Mesoscale performance analysis method for biphase material

Abstract

The invention discloses a two-phase material mesoscale performance analysis method which is characterized by comprising the following steps: S1, constructing a two-phase material crystal plasticity finite element model; s2, constructing a constitutive model of related plasticity; and S3, determining the damage of the two-phase material according to the crystal plasticity finite element model of the two-phase material and the constitutive model of the related plasticity. According to the modeling mode provided by the method, the micromechanical property of the material can be well observed, and the defect that an original model cannot describe the damage process is overcome by adding damage evolution. By means of the method, good microscopic simulation can be conducted on common multi-phase materials.

Description

Technical Field

[0001] The invention belongs to the technical field of dual-phase material modeling and analysis, and in particular to a method for analyzing the mesoscopic scale performance of dual-phase materials. Background Art

[0002] Dual-phase materials refer to composite materials with two types of microstructures. Due to the different structures and physical properties in different phases, they often have better performance than single-phase materials when subjected to loads, such as nickel-based high-temperature alloys. The crystal plasticity finite element method is based on the large deformation crystal plasticity theory. Through the mesoscopic model, the rate-dependent constitutive relationship is used to evolve the deformation process on the basis of the slip system, and the finite element method that connects the mesoscopic and macroscopic responses is used through the homogenization method. In applications, the rate-dependent constitutive model is often used to describe the evolution law of material deformation. Its specific parameters need to be obtained through experiments, and then these parameters are imported into the actual finite element calculation.

[0003] The crystal plasticity finite element model uses disordered polycrystalline representative volume units to characterize. In this model, all grains differ only in their grain orientations, which cannot well describe the interaction between different grains. Especially for two-phase materials, a geometric model that can better reflect the interaction between different phases and their characteristics is needed. On the other hand, the relevant constitutive model does not consider damage, so it cannot describe the necking phenomenon during the destruction of metal materials, which is part of the destruction process of metal materials. Therefore, it is necessary to establish a crystal plasticity model for describing the characteristics of two-phase materials, and develop a constitutive model that can describe the material destruction stage, so as to realize the calculation of the mesoscopic performance of two-phase materials.

[0004] Chinese patent 202210521442.5 discloses a mesoscopic modeling and multi-scale analysis method suitable for needle-punched composite materials. First, a CT tomography test is carried out to measure the structural dimensions and obtain characteristic parameters; the punctured area is geometrically divided based on the general unit cell model, and a mesoscopic analysis model of the punctured area is established. Then, for the non-punctured area in the needle-punched composite material, the continuous medium damage theory is used to describe its damage behavior; considering that the needle-punched composite material has a complex material phase, the idea of ​​hierarchical modeling is adopted to obtain the equivalent elastic properties of the non-punctured area as the input of the continuous medium damage theory model. Finally, in view of the fact that the punctured area does not have the characteristics of applying periodic boundary conditions, a local area volume averaging method is proposed to realize the two-way transmission of meso-macro cross-scale data in multi-scale analysis. It is not applicable to the mesoscopic scale performance analysis of dual-phase materials. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a mesoscopic-scale performance analysis method for two-phase materials, which can well characterize the differences between different phases of two-phase materials and their interactions, and calculate the destruction process of the material, making the simulation results more complete, and can perform good microscopic simulation of general multiphase materials.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: a method for analyzing the mesoscopic properties of a dual-phase material, comprising the following steps:

[0007] S1. Construct a finite element model of crystal plasticity of dual-phase materials;

[0008] S2. Construct a constitutive model of related plasticity;

[0009] S3. Determine the damage of the dual-phase material based on the finite element model of dual-phase material crystal plasticity and the constitutive model of related plasticity.

[0010] The S1 comprises the following sub-steps:

[0011] S11. Collecting microstructure images of dual-phase materials using microstructure characterization methods;

[0012] S12, extracting a single-phase volume representative element according to the geometric features and geometric relationships of each phase in the microstructure image;

[0013] S13, constructing geometric models using finite element software;

[0014] S14, obtaining a stress-strain curve of the dual-phase material, and obtaining material parameters from the stress-strain curve;

[0015] S15. Based on the single-phase volume representative element, geometric model and material parameters, different constitutive relations are generated for different phases to obtain a two-phase material crystal plasticity finite element model.

[0016] The S2 comprises the following sub-steps:

[0017] S21, obtaining performance parameters of the constitutive relationship and calculating the shear strain rate;

[0018] S22, calculating the increment of shear strain according to the shear strain rate, and determining the thermal slip resistance and the hardening matrix;

[0019] S23. Based on the thermal slip resistance and hardening matrix, a constitutive model of related plasticity is constructed.

[0020] The calculation formula of the shear strain rate is:

[0021]

[0022] Where Q is the activation energy barrier, k B(=1.3807×10 -23 J / K) is the Boltzmann constant, θ is the current absolute temperature, p and q are material constants, is the reference slip rate, is the thermal sliding resistance caused by thermal effect, is the effective shear force, τ α is the original shear force, It is the thermal slip resistance caused by non-thermal effects.

[0023] In S23, the calculation formula of thermal sliding resistance is:

[0024]

[0025] Where n α is the normal vector of the sliding plane, t β is the direction of slip;

[0026] In S22, the calculation formula of the hardening matrix is:

[0027]

[0028] In the formula, q αβ =q+(1-q)δ αβ , q is a constant, h0, r are constants, is the value of saturation shear stress.

[0029] The S3 comprises the following sub-steps:

[0030] S31, obtaining stress and strain data on each frame unit;

[0031] S32, calculating effective stress according to stress-strain data on each frame unit;

[0032] S33. Calculate the evolution damage factor based on the effective stress;

[0033] S34, performing homogenization processing on the effective stress of all units in each frame unit to determine the lossy stress-strain curve;

[0034] S35. Determine the damage of the dual-phase material based on the loss-containing stress-strain curve, the finite element model of the dual-phase material crystal plasticity, and the constitutive model of the related plasticity.

[0035] In S32, the calculation formula of effective stress is:

[0036]

[0037] In the formula, is the second-order tensor of damage factor, and σ is the second-order tensor of stress at the integration point.

[0038] The beneficial effects of the present invention are as follows: the present invention establishes a two-phase material calculation model based on microstructure for the microscopic characteristics of two-phase materials, and at the same time constructs a crystal plasticity model and damage relationship considering twins, and creatively uses the two to describe the plastic deformation and damage analysis of two-phase materials. The calculation model and process can well reflect the microscopic characteristics of different phases of two-phase materials, innovatively realizes the modeling method of combining finite element model with actual model, and provides a reliable and credible method for describing the damage and destruction process of two-phase materials through coupling of damage and crystal plasticity models. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention will be further described below in conjunction with the accompanying drawings:

[0040] Figure 1 Schematic diagram of the microstructure of the dual-phase material;

[0041] Figure 2 It is a schematic diagram of the finite element model of the dual-phase material of the present invention;

[0042] Figure 3 Establishing a flow chart for the finite element model of the dual-phase material crystal plasticity of the present invention;

[0043] Figure 4 A flow chart for realizing the rate-dependent plastic constitutive relation based on twin evolution of the present invention;

[0044] Figure 5 Constructing a flow chart for the damage relationship of the present invention based on the dual-phase material model;

[0045] Figure 6 It is a simulation flow chart of the present invention. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0047] The technical solution of the present invention is described in detail with specific embodiments below. The following specific embodiments can be combined or replaced with each other according to actual conditions, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0048] Example 1

[0049] A method for analyzing mesoscopic properties of a dual-phase material comprises the following steps:

[0050] S1. Construct a finite element model of crystal plasticity of dual-phase materials;

[0051] S2. Construct a constitutive model of related plasticity;

[0052] S3. Determine the damage of the dual-phase material based on the finite element model of dual-phase material crystal plasticity and the constitutive model of related plasticity.

[0053] The S1 comprises the following sub-steps:

[0054] S11. Collecting microstructure images of dual-phase materials using microstructure characterization methods;

[0055] S12, extracting a single-phase volume representative element according to the geometric features and geometric relationships of each phase in the microstructure image;

[0056] S13, constructing geometric models using finite element software;

[0057] S14, obtaining a stress-strain curve of the dual-phase material, and obtaining material parameters from the stress-strain curve;

[0058] S15. Based on the single-phase volume representative element, geometric model and material parameters, different constitutive relations are generated for different phases to obtain a two-phase material crystal plasticity finite element model.

[0059] The S2 comprises the following sub-steps:

[0060] S21, obtaining performance parameters of the constitutive relationship and calculating the shear strain rate;

[0061] S22, calculating the increment of shear strain according to the shear strain rate, and determining the thermal slip resistance and the hardening matrix;

[0062] S23. Based on the thermal slip resistance and hardening matrix, a constitutive model of related plasticity is constructed.

[0063] The calculation formula of the shear strain rate is:

[0064]

[0065] Where Q is the activation energy barrier, k B (=1.3807×10 -23 J / K) is the Boltzmann constant, θ is the current absolute temperature, p and q are material constants, is the reference slip rate, is the thermal sliding resistance caused by thermal effect, is the effective shear force, τ α is the original shear force, It is the thermal slip resistance caused by non-thermal effects.

[0066] In S23, the calculation formula of thermal sliding resistance is:

[0067]

[0068] Where n α is the normal vector of the sliding plane, t β is the direction of slip;

[0069] In S22, the calculation formula of the hardening matrix is:

[0070]

[0071] In the formula, q αβ =q+(1-q)δ αβ , q is a constant, h0, r are constants, is the value of saturation shear stress.

[0072] The S3 comprises the following sub-steps:

[0073] S31, obtaining stress and strain data on each frame unit;

[0074] S32, calculating effective stress according to stress-strain data on each frame unit;

[0075] S33. Calculate the evolution damage factor based on the effective stress;

[0076] S34, performing homogenization processing on the effective stress of all units in each frame unit to determine the lossy stress-strain curve;

[0077] S35. Determine the damage of the dual-phase material based on the loss-containing stress-strain curve, the finite element model of the dual-phase material crystal plasticity, and the constitutive model of the related plasticity.

[0078] In S32, the calculation formula of effective stress is:

[0079]

[0080] In the formula, is the second-order tensor of damage factor, and σ is the second-order tensor of stress at the integration point. The specific implementation method of the mesoscopic scale modeling method and constitutive relationship calculation model of the dual-phase material involved in the present invention is as follows:

[0081] (1) Construction of finite element model of dual-phase material crystal plasticity

[0082] First, the microstructure distribution and geometric characteristics of the dual-phase material are obtained by microscopic characterization techniques such as EBSD. Figure 1 As shown in the figure, including the distribution and size of grain boundaries, the shape and size of each phase, etc., the smallest periodic unit in the microstructure is selected as the volume representative element. Since the two-phase material has a certain degree of inter-embeddedness, the relevant geometric relationship model is constructed with the help of geometric modeling software, such as Figure 2As shown in the figure, in order to ensure the true reproduction of the characteristics of the two-phase material, different constitutive relations are designed for different phases. For example, the phase that bears the main plastic deformation adopts the traditional crystal plastic constitutive relationship, and the phase with smaller deformation adopts the elastic constitutive relationship. The two phases are connected through contact or grid sharing. Finally, periodic boundary conditions are imposed on the volume representative element to ensure that the volume representative unit can well simulate the load and constraint conditions around the smallest unit. The process of establishing the finite element model of the crystal plasticity of the two-phase material is as follows: Figure 3 The specific steps are as follows:

[0083] S11. Use existing microstructure characterization methods to collect microstructure images of dual-phase materials, that is, use the SEM method. The scanning electron microscope SEM is a powerful microscope that scans the sample surface with a high-energy electron beam, captures signals scattered or emitted by electrons, and generates high-resolution images of the sample surface. When using SEM, you first need to prepare the sample properly, including ensuring that the sample is dry, conductive, and spraying a conductive film when necessary. Then fix the sample on the sample stage and perform vacuum operation to ensure that the inside of the instrument is in a high vacuum state. Next, according to the nature of the sample and the purpose of observation, set appropriate parameters such as acceleration voltage, working distance, and beam size, and select a suitable detector. A clear image is obtained by adjusting the focus of the electron beam and ensuring that the electron beam is perpendicular to the sample surface. Finally, start the scanning electron microscope for imaging, adjust the brightness, contrast, and magnification of the image as needed, optimize the image quality, and perform necessary post-processing to obtain it. Figure 1 of the image.

[0084] S12. According to the geometric features and geometric relationships of each phase in the microstructure image, a single-phase volume representative element is extracted. In this example, a gray precipitate phase and a black matrix phase can be seen from the microstructure image. The geometric dimensions of each phase are determined according to the scanning parameters, including the geometric features of the precipitate phase and the characteristic length of the matrix phase. In this example, it is found that there is a minimum array unit composed of the matrix phase and the precipitate phase in the periscopic structure, that is, Figure 1 The red box in the figure shows the volume representing the unit shape and parameters.

[0085] S13, using finite element software to build a geometric model. The geometric features and related parameters of the volume representative unit have been determined in S12. Next, it is built into a mesh model in the finite element software. As described in S12, RVE contains a matrix phase and a precipitate phase. The distribution law is that the matrix phase is the skeleton and the precipitate phase is attached to it. Based on this feature, the RVE model is established, such as Figure 2As shown in the figure, the green part represents the matrix phase, the red part represents the precipitation phase, and an RVE model contains 8 precipitation phases and a matrix skeleton. The construction method in the finite element software is to first build a cube geometric model, and then divide the cube into two parts, namely the matrix phase part and the precipitation phase part, through the cutting function.

[0086] S14. Obtain the stress-strain curve of the dual-phase material and obtain the material parameters from the stress-strain curve. Obtaining the stress-strain curve of the dual-phase material is usually achieved through experimental tests such as uniaxial tensile tests, which draw curves by recording the force and elongation of the sample during the stretching process. From these curves, key material parameters can be extracted, including elastic modulus, yield strength, tensile strength and elongation. The elastic modulus is obtained from the initial linear part of the curve, the yield strength corresponds to the first obvious yield point on the curve, the tensile strength is the maximum stress that the material can withstand, and the elongation is the maximum strain before the material breaks.

[0087] S15. Based on the single-phase volume representative element, geometric model and material parameters, different constitutive relations are generated for different phases to obtain a two-phase material crystal plastic finite element model. That is, according to the current experimental and research status, it is believed that the precipitate phase is approximately in an elastic state during the deformation process, while the matrix phase bears the main plastic deformation. Therefore, in this case, the matrix phase is considered to be a plastic deformation material, and the crystal plastic constitutive law is used. The two precipitate phases have high hardness and are considered to be elastic constitutive laws. Furthermore, the contact between the precipitate phase and the matrix phase is considered. Because it is a mesoscale deformation, continuous deformation is considered here, and fully coupled contact is used, thereby completing the two-phase crystal plastic finite element model.

[0088] (2) Rate-dependent plastic constitutive relation based on twin evolution

[0089] Based on the traditional phenomenological rate-dependent model, this method adopts a rate-dependent constitutive relationship that takes twinning into account. The implementation process is as follows: Figure 4 As shown, the first step is to read the parameters required for the constitutive relationship, and then use these parameters to assemble the stiffness matrix, rotation matrix, volume strain, slip plane and slip direction, Schmidt factor, etc. Next is to calculate the shear strain rate Its evolution formula is:

[0090] where Q is the activation energy barrier, k B (=1.3807×10 -23 J / K) is the Boltzmann constant, θ is the current absolute temperature, p and q are both material constants, is a reference slip rate, is the thermal slip resistance caused by thermal effect, and is the effective shear force, τ αis the original shear force, is the thermal slip resistance caused by non-thermal effects. For the reference slip rate, The following evolution formula is used:

[0091]

[0092] Where H is the Heaviside step function, is a known initial reference slip rate, and l p ,k, are material parameters, and the equivalent plastic strain The plastic strain component is the plastic strain gradient tensor component.

[0093] After solving the shear strain rate, the shear strain increment can be solved, and the thermal slip resistance and hardening matrix can be evolved from it. The thermal slip resistance is decomposed into the part caused by thermal effect and the part caused by non-thermal effects

[0094] in is the thermal effect hardening matrix component, is the shear slip rate, n α is the normal vector of the sliding plane, t β is the direction of slip. is the thermal hardening matrix component, is the shear slip rate, n α is the normal vector of the sliding plane, t β is the direction of slip. Then the total thermal slip resistance can be calculated

[0095] Finally, the hardening matrix is ​​made here Assumption, then complete the evolution of the hardening matrix for each slip system, the evolution formula is Where q αβ =q+(1-q)δ αβ , q is a constant, h0, r are constants, and is the value of the saturation shear stress, which is also a material constant.

[0096] At this point, the plastic constitutive model considering twins is implemented. It is only necessary to traverse the integration points on all units and calculate frame by frame to obtain the final finite element results.

[0097] (3) Construction of damage relationship based on dual-phase material model

[0098] Read the stress-strain values ​​in the result file and construct a mapping relationship to export the damage-containing stress-strain curve. First, create a script file to read the finite element calculation results. By creating a result object, call the object's member function to traverse and access the integration points on each unit in all frames in all steps. The integration points store the strain and stress information on the node. Store the stress, strain, volume fraction and other information on the integration points so that they can be homogenized and processed to obtain a lossless curve. After storage, substitute the stress component information into the effective stress The calculation formula in is the second-order tensor of the damage factor, and σ is the second-order tensor of the stress at the integration point. Then the effective stress at the integration point of the unit on the frame is obtained. The effective stress is obtained by the interaction between the original stress and the damage factor, and then the damage factor is substituted according to the effective stress The evolution formula of Where γ is the total accumulated slip strain, γ0 is the damage judgment reference rate, H(γ-γ0) indicates that when the value in the bracket is greater than 0, the value in the bracket is taken, otherwise it is taken as 0, β is a known parameter, I is the unit tensor of the second-order tensor, is the unit tensor of the fourth-order tensor, α and n are fixed parameters, and <> means that the value in the brackets is taken when it is greater than 0, otherwise it is taken as 0. Then the damage factor of the next frame is obtained. After traversing all the unit integration points in the frame, the evolution data of the effective stress is obtained. Then, through homogenization processing, that is, Where n is the number of all integration points, is the damage stress at the integration point, f i is the volume fraction at the integration point, and ε is the strain value at the integration point. Then, the average effective stress and average strain of each frame are obtained. Finally, the data points obtained in each frame are stored and plotted to obtain the stress-strain curve including damage. For a lossless curve, it is only necessary to replace the stress homogenization formula with damage The effective stress in the equation can be replaced by the lossless stress. In this way, the simulation curves under lossless and lossy conditions are obtained. The specific implementation process is as follows: Figure 5 shown.

[0099] By embedding the above damage model into the crystal plasticity model and applying it to the two-phase material model, reliability evaluation of the mesoscopic plasticity and damage calculation of the two-phase material can be achieved.

[0100] Through the model establishment of this method, the dual-phase material can be simulated and evaluated. The specific process is as follows: Figure 6 shown.

[0101] In addition to the above-mentioned preferred embodiments, the present invention also has other implementation modes. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection requested by the present invention.

Claims

1. A method for analyzing mesoscopic properties of dual-phase materials, characterized in that: The following steps are involved: S1. Construct a finite element model of crystal plasticity of dual-phase materials; S2. Construct a constitutive model of related plasticity; S3. Determine the damage of the dual-phase material based on the finite element model of dual-phase material crystal plasticity and the constitutive model of related plasticity.

2. The method for analyzing mesoscopic properties of dual-phase materials according to claim 1, characterized in that: The S1 comprises the following sub-steps: S11. Collecting microstructure images of dual-phase materials using microstructure characterization methods; S12, extracting a single-phase volume representative element according to the geometric features and geometric relationships of each phase in the microstructure image; S13, constructing geometric models using finite element software; S14, obtaining a stress-strain curve of the dual-phase material, and obtaining material parameters from the stress-strain curve; S15. Based on the single-phase volume representative element, geometric model and material parameters, different constitutive relations are generated for different phases to obtain a two-phase material crystal plasticity finite element model.

3. The method for analyzing mesoscopic properties of dual-phase materials according to claim 1, characterized in that: The S2 comprises the following sub-steps: S21, obtaining performance parameters of the constitutive relationship and calculating the shear strain rate; S22, calculating the increment of shear strain according to the shear strain rate, and determining the thermal slip resistance and the hardening matrix; S23. Based on the thermal slip resistance and hardening matrix, a constitutive model of related plasticity is constructed.

4. The method for analyzing mesoscopic properties of dual-phase materials according to claim 3, characterized in that: The calculation formula of the shear strain rate is: Where Q is the activation energy barrier, k B (=1.3807×10 -23 J / K) is the Boltzmann constant, θ is the current absolute temperature, p and q are material constants, is the reference slip rate, is the thermal sliding resistance caused by thermal effect, is the effective shear force, τ α is the original shear force, It is the thermal slip resistance caused by non-thermal effects.

5. The method for analyzing mesoscopic properties of dual-phase materials according to claim 3, characterized in that: In S23, the calculation formula of thermal sliding resistance is: Where n α is the normal vector of the sliding plane, t β is the direction of slip; In S22, the calculation formula of the hardening matrix is: In the formula, q αβ =q+(1-q)δ αβ , q is a constant, h0, r are both constants, is the value of saturation shear stress.

6. The method for analyzing mesoscopic properties of dual-phase materials according to claim 1, characterized in that: The S3 comprises the following sub-steps: S31, obtaining stress and strain data on each frame unit; S32, calculating effective stress according to stress-strain data on each frame unit; S33. Calculate the evolution damage factor based on the effective stress; S34, performing homogenization processing on the effective stress of all units in each frame unit to determine the lossy stress-strain curve; S35. Determine the damage of the dual-phase material based on the loss-containing stress-strain curve, the finite element model of the dual-phase material crystal plasticity, and the constitutive model of the related plasticity.

7. The method for analyzing mesoscopic properties of dual-phase materials according to claim 6, characterized in that: In S32, the calculation formula of effective stress is: In the formula, is the second-order tensor of damage factor, and σ is the second-order tensor of stress at the integration point.

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