Logarithmic Asymmetric Modification Design Method for the Rollers of the Main Drive Bearing of a Large Roadheader

Abstract

The present invention belongs to the field of multi-parameter optimization and reliability design of main drive bearings for large tunneling machines, and discloses a logarithmic asymmetric profile modification design method for rollers of main drive bearings of large tunneling machines. The method establishes a contact mechanics model of the main drive bearing of the large tunneling machine under eccentric load based on the logarithmic asymmetric profile modification of the rollers, determines the load distribution of each row of rollers of the bearing, and then establishes a fatigue life calculation model of the bearing. By establishing an optimization model, the optimization design of the logarithmic asymmetric profile modification curve is carried out to obtain the optimal parameters under the action of eccentric load, so that the contact stress distribution along the roller length direction is uniform, and the excessive stress in the middle of the roller caused by excessive profile modification amount is avoided. This method can flexibly calculate the optimal logarithmic asymmetric profile modification curve of the roller under different working condition loads, so as to meet the requirements of high reliability and long service life of the bearing.

Description

Technical Field

[0001] The invention relates to the field of multi-parameter optimization and reliability design of a main drive bearing of a large-scale tunnel boring machine, and in particular to a logarithmic asymmetric shaping design method for a roller of a main drive bearing of a large-scale tunnel boring machine. Background Art

[0002] As an important component of a large-scale tunnel boring machine, the main drive bearing is large in size, needs to bear a large number of complex loads, is inconvenient to disassemble and has high maintenance costs. These characteristics require it to have high reliability and long service life. However, the load-bearing capacity and fatigue life of the main drive bearing of a large-scale tunnel boring machine depend not only on the performance of the bearing material, but also on the rationality of the bearing structure design. Since the straight generatrix roller inevitably has boundary stress concentration at both ends after being loaded, it causes contact fatigue of the bearing, which in turn affects the reliability of the bearing and greatly shortens the service life of the bearing. Therefore, the research on roller modification is crucial.

[0003] In the modification design of traditional bearing rollers, logarithmic modification is recognized as the best modification technology. Liu Liangyong et al. compared the contact stress distribution of rollers with different modification generatrixes, including full convex arc modification, intersecting arc modification, tangent arc modification and logarithmic modification. The modification amount was symmetrically distributed, increasing from the length center of the roller to both ends, thereby avoiding the stress concentration at both ends of the roller caused by the straight generatrix profile. At the same time, it can be seen from the comparison that the logarithmic modified roller has the highest utilization rate and can obtain the most ideal contact stress distribution. However, for the main drive bearings of large tunnel boring machines, the load conditions are complex. Due to various reasons, the rollers often need to bear large eccentric loads, such as: the overturning moment causes the contact between the roller and the raceway to deviate along the axis of the roller. In addition, the deformation of the raceway will also cause the eccentric load effect of the roller, making the contact stress distribution on the roller uneven, and the stress at one end of the roller increases sharply, shortening the service life of the bearing, and even causing the bearing to fail. In actual engineering applications, the main drive bearings of large tunnel boring machines usually adopt the method of increasing the logarithmic symmetrical shaping amount of the rollers to improve their unbalanced load effect. However, too large a shaping amount will cause the stress to be too concentrated in the middle of the roller, which will also make the contact stress on the roller unevenly distributed, greatly reducing the service life of the bearing. Therefore, the logarithmic symmetrical shaping of the rollers has certain limitations.

[0004] In summary, the current logarithmic symmetric roller shaping method cannot ensure that the main drive bearing of a large tunnel boring machine can improve the roller's off-center load effect while maintaining high reliability and long service life. At the same time, due to the different load conditions of bearings of different models, the contact stress distribution between the roller and the raceway is different, and the corresponding shaping curves are also different. Therefore, it is necessary to propose a logarithmic asymmetric shaping design method for the roller of the main drive bearing of a large tunnel boring machine, and determine different optimal shaping curves for different main drive bearing roller models to improve the roller's off-center load effect, thereby effectively improving the reliability and service life of the bearing. Summary of the invention

[0005] The present invention aims to solve the technical problems that the main drive bearings of large-scale tunnel boring machines are expensive to maintain, inconvenient to disassemble, and rollers are prone to overloading when subjected to complex loads. The present invention invents a logarithmic asymmetric shaping design method for rollers of the main drive bearings of large-scale tunnel boring machines. The method is applicable to main drive bearings of large-scale tunnel boring machines of different models. The method can avoid excessive stress in the middle of the rollers and effectively improve the contact fatigue between the rollers and the raceways caused by the overloading effect of the rollers, thereby achieving higher reliability and service life of the bearings.

[0006] The technical solution of the present invention:

[0007] A logarithmic asymmetric modification design method for the main drive bearing roller of a large-scale tunnel boring machine comprises the following steps:

[0008] Step 1: Establish a contact mechanics model of the main drive bearing of a large tunnel boring machine under eccentric load based on the asymmetric modification of roller logarithms;

[0009] The main drive bearing of a large tunnel boring machine adopts a three-row cylindrical roller structure, in which the load-bearing row is composed of two rows of rollers connected in series, mainly bearing the axial load F a The supporting row of rollers will only work under a larger overturning moment M, and the middle row of rollers will bear the radial load F. r The radial balance and axial balance of the bearing are independent of each other, and the axial load F a Much larger than the radial load F r Under this load condition, the contact stress between the load-bearing row rollers and the raceway is the largest, and the raceway is most susceptible to damage. Therefore, the middle row and supporting row rollers are still modified in a logarithmic symmetric manner, and only the load-bearing row rollers are modified in a logarithmic asymmetric manner.

[0010] Establish a logarithmic asymmetric shaping curve and set seven design parameters, k 1 , k 4 Indicates the maximum load factor of the roller, k 2 , k 5 Indicates the radius coefficient of the roller end, k3 , k 6 represents the proportion coefficient of the straight line part of the roller generatrix, c represents the offset from the center of the roller length, and the expression of the logarithmic asymmetric shaping curve is as follows;

[0011]

[0012] Among them, Q 1max is the maximum load of the bearing row rollers, expressed as;

[0013]

[0014] Among them, b 1 The half-width of contact between the roller and raceway in the row with the largest load, expressed as;

[0015]

[0016] Where E is the comprehensive elastic modulus, expressed as:

[0017]

[0018] Where, d 1m is the pitch diameter of the load-bearing roller row, Z 1 D is the number of load-bearing rollers. 1w is the diameter of the load-bearing row rollers, l 1we is the effective length of the load-bearing roller row, E 1 、E 2 are the elastic modulus of each row of rollers and raceways, ν 1 , ν 2 are the Poisson's ratios of each row of rollers and raceways, M is the overturning moment, and F a is the axial load;

[0019] The contact mechanics model of the main drive bearing of a large-scale tunnel boring machine under eccentric load based on the asymmetric modification of roller logarithms includes deformation coordination relationship and force balance equation.

[0020] According to Hertz contact theory, the relationship between contact load and contact elastic deformation is as follows:

[0021] Q ij =35948l iwe 8 / 9 δ ij 10 / 9

[0022] In the formula, Q ij is the contact load between the jth roller in the i-th row and the raceway, δ ij is the elastic contact deformation between the jth roller in the i-th row and the raceway, l iweis the effective length of the i-th row of rollers, where i=1, 2, 3, i=1 represents the first row of load-bearing row 1, i=2 represents the second row of intermediate row 2, and i=3 represents the third row of supporting row 3;

[0023] The deformation coordination relationship between the roller and the raceway under the bearing eccentric load is as follows:

[0024]

[0025] In the formula, δ a is the axial displacement of the bearing inner ring caused by the axial load, δ r is the radial displacement of the bearing inner ring caused by the radial load, δ iθj is the angular deformation of the jth roller in the i-th row caused by the overturning moment when it is tilted with the raceway, δ ixj is the deformation caused by the modification of the jth roller in the i-th row;

[0026] According to the balance relationship between contact stress and external load under the bearing eccentric load, the contact area between the roller and the raceway is sliced ​​so that it is divided into n parts along the length direction of the roller. s The basic equation for the contact between each row of rollers and the raceway is:

[0027]

[0028] Where M ij is the overturning moment of the jth roller in the i-th row, b ijk 、h ijk 、p ijk are the contact half-width, contact half-length and contact stress of the kth slice unit of the jth roller in the i-th row, respectively. ijk is the center coordinate of the kth slice unit of the jth roller in the i-th row, y ijc is the center coordinate of the jth roller in the i-th row;

[0029] The force balance equation of the bearing as a whole is:

[0030]

[0031] In the formula, F r is the radial load;

[0032] Solve the force balance equation of the bearing as a whole and obtain the load distribution of each row of rollers in the bearing;

[0033] Step 2: Establish a bearing fatigue life calculation model;

[0034] Rated load Q of the inner and outer rings of the i-th row of rollers icμ , Q icν Respectively expressed as:

[0035]

[0036] Among them, γ i is a dimensionless geometric parameter, expressed as:

[0037]

[0038] In the formula, B is the calculation constant, λ is the reduction coefficient considering the edge effect and the roller load center is not in the middle of the roller, and the value is between 0.6 and 0.8; D iw is the diameter of the roller in the i-th row, Z i is the number of rollers in the i-th row, d im is the pitch diameter of the i-th row of rollers, α i is the contact angle between the rollers in the i-th row and the raceway;

[0039] The inner ring rotates relative to the rated load direction, and the outer ring is stationary relative to the rated load direction. The equivalent load Q of the inner and outer rings of the i-th row of rollers ieμ , Q iev Respectively expressed as:

[0040]

[0041] Bearing fatigue life L h It is expressed as:

[0042]

[0043] Where n is the bearing speed;

[0044] Step 3: Establish an optimization model to optimize the design of the logarithmic asymmetric shaping curve

[0045] The optimization model includes design variables, objective functions, and constraints;

[0046] 3.1) Determine the design variables, including the maximum load factor k of the roller 1 , k 4 , the radius coefficient k of the roller end 2 , k 5 , the proportion coefficient k of the straight part of the roller generatrix 3 , k 6 , the offset c from the center of the roller length;

[0047] X=[k 1 ,k 2 ,k 3 ,k 4 ,k 5 ,k 6 ,c] T

[0048] The length of the straight part where the roller contacts the raceway should not be too long or too short. If it is too long, it will cause greater stress at the connection between the straight part and the curved part; if it is too short, it will cause greater stress in the middle of the roller. Both will reduce the bearing capacity. At the same time, the roller shaping amount should not be too large, otherwise it will increase the contact stress in the middle of the roller. Therefore, the design variables need to be determined within a reasonable range:

[0049] l b ≤X≤U b

[0050] In the formula, l b is the lower bound of the design variable, U b is the upper bound of the design variable;

[0051] 3.2) Determine the objective function. Bearing fatigue life is the most important indicator for its normal operation. Therefore, the maximum bearing fatigue life is selected as the objective function f(X):

[0052] max[f(X)]=max[L h ]

[0053] 3.3) Determine the constraints, and use the roller contact stress, contact stress variance, and elastic contact deformation at both ends of the roller as the constraints for the optimization design of the logarithmic asymmetric modification curve:

[0054] The contact stress p between the roller with the largest load in the load-carrying row and the raceway 1max The permissible contact stress [σ max ], so constraint 1 is set as:

[0055] g 1 (X) = p 1max -[σ max ]<0

[0056] The contact stress variance of the slice unit in the direction of the roller generatrix represents the distribution of the contact stress. The smaller the variance, the more uniform the contact stress distribution of the roller. However, if the variance is too small, the roller modification amount is too small, which can easily cause stress concentration at both ends of the roller. Therefore, the maximum contact stress variance of the roller is Cannot be too small, constraint 2 is set as:

[0057]

[0058] The variance of the contact stress on the roller with the largest load in the load-carrying row is expressed as:

[0059]

[0060] In the formula, is the average contact stress of the roller slice unit with the largest load in the load-bearing row;

[0061] In order to avoid the stress concentration problem at both ends of the roller, the elastic contact deformation of the slice units at both ends of the roller with the largest load is made smaller than the elastic approach of the roller and the raceway. Constraints 3 and 4 are:

[0062] g 3 (X) = δ 1max1 -δ<0

[0063]

[0064] In the formula, δ 1max1 , They are the first and nth rollers with the largest load in the bearing row respectively. s The elastic deformation of each slice unit;

[0065] Among them, the elastic approach between the roller and the raceway with the largest load in the bearing row is expressed as:

[0066]

[0067] A genetic algorithm is used for the optimization model to set the population size, maximum evolutionary generations, mutation probability and crossover probability, and perform optimization analysis to obtain the maximum fatigue life and thus the optimal model.

[0068] The method for solving the overall force balance equation of the bearing is the Newton-Raphson iteration method.

[0069] After a large number of experimental calculations, the calculation constant B=551.3.

[0070] The beneficial effect of the present invention is that asymmetric shaping is performed on the basis of the logarithmic curve of the roller, which changes the logarithmic symmetric shaping method of the traditional roller, so that under the action of the eccentric load, the contact stress is evenly distributed along the length direction of the roller, avoiding the problem of excessive stress in the middle of the roller. At the same time, the design parameters of the logarithmic asymmetric shaping curve of the roller can be flexibly adjusted according to the different load conditions of the main drive bearings of large-scale tunnel boring machines of different models to meet different working conditions, thereby achieving the ultimate goal of obtaining higher reliability and fatigue life for the main drive bearings of large-scale tunnel boring machines. The logarithmic asymmetric shaping design method for the rollers of the main drive bearings of large-scale tunnel boring machines proposed in the present invention can not only be used for the main drive bearings of large-scale tunnel boring machines of different models, but can also be applied to the roller shaping design of other bearings that bear eccentric loads, and has strong versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 It is a schematic diagram of the overall structure of a main drive bearing of a 6-meter tunnel boring machine of the present invention.

[0072] Figure 2The figure is a flow chart of a logarithmic asymmetric modification design method for the main drive bearing rollers of a large tunnel boring machine.

[0073] Figure 3 This is a diagram showing the fatigue life optimization results of a main drive bearing of a 6-meter tunnel boring machine according to the present invention.

[0074] In the figure: 1 the 1st row of load-bearing rollers, 2 the 2nd row of middle row of rollers, 3 the 3rd row of supporting row of rollers, 4 the bearing outer ring, 5 the bearing inner ring. DETAILED DESCRIPTION

[0075] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and technical solutions. The present invention is applicable to main drive bearings of large-scale tunnel boring machines of different models. In this embodiment, a logarithmic asymmetric shaping method for rollers of a main drive bearing of a 6-meter tunnel boring machine under its working load is designed. The main drive bearing of the 6-meter tunnel boring machine is as follows: Figure 1 The bearing comprises an outer ring 4, an inner ring 5, a first row of load-bearing rollers 1, a second row of middle row rollers 2 and a third row of supporting row rollers 3.

[0076] Firstly, a contact mechanics model of a 6-meter-type tunnel boring machine main drive bearing under eccentric load based on roller logarithmic asymmetric modification is established. The load distribution of each row of rollers in the bearing is obtained by the Newton-Raphson iteration method, and then the fatigue life calculation model of the bearing is established. Finally, an optimization model is established to optimize the logarithmic asymmetric modification curve. The specific design steps are as follows:

[0077] Step 1: Establish a contact mechanics model of a 6-meter-type tunnel boring machine main drive bearing under eccentric load based on the asymmetric modification of roller logarithms:

[0078] The overall structure of the bearing in this embodiment is as follows: Figure 1 As shown, its structural parameters and working parameters are shown in Table 1 and Table 2 respectively:

[0079] Table 1 Structural parameters of the main drive bearing of a 6-meter tunnel boring machine

[0080]

[0081] Table 2 Working parameters of main drive bearing of a 6-meter tunnel boring machine

[0082]

[0083]

[0084] Establish a logarithmic asymmetric shaping curve, considering seven design parameters, k 1 , k 4 Indicates the maximum load factor of the roller, k 2 , k5 Indicates the radius coefficient of the roller end, k 3 , k 6 represents the coefficient of the straight line portion of the roller generatrix, and c represents the offset from the center of the roller length. The expression is as follows:

[0085]

[0086] Where, the maximum load of the bearing row roller is The half-width of contact between the roller with the heaviest load in the load-carrying row and the raceway Comprehensive elastic modulus

[0087] According to Hertz contact theory, there is the following relationship between contact load and contact elastic deformation:

[0088] Q ij =35948l iwe 8 / 9 δ ij 10 / 9

[0089] In the formula, Q ij is the contact load between the jth roller in the i-th row and the raceway; δ ij is the elastic contact deformation between the jth roller in the i-th row and the raceway; wherein, i=1, 2, 3, i=1 represents the first load-bearing row, i=2 represents the second middle row, and i=3 represents the third support row.

[0090] The deformation coordination relationship between the roller and the raceway under the bearing eccentric load is as follows:

[0091]

[0092] In the formula, δ a is the axial displacement of the bearing inner ring caused by the axial load, δ r is the radial displacement of the bearing inner ring caused by the radial load; iθj is the angular deformation of the jth roller in the i-th row caused by the overturning moment when it is tilted with the raceway; δ ixj is the deformation caused by the modification of the jth roller in the i-th row.

[0093] The contact area between the roller and the raceway is divided into n s = 41 strip units, then the basic equations for the contact between each row of rollers and the raceway can be expressed as:

[0094]

[0095] Where M ij is the moment load on the jth roller in the i-th row; b ijk 、hijk 、p 0ijk are the contact half-width, contact half-length and maximum contact stress of the kth slice unit of the jth roller in the i-th row; y ijk is the center coordinate of the kth slice unit of the jth roller in the i-th row; y ijc is the center coordinate of the jth roller in the i-th row.

[0096] The force balance equation of the bearing as a whole is:

[0097]

[0098] The Newton-Raphson iteration method is used to solve the force balance equation of the bearing as a whole and obtain the load distribution of each row of rollers in the bearing.

[0099] Step 2: Establish a bearing fatigue life calculation model.

[0100] Rated load Q of the inner and outer rings of the i-th row of rollers icμ , Q icν Respectively expressed as:

[0101]

[0102] Where, the calculation constant B = 551.3; the reduction coefficient λ = 0.6; the dimensionless geometric parameter γ 1 =γ 3 =0,γ 2 =D 2w / d 2m . Get the rated load Q 1cμ =Q 1cν =311848N / 308733N, Q 2cμ =44903N,Q 2cν =45826N,Q 3cμ =Q 3cν =70027N.

[0103] The inner ring 5 of the bearing rotates relative to the rated load direction, while the outer ring 4 of the bearing is stationary relative to the rated load direction. Then the equivalent load Q of the inner and outer rings of the i-th row of rollers is ieμ , Q iev Respectively expressed as:

[0104]

[0105] Bearing fatigue life L h It is expressed as:

[0106]

[0107] Step 3: Establish an optimization model to optimize the design of the logarithmic asymmetric shaping curve.

[0108] Determine the design variables, including the maximum load factor k of the rollers 1 , k 4 , radius coefficient k of the roller end 2 , k 5 , the proportion coefficient k of the straight part of the roller generatrix 3 , k 6 , the offset c from the center of the roller length:

[0109] X=[k 1 ,k 2 ,k 3 ,k 4 ,k 5 ,k 6 ,c] T

[0110] The ranges of the design variables are set as follows:

[0111]

[0112] Determine the objective function. Bearing fatigue life is the most important indicator for its normal operation, so the maximum bearing fatigue life is selected as the objective function f(X):

[0113] max[f(X)]=max[L h ]

[0114] Determine the constraints, and use the roller contact stress, contact stress variance, and elastic contact deformation at both ends of the roller as the constraints for the design parameters of the logarithmic asymmetric modification curve:

[0115] Allowable contact stress [σ max ]=2800MPa, then the contact stress constraint condition 1 is:

[0116] g 1 (X) = p 1max -2800<0

[0117] Maximum contact stress variance of rollers Then the contact stress variance constraint 2 is:

[0118] g 2 (X) = s 1max 2 -2000<0

[0119] The variance of the contact stress on the roller with the largest load in the load-bearing row can be expressed as:

[0120]

[0121] In the formula, is the average contact stress of the roller slice unit with the largest load in the load-bearing row.

[0122] The elastic approach between the roller and raceway of the row with the largest load Then the elastic contact deformation constraints 3 and 4 of the slice units at both ends of the roller with the largest load are:

[0123] g 3 (X) = δ 1max1 -0.121<0

[0124] g 4 (X) = δ 1max41 -0.121<0

[0125] The genetic algorithm is used, the population size is set to 30, the maximum evolutionary generation is 50, the crossover probability is 0.9, and the mutation probability is 0.2. Through the optimization algorithm, the bearing fatigue life optimization results are obtained, such as Figure 3 The parameters of the obtained logarithmic asymmetric modification optimization design method and the original logarithmic symmetric modification scheme are compared and shown in Table 3.

[0126] Table 3 Parameter comparison between the logarithmic asymmetric shaping optimization scheme and the original logarithmic symmetric shaping scheme

[0127]

[0128] It can be seen from Table 3 that, compared with the original logarithmic symmetric shaping scheme, the fatigue life obtained by the logarithmic asymmetric shaping method of the present invention is increased by 39.16%. From the above analysis, it can be seen that the logarithmic asymmetric shaping design method of the present invention is feasible and effective for improving the unbalanced load effect, reducing the stress in the middle of the roller, and making the roller contact stress distribution uniform.

[0129] The above embodiments describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and that the present invention may be modified and improved without departing from the technical principles of the present invention, and these modifications and improvements fall within the scope of protection of the present invention.

Claims

1. A logarithmic asymmetric modification design method for the main drive bearing roller of a large tunnel boring machine. It is characterized in that The following steps are involved: Step 1: Establish a contact mechanics model of the main drive bearing of a large tunnel boring machine under eccentric load based on the asymmetric modification of roller logarithms; Establish a logarithmic asymmetric shaping curve and set seven design parameters, k 1 , k 4 Indicates the maximum load factor of the roller, k 2 , k 5 Indicates the radius coefficient of the roller end, k 3 , k 6 represents the proportion coefficient of the straight line part of the roller generatrix, c represents the offset from the center of the roller length, and the expression of the logarithmic asymmetric shaping curve is as follows; Among them, Q 1max is the maximum load of the bearing row rollers, expressed as; Among them, b 1 The half-width of contact between the roller and raceway in the row with the largest load, expressed as; Where E is the comprehensive elastic modulus, expressed as: Where, d 1m is the pitch diameter of the load-bearing roller row, Z 1 D is the number of load-bearing rollers. 1w is the diameter of the load-bearing row rollers, l 1we is the effective length of the load-bearing roller row, E 1 、E 2 are the elastic modulus of each row of rollers and raceways, ν 1 , ν 2 are the Poisson's ratios of each row of rollers and raceways, M is the overturning moment, and F a is the axial load; The contact mechanics model of the main drive bearing of a large-scale tunnel boring machine under eccentric load based on the asymmetric modification of roller logarithms includes deformation coordination relationship and force balance equation. According to Hertz contact theory, the relationship between contact load and contact elastic deformation is as follows: Q ij =35948l iwe 8 / 9 d ij 10 / 9 In the formula, Q ij is the contact load between the jth roller in the i-th row and the raceway, δ ij is the elastic contact deformation between the jth roller in the i-th row and the raceway, l iwe is the effective length of the i-th row of rollers, where i=1, 2, 3, i=1 represents the first load-bearing row (1), i=2 represents the second middle row (2), and i=3 represents the third support row (3); The deformation coordination relationship between the roller and the raceway under the bearing eccentric load is as follows: In the formula, δ a is the axial displacement of the bearing inner ring caused by the axial load, δ r is the radial displacement of the bearing inner ring caused by the radial load, δ iθj is the angular deformation of the jth roller in the i-th row caused by the overturning moment when it is tilted with the raceway, δ ixj is the deformation caused by the modification of the jth roller in the i-th row; According to the balance relationship between contact stress and external load under the bearing eccentric load, the contact area between the roller and the raceway is sliced ​​so that it is divided into n parts along the length direction of the roller. s The basic equation for the contact between each row of rollers and the raceway is: Where M ij is the overturning moment of the jth roller in the i-th row, b ijk 、h ijk 、p ijk are the contact half-width, contact half-length and contact stress of the kth slice unit of the jth roller in the i-th row, respectively. ijk is the center coordinate of the kth slice unit of the jth roller in the i-th row, y ijc is the center coordinate of the jth roller in the i-th row; The force balance equation of the bearing as a whole is: In the formula, F r is the radial load; Solve the force balance equation of the bearing as a whole and obtain the load distribution of each row of rollers in the bearing; Step 2: Establish a bearing fatigue life calculation model; Step 3: Establish an optimization model to optimize the design of the logarithmic asymmetric shaping curve.

2. According to claim 1, a logarithmic asymmetric modification design method for the main drive bearing roller of a large-scale tunnel boring machine, It is characterized in that Step 2 is as follows: Rated load Q of the inner and outer rings of the i-th row of rollers icμ , Q icν Respectively expressed as: Among them, γ i is a dimensionless geometric parameter, expressed as: In the formula, B is the calculation constant, λ is the reduction coefficient considering the edge effect and the roller load center is not in the middle of the roller, and the value is between 0.6 and 0.8; D iw is the diameter of the roller in the i-th row, Z i is the number of rollers in the i-th row, d im is the pitch diameter of the i-th row of rollers, α i is the contact angle between the rollers in the i-th row and the raceway; The inner ring rotates relative to the rated load direction, and the outer ring is stationary relative to the rated load direction. The equivalent load Q of the inner and outer rings of the i-th row of rollers ieμ , Q iev Respectively expressed as: Bearing fatigue life L h It is expressed as: Where n is the bearing speed.

3. The logarithmic asymmetric modification design method for the main drive bearing roller of a large-scale tunnel boring machine according to claim 1, It is characterized in that Step 3 is as follows: The optimization model includes design variables, objective functions, and constraints; 3.1) Determine the design variables, including the maximum load factor k of the roller 1 , k 4 , the radius coefficient k of the roller end 2 , k 5 , the proportion coefficient k of the straight part of the roller generatrix 3 , k 6 , the offset c from the center of the roller length; X=[k 1 ,k 2 ,k 3 ,k 4 ,k 5 ,k 6 ,c] T Determine the range of design variables; l b ≤X≤U b In the formula, l b is the lower bound of the design variable, U b is the upper bound of the design variable; 3.2) Select the maximum bearing fatigue life as the objective function f(X): max[f(X)]=max[L h ] 3.3) Determine the constraints, and use the roller contact stress, contact stress variance, and elastic contact deformation at both ends of the roller as the constraints for the optimization design of the logarithmic asymmetric modification curve: The contact stress p between the roller with the largest load in the load-carrying row and the raceway 1max The permissible contact stress [σ max ], so constraint 1 is set as: g 1 (X)(p 1max -[σ max ]90 The contact stress variance of the slice element in the roller generatrix direction represents the distribution of the contact stress, and constraint condition 2 is set as: The variance of the contact stress on the roller with the largest load in the load-carrying row is expressed as: In the formula, is the average contact stress of the roller slice unit with the largest load in the load-bearing row; In order to avoid the stress concentration problem at both ends of the roller, the elastic contact deformation of the slice units at both ends of the roller with the largest load is made smaller than the elastic approach of the roller and the raceway. Constraints 3 and 4 are: g 3 (X)=δ 1max1 -δ<0 In the formula, δ 1max1 , They are the first and nth rollers with the largest load in the bearing row respectively. s The elastic deformation of each slice unit; Among them, the elastic approach between the roller and the raceway with the largest load in the bearing row is expressed as: A genetic algorithm is used for the optimization model to set the population size, maximum evolutionary generations, mutation probability and crossover probability, and perform optimization analysis to obtain the maximum fatigue life and thus the optimal model.

4. The logarithmic asymmetric shaping design method for the main drive bearing roller of a large-scale tunnel boring machine according to claim 1, It is characterized in that The method for solving the overall force balance equation of the bearing is the Newton-Raphson iteration method.

5. The logarithmic asymmetric shaping design method for the main drive bearing roller of a large-scale tunnel boring machine according to claim 2, It is characterized in that The calculation constant B=551.3.

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