A method for establishing a lattice structure homogenization elastoplastic dynamic constitutive model
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
- Filing Date
- 2026-04-16
- Publication Date
- 2026-08-07
AI Technical Summary
[0003]发明目的：本发明提供一种点阵结构均质化弹塑性动态本构模型的建立方法，用以解决工程应用中针对大尺寸点阵结构件开展动态冲击数值仿真时网格数量多，计算资源消耗大的技术问题
[0027]Beneficial effects: In traditional mesoscopic finite element modeling, the unit cell of a lattice structure often requires discretization by thousands or even tens of thousands of finite element elements. This invention, however, uses a single finite element to characterize the equivalent mechanical response of the lattice structure unit cell in numerical simulation and introduces a description of the strain rate strengthening effect. Therefore, this method can significantly reduce the mesh size required for the model, thereby reducing computational overhead, saving computational resources, and effectively improving numerical computation efficiency.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid mechanics, specifically relating to a method for establishing a homogeneous elastoplastic dynamic constitutive model of a lattice structure. Background Technology
[0002] With the widespread application of additive manufacturing technology in high-end fields such as aerospace, the number of large components manufactured using lattice structures is increasing. These structures typically contain a considerable number of lattice structural unit cells. With the development of computational mechanics, the finite element method (FEM) can obtain structural response information, such as internal interaction mechanisms and energy absorption characteristics, that is difficult to obtain directly through traditional experiments, while reducing experimental costs. However, numerical simulation of large-scale components composed of numerous lattice structural unit cells faces significant challenges: accurate description of the unit cell mechanical behavior requires fine meshes, leading to a large overall model size and stringent computational resource requirements. Therefore, macroscopic equivalent methods for predicting the overall mechanical properties of lattice structures and establishing homogeneous constitutive models of lattice structures are of profound significance. Existing homogeneous constitutive models are mostly based on uniaxial compression data, focusing on the calibration of equivalent Young's modulus and initial yield strength; however, there are few results regarding subsequent yield evolution after initial yielding, strain hardening laws, and dynamic equivalent performance. Lattice-filled components often experience complex dynamic loads and significant plastic deformation during service; therefore, macroscopic models must be able to accurately characterize the plastic response under high strain rate and multiaxial stress conditions. Therefore, developing a homogeneous elastoplastic dynamic constitutive model for lattice structures applicable to engineering is the key and the difficult point of the problem. Summary of the Invention
[0003] Purpose of the invention: This invention provides a method for establishing a homogenized elastoplastic dynamic constitutive model of a lattice structure, in order to solve the technical problem of large mesh number and high computational resource consumption when conducting dynamic impact numerical simulation of large-size lattice structural components in engineering applications.
[0004] Technical Solution: The method for establishing a homogenized elastoplastic dynamic constitutive model of a lattice structure provided by this invention adopts the following technical solution, including the following steps:
[0005] (1) Conduct basic mechanical property tests on lattice structures under uniaxial tension, uniaxial compression and pure shear conditions and obtain test results;
[0006] (2) Conduct numerical simulations of the mechanical properties of lattice structures under quasi-static and dynamic uniaxial tension, uniaxial compression and pure shear conditions. Compare the engineering stress-engineering strain curves and shear stress-shear strain curves obtained from the numerical simulations with the experimental results in step (1). The comparison includes the slope of the linear elastic segment in the stress-strain curve and the stress and strain corresponding to the initial yield. If the error is less than the preset error threshold, proceed to step (3). If the error is greater than the preset error threshold, correct the geometric model and material model in the numerical simulation.
[0007] (3) Based on the numerical simulation results of uniaxial tension, uniaxial compression and pure shear loading under quasi-static conditions, the engineering stress-engineering strain curves under uniaxial tension and uniaxial compression are processed into true stress-true strain curves to obtain the initial yield parameters; numerical simulation of the mechanical properties of lattice structures under biaxial tension, triaxial tension, biaxial compression and triaxial compression under quasi-static conditions is carried out, and the engineering stress-engineering strain curves of uniaxial tension, uniaxial compression, biaxial tension, triaxial tension, biaxial compression and triaxial compression are processed into true stress-true strain curves to obtain a total of six sets of true stress-true strain curves and one set of shear stress-shear strain curves, for a total of seven sets of stress-strain curves; the uniaxial tension, uniaxial compression, biaxial tension, triaxial tension, biaxial compression, triaxial compression and pure shear loading are referred to as the seven loading conditions;
[0008] (4) Determine the characteristic stress in each set of stress-strain curves. and characteristic strain Seven characteristic stress-strain curves were obtained;
[0009] (5) Define a dimensionless physical quantity η. The value range of the dimensionless physical quantity η is -1 to 1. When the dimensionless physical quantity η changes between -1 and 0, it indicates that the lattice structure gradually changes from a triaxial compression state to a pure shear state. When the dimensionless physical quantity η changes between 0 and 1, it indicates that the structure gradually transitions from a pure shear state to a triaxial tension state. Perform linear fitting on the hardening modulus under seven different working conditions, and finally obtain the hardening modulus H corresponding to the seven loading conditions. Plot the hardening modulus H with the dimensionless physical quantity η.
[0010] (6) Change the loading speed under each loading condition in the numerical simulation to obtain the characteristic strain variation curves under different loading speeds. Perform linear fitting on each characteristic strain variation curve under different loading speeds, and use the slope of the fitting as the equivalent strain rate under the loading condition and loading speed.
[0011] For any loading condition, a high strain rate loading simulation is performed. The logarithmic strain rate is defined, and its calculation method is as follows:
[0012] Logarithmic strain rate = ln(equivalent strain rate / quasi-static loading strain rate);
[0013] Wherein, the quasi-static loading strain rate refers to the strain rate generated in step (3) based on any one of the loading conditions under quasi-static conditions, namely uniaxial tension, uniaxial compression, pure shear loading, biaxial tension, triaxial tension, biaxial compression, and triaxial compression; the high strain rate refers to the strain rate being higher than the quasi-static loading strain rate.
[0014] Multiple points are randomly selected on any characteristic stress-characteristic strain curve as representative characteristic strains. Each characteristic point corresponds to a set of logarithmic strain rates and normalized characteristic stresses. Then, the logarithmic strain rates and normalized characteristic stresses are plotted as scatter plots. The strain rate hardening coefficient C is obtained by linear fitting of these scatter plots. After the lattice structure yields, the subsequent yield stress is calculated based on the hardening modulus H and the strain rate hardening coefficient C.
[0015] Furthermore, in step (3), and Represents the true stress and true strain at yield in uniaxial tension or uniaxial compression. E is the equivalent Young's modulus; and Shear yielding is represented by the corresponding shear stress and shear strain. G is the equivalent shear modulus; the equivalent Poisson's ratio of the lattice structure is obtained based on numerical simulation results of uniaxial tension or uniaxial compression. .
[0016] Furthermore, in step (3), both the uniaxial tension and uniaxial compression conditions only include... A curve, which includes both biaxial tensile and biaxial compression conditions. and Both curves include triaxial tensile and triaxial compression conditions. , and Three curves, including the pure shear condition. A curve.
[0017] Furthermore, in step (4), the characteristic stress ;
[0018] Characteristic strain ;
[0019] and It is a total physical quantity represented by six stress components. This is called characteristic equivalent stress. This is called characteristic volumetric stress. and It is a total physical quantity represented by six strain components. This is called the characteristic equivalent change. This becomes characteristic volumetric strain. It is a proportionality constant calculated using Poisson's ratio.
[0020] Furthermore, using characteristic stress as the criterion for determining whether a structure has entered the yielding stage, the macroscopic yield function of a lattice structure can be expressed as:
[0021] ;
[0022] In the formula, Y represents the characteristic stress corresponding to the initial yield. A value less than 0 means the lattice structure is still in the elastic stage, when A value greater than 0 indicates that the lattice structure has entered the yielding stage.
[0023] Furthermore, in step (5), the dimensionless physical quantity ;
[0024] Furthermore, in step (6), for a homogenized finite element of a lattice structure, the yield stress of the homogenized finite element at a certain moment is Y. old A plastic strain increment occurs within a time interval Δt. ,Will The ratio of Δt to strain rate Then, the subsequent yield stress Y after time Δt is calculated according to the following formula, where The strain rate corresponding to quasi-static loading;
[0025] .
[0026] Furthermore, the three-dimensional lattice structure has the same periodicity in the three directions of space, that is, the three equivalent Young's moduli of the lattice structure in the three principal directions of space are equal, the three equivalent shear moduli are equal and the three independent Poisson's ratios are equal, and the initial yield strength of the lattice structure under tensile and compressive loads is equal.
[0027] Beneficial effects: In traditional mesoscopic finite element modeling, the unit cell of a lattice structure often requires discretization by thousands or even tens of thousands of finite element elements. This invention, however, uses a single finite element to characterize the equivalent mechanical response of the lattice structure unit cell in numerical simulation and introduces a description of the strain rate strengthening effect. Therefore, this method can significantly reduce the mesh size required for the model, thereby reducing computational overhead, saving computational resources, and effectively improving numerical computation efficiency.
[0028] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method.
[0029] The present invention also provides a computer-readable storage medium having a computer program stored thereon, characterized in that the computer program, when executed by a processor, implements the steps of the above-described method. Attached Figure Description
[0030] Figure 1 This is a schematic diagram of the three main directions of the body-centered cubic lattice structure in this invention;
[0031] Figure 2 This invention relates to a flowchart of the process for establishing a homogenized elastoplastic dynamic constitutive model for a lattice structure.
[0032] Figure 3 This is a schematic diagram of the true stress-true strain curve of the ideal deformation of the lattice structure involved in this invention;
[0033] Figure 4 This invention relates to schematic diagrams of characteristic stress-characteristic strain curves under different loading conditions;
[0034] Figure 5 This is a schematic diagram of obtaining the hardening modulus through linear fitting, as per the present invention.
[0035] Figure 6 This is a schematic diagram illustrating the change of hardening modulus with η as described in the present invention;
[0036] Figure 7 This invention relates to a schematic diagram of the equivalent strain rate corresponding to different loading speeds under typical loading conditions.
[0037] Figure 8 This is a schematic diagram of the characteristic stress corresponding to the representative characteristic strain involved in this invention;
[0038] Figure 9 This is a schematic diagram of obtaining the strain rate strengthening coefficient through linear fitting, which is the subject of this invention. Detailed Implementation
[0039] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. After reading this invention, any modifications of the invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.
[0040] Firstly, the structural and mechanical properties of the lattice structure to which this invention applies are defined as follows:
[0041] I. A three-dimensional lattice structure exhibits the same periodicity in three directions in space. That is, the three equivalent Young's moduli, three equivalent shear moduli, and three independent Poisson's ratios are equal in the three principal directions of the lattice structure. Taking a body-centered cubic (BCC) lattice structure as an example, the specific explanation is as follows: Because a three-dimensional lattice structure exhibits orthogonal anisotropy in space, its three principal directions are as follows: Figure 1 As shown, its elastic deformation follows Hooke's law, i.e., equation (1):
[0042] (1)
[0043] (2)
[0044] In the formula, , and This represents the positive strain in the three main directions. , and Engineering shear strain representing three directions. , and This represents the normal stress in the three principal directions. , and E1, E2, and E3 represent the shear stresses in three directions, and E3 represents the three equivalent Young's moduli in the three directions in space. 12 G 23 and G 13 Representing three equivalent shear moduli, , , , , and Representing six equivalent Poisson ratios, according to Maxwell's criterion, i.e., equation (2), there are only three independent Poisson ratios. Since the unit cell of the BCC structure has the same periodic arrangement in three directions in space, ignoring the mechanical property error caused by the printing direction, in this embodiment, the above independent material parameters are further simplified, assuming that the three equivalent Young's moduli in space are equal, the three equivalent shear moduli are equal, and the three independent Poisson ratios are equal, as shown in equation (3). It should be noted that satisfying the above assumptions does not mean that the structure degenerates into an isotropic material, because E, G and The two are independent of each other, and the independent mechanical property constants cannot degenerate into two; the material still has orthogonal anisotropy.
[0045] (3)
[0046] Second, the initial yield strength of the lattice structure is equal under tensile and compressive loads, i.e., tensile-compressive symmetry.
[0047] The method for establishing a homogenized elastoplastic dynamic constitutive model of a lattice structure provided by this invention includes the following steps: Figure 2 As shown, the specific explanation is as follows:
[0048] (1) Conduct basic mechanical performance tests on the lattice structure under uniaxial tension, uniaxial compression and pure shear conditions and obtain test results. Quasi-static and dynamic performance tests should be carried out simultaneously for each loading condition.
[0049] (2) Conduct numerical simulations of the mechanical properties of lattice structures under quasi-static and dynamic uniaxial tension, uniaxial compression and pure shear conditions. Compare the engineering stress-engineering strain curves and shear stress-shear strain curves obtained from the numerical simulations with the experimental results in step (1). The comparison includes the slope of the linear elastic segment in the stress-strain curve and the stress and strain corresponding to the initial yield. If the error is within acceptable limits, proceed to the next step. If the error is greater than the preset error threshold, correct the geometric model and material model in the numerical simulation.
[0050] (3) Based on the numerical simulation results of uniaxial loading and pure shear loading under quasi-static conditions, the engineering stress-engineering strain curves under uniaxial tension and uniaxial compression conditions are processed into true stress-true strain curves to obtain the initial yield parameters.
[0051] The specific explanation is as follows: When a lattice structure undergoes elastoplastic deformation, its uniaxial true stress-true strain curve and shear stress-shear strain curve are as follows: Figure 3 As shown. Among them, and The true stress and true strain represent the uniaxial tensile / compressive yield, and their relationship satisfies equation (4). and The shear yield represents the corresponding shear stress and shear strain, and their relationship satisfies equation (5). Furthermore, the equivalent Poisson's ratio of the lattice structure can be obtained based on uniaxial tension / compression numerical simulation results. .
[0052] (4)
[0053] (5)
[0054] E is the equivalent Young's modulus, and G is the equivalent shear modulus.
[0055] Numerical simulations of the mechanical properties of lattice structures under quasi-static conditions of biaxial tension, triaxial tension, biaxial compression, and triaxial compression were conducted. Combined with previously calculated quasi-static uniaxial tension, uniaxial compression, and pure shear conditions, a total of seven conditions were simulated. The engineering stress-strain curves for the tension and compression conditions were converted into true stress-strain curves, resulting in a total of six sets of true stress-strain curves and one set of shear stress-strain curves, hereinafter referred to as the seven sets of stress-strain data. Note that each set of stress-strain data contains 1 to 3 stress-strain data points. For example, for the uniaxial tension and uniaxial compression conditions, since the stresses in the biaxial and triaxial directions are 0, these two conditions only contain 1 to 3 stress-strain data points. A curve, while both biaxial tensile and compression conditions include... and Both curves include the triaxial tensile condition and the three-cycle compression condition. , and Three curves, the pure shear condition includes A curve.
[0056] (4) Obtain the initial yield characteristic stress: According to formulas (6) to (14), substitute the seven sets of stress-strain data to obtain the characteristic stress under each loading condition. and characteristic strain Seven characteristic stress-strain curves were obtained, such as Figure 4 As shown, under different loading conditions, the characteristic stress-characteristic strain curves can completely unify the elastic stage, and all conditions have the same initial yield characteristic stress.
[0057] (6)
[0058] (7)
[0059] in, and It is a total physical quantity represented by six stress components. This is called characteristic equivalent stress. This is called characteristic volumetric stress. and It is a total physical quantity represented by six strain components. This is called the characteristic equivalent change. This becomes characteristic volumetric strain. It is a proportionality constant calculated using Poisson's ratio. The specific calculation expression for the above physical quantity is as follows:
[0060] (8)
[0061] (9)
[0062] (10)
[0063] (11)
[0064] (12)
[0065] Characteristic stress and characteristic strain are work conjugate variables, satisfying:
[0066] (13)
[0067] (14)
[0068] Using characteristic stress as the criterion for determining whether a structure has entered the yielding stage, the macroscopic yield function of a lattice structure can be expressed as:
[0069] (15)
[0070] In the formula, Y represents Figure 4 The characteristic stress corresponding to the initial yield in the middle, A value less than 0 means the structure is still in the elastic stage, when A value greater than 0 indicates that the structure has entered the yielding stage.
[0071] (5) Fitting the hardening modulus H: Although the initial yield is uniform on the characteristic stress-characteristic strain curve, after the initial yield, the characteristic stress-characteristic strain curve diverges significantly with the increase of plastic strain, showing a clear loading path dependence. A linear model is then used to describe the subsequent yield of the lattice structure. Since the subsequent yield has a loading path dependence, the dimensionless physical quantity η is first defined:
[0072] (16)
[0073] The value range of is -1 to 1. Combining with equation (6), it can be seen that when When the value varies between -1 and 0, it indicates that the structure is gradually transitioning from a triaxial compression state to a pure shear state. When the value varies between 0 and 1, it indicates that the structure is gradually transitioning from pure shear to triaxial tension. Linear fitting was performed on the hardening modulus under seven different working conditions, such as... Figure 5 As shown, the hardening modulus H corresponding to the seven loading conditions can be obtained. The graph showing the change of hardening modulus H with η is plotted as follows. Figure 6 As shown.
[0074] (6) Considering the strain rate effect: First, change the loading speed under each loading condition in the numerical simulation to obtain the characteristic strain variation curves with time under different loading speeds, such as... Figure 7 As shown, a linear fit is performed on each curve, and the slope of the fit is taken as the equivalent strain rate at that loading speed under that loading condition. Taking a certain loading path as an example, as... Figure 8 As shown, assuming a uniaxial tensile condition, based on the numerical simulation of uniaxial tension under quasi-static conditions in step (2), a high strain rate loading simulation is performed. The figure shows the simulation results under three high strain rates. Under high strain rates, the material exhibits a strain rate strengthening effect, and the characteristic stress increases with the increase of the strain rate. Multiple points are randomly selected from the characteristic stress-characteristic strain curve as representative characteristic strains. Figure 8 Two representative characteristic strains are given. Assuming a representative characteristic strain of 1, a normalized characteristic stress is defined. The normalized characteristic stress is equal to the ratio of the characteristic stress at high strain rate to the characteristic stress under quasi-static loading, i.e., in... Figure 8 In the schematic diagram, four normalized characteristic stresses can be obtained under a representative characteristic strain of 1, and the normalized characteristic stress under quasi-static loading is 1. The logarithmic strain rate is defined, and its calculation method is as follows:
[0075] Logarithmic strain rate = ln(equivalent strain rate / quasi-static loading strain rate) (17)
[0076] Wherein, the quasi-static loading strain rate refers to the strain rate generated in step (3) based on any one of the loading conditions under quasi-static conditions, namely uniaxial tension, uniaxial compression, pure shear loading, biaxial tension, triaxial tension, biaxial compression, and triaxial compression; the high strain rate refers to the strain rate being higher than the quasi-static loading strain rate.
[0077] At this point, Figure 8 Each feature point in the model can correspond to a set of logarithmic strain rates and normalized characteristic stresses. Specifically, Figure 8The selected characteristic points are characteristic strain and characteristic stress. Each characteristic point is then converted into its corresponding logarithmic strain rate and normalized characteristic stress. Finally, the logarithmic strain rate and normalized characteristic stress are plotted as scatter plots, as shown below. Figure 9 As shown in the figure. The more representative characteristic strains selected and the more curves under high strain rates, the more characteristic points are obtained. The above only takes one loading condition (uniaxial tension) as an example. For the other six loading conditions, the method for obtaining characteristic points and the corresponding logarithmic strain rate and normalized characteristic stress is the same as described above. Finally, the logarithmic strain rate and normalized characteristic stress corresponding to all obtained characteristic points are plotted on a single graph, as shown in the figure. Figure 9 As shown, the strain rate strengthening coefficient C can be obtained through linear fitting.
[0078] Thus, based on the preceding steps, a homogenized elastoplastic dynamic constitutive model of the lattice structure can be constructed. The principle of this constitutive model is to determine the characteristic stress corresponding to the yielding of the element at any time during finite element calculation. The specific principle is as follows: First, the characteristic stress is used as the criterion for yielding. The initial yield characteristic stress obtained in step (5) is used to determine whether the lattice structure has entered yielding. After the lattice structure enters yielding, the subsequent yield stress is calculated based on the hardening modulus H and the strain rate strengthening coefficient C. The method is as follows: Assume that for a homogenized finite element of a lattice structure, the yield stress of the element at a certain time is Y. old Then, a small plastic strain increment occurs within a time interval Δt. Next, the hardening modulus H corresponding to the current loading condition is first obtained through linear interpolation, and then... The ratio of Δt to strain rate Then, the yield stress Y after time Δt can be calculated using the following formula, where The strain rate corresponding to quasi-static loading is typically 0.001 s⁻¹. -1 .
[0079] (18)
[0080] In addition, this invention uses a BCC lattice structure as an example, but the related methods are also applicable to other types of lattice structures, as long as the type of lattice structure conforms to settings one and two in this embodiment.
[0081] Furthermore, there are many specific methods and approaches to implement this invention, and the above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention.
Claims
1. A method for establishing a homogenized elastoplastic dynamic constitutive model of a lattice structure, characterized in that, Includes the following steps: (1) Conduct basic mechanical property tests on lattice structures under uniaxial tension, uniaxial compression and pure shear conditions and obtain test results; (2) Conduct numerical simulations of the mechanical properties of lattice structures under quasi-static and dynamic uniaxial tension, uniaxial compression and pure shear conditions. Compare the engineering stress-engineering strain curves and shear stress-shear strain curves obtained from the numerical simulations with the experimental results in step (1). The comparison includes the slope of the linear elastic segment in the stress-strain curve and the stress and strain corresponding to the initial yield. If the error is less than the preset error threshold, proceed to step (3). If the error is greater than the preset error threshold, correct the geometric model and material model in the numerical simulation. (3) Based on the numerical simulation results of uniaxial tension, uniaxial compression and pure shear loading under quasi-static conditions, the engineering stress-engineering strain curves under uniaxial tension and uniaxial compression are processed into true stress-true strain curves to obtain the initial yield parameters. Numerical simulations of the mechanical properties of lattice structures under quasi-static loading conditions (biaxial tension, triaxial tension, biaxial compression, and triaxial compression) were conducted. The engineering stress-strain curves for the uniaxial tension, uniaxial compression, biaxial tension, triaxial tension, biaxial compression, and triaxial compression conditions were converted into true stress-strain curves, resulting in a total of six sets of true stress-strain curves and one set of shear stress-strain curves, for a total of seven sets of stress-strain curves. The uniaxial tension, uniaxial compression, biaxial tension, triaxial tension, biaxial compression, triaxial compression, and pure shear loading conditions are referred to as the seven loading conditions. (4) Determine the characteristic stress in each set of stress-strain curves. and characteristic strain Seven characteristic stress-strain curves were obtained; (5) Define a dimensionless physical quantity η. The value range of the dimensionless physical quantity η is -1 to 1. When the dimensionless physical quantity η changes between -1 and 0, it indicates that the lattice structure gradually changes from a triaxial compression state to a pure shear state. When the dimensionless physical quantity η changes between 0 and 1, it indicates that the structure gradually transitions from a pure shear state to a triaxial tension state. Perform linear fitting on the hardening modulus under seven different working conditions, and finally obtain the hardening modulus H corresponding to the seven loading conditions. Plot the hardening modulus H with the dimensionless physical quantity η. (6) Change the loading speed under each loading condition in the numerical simulation to obtain the characteristic strain variation curves under different loading speeds. Perform linear fitting on each characteristic strain variation curve under different loading speeds, and use the slope of the fitting as the equivalent strain rate under the loading condition and loading speed. For any loading condition, a high strain rate loading simulation is performed. The logarithmic strain rate is defined, and its calculation method is as follows: Logarithmic strain rate = ln(equivalent strain rate / quasi-static loading strain rate); Wherein, the quasi-static loading strain rate refers to the strain rate generated in step (3) based on any one of the loading conditions under quasi-static conditions, namely uniaxial tension, uniaxial compression, pure shear loading, biaxial tension, triaxial tension, biaxial compression, and triaxial compression; the high strain rate refers to the strain rate being higher than the quasi-static loading strain rate. Multiple points are randomly selected on any characteristic stress-characteristic strain curve as representative characteristic strains. Each characteristic point corresponds to a set of logarithmic strain rates and normalized characteristic stresses. Then, the logarithmic strain rates and normalized characteristic stresses are plotted as scatter plots. The strain rate hardening coefficient C is obtained by linear fitting of these scatter plots. After the lattice structure reaches yield, the subsequent yield stress is calculated based on the hardening modulus H and the strain rate hardening coefficient C.
2. The method for establishing a homogeneous elastoplastic dynamic constitutive model of a lattice structure as described in claim 1, characterized in that, In step (3), and Represents the true stress and true strain at yield in uniaxial tension or uniaxial compression. E is the equivalent Young's modulus; and Shear yielding is represented by the corresponding shear stress and shear strain. G is the equivalent shear modulus; the equivalent Poisson's ratio of the lattice structure is obtained based on numerical simulation results of uniaxial tension or uniaxial compression. .
3. The method for establishing a homogeneous elastoplastic dynamic constitutive model of a lattice structure as described in claim 2, characterized in that, In step (3), both the uniaxial tension and uniaxial compression conditions only include A curve, which includes both biaxial tensile and biaxial compression conditions. and Both curves include triaxial tensile and triaxial compression conditions. , and Three curves, including the pure shear condition. A curve.
4. The method for establishing a homogeneous elastoplastic dynamic constitutive model of a lattice structure as described in claim 3, characterized in that, In step (4), characteristic stress ; Characteristic strain ; and It is a total physical quantity represented by six stress components. This is called characteristic equivalent stress. This is called characteristic volumetric stress. and It is a total physical quantity represented by six strain components. This is called the characteristic equivalent change. This becomes characteristic volumetric strain. It is a proportionality constant calculated using Poisson's ratio.
5. The method for establishing a homogenized elastoplastic dynamic constitutive model of a lattice structure as described in claim 4, characterized in that, Using characteristic stress as the criterion for determining whether a structure has entered the yielding stage, the macroscopic yield function of a lattice structure can be expressed as: ； In the formula, Y represents the characteristic stress corresponding to the initial yield. A value less than 0 means the lattice structure is still in the elastic stage, when A value greater than 0 indicates that the lattice structure has entered the yielding stage.
6. The method for establishing a homogenized elastoplastic dynamic constitutive model of a lattice structure as described in claim 5, characterized in that, In step (5), the dimensionless physical quantity .
7. The method for establishing a homogeneous elastoplastic dynamic constitutive model of a lattice structure as described in claim 1, characterized in that, In step (6), for a homogenized finite element with a lattice structure, the yield stress of the homogenized finite element at a certain moment is Y. old A plastic strain increment occurs within a time interval Δt. ,Will The ratio of Δt to strain rate Then, the subsequent yield stress Y after time Δt is calculated according to the following formula, where The strain rate corresponding to quasi-static loading; 。 8. The method for establishing a homogenized elastoplastic dynamic constitutive model of a lattice structure as described in any one of claims 1 to 7, characterized in that, The three-dimensional lattice structure has the same periodicity in the three directions of space, that is, the three equivalent Young's moduli of the lattice structure in the three principal directions of space are equal, the three equivalent shear moduli are equal and the three independent Poisson's ratios are equal, and the initial yield strength of the lattice structure under tensile and compressive loads is equal.
9. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 8.
10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 8.