaphragm coupling.

3. The method for calculating the stiffness of a diaphragm coupling considering the service state according to claim 2 is characterized in that: The regional cutting of the diaphragm forms a load-bearing area for distributed loads in the waist section of the diaphragm, and increases the number of grid seed lines to coordinate the grid distribution of the diaphragm; the regional cutting of the flange bushing forms a bolt preload application section in the middle position of the flange bushing; the regional cutting of the gasket matches the grid seed lines of the flange bushing and coordinates the grid distribution.

4. The method for calculating stiffness of a diaphragm coupling considering service status according to claim 2, characterized in that: The interaction relationship includes the separable friction contact between the diaphragm and the diaphragm contact plane, the non-separable friction contact between the diaphragm and the flange bushing contact plane, the non-separable friction contact between the diaphragm and the flange bushing contact cylinder, and the non-separable friction contact between the diaphragm and the gasket contact plane; the constraint relationship includes the binding constraint between the flange bushing and the gasket contact cylinder, the coupling constraint between the coupling point RP1 and the inner cylindrical node of the active end flange bushing, and the coupling constraint between the coupling point RP2 and the inner cylindrical node of the fixed end flange bushing.

5. The method for calculating the stiffness of a diaphragm coupling considering the service state according to claim 2, characterized in that: The load boundary condition for the mesh independence check is the bolt preload applied to the flange bushing section; the displacement boundary condition for the mesh independence check includes setting the torsional angular displacement of the coupling point RP1 and fixing other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2.

6. The method for calculating the stiffness of a diaphragm coupling considering the service state according to claim 2, characterized in that: The grid independence check is performed by analyzing the diaphragm coupling finite element model group established based on the diaphragm grid size variable group, so that the torsional angular displacement of the diaphragm coupling finite element model group at the coupling point RP1 is consistent, and the convergence of the support reaction torque at the coupling point RP2 is checked. If the support reaction torque change of the diaphragm coupling finite element model of adjacent diaphragm grid sizes is less than 1%, it is considered to be converged, and the diaphragm grid size that meets the convergence of the support reaction torque is considered to be independent.

7. The method for calculating the stiffness of a diaphragm coupling considering the service state according to claim 6, characterized in that: The reasonable diaphragm grid size satisfies the diaphragm grid size independence, and the maximum diaphragm grid size in the diaphragm grid size group is taken to obtain the initial finite element model of the diaphragm coupling.

8. The method for calculating the stiffness of a diaphragm coupling considering the service state according to claim 2, characterized in that: In step S2, the load boundary conditions that produce the initial defect include the bolt preload applied to the flange bushing section and the distributed load applied to the diaphragm waist section bearing area from the active end flange bushing to the driven end flange bushing in the torsional direction; the displacement boundary conditions that produce the initial defect include all degrees of freedom of the fixed coupling point RP1 and the coupling point RP2.

9. The method for calculating the stiffness of a diaphragm coupling considering the service state according to claim 1, characterized in that: Set the displacement output keyword to output the node displacement information of the initial defect of the diaphragm coupling. The displacement output keyword is as follows *NODE FILE U 。 10. The method for calculating the stiffness of a diaphragm coupling considering the service state according to claim 1, characterized in that: In step S3, the defect introduction keyword is used to import the node displacement information of the initial defect of the diaphragm coupling output in step S2 to establish the diaphragm coupling torsional defect model. The keywords are as follows: *IMPERFECTION,FILE=filename,STEP=a,INC=b 1,c Among them, step S2 outputs the node displacement information of the initial defect of the diaphragm coupling by executing the job, filename is the name of the job, and the job is executed in the order of analysis steps, each analysis step is executed in the order of incremental steps, a is the number of analysis steps introduced by the defect, b is the number of incremental steps introduced by the defect, and c is the proportional value of the defect introduction.

11. The method for calculating stiffness of a diaphragm coupling considering service status according to claim 1, characterized in that: The load boundary condition of the torsion analysis is the bolt preload applied to the flange bushing section; the displacement boundary condition of the torsion analysis includes setting the torsion angular displacement θ of the coupling point RP1 and fixing other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2; the torsion angular displacement θ of the coupling point RP1 should make the diaphragm coupling reach the ultimate bearing torque in the torsion direction, yield and produce plastic deformation.

12. The method for calculating stiffness of a diaphragm coupling considering service status according to claim 1, characterized in that: The reset displacement boundary conditions of the torsion analysis include setting the torsion angular displacement β of the coupling point RP1 and fixing other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2; and β=α+n*Δ, wherein α is the torsion angular displacement solved in step S3, n is the number of plastic deformation models of different service degrees of the diaphragm coupling required, and Δ is the differentiation amount of the plastic deformation degree, which is 0.1°~0.3°.

13. The method for calculating stiffness of a diaphragm coupling considering service status according to claim 1, characterized in that: The restart output request outputs the node information of displacement, stress and strain of the torsional defect model of the diaphragm coupling under different torsional angular displacements as the restart information of the plastic deformation model of the diaphragm coupling at different service levels.

14. The method for calculating stiffness of a diaphragm coupling considering service status according to claim 1, characterized in that: Step S5 specifically includes: S5.1, copy the initial finite element model of the diaphragm coupling in step S1 as the basic setting model; S5.

2. Set the restart properties of the model and import the restart information of the plastic deformation model of a certain service level; S5.3, determine the stiffness analysis task; S5.4, set the unloading analysis step and stiffness analysis step; S5.

5. Set the load boundary conditions and displacement boundary conditions for stiffness analysis, and establish the stiffness analysis model of the diaphragm coupling after service.

15. The method for calculating stiffness of a diaphragm coupling considering service status according to claim 14, characterized in that: The model restart attribute is used to import the restart information output from step S4, determine the incremental step by the torsion angular displacement that forms the plastic deformation model of a certain service level, use the restart information of the incremental step as the node result information of the plastic deformation model, and set the initial state of the stiffness analysis model.

16. The method for calculating the stiffness of a diaphragm coupling considering the service state according to claim 14, characterized in that: There are 4 types of stiffness analysis tasks, which are based on a plastic deformation model of a certain service degree, considering the influence of the service state of the diaphragm coupling on its stiffness performance, and performing torsional stiffness analysis, axial stiffness analysis, angular stiffness analysis, and radial stiffness analysis respectively.

17. The method for calculating the stiffness of a diaphragm coupling considering the service state according to claim 16, characterized in that: The unloading analysis step is the first analysis step for restarting the stiffness analysis model, which releases the torsional degree of freedom of the coupling point RP1 and fixes the other degrees of freedom of the coupling point RP1, realizes the automatic unloading of the torsional support reaction torque, and retains the plastic deformation; the stiffness analysis step is used to set the load boundary conditions and displacement boundary conditions of the stiffness analysis, and solves the isotropic stiffness of the diaphragm coupling after service.

18. The method for calculating the stiffness of a diaphragm coupling considering the service state according to claim 17, characterized in that: The load boundary conditions for the torsional stiffness analysis include the bolt preload applied to the flange bushing section, the torsional moment amplitude M applied to the coupling point RP1, and the max ; The torsional moment amplitude M max =1.1M1, M1 is the nominal torque value of the diaphragm coupling; the displacement boundary condition of the torsional stiffness analysis includes releasing the torsional degree of freedom of the coupling point RP1 and fixing the other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2.

19. The method for calculating stiffness of a diaphragm coupling considering service status according to claim 17, characterized in that: The load boundary conditions of the axial stiffness analysis, angular stiffness analysis, and radial stiffness analysis are the same, including the bolt preload applied to the flange bushing section and the torsional moment amplitude M1 applied to the coupling point RP1; the torsional moment amplitude M1 is the nominal torque value of the diaphragm coupling, which is used as the actual working torque borne by the coupling during the stiffness analysis; the displacement boundary conditions of the axial stiffness analysis, angular stiffness analysis, and radial stiffness analysis include setting only one degree of freedom displacement value of the coupling point RP1 and fixing the other degrees of freedom of the coupling point RP1 and all degrees of freedom of the coupling point RP2; for the axial stiffness analysis, the axial degree of freedom displacement value x of the coupling point RP1 is set; for the angular stiffness analysis, the angular degree of freedom displacement value δ of the coupling point RP1 is set; for the radial stiffness analysis, the radial degree of freedom displacement value y of the coupling point RP1 is set.

20. The method for calculating stiffness of a diaphragm coupling considering service status according to claim 17, characterized in that: The coupling point data for torsional stiffness analysis include the displacement data of coupling point RP1 and the torque data of coupling point RP2 within the torque loading range of 0.9M1 to 1.1M1. The load-displacement curve is drawn and the tangent stiffness is solved to obtain the torsional stiffness of the diaphragm coupling when it is subjected to working torque after considering the service state.

21. The method for calculating stiffness of a diaphragm coupling considering service status according to claim 17, characterized in that: The coupling point data of axial stiffness analysis, angular stiffness analysis, and radial stiffness analysis, including the displacement / angular displacement data of coupling point RP1 and the support reaction force / support reaction torque data of coupling point RP2, are used to draw the load-displacement curve and solve the tangent stiffness to obtain the axial stiffness, angular stiffness, and radial stiffness of the diaphragm coupling when it is subjected to working torque after considering the service state.

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