Multi-axial fatigue prediction method based on normal and shear strain energy coupling and medium

Abstract

The invention relates to a multi-axial fatigue prediction method and medium based on non-linear coupling of normal and shear strain energy, and the method comprises the steps: calculating the normal strain and tangential strain of each group of experimental results at each angle under a loaded condition by using the fatigue experimental results of a to-be-predicted material, finding out the plane where the maximum shear strain amplitude of the maximum normal strain is located, and calculating the maximum shear strain amplitude of the maximum normal strain; taking as a critical surface; calculating each stress-strain component on the critical surface; acquiring material and shear performance parameters of a to-be-predicted material, and predicting by adopting the fatigue prediction model in combination with each stress-strain component; the model building process comprises the following steps: performing nonlinear coupling on normal strain energy and shear strain energy, obtaining a fatigue damage parameter by combining an average normal stress correction coefficient and an average tangential stress sensitivity coefficient, and obtaining a fatigue prediction model by combining the fatigue damage parameter with a fatigue damage equation in a shear form. Compared with the prior art, the method has the advantages of being high in fatigue life prediction precision, suitable for proportional and non-proportional loading, high in safety and the like.

Description

Technical Field

[0001] This invention relates to the field of multiaxial fatigue life prediction technology, and in particular to a multiaxial fatigue prediction method and medium based on the coupling of normal and shear strain energy. Background Technology

[0002] In practical applications, engineering structures often bear complex loads, and fatigue failure is one of the main failure modes. Therefore, research on fatigue failure and life prediction methods has significant practical implications. Most existing fatigue life prediction methods can be categorized into: equivalent stress / strain method, energy density method, and critical surface method. Among these methods, the critical surface method considers the mechanism of crack initiation and propagation, possesses certain physical significance, and is considered an effective method for fatigue life prediction. It has been widely discussed, researched, and expanded, especially the combination of critical surface parameters and the energy method, resulting in prediction models with high accuracy and certain physical significance.

[0003] For example, the invention with publication number CN107506535A discloses a multiaxial fatigue life prediction method based on critical strain damage parameters, which is applied to the field of multiaxial fatigue life prediction. It obtains a life prediction model by using shear strain and normal strain damage on the maximum damage parameter plane near the maximum shear strain plane and using different shear and normal stress correction factors. The plane near the shear strain plane is used as a candidate critical plane, and the plane where the maximum damage is located is selected as the critical plane.

[0004] Under disproportionate loads on engineering structures, the rotation of the principal strain axis causes additional strengthening of the material, leading to a shortened fatigue life—a phenomenon known as disproportionate strengthening. Simultaneously, under asymmetric loading conditions, the mean normal tensile stress is generally considered to accelerate crack initiation and propagation, reducing fatigue life. Conversely, the mean normal compressive stress helps suppress the initiation and propagation of fatigue cracks, thus increasing the fatigue life of the structure under the same stress amplitude. Furthermore, experiments have shown that for certain metallic materials, the mean shear stress has a significant impact on fatigue life. Therefore, it is necessary to comprehensively consider the influence of multiple factors on fatigue damage, while avoiding the limitations of a simple linear combination of shear energy and tensile energy, to improve the accuracy of fatigue damage prediction and enhance the accuracy and safety of fatigue life prediction. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology by providing a multiaxial fatigue prediction method and medium based on the nonlinear coupling of normal and shear strain energy. By combining the critical surface method and the energy method, it avoids the limitations of simple linear superposition of shear strain energy density and normal strain energy density, as well as the influence of normal and shear mean stress on fatigue damage, thereby improving the accuracy and safety of life prediction.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A multiaxial fatigue prediction method based on nonlinear coupling of normal and shear strain energy, the method comprising:

[0008] Using the fatigue test results of the material to be predicted, the normal strain and tangential strain of each set of test results at various angles under load are calculated, and the plane containing the maximum shear strain amplitude of the maximum normal strain is found as the critical plane.

[0009] Calculate each stress and strain component on the critical surface, including the normal and tangential stress and strain amplitudes, and the mean values ​​of normal and tangential stresses on the critical surface;

[0010] The material and shear property parameters of the material to be predicted are obtained by consulting material handbooks or conducting uniaxial tensile and torsional fatigue tests. These material and shear property parameters include the material yield stress σ. y Shear modulus G, shear fatigue strength coefficient τ′ f Shear fatigue strength index b0, shear fatigue ductility index γ′ f The fatigue prediction model is used to predict the life of the material under test by combining the shear fatigue ductility index c0 with the stress and strain components on the critical surface and the pre-established fatigue prediction model.

[0011] The process of establishing the fatigue prediction model includes: nonlinearly coupling the normal and shear strain energies, and combining the average normal stress correction coefficient and the average tangential stress sensitivity coefficient to obtain the calculation expression of the fatigue damage parameters; combining the fatigue damage parameters with the shear form of the Basquin and Manson-Coffin equations to obtain the fatigue prediction model.

[0012] Furthermore, the calculation expression for the nonlinear coupling of the normal and shear strain energy is as follows:

[0013]

[0014] In the formula, D′ is the damage parameter obtained by nonlinearly coupling the normal and shear strain energy. The normal stress amplitude on the critical surface. The normal strain amplitude on the critical surface. This represents the maximum shear strain amplitude on the critical surface. Let |τ be the tangential stress amplitude on the critical surface. m | represents the absolute value of the mean tangential stress on the critical surface.

[0015] Furthermore, the average normal stress correction factor is:

[0016]

[0017] In the formula, α is the average normal stress correction factor, and σ m σ is the average normal stress on the critical surface. y The yield stress of the material;

[0018] The expression for the tangential stress sensitivity coefficient is:

[0019]

[0020] In the formula, k is the tangential stress sensitivity coefficient. Predicting fatigue life under symmetrical cyclic pure shear conditions. For predicting fatigue life under asymmetric cyclic pure shear, n is the number of experiments required.

[0021] Under the same loading conditions, the calculation expressions for the predicted fatigue life under the asymmetric cyclic pure shear mode and the predicted fatigue life under the symmetric cyclic pure shear mode are as follows:

[0022]

[0023] In the formula, τ′ f γ′ represents the shear fatigue strength coefficient. f denoted by , b0 represents the shear fatigue ductility coefficient, c0 represents the shear fatigue strength index, and G represents the shear modulus.

[0024] Furthermore, the fatigue damage parameter combines the normal stress amplitude in the nonlinear coupling part of normal and shear strain with the average normal stress correction coefficient, and combines the mean shear stress term with the tangential stress sensitivity coefficient. The corresponding calculation expression is:

[0025]

[0026] In the formula, D is the fatigue damage parameter of nonlinear coupling between normal and shear strain energy and mean stress effect.

[0027] Furthermore, during the total anti-torsional loading process of the material to be predicted, the parameters of the critical surface satisfy: Δσ n =0, Δε n =0, Δγ max =Δγ n , τ m =0;

[0028] Combining the parameters of the critical surface with the fatigue damage parameters, the resulting calculation expression is:

[0029]

[0030] In the formula, Δγn f(N) represents the shear stress amplitude on the critical surface. f ) is a function related to fatigue life, N f This refers to fatigue life.

[0031] Furthermore, for a completely reversed constant-amplitude torsional load, the expressions for the shear form of the Basquin and Manson-Coffin equations are as follows:

[0032]

[0033] Furthermore, the rewritten expression of the fatigue damage parameter, combined with the shear form of the Basquin and Manson-Coffin equations, yields the following damage function expression:

[0034]

[0035] Furthermore, by combining the nonlinear coupling of normal and shear strain energy with the fatigue damage parameters and damage function of mean stress effect, the calculation expression of the fatigue prediction model is obtained as follows:

[0036]

[0037] Furthermore, the method is used for fatigue life prediction of metallic materials in the field of aerospace technology.

[0038] The present invention also provides a computer-readable storage medium including a program executable by a processor of an electronic device, the program including methods described above.

[0039] Compared with the prior art, the beneficial effects of the present invention include:

[0040] 1. In calculating damage parameters, this invention first considers the limitations of a simple linear combination of shear strain energy density and normal strain energy density, and nonlinearly couples the normal and shear strain energies, which is more in line with the fatigue failure mechanism and improves the accuracy of life prediction results.

[0041] This invention further considers the differences in the impact of mean normal stress on the fatigue life of different materials and the different effects of mean tangential stress on fatigue damage under different loading paths. A mean normal stress correction coefficient is introduced into the normal stress amplitude component of the damage parameters, and a tangential stress sensitivity coefficient is introduced into the mean shear stress term. This yields damage parameters that quantify the nonlinear coupling of normal-shear strain energy and the mean stress effect, thus quantifying the correlation between material deformation characteristics and damage modes and enhancing universality. Simultaneously, using the absolute value of the mean tangential stress and its sensitivity coefficient to consider the impact of mean shear stress on fatigue damage enables more accurate fatigue life prediction, significantly improving the reliability of life prediction in complex load scenarios such as aerospace and energy equipment.

[0042] 2. This invention defines the plane containing the maximum shear strain amplitude with the maximum normal strain as the maximum damage surface, i.e., the critical surface. It can comprehensively consider the fatigue damage mechanism, more comprehensively evaluate the fatigue damage of materials, determine material parameters by consulting material handbooks, achieve efficient and accurate fitting of material parameters, and is relatively easy to operate with low implementation cost. Attached Figure Description

[0043] Figure 1 This is a flowchart illustrating a multiaxial fatigue prediction method with nonlinear coupling of normal and shear strain energy provided in an embodiment of the present invention.

[0044] Figure 2 This is a fatigue test loading path diagram provided in an embodiment of the present invention;

[0045] Figure 3 This is a comparison chart of fatigue life prediction results and experimental results for a multiaxial fatigue prediction method with nonlinear coupling of normal and shear strain energy provided in an embodiment of the present invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0047] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0048] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0049] Example 1

[0050] This embodiment provides a multiaxial fatigue prediction method based on the nonlinear coupling of normal and shear strain energy, which uses the fatigue test results of IN-718 material to predict the fatigue life, including the following steps:

[0051] Obtain the fatigue test results of the material to be predicted, and calculate... Figure 2 For each experimental result under the loading path shown, the normal strain and tangential strain at each angle are used to find the plane containing the maximum shear strain amplitude with the maximum normal strain, which is taken as the critical plane.

[0052] Calculate each stress and strain component on the critical surface, including the normal and tangential stress and strain amplitudes, and the mean values ​​of normal and tangential stresses on the critical surface;

[0053] The material and shear property parameters of the material to be predicted are obtained by consulting material handbooks or conducting uniaxial tensile and torsional fatigue tests. These material and shear property parameters include the material yield stress σ. y Shear modulus G, shear fatigue strength coefficient τ′ f Shear fatigue strength index b0, shear fatigue ductility index γ′ f The fatigue prediction model is used to predict the life of the material by combining the shear fatigue ductility index c0 with the stress and strain components on the critical surface and the pre-established fatigue prediction model.

[0054] The process of establishing the fatigue prediction model includes: nonlinearly coupling the normal and shear strain energies, and combining the average normal stress correction coefficient and the average tangential stress sensitivity coefficient to obtain the calculation expression of the fatigue damage parameters; combining the fatigue damage parameters with the shear form of the Basquin and Manson-Coffin equations to obtain the fatigue prediction model.

[0055] like Figure 1 As shown, in this embodiment, the process of establishing the fatigue prediction model includes the following steps:

[0056] S1: The strain energy density is the product of the stress amplitude and the corresponding strain amplitude; based on the different effects of normal and shear strain energy on fatigue life, a nonlinear coupling damage parameter between normal and shear strain energy is established.

[0057] Specifically, fatigue cracks typically initiate in the local plastic zone of the slip band. Fatigue crack growth is a coalescence process along the shear band at the crack tip. Normal strain and normal stress on the crack surface accelerate this coalescence and contribute to fatigue crack growth.

[0058] It is generally believed that positive mean normal stress reduces fatigue life, while negative mean normal stress has a beneficial effect on fatigue life. The maximum normal stress contains the peak value of the normal stress during loading, and the influence of the mean normal stress is reflected in the maximum normal stress value. A positive mean normal stress increases the maximum normal stress, thus accelerating fatigue damage; conversely, a negative mean normal stress results in a relatively smaller maximum stress, weakening its promoting effect on fatigue damage. Therefore, the maximum normal stress can reflect the influence of mean normal stress on fatigue damage. However, regardless of whether it is positive or negative, the mean tangential stress has a detrimental effect on fatigue life. Therefore, the maximum tangential stress is not suitable for reflecting the influence of mean tangential stress on fatigue damage; hence, the absolute value of the mean tangential stress is directly used as the damage parameter. To avoid the limitations of simple linear combinations, the damage parameter is obtained by nonlinearly coupling the normal and shear strain energy as follows:

[0059]

[0060] In the formula, D′ is the damage parameter obtained by nonlinearly coupling the normal and shear strain energy. The normal stress amplitude on the critical surface. The normal strain amplitude on the critical surface. This represents the maximum shear strain amplitude on the critical surface. Let |τ be the shear stress amplitude on the critical surface. m | represents the absolute value of the mean shear stress on the critical surface;

[0061] S2: Establish the average normal stress correction factor and the tangential stress sensitivity factor;

[0062] Specifically, to account for the varying effects of mean normal stress on the fatigue life of different materials, the yield strength of the material is used to correct the influence of mean normal stress on fatigue damage. Yield strength is an inherent property of materials; different yield strengths mean different levels of ease with which plastic deformation occurs, leading to differences in crack propagation and thus affecting fatigue life. The consensus is that tensile stress promotes plastic deformation and reduces fatigue life, while compressive stress inhibits plastic deformation and improves fatigue life. Therefore, the mean normal stress correction factor is constructed as follows:

[0063]

[0064] In the formula, α is the average normal stress correction factor, and σ m σ is the average normal stress on the critical surface. y The yield stress of the material;

[0065] Specifically, by setting up control groups for symmetrical and asymmetrical pure torsional loading fatigue experiments, in Figure 2 In the loading paths B and E shown, each group uses the average shear stress as the sole variable. The impact of average shear stress on fatigue life can be intuitively observed from the fatigue test data. Since the degree of harm caused by tangential average stress varies for different materials, to quantify the degree of harm, the ratio of fatigue test life under asymmetric pure torsion loading to symmetric pure torsion loading is used. This ratio changes with the material's sensitivity to average shear stress. To consider cost, predicted fatigue life is used instead of experimental fatigue life. Although there is an error between predicted and experimental fatigue life, the ratio still reflects the material's sensitivity to shear stress and avoids the randomness of experimental fatigue life. Therefore, describing shear stress sensitivity using the ratio of predicted fatigue life under symmetric and asymmetric cycles is reasonable. The shear stress sensitivity coefficient is constructed as follows:

[0066]

[0067] In the formula, k is the tangential stress sensitivity coefficient. For predicting fatigue life under symmetrical cyclic pure shear, The predicted fatigue life under asymmetric cyclic pure shear is given by formula (4), and the predicted fatigue life under symmetric cyclic pure shear under the same loading conditions is given by formula (5).

[0068]

[0069] In the formula, τ′ f γ′ represents the shear fatigue strength coefficient. f denoted by b0, which represents the shear fatigue ductility coefficient; b0 represents the shear fatigue strength index; c0 represents the shear fatigue ductility index; and G represents the shear modulus.

[0070] S3: Combining steps S1 and S2, establish fatigue damage parameters based on nonlinear coupling of normal-shear strain energy and mean stress effect;

[0071] Specifically, by combining equation (1) with the Poisson's ratio correlation factor and the mean shear stress sensitivity coefficient, the damage parameters of the nonlinear coupling between normal-shear strain energy and the mean stress effect are established as follows:

[0072]

[0073] In the formula, D is the fatigue damage parameter of nonlinear coupling between normal and shear strain energy and mean stress effect;

[0074] S4: Combine the fatigue damage parameters obtained in step S3 with the shear form of the Basquin and Manson-Coffin equations to construct a fatigue damage model in the form of Basquin-Manson-Coffin.

[0075] Specifically, during the full-reverse constant-amplitude uniaxial loading process of the material sample to be predicted, the parameters of the critical surface satisfy the following equation:

[0076]

[0077] Δγ max =Δγ n (8)

[0078]

[0079] τ m =0 (10)

[0080] Combining equations (7) to (10) with equation (6), the calculation expression for the fatigue damage parameters is rewritten as follows:

[0081]

[0082] In the formula, Δγ n f(N) represents the shear stress amplitude on the critical surface. f ) is a function related to fatigue life, N f For fatigue life;

[0083] For a completely reversed constant-amplitude torsional load, the expressions for the shear form of the Basquin and Manson-Coffin equations are as follows:

[0084]

[0085] Combining equations (12), (13) with (11), we can obtain:

[0086]

[0087] The proposed fatigue life prediction model can be rewritten as follows:

[0088]

[0089] S5: According to the critical plane rule, the critical plane is defined as the plane containing the maximum shear strain amplitude with the maximum normal strain, and the stress-strain components on the critical plane are calculated.

[0090] Specifically, fatigue cracks form along the direction of the plane of maximum shear strain and then propagate approximately along the normal strain direction of that plane. This means that the plane of maximum shear strain and the normal strain play crucial roles in the initiation and propagation of fatigue cracks. Therefore, defining the maximum shear plane with the maximum normal strain as the critical surface can more accurately reflect the actual situation of fatigue damage.

[0091] Under non-proportional cyclic loading conditions, the phase difference between loads affects the fatigue life of materials. The normal strain range on the plane of maximum shear strain increases with the increase of the phase difference, while the multiaxial fatigue life tends to decrease with the increase of the phase difference between loads. Using the normal strain range and normal stress range on the plane of maximum shear strain as multiaxial damage parameters can reflect the fact that the multiaxial fatigue life decreases with the increase of the phase difference between loads.

[0092] Using the plane containing the maximum shear strain amplitude with the maximum normal strain as the critical plane allows for a more comprehensive assessment of fatigue damage mechanisms and a more complete evaluation of material fatigue damage. Therefore, the plane containing the maximum shear strain amplitude with the maximum normal strain is defined as the maximum damage plane, i.e., the critical plane. The normal and tangential stress-strain amplitudes, the maximum and minimum normal stresses, and the mean tangential stresses on the critical plane are calculated.

[0093] The normal and tangential strains at each angle are calculated using equations (16) and (17). The plane containing the maximum shear strain amplitude of the maximum normal strain is the maximum damage surface, i.e., the critical surface. The normal and tangential stress-strain amplitudes, maximum normal stress, and mean tangential stress on the critical surface are calculated.

[0094]

[0095] In the formula, υ eff The effective Poisson ratio is calculated using the effective Poisson ratio method proposed by Wang-Brown, formula (18). To simplify the calculation process, the effective Poisson ratio can be approximated to 0.5.

[0096]

[0097] In the formula, υ e Δσ is the elastic Poisson's ratio; E is the elastic modulus; Δσ eq The equivalent stress range; Δε eq This is the equivalent variation range;

[0098] S6: Determine the material and shear performance parameters according to the material handbook, and predict the life based on the proposed fatigue prediction model;

[0099] Specifically, by consulting the material handbook, the yield strength σ of the material can be determined. y Shear modulus G, shear fatigue strength coefficient τ′ fShear fatigue strength index b0, shear fatigue ductility coefficient γ′ f The shear fatigue ductility index is shown in Table 1. Fatigue prediction was performed using the model for 15 load path pairs, such as... Figure 2 As shown, the lifetime prediction results are as follows: Figure 3 As shown.

[0100] Table 1 Material Parameters

[0101] G / GPa <![CDATA[σ y / MPa]]> <![CDATA[τ′ f / MPa]]> <![CDATA[γ′ f / %]]> <![CDATA[b0]]> <![CDATA[c0]]> 82.8 510 1030 3.62 -0.074 -0.778

[0102] This embodiment also provides a computer-readable storage medium including a program executable by a processor of an electronic device, the program including methods described above.

[0103] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multiaxial fatigue prediction method based on nonlinear coupling of normal and shear strain energy, characterized in that, The method includes: Using the fatigue test results of the material to be predicted, the normal strain and tangential strain of each set of test results at various angles under load are calculated, and the plane containing the maximum shear strain amplitude of the maximum normal strain is found as the critical plane. Calculate each stress and strain component on the critical surface, including the normal and tangential stress and strain amplitudes, and the mean values ​​of normal and tangential stresses on the critical surface; The material and shear property parameters of the material to be predicted are obtained by consulting material handbooks or conducting uniaxial tensile and torsional fatigue tests. These material and shear property parameters include the material yield stress σ. y Shear modulus G, shear fatigue strength coefficient τ′ f Shear fatigue strength index b0, shear fatigue ductility index γ′ f The fatigue prediction model is used to predict the life of the material under test by combining the shear fatigue ductility index c0 with the stress and strain components on the critical surface and the pre-established fatigue prediction model. The process of establishing the fatigue prediction model includes: nonlinearly coupling the normal and shear strain energies, and combining the average normal stress correction coefficient and the average tangential stress sensitivity coefficient to obtain the calculation expression of the fatigue damage parameters; combining the fatigue damage parameters with the shear form of the Basquin and Manson-Coffin equations to obtain the fatigue prediction model.

2. The multiaxial fatigue prediction method based on nonlinear coupling of normal and shear strain energy according to claim 1, characterized in that, The calculation expression for nonlinearly coupling the normal and shear strain energy is as follows: In the formula, D′ is the damage parameter obtained by nonlinearly coupling the normal and shear strain energy. The normal stress amplitude on the critical surface. The normal strain amplitude on the critical surface. This represents the maximum shear strain amplitude on the critical surface. Let |τ be the tangential stress amplitude on the critical surface. m | represents the absolute value of the mean tangential stress on the critical surface.

3. The multiaxial fatigue prediction method based on nonlinear coupling of normal and shear strain energy according to claim 1, characterized in that, The average normal stress correction factor is: In the formula, α is the average normal stress correction factor, and σ m σ is the average normal stress on the critical surface. y The yield stress of the material; The expression for the tangential stress sensitivity coefficient is: In the formula, k is the tangential stress sensitivity coefficient. is the predicted fatigue life under the symmetrical cyclic pure shear form, and is the predicted fatigue life under the asymmetric cyclic pure shear form, where n is the number of experiments required. Under the same loading conditions, the calculation expressions for the predicted fatigue life under the asymmetric cyclic pure shear mode and the predicted fatigue life under the symmetric cyclic pure shear mode are as follows: In the formula, τ′ f γ′ represents the shear fatigue strength coefficient. f denoted by , b0 represents the shear fatigue ductility coefficient, c0 represents the shear fatigue strength index, and G represents the shear modulus.

4. The multiaxial fatigue prediction method based on nonlinear coupling of normal and shear strain energy according to claim 2, characterized in that, The fatigue damage parameter combines the normal stress amplitude in the nonlinear coupling component of normal and shear strain with the average normal stress correction coefficient, and combines the mean shear stress term with the shear stress sensitivity coefficient. The corresponding calculation expression is as follows: In the formula, D is the fatigue damage parameter of nonlinear coupling between normal and shear strain energy and mean stress effect, α is the average normal stress correction coefficient, and k is the tangential stress sensitivity coefficient.

5. The multiaxial fatigue prediction method based on nonlinear coupling of normal and shear strain energy according to claim 4, characterized in that, During the full-reverse constant-amplitude pure torsion loading process of the material to be predicted, the parameters of the critical surface satisfy: Δσ n =0, Δε n =0, Δγ max =Δγ n , τ m =0; Combining the parameters of the critical surface with the fatigue damage parameters, the resulting calculation expression is: In the formula, Δγ n f(N) represents the shear stress amplitude on the critical surface. f ) is a function related to fatigue life, N f This refers to fatigue life.

6. The multiaxial fatigue prediction method based on nonlinear coupling of normal and shear strain energy according to claim 5, characterized in that, For a completely inverted constant-amplitude torsional load, the expressions for the shear form of the Basquin and Manson-Coffin equations are as follows: In the formula, τ′ f γ′ is the shear fatigue strength coefficient. f denoted as the shear fatigue ductility coefficient, b0 as the shear fatigue strength exponent, c0 as the shear fatigue ductility exponent, and G as the shear modulus.

7. The multiaxial fatigue prediction method based on nonlinear coupling of normal and shear strain energy according to claim 5, characterized in that, The rewritten expression for the fatigue damage parameter, combined with the shear form of the Basquin and Manson-Coffin equations, yields the following damage function expression:

8. The multiaxial fatigue prediction method based on nonlinear coupling of normal and shear strain energy according to claim 7, characterized in that, By combining the nonlinear coupling of normal and shear strain energy with the fatigue damage parameters and damage function of mean stress effect, the calculation expression of the fatigue prediction model is obtained as follows:

9. The multiaxial fatigue prediction method based on nonlinear coupling of normal and shear strain energy according to claim 1, characterized in that, The method is used for predicting the fatigue life of metallic materials in the field of aerospace technology.

10. A computer-readable storage medium comprising a program executable by a processor of an electronic device, the program including methods for performing the method as claimed in any one of claims 1-9.

Images