Additive manufacturing aluminum alloy crystal plastic finite element modeling method and analysis method

Abstract

The application provides an additive manufacturing aluminum alloy crystal plastic finite element modeling method and an analysis method, and the method comprises the following steps: establishing an additive manufacturing aluminum alloy RVE model by using ABAQUS software; applying a boundary condition to the RVE model, setting a reference point directly above the RVE model, and applying a complete constraint to the bottom surface of the model; combining plastic constitutive relationship calibration parameters to obtain a group of material parameters that can reflect the elastic-plastic constitutive of the additive manufacturing aluminum alloy; comparing the simulation results with the experimental results to verify the applicability of the model; and on the basis of the RVE model that meets the applicability, establishing an RVE model containing defects and analyzing the stress and strain state of the RVE model. The application fully considers the influence of defects on the crystal plastic behavior, so that the modeling of the material behavior is more accurate, the interaction between the defects and the grains and the mesoscopic deformation of the grains under the cyclic load can be directly observed, and the deformation and performance of the additive manufacturing aluminum alloy under the fatigue load can be better understood.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of additive manufacturing of aluminum alloys, and particularly relates to a crystal plasticity finite element modeling method and analysis method for additive manufacturing of aluminum alloys. BACKGROUND

[0002] Additive manufacturing technology is increasingly attracting attention in the manufacturing industry, as it enables the creation of complex parts and components in a highly flexible and customized manner. This technology has been widely applied in various industries, including aerospace, medical, automotive, and energy, to meet the growing manufacturing needs.

[0003] However, although additive manufacturing has the potential to improve production efficiency and reduce material waste, it also brings new challenges. In particular, when using metal alloys for additive manufacturing, such as additive manufacturing of aluminum alloys, the understanding and modeling of crystal plasticity behavior become crucial. The performance of alloy materials is usually influenced by multiple factors such as grain structure, defects (such as inclusions or cracks), and cyclic loading. Traditional fatigue test methods are difficult to directly observe the interaction between defects and grains and the mesoscopic deformation of grains, making it difficult to study the material deformation mechanism and stress distribution in depth, resulting in insufficient understanding of material mesoscopic behavior and understanding, making it difficult to reveal the deformation behavior at the crystal level under fatigue loading, and thus failing to fully understand the influence of defects on the overall performance of the material, causing waste of test cost, thereby limiting the optimization of material design and use. SUMMARY

[0004] To solve the problems in the background art, the purpose of the present application is to provide a crystal plasticity finite element modeling method and analysis method for additive manufacturing of aluminum alloys, to solve the problem that traditional fatigue tests cannot directly observe the interaction between defects and grains and the mesoscopic deformation of grains under cyclic loading, which helps to better understand the behavior of additive manufacturing of aluminum alloys under fatigue loading, and promotes the combination and application of additive manufacturing technology and finite element technology.

[0005] To achieve the above-mentioned purpose, the first aspect of the present application provides a crystal plasticity finite element modeling method for additive manufacturing of aluminum alloys, comprising the following processes:

[0006] Step 1, using ABAQUS software to establish an RVE model of additive manufacturing of aluminum alloys;

[0007] Step 2, applying boundary conditions to the RVE model, setting a reference point directly above the RVE model, and applying complete constraints to the bottom surface of the model;

[0008] Step 3, combining plasticity constitutive relationship calibration parameters to obtain a set of material parameters that can reflect the elastoplasticity constitutive of additive manufacturing of aluminum alloys;

[0009] Step 4, the simulation results are compared with the experimental results to verify the applicability of the model; the cyclic stress-strain relationship of the additively manufactured aluminum alloy is obtained and compared with the stress-strain relationship under monotonic tension, and if the two are consistent, the RVE model is applicable to subsequent fatigue simulation calculation;

[0010] Step 5, on the basis of the RVE model in step 4 that meets the applicability, introduce a spherical hole in the model to represent the sharp protruding part of the unfused defect, and establish an RVE model containing the defect.

[0011] Preferably, the specific process of step 1 is as follows:

[0012] S11, obtain the grain size, crystal orientation and Euler angle crystallographic characteristics of the material through EBSD test;

[0013] S12, establish a cubic entity using ABAQUS software, divide it into several grains, set the node distance for dividing cells as n, and the discretization method of cells in the square entity is Lagrange method, finally obtain a square entity containing several hexahedral cells;

[0014] S13, set the type of hexahedral entity cell as C3D8 cell to realize crystal plastic finite element calculation with subprogram;

[0015] S14, select Voronoi polyhedron modeling method to establish RVE model of polycrystalline material, and generate grains with non-uniform geometric shape;

[0016] S15, obtain the grain Euler angle in the material through EBSD test, which is the angle parameter of nutation angle θ, precession angle ψ and rotation angle φ;

[0017] S16, convert the Euler angle into Miller index to express the grain orientation.

[0018] Preferably, the specific process of step 2 is as follows:

[0019] S21, set a reference point RP directly above the RVE model, completely couple the motion of the top surface of the model with the reference point, and constrain the reference point to move only along the loading direction and cannot rotate;

[0020] S22, apply complete constraint to the bottom surface of the RVE model;

[0021] S23, adjust the size and waveform of the load to simulate monotonic tension load and cyclic load respectively, to obtain monotonic tension stress-strain curve, hysteresis loop and stress-strain distribution under fatigue load.

[0022] Preferably, the specific process of step 3 is as follows:

[0023] S31, through C 11 、C12 and C 44 Three parameters are used to describe the mechanical behavior of the additive manufacturing aluminum alloy under the elastic section, and the matrix arrangement form of the three parameters is:

[0024]

[0025] The calculation formula of the three parameters is respectively:

[0026]

[0027]

[0028]

[0029] In the formula, E is the elastic modulus, v is the Poisson's ratio, and A is the Zener coefficient reflecting the degree of anisotropy of the material;

[0030] S32, adjust the yield shear stress τ0 of the material to start the slip system, and obtain the stress-strain relationship of the material;

[0031] S33, fitting the yield point data under each yield shear stress τ0, obtaining the relationship between the yield strength σ y and the yield shear stress τ0, combining the monotonic tensile test results, calculating the value of the yield shear stress τ0;

[0032] S34, changing the saturated flow stress τ s of the material to control the stress-strain relationship of the RVE model in the plastic stage;

[0033] S35, according to the observed structure of EBSD, combining the Schmidt factor value, calculating the saturated flow stress τ s value;

[0034] S36, adjusting the initial hardening modulus h0, obtaining the stress-strain relationship of the material;

[0035] S37, determining the value of the reference shear strain rate r0 and the strain rate sensitivity n of the material;

[0036] S38, using the control variable method to calibrate the above parameters, obtaining a group of material parameters which can reflect the elastoplasticity constitutive of the additive manufacturing aluminum alloy.

[0037] Preferably, the specific process of step 4 is:

[0038] S41, applying the corresponding strain rate load at the reference point, obtaining the monotonic tensile stress-strain relationship of the additive manufacturing aluminum alloy based on the crystal plasticity theory and the elastoplasticity constitutive;

[0039] S42, compare the stress-strain relationship obtained by simulation and test, and determine whether the simulation result is within the allowable error range;

[0040] S43, keep the crystal orientation information of the RVE model, the elastic-plastic constitutive material parameters, the grain division, the grid division and the boundary condition setting unchanged;

[0041] S44, apply a constant amplitude displacement load at the reference point, the load waveform is a triangular wave, the stress ratio R is 0, the strain amplitude is 0.3%, 0.6%, 0.9%, 1.2% and 1.5% respectively, and the cyclic stress-strain relationship under different strain amplitudes is obtained; a The cyclic stress-strain relationship of the additive manufacturing aluminum alloy is obtained by connecting the top points of the hysteresis loop curves under different strain amplitudes, and compared with the stress-strain relationship under monotonic tension, if the two are consistent, the RVE model is suitable for subsequent fatigue simulation calculation.

[0042] S45, connect the top points of the hysteresis loop curves under different strain amplitudes to obtain the cyclic stress-strain relationship of the additive manufacturing aluminum alloy, and compare it with the stress-strain relationship under monotonic tension, if the two are consistent, the RVE model is suitable for subsequent fatigue simulation calculation.

[0043] Preferably, the specific process of step 5 is:

[0044] Introduce a spherical hole in the RVE model verified for use in step 4 to represent the sharp protruding part of the unfused defect, and obtain the RVE model containing the defect; and re-refine the grid of the hole and the surrounding area in the RVE model containing the defect.

[0045] Preferably, the Euler angle is converted into Miller index to express the grain orientation in S16, and the conversion method is as follows:

[0046]

[0047] Wherein, <u, v, w> is the orientation parallel to the X axis; <r, s, t> is the orientation parallel to the Y axis, and the obtained (h, k, l) array is the Miller index.

[0048] The second aspect of the application provides a crystal plastic finite element modeling analysis method of additive manufacturing aluminum alloy, which is applied to the RVE model containing the defect established by the modeling method of the first aspect, and comprises the following processes:

[0049] S1, apply a sinusoidal cyclic load at the reference point of the RVE model;

[0050] S2, use the plastic strain energy density PSED as an index to evaluate whether the simulation enters a stable state, when the PSED value is stable, take the result at the maximum PSED stable time as the result of subsequent fatigue loading for analysis, and the calculation formula of PSED is:

[0051]

[0052] where Δτ is the range of shear stress variation in a certain element of the model, and Δγp is the range of plastic shear strain variation in the element;

[0053] S3, calculate the change of the maximum PSED value of different slip systems under cyclic loading, and when the maximum PSED approaches stability, the stress and strain state under the current cyclic loading is taken as the basis for subsequent analysis;

[0054] S4, analyze the distribution of local stress and local strain characteristics in the material during fatigue loading, and evaluate the influence of defects on the local stress-strain distribution of surrounding grains.

[0055] The application discloses a kind of additive manufacturing aluminum alloy crystal plastic finite element modeling method and analysis method, compared with prior art, with following beneficial effects:

[0056] (1) compared with traditional fatigue test, the present application can directly observe the interaction between defects and grains and the mesoscopic deformation problem of grains under cyclic loading, which helps better understand the deformation and performance of additive manufacturing aluminum alloy under fatigue load.

[0057] (2) the present application fully considers the influence of defects on crystal plastic behavior, making the modeling of material behavior more accurate, and can also be used to analyze multiple aspects of materials, including static and fatigue performance, grain structure and the influence of defects on material behavior.

[0058] (3) the method of the present application is not limited to specific alloys or application fields, but is a general analysis tool suitable for a variety of metal alloys and material systems, providing guidance for the corresponding technical development in other fields. BRIEF DESCRIPTION OF DRAWINGS

[0059] In order to more clearly illustrate the technical solutions of the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the following description is only one embodiment of the present application, and those skilled in the art can obtain other drawings from these drawings without creative labor.

[0060] Figure 1 is the overall flow chart of the additive manufacturing aluminum alloy crystal plastic finite element modeling and analysis method of the present application;

[0061] Figure 2 is the grain division and element division schematic diagram of the RVE model of the embodiment of the present application;

[0062] Figure 3 is the coupling setting schematic diagram of the reference point of the model of the embodiment of the present application;

[0063] Figure 4is a schematic diagram of applying complete constraint to the bottom surface of the model of the embodiment of the present application;

[0064] Figure 5 is a schematic diagram of the yield shear stress corresponding to the stress-strain relationship of the embodiment of the present application;

[0065] Figure 6 is a schematic diagram of the saturated flow stress corresponding to the stress-strain relationship of the embodiment of the present application;

[0066] Figure 7 is a schematic diagram of the initial hardening modulus corresponding to the stress-strain relationship of the embodiment of the present application;

[0067] Figure 8 is a schematic diagram of the comparison between the simulated stress-strain relationship and the test stress-strain relationship of the embodiment of the present application;

[0068] Figure 9 is a schematic diagram of the cyclic stress-strain relationship under different strain amplitudes of the embodiment of the present application;

[0069] Figure 10 is a schematic diagram of the comparison between the monotonic tensile stress-strain relationship and the cyclic mixed stress-strain relationship of the embodiment of the present application;

[0070] Figure 11 is a schematic diagram of the RVE model containing defects of the embodiment of the present application;

[0071] Figure 12 is a schematic diagram of the meshing of the RVE model containing defects of the embodiment of the present application;

[0072] Figure 13 is a schematic diagram of the sinusoidal load spectrum of the embodiment of the present application;

[0073] Figure 14 is a schematic diagram of the relationship between the maximum PSED and the cycle number on the (111) [-110] slip system of the embodiment of the present application;

[0074] Figure 15 is a schematic diagram of the relationship between the maximum PSED and the cycle number on the (111) [0 -11] slip system of the embodiment of the present application;

[0075] Figure 16 is a Mises stress cloud chart in the RVE model of the embodiment of the present application. DETAILED DESCRIPTION

[0076] The technical solutions in the specific embodiments of the present application will be described clearly and completely in combination with the drawings in the present application.

[0077] The present application provides a method for modeling and analyzing the crystal plasticity finite element of an aluminum alloy manufactured by additive manufacturing, and introduces the method of the present application by taking the aluminum alloy manufactured by additive manufacturing as an example.Figure 1 The method comprises the following steps:

[0078] Step 1: Establishing an RVE model using ABAQUS software.

[0079] Step 1.1: Obtaining the grain size, crystal orientation, and Euler angle crystallographic characteristics of the material through EBSD testing;

[0080] Step 1.2: Establishing a 0.2mm x 0.2mm x 0.2mm cubic solid using ABAQUS software, dividing it into 50 grains, and setting the node distance for dividing units to 0.01mm. The discretization method for units within the square solid is the Lagrangian method. Finally, the square solid contains 8000 hexahedral units.

[0081] Step 1.3: Setting the hexahedral unit type to C3D8 units to cooperate with the subprogram to realize crystal plastic finite element calculation;

[0082] Step 1.4: Selecting the Voronoi modeling method to establish the RVE model of the polycrystalline material and generate grains with non-uniform geometric shapes, as shown in Figure 2 ;

[0083] Step 1.5: Obtaining the grain Euler angles of the material through EBSD testing, which are the nutation angle θ, the precession angle ψ, and the rotation angle φ. Some grain Euler angles are shown in Table 1.

[0084] Table 1: Some grain Euler angles

[0085]

[0086] Step 1.6: Converting the Euler angles to Miller indices to express the grain orientation. The conversion method is as follows. The obtained (h, k, l) array is the Miller index:

[0087]

[0088] Step 2: Applying boundary conditions to the RVE model.

[0089] Step 2.1: Setting a reference point RP at 0.1mm above the model. Coupling the motion of the top surface of the model with the reference point completely, and constraining the reference point to only move in the loading direction and not to rotate. The reference coupling setting is shown in Figure 3 ;

[0090] Step 2.2: Applying complete constraints to the bottom surface of the model, as shown in Figure 4 ;

[0091] Step 2.3 Adjust the size and waveform of the load to simulate monotonic tensile load and cyclic load respectively to obtain monotonic tensile stress-strain curve, hysteresis loop and stress-strain distribution under fatigue load.

[0092] Step 3 Calibrate parameters combined with plastic constitutive relation.

[0093] Step 3.1 The mechanical behavior of additive manufacturing aluminum alloy in the elastic segment is described by three parameters, and the matrix arrangement form of the three parameters is:

[0094]

[0095] The calculation formula of the three parameters is:

[0096]

[0097]

[0098]

[0099] In the application, wherein E is the elastic modulus, based on the single point tensile result, the value is 71.63GPa; v is the Poisson's ratio, the value is 0.30; A is the Zener coefficient reflecting the anisotropy degree of the material, the value is 1.125; after calculation, C 11 = 96.43GPa, C 12 = 41.33GPa, C 44 = 31.00GPa;

[0100] Step 3.2 Adjust the yield shear stress τ0 of the material to make the slip system start to start, and obtain the stress-strain relationship of the material as shown in Figure 5

[0101] Step 3.3 Fit the yield point data under each yield shear stress τ0 to obtain the relationship between yield strength σ y and yield shear stress τ0:

[0102] σ y = 3.91τ0+38.10 (6)

[0103] Combined with the monotonic tensile test result, the yield shear stress τ0 = 46.01MPa is calculated;

[0104] Step 3.4 Change the saturated flow stress τ s to control the stress-strain relationship of the RVE model in the plastic stage as shown in Figure 6

[0105] Step 3.5 According to the observed structure of EBSD, the Schmidt factor value is 0.455, and the saturated flow stress τ​​s = 99.19 MPa;

[0106] Step 3.6 Adjust the initial hardening modulus h0, obtain the stress-strain relationship of the material as shown in Figure 7 When h0=44.37 MPa, the simulation results are in good agreement with the test results;

[0107] Step 3.7 Determine the values of the reference shear strain rate r0 and the strain rate sensitivity n of the material, after consulting the reference, determine r0=0.001 s-1 , n=5.60.

[0108] The parameters described in step 3 are calibrated by using the control variable method, and a set of material parameters that can reflect the elastoplasticity constitutive of additive manufacturing aluminum alloy are obtained, as shown in Table 2;

[0109] Table 2 Material parameters

[0110]

[0111] Step 4 Compare the simulation results with the experimental results to verify the applicability of the model.

[0112] Step 4.1 Apply a load with a strain rate of 0.01 s-1 at the reference point to obtain the monotonic tensile stress-strain relationship of additive manufacturing aluminum alloy based on crystal plasticity theory and elastoplasticity constitutive;

[0113] Step 4.2 Compare the simulation with the stress-strain relationship obtained by experiment, as shown in Figure 8 The simulation results are accurate;

[0114] Step 4.3 Keep the crystal orientation information of the RVE model, the elastoplasticity constitutive material parameters, the grain division, the mesh division and the boundary condition setting unchanged;

[0115] Step 4.4 Apply a constant amplitude displacement load at the reference point, the load waveform is a triangle wave, the stress ratio R is 0, and the strain amplitudes ε a are 0.3%, 0.6%, 0.9%, 1.2% and 1.5% respectively, and the cyclic stress-strain relationship under different strain amplitudes is obtained as shown in Figure 9 ;

[0116] Step 4.5 Connect the top points of the hysteresis loop curves under different strain amplitudes to obtain the cyclic stress-strain relationship of additive manufacturing aluminum alloy, and compare it with the stress-strain relationship under monotonic tension, as shown in Figure 10 The two are in good agreement, and the RVE model is suitable for subsequent fatigue simulation calculation;

[0117] Step 5 Establish the RVE model containing defects.

[0118] Step 5.1 Spherical voids were introduced into the RVE model to represent the sharp protrusions of the un-fused defects, with a diameter of 20 pm, as shown in Figure 11 ;

[0119] Step 5.2 The mesh of the void and surrounding area was re-refined in the RVE model containing the defect, as shown in Figure 12 .

[0120] Step 6 The effect of the defect on the local stress-strain distribution of the surrounding grains was evaluated.

[0121] Step 6.1 A sinusoidal cyclic load was applied to the reference point of the RVE model, as shown in Figure 13 ;

[0122] Step 6.2 The plastic strain energy density (PSED) was used as an indicator to evaluate whether the simulation had reached a steady state. When the PSED value was stable, the results at the maximum PSED stable time were taken as the results of subsequent fatigue loading for analysis. The calculation formula of PSED is:

[0123]

[0124] where Δτ is the change range of shear stress on a certain element of the model, and Δγ p is the change range of plastic shear strain of the element;

[0125] Step 6.3 The maximum PSED value on the (1 1 1) [-1 1 0] slip system was calculated, which showed an overall upward trend with the increase of cycle number, as shown in Figure 14 ; On the (1 1 1) [0 -1 1] slip system, the maximum PSED showed a downward trend with the increase of cycle number, as shown in Figure 15 ; When the cycle number exceeded 20, the maximum PSED on both slip systems tended to be stable. Based on this result, the stress and strain state of the additive manufacturing aluminum alloy at the 20th cycle loading was taken as the basis for subsequent analysis;

[0126] Step 6.4 After 20 cycles of loading, the Mises stress in the RVE model was as shown in Figure 16 ; After the cyclic load, the Mises stress in the material showed a non-uniform distribution, and there was a certain difference in the stress level in different grains.

[0127] The application provides a crystal plastic finite element modeling method and an analysis method for additive manufacturing of aluminum alloy considering defects, solves the problem that the traditional fatigue test cannot directly observe the interaction between defects and grains and the mesoscopic deformation of grains under cyclic loading, and helps better understand the deformation and performance of the additive manufacturing aluminum alloy under the fatigue load, thereby providing deeper insights and guidance for part design and manufacturing.

[0128] The above description in connection with the accompanying drawings adequately illustrates the specific embodiments of the present application so that those skilled in the art can practice them. Parts and features of some embodiments can be included or replaced by parts and features of other embodiments. The scope of the embodiments of the present application includes the entire scope of the claims, and all available equivalents of the claims. In the present application, the terms "first", "second", etc. are only used to distinguish one element from another, without requiring or implying any actual relationship or order between the elements. In fact, the first element can also be referred to as the second element, and vice versa. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that a structure, device or apparatus including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such structure, device or apparatus. Without more limitations, the element defined by the phrase "including a" does not exclude the presence of additional identical elements in the structure, device or apparatus including the element. Various embodiments are described in a progressive manner, each focusing on the differences from other embodiments, and the same or similar parts between various embodiments can be referred to each other.

[0129] The above description is only the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0130] Although the specific embodiments of the present application have been described above, they are not intended to limit the scope of protection of the present application, and those skilled in the art should understand that various modifications or changes made by those skilled in the art on the basis of the technical solutions of the present application without creative labor are still within the protection scope of the present application.

Claims

1. A finite element method for additive manufacturing of aluminum alloy crystal plasticity, characterized in that, The process includes the following: Step 1: Use ABAQUS software to create an additive manufacturing RVE model of the aluminum alloy; Step 2: Apply boundary conditions to the RVE model. Establish a reference point directly above the RVE model and apply full constraints to the bottom surface of the model. The specific process is as follows: S21, set a reference point RP directly above the RVE model, fully couple the motion of the top surface of the model with the reference point, and constrain the reference point to only move along the loading direction and not to rotate. S22, apply full constraints to the bottom surface of the RVE model; S23, adjust the magnitude and waveform of the load to simulate monotonic tensile load and cyclic load respectively, in order to obtain monotonic tensile stress-strain curve, hysteresis loop and stress-strain distribution under fatigue load. Step 3: Combining the calibration parameters with the plastic constitutive relation, a set of material parameters that can reflect the elastoplastic constitutive structure of additively manufactured aluminum alloys is obtained; the specific process is as follows: S31, via C 11 C 12 and C 44 Three parameters are used to describe the mechanical behavior of additively manufactured aluminum alloys in the elastic segment. The matrix arrangement of the three parameters is as follows: The calculation formulas for the three parameters are as follows: In the formula, E is the elastic modulus, ν is Poisson's ratio, and A is the Zener coefficient, which reflects the degree of anisotropy of the material. S32, Adjusting the yield shear stress of the material τ 0 initiates the slip system, allowing the stress-strain relationship of the material to be obtained; S33, for each yield shear stress τ The yield strength is obtained by fitting the yield point data at 0°C. σ y With yield shear stress τ Based on the relationship between 0 and 0, and combined with the results of monotonic tensile tests, the yield shear stress is calculated. τ The value of 0; S34, changing the saturated flow stress of the material τ s To control the stress-strain relationship of the RVE model during the plastic stage; S35 calculates the saturated flow stress based on the EBSD observation structure and the Schmidt factor value. τ s value; S36, Adjust initial hardening modulus h 0, obtain the stress-strain relationship of the material; S37, Determine the reference shear strain rate of the material. With strain rate sensitivity n The value; S38. The above parameters are calibrated using the controlled variable method to obtain a set of material parameters that can reflect the elastic-plastic constitutive structure of additively manufactured aluminum alloys. Step 4: Compare the simulation results with the experimental results to verify the applicability of the model; calculate the cyclic stress-strain relationship of additively manufactured aluminum alloys and compare it with the stress-strain relationship under monotonic tension. If the two are consistent, the RVE model is suitable for subsequent fatigue simulation calculations. Step 5: Based on the applicable RVE model from Step 4, introduce spherical holes into the model to represent the sharp protrusions of the unfused defects, and establish an RVE model that includes the defects.

2. The additive manufacturing aluminum alloy crystal plastic finite element modeling method as described in claim 1, characterized in that, The specific process of step 1 is as follows: S11, the grain size, crystal orientation and Euler angle crystallographic characteristics of the material were obtained by EBSD testing; S12, a cubic solid is constructed using ABAQUS software, divided into several grains, with the node distance for dividing the unit set to n. The discretization method for the unit within the square solid is the Lagrange method, and the final square solid contains several hexahedral units. S13, the hexahedral solid element type is set to C3D8 element to cooperate with the subroutine to realize crystal plasticity finite element calculation; S14, Select the Voronoi polyhedron modeling method to establish the RVE model of the polycrystalline material and generate grains with non-uniform geometry; S15, the Euler angles of the material grains obtained by EBSD testing are nutation angle θ, precession angle ψ and spin angle φ; S16 converts Euler angles into Miller indices to express grain orientation.

3. The additive manufacturing aluminum alloy crystal plastic finite element modeling method as described in claim 1, characterized in that, The specific process of step 4 is as follows: S41, by applying a load with a corresponding strain rate at the reference point, the monotonic tensile stress-strain relationship of the additive manufacturing aluminum alloy based on crystal plasticity theory and elastoplastic constitutive model is obtained. S42, compare the stress-strain relationship obtained from simulation and experiment to determine whether the simulation results are within the allowable error range; S43, keep the crystal orientation information, elastoplastic constitutive material parameters, grain division, mesh division and boundary condition settings of the RVE model unchanged; S44, a constant amplitude displacement load is applied at the reference point. The load waveform is a triangular wave, and the stress ratio is... R=0 strain amplitude ε a The cyclic stress-strain relationships under different strain amplitudes were obtained by using 0.3%, 0.6%, 0.9%, 1.2%, and 1.5%, respectively. S45. Connect the vertices of the hysteresis loop curves under different strain amplitudes to obtain the cyclic stress-strain relationship of the additively manufactured aluminum alloy. Compare it with the stress-strain relationship under monotonic tension. If the two match, the RVE model is suitable for subsequent fatigue simulation calculations.

4. The additive manufacturing aluminum alloy crystal plastic finite element modeling method as described in claim 1, characterized in that, The specific process of step 5 is as follows: Introduce a spherical hole into the RVE model used in step 4 to represent the sharp protrusion of the unfused defect, and obtain an RVE model containing the defect; then refine the mesh of the hole and the surrounding area within the RVE model containing the defect.

5. The additive manufacturing aluminum alloy crystal plastic finite element modeling method as described in claim 2, characterized in that, In S16, Euler angles are converted into Miller indices to express grain orientation. The conversion method is as follows: in, <u, v, w> Orientation parallel to the X-axis; <r, s, t> For an orientation parallel to the Y-axis, the resulting (h, k, l) The array is the Miller index.

6. A finite element modeling and analysis method for the plasticity of additively manufactured aluminum alloy crystals, characterized in that, Applied to a defect-containing RVE model established by the modeling method as described in any one of claims 1 to 5, and comprising the following procedures: S1, apply a sinusoidal cyclic load at the reference point of the RVE model; S2 uses the plastic strain energy density (PSED) as an indicator to evaluate whether the simulation has entered a steady state. Once the PSED value stabilizes, the result at the stable moment of the maximum PSED is taken to represent the result of subsequent fatigue loading for analysis. The formula for calculating PSED is: Where Δτ is the range of shear stress variation on a certain element of the model, and Δγp is the range of plastic shear strain variation of that element; S3, calculate the change of the maximum PSED value of different slip systems under cyclic loading. When the maximum PSED approaches stability, the stress and strain state under the current cyclic loading is used as the basis for subsequent analysis. S4. Analyze the distribution of local stress and local strain characteristics within the material during fatigue loading, and evaluate the impact of defects on the local stress-strain distribution of surrounding grains.

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