Method and system for predicting fatigue life of high-speed bearing in high-speed transmission system

Abstract

The invention discloses a method and a system for predicting the fatigue life of a high-speed bearing in a high-speed transmission system. The method comprises the following steps: extracting a load borne by a to-be-predicted bearing in the high-speed transmission system; constructing a bearing mechanical model based on the extracted load; extracting a contact stress time sequence of any position of the inner and outer raceways by utilizing a bearing mechanical model and combining a high-speed effect and a contact point position change time sequence; and on the basis of the extracted contact stress time sequence, traversing and solving all contact point damages of the inner and outer raceways to finish bearing life prediction. According to the method, the load borne by the bearing in the high-speed transmission system is accurately extracted, the bearing mechanical model is constructed based on the load, and finally the bearing service life prediction is completed by using the model, so that compared with a traditional macroscopic equivalent load method, the service life prediction is performed according to a bearing local contact stress time sequence, the prediction precision is remarkably improved; and a more scientific and reliable technical means is provided for service life evaluation and maintenance of high-speed bearings of high-speed transmission systems of various devices.

Description

Technical Field

[0001] The present invention relates to the field of bearing life prediction, and in particular to a method and system for predicting fatigue life of a high-speed bearing in a high-speed transmission system. Background Art

[0002] High-speed ball bearings are widely used in high-speed transmission systems of various modern equipment, such as ship transmission systems, spacecraft transmission systems, and electric drive systems of new energy vehicles. They are important components to ensure the reliable operation of high-speed shaft systems in high-speed transmission systems. Due to the traditional demand for stability, high-speed transmission systems often use helical gear transmissions. During the operation of high-speed transmission systems, the transmission torque and speed are often alternating rapidly. Under the action of the helical gear meshing force and the high-speed effect of the rolling elements, the working loads borne by the bearings and their internal load distribution are relatively harsh and complex. Therefore, accurate prediction of the life of high-speed bearings is the key to the high-reliability development process of high-speed transmission systems.

[0003] Contact fatigue is the main manifestation of failure during the operation of high-speed bearings. Accurate prediction of contact fatigue life is an important part of bearing service life assessment. For a long time, the bearing fatigue life prediction has generally been carried out using the empirical model established by Lundberg-Palmgren based on the maximum dynamic shear stress and Weibull life probability distribution (referred to as the LP model). However, since this method is based on the equivalent load of the bearing, it fails to consider the actual state and working conditions of the bearing, and there is a large error in the life assessment. In recent years, based on the LP model, researchers have corrected the LP model by considering factors such as the fatigue failure limit of the bearing material, the thickness of the lubricating oil film, and the correction factor of the fatigue life to improve the prediction accuracy. However, due to the limitations of test conditions, specific structural characteristics of the bearing, and materials of various bearing components, the corrected model has good results in specific cases, but has great limitations in terms of universality. In addition, the corrected model established by the constant load life test cannot accurately reflect the bearing life under complex dynamic load conditions. Summary of the invention

[0004] In order to solve the technical problems in the above background, the present invention provides a method for predicting fatigue life of high-speed bearings in a high-speed transmission system, the steps comprising:

[0005] Extract the load on the bearing to be predicted in the high-speed transmission system;

[0006] Based on the extracted loads, a bearing mechanics model is constructed;

[0007] By using the bearing mechanics model, combined with the high-speed effect and the contact point position change sequence, the contact stress sequence at any position of the inner and outer raceways is extracted;

[0008] Based on the extracted contact stress time series, the damage of all contact points on the inner and outer raceways is traversed and solved to complete the bearing life prediction.

[0009] Preferably, the expression of the load on the bearing includes:

[0010]

[0011] In the formula, subscripts A and B represent bearing A and bearing B at both ends of the shaft respectively; F r 、F t and F a Respectively represent the circumferential, radial and axial forces of the input shaft helical gear; F x 、F y and F z Represents forces in different directions; M x and M y Represents the overturning moment.

[0012] Preferably, the method for constructing the bearing mechanics model comprises: selecting the bearing type and configuration and extracting the load on the bearing; and then constructing the bearing mechanics model according to the size, direction and point of action of the extracted load.

[0013] Preferably, the bearing mechanics model constructed includes:

[0014]

[0015] In the formula, F x 、F y and F z Represents forces in different directions; M x and M y represents the overturning moment; ij and λ oj Both represent the bearing ball torque distribution coefficient; z represents the number of bearing rolling elements; α ij , α oj Respectively represent the actual contact angle between the bearing ball and the inner and outer raceways; F cj Indicates centrifugal force; M gj Indicates the gyroscopic torque; Q ij and Q oj Indicates the normal load of the bearing ball in contact with the inner and outer raceways respectively; D w Indicates the ball diameter; T iψ Indicates the friction force of the inner raceway; R i Indicates the rotation radius of the center of curvature of the inner raceway of the bearing; ψ j It represents the time sequence of the orientation of each contact of the j-th contact point on the inner raceway of the bearing; the subscript i represents the inner ring of the bearing, j represents the j-th contact point on the bearing raceway, and ψ represents the orientation angle of the contact point when it contacts.

[0016] Preferably, the method for predicting bearing life includes: based on the bearing mechanics model, combined with Hertz contact theory, obtaining stress distribution and deformation; based on the stress distribution and deformation at different times, obtaining stress time series; based on the stress time series, completing bearing life prediction.

[0017] The present invention also provides a high-speed bearing fatigue life prediction system in a high-speed transmission system, the system is used to implement the above method, including: an external load extraction module, an internal load construction module, a stress extraction module and a damage calculation module;

[0018] The external load extraction module is used to extract the load on the bearing to be predicted in the high-speed transmission system;

[0019] The internal load construction module is used to construct a bearing mechanics model based on the extracted loads;

[0020] The stress extraction module is used to extract the contact stress time series at any position of the inner and outer raceways by utilizing the bearing mechanics model, combining the high-speed effect and the contact point position change time series;

[0021] The damage calculation module is used to traverse and solve the damage of all contact points of the inner and outer raceways based on the extracted contact stress time series to complete the bearing life prediction.

[0022] Preferably, the expression of the load on the bearing includes:

[0023]

[0024] Wherein, subscripts A and B represent bearing A and bearing B respectively; F r 、F t and F a Respectively represent the circumferential, radial and axial forces of the input shaft helical gear; F x 、F y and F z Represents forces in different directions; M x and M y Represents the overturning moment.

[0025] Preferably, the workflow of the construction module includes: selecting the bearing type and configuration and extracting the load on the bearing; and then constructing the bearing mechanical model according to the size, direction and point of action of the extracted load.

[0026] Preferably, the bearing mechanics model constructed includes:

[0027]

[0028] In the formula, F x 、F y and Fz Represents forces in different directions; M x and M y represents the overturning moment; ij and λ oj Both represent the bearing ball torque distribution coefficient; z represents the number of bearing rolling elements; α ij , α oj Respectively represent the actual contact angle between the bearing ball and the inner and outer raceways; F cj Indicates centrifugal force; M gj Indicates the gyroscopic torque; Q ij and Q oj Indicates the normal load of the bearing ball in contact with the inner and outer raceways respectively; D w Indicates the ball diameter; T iψ Indicates the friction force of the inner raceway; R i Indicates the rotation radius of the center of curvature of the inner raceway of the bearing; ψ j It represents the time sequence of the positions of the jth contact point on the inner raceway of the bearing at each contact.

[0029] Preferably, the workflow of the damage calculation module includes: based on the bearing mechanics model, combined with Hertz contact theory, obtaining the stress distribution and deformation; based on the stress distribution and deformation at different times, obtaining the stress time series; based on the stress time series, completing the bearing life prediction.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention accurately extracts the loads on bearings in high-speed transmission systems, constructs a bearing mechanics model based on these loads, and finally uses the model to complete bearing life prediction. Compared with the traditional macro-equivalent load method, the life prediction is performed based on the local contact stress time series of the bearing, which significantly improves the prediction accuracy. This provides a more scientific and reliable technical means for life assessment and maintenance of high-speed bearings in high-speed transmission systems of various equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] Figure 1 A schematic diagram of a method flow of an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of a high-speed transmission system according to an embodiment of the present invention;

[0035] Figure 3 A schematic diagram of a service load spectrum of a high-speed transmission system according to an embodiment of the present invention;

[0036] Figure 4 A schematic diagram of boundary conditions of a high-speed transmission system according to an embodiment of the present invention;

[0037] Figure 5 Schematic diagram of the bearing coordinate system and inner ring force according to an embodiment of the present invention; wherein (a) represents the bearing coordinate system; (b) represents the bearing ball orientation coordinate system;

[0038] Figure 6 A schematic diagram of force balance of the input shaft of a transmission system according to an embodiment of the present invention;

[0039] Figure 7 Schematic diagram of the axial position of the contact point between the ball and the raceway according to an embodiment of the present invention;

[0040] Figure 8 The calculation process of the axial contact position between the bearing ball and the raceway according to the embodiment of the present invention;

[0041] Fig. 9 Schematic diagram of Hertz point contact according to an embodiment of the present invention;

[0042] Fig.10 A schematic diagram of bearing deformation coordination according to an embodiment of the present invention;

[0043] Fig.11 A schematic diagram of the force on a bearing ball according to an embodiment of the present invention;

[0044] Fig.12 This is a schematic diagram of initial value control of intermediate variable iteration according to an embodiment of the present invention;

[0045] Fig.13 The calculation process of the time sequence damage of the target contact points of the inner and outer raceways of the bearing according to the embodiment of the present invention;

[0046] Fig.14 A schematic diagram of the timing stress and damage of the contact point according to an embodiment of the present invention;

[0047] Fig.15 It is the service damage result of the high-speed ball bearing of the high-speed transmission system of the embodiment of the present invention. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 creative work are within the scope of protection of the present invention.

[0049] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] Embodiment 1

[0051] like Figure 1 FIG. 1 is a schematic diagram of the method flow of this embodiment, and the steps include:

[0052] S1. Extract the load on the bearing to be predicted in the high-speed transmission system.

[0053] The high-speed transmission system used in this embodiment is an electric drive system with a shaft structure of "motor shaft - spline - (reducer) input shaft - intermediate shaft - output shaft", such as Figure 2 As shown in the figure, the bearings A and B at both ends of the reducer input shaft are usually arranged as high-speed ball bearings. When the vehicle is driving, the torque is positive and the motor shaft rotates clockwise; when the vehicle is braking, the torque is negative and the motor shaft rotates counterclockwise. Figure 2 The global coordinate system shown.

[0054] The random road load of the electric drive system is characterized by the torque (N·m) transmitted by the motor shaft and the speed (r / min), such as Figure 3 As shown, the actual vehicle sampling frequency is 1 Hz.

[0055] During vehicle driving, the speed, torque and other service loads of the electric drive system show significant dynamic alternation and randomness. Figure 3 The load spectrum is counted for the joint distribution of speed and torque, and the results are as follows Figure 4 As shown, the cumulative frequency is higher in the ranges of torque -10 to 30 N·m, speed 0 to 800 r / min and torque -110 to -90 N·m, speed 800 to 6000 r / min.

[0056] Figure 4 In the figure, the torque-speed frequency distribution of the electric drive system is roughly in a "triangle" shape. The three boundary conditions are selected in turn: the highest speed under the maximum torque (condition 1), the maximum torque under the highest speed (condition 2), and the highest speed under the minimum torque (condition 3). The specific values ​​of the boundary conditions are shown in Table 1.

[0057] Table 1

[0058]

[0059] Establish a bearing coordinate system in the same direction as the global coordinate system at the center of the bearing, such as Figure 5 a; and the XOY plane coordinate system of the coordinate system is used as the bearing ball orientation coordinate system, as shown in Figure 5b. In the bearing ball azimuth coordinate system, the azimuth angle ψ j =0°, 360° / z,…, 360°(z-1) / z are typical contact positions in bearing mathematical modeling, where z represents the number of bearing rolling elements.

[0060] When the outer ring of the bearing is fixed and the inner ring is running at a speed (r / min), assuming that the inner ring is subjected to the following Figure 5 The force F in the direction indicated by a x 、F y and F z (N) and overturning moment M x and M y (N·mm) and produces a displacement δ in the same direction as the load x , δ y and δ z (mm) and angular displacement θ x and θ y (rad).

[0061] The simplified input shaft of the electric drive system is a uniform cross-section shaft, and the loads on bearings A and B are the support reaction forces applied by the input shaft to the bearings, such as Figure 6 shown.

[0062] Taking the input shaft and the coaxial helical gear as the object of force analysis, the force balance equation is:

[0063]

[0064] Wherein, subscripts A and B represent bearing A and bearing B respectively; F r 、F t and F a denote the circumferential, radial and axial forces (N) of the helical gear of the input shaft respectively. These loads and the auxiliary variable F A and F B The expression of is shown in Table 2.

[0065] Table 2

[0066]

[0067] In Table 2, α n , d and β represent the helical gear pressure angle (°), pitch diameter (mm) and helix angle (°) respectively. The working load on the bearing is taken as the quantity to be determined, and the flexural coordination equation that needs to be supplemented is:

[0068]

[0069] In the formula, bearings A and B are both fixed support structures at both ends; a and b represent the distance from the center of the input shaft helical gear to the center of bearings A and B respectively (mm); E represents the elastic modulus of the shaft (MPa); I represents the moment of inertia of the shaft section (mm 4) θ x ,θ y They represent the angular displacement in the x-direction and the angular displacement in the y-direction respectively;

[0070] S2. Based on the extracted loads, a bearing mechanical model is constructed.

[0071] The bearing type and configuration are selected and the load on the bearing is extracted; then, the bearing mechanical model is constructed according to the size, direction and action point of the extracted load.

[0072] In the bearing statics model, the contact angle α between the bearing ball and the inner and outer raceways is ij and α oj When the outer ring of the bearing is fixed and the inner ring is running at high speed, the centrifugal force and gyroscopic torque on the bearing ball make the inner and outer contact angles different. As the angular displacement of the inner ring of the bearing occurs, the actual contact points between the ball and the inner and outer raceways are different in the axial direction.

[0073] The acute angle between the contact normal line of the same ball and the inner and outer raceways at the jth contact position and the normal line of the inner raceway groove bottom is recorded as the relative contact angle. will change with the revolution of the bearing ball, then the axial arc length l from the jth contact position on the inner and outer raceways of the bearing to the center of the raceway groove bottom is ij and l oj (mm) can be expressed as and

[0074] like Figure 7 As shown in the figure, the outer ring of the bearing is fixed and the normal line of the outer raceway groove bottom remains unchanged. The angle between the normal line of the bottom of the raceway in the bearing and the vertical normal line can be expressed as θ x sinψ j -θ y cosψ j , according to the triangle exterior angle theorem, then:

[0075]

[0076] In the formula, f i and f o Respectively represent the curvature radius coefficient of the inner and outer raceways of the bearing; D w Indicates the ball diameter (mm).

[0077] When the target contact point on the inner and outer raceways of the bearing actually contacts, the position of the actual contact position in the bearing coordinate system is the axial position of the contact point. When the outer ring of the bearing is fixed and the inner ring is running, the time sequence of the position of a target contact point on the inner and outer raceways of the bearing at each contact is recorded as ψ j 、ψ0.

[0078] In the time sequence orientation process, the position of the bearing ball in contact with the inner and outer raceways is determined by the position interval Δψ(°) at each contact; the number of contacts is determined by the interval Δφ(°) of the inner ring rotation angle at each contact. The calculation process of the time sequence orientation process is as follows: Figure 8 shown.

[0079] Figure 8 In the equation, f represents the load spectrum sampling frequency (Hz); n k represents the inner ring speed of the bearing in the kth operating condition (r / min); assuming that the ball slip rate is 0, when a certain point on the inner and outer raceways of the bearing contacts each time, the expressions of Δψ and Δφ are shown in Table 3.

[0080] Table 3

[0081]

[0082] In Table 3, d p represents the pitch circle diameter of the bearing (mm); ξ represents the ball slip rate. To simplify the calculation, ξ=0.

[0083] The contact analysis between the ball and the raceway of a ball bearing is based on the rigid ring theory and the Hertz contact theory. After simplification, the normal load Q at the jth contact point of the inner and outer raceways of the bearing is j (N) and its elastic approximation δ j The relationship between (mm) is:

[0084]

[0085] Where, e, Γ(e) and Π(e) represent the eccentricity of the contact ellipse and the first and second complete elliptic integrals respectively; Σρ represents the curvature and function of the contact structure between the ball and the inner and outer raceways (1 / mm); It represents the equivalent elastic modulus (MPa) at the contact point, which is the equivalent of the Poisson's ratio v1 and v2 and the elastic modulus E1 and E2 (MPa) of the two contact surfaces.

[0086] When the motion trajectory of the bearing ball is stable and the long semi-axis of the contact ellipse at the contact point between the inner and outer raceways is always parallel to the Z axis of the bearing coordinate system, any point M in the contact ellipse is subjected to pulsating cyclic stress, such as Fig. 9 shown.

[0087] Its maximum contact stress q maxj The expression of (MPa) is:

[0088]

[0089] In the formula, a j , b j They represent the contact ellipse length and the minor semi-axis length (mm) of the j-th contact point.

[0090] When the ball bearing is stationary or running at low speed, the center point of the ball O b At the center point O of the inner and outer raceway curvature i With O o When the ball bearing runs at high speed, due to the centrifugal force and gyroscopic torque on the ball, the curvature centers of the inner and outer raceways of the bearing and the center of the ball are respectively at point O i ', O' o and O b ' position. The bearing deformation coordination diagram is as follows Fig.10 shown.

[0091] Fig.10 In the figure, α0 represents the radial clearance P of the bearing. d (mm) after the initial contact angle of the ball bearing (°), the expression is:

[0092]

[0093] according to Fig.10 The geometric relationship shown in the figure shows the actual contact angle α between the bearing ball and the inner and outer raceways. ij , α oj (°) and its elastic approximation δ ij , δ oj The expressions of (mm) are:

[0094]

[0095]

[0096] Where, X 1j and X 2j are intermediate variables, representing the axial and radial distances (mm) between the center of the bearing ball and the center of curvature of the outer raceway; A 1j and A 2j Respectively represent the axial and radial distances (mm) of the center of curvature of the inner raceway of the bearing relative to the center of curvature of the outer raceway.

[0097] When the outer ring of the bearing is fixed and subject to non-raceway control, the calculation method of the ball attitude angle (°) is applicable to high, medium and low speed conditions of the bearing, and its expression is:

[0098]

[0099] Where η = Q ij a ij Γ(e) / Q oj a oj ∏ o (e); γ o =γ'cosα oj ; γ i =γ'cosα ij ; γ'=D w / d p .

[0100] Take the bearing ball as the force analysis object, such as Fig.11 As shown, the ball is subjected to a centrifugal force F cj (N), gyroscopic moment M gj (N·mm) and the normal load Q in contact with the inner and outer raceways respectively ij , Q oj (N), satisfying the equilibrium equation:

[0101]

[0102] Taking the inner ring of the bearing as the force analysis object, its equilibrium equation is:

[0103]

[0104] In the formula, F x 、F y and F z Represents forces in different directions; M x and M y represents the overturning moment; ij and λ oj Both represent the bearing ball torque distribution coefficient; z represents the number of bearing rolling elements; α ij , α oj Respectively represent the actual contact angle between the bearing ball and the inner and outer raceways; F cj Indicates centrifugal force; M gj Indicates the gyroscopic torque; Q ij and Q oj Indicates the normal load of the bearing ball in contact with the inner and outer raceways respectively; D w Indicates the ball diameter; T iψ Indicates the friction force of the inner raceway; R i Indicates the rotation radius of the center of curvature of the inner raceway of the bearing; ψ jIt represents the time sequence of the orientation of each contact of the j-th contact point on the inner raceway of the bearing; the subscript i represents the inner ring of the bearing, j represents the j-th contact point on the bearing raceway, and ψ represents the orientation angle of the contact point when it contacts.

[0105] After the model is built, it is constrained and solved.

[0106] The high-speed effect of the ball bearing will cause the contact angle between the ball and the inner and outer raceways to increase and decrease respectively, until the ball is separated from the inner raceway. From the geometric meaning of formula (9), it can be seen that the separation and contact between a certain ball and the inner raceway correspond to the intermediate variable X 1j and X 2j The value of Fig.12 The circle O shown i ' or O i ” inside and outside.

[0107] When the ball is in good contact with the inner raceway, the intermediate variable X 1j and X 2j The iteration direction is downward and is on the line segment Above and close to the two circles, such as Fig.12 As shown, then X 1j and X 2j The initial value of the iteration can be constrained to the path shown in Table 4.

[0108] Table 4

[0109]

[0110] Substitute the equations (13) of bearings A and B into the shaft system equations (1) and (2) as the overall equation system, and the variable to be solved is S = (δ xA(B) ,δ yA(B) ,δ zA(B) ,θ xA(B) ,θ yA(B) ); Equation (11) and equation group (12) of bearings A and B are respectively regarded as local equation groups, and the variables to be solved are s=(X 1jA(B) ,X 2jA(B) ,β jA(B) ). The model of this embodiment is solved by programming using the Newton-Raphson method in conjunction with the cyclic iteration method.

[0111] Among them, the initial values ​​of the iteration of the global and local equations are controlled by one-dimensional search, and positive and negative initial values ​​are adopted under positive and negative torque conditions respectively; X1' jA(B) and X' 2jA(B) Represents the intermediate variable X 1jA(B) and X 2jA(B) The initial value of the iteration of the equation system after updating once is X' 2jA(B) =X2jA(B) +0.02.

[0112] S3. Using the bearing mechanics model, combined with the high-speed effect and the contact point position change sequence, the contact stress sequence at any position of the inner and outer raceways is extracted.

[0113] 21 and 360 target contact points are uniformly selected along the axial and circumferential directions on the inner and outer raceways of the bearing respectively; the damage history solution process of the target contact point is obtained according to the axial position of the actual contact point obtained by model analysis as follows: Fig.13 shown.

[0114] Under the boundary condition of working condition 1, the target contact point at (0mm, 147°) on the inner raceway of bearing A has the greatest damage. Fig. 9 In the Hertz point contact schematic diagram, the pulsating cyclic stress at any point in the contact ellipse is the cyclic stress from zero to the maximum contact stress, and is a compressive stress with a stress ratio of 0, all of which are positive. Its time series stress and damage history are as follows Fig.14 shown.

[0115] S4. Based on the extracted contact stress time series, traverse and solve all contact point damages of the inner and outer raceways to complete the bearing life prediction.

[0116] Based on the constructed bearing mechanics model and combined with Hertz contact theory, the stress distribution and deformation are obtained; based on the stress distribution and deformation at different times, the stress time series is obtained; based on the stress time series, the bearing life prediction is completed.

[0117] The above-mentioned Hertz contact theory mainly uses the contact load, the equivalent elastic modulus at the contact point between the bearing ball and the raceway, the eccentricity of the contact ellipse, and the first and second complete elliptic integrals to calculate the major semi-axis length, minor semi-axis length and contact deformation of the contact ellipse to characterize the point contact area characteristics between the bearing ball and the raceway; then, the maximum contact stress is calculated using the contact ellipse length, minor semi-axis length and contact load; finally, the contact stress of each point in the contact area is calculated.

[0118] Specifically, the service process of high-speed ball bearings in electric drive systems is a typical fatigue damage accumulation process. Figure 3 The torque-speed load spectrum of the electric drive system is shown, and the bearing contact stress and damage are calculated at each moment to obtain the cumulative damage distribution of the raceway contact points of bearings A and B after 32 hours of service.

[0119] Under the positive torque condition, the contact stress distribution of the outer raceway of bearing A is concentrated at 0° along the circumferential direction and at 0mm along the axial direction; the contact stress distribution of the outer raceway of bearing B is concentrated at 350° along the circumferential direction and at 3mm along the axial direction. Under the negative torque condition, the contact stress distribution of the outer raceway of bearing A is concentrated at 225 along the circumferential direction and at -3mm along the axial direction; the contact stress distribution of the outer raceway of bearing B is concentrated at 0° along the circumferential direction and at 0mm along the axial direction. It can be seen from the cumulative damage values ​​that the positive torque condition contributes more to the damage of bearing B and the negative torque condition contributes more to the damage of bearing A.

[0120] Solve the torque-speed load spectrum of the electric drive system. According to formula (14), the damage of each target contact point is equivalent to the damage of the inner and outer rings of the bearing. Then, according to formula (15), the damage of the inner and outer rings of the bearing is equivalent to the overall damage of the bearing, as follows: Fig.15 The service damage is from small to large in order of the outer ring, inner ring and the whole bearing, which is consistent with the fluctuation trend of the speed in the service load spectrum.

[0121]

[0122] Among them, D ik , D ok and D k Respectively represent the damage of the inner and outer rings of the bearing and the entire bearing; n k represents the bearing speed under the constant value condition of the kth section in the load spectrum; D i ' represents the total damage of the node under a certain constant value condition.

[0123] After 13 load spectrum cycles, the total damage of bearings A and B is 0.019 and 0.075 respectively. According to formula (16), substituting l = 12500km, the service life of high-speed ball bearings A and B of the electric drive system at 90% reliability under the random road load spectrum is 688,000 km and 167,000 km respectively. The difference in damage between bearings A and B is that the number of positive torque conditions in the load spectrum is greater than the number of negative torque conditions. Under the positive and negative torque conditions, bearings B and A bear axial forces respectively, and the positive torque condition contributes more to the damage of bearing B and the negative torque condition contributes more to the damage of bearing A. In this regard, the structural parameters of bearing B or the shaft system parameters can be optimized to meet the requirements of the random road load spectrum.

[0124]

[0125] L represents the life of the entire bearing when the reliability is 0.9; l represents the mileage of the vehicle.

[0126] Embodiment 2

[0127] The present embodiment also provides a high-speed bearing fatigue life prediction system in a high-speed transmission system, including: an external load extraction module, an internal load construction module, a stress extraction module and a damage calculation module; the external load extraction module is used to extract the load on the bearing to be predicted in the electric drive system; the internal load construction module is used to construct a bearing mechanics model based on the extracted load; the stress extraction module is used to utilize the bearing mechanics model, combined with the high-speed effect and the contact point position change sequence, to extract the contact stress time series at any position of the inner and outer raceways; the damage calculation module is used to traverse and solve all contact point damages of the inner and outer raceways based on the extracted contact stress time series to complete the bearing life prediction.

[0128] The expressions for the loads on the bearings include:

[0129]

[0130] Wherein, subscripts A and B represent bearing A and bearing B respectively; F r 、F t and F a Respectively represent the circumferential, radial and axial forces of the input shaft helical gear; F x 、F y and F z Represents forces in different directions; M x and M y Represents the overturning moment.

[0131] The workflow of the construction module includes: selecting the bearing type and configuration and extracting the load on the bearing; and then constructing the bearing mechanical model according to the size, direction and action point of the extracted load.

[0132] The bearing mechanics model constructed includes:

[0133]

[0134] In the formula, F x 、F y and F z Represents forces in different directions; M x and M y represents the overturning moment; ij and λ oj Both represent the bearing ball torque distribution coefficient; z represents the number of bearing rolling elements; α ij , α oj Respectively represent the actual contact angle between the bearing ball and the inner and outer raceways; F cj Indicates centrifugal force; M gj Indicates the gyroscopic torque; Q ij and Q oj Indicates the normal load of the bearing ball in contact with the inner and outer raceways respectively; D w Indicates the ball diameter; Tiψ Indicates the friction force of the inner raceway; R i Indicates the rotation radius of the center of curvature of the inner raceway of the bearing; ψ j It represents the time sequence of the positions of the jth contact point on the inner raceway of the bearing at each contact.

[0135] The workflow of the damage calculation module includes: based on the constructed bearing mechanics model and combined with Hertz contact theory, the stress distribution and deformation are obtained; based on the stress distribution and deformation at different times, the stress time series is obtained; based on the stress time series, the bearing life prediction is completed.

[0136] The above-mentioned Hertz contact theory mainly uses the contact load, the equivalent elastic modulus at the contact point between the bearing ball and the raceway, the eccentricity of the contact ellipse, and the first and second complete elliptic integrals to calculate the major semi-axis length, minor semi-axis length and contact deformation of the contact ellipse to characterize the point contact area characteristics between the bearing ball and the raceway; then, the maximum contact stress is calculated using the contact ellipse length, minor semi-axis length and contact load; finally, the contact stress of each point in the contact area is calculated.

[0137] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for predicting fatigue life of high-speed bearings in a high-speed transmission system, characterized in that the steps include: Extract the load on the bearing to be predicted in the high-speed transmission system; Based on the extracted loads, a bearing mechanics model is constructed; By using the bearing mechanics model, combined with the high-speed effect and the contact point position change sequence, the contact stress sequence at any position of the inner and outer raceways is extracted; Based on the extracted contact stress time series, the damage of all contact points on the inner and outer raceways is traversed and solved to complete the bearing life prediction.

2. The method for predicting fatigue life of high-speed bearings in a high-speed transmission system according to claim 1, characterized in that: The expressions for the loads acting on the bearing include: In the formula, subscripts A and B represent bearing A and bearing B at both ends of the shaft respectively; F r 、F t and F a Respectively represent the circumferential, radial and axial forces of the input shaft helical gear; F x 、F y and F z Represents forces in different directions; M x and M y Represents the overturning moment.

3. The method for predicting fatigue life of high-speed bearings in a high-speed transmission system according to claim 1, characterized in that: The method for constructing the bearing mechanics model includes: selecting the bearing type and configuration and extracting the load on the bearing; and then constructing the bearing mechanics model according to the size, direction and action point of the extracted load.

4. The method for predicting fatigue life of high-speed bearings in a high-speed transmission system according to claim 1, characterized in that: The bearing mechanics model constructed includes: In the formula, F x 、F y and F z Represents forces in different directions; M x and M y represents the overturning moment; ij and λ oj Both represent the bearing ball torque distribution coefficient; z represents the number of bearing rolling elements; α ij , α oj Respectively represent the actual contact angle between the bearing ball and the inner and outer raceways; F cj Indicates centrifugal force; M gj Indicates the gyroscopic torque; Q ij and Q oj Indicates the normal load of the bearing ball in contact with the inner and outer raceways respectively; D w Indicates the ball diameter; T iψ Indicates the friction force of the inner raceway; R i Indicates the rotation radius of the center of curvature of the bearing raceway; ψ j It represents the time sequence of the orientation of each contact of the j-th contact point on the inner raceway of the bearing; the subscript i represents the inner ring of the bearing, j represents the j-th contact point on the bearing raceway, and ψ represents the orientation angle of the contact point when it contacts.

5. The method for predicting fatigue life of high-speed bearings in a high-speed transmission system according to claim 4, characterized in that: The method for predicting bearing life includes: based on the bearing mechanics model, combined with Hertz contact theory, obtaining stress distribution and deformation; based on the stress distribution and deformation at different times, obtaining stress time series; based on the stress time series, completing bearing life prediction.

6. A high-speed bearing fatigue life prediction system in a high-speed transmission system, the system is used to implement the method described in any one of claims 1 to 5, characterized in that: include: External load extraction module, internal load construction module, stress extraction module and damage calculation module; The external load extraction module is used to extract the load on the bearing to be predicted in the high-speed transmission system; The internal load construction module is used to construct a bearing mechanics model based on the extracted loads; The stress extraction module is used to extract the contact stress time series at any position of the inner and outer raceways by utilizing the bearing mechanics model, combining the high-speed effect and the contact point position change time series; The damage calculation module is used to traverse and solve the damage of all contact points of the inner and outer raceways based on the extracted contact stress time series to complete the bearing life prediction.

7. The high-speed bearing fatigue life prediction system in a high-speed transmission system according to claim 6, characterized in that: The expressions for the loads acting on the bearing include: Wherein, subscripts A and B represent bearing A and bearing B respectively; F r 、F t and F a Respectively represent the circumferential, radial and axial forces of the input shaft helical gear; F x 、F y and F z Represents forces in different directions; M x and M y Represents the overturning moment.

8. The high-speed bearing fatigue life prediction system in a high-speed transmission system according to claim 6, characterized in that: The workflow of the construction module includes: selecting the bearing type and configuration and extracting the load on the bearing; and then constructing the bearing mechanical model according to the size, direction and action point of the extracted load.

9. The high-speed bearing fatigue life prediction system in a high-speed transmission system according to claim 8, characterized in that: The bearing mechanics model constructed includes: In the formula, F x 、F y and F z Represents forces in different directions; M x and M y represents the overturning moment; ij and λ oj Both represent the bearing ball torque distribution coefficient; z represents the number of bearing rolling elements; α ij , α oj Respectively represent the actual contact angle between the bearing ball and the inner and outer raceways; F cj Indicates centrifugal force; M gj Indicates the gyroscopic torque; Q ij and Q oj Indicates the normal load of the bearing ball in contact with the inner and outer raceways respectively; D w Indicates the ball diameter; T iψ Indicates the friction force of the inner raceway; R i Indicates the rotation radius of the center of curvature of the bearing raceway; ψ j It represents the time sequence of the positions of the jth contact point on the inner raceway of the bearing at each contact.

10. The high-speed bearing fatigue life prediction system in a high-speed transmission system according to claim 9, characterized in that: The workflow of the damage calculation module includes: based on the bearing mechanics model, combined with Hertz contact theory, obtaining the stress distribution and deformation; based on the stress distribution and deformation at different times, obtaining the stress time series; based on the stress time series, completing the bearing life prediction.

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