A method for fatigue life analysis of sun gear shaft bearing of continuously variable transmission

Abstract

The present invention discloses a method for fatigue life analysis of a sun gear shaft bearing of a continuously variable transmission, comprising the following steps: (1) determining the operating parameters of the bearing under different gear positions; (2) establishing a finite element model of the bearing and importing it into a dynamic analysis software to set the contact parameters of the bearing; (3) constructing a strain elastic model of the bearing material from the perspective of fracture mechanics, compiling a crack extension program, calculating and analyzing the numerical value of the bearing crack, and obtaining the fatigue life of the bearing under the crack; (4) establishing a bearing damage evolution constitutive equation from the perspective of damage mechanics, verifying the equation, calculating the bearing damage numerical value, and obtaining the fatigue life of the bearing under the damage; (5) comparing the theoretical and simulated life analysis of damage and cracks with fatigue test data to obtain the final result of the bearing fatigue life prediction analysis. The present invention can effectively analyze the fatigue life of the bearing under the actual conditions of the continuously variable transmission and improve the prediction accuracy of the bearing fatigue life.

Description

Technical Field

[0001] The invention relates to the technical field of continuously variable transmissions, and in particular to a method for analyzing fatigue life of a sun gear shaft bearing of a continuously variable transmission. Background Art

[0002] Bearings are important components of high-speed mechanical equipment, and their operating conditions directly affect the normal operation of major equipment. Studies have shown that equipment damage caused by bearing failure in high-speed rotating mechanisms accounts for 30% of continuously variable transmission failure damage. Bearing cracks and failure wear damage have become the main problems of continuously variable transmission damage. With the advancement of science and technology, more in-depth research should be conducted on the fatigue life, cracks and wear of bearings under technical conditions. The stress concentration part of the bearing has the largest deformation, which will cause cracks and wear. How to accurately predict crack expansion and wear evolution to improve the bearing life deserves attention. In order to solve the above problems, it is necessary to propose a fatigue life analysis method based on fracture mechanics and damage mechanics for bearing life theory to improve the accuracy of bearing fatigue life analysis prediction.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The purpose of the present invention is to provide a method for analyzing the fatigue life of a sun gear shaft bearing of a continuously variable transmission, which can effectively analyze the fatigue life of the bearing under actual conditions of a continuously variable transmission, improve the prediction accuracy of the bearing fatigue life, have broad application prospects, and are conducive to popularization and application.

[0005] In order to achieve the above object, the present invention provides a method for analyzing fatigue life of a continuously variable transmission sun gear shaft bearing, comprising the following steps:

[0006] (1) Determine the operating parameters of the sun gear shaft bearing of the continuously variable transmission at different gear positions;

[0007] (2) Establish a bearing finite element model and import it into dynamic analysis software to set bearing contact parameters;

[0008] (3) Fracture mechanics analysis: From the perspective of fracture mechanics, a strain elastic model of bearing materials is constructed, a crack extension program is compiled, the bearing crack values ​​are calculated and analyzed, and the fatigue life of the bearing under cracks is obtained;

[0009] (4) Damage mechanics analysis: From the perspective of damage mechanics, the bearing damage evolution constitutive equation is established and verified, the bearing damage value is calculated, and the bearing fatigue life under damage is obtained;

[0010] (5) Comprehensive fatigue life analysis: The simulated fatigue life analysis based on fracture mechanics and damage mechanics combines theoretical and experimental evidence, compares the theoretical and simulated life analysis of damage and cracks with fatigue test data, and obtains the final results of bearing fatigue life prediction analysis.

[0011] Preferably, in step (2), the dynamic analysis software is ANSYS Workbench, and after the bearing model is imported, the contact and clearance parameter settings between the inner ring and the rolling element, the outer ring and the rolling element, and the rolling element and the retaining frame are defined.

[0012] Preferably, in the step (3), the crack extension program is compiled according to the ANSYS Workbench command flow Command and Matlab.

[0013] Preferably, in the step (3), the calculation of the fatigue life of the bearing under cracks relies on the joint comparison of fatigue life calculation results by ANSYS Workbench and Matlab.

[0014] Preferably, in step (4), the establishment of the bearing damage evolution constitutive equation is programmed and inserted into the ANSYS Workbench command flow Command.

[0015] Preferably, in step (4), the calculation of the fatigue life of the bearing under damage relies on calculations using ANSYS Workbench.

[0016] Preferably, in step (4), fatigue life analysis based on damage mechanics adopts a two-dimensional plane stress method and a maximum stress element method.

[0017] The present invention provides a method for analyzing fatigue life of a continuously variable transmission sun gear shaft bearing, which has the following beneficial effects.

[0018] The present invention starts from the dual perspectives of fracture mechanics and damage mechanics (based on the two-dimensional plane stress method and the maximum stress unit method), utilizes the complementary advantages and disadvantages of the two mechanical models to analyze the bearing fatigue life, and finally combines theoretical and experimental evidence to effectively analyze the fatigue life of the continuously variable transmission sun gear shaft bearing under different gear conditions, thereby effectively improving the prediction accuracy of the bearing fatigue life. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A flow chart of a method for analyzing fatigue life of a sun gear shaft bearing of a continuously variable transmission provided by the present invention;

[0020] Figure 2 A schematic diagram of fracture mechanics analysis of a method for fatigue life analysis of a sun gear shaft bearing of a continuously variable transmission provided by the present invention;

[0021] Figure 3 A schematic diagram of damage mechanics analysis of a method for fatigue life analysis of a sun gear shaft bearing of a continuously variable transmission provided by the present invention;

[0022] Figure 4 A schematic diagram of a comprehensive fatigue life analysis of a method for fatigue life analysis of a continuously variable transmission sun gear shaft bearing provided by the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with specific embodiments and drawings to help understand the content of the present invention.

[0024] like Figure 1 FIG. 1 is a flow chart of a method for analyzing fatigue life of a sun gear shaft bearing of a continuously variable transmission provided by the present invention. The method for analyzing fatigue life of a sun gear shaft bearing of a continuously variable transmission comprises the following steps:

[0025] (1) Determine the operating parameters of the sun gear shaft bearing of the continuously variable transmission at different gear positions;

[0026]

[0027] (2) Establish a bearing finite element model and import it into the dynamic analysis software to set the bearing contact parameters. The dynamic analysis software is ANSYS Workbench. After importing the bearing model, define the contact and clearance parameters between the inner ring and the rolling element, the outer ring and the rolling element, and the rolling element and the cage.

[0028] (3) Fracture mechanics analysis: From the perspective of fracture mechanics, a strain elastic model of bearing materials is constructed, a crack extension program is compiled, the bearing crack value is calculated and analyzed, and the bearing fatigue life under crack is obtained. The crack extension program is compiled according to the ANSYS Workbench command flow and Matlab. The calculation of bearing fatigue life under crack depends on the joint comparison of fatigue life calculation results by ANSYS Workbench and Matlab.

[0029] (4) Damage mechanics analysis: From the perspective of damage mechanics, the bearing damage evolution constitutive equation is established, and the equation is verified, the bearing damage value is calculated, and the bearing fatigue life under damage is obtained. The fatigue life analysis based on damage mechanics adopts the two-dimensional plane stress method and the maximum stress unit method. The establishment of the bearing damage evolution constitutive equation is based on programming and inserted into the ANSYS Workbench command flow Command. The calculation of the bearing fatigue life under damage depends on the calculation results of ANSYS Workbench.

[0030] (5) Comprehensive fatigue life analysis: The simulated fatigue life analysis based on fracture mechanics and damage mechanics combines theoretical and experimental evidence, compares the theoretical and simulated life analysis of damage and cracks with fatigue test data, and obtains the final results of bearing fatigue life prediction analysis.

[0031] like Figure 2 The figure shows a fracture mechanics analysis schematic diagram of a method for fatigue life analysis of a continuously variable transmission sun gear shaft bearing provided by the present invention. The fracture mechanics analysis includes compiling a crack extension program, and compiling the crack extension program in the ANSYS Workbench command flow and Matlab to perform theoretical calculation of life.

[0032] The crack extension program compiled by Matlab includes three stages: no extension, stable extension, and unstable extension:

[0033] The relationship between the stress intensity factor variation range and the crack growth rate under the stress fatigue mechanism established by Paris's law is:

[0034]

[0035] Where: C, m are Paris law constants, which are related to material properties and stress ratio. △K is the range of stress intensity factor variation within the fatigue cycle.

[0036] Specifically, calculate the equivalent stress intensity factor:

[0037] The equivalent stress intensity factor K can express the stress intensity at the crack end:

[0038]

[0039] Where: a is the crack size.

[0040] Based on the equivalent stress intensity factor, the fatigue life is calculated according to the modified Paris Forman formula:

[0041] da / dN=[C(K) n ] / [(1-R)K C -K]

[0042] Where: a is the crack size; N is the number of fatigue cycles; C and n are the material coefficients determined by the test, n = 2 to 4.

[0043] ANSYS Workbench compiles crack extension program to solve the command and inserts the command flow into the command:

[0044] / SOLU

[0045] CINT,NEW,One

[0046] CINT,TYPE,TSTR

[0047] CINT,CTNC,NS_SECrack_Front

[0048] CINT,NCON,10

[0049] CINT,LIST

[0050] ALLSEL,ALL

[0051] / SHOW,png

[0052] / POST One

[0053] / OUT,

[0054] PLCINT,,,TSTRESS

[0055] like Figure 3 As shown, it is a schematic diagram of damage mechanics analysis of a method for fatigue life analysis of a continuously variable transmission sun gear shaft bearing provided by the present invention. Damage mechanics analysis includes analyzing the fatigue life of the bearing under damage based on a simplified two-dimensional plane stress method and a maximum stress element method. The damage analysis is based on the establishment of a damage evolution constitutive equation and is programmed according to the ANSYS Workbench command flow Command.

[0056] Simplify the 2D plane stress and plane strain physics equations:

[0057]

[0058] Where: E is the elastic modulus of the bearing material, μ is the Poisson's ratio of the bearing material.

[0059] The principal stress acting on the principal plane corresponds to the maximum value:

[0060]

[0061] Based on the damage evolution constitutive equation, insert the command flow in ANSYS Workbench to implement damage analysis:

[0062] Damage constitutive equation:

[0063]

[0064]

[0065] Where: E is the elastic modulus of the bearing material, μ is the Poisson's ratio of the bearing material, D ranges from 0 to 1, σαβ represents stress, εαβ represents stress, α and β represent free indicators, and δαβ represents the Kronecker function.

[0066] 1. K, H, and P are constitutive parameters that define the contact damage between the inner ring and the rolling element (all rolling elements must be defined):

[0067] tb,wear,cid,,,arcd

[0068] tbdata,1,K,H,P,V

[0069] Define outer ring and rolling element contact damage (all rolling elements must be defined):

[0070] tb,wear,cid,,,arcd

[0071] tbdata,1,K,H,P,V

[0072] The calculation of fatigue life based on the damaged state is:

[0073]

[0074] Where: B and ν can be determined by material fatigue test; when the initial material damage is 0, that is, D=0, N=0; when the bearing material is damaged by fatigue, it is theoretically regarded as D=1; Nf is the fatigue life.

[0075] like Figure 4 FIG. 1 is a schematic diagram of a comprehensive fatigue life analysis method for analyzing fatigue life of a continuously variable transmission sun gear shaft bearing provided by the present invention. The comprehensive fatigue life analysis includes a dual-angle combined theory and experimental comprehensive analysis of fatigue life.

[0076] Starting from the dual perspectives of fracture mechanics and damage mechanics, a new idea for life assessment is proposed by utilizing the complementary advantages and disadvantages of the two mechanical models. The advantages and disadvantages of the two models complement each other, and the life is evaluated from two angles. The connection between the stress-strain field and crack propagation, and the computational coupling of bearing fatigue damage and stress-strain field are realized. Finite element calculation, theoretical calculation, and experimental evidence are combined to comprehensively evaluate the fatigue life of bearings.

[0077] The present invention performs fatigue life analysis on bearing structures based on the method of combining finite element analysis results from dual angles of damage mechanics and fracture mechanics, which is more convincing, and the cumulative numerical calculation of fatigue damage of bearing parts will be more realistic and reasonable, and the accuracy of life assessment results will be higher.

[0078] The invention concept is described in detail using specific examples herein, and the description of the above embodiments is only used to help understand the core idea of ​​the invention. It should be pointed out that any obvious modification, equivalent substitution or other improvement made by a person of ordinary skill in the art without departing from the invention concept should be included in the protection scope of the present invention.

Claims

1. A method for fatigue life analysis of a sun gear shaft bearing of a continuously variable transmission, characterized in that: The steps include: (1) Determine the operating parameters of the sun gear shaft bearing of the continuously variable transmission at different gear positions; (2) Establish a bearing finite element model and import it into dynamic analysis software to set bearing contact parameters; (3) Fracture mechanics analysis: From the perspective of fracture mechanics, a strain elastic model of bearing materials is constructed, a crack extension program is compiled, the bearing crack value is calculated and analyzed, and the fatigue life of the bearing under cracks is obtained. The crack extension program is compiled according to the ANSYS Workbench command flow and Matlab. The calculation of the fatigue life of the bearing under cracks depends on the joint comparison of the fatigue life calculation results of ANSYS Workbench and Matlab. (4) Damage mechanics analysis: From the perspective of damage mechanics, the bearing damage evolution constitutive equation is established and verified, the bearing damage value is calculated, and the bearing fatigue life under damage is obtained. The establishment of the bearing damage evolution constitutive equation is based on programming and inserted into the ANSYS Workbench command flow Command. The calculation of the bearing fatigue life under damage depends on the calculation results of ANSYS Workbench. The fatigue life analysis based on damage mechanics adopts the two-dimensional plane stress method and the maximum stress element method; (5) Comprehensive fatigue life analysis: The simulated fatigue life analysis based on fracture mechanics and damage mechanics combines theoretical and experimental evidence, compares the theoretical and simulated life analysis of damage and cracks with fatigue test data, and obtains the final result of bearing fatigue life prediction analysis.

2. The method for analyzing fatigue life of a continuously variable transmission sun gear shaft bearing according to claim 1, characterized in that: In the step (2), the dynamic analysis software is ANSYS Workbench. After the bearing model is imported, the contact and clearance parameters between the inner ring and the rolling element, the outer ring and the rolling element, and the rolling element and the retaining frame are defined.

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