Wheel disc fatigue life prediction method considering residual stress relaxation influence

Abstract

A wheel disc fatigue life prediction method considering residual stress relaxation influence comprises the following steps: obtaining fatigue load of each examination part of a wheel disc and stress distribution Si of a notched test bar under different net section stress loads, and obtaining test fatigue life Nj of the notched test bar under different net section stress loads; based on the stress distribution Si, obtaining the stress amplitude delta Si of the dangerous part of the wheel disc and the notch test bar when the stress ratio is 0 under the loading and unloading conditions; calculating the fatigue life N of the dangerous part of the wheel disc and calculating the fatigue life Ni of the notched test bar through the stress amplitude delta Si when the stress ratio is 0; and introducing a residual stress relaxation life evaluation coefficient fa, and obtaining a stress relaxation fatigue life Na considering residual stress attenuation. And the fatigue life of the wheel disc is corrected by introducing the residual stress relaxation life evaluation coefficient, so that the accuracy of predicting the fatigue life of the aero-engine wheel disc is improved, and the reliability of the aero-engine wheel disc structure design is further improved.

Description

Technical Field

[0001] The invention belongs to the field of aeroengines, and in particular relates to a method for predicting wheel fatigue life taking into account the influence of residual stress relaxation. Background Art

[0002] With the continuous improvement and innovation of domestic aero-engine technology, the research and prediction technology of engine life is also constantly improving. The life of key components of aero-engines directly affects the service life and safety of the engine. As a key component of the engine, the prediction of its life is also a hot research topic in this field. At present, the methods for predicting the life of aero-engine discs include grain size correction method, low-cycle fatigue life analysis method, etc.

[0003] For example, the patent document with publication number CN107451377B involves a grain size correction method for the life analysis of aircraft engine disc structures. Metallographic analysis is carried out on standard samples sampled from different parts, and the average grain size is introduced to correct the existing deterministic life model to improve the prediction accuracy; a probabilistic life model is established for the test data of standard samples to quantitatively describe the dispersion of material properties; finally, the damage parameters of the deterministic model are combined with the probabilistic model to establish a probabilistic life model corrected by grain size. Based on the fatigue life model, the average grain size is introduced to correct the life model, which significantly improves the prediction accuracy of the life model. The deterministic grain size correction life model is further probabilized, which can ensure the accuracy of the deterministic life prediction results while achieving a quantitative description of the dispersion of life data.

[0004] For example, the patent document with publication number CN117473841A provides a body method and system for low-cycle fatigue life analysis of a wheel considering fatigue volume effect. For the wheel structure, a "body method" containing dangerous volume information is introduced to conduct strain fatigue reliability analysis of the wheel, so as to solve the shortcomings of the current local stress / strain method for predicting fatigue life of large-volume, high-stress gradient wheels, which has large errors and even dangerous tendencies.

[0005] However, the above-mentioned prior arts have not considered the influence of residual stress relaxation on the fatigue life of the wheel. The overspeed pre-rotation of the aircraft engine wheel can form a certain plastic deformation at the stress concentration part of the wheel, which leads to a large residual compressive stress after unloading, which reduces the average stress level at the stress concentration part and improves the low-cycle fatigue life. However, since the residual stress will relax with the increase of the load test piece and the number of cycles under high temperature conditions, the residual compressive stress level will gradually decrease. Therefore, the influence of residual stress relaxation must be considered when predicting the fatigue life after the overspeed pre-rotation of the wheel. However, there is no effective technical solution for predicting the fatigue life of the wheel considering the influence of residual stress relaxation in the prior art. Summary of the invention

[0006] In order to solve the above technical problems, the present application provides a method for predicting the fatigue life of a wheel considering the influence of residual stress relaxation, comprising the following steps:

[0007] Obtain the fatigue load of each test part of the wheel and the stress distribution S of the notched test bar under different net cross-sectional stress loads i , obtain the test fatigue life N of the notched test bar under different net section stress loads j ;

[0008] Based on the stress distribution S i , obtain the stress amplitude ΔS of the wheel dangerous part and the notched test bar when the stress ratio is 0 under loading and unloading conditions i ;

[0009] By stress amplitude ΔS i , calculate the fatigue life N of the dangerous part of the wheel when the stress ratio is 0 计算 And notched test bar calculation fatigue life N i ;

[0010] Based on the fatigue life of dangerous parts of the wheel 计算 、Calculation of fatigue life of notched test bar N i And notched test bar test fatigue life N j , obtain the residual stress relaxation life evaluation coefficient f a and stress relaxation fatigue life considering residual stress decay N a .

[0011] Furthermore, the stress distribution S of the fatigue load of each test part of the wheel i The stress distribution S of the notched test bar under different net cross-sectional stress loads is obtained by finite element elastic calculation analysis; i It is obtained by subjecting notched test bars to fatigue life tests under different net section stress loads.

[0012] Furthermore, the stress amplitude ΔS i It is obtained using the Goodman correction method and is expressed as: ΔS i =[ΔS1,ΔS2,ΔS3,…].

[0013] Further, the stress amplitude ΔS of the dangerous part of the wheel disc when the stress ratio is 0 under the loading and unloading conditions is obtained. i When the fatigue load of the dangerous part of the wheel is converted into the fatigue load with stress ratio R = 0, the stress amplitude ΔS of the dangerous part of the wheel is obtained. i and maximum stress S max .

[0014] Furthermore, the stress amplitude ΔS of the notched test bar when the stress ratio is 0 under the loading and unloading conditions is i When the stress distribution results S of the notched test bar under different stress ratios are i , converted into the stress amplitude ΔS of the notched test bar under stress ratio R = 0 i .

[0015] Furthermore, the N 计算 The calculation method is as follows:

[0016] Using smooth test bars, high temperature low cycle fatigue tests were carried out under given pre-stretching stress conditions at different stress levels, and the relationship between pre-stretching stress and life under different stress ratio conditions was obtained: N f =S 拉伸 (S max ,R,T,C), and then determine the optimal pre-stretching stress S 拉伸 , where N f is the tensile fatigue life, S max is the maximum stress, R is the stress ratio, T is the fatigue test temperature in °C, and C is a material-related constant;

[0017] Through the formula σ ture =σ engineering (1+ε), convert the engineering stress into the real stress of the smooth test bar when the stress ratio R=0, carry out fatigue tests at different stress levels, substitute the test results into the material SN curve, obtain the SN curve of the smooth test bar when the stress ratio R=0, and calculate the fatigue life N of the dangerous part of the wheel when the stress ratio R=0 计算 , where σ ture is the true stress, σ engineering is the engineering stress and ε is the engineering strain.

[0018] Furthermore, the N i The calculation method is to calculate the stress amplitude ΔS of the notched test bar when the stress ratio is 0 i Substitute the SN curve of the smooth test bar under stress ratio R = 0, and calculate the fatigue life N of the notched test bar when stress ratio R = 0 under different net section stress loads. i .

[0019] Furthermore, the residual stress relaxation life evaluation coefficient f a is the test fatigue life of the notched test bar N j Calculated fatigue life N of notched test bar when stress ratio R = 0 i The ratio, f a =N j / N i , where f a is the residual stress relaxation life evaluation factor, N j is the test fatigue life, Ni To calculate fatigue life.

[0020] Furthermore, the test fatigue life N of the notched test bar j Obtained through fatigue testing of notched test bars under different net section stress loads.

[0021] Furthermore, the stress relaxation fatigue life N a By introducing the residual stress relaxation life evaluation factor f a Calculated value of wheel fatigue life when stress ratio R=0 N 计算 Correction acquisition, N a =N 计算 ·f a , where N a is the stress relaxation fatigue life considering the residual stress decay.

[0022] The beneficial effects of the present invention are that, based on the fatigue life test, the Goodman formula is used for correction, and the residual stress relaxation life assessment coefficient is introduced to correct the fatigue life of the wheel disc, so as to obtain the fatigue life of the wheel disc taking into account the residual stress attenuation, and effectively predict the fatigue life of the aircraft engine wheel disc; this prediction method is more reliable and can improve the accuracy of the prediction, and is a new direction and key point in the research on the life prediction of the aircraft engine wheel disc; and the prediction method of the present invention is also applicable to the life prediction of other key components or the whole machine of the aircraft engine, as well as other components with life prediction requirements, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flowchart of the fatigue life prediction process of a wheel disc according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0025] An embodiment of the present invention provides a wheel fatigue life prediction method taking into account the influence of residual stress relaxation, which is used to predict the wheel fatigue life problem under different stress ratio conditions. Figure 1 The present invention is a flowchart of a method for predicting the fatigue life of a wheel disc taking into account the influence of residual stress relaxation. The main steps of the method include:

[0026] Step S100

[0027] First, obtain the fatigue load of each test part of the wheel and the stress distribution S of the notched test bar under different net cross-sectional stress loads. i , obtain the test fatigue life N of the notched test bar under different net section stress loads j , the calculation in this stage includes the following operations:

[0028] Step S101:

[0029] 1) Analyze the stress distribution of each test part at the maximum steady-state speed of the engine rotor through finite element elastic calculation to determine the dangerous parts that affect fatigue life;

[0030] 2) Based on the calculation results of 1), combined with the finite element elastic-plastic analysis, the stress distribution of different stress ratios at the dangerous part of the wheel under loading and unloading conditions is obtained:

[0031] S i =[S1,S2,S3,…] (1)

[0032] Step S102: Through the notched test bar fatigue test, the test fatigue life N of the notched test bar under different net cross-sectional stress loads can be obtained. j , (unit: times):

[0033] N j =[N1,N2,N3,…] (2)

[0034] Step S103: Considering the pre-tensioning condition under high temperature conditions, fatigue life tests are performed using notched test bars under different net cross-sectional stress loads. According to the test results, the stress distribution S of the notched test bars under different net cross-sectional stress loads under loading and unloading conditions is obtained. i , expressed as:

[0035] S i =[S1,S2,S3,…] (3)

[0036] Step S110

[0037] Second: Based on stress distribution S i , obtain the stress amplitude ΔS of the wheel dangerous part and the notched test bar when the stress ratio is 0 under loading and unloading conditions i , this phase includes the following operations:

[0038] Step S111: Using the Goodman correction method, the fatigue load of the dangerous part of the wheel is converted into a fatigue load with a stress ratio R=0 for testing to obtain the stress amplitude ΔS i and maximum stress S max , (unit: MPa).

[0039] Specific method: The maximum stress when the above stress ratio is 0 is selected as the optimal pre-stretching stress of the material, and the pre-stretching stress at different stress levels is given respectively, and a low cycle fatigue test is carried out under high temperature conditions.

[0040] Step S112: Using the Goodman correction method, the test results in step S103 are converted into stress distribution results S of the notched test bar under different stress ratios.i , converted into stress amplitude ΔS under stress ratio R = 0 i , (unit: MPa):

[0041] ΔS i =[ΔS1, ΔS2, ΔS3, …] (4)

[0042] Step S120

[0043] Third, through the stress amplitude ΔS i , calculate the fatigue life N of the dangerous part of the wheel when the stress ratio is 0 计算 And notched test bar calculation fatigue life N i , this phase includes the following operations:

[0044] Step S121:

[0045] According to the fatigue test results of step S111, the relationship between pre-tension stress and life under different stress ratio conditions is obtained:

[0046] N f =S 拉伸 (S max ,R,T,C) (5)

[0047] The optimal pre-tension stress S is further determined from this relationship 拉伸 , (unit: MPa).

[0048] Where: N f is the tensile fatigue life, S max is the maximum stress, R is the stress ratio, T is the fatigue test temperature (unit: °C), and C is a material related constant.

[0049] According to the optimal pre-tension stress S determined above 拉伸 , the pre-tensile stress is the engineering stress, and the engineering stress is converted into the true stress of the test rod when the stress ratio R = 0 using formula (6):

[0050] σ ture =σ engineering (1+ε) (6)

[0051] Where: ture is the true stress, σ engineering is the engineering stress and ε is the engineering strain.

[0052] Step S122: The true stress σ obtained in step S121 is ture , substitute the material SN curve, and finally obtain the SN curve of the smooth test bar under the stress ratio R = 0 through data analysis and linear regression calculation. From this, the fatigue life N of the dangerous part of the wheel when the stress ratio R = 0 is calculated. 计算 , (unit: times).

[0053] Step S123: Different stress amplitudes ΔS in step S112 i Substitute the SN curve of the smooth test rod under stress ratio R=0 in step S122.

[0054] Step S124: Based on the SN curve of the smooth test bar under the stress ratio R=0 obtained in step S123, the fatigue life N of the notched test bar under different net cross-sectional stress loads when the stress ratio R=0 is calculated. i , (unit: times):

[0055] N i =[N1,N2,N3,…] (7)

[0056] Step S130

[0057] Finally, based on the fatigue life N of the dangerous parts of the wheel 计算 、Calculation of fatigue life of notched test bar N i And notched test bar test fatigue life N j , obtain the residual stress relaxation life evaluation coefficient f a And the stress relaxation fatigue life considering the residual stress decay. The calculation in this stage includes the following operations:

[0058] Step S131: In order to accurately predict the fatigue life of the wheel disc, the predicted life of the wheel disc is corrected by introducing the residual stress relaxation life evaluation coefficient, that is, using the test fatigue life N of the notched test bar in step S102 j Compared with the calculated fatigue life N of the notched test bar when the stress ratio R=0 in step S124 i , and then obtain the residual stress relaxation life evaluation coefficient f of the notched test bar under different net section stress loads a :

[0059] f a =N j / N i (8)

[0060] Where: f a is the residual stress relaxation life evaluation factor, N j is the test fatigue life, N i To calculate fatigue life.

[0061] Step S132: Using the introduced residual stress relaxation life evaluation coefficient f a Calculated value of wheel fatigue life when stress ratio R=0 N 计算 By making corrections, the stress relaxation fatigue life N considering the residual stress decay can be obtained. a :

[0062] N a=N 计算 ·f a (9)

[0063] Where: N a is the stress relaxation fatigue life considering the residual stress decay.

[0064] The present invention provides a life prediction method for an aircraft engine wheel disc under the influence of residual stress relaxation. The fatigue life of the wheel disc is corrected by introducing a residual stress relaxation life evaluation coefficient to obtain the fatigue life of the wheel disc considering residual stress attenuation, which is used to predict the fatigue life of the aircraft engine wheel disc. The prediction result is reliable and accurate. At the same time, the prediction method proposed by the present invention can not only predict the life of the aircraft engine wheel disc, but also is also applicable to predicting other key components or complete machines of the aircraft engine, and has a wide range of applications.

[0065] The above disclosure is only a specific embodiment of the present invention, but the present invention is not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for predicting the fatigue life of a wheel considering the influence of residual stress relaxation, characterized in that The following steps are involved: Obtain the fatigue load of each test part of the wheel and the stress distribution S of the notched test bar under different net cross-sectional stress loads i , obtain the test fatigue life N of the notched test bar under different net section stress loads j ; Based on the stress distribution S i , obtain the stress amplitude ΔS of the wheel dangerous part and the notched test bar when the stress ratio is 0 under loading and unloading conditions i ; By stress amplitude ΔS i , calculate the fatigue life N of the dangerous part of the wheel when the stress ratio is 0 计算 And notched test bar calculation fatigue life N i ; Based on the fatigue life of dangerous parts of the wheel 计算 、Calculation of fatigue life of notched test bar N i And notched test bar test fatigue life N j , obtain the residual stress relaxation life evaluation coefficient f a and stress relaxation fatigue life considering residual stress decay.

2. The method for predicting wheel fatigue life considering the influence of residual stress relaxation as claimed in claim 1, characterized in that: The stress distribution S of fatigue load at each test part of the wheel i The stress distribution S of the notched test bar under different net cross-sectional stress loads is obtained by finite element elastic calculation analysis; i It is obtained by conducting fatigue life tests on notched test bars under different net section stress loads under high temperature conditions.

3. The method for predicting wheel fatigue life considering the influence of residual stress relaxation as claimed in claim 1, characterized in that: The stress amplitude ΔS i It is obtained using the Goodman correction method and is expressed as: ΔS i =[ΔS1,ΔS2,ΔS3,…].

4. The method for predicting wheel fatigue life considering the influence of residual stress relaxation as claimed in claim 1, characterized in that: Obtain the stress amplitude ΔS of the dangerous part of the wheel when the stress ratio is 0 under the loading and unloading conditions i When the fatigue load of the dangerous part of the wheel is converted into the fatigue load with stress ratio R = 0, the stress amplitude ΔS of the dangerous part of the wheel is obtained. i and maximum stress S max .

5. The method for predicting wheel fatigue life considering the influence of residual stress relaxation as claimed in claim 1, characterized in that: Obtain the stress amplitude ΔS of the notched test bar when the stress ratio is 0 under the loading and unloading conditions i When the stress distribution results S of the notched test bar under different stress ratios are i , converted into the stress amplitude ΔS of the notched test bar under stress ratio R = 0 i .

6. The method for predicting wheel fatigue life considering the influence of residual stress relaxation as claimed in claim 1, characterized in that: The N 计算 The calculation method is as follows: Using smooth test bars, high temperature low cycle fatigue tests were carried out under given pre-tensile stress conditions of different stress levels, and the relationship between pre-tensile stress and life under different stress ratio conditions was obtained: N f =S 拉伸 (S max ,R,T,C), and then determine the optimal pre-stretching stress S 拉伸 , where N f is the tensile fatigue life, S max is the maximum stress, R is the stress ratio, T is the fatigue test temperature in °C, and C is a material-related constant; Through the formula σ ture =σ engineering (1+ε), convert the engineering stress into the real stress of the smooth test bar when the stress ratio R=0, carry out fatigue tests at different stress levels, substitute the test results into the material SN curve, obtain the SN curve of the smooth test bar when the stress ratio R=0, and calculate the fatigue life N of the dangerous part of the wheel when the stress ratio R=0 计算 , where σ ture is the true stress, σ engineering is the engineering stress and ε is the engineering strain.

7. The method for predicting wheel fatigue life considering the influence of residual stress relaxation as claimed in claim 1, characterized in that: The N i The calculation method is to calculate the stress amplitude ΔS of the notched test bar when the stress ratio is 0 i Substitute the SN curve of the smooth test bar under stress ratio R = 0, and calculate the fatigue life N of the notched test bar when stress ratio R = 0 under different net section stress loads. i .

8. The method for predicting wheel fatigue life considering the influence of residual stress relaxation as claimed in claim 1, characterized in that: The residual stress relaxation life evaluation factor f a is the test fatigue life of the notched test bar N j Calculated fatigue life N of notched test bar when stress ratio R = 0 i The ratio, f a =N j / N i , where f a is the residual stress relaxation life evaluation factor, N j is the test fatigue life, N i To calculate fatigue life.

9. The method for predicting wheel fatigue life considering the influence of residual stress relaxation as claimed in claim 1 or 8, characterized in that: The test fatigue life of the notched test bar is N j Obtained through fatigue testing of notched test bars under different net section stress loads.

10. The method for predicting wheel fatigue life considering the influence of residual stress relaxation as claimed in claim 1, characterized in that: The stress relaxation fatigue life N a By introducing the residual stress relaxation life evaluation factor f a Calculated value of wheel fatigue life when stress ratio R=0 N 计算 Correction acquisition, N a =N 计算 ·f a , where N a is the stress relaxation fatigue life considering the residual stress decay.

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