A multi-axial variable amplitude fatigue life prediction method based on critical plane

Abstract

The present application relates to the technical field of multi-axis mechanical fatigue, and particularly relates to a multi-axis variable amplitude fatigue life prediction method based on a critical plane. The uniaxial tension-compression fatigue limit and pure torsional fatigue limit of a metal material, the tensile yield strength and shear strength are obtained; the fatigue performance parameters, static force performance parameters and multi-axis fatigue loading soft coefficients of each level of load of the metal material are calculated to determine the critical plane of the metal material; the equivalent fatigue damage parameters on the critical plane of each level of load are obtained, and the fatigue life of the metal material under multi-axis variable amplitude loading conditions is obtained according to the equivalent fatigue damage parameters on the critical plane of each level of load. The present application is simple in form, and only needs to obtain the performance parameters of the metal material by consulting a manual to accurately predict the fatigue life of the metal material under multi-axis variable amplitude loading.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of multi-axial mechanical fatigue, and in particular to a multi-axial variable amplitude fatigue life prediction method based on a critical plane. BACKGROUND

[0002] In engineering practice in the field of aerospace and the like, many dangerous parts of structures bear multi-axial loads due to complex loading conditions, and most of them bear variable amplitude loads, such as fuselage panels, wing skins, aero-engine blades and discs, bearings and the like. The fatigue damage accumulation during loading is coupled by loading parameters and loading sequence, and thus the fatigue failure behavior is more complex than that of multi-axial constant amplitude fatigue failure. In order to further realize structure weight reduction on the basis of meeting the safety and fatigue performance of an aircraft structure, how to accurately and conveniently predict the fatigue life of a metal material under multi-axial variable amplitude loading which is more in line with engineering practice has attracted more and more attention from the engineering field.

[0003] In the aspect of life prediction, although many studies have been carried out, due to the complexity of multi-axial variable amplitude loading parameters, the test results are highly dispersed and the test cycle is long. At present, the research on multi-axial fatigue cumulative damage models is more focused on the applicability of uniaxial fatigue cumulative damage models in multi-axial fatigue problems. However, due to the irregular change of the size and direction of principal stress with the change of load under multi-axial variable amplitude fatigue load, the fatigue failure behavior and fatigue cumulative damage of the structure are more complex. When using uniaxial fatigue cumulative damage models to study multi-axial fatigue problems, there are certain limitations in the applicability of different materials and different loading paths.

[0004] At present, many models for calculating multi-axial variable amplitude fatigue damage accumulation have been proposed at home and abroad, but these models are relatively complex in form, and the parameters are difficult to confirm. They must be fitted by a large amount of experimental data, and are not convenient to apply to engineering practice. There is no simple, economical and accurate method for predicting multi-axial variable amplitude fatigue life among the existing multi-axial variable amplitude fatigue damage accumulation models. In addition, a large number of studies have shown that under multi-axial fatigue load, cracks are generated on a specific plane. The shear stress and normal stress on the plane will affect the initiation and propagation of fatigue cracks. Therefore, when predicting the multi-axial variable amplitude fatigue life in engineering, the fatigue life of a metal material can be predicted by determining the critical plane where fatigue cracks appear. SUMMARY

[0005] In order to solve the problem that the multiaxial variable amplitude fatigue life of metal materials cannot be simply, economically and accurately predicted in the prior art, the application provides a multiaxial variable amplitude fatigue life prediction method based on a critical plane, wherein the uniaxial tension-compression fatigue limit and the pure torsion fatigue limit, the tensile yield strength and the shear strength of the metal material are obtained by consulting a manual; then the fatigue performance parameters, the static force performance parameters and the multiaxial fatigue loading softness coefficient of each level of load of the metal material are obtained by calculation, and the critical plane of the metal material is determined according to the multiaxial fatigue loading softness coefficient of each level of load of the metal material, the fatigue performance parameters and the static force performance parameters; then the equivalent fatigue damage parameters on the critical plane of each level of load are obtained, and finally the fatigue life of the metal material under the multiaxial variable amplitude loading condition is calculated according to the equivalent fatigue damage parameters of each level of load. The application is simple in form, and the fatigue life of the metal material under the multiaxial variable amplitude loading condition can be accurately predicted only by obtaining the performance parameters of the metal material by consulting a manual.

[0006] The application adopts the following technical scheme, a multiaxial variable amplitude fatigue life prediction method based on a critical plane, comprising:

[0007] The uniaxial tension-compression fatigue limit and the pure torsion fatigue limit, the tensile yield strength and the shear strength of the metal material are obtained by consulting a manual;

[0008] The fatigue performance parameters of the metal material are obtained according to the uniaxial tension-compression fatigue limit and the pure torsion fatigue limit of the metal material;

[0009] The static force performance parameters of the metal material are obtained according to the tensile yield strength and the shear strength of the metal material;

[0010] The multiaxial fatigue loading softness coefficient of each level of load of the metal material is obtained, and the critical plane of the metal material is determined according to the multiaxial fatigue loading softness coefficient of each level of load of the metal material, the fatigue performance parameters and the static force performance parameters;

[0011] The equivalent fatigue damage parameters on the critical plane of each level of load are obtained, and the fatigue life of the metal material under the multiaxial variable amplitude loading condition is obtained according to the equivalent fatigue damage parameters on the critical plane of each level of load.

[0012] Further, the method for obtaining the fatigue performance parameters of the metal material is that the fatigue performance parameters of the metal material are obtained according to the ratio of the uniaxial tension-compression fatigue limit and the pure torsion fatigue limit of the metal material.

[0013] Further, the method for obtaining the static force performance parameters of the metal material is that the static force performance parameters of the metal material are obtained according to the ratio of the shear strength and the tensile yield strength of the metal material.

[0014] Further, the method for determining the critical plane of the metal material according to the multiaxial fatigue loading soft coefficient, the fatigue performance parameter and the static force performance parameter of each level of load of the metal material comprises:

[0015] According to the multiaxial fatigue loading soft coefficient η i of each level of load of the metal material, the fatigue performance parameter α' and the static force performance parameter β' are compared.

[0016] When η i ≤ α', the maximum normal stress plane is the critical plane; when α' i < β', the maximum damage plane is the critical plane, and when β' i ≤ η , the maximum shear stress amplitude plane is the critical plane.

[0017] Further, the expression of the equivalent fatigue damage parameter on the critical plane of each level of load is obtained as follows:

[0018]

[0019] Wherein, represents the maximum normal stress on the maximum damage critical plane, τ n,a represents the shear stress amplitude on the plane, τ na,max represents the shear stress amplitude on the maximum shear stress amplitude plane, n represents the normal stress direction, and a represents the amplitude; f -1 represents the pure torsional fatigue limit, t -1 represents the uniaxial tension-compression fatigue limit; η i represents the multiaxial fatigue loading soft coefficient of the i-th level of load of the metal material, α' represents the fatigue performance parameter, and β' represents the static force performance parameter; S eq,i represents the equivalent fatigue damage parameter on the i-th level of load critical plane, and eq represents the equivalent.

[0020] Further, the expression of the maximum normal stress on the maximum damage critical plane is obtained as follows:

[0021]

[0022] Wherein, represents the normal stress amplitude on the maximum damage critical plane, represents the average normal stress on the maximum damage critical plane, n represents the normal stress direction, and m represents the average, σ u represents the tensile strength, and is a fixed symbol.

[0023] Further, the expression of the multiaxial fatigue loading soft coefficient of each level of load of the metal material is obtained as follows:

[0024]

[0025] wherein, η i represents the multiaxial fatigue loading soft coefficient of the i-th level of the metal material, τ n,a represents the shear stress amplitude on the plane, σ n,a represents the normal stress amplitude on the plane, represents the plane direction (the included angle between the projection of the plane unit normal vector on the x-y plane and the x axis).

[0026] Further, the method for obtaining the fatigue life of the metal material under the multiaxial variable-amplitude loading condition is as follows:

[0027] obtaining the multiaxial variable-amplitude fatigue damage on the critical plane according to the equivalent fatigue damage parameter on the critical plane of each level of loading;

[0028] obtaining the fatigue life of the metal material under the multiaxial variable-amplitude loading condition according to the multiaxial variable-amplitude fatigue damage on the critical plane of the metal material.

[0029] The beneficial effects of the present application are as follows: through the technical means provided in the present application, the performance parameters of the metal material can be obtained by consulting the manual, so that the critical plane of the metal material can be quickly determined according to the performance parameters, and further, in the process of obtaining the fatigue life of the metal material, the influence of the loading parameter on the fatigue life of the metal material is represented by the equivalent fatigue damage parameter on the critical plane of each level of loading, and then the combined influence of the change of the critical plane direction and the stress distribution on the critical plane caused by the change of the loading parameter in each level of loading is considered, so that the multiaxial variable-amplitude fatigue test under the corresponding loading condition is not needed, and the multiaxial variable-amplitude fatigue life of the metal material can be accurately predicted without engineering constants, which is convenient for engineering application. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0031] Figure 1 A flowchart of a multiaxial variable-amplitude fatigue life prediction method based on a critical plane according to an embodiment of the present application is shown in the figure.

[0032] Figure 2 A flowchart of a method for predicting the fatigue life of a metal material under a multiaxial variable-amplitude loading condition according to an embodiment of the present application is shown in the figure.

[0033] Figure 3 A comparison chart of the fatigue life prediction of 30CrMnSiA steel under multiaxial variable-amplitude loading and the test data in the prior art according to an embodiment of the present application is shown in the figure.

[0034] Figure 4 Figure 1 is a comparison chart of the fatigue life prediction of the 2024-T4 aluminum alloy under the multi-axial amplitude loading of the embodiment of the present application and the test data in the prior art. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0036] The present application overcomes the deficiencies of the prior art, considers the influences of the stress amplitude ratio, phase difference, average stress and loading sequence on the fatigue failure life of the metal material under the multi-axial amplitude loading, takes the uniaxial tension-compression fatigue limit t -1 and the pure torsional fatigue limit f -1 , the tensile yield strength σ y and the shear strength τ u as the basic parameters, and provides a fatigue life prediction method of the metal material under the multi-axial amplitude fatigue loading without the need of multi-axial amplitude fatigue test. As shown in Figure 1, a flowchart of the multi-axial amplitude fatigue life prediction method based on the critical plane in the embodiment of the present application is given, which comprises the following steps. Figure 1

[0037] 101. Obtain the uniaxial tension-compression fatigue limit and the pure torsional fatigue limit, the tensile yield strength and the shear strength of the metal material by consulting the manual;

[0038] In one specific embodiment, the manual in the present application can be the China Aviation Material Manual, the Metal Material Manual or the Practical Metal Material Selection Manual, etc. The specific manual is selected according to the change of the metal material, that is, the metal material whose multi-axial amplitude fatigue life needs to be predicted is first determined, and then the manual recording the corresponding parameters of the metal material is searched to predict the multi-axial amplitude fatigue life of the metal material.

[0039] In the present embodiment, the uniaxial tension-compression fatigue limit t -1 and the pure torsional fatigue limit f -1 , the tensile yield strength σ y and the shear strength τ u of the metal material are first obtained by consulting the manual, so as to calculate the fatigue performance parameter α' and the static force performance parameter β' of the metal material.

[0040] ​102. Obtain the fatigue performance parameter of the metal material according to the uniaxial tension-compression fatigue limit and the pure torsion fatigue limit of the metal material;

[0041] The method for obtaining the fatigue performance parameter of the metal material is: obtaining the fatigue performance parameter of the metal material according to the ratio of the uniaxial tension-compression fatigue limit and the pure torsion fatigue limit of the metal material, and the calculation expression is:

[0042] α' = t -1 / f -1

[0043] Wherein, α' represents the fatigue performance parameter of the metal material, t -1 represents the uniaxial tension-compression fatigue limit of the metal material, f -1 is the pure torsion fatigue limit of the metal material; the formula is the existing formula, and the purpose is to take the fatigue performance parameter of the metal material as the critical value of the multi-axial loading fatigue soft coefficient, so as to subsequently judge the maximum damage plane.

[0044] 103. Obtain the static performance parameter of the metal material according to the tensile yield strength and the shear strength of the metal material;

[0045] The method for obtaining the static performance parameter of the metal material is: obtaining the static performance parameter of the metal material according to the ratio of the shear strength and the tensile yield strength of the metal material, and the calculation expression is:

[0046] β' = τ u / σ y

[0047] Wherein, β' represents the static performance parameter of the metal material, τ u represents the shear strength of the metal material, and σ y represents the tensile yield strength of the metal material; the formula is the existing formula, and the purpose is to take the static performance parameter of the metal material as the critical value of the multi-axial loading fatigue soft coefficient, so as to subsequently judge the maximum damage plane.

[0048] 104. Obtain the multi-axial fatigue loading soft coefficient of each level of load of the metal material, and determine the critical plane of the metal material according to the multi-axial fatigue loading soft coefficient of each level of load of the metal material, the fatigue performance parameter and the static performance parameter;

[0049] The expression for obtaining the multi-axial fatigue loading soft coefficient of each level of load of the metal material is:

[0050]

[0051] Wherein, η i represents the multi-axial fatigue loading soft coefficient of the i-th level of load of the metal material, τ n,adenotes the maximum normal stress amplitude in the plane, σ n,a denotes the maximum normal stress amplitude in the plane, σ denotes the plane direction (the angle between the projection of the plane unit normal vector on the x-y plane and the x axis).

[0052] The method for determining the critical plane of a metal material according to the multiaxial fatigue loading soft coefficient, the fatigue performance parameter and the static performance parameter of each level of load of the metal material comprises the following steps:

[0053] The multiaxial fatigue loading soft coefficient η i is compared with the fatigue performance parameter α' and the static performance parameter β';

[0054] When η i ≤ α', the maximum normal stress plane is the critical plane; when α' < η i < β', the maximum damage plane is the critical plane, and when β' ≤ η i , the maximum shear stress amplitude plane is the critical plane.

[0055] 105. The equivalent fatigue damage parameter on the critical plane of each level of load is obtained, and the fatigue life of the metal material under multiaxial variable amplitude loading is obtained according to the equivalent fatigue damage parameter on the critical plane of each level of load.

[0056] The expression for obtaining the equivalent fatigue damage parameter on the critical plane of each level of load is:

[0057]

[0058] wherein, denotes the maximum normal stress on the maximum damage critical plane, τ n,a denotes the shear stress amplitude in the plane, τ na,max denotes the shear stress amplitude on the maximum shear stress amplitude plane, n denotes the normal stress direction, a denotes the amplitude; f -1 denotes the pure torsional fatigue limit, t -1 denotes the uniaxial tension-compression fatigue limit; η i denotes the multiaxial fatigue loading soft coefficient of the i-th level of load of the metal material, α' denotes the fatigue performance parameter, and β' denotes the static performance parameter; S eq,i denotes the equivalent fatigue damage parameter on the i-th level of load critical plane, and eq denotes equivalent.

[0059] The crack initiation and propagation behavior can be predicted through the relationship between the loading path and the material performance, and the multiaxial fatigue crack initiation and propagation path is consistent with the basic assumption of the critical plane failure criterion, therefore, in the embodiment, the multiaxial fatigue loading soft coefficient η ithe relationship between the fatigue performance parameter α' and the static performance parameter β' of the material to select the maximum damage plane;

[0060] When η i ≤ α', which corresponds to a low stress amplitude ratio, the crack initiation and propagation are along the maximum normal stress plane, and the failure mode is close to that under uniaxial tension-compression loading. In this case, the maximum normal stress plane is selected as the critical plane under this loading path;

[0061] When α' < η i < β', which corresponds to a medium stress amplitude ratio, the crack transition from the first stage of crack propagation to the second stage of crack propagation. In this case, the plane with the maximum fatigue damage is selected as the critical plane under this loading path;

[0062] When β' ≤ η i , which corresponds to a high stress amplitude ratio, the crack initiation and propagation are along the maximum shear stress amplitude plane, and the failure mode is close to that under pure torsion loading. In this case, the maximum shear stress amplitude plane is selected as the critical plane under this loading path.

[0063] In this embodiment, the Goodman criterion is used to convert the normal stress amplitude on the maximum damage critical plane to obtain the expression of the maximum normal stress on the maximum damage critical plane as follows:

[0064]

[0065] wherein, represents the normal stress amplitude on the maximum damage critical plane, represents the average normal stress on the maximum damage critical plane, n represents the normal stress direction, and m represents the average, σ u represents the tensile strength, which is a fixed symbol.

[0066] According to the determined critical plane, the corresponding critical plane direction θ i , and the equivalent fatigue damage parameter on the critical plane of the i-th load to obtain the fatigue damage D i of the i-th load. If i = 1, the fatigue damage D fi of the i-th load is obtained. If i ≠ 1, the fatigue damage calculation expression of the i-th load is as follows:

[0067]

[0068] wherein, N fi represents the multi-axial constant amplitude fatigue life corresponding to the i-th load, a represents the material constant of the metal material, S eq,i represents the equivalent fatigue damage parameter on the critical plane of the i-th load, η i represents the multi-axial fatigue loading soft coefficient of the metal material of the i-th load.

[0069] The magnitude and direction of the principal stress change irregularly with the load under the multiaxial variable amplitude fatigue load. In addition, under the multiaxial fatigue load, the fatigue crack is generated on a specific plane, and both the shear stress and the normal stress on the plane affect the generation and propagation of the fatigue crack. Therefore, when the multiaxial variable amplitude fatigue life is predicted, the fatigue life of the metal material can be predicted by determining the critical plane on which the fatigue crack occurs.

[0070] Thus, the multiaxial variable amplitude fatigue damage on the critical plane of each load level is obtained according to the equivalent fatigue damage parameter on the critical plane of each load level, and then the cumulative multiaxial variable amplitude fatigue damage D on the critical plane is obtained according to the sum of the fatigue damages of all load levels.

[0071] Obtaining the fatigue life under the multiaxial variable amplitude loading condition As shown in Figure 2 , a flowchart of a method for obtaining the fatigue life of a metal material under a multiaxial variable amplitude loading condition in the embodiment is given.

[0072] Further, in order to verify the accuracy of the fatigue life prediction result of the metal material under the multiaxial variable amplitude loading condition by the scheme of the present application, the embodiment gives a comparison chart of the prediction result of the scheme of the present application and the test data in the existing literature, as shown in Figure 3 and Figure 4 , wherein, Figure 3 is a comparison chart of the fatigue life prediction result of 30CrMnSiA steel under multiaxial variable amplitude loading and the test data in the existing literature, Figure 4 is a comparison chart of the fatigue life prediction result of 2024-T4 aluminum alloy under multiaxial variable amplitude loading and the test data in the existing literature, Figure 3 The test data in is derived from the paper literature entitled Crack growth path of 30CrMnSiA steel under variable amplitude multiaxial loading published in International Journal of Fatigue, volume and issue number 2021, 153: 106502; Figure 4The experimental data in this paper are derived from the following papers: Fatigue & Fracture of Engineering Materials & Structures, Volume 2015, 38(7):838-850, titled "Study on the accumulative fatigue damage rules under multiaxial two-stage step spectra constructed by loadings with similar lives"; International Journal of Fatigue, Volume 2013, 48:257-265, titled "Comparative research on the accumulative damage rules under multiaxial block loading spectrum for 2024-T4 aluminum alloy"; and Fatigue & Fracture of Engineering Materials & Structures, Volume 2016, 39(2):194-205, titled "A novel accumulative fatigue damage model for multiaxial stepspectrum considering the variations of loading amplitude and loading path".

[0073] It should be noted that the embodiments provided in this example are... Figure 3 as well as Figure 4 The experimental data used in the above-mentioned existing papers and literature are experimental data, while the predicted data are the prediction results obtained by applying the experimental data from the existing literature to the scheme of this invention. In the attached figure, the horizontal axis represents the experimental life in the references, and the vertical axis represents the predicted life obtained in the scheme of this invention. Different symbols represent different test groups. The dashed line represents the fatigue dispersion zone, and the two types of dashed lines, from the inside to the outside, represent ±2 times the fatigue dispersion zone and ±3 times the fatigue dispersion zone, respectively. Figure 3 as well as Figure 4 As can be seen from the comparison results, the predicted results in this invention are quite close to the experimental life data in the reference. The predicted results are all distributed within ±3 times the fatigue dispersion zone, and a large number are distributed within ±2 times the fatigue dispersion zone. It can be seen that the fatigue life prediction method proposed in this invention conforms to the actual experimental results and has high accuracy and reliability.

[0074] Through the technical means provided by the present application, the performance parameters of the metal material can be obtained by only consulting the manual, so that the critical plane of the metal material is quickly determined according to the performance parameters. In the process of obtaining the fatigue life of the metal material, the influence of the load parameter on the fatigue life of the metal material is characterized by the equivalent fatigue damage parameter of each level of load, and then the combined influence of the change of the critical plane direction and the stress distribution change on the critical plane caused by the change of the load parameter in each level of load is combined, so that the multi-axial variable amplitude fatigue test under the corresponding load condition is not needed, and the multi-axial variable amplitude fatigue life of the metal material can be accurately predicted without engineering constants, which is convenient for engineering application.

[0075] The above merely describes preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for predicting the fatigue life of a multi-axis variable amplitude circuit based on a critical plane, characterized in that, include: The manual provides information on the uniaxial tensile and compressive fatigue limit, pure torsional fatigue limit, tensile yield strength, and shear strength of metallic materials. The fatigue performance parameters of metallic materials are obtained by comparing their uniaxial tensile / compressive fatigue limit and pure torsional fatigue limit. The method involves using the ratio of the uniaxial tensile / compressive fatigue limit to the pure torsional fatigue limit to determine the fatigue performance parameters of the metallic material. The static performance parameters of a metallic material are obtained based on its tensile yield strength and shear strength. The method is as follows: the static performance parameters of the metallic material are obtained based on the ratio of its shear strength to its tensile yield strength. Obtain the multiaxial fatigue loading softness coefficient of the metallic material at each load level, and determine the critical plane of the metallic material based on the multiaxial fatigue loading softness coefficient, fatigue performance parameters, and static performance parameters at each load level; including: The expression for obtaining the multiaxial fatigue loading softness coefficient of a metallic material at each load level is: ； in, Indicates the first metal material Multiaxial fatigue loading softness coefficient under level load, The shear stress amplitude on the plane, Represents the normal stress amplitude on the plane. Indicates planar direction; Based on the multiaxial fatigue loading softness coefficient of each load level for metallic materials With fatigue performance parameters and static performance parameters Compare; when When the maximum normal stress occurs, the plane of maximum normal stress is the critical plane; when At that time, the plane of maximum damage is the critical plane; At that time, the plane of maximum shear stress amplitude is the critical plane; The equivalent fatigue damage parameters on the critical plane of each load level are obtained, and the fatigue life of the metallic material under multiaxial variable amplitude loading conditions is obtained based on the equivalent fatigue damage parameters on the critical plane of each load level. The expression for obtaining the equivalent fatigue damage parameters on the critical plane of each load level is as follows: ； in, This represents the maximum normal stress on the critical plane of maximum damage. Indicates the shear stress amplitude on the plane. This represents the shear stress amplitude on the plane of maximum shear stress. Indicates the direction of normal stress. Indicates amplitude; Indicates the pure torsional fatigue limit. Indicates the uniaxial tensile and compressive fatigue limit; Indicates the first metal material Multiaxial fatigue loading softness coefficient under level load, Indicates fatigue performance parameters, Indicates static performance parameters; Indicates the first Equivalent fatigue damage parameters on the critical plane of the first-level load. Indicates equivalence; The method for obtaining the fatigue life of metallic materials under multiaxial variable amplitude loading conditions is as follows: The multiaxial amplitude fatigue damage on the critical plane is obtained based on the equivalent fatigue damage parameters on the critical plane of each load level. The fatigue life of a metallic material under multiaxial amplitude loading conditions is obtained by analyzing the multiaxial amplitude fatigue damage on the critical plane of the metallic material.

2. The multi-axis variable amplitude fatigue life prediction method based on the critical plane according to claim 1, characterized in that: The expression for obtaining the maximum normal stress on the maximum damage critical plane is: ； in, This represents the normal stress amplitude on the plane of maximum damage. This represents the average normal stress on the plane of maximum damage. Indicates the direction of normal stress. Indicates average, It represents tensile strength and is a fixed symbol.

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