Inter-shaft self-locking nut closing-in process variable parameter influence analysis method based on finite element

Abstract

The invention discloses an inter-axis self-locking nut closing-in process variable parameter influence analysis method based on finite elements. Comprising the steps that S1, a finite element model containing the shaft self-locking nut and the closing-in device is constructed; s2, configuring a material constitutive parameter, a grid parameter, a contact parameter and a boundary parameter; s3, carrying out univariate simulation by taking the key process parameters as variables, and analyzing the forming performance by combining point tracking and cloud atlas; s4, outputting a process optimization scheme; through finite element model construction, multi-dimensional parameter configuration and univariate simulation analysis, the influence rule of key process parameters on equivalent stress, damage distribution and forming load is accurately obtained, the optimal process parameters giving consideration to the forming quality and the production efficiency are determined, and a reliable theoretical basis is provided for actual production process adjustment.

Description

Technical Field

[0001] This invention belongs to the field of numerical simulation technology for high-temperature alloy fastener forming process, and more specifically, it is based on the finite element method for analyzing the influence of process variable parameters on the closing process of inter-shaft self-locking nuts. Background Technology

[0002] Self-locking nuts, with their excellent vibration resistance and anti-loosening performance, have become key fasteners in extreme-condition equipment such as aero-engines and pressure vessels. Their locking performance depends on the quality of the end-forming process. Existing research on the end-forming process of self-locking nuts focuses mainly on ordinary nuts. However, shaft self-locking nuts have unique structural features: a thin-walled structure with a small width-to-diameter ratio and evenly spaced grooves along the circumference. These grooves create a toothed structure at the nut's tail, requiring uniform multi-point interference contact with the external thread through end-forming deformation. The process research for ordinary nuts cannot adapt to the special deformation requirements of shaft self-locking nuts. This results in unclear influence patterns of key process parameters on isostatic stress, damage values, and forming loads during the end-forming process. Process optimization lacks targeted theoretical support, making it difficult to guarantee the stability of forming quality and locking performance, and failing to meet the stringent requirements of high-end equipment for shaft self-locking nuts. Summary of the Invention

[0003] Purpose of the invention: In order to overcome the shortcomings of the existing technology, this invention provides a finite element method for analyzing the influence of process variables on the closing process of inter-shaft self-locking nuts. By constructing a finite element model, configuring multi-dimensional parameters and performing single-variable simulation analysis, the influence of pressing speed, holding time and friction coefficient on equivalent stress, damage distribution and forming load is accurately obtained. The optimal process parameters that take into account both forming quality and production efficiency are determined, providing a reliable theoretical basis for adjusting the actual production process.

[0004] Technical solution: To achieve the above objectives, the present invention provides a finite element-based method for analyzing the influence of process variable parameters on the closing process of inter-shaft self-locking nut, comprising the following steps:

[0005] Step S1: Construct a finite element model of the self-locking nut for shaft forming. The finite element model includes a three-dimensional model of the self-locking nut for shaft and a model of the forming device consisting of an upper mold base, a forming mold, a lower mold base, a positioning base, and a positioning pin.

[0006] Step S2: Configure the multi-dimensional parameters of the finite element model. The configuration includes setting the material properties of each component of the shaft self-locking nut and the closing device, setting the mesh generation parameters, setting the contact interface conditions, and setting the boundary constraints and simulation process control parameters.

[0007] Step S3: Conduct a simulation test on the closing forming process using a single-variable control method and analyze the forming performance. The pressing speed of the closing die, the holding time after forming, and the friction coefficient between the closing device and the shaft self-locking nut are used as independent variables to conduct the test. By combining the point tracking method and the cloud map analysis method, the equivalent stress change, damage distribution and forming load fluctuation of the shaft self-locking nut under different variables are analyzed to obtain the influence law of each process parameter on the forming quality of the shaft self-locking nut.

[0008] Step S4: Based on this influence law, output the parameter optimization direction and application suggestions for the forming process of self-locking nuts for high-temperature alloy shafts, providing a theoretical basis for adjusting the actual production process of self-locking nuts for shafts.

[0009] Furthermore, step S1 includes the following sub-steps:

[0010] Step S1.1: Using 3D solid modeling software, create a 3D model of the self-locking nut for shafts according to its structural features. The structural features of the self-locking nut for shafts include functional areas such as the non-deformable area at the opening, the teeth at the opening and the groove, and the thread.

[0011] Step S1.2: Using 3D solid modeling software, create a 3D model of the closing device according to the assembly relationship between the components in the closing device. In the assembled state, the upper mold base is fixed to the lower surface of the hydraulic press head by screws, the closing mold is coaxially installed below the upper mold base by screws, and the closing end of the closing mold faces downward. The lower mold base is fixed directly below the hydraulic press head, the positioning seat is coaxially installed on the upper surface of the lower mold base, and the periphery of the positioning seat is coaxially fitted with a buffer structure through positioning pins.

[0012] Step S1.3: Export the completed 3D model of the shaft self-locking nut and the 3D model of the closing device as STL format files, import the STL format files into DEFORM-3D finite element simulation software, and in DEFORM-3D finite element simulation software, assign the relevant data of the shaft self-locking nut to the Workpiece plastic body module, and assign the relevant data of each component of the closing device to the TopDie or BottomDie rigid body module respectively;

[0013] Step S1.4: Configure the material constitutive model and material performance parameters of the high-temperature alloy material for the shaft self-locking nut in the DEFORM-3D finite element simulation software to ensure that the model can reflect the plastic deformation characteristics of the high-temperature alloy.

[0014] Furthermore, step S2 includes the following sub-steps:

[0015] Step S2.1: Mesh the self-locking nut for the shaft, select the tetrahedral mesh type suitable for complex plastic deformation regions, and set the total number of meshes, the number of nodes, the mesh size ratio, and the minimum element size to ensure that the mesh in the deformation region of the self-locking nut for the shaft has strong deformation adaptability;

[0016] Step S2.2: Based on the interaction characteristics between the closing device and the shaft self-locking nut during the closing forming process, the shear friction model is selected as the friction model of the contact interface, and the friction coefficient of the contact interface is set.

[0017] Step S2.3: Set boundary conditions and simulation control parameters, set the simulation environment temperature, constrain the radial displacement and axial movement degrees of freedom of the self-locking nut of the shaft to fix the position of the self-locking nut of the shaft, set the lower mold base to be fixed and the upper mold base to move in a preset direction, and determine the displacement step size, total number of steps and the reference value of the upper mold base movement speed in the simulation.

[0018] Furthermore, when the closing forming simulation test and forming performance analysis are carried out in step S3 with the pressing speed of the closing die as an independent variable, the following sub-steps are included:

[0019] Step S3.1: Fix other process parameters, including the closing amount, pressure holding time, and friction coefficient between the closing device and the shaft self-locking nut;

[0020] Step S3.2: Set multiple different values ​​for the pressing speed of the closing mold to form multiple simulation test schemes where only the pressing speed varies;

[0021] Step S3.3: According to each simulation test plan, configure the corresponding pressing speed parameters in the DEFORM-3D finite element simulation software, start the simulation process of the shaft using a self-locking nut to form the shaft, and record the data information in real time during the simulation process;

[0022] Step S3.4: Select multiple representative tracking points inside the thread teeth in the deformation area at the bottom of the self-locking nut tooth profile, and collect the equivalent stress variation data of each tracking point with the forming stroke using the point tracking method;

[0023] Step S3.5: Using the cloud map function of DEFORM-3D finite element simulation software, generate equivalent stress distribution cloud maps and damage distribution cloud maps for the self-locking nut of the shaft under different pressing speeds;

[0024] Step S3.6: Calculate the maximum damage value and maximum forming load of the self-locking nut for shaft in each group of simulation tests, and plot the relationship curves between pressing speed and equivalent stress, damage value and forming load;

[0025] Step S3.7: Based on the collected data, generated cloud maps, and plotted curves, analyze and summarize the influence of pressing speed on the forming performance of shaft self-locking nuts.

[0026] Furthermore, when the closing forming simulation test and forming performance analysis are carried out in step S3 with the holding pressure time after forming as an independent variable, the following sub-steps are included:

[0027] Step S3.8: Fix other process parameters, including the closing amount, the pressing speed of the closing die, and the coefficient of friction between the closing device and the self-locking nut of the shaft;

[0028] Step S3.9: Set multiple different values ​​for the holding time after molding, thereby forming multiple sets of simulation test schemes where only the holding time varies;

[0029] Step S3.10: According to each simulation test plan, configure the corresponding pressure holding time parameters in the DEFORM-3D finite element simulation software, start the simulation process of the shaft using a self-locking nut to form the shaft, and record the data information in real time during the simulation process;

[0030] Step S3.11: Using the cloud map function of DEFORM-3D finite element simulation software, generate equivalent stress distribution cloud maps and damage distribution cloud maps for the shaft self-locking nut at the end of different pressure holding times;

[0031] Step S3.12: Calculate the maximum damage value and maximum forming load of the self-locking nut for the shaft in each group of simulation tests, and plot the relationship curves between the holding time and the equivalent stress, damage value, and forming load;

[0032] Step S3.13: Based on the generated cloud map, statistical indicators, and plotted curves, summarize the influence of pressure holding time on the forming performance of shaft self-locking nuts.

[0033] Furthermore, when the friction coefficient between the closing device and the shaft self-locking nut is used as an independent variable in step S3 to conduct the closing forming simulation test and forming performance analysis, the following sub-steps are included:

[0034] Step S3.14: Fix other process parameters, including the amount of closing, the pressing speed of the closing die, and the holding pressure time after forming;

[0035] Step S3.15: Set multiple different value levels for the friction coefficient between the closing device and the shaft self-locking nut to form multiple sets of simulation test schemes where only the friction coefficient changes;

[0036] Step S3.16: According to each simulation test plan, configure the corresponding friction coefficient parameters in the DEFORM-3D finite element simulation software, start the simulation process of the shaft using a self-locking nut to form the shaft, and record the data information in real time during the simulation process;

[0037] Step S3.17: Select multiple representative tracking points inside the thread teeth in the deformation area at the bottom of the self-locking nut tooth profile, and collect the equivalent stress variation data of each tracking point with the forming stroke using the point tracking method;

[0038] Step S3.18: Using the cloud map function of DEFORM-3D finite element simulation software, generate equivalent stress distribution cloud maps and damage distribution cloud maps for self-locking nuts on shafts under different friction coefficients;

[0039] Step S3.19: Calculate the maximum damage value and maximum forming load of the shaft self-locking nut in each group of simulation tests, and plot the relationship curves between the friction coefficient and the equivalent stress, damage value, and forming load;

[0040] Step S3.20: Based on the collected data, generated cloud maps, and plotted curves, summarize the influence of friction coefficient on the forming performance of shaft self-locking nuts.

[0041] Furthermore, step S4 includes the following sub-steps:

[0042] Step S4.1: Based on the influence of each process parameter summarized in step S3, select the pressing speed range, holding time range and friction coefficient range that can reduce the equivalent stress of the shaft self-locking nut, reduce the damage value of the shaft self-locking nut, optimize the forming load of the shaft self-locking nut and ensure the uniformity of the deformation of the shaft self-locking nut.

[0043] Step S4.2: Taking into account the forming quality of the self-locking nut for shafts, including the uniformity of deformation and the degree of damage, and the production efficiency, including the forming cycle, determine the optimal combination of process parameters that balances performance and efficiency within the selected parameter range.

[0044] Step S4.3: Output a process optimization scheme that includes the optimal combination of process parameters, the principle of parameter adjustment (i.e., the adjustment direction when parameters deviate from the optimal value), and the key points of forming quality control for self-locking nuts for shafts, providing a theoretical basis for adjusting the forming process in the actual production of self-locking nuts for shafts.

[0045] Furthermore, step S1.3 includes the following sub-steps:

[0046] Step S1.4.1: Select a suitable constitutive model that can characterize the plastic stress characteristics of the high-temperature alloy constituting the shaft self-locking nut under different strain, strain rate and temperature conditions, and adapt to the deformation mechanism of the high-temperature alloy.

[0047] Step S1.4.2: Input the material property parameters of the high-temperature alloy, including static strength parameters, strain hardening parameters, strain rate sensitive parameters, temperature sensitive parameters, material melting point, room temperature, etc., into the constitutive model;

[0048] Step S1.4.3: Enable the material volume compensation function in the DEFORM-3D finite element simulation software. This allows the DEFORM-3D finite element simulation software to dynamically adjust the overall volume of the shaft self-locking nut according to the preset target volume during the mesh re-division process, thereby reducing the simulation error caused by mesh deformation.

[0049] Furthermore, step S2.1 includes the following sub-steps:

[0050] Step S2.1.1: Based on the structural dimensions and deformation complexity of the self-locking nut for shafts, determine the total number of tetrahedral meshes and the number of nodes to ensure that the number of meshes can meet the calculation accuracy requirements of the simulation of the self-locking nut for shafts forming.

[0051] Step S2.1.2: Set the mesh size ratio and minimum cell size so that the mesh cell size of the deformation area of ​​the self-locking nut of the shaft is adapted to its plastic deformation requirements and is smaller than the mesh cell size of the non-deformation area. At the same time, the mesh cell density of the deformation area is higher than that of the non-deformation area to improve the mesh's ability to follow plastic deformation.

[0052] Step S2.1.3: Use the mesh generation function of DEFORM-3D finite element simulation software to mesh the self-locking nut for the shaft. After mesh generation, check the mesh quality and adjust and optimize areas with unsatisfactory mesh quality to ensure that the mesh can support subsequent simulation calculations of the self-locking nut's tapering and forming.

[0053] Furthermore, step S2.3 includes the following sub-steps:

[0054] Step S2.3.1: Based on the actual processing environment of the self-locking nut for shaft forming and the set simulation environment temperature, without setting additional heat transfer conditions for the self-locking nut for shaft, match the actual room temperature forming conditions of the self-locking nut for shaft.

[0055] Step S2.3.2: Using the constraint function of DEFORM-3D finite element simulation software, constrain the radial displacement of the self-locking nut of the shaft using the relevant parameters of the positioning seat, and at the same time directly constrain the axial movement degree of freedom of the self-locking nut of the shaft to avoid positional displacement during the forming process of the self-locking nut of the shaft.

[0056] Step S2.3.3: In the simulation control module of DEFORM-3D finite element simulation software, the lower mold base is set to remain fixed, and the upper mold base drives the closing mold to move along the axial direction. The total moving distance of the upper mold base is controlled by setting the minimum displacement step and the total number of steps to ensure that the movement of the upper mold base meets the closing forming requirements of the shaft self-locking nut.

[0057] Beneficial Effects: Compared with existing technologies, the finite element-based method for analyzing the influence of process variable parameters on the closing process of the self-locking nut between shafts in this invention has the following beneficial effects:

[0058] 1. The self-locking nut for the shaft and the closing device are integrated into the same finite element model. Combined with the constitutive model adapted to the characteristics of high-temperature alloy materials and the material volume compensation function, the real closing conditions can be accurately reproduced, avoiding simulation deviations caused by model splitting or mesh deformation.

[0059] 2. Through single-variable control experiments, the influence of each process parameter on forming performance is clearly revealed, providing directions for parameter optimization.

[0060] 3. The optimal combination of output process parameters takes into account both forming quality and production efficiency, which can directly guide actual production, reduce trial and error costs, improve the locking performance and service life of shaft self-locking nuts, and meet the application needs of high-end equipment. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of the self-locking nut for the shaft in this scheme;

[0062] Figure 2 This is a schematic diagram of the assembly of the self-locking nut for the shaft and the closing device in this scheme;

[0063] Figure 3 A schematic diagram of the mesh division for a self-locking nut for a shaft;

[0064] Figure 4 This is a schematic diagram showing the location distribution of each tracking point in the point tracking method.

[0065] Figure 5 The graph shows the equivalent stress at each tracking point as a function of stroke under different downward pressure speeds.

[0066] Figure 6 Damage distribution cloud map of the self-locking nut for shaft under different compression speeds;

[0067] Figure 7 The graph shows the maximum damage value of the self-locking nut for shaft as a function of the pressing speed.

[0068] Figure 8 A graph showing the variation of the forming load of the self-locking nut on the shaft of the die at different pressing speeds as a function of stroke;

[0069] Figure 9 The equivalent stress distribution cloud map of the self-locking nut for shaft at the end of different holding times;

[0070] Figure 10 The damage distribution cloud map of the self-locking nut for shaft under different holding times;

[0071] Figure 11 Forming load curves for different holding times;

[0072] Figure 12 The graph shows the equivalent stress at each tracking point as a function of travel under different friction coefficients.

[0073] Figure 13 Damage distribution cloud maps of self-locking nuts for shafts under different friction coefficients;

[0074] Figure 14 The forming load curves are shown for different friction coefficients. Detailed Implementation

[0075] The invention will now be further described with reference to the accompanying drawings.

[0076] Taking a certain type of GH2132 high-temperature alloy shaft self-locking nut 1 as the research object, this paper introduces in detail the numerical simulation method of the forming process of the high-temperature alloy shaft self-locking nut 1 described in this scheme. The shaft self-locking nut 1 has an outer diameter of 56mm, an inner diameter of 48mm, and an overall width of 9mm. Eight slots are evenly opened along the circumference, each slot having a length of 10mm and a width of 4mm. The evenly spaced distribution of the slots allows the tooth-like structure formed at the tail of the nut to form a uniform multi-point interference contact with the external thread after the forming deformation.

[0077] The finite element method-based analysis of the influence of process variables on the closing process of inter-shaft self-locking nuts includes the following steps:

[0078] Step S1: Construct a finite element model of the self-locking nut 1 for shaft forming. This finite element model includes a three-dimensional model of the self-locking nut 1 for shaft forming and a model of the forming device 2 consisting of a lower mold base 5, a positioning pin 10, a positioning seat 6, a forming mold 4, and an upper mold base 3. The core components of the self-locking nut 1 for shaft forming and the forming device 2 are integrated into a unified finite element model, which can accurately reproduce the collaborative effect between the components in the actual forming process and avoid simulation deviations caused by model splitting.

[0079] Step S2: Configure multi-dimensional parameters for the finite element model. The parameter configuration includes setting the material properties of each component of the self-locking nut 1 and the closing device 2, setting the mesh generation parameters, setting the contact interface conditions, and setting the boundary constraints and simulation process control parameters. Among them, the material properties determine the plastic deformation characteristics of the high-temperature alloy of the self-locking nut 1, the mesh generation parameters affect the accuracy and efficiency of the simulation calculation, the setting of the contact interface conditions constrains the interaction between the closing device 2 model and the self-locking nut 1, making the simulation results more realistic, and the setting of boundary constraints and simulation control parameters can ensure that the simulation process fits the actual production conditions.

[0080] Step S3: A single-variable control method is used to conduct a simulation test of the closing forming process and to analyze the forming performance. The pressing speed of the closing mold 4, the holding time after forming, and the friction coefficient between the closing device 2 and the shaft self-locking nut 1 are used as independent variables to conduct separate tests. By combining the point tracking method and the cloud map analysis method, the equivalent stress change, damage distribution, and forming load fluctuation of the shaft self-locking nut 1 under different variables are analyzed to obtain the influence law of each process parameter on the forming quality of the shaft self-locking nut 1. Among them, the point tracking method can accurately capture the stress dynamic change in the key deformation area of ​​the shaft self-locking nut 1, and the cloud map analysis method can intuitively present the spatial distribution characteristics of stress and damage. The combination of the two can accurately locate the correlation between the influence of process parameters on local stress concentration and overall damage.

[0081] Step S4: Based on the influence law, output the parameter optimization direction and application suggestions for the forming process of the self-locking nut 1 for high-temperature alloy shafts, and provide a theoretical basis for the adjustment of the actual production process of the self-locking nut 1 for shafts.

[0082] More specifically, step S1 includes the following sub-steps:

[0083] Step S1.1: In the embodiments described in this solution, SolidWorks is selected as the 3D solid modeling software. In addition, those skilled in the art can also use commonly used 3D solid modeling software such as UG and 3ds Max for modeling. Using SolidWorks 3D solid modeling software, a 3D model of the self-locking nut 1 is created according to its structural features, such as... Figure 1 As shown, the structural features of the shaft self-locking nut 1 include a non-deformable area 1a, a toothed portion 1b, a groove 1c, and a threaded thread 1d, among other functional areas. The non-deformable area 1a ensures the overall stability of the shaft self-locking nut 1 during the self-locking process. The toothed portion 1b is the functional area for locking the shaft self-locking nut 1. The groove 1c and threaded thread 1d respectively meet the requirements for threaded connection and multi-point interference contact.

[0084] Step S1.2: Using SolidWorks 3D solid modeling software, create a 3D model of the sealing device 2 according to the assembly relationships between the components in the sealing device 2; for example... Figure 2 As shown, in the assembled state, the upper mold base 3 is fixed to the lower surface of the hydraulic press head by screws 9. The closing mold 4 is coaxially mounted below the upper mold base 3 by screws 9, with the closing end of the closing mold 4 facing downwards. The lower mold base 5 is fixed directly below the hydraulic press head. The positioning seat 6 is coaxially mounted on the upper surface of the lower mold base 5. A buffer structure is coaxially sleeved around the periphery of the positioning seat 6 by positioning pins 10. The buffer structure includes a thick washer 7 and an adjusting washer 8 arranged sequentially from top to bottom. The thick washer 7 bears the main pressure applied by the upper mold base 3, and the adjusting washer 8 provides protection against minor pressure fluctuations. The difference in height is compensated, and the two work together to meet the height change requirements during the closing experiment; more specifically, after the shaft self-locking nut 1 model is installed in the three-dimensional model of the closing device 2, the shaft self-locking nut 1 is coaxially installed on the upper surface of the positioning seat 6, and the closing deformation area located at the upper end of the shaft self-locking nut 1 abuts against the closing inner wall on the closing mold 4; thereby ensuring that when the closing mold 4 moves downward under the drive of the upper mold seat 3, it can directly act on the closing tooth 1b area of ​​the shaft self-locking nut 1, avoiding energy loss caused by excessive force transmission path, and the coaxial installation can ensure the uniformity of closing deformation;

[0085] Step S1.3: Export the completed 3D model of the self-locking nut 1 and the 3D model of the closing device 2 as STL format files. The STL format file can preserve the geometric integrity of the model. Import the STL format file into the DEFORM-3D finite element simulation software. In the DEFORM-3D finite element simulation software, assign the relevant data of the self-locking nut 1 to the Workpiece plastic body module, and assign the relevant data of each component of the closing device 2 to the TopDie or BottomDie rigid body module respectively. After assigning each component of the closing device 2 to the rigid body module, the deformation of the closing device 2 itself during the experiment can be ignored, ensuring that only the influence of the preset variables in step S3 on the simulation results is considered during the experiment.

[0086] Step S1.4: Configure the material constitutive model and material performance parameters of the high-temperature alloy material for the self-locking nut 1 of the shaft in the DEFORM-3D finite element simulation software to ensure that the model can reflect the plastic deformation characteristics of the high-temperature alloy.

[0087] More specifically, step S1.4 includes the following sub-steps:

[0088] Step S1.4.1: In this scheme, the Johnson-Cook constitutive model is selected as the constitutive model for high-temperature alloy materials. The Johnson-Cook constitutive model can characterize the plastic stress characteristics of high-temperature alloys under different strain, strain rate and temperature conditions, and is suitable for the deformation mechanism of high-temperature alloys.

[0089] Step S1.4.2: Input the material property parameters of the high-temperature alloy, including static strength parameters, strain hardening parameters, strain rate sensitive parameters, temperature sensitive parameters, material melting point, room temperature, etc., into the Johnson-Cook constitutive model; the expression of the Johnson-Cook constitutive model is:

[0090]

[0091] in,

[0092] : The yield strength of the material at a set temperature;

[0093] : refers to the hardening modulus of the material;

[0094] : is the strain rate hardening parameter of the material;

[0095] : refers to the hardening index of the material;

[0096] : is the strain rate sensitivity index of the material;

[0097] : refers to the plastic stress of the material;

[0098] : is the equivalent plastic strain of the material;

[0099] : is the equivalent plastic strain rate of the material;

[0100] : is the reference strain rate;

[0101] : The pre-set experimental temperature;

[0102] : is the melting point temperature of the material;

[0103] : refers to room temperature;

[0104] In the embodiments described in this scheme, the high-temperature alloy is GH2132, and its static strength parameters are... =694MPa, strain hardening parameter =1042MPa, strain rate sensitive parameter =0.00418, Hardening Index =0.75, temperature-sensitive parameter =1.81, material melting point =1424℃, room temperature =25℃,

[0105] Step S1.4.3: Enable the material volume compensation function in the DEFORM-3D finite element simulation software. This allows the DEFORM-3D finite element simulation software to dynamically adjust the overall volume of the shaft self-locking nut 1 according to the preset target volume during the mesh re-division process, thereby reducing the simulation error caused by mesh deformation. The material volume compensation function can ensure that the nut volume deviation is ≤1% after mesh re-division, avoiding density calculation errors caused by volume changes.

[0106] More specifically, step S2 includes the following sub-steps:

[0107] Step S2.1: Mesh the self-locking nut 1 for the shaft, select a tetrahedral mesh type suitable for complex plastic deformation regions, and set the total number of meshes, the number of nodes, the mesh size ratio, and the minimum element size to ensure that the mesh in the deformation region of the self-locking nut 1 for the shaft has strong deformation adaptability; wherein, the setting of the number of meshes and the mesh size needs to be determined in conjunction with the small width-to-diameter ratio and thin-walled structure characteristics of the nut; in the embodiment described in this scheme, the total number of meshes is set to 250,000, the number of nodes after meshing is 45,320, the mesh size ratio is 2, and the minimum element size is 0.276mm;

[0108] Step S2.2: Based on the interaction characteristics between the closing device 2 and the shaft self-locking nut 1 during the closing forming process, a shear friction model is selected as the friction model of the contact interface, and the friction coefficient of the contact interface is set; the specific value of the friction coefficient needs to be determined with reference to the material friction coefficient data table. In this scheme, the initial friction coefficient between each contact body is set to 0.12.

[0109] Step S2.3: Set boundary conditions and simulation control parameters, set the simulation environment temperature, constrain the radial displacement and axial movement degrees of freedom of the self-locking nut 1 to fix the position of the self-locking nut 1, set the lower mold base 5 to be fixed and the upper mold base 3 to move in a preset direction, and determine the simulation displacement step size, total number of steps and the reference value of the upper mold base 3's movement speed. In the embodiment described in this scheme, the simulation environment temperature is set to 20℃, the minimum displacement step size is 0.01mm, the total number of steps needs to be determined according to the upper mold movement distance and no specific value is provided here, and the reference value of the upper mold base 3's movement speed is set to 20mm / s.

[0110] More specifically, step S2.1 includes the following sub-steps:

[0111] Step S2.1.1: Based on the structural dimensions and deformation complexity of the self-locking nut 1 for the shaft, determine the total number of tetrahedral meshes and the number of nodes to ensure that the mesh count meets the computational accuracy requirements for the simulation of the self-locking nut 1 for the shaft's tapering process; for example... Figure 3 As shown in the embodiment described in this solution, the total number of grids is set to 250,000, and the number of nodes after grid division is 45,320.

[0112] Step S2.1.2: Set the mesh size ratio and minimum element size so that the mesh element size of the deformable region of the self-locking nut 1 is adapted to its plastic deformation requirements and smaller than the mesh element size of the non-deformable region. At the same time, the mesh element density of the deformable region is higher than that of the non-deformable region to improve the mesh's ability to follow plastic deformation. In the embodiment described in this solution, the mesh size ratio is set to 2 and the minimum element size is 0.276mm. This minimum element size matches the nut wall thickness of 4mm. When dividing the mesh, it is necessary to ensure that at least 14 mesh elements are distributed in the wall thickness direction of the self-locking nut 1 to avoid averaging errors in stress calculation.

[0113] Step S2.1.3: Start the mesh generation function of DEFORM-3D finite element simulation software to generate a mesh for the self-locking nut 1 of the shaft. After the generation is completed, check the mesh quality and adjust and optimize the areas with unqualified mesh quality to ensure that the mesh can support the subsequent simulation calculation of the self-locking nut 1 of the shaft for forming. In particular, at the groove and thread connection of the self-locking nut 1 of the shaft, the mesh is prone to distortion due to the complex shape of this area. It is necessary to adjust the element size or topology to make the mesh quality meet the standard and avoid the calculation interruption caused by mesh distortion during the simulation.

[0114] More specifically, step S2.3 includes the following sub-steps:

[0115] Step S2.3.1: Based on the actual processing environment of the self-locking nut 1 for shaft forming and the set simulation environment temperature, without setting additional heat transfer conditions for the self-locking nut 1 for shaft forming, match the actual room temperature forming condition of the self-locking nut 1 for shaft forming. In the embodiment described in this solution, the set simulation environment temperature is 20℃, which is close to the room temperature Tr=25℃ in the GH2132 constitutive model. This can reduce the interference of temperature difference on the calculation of material plastic stress, and at the same time, it fits the actual room temperature processing condition without additional heating or cooling, avoiding temperature field distortion caused by improper heat transfer condition settings.

[0116] Step S2.3.2: Using the constraint function of DEFORM-3D finite element simulation software, constrain the radial displacement of the self-locking nut 1 of the shaft using the relevant parameters of the positioning seat 6, and at the same time directly constrain the axial movement degree of freedom of the self-locking nut 1 of the shaft to avoid positional displacement of the self-locking nut 1 of the shaft during the forming process.

[0117] Step S2.3.3: In the simulation control module of DEFORM-3D finite element simulation software, the lower mold base 5 is set to remain fixed, and the upper mold base 3 drives the closing mold 4 to move along the axial direction. The total moving distance of the upper mold base 3 is controlled by setting the minimum displacement step and the total number of steps to ensure that the movement of the upper mold base 3 meets the closing forming requirements of the shaft self-locking nut 1.

[0118] More specifically, when the pressing speed of the closing die 4 is used as an independent variable in step S3 to conduct the closing forming simulation test and forming performance analysis, it includes the following sub-steps:

[0119] Step S3.1: Fix other process parameters. In the embodiment described in this solution, other process parameters include a closing amount of 0.3 mm, a holding time of 1 s, and a friction coefficient of 0.2 between the closing device 2 and the shaft self-locking nut 1.

[0120] Step S3.2: Set multiple different values ​​for the pressing speed of the closing mold 4. In the embodiment described in this scheme, the pressing speed of the closing mold 4 is set to four different values: 20mm / s, 40mm / s, 60mm / s, and 80mm / s, thereby forming multiple sets of simulation test schemes with only the pressing speed changing.

[0121] Step S3.3: According to each simulation test plan, configure the corresponding pressing speed parameters in the DEFORM-3D finite element simulation software, start the simulation process of the self-locking nut 1 forming the shaft, and record the data information in real time during the simulation process; among which, the data that needs to be recorded in real time during this experiment includes important data such as stress changes, damage evolution and load fluctuations at each tracking point in the point tracking method;

[0122] Step S3.4: Select multiple representative tracking points inside the thread teeth in the deformation area at the bottom of the self-locking nut 1 for the shaft, and collect the equivalent stress variation data of each tracking point with the forming stroke using the point tracking method; such as Figure 4 As shown in the embodiment described in this solution, the line connecting the thread root closest to the bottom of the slot 1c in the deformation area at the bottom of the self-locking nut tooth profile is selected as the selection area, and four tracking points P1, P2, P3, and P4 are set at equal intervals from top to bottom in the selection area, wherein P1 and P4 coincide with the intersection of the tooth root.

[0123] Step S3.5: Using the cloud map function of DEFORM-3D finite element simulation software, generate equivalent stress distribution cloud maps and damage distribution cloud maps for the self-locking nut 1 of the shaft under different pressing speeds. The cloud maps can intuitively show the expansion trend of the stress concentration area when the speed increases.

[0124] Step S3.6: Statistically analyze the maximum damage value and maximum forming load of the self-locking nut 1 for the shaft in each simulation test group, and plot the relationship curves between the pressing speed and the equivalent stress, damage value, and forming load. Various curve images generated during this experiment are shown below. Figures 5-8 As shown;

[0125] Step S3.7: Based on the collected data, generated cloud map and plotted curve, analyze and summarize the influence law of pressing speed on the forming performance of shaft self-locking nut 1;

[0126] like Figure 5 As shown, the equivalent stress at points P1, P2, P3, and P4 increases slightly with increasing compression speed. At the beginning of the stroke, the equivalent stress at all compression speeds rises rapidly. As the stroke increases, the curve begins to level off, indicating that the stress value stabilizes at this stage, but higher compression speeds still exhibit slightly higher stress values. This shows that the equivalent stress tends to increase with increasing compression speed; as... Figure 6 and Figure 7 As shown, at three different compression speeds of 20, 40, 60, and 80 mm / s, the maximum damage values ​​were 0.124, 0.120, 0.135, and 0.136, respectively. The damage values ​​first decreased and then increased, exhibiting a fluctuating trend. The damage was lowest at 40 mm / s, then increased significantly at 60 mm / s, and slightly increased at 80 mm / s. This indicates that excessively high speeds prevent the material from deforming uniformly, leading to increased frictional heat accumulation or dynamic effects, thus exacerbating the damage. However, at 20 mm / s, despite being the lowest speed, the damage value was still higher than at 40 mm / s, possibly due to prolonged contact time at low speeds, resulting in damage caused by frictional effects or the accumulation of microscopic defects. Figure 8 As shown, the load fluctuation varies with different compression speeds. At higher speeds (e.g., 60 mm / s and 80 mm / s), the load fluctuates significantly throughout the stroke, possibly due to greater impact or unstable material deformation caused by the higher compression speed. At compression speeds of 20 mm / s and 40 mm / s, the load changes relatively smoothly without drastic fluctuations, indicating more uniform deformation of the part at these speeds. At compression speeds of 20, 40, 60, and 80 mm / s, the maximum forming loads throughout the stroke are 13900 N, 14800 N, 15200 N, and 15400 N, respectively. The maximum forming load increases with increasing compression speed. Therefore, higher speeds during forming can affect the uniform deformation and forming quality of the part.

[0127] More specifically, when the closing forming simulation test and forming performance analysis are carried out in step S3 with the holding pressure time after forming as an independent variable, the following sub-steps are included:

[0128] Step S3.8: Fix other process parameters, including a closing amount of 0.3mm, a pressing speed of the closing die 4 of 20mm / s, and a friction coefficient of 0.2 between the closing device 2 and the self-locking nut 1; wherein the fixed closing amount can ensure that the deformation of the nut is consistent under each pressure holding time;

[0129] Step S3.9: Set multiple different values ​​for the holding time after molding. In the embodiment described in this scheme, the holding time after molding is set to four different values: 0.5s, 1s, 1.5s, and 2s, thereby forming multiple sets of simulation test schemes where only the holding time varies.

[0130] Step S3.10: According to each simulation test plan, configure the corresponding pressure holding time parameters in the DEFORM-3D finite element simulation software, start the simulation process of the self-locking nut 1 forming the shaft, and record the data information in real time during the simulation process; among which, the data that needs to be recorded in real time during this experiment includes important data such as stress decay rate and damage change trend;

[0131] Step S3.11: Using the cloud map function of DEFORM-3D finite element simulation software, generate equivalent stress distribution cloud maps and damage distribution cloud maps for the shaft self-locking nut 1 at the end of different pressure holding times;

[0132] Step S3.12: Statistically analyze the maximum damage value and maximum forming load of the self-locking nut 1 for the shaft in each simulation test, and plot the relationship curves between holding time and equivalent stress, damage value, and forming load; various curve images generated during this experiment are as follows: Figures 9-11 As shown;

[0133] Step S3.13: Based on the generated cloud map, statistical indicators and plotted curves, summarize the influence of holding time on the forming performance of the shaft self-locking nut 1;

[0134] like Figure 9As shown, at the end of the holding time of 0.5s, the equivalent stress is 1060 MPa; at the end of the holding time of 1s, the equivalent stress is 1030 MPa; at the end of the holding time of 1.5s, the equivalent stress is 998 MPa; and at the end of the holding time of 2s, the equivalent stress is 959 MPa. As the holding time increases from 0.5 seconds to 2 seconds, the equivalent stress decreases from 1060 MPa to 959 MPa, showing a gradual decrease in equivalent stress with increasing holding time. This indicates that as the holding time extends, the deformation of the material gradually stabilizes, and the stress in the material is gradually released and homogenized. Therefore, appropriately extending the holding time helps to release stress, thereby improving the forming quality of the part; for example... Figure 10 As shown, the maximum damage value is 0.121 when the holding time is 0.5 seconds, 0.113 when the holding time is 1 second, 0.105 when the holding time is 1.5 seconds, and 0.096 when the holding time is 2 seconds. The damage value is higher when the holding time is shorter, which may be due to incomplete deformation of the material in a short time, leading to excessive stress in local areas and thus increasing damage. As the holding time increases, the damage value gradually decreases, indicating that a longer holding time helps the material to deform fully and reduces local stress concentration, thereby reducing damage. Figure 11 As shown, the maximum forming load is 14800 N when the holding time is 0.5 seconds, 14700 N when the holding time is 1 second, 14600 N when the holding time is 1.5 seconds, and 14400 N when the holding time is 2 seconds. With increasing holding time, the forming load gradually decreases. When the holding time is short, incomplete material deformation may lead to uneven pressure distribution within the mold, requiring a larger load to force the material to complete deformation. With increasing holding time, the material has more time to fully deform within the mold, resulting in a smoother deformation process and reducing the required forming load. Therefore, a longer holding time helps reduce the forming load and improves the stability and uniformity of the nut closing forming process.

[0135] More specifically, when conducting the closing forming simulation test and forming performance analysis in step S3 using the friction coefficient between the closing device 2 and the shaft self-locking nut 1 as an independent variable, the following sub-steps are included:

[0136] Step S3.14: Fix other process parameters, including a closing amount of 0.3mm, a pressing speed of the closing mold 4 of 20mm / s, and a holding time of 1s after forming;

[0137] Step S3.15: Set multiple different values ​​for the friction coefficient between the closing device 2 and the shaft self-locking nut 1. In the embodiment described in this scheme, the friction coefficient between the closing device 2 and the shaft self-locking nut 1 is set to four different values: 0.1, 0.2, 0.3, and 0.4, forming multiple sets of simulation test schemes where only the friction coefficient changes.

[0138] Step S3.16: According to each simulation test plan, configure the corresponding friction coefficient parameters in the DEFORM-3D finite element simulation software, start the simulation process of the self-locking nut 1 forming the shaft, and record the data information in real time during the simulation process; among which, the data that needs to be recorded in real time during this experiment includes important data such as the change of friction force at the contact interface and stress transmission.

[0139] Step S3.17: Select several representative tracking points inside the thread teeth in the deformation area at the bottom of the self-locking nut 1 on the shaft, such as... Figure 4 As shown in the embodiment described in this solution, the line connecting the thread root closest to the bottom of the slot 1c in the deformation area at the bottom of the self-locking nut tooth profile is selected as the selection area, and four tracking points P1, P2, P3, and P4 are set at equal intervals from top to bottom in the selection area, wherein P1 and P4 coincide with the intersection of the tooth root.

[0140] Step S3.18: Using the cloud map function of DEFORM-3D finite element simulation software, generate equivalent stress distribution cloud maps and damage distribution cloud maps for the shaft self-locking nut 1 under different friction coefficients;

[0141] Step S3.19: Statistically analyze the maximum damage value and maximum forming load of the self-locking nut 1 for the shaft in each simulation test, and plot the relationship curves between the friction coefficient and the equivalent stress, damage value, and forming load; various curve images generated during this experiment are as follows: Figures 12-14 As shown;

[0142] Step S3.20: Based on the collected data, generated cloud map and plotted curve, summarize the influence law of friction coefficient on the forming performance of shaft self-locking nut 1.

[0143] like Figure 12As shown, under the same stroke, the equivalent stress gradually increases as the friction coefficient gradually increases from 0.1 to 0.4. This is because the increase in friction leads to increased resistance during deformation, resulting in greater stress on the material. A higher friction coefficient means greater friction between the material and the mold, increasing the difficulty of deformation and leading to stress concentration. A lower friction coefficient helps the material flow and deform more smoothly during forming, thus reducing stress. A higher friction coefficient increases the deformation resistance of the material, leading to an increase in stress level. This trend is reflected in the data at various points (P1, P2, P3, P4), where the increase in stress gradually increases with the increase in friction coefficient; for example... Figure 13 As shown, the maximum damage value is 0.121 when the friction coefficient is 0.1, 0.123 when the friction coefficient is 0.2, 0.124 when the friction coefficient is 0.3, and 0.125 when the friction coefficient is 0.4. The data shows that the maximum damage value gradually increases with the increase of the friction coefficient. Although the increase is small, the influence of the friction coefficient on the damage value is obvious. A lower friction coefficient means less friction between the material and the mold, resulting in smoother material flow and more uniform deformation during the forming process. The material will not undergo excessive deformation or localized damage due to excessive friction, thus improving the surface quality and shape accuracy of the parts. To reduce damage to parts, materials with lower friction coefficients should be used as much as possible, or lubrication conditions should be optimized to minimize damage during the forming process; for example... Figure 14 The maximum forming loads were 14800 N, 16000 N, 16700 N, and 17400 N when the friction coefficients were 0.1, 0.2, 0.3, and 0.4, respectively. The maximum forming load showed a gradual upward trend with increasing friction coefficients. This phenomenon is mainly attributed to the increased friction at the material-mold interface. When the friction coefficient is high, the relative sliding between the blank and the mold during deformation is subject to greater resistance, restricting material flow and thus increasing the external load required for plastic deformation. Higher friction coefficients require larger forming loads and may lead to uneven deformation, while lower friction coefficients help the material flow more uniformly during forming, reducing stress concentration and improving the forming quality of the parts.

[0144] More specifically, step S4 includes the following sub-steps:

[0145] Step S4.1: Based on the influence of each process parameter summarized in step S3, select the pressing speed range, holding time range and friction coefficient range that can reduce the equivalent stress of the shaft self-locking nut 1, reduce the damage value of the shaft self-locking nut 1, optimize the forming load of the shaft self-locking nut 1 and ensure the uniformity of deformation of the shaft self-locking nut 1.

[0146] Step S4.2: Considering both the forming quality of the self-locking nut 1 (including the uniformity of deformation and the degree of damage) and production efficiency (including the forming cycle), determine the optimal combination of process parameters that balances performance and efficiency within the selected parameter range. In the embodiment described in this scheme, the final optimal parameter combination is: a pressing speed of the closing die 4 of 40 mm / s, a holding time after forming of 1.5 s, and a friction coefficient of 0.15 between the closing device 2 and the self-locking nut 1. This combination ensures forming quality while avoiding reduced production efficiency due to excessively long holding time.

[0147] Step S4.3: Output a process optimization scheme that includes the optimal combination of process parameters, parameter adjustment principles (i.e., the adjustment direction when parameters deviate from the optimal value), and key points for quality control of the forming of the self-locking nut 1 for shafts. This provides a theoretical basis for adjusting the forming process in the actual production of the self-locking nut 1 for shafts. If the damage value of the nut is too high after forming, the holding time can be appropriately extended or the friction coefficient can be reduced. If the forming load exceeds the equipment capacity, the friction coefficient should be reduced first rather than the pressing speed to avoid efficiency loss.

[0148] Similarly, those skilled in the art can refer to the technical solution of the finite element method for analyzing the influence of process variable parameters on the closing of shaft self-locking nuts described in this solution. They can then explore the influence of the synergy between multiple process variables on the closing of shaft self-locking nuts by changing multiple process variable parameters simultaneously. Without changing the analysis principle, changing the number of parameters that need to be changed in a single experiment should also fall within the scope of this solution.

[0149] The above are the preferred embodiments described in this invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.

Claims

1. A method for analyzing the influence of process variable parameters on the closing of self-locking nuts between shafts based on finite element method, characterized in that: Includes the following steps: Step S1: Construct a finite element model of the self-locking nut (1) for shaft forming. The finite element model includes a three-dimensional model of the self-locking nut (1) for shaft forming and a model of the forming device (2) consisting of an upper mold base (3), a forming mold (4), a lower mold base (5), a positioning base (6), and a positioning pin (10). Step S2: Configure the multi-dimensional parameters of the finite element model. The configuration includes setting the material properties of each component of the shaft self-locking nut (1) and the closing device (2), setting the mesh generation parameters, setting the contact interface conditions, and setting the boundary constraints and simulation process control parameters. Step S3: A single-variable control method is used to carry out a simulation test of the closing forming and to analyze the forming performance. The pressing speed of the closing mold (4), the holding time after forming, and the friction coefficient between the closing device (2) and the shaft self-locking nut (1) are used as independent variables to carry out the test. By combining the point tracking method and the cloud map analysis method, the equivalent stress change, damage distribution and forming load fluctuation of the shaft self-locking nut (1) under different variables are analyzed to obtain the influence law of each process parameter on the forming quality of the shaft self-locking nut (1). Step S4: Based on the influence law, output the parameter optimization direction and application suggestions for the forming process of the self-locking nut (1) for high-temperature alloy shafts, and provide a theoretical basis for the adjustment of the actual production process of the self-locking nut (1) for shafts.

2. The method for analyzing the influence of process variable parameters of inter-shaft self-locking nut closing process based on finite element method according to claim 1, characterized in that: Step S1 includes the following sub-steps: Step S1.1: Using three-dimensional solid modeling software, create a three-dimensional model of the self-locking nut (1) for shafts according to its structural features. The structural features of the self-locking nut (1) for shafts include functional areas such as the non-deformation area (1a), the toothed part (1b), the groove (1c), and the thread (1d). Step S1.2: Using 3D solid modeling software, create a 3D model of the closing device (2) according to the assembly relationship between the components in the closing device (2). In the assembled state, the upper mold base (3) is fixed to the lower surface of the hydraulic press head by screws (9), the closing mold (4) is coaxially installed below the upper mold base (3) by screws (9), and the closing of the closing mold (4) is facing down. The lower mold base (5) is fixed directly below the hydraulic press head, the positioning seat (6) is coaxially installed on the upper surface of the lower mold base (5), and the periphery of the positioning seat (6) is coaxially fitted with a buffer structure by positioning pins (10). Step S1.3: Export the completed 3D model of the shaft self-locking nut (1) and the 3D model of the closing device (2) as STL format files, import the STL format files into DEFORM-3D finite element simulation software, and in DEFORM-3D finite element simulation software, assign the relevant data of the shaft self-locking nut (1) to the Workpiece plastic body module, and assign the relevant data of each component of the closing device (2) to the TopDie or BottomDie rigid body module respectively; Step S1.4: Configure the material constitutive model and material performance parameters of the high-temperature alloy material of the self-locking nut (1) for shaft in the DEFORM-3D finite element simulation software to ensure that the model can reflect the plastic deformation characteristics of the high-temperature alloy.

3. The method for analyzing the influence of process variable parameters of inter-shaft self-locking nut closing process based on finite element method according to claim 1, characterized in that: Step S2 includes the following sub-steps: Step S2.1: Mesh the self-locking nut (1) for shafts, select the tetrahedral mesh type suitable for complex plastic deformation regions, and set the total number of meshes, the number of nodes, the mesh size ratio and the minimum element size to ensure that the mesh of the deformation region of the self-locking nut (1) for shafts has strong deformation adaptability; Step S2.2: Based on the interaction characteristics between the closing device (2) and the shaft self-locking nut (1) during the closing forming process, the shear friction model is selected as the friction model of the contact interface, and the friction coefficient of the contact interface is set. Step S2.3: Set boundary conditions and simulation control parameters, set the simulation environment temperature, constrain the radial displacement and axial movement degrees of freedom of the self-locking nut (1) to fix the position of the self-locking nut (1), set the lower mold base (5) to be fixed and the upper mold base (3) to move in the preset direction, and determine the displacement step length, total number of steps and the reference value of the movement speed of the upper mold base (3) in the simulation.

4. The method for analyzing the influence of process variable parameters of inter-shaft self-locking nut closing process based on finite element method according to claim 1, characterized in that: When the pressing speed of the closing die (4) is used as an independent variable in step S3 to carry out the closing forming simulation test and forming performance analysis, the following sub-steps are included: Step S3.1: Fix other process parameters, including the amount of closing, the pressure holding time, and the coefficient of friction between the closing device (2) and the shaft self-locking nut (1); Step S3.2: Set multiple different values ​​for the pressing speed of the closing mold (4) to form multiple simulation test schemes with only the pressing speed changing; Step S3.3: According to each group of simulation test schemes, configure the corresponding pressing speed parameters in DEFORM-3D finite element simulation software, start the shaft self-locking nut (1) closing and forming simulation process, and record the data information in the simulation process in real time; Step S3.4: Select multiple representative tracking points inside the thread teeth of the self-locking nut (1) at the bottom of the tooth profile, and collect the data on the change of equivalent stress of each tracking point with the forming stroke by point tracking method; Step S3.5: Using the cloud map function of DEFORM-3D finite element simulation software, generate equivalent stress distribution cloud maps and damage distribution cloud maps of the self-locking nut (1) for shaft under different pressing speeds; Step S3.6: Calculate the maximum damage value and maximum forming load of the shaft self-locking nut (1) in each group of simulation tests, and plot the relationship curves between pressing speed and equivalent stress, damage value and forming load; Step S3.7: Based on the collected data, generated cloud map and drawn curve, analyze and summarize the influence law of the pressing speed on the forming performance of the shaft self-locking nut (1).

5. The method for analyzing the influence of process variable parameters of inter-shaft self-locking nut closing process based on finite element method according to claim 1, characterized in that: When the closing forming simulation test and forming performance analysis are carried out in step S3 with the holding pressure time after forming as an independent variable, the following sub-steps are included: Step S3.8: Fix other process parameters, including the amount of closing, the pressing speed of the closing mold (4), and the coefficient of friction between the closing device (2) and the shaft self-locking nut (1); Step S3.9: Set multiple different values ​​for the holding time after molding, thereby forming multiple sets of simulation test schemes where only the holding time varies; Step S3.10: According to each group of simulation test schemes, configure the corresponding pressure holding time parameters in DEFORM-3D finite element simulation software, start the simulation process of the self-locking nut (1) of the shaft for forming, and record the data information in the simulation process in real time; Step S3.11: Using the cloud map function of DEFORM-3D finite element simulation software, generate equivalent stress distribution cloud maps and damage distribution cloud maps of the shaft self-locking nut (1) at the end of different pressure holding times; Step S3.12: Statistically analyze the maximum damage value and maximum forming load of the shaft self-locking nut (1) in each group of simulation tests, and plot the relationship curves between the holding time and the equivalent stress, damage value and forming load; Step S3.13: Based on the generated cloud map, statistical indicators and plotted curves, summarize the influence of pressure holding time on the forming performance of shaft self-locking nut (1).

6. The method for analyzing the influence of process variable parameters of inter-shaft self-locking nut closing process based on finite element method according to claim 1, characterized in that: When the friction coefficient between the closing device (2) and the shaft self-locking nut (1) is used as an independent variable in step S3 to carry out the closing forming simulation test and forming performance analysis, the following sub-steps are included: Step S3.14: Fix other process parameters, including the amount of closing, the pressing speed of the closing mold (4), and the holding time after forming; Step S3.15: Set multiple different value levels for the friction coefficient between the closing device (2) and the shaft self-locking nut (1) to form multiple sets of simulation test schemes with only the friction coefficient changing; Step S3.16: According to each group of simulation test schemes, configure the corresponding friction coefficient parameters in DEFORM-3D finite element simulation software, start the simulation process of self-locking nut (1) for shaft forming, and record the data information in the simulation process in real time; Step S3.17: Select multiple representative tracking points inside the thread teeth of the self-locking nut (1) at the bottom of the tooth profile, and collect the data on the change of equivalent stress of each tracking point with the forming stroke by point tracking method; Step S3.18: Using the cloud map function of DEFORM-3D finite element simulation software, generate equivalent stress distribution cloud maps and damage distribution cloud maps of the shaft self-locking nut (1) under different friction coefficients; Step S3.19: Statistically calculate the maximum damage value and maximum forming load of the shaft self-locking nut (1) in each group of simulation tests, and plot the relationship curves between the friction coefficient and the equivalent stress, damage value, and forming load; Step S3.20: Based on the collected data, generated cloud map and drawn curve, summarize the influence law of friction coefficient on the forming performance of shaft self-locking nut (1).

7. The method for analyzing the influence of process variable parameters of inter-shaft self-locking nut closing process based on finite element method according to claim 1, characterized in that: Step S4 includes the following sub-steps: Step S4.1: Based on the influence of each process parameter summarized in step S3, select the pressing speed range, holding time range and friction coefficient range that can reduce the equivalent stress of the shaft self-locking nut (1), reduce the damage value of the shaft self-locking nut (1), optimize the forming load of the shaft self-locking nut (1) and ensure the uniformity of deformation of the shaft self-locking nut (1); Step S4.2: Comprehensively weigh the forming quality of the self-locking nut (1) for shafts, including the deformation uniformity of the self-locking nut (1), the degree of damage of the self-locking nut (1), and the production efficiency, including the forming cycle of the self-locking nut (1), and determine the optimal combination of process parameters that balances performance and efficiency within the selected parameter range; Step S4.3: Output the process optimization scheme containing the optimal combination of process parameters, the principle of parameter adjustment (i.e., the adjustment direction when the parameters deviate from the optimal value) and the key points of forming quality control of the self-locking nut for shaft (1), so as to provide a theoretical basis for adjusting the closing forming process in the actual production of the self-locking nut for shaft (1).

8. The method for analyzing the influence of process variable parameters of inter-shaft self-locking nut closing process based on finite element method according to claim 2, characterized in that: Step S1.3 includes the following sub-steps: Step S1.4.1: Select a suitable constitutive model that can characterize the plastic stress characteristics of the high-temperature alloy constituting the shaft self-locking nut (1) under different strain, strain rate and temperature conditions, and adapt to the deformation mechanism of the high-temperature alloy. Step S1.4.2: Input the material property parameters of the high-temperature alloy, including static strength parameters, strain hardening parameters, strain rate sensitive parameters, temperature sensitive parameters, material melting point, room temperature, etc., into the constitutive model; Step S1.4.3: Enable the material volume compensation function in the DEFORM-3D finite element simulation software so that the DEFORM-3D finite element simulation software can dynamically adjust the overall volume of the shaft self-locking nut (1) according to the preset target volume during the mesh re-division process, thereby reducing the simulation error caused by mesh deformation.

9. The method for analyzing the influence of process variable parameters of inter-shaft self-locking nut closing process based on finite element method according to claim 3, characterized in that: Step S2.1 includes the following sub-steps: Step S2.1.1: Based on the structural dimensions and deformation complexity of the self-locking nut (1) for shafts, determine the total number of tetrahedral meshes and the number of nodes to ensure that the number of meshes can meet the calculation accuracy requirements of the simulation of the closing and forming of the self-locking nut (1) for shafts. Step S2.1.2: Set the mesh size ratio and minimum unit size so that the mesh unit size of the deformation area of ​​the self-locking nut (1) of the shaft is adapted to its plastic deformation requirements and is smaller than the mesh unit size of the non-deformation area. At the same time, make the mesh unit density of the deformation area higher than that of the non-deformation area to improve the mesh's ability to follow plastic deformation. Step S2.1.3: Start the mesh generation function of DEFORM-3D finite element simulation software to perform mesh generation on the self-locking nut (1) for shaft. After the mesh generation is completed, check the mesh quality and adjust and optimize the areas with unqualified mesh quality to ensure that the mesh can support the subsequent simulation calculation of the self-locking nut (1) for shaft closing.

10. The method for analyzing the influence of process variable parameters of inter-shaft self-locking nut closing process based on finite element method according to claim 3, characterized in that: Step S2.3 includes the following sub-steps: Step S2.3.1: Based on the actual processing environment of the self-locking nut (1) for shaft forming and the set simulation environment temperature, without setting additional heat transfer conditions for the self-locking nut (1) for shaft, match the actual room temperature forming conditions of the self-locking nut (1) for shaft. Step S2.3.2: Using the constraint function of DEFORM-3D finite element simulation software, the radial displacement of the self-locking nut (1) of the shaft is constrained by the relevant parameters of the positioning seat (6), and the axial movement degree of freedom of the self-locking nut (1) of the shaft is directly constrained to avoid positional displacement of the self-locking nut (1) of the shaft during the forming process. Step S2.3.3: In the simulation control module of DEFORM-3D finite element simulation software, the lower mold base (5) is set to remain fixed, and the upper mold base (3) drives the closing mold (4) to move along the axial direction. By setting the minimum displacement step and the total number of steps, the total moving distance of the upper mold base (3) is controlled to ensure that the movement of the upper mold base (3) meets the closing forming requirements of the shaft self-locking nut (1).

Images