A method for measuring friction coefficient of bearing interference fit based on local twin model

Abstract

The present invention discloses a method for measuring the friction coefficient of bearing interference assembly based on a local twin model. Local twin simulation models are constructed for the bearing inner ring and the shaft respectively, modal tests are performed, and the local twin simulation models are corrected using the LSTM-based response surface method to obtain parameters such as the elastic modulus and Poisson's ratio of the bearing inner ring and the shaft. Press-fitting simulation is performed based on the corrected local twin simulation model, and a corresponding relationship table between the interference and the maximum press-fitting force under different friction coefficients is drawn. A preliminary interference is obtained based on the actual geometric dimensions of the shaft and the bearing inner ring, and the corrected interference is obtained by comprehensively considering the influence of the thermal deformation and the roughness flattening. An assembly press-fitting test of the shaft and the bearing inner ring is performed, the actual maximum press-fitting force during the press-fitting process is measured, and the corrected interference is searched in the relationship table to obtain the bearing interference assembly friction coefficient value. The present invention realizes accurate measurement of the interference assembly friction coefficient under the premise of considering the influence of thermal effects and roughness.

Description

Technical Field

[0001] The present invention relates to the field of bearing assembly parameter measurement, and in particular to a bearing interference assembly friction coefficient measurement method based on a local twin model. Background Art

[0002] Bearing interference fit is an effective method for load transfer, and the friction coefficient of the bearing interference fit is a key indicator of concern. The press force required for the bearing interference fit is closely related to the bearing interference and the friction coefficient. The press force required for the bearing interference fit is closely related to the surface roughness of the bearing and shaft, as well as thermal deformation caused by elevated temperatures. Therefore, comprehensively considering these influencing parameters to accurately measure the friction coefficient of the bearing interference fit is a question that requires research.

[0003] Research has shown that measuring the friction coefficient during interference fit between the bearing inner ring and the shaft is extremely difficult. Currently, both domestic and international friction coefficient measurements for interference fit are conducted experimentally, but these measurements often have large errors. With the continuous advancement of finite element simulation and bearing press-fit test measurement technology, it has become possible to accurately determine the friction coefficient for interference fit bearings by building a local twin model using finite element simulation and combining it with bearing press-fit test results. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a bearing interference fit friction coefficient measurement method based on a local twin model, which can accurately measure the interference fit friction coefficient while considering the influence of thermal effects and roughness, and has high accuracy, reliability and practicality.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for measuring the friction coefficient of bearing interference fit based on a local twin model comprises the following steps:

[0007] Step S1: construct local twin simulation models for the bearing inner ring and the shaft respectively and perform modal tests. The local twin simulation models of the bearing inner ring and the shaft are modified using a response surface method based on an LSTM long short-term memory network to obtain parameters of the bearing inner ring and the shaft, including the elastic modulus and Poisson's ratio of the bearing inner ring and the shaft.

[0008] Step S2: performing press-fitting simulation based on the local twin simulation model corrected in step S1, and drawing a corresponding relationship table between assembly interference and maximum press-fitting force under different friction coefficients;

[0009] Step S3: Calculate the preliminary assembly interference based on the actual geometric dimensions of the shaft and the bearing inner ring, and obtain the final corrected interference by comprehensively considering the effects of the shrink-fit deformation and the roughness flattening.

[0010] Step S4: Perform an assembly press-fit test on the shaft and the bearing inner ring, measure the maximum press-fitting force during the press-fitting process, and search the relationship table based on the final corrected interference fit obtained in step S3 to obtain the bearing interference fit friction coefficient value.

[0011] Preferably, the implementation process of step S1 is:

[0012] Step S101: Build local twin simulation models of the bearing inner ring and the shaft respectively:

[0013] The geometric models of the bearing inner ring and shaft were established using SolidWorks software. These geometric models were then meshed using Hypermesh software to obtain local twin simulation models of the bearing inner ring and shaft.

[0014] Step S102: Modify the local twin simulation model of the bearing inner ring and the shaft using the response surface method based on the LSTM long short-term memory network to obtain the parameters of the bearing inner ring and the shaft, including the elastic modulus and Poisson's ratio of the bearing inner ring and the shaft:

[0015] In terms of experiment, modal tests are performed on the bearing inner ring and the shaft to obtain the modal frequencies and vibration modes of the bearing inner ring and the shaft respectively. In terms of simulation, based on the local twin simulation model obtained in step S101, the vibration modes of each mode of the bearing inner ring and the shaft are calculated using Patran software. At the same time, N groups of elastic moduli and Poisson's ratios are changed for the local twin simulation models of the bearing inner ring and the shaft, which are respectively denoted as {E1, E2, ..., E N} and {π1,π2,...,π N}, and the obtained N groups of local twin simulation model modal frequencies are recorded as {f1,f2,...,f N};

[0016] The response surface is constructed using the LSTM long short-term memory network. The input of the LSTM long short-term memory network is the Poisson ratio {π1,π2,...,π N} and elastic modulus {E1,E2,...,E N}, the output is the modal frequency {f1,f2,...,f N According to the obtained response surface and the modal frequencies and vibration modes obtained from the experiment, the local twin simulation model obtained in step S101 is modified to obtain the true elastic modulus and Poisson's ratio of the bearing inner ring and the shaft.

[0017] Preferably, the implementation process of step S2 is:

[0018] Step S201: Perform press-fit simulation based on the local twin simulation model corrected in step S1:

[0019] Perform press-fit simulation on the modified local twin simulation model in step S1, preliminarily set the friction coefficient and assembly interference parameters, and obtain the stress cloud map and the curve of press-fit force versus press-fit displacement during the press-fit process of the bearing inner ring based on ABAQUS simulation software;

[0020] Step S202: Draw a table showing the corresponding relationship between the assembly interference parameters and the maximum press-fitting force under different friction coefficients:

[0021] The friction coefficient in step S201 is changed to obtain a corresponding relationship table between the assembly interference and the maximum press-fitting force under different friction coefficients.

[0022] Preferably, the implementation process of step S3 is:

[0023] Step S301: Based on the geometric dimensions of the shaft and the bearing inner ring, the initial assembly interference I is calculated as shown in formula (1):

[0024] I=Ds1-Dz2 (1)

[0025] Where Dz2 is the initial outer diameter of the shaft; Ds1 is the initial inner diameter of the bearing inner ring;

[0026] Step S302: Consider the influence of shrinkage deformation:

[0027] The reduction in inner ring assembly interference caused by temperature increase is shown in formula (2):

[0028] ΔI t =δ2ΔT2D n -δ s ΔT s D n (2)

[0029] Where: δ2 and δ s is the thermal expansion coefficient of the bearing inner ring and the shaft; ΔT2 and ΔT s The influence of the temperature increase of the bearing inner ring and the shaft on the bearing assembly interference is verified by ABAQUS finite element simulation considering the thermal effect; D n is the size of the mating surface between the bearing inner ring and the shaft after assembly; considering the influence of the thermal deformation, the corrected assembly interference I' is shown in formula (3):

[0030] I'=I-ΔI t (3)

[0031] Step S303: Consider the influence of the roughness flattening amount:

[0032] Since the mating surface between the bearing inner ring and the shaft has roughness, the influence of roughness is further considered to obtain the final corrected assembly interference I' rAs shown in formula (4):

[0033] I' r =I'+2(S p +S pm ) (4)

[0034] Where: S p S is the flattening depth of the shaft roughness during assembly; pm is the flattening depth of the roughness of the bearing inner ring during assembly; and:

[0035] S p =1.6R p (5)

[0036] S pm =1.6R pm (6)

[0037] Where: R p is the outer surface roughness of the shaft; R pm is the inner surface roughness of the bearing inner ring.

[0038] Preferably, the implementation process of step S4 is:

[0039] Step S401: Perform an assembly press-fit test on the shaft and the bearing inner ring, and measure the maximum press-fit force during the assembly press-fit test:

[0040] Use a press to press the inner ring of the bearing into the shaft at a constant speed. Measure the curve of the pressing force changing with the press displacement during the pressing process to obtain the maximum pressing force during the pressing process.

[0041] Step S402: Combine the final corrected interference I' r Look up the relationship table to get the friction coefficient value of the bearing interference fit:

[0042] Measure the roughness of the inner surface of the bearing inner ring and the outer surface of the shaft, the temperature change of the bearing inner ring and the shaft during the press-fit process, and the dimensions of the bearing inner ring and the shaft, and calculate the final corrected interference I' r ; According to the final correction interference I' r , and the maximum press-fitting force obtained in step S401, and search in the corresponding relationship table obtained in step S202 to obtain the bearing interference fit friction coefficient value.

[0043] The beneficial effects of the present invention are:

[0044] 1. The present invention fully utilizes the advantages of the local twin simulation model, reduces the parameter measurement cost, and improves the practicality and reliability of the interference fit friction coefficient measurement method;

[0045] 2. The present invention can achieve accurate measurement of the friction coefficient of interference fit while comprehensively considering the influence of thermal effect and roughness, thereby improving the accuracy of the measurement of the friction coefficient of interference fit. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a flow chart of a method for measuring the friction coefficient of bearing interference fit based on a local twin model provided in Example 1;

[0047] Figure 2 The cylindrical roller bearing used in Example 1, wherein a is a geometric structure diagram of the bearing, and b is an assembly structure diagram of the shaft and the bearing inner ring;

[0048] Figure 3 The geometric models of the shaft and the bearing inner ring provided in Example 1, wherein a is the geometric model of the shaft and b is the geometric model of the bearing inner ring;

[0049] Figure 4 The geometric dimensions of the shaft and bearing provided in Example 1, wherein a represents the geometric dimensions of the shaft, and b represents the geometric dimensions of the bearing inner ring;

[0050] Figure 5 The response surface constructed for the bearing inner ring provided in Example 1, wherein a is the first-order modal response surface, b is the second-order modal response surface of the shaft, and c is the third-order modal response surface of the shaft;

[0051] Figure 6 The finite element model for the bearing inner ring press-fit simulation provided in Example 1;

[0052] Figure 7 The finite element simulation based on ABAQUS and considering the thermal effect provided in Example 1, wherein a is a finite element simulation with a temperature increase of 40°C, b is a finite element simulation with a temperature increase of 50°C, and c is a finite element simulation with a temperature increase of 60°C;

[0053] Figure 8 The curve of the press-fitting force changing with the press-fitting displacement under different friction coefficients in the press-fitting process provided in Example 1;

[0054] Figure 9 The curve showing the change of the maximum pressing force with the interference during the pressing process provided in Example 1;

[0055] Figure 10 1 is a corresponding curve of interference fit and maximum press-fitting force under different friction conditions provided in Example 1. DETAILED DESCRIPTION

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0057] Example 1

[0058] See also Figures 1-10 This embodiment provides a method for measuring the friction coefficient of bearing interference fit based on a local twin model. The process of the method is as follows: Figure 1 As shown, this embodiment uses the assembly process of a certain type of cylindrical roller bearing as an example to verify the performance of the algorithm. Figure 2 The cylindrical roller bearing used in this embodiment. The strategy specifically includes the following steps:

[0059] Step S1: Build local twin simulation models for the bearing inner ring and shaft respectively and conduct modal tests. Use the LSTM-based response surface method to modify the finite element model to obtain parameters such as the elastic modulus and Poisson's ratio of the bearing inner ring and shaft:

[0060] Specifically, in this embodiment, step S1 includes:

[0061] Step S101: Build local twin simulation models of the bearing inner ring and the shaft respectively:

[0062] Based on Solidworks software, the geometric models of the shaft and the inner ring of the bearing are established (such as Figure 3 As shown in Figure 2), the geometric model of the bearing inner ring and the shaft is further meshed using Hypermesh software to obtain a local twin simulation model of the bearing inner ring and the shaft; the geometric dimensions of the bearing and the shaft are shown in Figure 2. Figure 4 As shown, Figure 4 The specific dimensions are shown in Table 1:

[0063] Table 1 Bearing and shaft geometric dimensions

[0064] parameter Size / mm parameter Size / mm L 16 Ls 26 Dz1 33.5 Ds1 39.992 Dz2 40.066 Ds2 47.1

[0065] Step S102: Perform a modal test and use the LSTM-based response surface method to modify the finite element model to obtain parameters such as the elastic modulus and Poisson's ratio of the bearing inner ring and the shaft:

[0066] In terms of experiment, modal tests are performed on the bearing inner ring and the shaft to obtain the modal frequencies and vibration modes. In terms of simulation, the finite element simulation model obtained in step S101 is used to calculate the modal vibration modes of the bearing inner ring and the shaft using Patran software. The modal frequencies of the bearing inner ring are shown in Table 2, and the modal frequencies of the shaft are shown in Table 3. At the same time, N groups of material parameters such as elastic modulus and Poisson's ratio are changed for the local twin simulation models of the bearing inner ring and the shaft, and are recorded as {E1, E2, ..., E N} and {π1,π2,...,π N}, and the modal frequencies of the N groups of local twin simulation models are recorded as {f1,f2,...,f N}.

[0067] Table 2 Modal frequencies of bearing inner ring

[0068] First-order modal frequency / Hz Second-order modal frequency / Hz Third-order modal frequency / Hz 4678 7590 13009

[0069] Table 3 Axis modal frequencies

[0070] First-order modal frequency / Hz Second-order modal frequency / Hz Third-order modal frequency / Hz 8775 5929 16438

[0071] Based on the obtained N groups of simulation modal data, the response surface is constructed using the LSTM algorithm (the response surface constructed for the bearing inner ring is as follows Figure 5 As shown), the input of the LSTM algorithm to construct the response surface is the Poisson ratio {π1,π2,...,π N} and elastic modulus {E1,E2,...,E N} and other material parameters, the output is the modal frequency {f1,f2,...,f N Using the response surface obtained by simulation and the modal results obtained by experiment, the finite element simulation model obtained in step S101 is modified to obtain parameters such as the true elastic modulus and Poisson's ratio of the bearing inner ring and the shaft;

[0072] Table 4 True elastic modulus and Poisson's ratio of bearing inner ring and shaft

[0073] Part Name Elastic modulus / Gpa Shear modulus / Gpa Poisson's ratio <![CDATA[Density / kg / m 3 <!-- 4 -->]]> axis 204 79 0.31 8240 Bearing inner ring 208 78 0.31 8100

[0074] Step S2: Perform press-fit simulation based on the modified ABAQUS finite element model and draw a corresponding relationship table between interference and maximum press-fit force under different friction coefficients:

[0075] Specifically, in this embodiment, step S2 includes:

[0076] Step S201: Perform bearing press-fit simulation based on the modified ABAQUS finite element model:

[0077] The steps for bearing press-fit simulation based on ABAQUS include creating component models, creating materials and cross-section properties, dividing the mesh, defining the assembly, setting the analysis steps, defining contacts, defining boundary conditions, and submitting the job. The details are as follows:

[0078] (1) Create component model

[0079] In step S101, the geometric models of the bearing inner ring and the shaft have been created and set as deformable bodies. At the same time, a press-fitting tool model is created according to the corresponding dimensions of the bearing inner ring and the shaft and set as a rigid body.

[0080] (2) Create material and section properties

[0081] Based on the geometric model of the bearing inner ring and the shaft obtained in (1) and the parameters such as the true elastic modulus and Poisson's ratio of the bearing inner ring and the shaft obtained in step S102, material and cross-section properties are created in the Property function module respectively; the press-fitting tool is a rigid body and no material properties are set;

[0082] (3) Grid division

[0083] Generate a hexahedral mesh for the bearing inner ring and shaft geometry, and refine the mesh near the contact area between the bearing inner ring and the shaft.

[0084] (4) Define the assembly

[0085] In the Assembly function module, assemble the bearing inner ring, shaft, press-fitting tool and other components according to the relative positions of the press-fitting test;

[0086] (5) Set the analysis step

[0087] Set the initial analysis step, Initial, to define the boundary conditions for the bearing inner ring and the shaft. Set the first analysis step, Contact, to move the bearing inner ring by 0.01 mm to establish a smooth contact relationship between the two rings and improve solution efficiency. Set the second analysis step, Press, to move the bearing inner ring along the axis so that it is completely pressed into the shaft. At the same time, set the output variables and historical output variables in this module. Select the required variables such as stress and strain in the output variables, and output the reaction force caused by the friction between the inner surface of the bearing inner ring and the outer surface of the shaft in the historical output variables.

[0088] (6) Define contact

[0089] Select the inner surface of the bearing inner ring as the master surface, the outer surface of the shaft as the slave surface, and set the inner surface of the bearing inner ring and the outer surface of the shaft as the contact pair. During the press-fit process, the contact position between the inner surface of the bearing inner ring and the outer surface of the shaft changes constantly, so the relative sliding of the contact surfaces is set to limited slip. At the same time, the contact properties of "hard contact" and Coulomb friction are adopted, and the friction coefficient range is set to 0.1-0.3.

[0090] (7) Define boundary conditions

[0091] In the initial analysis step, boundary conditions are applied to the shaft, constraining only the degrees of freedom along the axis and continuing until the second Press analysis step. Similarly, boundary conditions are applied to the inner ring of the bearing, constraining the remaining five degrees of freedom except the axis and continuing until the Press analysis step. The degrees of freedom along the axis are set to 0 in the initial analysis step, to 0.01 in the Contact analysis step, and to Ls in the Press analysis step to fully press the inner ring of the bearing into the shaft.

[0092] (7) Submitting homework

[0093] After completing the pre-processing of the finite element analysis according to the steps (1)-(6), enter the job function module and submit the analysis job. After the analysis is completed, enter the visualization module to view the analysis results (such as Figure 6 As shown in Figure 1, including the stress cloud diagram during the press-fitting process of the output bearing inner ring, a curve of press-fitting force versus displacement is obtained;

[0094] Step S202: Draw a table showing the corresponding relationship between interference and maximum press-fitting force under different friction coefficients:

[0095] Changing the friction coefficient in step S201 to obtain a corresponding relationship table between interference and maximum press-fitting force under different friction conditions;

[0096] Step S3: Calculate the preliminary interference based on the geometric dimensions of the shaft and the bearing inner ring, and obtain the corrected interference by comprehensively considering the effects of the shrink-fit deformation and the roughness flattening.

[0097] Specifically, in this embodiment, step S3 includes:

[0098] Step S301: Calculate the initial interference I based on the geometric dimensions of the shaft and the inner ring of the bearing as follows:

[0099] I=Ds1-Dz2 (1)

[0100] Wherein, Dz2 is the initial outer diameter of the shaft; Ds1 is the initial inner diameter of the bearing inner ring; the initial interference in Example 1 of the present invention is 39.992-40.066=0.074mm;

[0101] Step S302: Comprehensively consider the influence of shrink-fit deformation to obtain the corrected interference. The reduction in the inner ring interference caused by the temperature increase is:

[0102] ΔI t =δ2ΔT2D n -δ s ΔT s D n (2)

[0103] Where: δ2 and δ s is the thermal expansion coefficient of the bearing inner ring and the shaft, which is 0.0000125; ΔT2 and ΔT s is the temperature rise of the bearing inner ring and the shaft, which is set to 40°C. The effect of the temperature rise of the bearing inner ring and the bearing on the bearing assembly interference is verified by ABAQUS finite element simulation considering thermal effects, such as Figure 7 As shown; D n is the size of the mating surface between the bearing inner ring and the shaft after assembly; considering the influence of the shrinkage deformation, the corrected interference is obtained. The corrected interference I' is:

[0104] I'=I-ΔI t (3)

[0105] Step S303: comprehensively consider the influence of the roughness flattening amount to obtain the corrected interference:

[0106] The actual bearing inner ring and shaft mating surface are uneven. The wear of the contact surface after contact is twice the difference between the maximum roughness height and the average roughness height. At the same time, due to the extrusion effect, the rough surface will be flattened. Considering the influence of roughness, the final corrected interference I' is obtained. r The calculation formula is as follows:

[0107] I' r =I'+2(S p +S pm ) (4)

[0108] Where: S p S is the flattening depth of the shaft roughness during assembly; pm is the flattening depth of the roughness of the bearing inner ring during assembly; they satisfy:

[0109] S p =1.6R p (5)

[0110] S pm =1.6R pm (6)

[0111] Where: R p is the outer surface roughness of the shaft; Rpm is the inner surface roughness of the bearing inner ring;

[0112] Step S4: Perform an assembly press-fit test on the shaft and the inner ring of the bearing, measure the actual maximum press-fitting force during the press-fitting process, and find the corrected interference in the relationship table to obtain the bearing interference fit friction coefficient value:

[0113] Specifically, in this embodiment, step S4 includes:

[0114] Step S401, perform a press-fit test on the shaft and the inner ring of the bearing, and measure the actual maximum press-fitting force during the press-fitting process: use a press-fitting machine to press the inner ring of the bearing into the shaft at a constant speed, and measure the curve of the press-fitting force changing with the press-fitting displacement during the press-fitting process (the curves of the press-fitting force changing with different friction coefficients are shown in Figure 4). Figure 8 As shown), the actual maximum pressing force during the pressing process is obtained, as shown in Figure 9 As shown;

[0115] Step S402: Search the relationship table in combination with the corrected interference to obtain the bearing interference assembly friction coefficient value:

[0116] The initial interference obtained in step S203 is 0.074 mm; the temperature change of the bearing inner ring and the shaft during the press-fitting process is measured to obtain the corrected interference in this embodiment 1 of 0.074-0.004=0.07 mm; the roughness of the inner surface of the bearing inner ring and the outer surface of the shaft are measured to be 0.3 μm and 1.4 μm respectively, and the actual final corrected interference is calculated to be 0.07+2*(1.6*0.0003+1.6*0.0014)=0.007544 mm; according to the actual final corrected interference and the maximum press-fitting force obtained in step S401, the corresponding relationship table between the interference under different friction and the maximum press-fitting force obtained in step S202 is searched to obtain the bearing interference assembly friction coefficient value, such as Figure 10 As shown, the friction coefficient is 0.21.

[0117] Anything not described in detail in the present invention is well known to those skilled in the art.

[0118] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for measuring the friction coefficient of bearing interference fit based on a local twin model, characterized in that: The following steps are involved: Step S1: construct local twin simulation models for the bearing inner ring and the shaft respectively and perform modal tests. The local twin simulation models of the bearing inner ring and the shaft are modified using a response surface method based on an LSTM long short-term memory network to obtain parameters of the bearing inner ring and the shaft, including the elastic modulus and Poisson's ratio of the bearing inner ring and the shaft. The implementation process of step S1 is: Step S101: Build local twin simulation models of the bearing inner ring and the shaft respectively: The geometric models of the bearing inner ring and shaft were established using SolidWorks software. These geometric models were then meshed using Hypermesh software to obtain local twin simulation models of the bearing inner ring and shaft. Step S102: Modify the local twin simulation model of the bearing inner ring and the shaft using the response surface method based on the LSTM long short-term memory network to obtain the parameters of the bearing inner ring and the shaft, including the elastic modulus and Poisson's ratio of the bearing inner ring and the shaft: In terms of experiment, modal tests are performed on the bearing inner ring and the shaft to obtain the modal frequencies and vibration modes of the bearing inner ring and the shaft respectively. In terms of simulation, based on the local twin simulation model obtained in step S101, the vibration modes of each mode of the bearing inner ring and the shaft are calculated using Patran software. At the same time, N groups of elastic moduli and Poisson's ratios are changed for the local twin simulation models of the bearing inner ring and the shaft, which are respectively denoted as {E1, E2, ..., E N } and {π1,π2,...,π N }, and the obtained N groups of local twin simulation model modal frequencies are recorded as {f1,f2,...,f N }; The response surface is constructed using the LSTM long short-term memory network. The input of the LSTM long short-term memory network is the Poisson ratio {π1,π2,...,π N } and elastic modulus {E1,E2,...,E N }, the output is the modal frequency {f1,f2,...,f N According to the obtained response surface and the modal frequencies and vibration modes obtained from the experiment, the local twin simulation model obtained in step S101 is modified to obtain the true elastic modulus and Poisson's ratio of the bearing inner ring and the shaft; Step S2: performing press-fitting simulation based on the local twin simulation model corrected in step S1, and drawing a corresponding relationship table between assembly interference and maximum press-fitting force under different friction coefficients; Step S3: Calculate the preliminary assembly interference based on the actual geometric dimensions of the shaft and the bearing inner ring, and obtain the final corrected interference by comprehensively considering the effects of the shrink-fit deformation and the roughness flattening. Step S4: Perform an assembly press-fit test on the shaft and the bearing inner ring, measure the maximum press-fitting force during the press-fitting process, and search the relationship table based on the final corrected interference fit obtained in step S3 to obtain the bearing interference fit friction coefficient value.

2. The method for measuring the friction coefficient of bearing interference fit based on a local twin model according to claim 1, characterized in that: The implementation process of step S2 is: Step S201: Perform press-fit simulation based on the local twin simulation model corrected in step S1: Perform press-fit simulation on the modified local twin simulation model in step S1, preliminarily set the friction coefficient and assembly interference parameters, and obtain the stress cloud map and the curve of press-fit force versus press-fit displacement during the press-fit process of the bearing inner ring based on ABAQUS simulation software; Step S202: Draw a table showing the corresponding relationship between the assembly interference parameters and the maximum press-fitting force under different friction coefficients: The friction coefficient in step S201 is changed to obtain a corresponding relationship table between the assembly interference and the maximum press-fitting force under different friction coefficients.

3. The method for measuring the friction coefficient of bearing interference fit based on a local twin model according to claim 2, characterized in that: The implementation process of step S3 is: Step S301: Based on the geometric dimensions of the shaft and the inner ring of the bearing, the initial assembly interference I is obtained as shown in formula (1): I=Ds1-Dz2 (1) Where Dz2 is the initial outer diameter of the shaft; Ds1 is the initial inner diameter of the bearing inner ring; Step S302: Consider the influence of shrinkage deformation: The reduction in inner ring assembly interference caused by temperature increase is shown in formula (2): I t =δ2ΔT2D n -d s ΔT s D n (2) Where: δ2 and δ s is the thermal expansion coefficient of the bearing inner ring and the shaft; ΔT2 and ΔT s The influence of the temperature increase of the bearing inner ring and the shaft on the bearing assembly interference is verified by ABAQUS finite element simulation considering the thermal effect; D n is the size of the mating surface between the bearing inner ring and the shaft after assembly; considering the influence of the thermal deformation, the corrected assembly interference I' is shown in formula (3): I'=I-ΔI t (3) Step S303: Consider the influence of the roughness flattening amount: Since the mating surface between the bearing inner ring and the shaft has roughness, the influence of roughness is further considered to obtain the final corrected assembly interference I' r As shown in formula (4): I' r =I'+2(S p +S pm ) (4) Where: S p S is the flattening depth of the shaft roughness during assembly; pm is the flattening depth of the roughness of the bearing inner ring during assembly; and: With p =1.6R p (5) With pm =1.6R pm (6) Where: R p is the outer surface roughness of the shaft; R pm is the inner surface roughness of the bearing inner ring.

4. The method for measuring the friction coefficient of bearing interference fit based on a local twin model according to claim 3 is characterized in that: The implementation process of step S4 is: Step S401: Perform an assembly press-fit test on the shaft and the bearing inner ring, and measure the maximum press-fit force during the assembly press-fit test: Use a press to press the inner ring of the bearing into the shaft at a constant speed. Measure the curve of the pressing force changing with the press displacement during the pressing process to obtain the maximum pressing force during the pressing process. Step S402: Combine the final corrected interference I' r Look up the relationship table to get the friction coefficient value of the bearing interference fit: Measure the roughness of the inner surface of the bearing inner ring and the outer surface of the shaft, the temperature change of the bearing inner ring and the shaft during the press-fit process, and the dimensions of the bearing inner ring and the shaft, and calculate the final corrected interference I' r ; According to the final correction interference I' r , and the maximum press-fitting force obtained in step S401, and search in the corresponding relationship table obtained in step S202 to obtain the bearing interference fit friction coefficient value.

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