Method for determining residual stress under plastic deformation of turntable bearing

Abstract

The invention relates to a method for determining residual stress under plastic deformation of a turntable bearing, and belongs to the technical field of bearing performance research. According to the method, the relationship between the residual stress and the plastic deformation is established by utilizing the plastic deformation residual stress under the action of each load, and the plastic deformation of the turntable bearing under the actual working condition is obtained; and the residual stress of the turntable bearing under the actual working condition can be determined by substituting the plastic deformation under the actual working condition into the established relationship between the residual stress and the plastic deformation. Therefore, only the plastic deformation amount of the turntable bearing under the actual working condition needs to be obtained, the residual stress of the turntable bearing under the actual working condition can be determined without taking down the turntable bearing from actual running equipment, and normal running of the equipment is not affected by the detection mode.

Description

Technical Field

[0001] The invention relates to a method for determining residual stress of a turntable bearing under plastic deformation, and belongs to the technical field of bearing performance research. Background Art

[0002] In recent years, with the construction progress of wind power generation, shipbuilding, nuclear power engineering and transportation facilities, the research on heavy cranes has become a hot topic. The research and development of heavy cranes aims to improve their load-bearing capacity to reduce the restrictions on construction speed. As a key part of the crane's slewing mechanism, the slewing bearing has a unique structure and is subject to an extremely complex mechanical environment. When the crane is operating, the slewing bearing performs low-speed heavy-load slewing motion. Due to the unevenness of the main machine's stiffness, the contact stress at the contact point between a roller and the raceway inside the bearing may be too large, which will cause local material plastic deformation and put the bearing in an elastic-plastic non-Hertzian contact state. Considering that the plastic deformation of the rolling element under specific working conditions may cause the accumulation of residual stress, excessive residual stress may cause early failure of the component or even cracking. In addition, these residual stresses may also have a negative impact on the static load strength, fatigue resistance, dimensional stability and stress corrosion cracking of the material component. Therefore, accurate detection of residual stress is required. At present, the residual stress of the turntable bearing can only be accurately detected by using a tester, such as an X-ray diffractometer. Although accurate detection of residual stress is achieved, this method requires the turntable bearing to be removed from the crane and placed in the X-ray diffractometer, which is relatively complicated and affects the normal operation of the crane. Summary of the invention

[0003] The purpose of the present invention is to provide a method for determining residual stress of a turntable bearing under plastic deformation, so as to solve the problem that it is inconvenient to detect residual stress of a turntable bearing under plastic deformation.

[0004] In order to solve the above technical problems, the present invention provides a method for determining residual stress of a turntable bearing under plastic deformation, the method comprising the following steps:

[0005] 1) Obtain the plastic deformation of the slewing bearing under actual working conditions;

[0006] 2) Substituting the obtained plastic deformation of the slewing bearing under actual working conditions into the relationship between residual stress and plastic deformation, thereby determining the residual stress caused by the plastic deformation of the slewing bearing under actual working conditions;

[0007] The relationship between the residual stress and the plastic deformation is determined based on the plastic deformation of the slewing bearing under various loads and the residual stress of the slewing bearing under various loads.

[0008] Furthermore, the plastic deformation of the turntable bearing under each load is determined by at least one of finite element simulation, roller bearing elastic-plastic contact theory calculation, and plastic deformation measurement.

[0009] Furthermore, the calculation formula used to calculate the plastic deformation of the slewing bearing under various loads is:

[0010]

[0011] Among them, δ s is the plastic deformation; δ y F is the deformation of the material when it yields; c is the critical load at yield, Q is the normal contact load between the rolling element and the raceway in the slewing bearing, that is, the load borne by the slewing bearing; l is the effective length of the roller in the slewing bearing, and η is a coefficient related to the elastic constant E and Poisson's ratio v of the material of the two-body contact system of the slewing bearing.

[0012] Furthermore, when finite element simulation is used to determine the plastic deformation of the slewing bearing under various loads, a finite element model of the rolling element with the largest load is established. The finite element model adopts the elastic-plastic constitutive relationship as a bilinear isotropic hardening model, and the finite element model selects the lower surface of the outer ring of the slewing bearing as the fixed surface, constrains the x and z directions of all nodes along the line connecting the contact points between the roller and the inner and outer rings, and at the same time, it is necessary to constrain the x and z directions of all nodes on the inner ring surface. When the finite element model is loaded and simulated, the load is controlled to increase over time and unloaded after reaching the maximum value.

[0013] Furthermore, the residual stress of the turntable bearing under various loads is measured by an X-ray diffractometer.

[0014] Furthermore, when using an X-ray diffractometer to measure the residual stress of a turntable bearing under various loads, a static pressure test is first performed on the rolling element specimen of the turntable bearing, and then the rolling element specimen after the static pressure test is cleaned and measured using an X-ray diffractometer. The displacement of the diffraction peak is recorded, and the change in the lattice constant is calculated based on the diffraction pattern, and the residual stress is determined through the relationship between strain and stress.

[0015] Furthermore, the relationship between the residual stress and the plastic deformation is obtained by fitting the plastic deformation and residual stress of the turntable bearing under various loads.

[0016] Furthermore, the relationship between the fitted residual stress and the plastic deformation includes the relationship between the residual stress and the plastic deformation of the rolling element of the turntable bearing under the main thrust and the relationship between the residual stress and the plastic deformation of the rolling element of the turntable bearing under the reverse thrust. The relationship between the residual stress and the plastic deformation of the rolling element of the turntable bearing under the main thrust is a nonlinear relationship, and the relationship between the residual stress and the plastic deformation of the rolling element of the turntable bearing under the reverse thrust is a nonlinear relationship.

[0017] Furthermore, in the step 1), the plastic deformation of the slewing bearing under actual working conditions is determined by using one of finite element simulation of the slewing bearing and elastic-plastic contact theory calculation of the roller bearing; when using the elastic-plastic contact theory calculation of the roller bearing, the load borne by the slewing bearing is the load under the current working condition of the slewing bearing; when using finite element simulation to determine the plastic deformation of the slewing bearing, the control load is the load under the current working condition of the slewing bearing.

[0018] The beneficial effects of the present invention are as follows: the present invention uses the residual stress of the plastic deformation under each load to establish the relationship between the residual stress and the plastic deformation, obtains the plastic deformation of the turntable bearing under the actual working condition, and substitutes the plastic deformation under the actual working condition into the established relationship between the residual stress and the plastic deformation to determine the residual stress of the turntable bearing under the actual working condition. Therefore, the present invention only needs to obtain the plastic deformation of the turntable bearing under the actual working condition, and does not need to remove the turntable bearing from the equipment actually in operation to determine the residual stress of the turntable bearing under the actual working condition, and the detection method is used for detection, which does not affect the normal operation of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flow chart of a method for determining residual stress of a turntable bearing under plastic deformation of the present invention;

[0020] Figure 2 This is a schematic diagram of the structure and force of a slewing bearing for a crane in an embodiment of the present invention;

[0021] Figure 3 It is a schematic diagram of a bilinear isotropic hardening model used in finite element simulation of a slewing bearing in an embodiment of the present invention;

[0022] Figure 4 It is a schematic diagram of establishing a finite element model when performing finite element simulation on a slewing bearing in an embodiment of the present invention;

[0023] Figure 5 is a schematic diagram of boundary conditions of a finite element model established in an embodiment of the present invention;

[0024] Figure 6a Schematic diagram of the effect of the load under the main thrust on the plastic deformation of the bearing obtained in an embodiment of the present invention;

[0025] Figure 6b Schematic diagram of the effect of load on the plastic deformation of the bearing under reverse thrust obtained in an embodiment of the present invention;

[0026] Figure 7 1 is a schematic diagram comparing the experimental value, theoretical value and simulation value of the total plastic deformation under different loads under the main thrust obtained in the embodiment of the present invention;

[0027] Figure 8 1 is a schematic diagram comparing the experimental value, theoretical value and simulation value of the total plastic deformation under different loads under reverse thrust obtained in an embodiment of the present invention;

[0028] Figure 9a Schematic diagram of residual stress distribution of main thrust rolling element under 586KN obtained by finite element simulation in an embodiment of the present invention;

[0029] Figure 9b Schematic diagram of residual stress distribution of rolling element under 943KN reverse thrust force obtained by finite element simulation in an embodiment of the present invention;

[0030] Fig.10 1 is a schematic diagram comparing the test value and the simulation value of the residual stress under different loads under the main thrust in the embodiment of the present invention;

[0031] Fig.11 1 is a schematic diagram comparing the test value and the simulation value of the residual stress under different loads under reverse thrust in an embodiment of the present invention;

[0032] Fig.12 Schematic diagram of the relationship between the plastic deformation of the main thrust rolling element and the residual stress obtained in the embodiment of the present invention;

[0033] Fig.13 Schematic diagram of the relationship between the plastic deformation of the reverse thrust rolling element and the residual stress obtained in the embodiment of the present invention;

[0034] Fig.14 is a fitting curve of the plastic deformation and residual stress of the main thrust rolling element obtained in the embodiment of the present invention;

[0035] Fig.15 is a fitting curve of plastic deformation and residual stress of the reverse thrust rolling element obtained in an embodiment of the present invention;

[0036] Among them, 1 is the main thrust roller, 2 is the radial roller, 3 is the reverse thrust roller, 4 is the inner ring, and 5 is the outer ring. DETAILED DESCRIPTION

[0037] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0038] The present invention uses the residual stress of the plastic deformation under various loads to establish the relationship between the residual stress and the plastic deformation, obtains the plastic deformation of the turntable bearing under actual working conditions, and substitutes the plastic deformation under the actual working conditions into the established relationship between the residual stress and the plastic deformation to determine the residual stress of the turntable bearing under actual working conditions. The implementation process of the method is as follows: Figure 1 As shown, the detailed description is given below.

[0039] 1. Obtain the plastic deformation of the slewing bearing under various loads.

[0040] The present invention has found through research that the plastic deformation of the disc bearing under various loads can be determined by at least one of finite element simulation, roller bearing elastic-plastic contact theory calculation, and plastic deformation measurement. The determination process of each method is described below.

[0041] 1) Theoretical calculation of the plastic deformation of the slewing bearing under various loads

[0042] In order to ensure the accuracy of the theoretically calculated plastic deformation of the turntable bearing under different loads, it is particularly important to select a reasonable elastic-plastic mechanical model. After comprehensively considering the accuracy and calculation efficiency of various models, the present invention adopts a bilinear isotropic hardening model. This model can not only effectively calculate the total deformation of the bearing, but also accurately distinguish the elastic and plastic stages during the deformation process. Therefore, the overall strain δ of the bearing is decomposed into two parts:

[0043] δ=δ t +δ s (1)

[0044]

[0045] where δ t is the elastic deformation; δ s is the amount of plastic deformation, Q is the normal contact load between the rolling element and the raceway; l is the effective length of the roller, and η is a coefficient related to the elastic constant E and Poisson's ratio v of the material of the two-body contact system.

[0046] In practical engineering applications, the contact area of ​​a rolling bearing usually undergoes a relatively complex elastic-plastic deformation process. In view of this complexity, the present invention selects the Mises criterion as the criterion for evaluating whether the cylindrical roller contact part has reached the yield state. Specifically, the mathematical expression of the Mises yield criterion is as follows:

[0047]

[0048] Based on the Mises yield criterion, we know that:

[0049]

[0050] Where: s Indicates the critical stress value when the material yields; k st Indicates the shear yield strength of the material, k st =0.3. σ1, σ2 and σ3 are the first, second and third principal stresses.

[0051] By sorting out the above formula, we can get:

[0052]

[0053] where δ y F is the deformation of the material when it yields; c is the critical load at yield, and η is a coefficient related to the elastic constant E and Poisson's ratio v of the material of the two-body contact system:

[0054] Transforming formula (2) yields:

[0055]

[0056] Find δ for Q when δ=δ y The partial derivative of is:

[0057]

[0058] Combining the above formulas, the elastic-plastic loading curve equation is:

[0059]

[0060] Plastic deformation δ s The relationship with load Q is:

[0061]

[0062] make:

[0063]

[0064] Equation (10) describes the plastic deformation δ s The relationship between the normal load Q shows that under different loads, the total deformation δ of the roller and raceway contact is related to the load Q.

[0065]

[0066] Among them, k 1 , k 2 is a constant; δ t , δ sare the total elastic and plastic deformations of the contact area between the roller and the raceway, respectively. The corresponding plastic deformations can be calculated using formula (11). The calculation formulas for the plastic deformations corresponding to the main thrust and the reverse thrust are the same, which is formula (11).

[0067] 2) Finite element simulation to determine the plastic deformation of the slewing bearing under various loads

[0068] The present embodiment adopts a certain type of crane turntable bearing structure as shown in FIG. Figure 2 As shown, it includes a main thrust roller 1, a radial roller 2 and a reverse thrust roller 3. By calculating the load distribution of the turntable bearing for the crane under given working conditions, it can be known that the loads on the main thrust roller 1 and the reverse thrust roller 3 are significantly greater than the loads on the radial roller 2, and therefore can be ignored. In this embodiment, the contact stress and strain between the rolling element with the largest load and the inner raceway are analyzed. These areas are usually the most prone to failure. In order to further study the total plastic deformation of the contact position between the rolling element with the largest load and the inner and outer raceways when loading from 0 to the maximum load, this embodiment uses a finite element simulation method to distribute the plastic deformation of each component in the contact area under different loads. When the stress state of the material is complex, it is not reliable to judge whether the material has reached the yield condition only by one stress component. For plastic metal materials, the Von Mises criterion can better reflect the actual situation. According to this criterion, under complex stress states, when the equivalent stress reaches the yield limit σ of uniaxial tension, s When , the material enters the yield state and satisfies the formula:

[0069] The material model and parameters have a great influence on the accuracy of the simulation analysis results. In this embodiment, the elastic-plastic finite element analysis adopts a bilinear isotropic hardening model, such as Figure 3 As shown, the selected materials are all bearing steel GCr15, and their specific material characteristic parameters are shown in Table 1.

[0070] Table 1

[0071]

[0072] HyperMesh is used for pre-processing to establish the finite element model of the main thrust roller with the largest load (i.e., main thrust roller 1) (the finite element model of the reverse thrust roller can be established similarly). The finite element model of the main thrust roller with the largest load is as follows: Figure 4As shown in the figure, the main thrust roller 1 is between the inner ring 4 and the outer ring 5. The selected materials are all bearing steel GCr15, and its elastic-plastic constitutive relationship is a bilinear isotropic hardening model. The lower surface of the outer ring of the bearing is selected as the fixed surface, and the x and z directions of freedom of all nodes along the line connecting the roller and the inner and outer rings are constrained (since the y direction is the downward direction in the simulation software used, the x and z directions of freedom need to be constrained); at the same time, the x and z directions of freedom of all nodes on the inner ring surface need to be constrained. The model after constraint is as follows Figure 5 In order to analyze the relationship between the plastic deformation of each component in the contact area with the maximum-loaded rolling element under different loads, this embodiment defines that the load increases with time and unloads after reaching the maximum value.

[0073] By applying a load that increases over time and performing finite element simulation analysis, the influence of the plastic deformation of each component in the contact area of ​​the maximum-loaded rolling element under different loads is obtained as follows: Figure 6a and Figure 6b As shown in the figure, it can be found that: under the joint influence of material nonlinearity and contact nonlinearity, in the rolling element contact area under extreme load, the plastic deformation of each component shows a nonlinear growth trend with the increasing load intensity; when the initial load is light, the plastic deformation degree of the contact point of the inner ring raceway exceeds the corresponding deformation on the roller; with the continuous increase of the load level, the plastic deformation rate of the roller increases significantly, and the main thrust and reverse thrust are respectively when the load is greater than 300KN and 500KN. The plastic deformation degree of the roller successively exceeds the inner ring, and the main thrust and reverse thrust phenomena are particularly prominent at this time. In this process, the contact area between the outer ring raceway and the roller continues to maintain the lowest plastic deformation.

[0074] 3) Use measuring tools to determine the plastic deformation of the slewing bearing under various loads

[0075] Before the plastic deformation test, a static pressure test is performed. In this embodiment, a pressure tester is used to compress the two selected cylindrical rollers six times, and six groups of different loads are applied to perform a static pressure test. The static pressure test loads of the main thrust and reverse thrust rolling elements are shown in Tables 2 and 3, respectively.

[0076] Table 2

[0077]

[0078] Table 3

[0079]

[0080] After the static pressure test is completed, in order to avoid errors in the measurement process, this embodiment uses a bearing detector to measure the plastic deformation multiple times and records the data of the inner ring, outer ring and roller.

[0081] The measured results of plastic deformation were compared with theoretical calculations and finite element analysis (static load calculation results). The comparison results of the maximum rolling element under the main thrust and reverse thrust are shown in Table 4 and Table 5, respectively. The comparison of the total plastic deformation of the maximum rolling element under the main thrust and reverse thrust under different loads is shown in Table 4, Table 5, respectively. Figure 7 and Figure 8 shown.

[0082] Table 4

[0083]

[0084] Table 5

[0085]

[0086]

[0087] As can be seen from Table 4, when the main thrust bearing maximum load rolling element is loaded from 0 to the maximum load and then unloaded to 0, the theoretical value and simulation value of the bearing plastic deformation are basically consistent with the test results, with a maximum error of 10.95%. As can be seen from Table 5, when the reverse thrust bearing maximum load rolling element is loaded from 0 to 700KN, the comparison results of the theoretical value and the test value show good consistency, with a maximum error of 8.589%; however, when the load exceeds 700KN, the error between the theoretical value and the test value increases significantly. For example, under a load of 943KN, the error is as high as 62.26%, which shows that under ultra-large loads, the application of theoretical calculation methods to plastic deformation has certain limitations.

[0088] The results of the plastic deformation of the maximum rolling element under the main thrust and reverse thrust loads show that the change trends of the simulation value and the test value are basically consistent. For example, when the maximum rolling element under the main thrust load is in the range of 0 to 586KN, the maximum error between the simulation value and the test value is less than 10.95%; when the maximum rolling element under the reverse thrust load is in the range of 0 to 943KN, the maximum error between the simulation value and the test value does not exceed 7.142%. This shows that the finite element method is suitable for calculating the plastic deformation of each component in the contact area of ​​the maximum rolling element under various loads.

[0089] Through the above analysis, it can be known that the present invention can use at least one of the finite element analysis results, theoretical calculations and plastic deformation tests to obtain the plastic deformation of each component in the contact area of ​​the maximum loaded rolling element as needed. For example, if it is under an extremely large load, the finite element simulation method can be used, if it is under a normal load, the theoretical calculation method can be used, and if there is a high requirement for accuracy, the plastic deformation test method can be used.

[0090] 2. Determine the residual stress of the slewing bearing under various loads.

[0091] The residual stress of the slewing bearing under various loads can be obtained by finite element simulation of the slewing bearing and testing using a tester.

[0092] 1) Finite element simulation

[0093] The finite element simulation here can refer to the finite element simulation process in step 1. The residual stress of the slewing bearing under various loads can be obtained through finite element simulation.

[0094] 2) Test with a tester

[0095] Since the finite element simulation method has certain errors, and the residual stress in the material will cause the change of the crystal plane spacing, the present invention uses a single crystal X-ray diffractometer to detect the rolling element specimens after the static pressure test to obtain the actual residual stress inside the specimen. At the same time, in order to ensure the accuracy of the measurement, the specimens after the static pressure test are cleaned, measured using an X-ray diffractometer, the displacement of the diffraction peak is recorded, the diffraction pattern is analyzed, the change of the lattice constant is calculated, and the residual stress is determined through the relationship between strain and stress. The finite element analysis results of the residual stress of the main thrust and reverse thrust rolling elements are shown as follows: Figure 9a and Figure 9b The comparison results of the residual stress of the main thrust rolling element between the test and simulation are shown in Table 6 and Fig.10 The comparison results of the test and simulation of the residual stress of the reverse thrust rolling element are shown in Table 7 and Fig.11 shown.

[0096] Table 6

[0097]

[0098] Table 7

[0099]

[0100] It can be seen from Table 6 and Table 7 that the maximum residual stresses of the main thrust and reverse thrust rolling elements are 425.17Mpa and 628.31Mpa respectively, the maximum error between the simulation value and the test value of the main thrust rolling element is 7.34% and the maximum error between the simulation value and the test value of the reverse thrust rolling element is 8.75%. This shows that the finite element method is suitable for residual stress under certain loads.

[0101] 3. Establish the relationship between residual stress and plastic deformation.

[0102] Based on the plastic deformation and residual stress under different loads, the relationship between the residual stress and the plastic deformation is determined. The relationship between the plastic deformation and the residual stress of the main thrust rolling element obtained in this embodiment is as follows: Fig.12 As shown in the figure, the relationship between the plastic deformation of the reverse thrust rolling element and the residual stress is as follows: Fig.13 As shown, it can be seen that as the amount of plastic deformation increases, the residual stress also increases. The maximum residual stress of the main thrust rolling element is close to 430Mpa, and the maximum residual stress of the reverse thrust rolling element is close to 630Mpa, and the relationship between the two is nonlinear. In order to more accurately describe the relationship between residual stress and plastic deformation, the present invention obtains more test data and uses regression method for fitting to obtain the relationship between the plastic deformation of the main thrust rolling element and the residual stress, and the relationship between the plastic deformation of the reverse thrust rolling element and the residual stress, as shown respectively. Fig.14 and Fig.15 As shown. According to the fitting results, the correlation coefficients of the main thrust and the reverse thrust are 0.981 and 0.9833, respectively, indicating that there is a strong correlation between the plastic deformation and the residual stress. The fitting curve equations of the main thrust and the reverse thrust obtained in this embodiment are:

[0103] f(x)=1.845e+04x 2.768 (14)

[0104] f(x)=289.4-298.9×cos(5.863x)-46.21sin(5.863x) (15)

[0105] Where f(x) is the residual stress and x is the plastic deformation of the rolling element.

[0106] It can be seen that the relationship between the residual stress and the plastic deformation of the turntable bearing rolling element under the main thrust obtained in this embodiment is an exponential relationship, and the relationship between the residual stress and the plastic deformation of the turntable bearing rolling element under the reverse thrust is a trigonometric function relationship. As the sample data changes, the fitting relationship is not limited to the exponential relationship and the trigonometric function relationship, and may be other nonlinear relationships.

[0107] 4. Obtain the plastic deformation of the slewing bearing under actual working conditions and bring it into the relationship established in step 3 to obtain the residual stress under actual working conditions.

[0108] The plastic deformation of the slewing bearing under actual working conditions can be determined by using one of the finite element simulation of the slewing bearing and the elastic-plastic contact theory calculation of the roller bearing; when using the elastic-plastic contact theory calculation of the roller bearing, the load borne by the slewing bearing is set to be the load under the current working condition of the slewing bearing; when using the finite element simulation to determine the plastic deformation of the slewing bearing, the control load is the load under the current working condition of the slewing bearing. The theoretical calculation can refer to formula (11), and Q in it can be equal to the load value under the actual working condition; the finite element simulation can refer to the finite element simulation process in step 1, and it is only necessary to record the plastic deformation corresponding to the load value under the actual working condition.

[0109] Substituting the plastic deformation of the slewing bearing under the actual working condition into the relationship established in step 3, such as formula (14) or formula (15), the residual stress under the actual working condition can be obtained. The fitting relationship between the residual stress and the plastic deformation corresponding to different types of slewing bearings may be different, so it is necessary to establish the fitting relationship between the residual stress and the plastic deformation corresponding to different types of slewing bearings, so that the residual stress can be accurately measured only in the fitting relationship under the corresponding model.

[0110] Therefore, the present invention only needs to obtain the plastic deformation of the slewing bearing under actual working conditions, and the residual stress of the slewing bearing under actual working conditions can be determined without removing the slewing bearing from the actually running equipment. The detection method is used for detection, and the normal operation of the equipment is not affected.

Claims

1. A method for determining residual stress of a turntable bearing under plastic deformation, characterized in that: The method comprises the following steps: 1) Obtain the plastic deformation of the slewing bearing under actual working conditions; 2) Substituting the obtained plastic deformation of the slewing bearing under actual working conditions into the relationship between residual stress and plastic deformation, thereby determining the residual stress caused by the plastic deformation of the slewing bearing under actual working conditions; The relationship between the residual stress and the plastic deformation is determined based on the plastic deformation of the slewing bearing under various loads and the residual stress of the slewing bearing under various loads.

2. The method for determining residual stress of a turntable bearing under plastic deformation according to claim 1, characterized in that: The plastic deformation of the turntable bearing under each load is determined by at least one of finite element simulation, roller bearing elastic-plastic contact theory calculation, and plastic deformation measurement.

3. The method for determining residual stress of a turntable bearing under plastic deformation according to claim 2, characterized in that: When using the roller bearing elastic-plastic contact theory to calculate the plastic deformation of the slewing bearing under various loads, the calculation formula used is: Among them, δ s is the plastic deformation; δ y F is the deformation of the material when it yields; c is the critical load at yield, Q is the normal contact load between the rolling element and the raceway in the slewing bearing, that is, the load borne by the slewing bearing; l is the effective length of the roller in the slewing bearing, and η is a coefficient related to the elastic constant E and Poisson's ratio v of the material of the two-body contact system of the slewing bearing.

4. The method for determining residual stress of a turntable bearing under plastic deformation according to claim 2, characterized in that: When finite element simulation is used to determine the plastic deformation of the slewing bearing under various loads, a finite element model of the rolling element with the largest load is established. The finite element model adopts the elastoplastic constitutive relationship as a bilinear isotropic hardening model, and the finite element model selects the lower surface of the outer ring of the slewing bearing as the fixed surface, constrains the x and z directions of all nodes along the line connecting the contact points between the roller and the inner and outer rings, and at the same time, it is necessary to constrain the x and z directions of all nodes on the inner ring surface. When the finite element model is loaded and simulated, the load is controlled to increase over time and unloaded after reaching the maximum value.

5. The method for determining residual stress of a turntable bearing under plastic deformation according to claim 1, characterized in that: The residual stress of the slewing bearing under various loads is measured by X-ray diffractometer.

6. The method for determining residual stress of a turntable bearing under plastic deformation according to claim 5, characterized in that: When using an X-ray diffractometer to measure the residual stress of a turntable bearing under various loads, first perform a static pressure test on the rolling element specimen of the turntable bearing, then clean the rolling element specimen after the static pressure test, and use an X-ray diffractometer to measure it, record the displacement of the diffraction peak, calculate the change in the lattice constant based on the diffraction pattern, and determine the residual stress through the relationship between strain and stress.

7. The method for determining residual stress of a turntable bearing under plastic deformation according to claim 1, characterized in that: The relationship between the residual stress and the plastic deformation is obtained by fitting the plastic deformation and residual stress of the turntable bearing under various loads.

8. The method for determining residual stress of a turntable bearing under plastic deformation according to claim 7, characterized in that: The relationship between the residual stress and the plastic deformation obtained by fitting includes the relationship between the residual stress and the plastic deformation of the rolling element of the turntable bearing under the main thrust and the relationship between the residual stress and the plastic deformation of the rolling element of the turntable bearing under the reverse thrust. The relationship between the residual stress and the plastic deformation of the rolling element of the turntable bearing under the main thrust is a nonlinear relationship, and the relationship between the residual stress and the plastic deformation of the rolling element of the turntable bearing under the reverse thrust is a nonlinear relationship.

9. The method for determining residual stress of a turntable bearing under plastic deformation according to claim 1, characterized in that: In the step 1), the plastic deformation of the slewing bearing under actual working conditions is determined by using one of the finite element simulation of the slewing bearing and the elastic-plastic contact theory calculation of the roller bearing; when using the elastic-plastic contact theory calculation of the roller bearing, the load borne by the slewing bearing is the load under the current working condition of the slewing bearing; when using the finite element simulation to determine the plastic deformation of the slewing bearing, the control load is the load under the current working condition of the slewing bearing.

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