A simulation method for installing, cutting and unscrewing a self-locking nut assembly without ear support

Abstract

The present invention relates to the technical field of fasteners, and specifically discloses a simulation method for the installation, cutting and unscrewing of an earless pallet self-locking nut assembly. The earless pallet self-locking nut fastening assembly is selected to obtain its structural parameters and material parameters; an unscrewing test of the earless pallet self-locking nut fastening assembly is carried out; a pre-simplified finite element model of the earless pallet self-locking nut fastening assembly is established; a finite element simulation calculation is carried out on the cold extrusion installation process; the cutting process of the inner wall of the earless pallet is simulated by the life and death unit technology; the friction coefficient is reversed according to the limit unscrewing data of the earless pallet self-locking nut fastening assembly; and a finite element simulation calculation of unscrewing of the earless pallet self-locking nut fastening assembly is carried out. The simulation of the installation, cutting and unscrewing processes of the earless pallet self-locking nut assembly can expose the structural design deficiencies of the earless pallet self-locking nut fastening assembly, save the test cost, and predict the unscrewing torque of earless pallet self-locking nut fastening assembly products of different sizes.

Description

Technical Field

[0001] The invention relates to a simulation method, in particular to a simulation method for the installation, cutting and unscrewing of a self-locking nut assembly without an ear support plate, and belongs to the technical field of fasteners. Background Art

[0002] With the development of the aerospace industry, fasteners, known as the "rice of industry", have received more and more attention from the country and enterprises. As a connection node for transmitting loads, its reliability is extremely important to the safe service of the entire structure and equipment. The aerospace industry has continuously increased its requirements for the long life and lightweight of fastening connection structures. The pallet nut is a very important type of fastener, often used in conjunction with self-locking nuts, and is suitable for narrow areas, closed structures, or areas that require frequent disassembly and assembly. Traditional pallet nuts are connected to the overall structure through rivets. Excessive rivet holes and rivets not only destroy the consistency of the original equipment structure, increase the risk of fatigue damage to the equipment, but also have a great impact on the weight of the equipment.

[0003] The new earless support plate generates plastic strain through cold extrusion, and is then squeezed onto the mounting plate. The installation method without rivets not only improves the installation efficiency, but also reduces the weight of the overall equipment. At the same time, the cold extrusion installation method can generate residual compressive stress in a certain area of ​​the hole wall radially, effectively delaying the initiation and expansion of fatigue cracks, and achieving the demand for long life.

[0004] Compared with the traditional rivet-assembled tray nuts, the earless tray self-locking nut fastening assembly is more prone to slip failure when subjected to torque load. At present, the research method of earless tray self-locking nut fastening assembly mainly relies on experimental research. By processing earless tray self-locking nut fastening assemblies of different sizes, the experiment is carried out to explore the influence of the size of the earless tray self-locking nut fastening assembly on its fastening performance. However, the experimental research method is relatively cumbersome, time-consuming and costly, and it cannot expose the structural design deficiencies of the earless tray self-locking nut fastening assembly. Therefore, it is necessary to carry out multi-process simulation of the earless tray self-locking nut fastening assembly to analyze its fastening performance. Summary of the invention

[0005] In view of the shortcomings of the existing methods that rely on experiments to determine the unscrewing force data, a small number of experiments are used to help determine the friction coefficient in the finite element simulation model, and an approximate linear model of the friction coefficient is established, covering the friction coefficient under all sizes, thereby improving the effectiveness and accuracy of the simulation of the finite element simulation model. Using the finite element method, a multi-process simulation method for the installation, cutting and unscrewing of earless tray self-locking nut assemblies is provided, which accurately and efficiently predicts the ultimate unscrewing force of earless tray self-locking nut fastening assemblies under various sizes, and provides a reliable basis for the selection of models and sizes of earless tray self-locking nut fastening assemblies in engineering. Compared with the existing methods that rely on experiments, the present invention can effectively reduce the test time and test costs, and achieve the purpose of quickly predicting the ultimate unscrewing force of the product.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A multi-process simulation method for installation, cutting and unscrewing of a self-locking nut assembly without an ear support plate, the simulation method comprising:

[0009] Step S1, selecting a self-locking nut fastening assembly without ear support plate, and obtaining its structural parameters and material parameters;

[0010] Step S2, conducting a twist-off test of the earless support plate self-locking nut fastening assembly;

[0011] Step S3, establishing a pre-simplified finite element model of the earless support plate self-locking nut fastening assembly;

[0012] Step S4, performing finite element simulation calculation on the cold extrusion installation process;

[0013] Step S5, applying the birth-death unit technology to simulate the inner wall cutting process of the earless support plate;

[0014] Step S6, reversely calculating the friction coefficient according to the limit unscrewing data of the earless support plate self-locking nut fastening assembly;

[0015] Step S7, performing finite element simulation calculation of unscrewing of the earless support plate self-locking nut fastening assembly;

[0016] Step S8, changing the size of the earless support plate self-locking nut fastening assembly model, and using the above steps to predict the ultimate unscrewing force of the earless support plate self-locking nut fastening assembly under different sizes.

[0017] Preferably, in step S1, the structural parameters of the earless support plate self-locking nut fastening assembly include geometric dimension information of the earless support plate, the mounting plate, the core rod and the bushing, and the material parameters include density, elastic modulus, Poisson's ratio, yield limit and hardening modulus.

[0018] Preferably, in step S2, a QBN200-L testing machine is used to perform a twisting-off force test on the earless support plate nut fastening assembly, and the limit twisting-off force data when the earless support plate self-locking nut fastening assembly fails due to slipping is recorded;

[0019] Preferably, in step S3, the earless support plate self-locking nut fastening assembly is CAD modeled using Solidworks modeling software, and the CAD model includes the earless support plate, the mounting plate and the mandrel. After the modeling is completed, the CAD model is imported into Abaqus finite element software, and finite element meshing is performed.

[0020] Preferably, in step S4, boundary conditions are applied to the earless support plate self-locking nut fastening assembly in Abaqus software, contact conditions are applied between the earless support plate and the mounting plate, and between the mandrel and the earless support plate, and a vertical downward displacement is applied to the mandrel to simulate the cold extrusion installation process of the earless support plate self-locking nut fastening assembly.

[0021] Preferably, in step S5, the birth-death unit technology is used for the inner wall of the earless support plate, that is, after cold extrusion, the inner wall area of ​​the earless support plate is deleted to simulate the cutting process.

[0022] Preferably, in step S6, the unscrewing force data measured in S2 is used in combination with simulation calculation to reversely deduce the friction coefficient between the earless support plate and the mounting plate. Using the existing friction coefficient data, a friction coefficient model covering all earless support plate self-locking nut fastening component sizes is established;

[0023] Preferably, in step S7, a torsional load is applied to the protrusion of the earless support plate, and the friction coefficient obtained by reverse deduction is input, and the torque-angle curve of the earless support plate self-locking nut fastening assembly is recorded to obtain the ultimate unscrewing torque of the earless support plate self-locking nut fastening assembly.

[0024] Preferably, in step S8, the size of the earless support plate self-locking nut fastening assembly is changed, and the simulation process of the cold extrusion, cutting and unscrewing processes is repeated to predict the ultimate unscrewing force values ​​of the earless support plate self-locking nut fastening assembly under different sizes.

[0025] Beneficial effects of the present invention:

[0026] By selecting a certain earless support plate self-locking nut fastening assembly to establish a corresponding finite element model, simplify the structures such as the slit bushing and the retaining spring in the finite element model; simulate the cold extrusion installation process of the earless support plate self-locking nut fastening assembly through the finite element software; use the life and death unit technology for the inner wall cutting process of the earless support plate to obtain the residual stress and strain results around the hole after cutting; use the method of combining experiments with simulations to reversely deduce the friction coefficient between the earless support plate and the mounting plate, apply a torsional load to the earless support plate, and obtain the limit unscrewing torque when it fails to unscrew; change the size of the earless support plate self-locking nut fastening assembly, and use the friction coefficient obtained by reverse deduction to predict the unscrewing force of the earless support plate self-locking nut fastening assembly under various models. The present invention simulates the installation, cutting and unscrewing processes of the earless support plate self-locking nut fastening assembly, which can expose the structural design deficiencies of the earless support plate self-locking nut fastening assembly, save the test cost, and predict the unscrewing torque of earless support plate self-locking nut fastening assembly products of different sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0028] Figure 1 It is a flow chart of a simulation method for installing, cutting and twisting off the earless support plate self-locking nut fastening assembly of the present invention.

[0029] Figure 2 It is a schematic diagram of cold extrusion installation of the earless support plate self-locking nut fastening assembly of the present invention.

[0030] Figure 3 It is a diagram of a twist-off force test device for a self-locking nut fastening assembly without an ear support plate according to the present invention.

[0031] Figure 4 It is a geometric model diagram of the earless support plate self-locking nut fastening assembly of the present invention.

[0032] Figure 5 It is a finite element mesh diagram of the earless support plate self-locking nut fastening assembly of the present invention.

[0033] Figure 6 It is a boundary condition diagram of the cold extrusion installation simulation of the present invention.

[0034] Figure 7 It is a setting diagram of the life and death unit for the cutting process simulation of the present invention.

[0035] Figure 8 It is a boundary condition diagram of the twist-off simulation of the present invention.

[0036] Fig. 9 It is a twist-off force curve diagram of the earless support plate nut fastening assembly under four different sizes of the present invention. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than 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.

[0038] See also Figure 1-9 As shown, a simulation method for installing, cutting and unscrewing a self-locking nut assembly without an ear support plate, the simulation method comprising:

[0039] Step S1, selecting a self-locking nut fastening assembly without ear support plate, and obtaining its structural parameters and material parameters;

[0040] Step S2, carrying out a torsion test of the earless support plate self-locking nut fastening assembly;

[0041] Step S3, establishing a pre-simplified finite element model of the earless support plate self-locking nut fastening assembly;

[0042] Step S4, performing finite element simulation calculation on the cold extrusion installation process;

[0043] Step S5, applying the birth-death unit technology to simulate the inner wall cutting process of the earless support plate;

[0044] Step S6, reversely calculating the friction coefficient according to the limit unscrewing data of the earless support plate self-locking nut fastening assembly;

[0045] Step S7, performing finite element simulation calculation of unscrewing of the earless support plate self-locking nut fastening assembly;

[0046] Step S8, changing the size of the earless support plate self-locking nut fastening assembly model, and using the above steps to predict the ultimate unscrewing force of the earless support plate self-locking nut fastening assembly under different sizes.

[0047] It should be noted that: the present invention selects a certain earless support plate self-locking nut fastening assembly, conducts a torsional unscrewing test on it, and records the value of the ultimate unscrewing force when unscrewing fails; establishes a corresponding finite element model, and simplifies the structures such as the slit bushing and the retaining spring in the finite element model; simulates the cold extrusion installation process of the earless support plate self-locking nut fastening assembly through finite element software; uses the life and death unit technology to the inner wall cutting process of the earless support plate to obtain the residual stress and strain results around the hole after cutting; uses the test combined with the simulation method to reversely deduce the friction coefficient between the earless support plate and the mounting plate, and constructs an approximate linear model of the friction coefficient to cover the friction coefficient between the earless support plate and the mounting plate under all sizes; applies a torsional load to the earless support plate to obtain its ultimate unscrewing torque when unscrewing fails; changes the size of the earless support plate self-locking nut fastening assembly, and predicts the ultimate unscrewing force of the earless support plate self-locking nut fastening assembly under different sizes. The present invention simulates the installation, cutting and unscrewing processes of the earless support plate self-locking nut assembly, which can expose the structural design deficiencies of the earless support plate self-locking nut fastening assembly, save test costs, and predict the unscrewing torque of earless support plate self-locking nut assembly products of different sizes, so as to determine whether the unscrewing force of the earless support plate self-locking nut fastening assembly under the size can meet the product requirement standard.

[0048] As a technical optimization solution of the present invention, in the step S1, the structural parameters of the earless support plate self-locking nut fastening assembly include geometric size information of the earless support plate, the mounting plate, the core rod and the bushing, and the material parameters include density, elastic modulus, Poisson's ratio, yield limit and hardening modulus;

[0049] As a technical optimization scheme of the present invention, in the step S2, the earless support plate nut fastening assembly is first installed by a cold extrusion process, the inner wall of the earless support plate is polished smooth by a cutting process, and then a QBN200-L testing machine is used to perform a twisting force test on the earless support plate nut fastening assembly, and the limit twisting force data when the earless support plate self-locking nut fastening assembly fails due to slipping is recorded;

[0050] As a technical optimization solution of the present invention, in the step S3, the earless support plate self-locking nut fastening assembly is CAD modeled by using Solidworks modeling software, and the CAD model includes the earless support plate, the mounting plate and the mandrel. After the modeling is completed, the CAD model is imported into the Abaqus finite element software, and the finite element mesh is divided, and the mesh of the contact area in the model is refined;

[0051] As a technical optimization solution of the present invention, in step S4, boundary conditions are applied to the earless support plate self-locking nut fastening assembly in Abaqus software, contact conditions are applied between the earless support plate and the mounting plate, and between the mandrel and the earless support plate, and a vertical downward displacement is applied to the mandrel to simulate the cold extrusion installation process of the earless support plate self-locking nut fastening assembly;

[0052] As a technical optimization solution of the present invention, in step S5, the inner wall of the earless support plate is subjected to the birth and death unit technology, that is, after cold extrusion, the inner wall area of ​​the earless support plate is deleted to simulate the cutting process, and the birth and death unit thickness should be consistent with the actual cutting thickness;

[0053] As a technical optimization solution of the present invention, in step S6, the unscrewing force data measured in S2 is used in combination with simulation calculation to reversely deduce the friction coefficient between the earless support plate and the mounting plate. Using the existing friction coefficient data, a friction coefficient model covering all earless support plate self-locking nut fastening component sizes is established;

[0054] As a technical optimization solution of the present invention, in step S7, a torsional load is applied to the protrusion of the earless support plate, and the friction coefficient obtained by reverse calculation is input, and the torque-angle curve of the earless support plate self-locking nut fastening assembly is recorded to obtain the limit unscrewing torque of the earless support plate self-locking nut fastening assembly;

[0055] As a technical optimization scheme of the present invention, in the step S8, the size of the earless support plate self-locking nut fastening assembly is changed, and the simulation process of the above-mentioned cold extrusion, cutting and unscrewing processes is repeated to predict the ultimate unscrewing force values ​​of the earless support plate self-locking nut fastening assembly under different sizes.

[0056] Example

[0057] The simulation method of the multiple processes of installation, cutting and unscrewing of the earless support plate self-locking nut assembly of the present invention is specifically described below with reference to an application example.

[0058] (1) Select a self-locking nut fastening assembly without ear support plate, and obtain the structural parameters and material parameters of the assembly. The structural parameters include the geometric size information of the earless support plate, the mounting plate, the core rod and the bushing. The core rod diameter is 7.36 mm; the bushing thickness is 0.17 mm; the inner wall diameter of the earless support plate is 7.40 mm, and the outer wall diameter is 10.29 mm; the hole diameter d and the plate thickness h of the mounting plate have certain range requirements, and the hole diameter d can vary from 10.30 mm to 10.36 mm, and the plate thickness h can vary from 1.96 mm to 3.20 mm. The material parameters of the self-locking nut fastening assembly without ear support plate include density, elastic modulus, Poisson's ratio, yield limit and hardening modulus.

[0059] (2) Before the twist-off test, the cold extrusion installation and cutting process of the earless support plate assembly is first performed. Figure 2As shown. After cold extrusion installation, the inner wall material of the earless support plate will undergo plastic flow at the slit of the bushing, forming a ridge on the inner wall, and the inner wall of the hole needs to be cut and polished to make it smooth. After cold extrusion and cutting are completed, the QBN200-L testing machine can be used to test the unscrewing force of the earless support plate nut fastening assembly, and record the ultimate unscrewing force data when the assembly fails due to slippage. Figure 3 Four groups of unscrewing force tests were carried out under four different sizes, including maximum aperture and maximum plate thickness, maximum aperture and minimum plate thickness, minimum aperture and maximum plate thickness, and minimum aperture and minimum plate thickness. Each group of tests had 5 specimens in total, and the unscrewing force data are shown in Table 1.

[0060] Table 1 Twist-off force test data

[0061]

[0062] (3) Use Solidworks to model the earless bracket self-locking nut fastening component, such as Figure 4 As shown, since the slit bushing and retaining spring have little effect on subsequent simulations, directly building a complete model will complicate meshing. Therefore, it is necessary to simplify the modeling of the earless support plate self-locking nut fastening assembly. The retaining spring is ignored during modeling, and the bushing thickness is considered within the core rod diameter. The main structural parts of the complete model are: earless support plate, mounting plate and core rod. After the modeling is completed, the model is imported into Abaqus, and the material parameters are entered. The earless support plate self-locking nut fastening assembly is meshed, and the C3D8R mesh unit is selected for the mesh. The mesh of the contact area between the earless support plate and the mounting plate is refined. The finite element mesh is as follows Figure 5 shown.

[0063] (4) Apply contact conditions and load constraint conditions for cold extrusion installation to the earless support plate self-locking nut fastening assembly, where the normal contact between the mandrel and the earless support plate is hard contact, the tangential contact is friction contact, and the friction coefficient is 0.1; the normal contact between the earless support plate and the mounting plate is hard contact, the tangential contact is friction contact, and the friction coefficient is determined by unscrewing test and simulation back-stepping. Apply boundary conditions to the established earless support plate self-locking nut fastening assembly, and apply a vertical downward displacement to the mandrel to control the cold extrusion process and simulate the installation process of the earless support plate self-locking nut fastening assembly. Boundary conditions such as Figure 6 shown.

[0064] (5) Figure 7 As shown in the figure, the birth and death unit method is used to simulate the inner wall cutting process of the earless support plate. After the cold extrusion is completed, the unit layer to be cut is directly killed. The thickness of the birth and death unit is consistent with the actual cutting thickness to ensure that the final hole diameter of the earless support plate before twisting off is consistent. The inner wall cutting thickness of this model of earless support plate is 0.2975mm.

[0065] (6) The friction coefficient between the earless support plate and the mounting plate is inferred by combining experiments with simulation. The specific inference method of the friction coefficient is as follows: 1. Using the four sets of unscrewing force test data measured in the pre-simulation test, different friction coefficients are set during the simulation and the unscrewing simulation process is repeated multiple times, so that the unscrewing force value calculated by the simulation is equal to the average value of each set of test data, and the friction coefficient between the mounting plate and the earless support plate under four different sizes is determined; 2. Using the friction coefficient value obtained by inference, an approximate linear model of the friction coefficient is established. The linear approximate model of the friction coefficient can cover the friction coefficient between the mounting plate and the earless support plate under all apertures and plate thicknesses, and then simulate the unscrewing force.

[0066] (7) Input the friction coefficient obtained by reverse calculation and simulate the unscrewing force of the earless support plate self-locking nut fastening assembly. The constraints are as follows: Figure 8 As shown in the figure, fixed constraints are applied to the two opposite sides of the mounting plate. When the torsion load is applied, the contact area between the earless support plate and the self-locking nut is coupled to the middle reference point RP-1, and the torsion is applied to the point RP-1 in the form of an angle. The unscrewing force curve of the earless support plate self-locking nut fastening assembly is output, as shown in Fig. 9 As shown, the ultimate unscrewing force data of the earless support plate self-locking nut fastening assembly when slipping failure occurs is recorded.

[0067] (8) By changing the size of the mounting plate in the earless support plate self-locking nut fastening assembly, the ultimate unscrewing force of the earless support plate self-locking nut fastening assembly of different sizes can be predicted using the approximate linear model of the friction coefficient. By comparing with the subsequent 4 groups of unscrewing force tests of earless support plate self-locking nut fastening assemblies of different sizes, as shown in Table 2, it is proved that this method can accurately predict the ultimate unscrewing force of earless support plate self-locking nut fastening assemblies of different sizes based on a small number of tests, thereby improving work efficiency and reducing test costs. At the same time, it also confirms the feasibility and accuracy of the multi-process simulation method of installation, cutting and unscrewing of the earless support plate self-locking nut assembly.

[0068] Table 2 Experimental simulation comparison

[0069]

[0070] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A simulation method for installing, cutting and unscrewing a self-locking nut assembly without ear support, characterized in that: The simulation method includes the following steps: Step S1, selecting a self-locking nut fastening assembly without ear support plate, and obtaining its structural parameters and material parameters; Step S2, conducting a twist-off test of the earless support plate self-locking nut fastening assembly; Step S3, establishing a pre-simplified finite element model of the earless support plate self-locking nut fastening assembly; Step S4, performing finite element simulation calculation on the cold extrusion installation process; Step S5, applying the birth-death unit technology to simulate the inner wall cutting process of the earless support plate; Step S6, reversely calculating the friction coefficient according to the limit unscrewing data of the earless support plate self-locking nut fastening assembly; Step S7, performing finite element simulation calculation of unscrewing of the earless support plate self-locking nut fastening assembly; Step S8, changing the model size of the earless support plate self-locking nut fastening assembly, and using steps S1-S7 to predict the ultimate unscrewing force of the earless support plate self-locking nut fastening assembly under different sizes.

2. The method for simulating installation, cutting and unscrewing of a self-locking nut assembly without ear support according to claim 1, characterized in that: In the step S1, the structural parameters of the earless support plate self-locking nut fastening assembly include geometric dimension information of the earless support plate, the mounting plate, the core rod and the bushing, and the material parameters include density, elastic modulus, Poisson's ratio, yield limit and hardening modulus.

3. The method for simulating installation, cutting and unscrewing of a self-locking nut assembly without ear support according to claim 1, characterized in that: In the step S2, a testing machine is used to perform a twisting-off force test on the earless support plate self-locking nut fastening assembly, and the ultimate twisting-off force data of the earless support plate self-locking nut fastening assembly with different sizes when slipping and failure occur are recorded.

4. The method for simulating installation, cutting and unscrewing of a self-locking nut assembly without ear support according to claim 1, characterized in that: In the step S3, the earless support plate self-locking nut fastening assembly is modeled using modeling software, and the model includes an earless support plate, a mounting plate and a core rod. After the modeling is completed, the model is imported into finite element software and finite element meshing is performed.

5. The method for simulating installation, cutting and unscrewing of a self-locking nut assembly without ear support plate according to claim 4, characterized in that: In step S4, boundary conditions are applied to the earless support plate self-locking nut fastening assembly in the finite element software, contact conditions are applied between the earless support plate and the mounting plate, and between the mandrel and the earless support plate, and a vertical downward displacement is applied to the mandrel to simulate the cold extrusion installation process of the earless support plate self-locking nut fastening assembly.

6. The method for simulating installation, cutting and unscrewing of a self-locking nut assembly without ear support according to claim 1, characterized in that: In step S5, the birth-death unit technology is used for the inner wall of the earless support plate, that is, after cold extrusion, the inner wall area of ​​the earless support plate is deleted to simulate the cutting process.

7. The method for simulating installation, cutting and unscrewing of a self-locking nut assembly without ear support plate according to claim 3, characterized in that: In step S6, the unscrewing force data measured in S2 is combined with simulation calculation to reversely infer the friction coefficient between the earless support plate and the mounting plate; using the existing friction coefficient data, a friction coefficient model covering all sizes of earless support plate self-locking nut fastening components is established.

8. The method for simulating installation, cutting and unscrewing of a self-locking nut assembly without ear support according to claim 1, characterized in that: In step S7, a torsional load is applied to the protrusion of the earless support plate, and the friction coefficient obtained by reverse calculation is input, and the torque-angle curve of the earless support plate self-locking nut fastening assembly is recorded to obtain the ultimate unscrewing torque of the earless support plate self-locking nut fastening assembly.

9. The method for simulating installation, cutting and unscrewing of a self-locking nut assembly without ear support according to claim 1, characterized in that: In step S8, the size of the earless support plate self-locking nut fastening assembly is changed, and the simulation process of the cold extrusion, cutting and unscrewing processes is repeated to predict the ultimate unscrewing force values ​​of the earless support plate self-locking nut fastening assembly under different sizes.

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