Crack path propagation prediction method and system for pre-cracked plate based on crystal plasticity

Abstract

The present invention relates to a method and system for predicting crack path propagation of a pre-cracked plate based on crystal plasticity. The method first obtains stress-strain data and grain information of an aluminum plate through tensile tests and EBSD characterization, and constructs a finite element model of the true morphology of the grains. Subsequently, a crystal plasticity constitutive model is written using a FORTRAN subroutine, and simulation is performed in combination with the bilinear cohesion criterion and the maximum shear strain criterion. The best fitting parameters are determined by fitting multiple simulations with experimental data. Furthermore, different grain pattern models are established, the crack propagation path is predicted and compared with the experimental results to determine a suitable grain model. Finally, the influence of plates of different thicknesses on the tensile properties is studied, a multi-scale grain model is established for simulation, and the simulation is compared with the experimental results, providing method guidance for predicting the fracture behavior of aluminum plates of different thicknesses.

Description

Technical Field

[0001] The present invention relates to the technical field of fracture crack propagation prediction, and in particular to a method and system for predicting crack path propagation of a pre-cracked plate based on crystal plasticity. Background Art

[0002] In the field of materials science, especially in the study of fracture mechanics and crystal plasticity theory, how to accurately predict the damage and fracture behavior of materials under different loading conditions has always been the focus of researchers. In existing research, some progress has been made by combining different damage criteria with crystal plasticity theory, providing a powerful tool for predicting material damage and fracture.

[0003] Crystal plasticity theory takes into account the influence of the microscopic lattice structure of the material on plastic deformation and can more accurately describe the mechanical behavior of the material. The damage criterion is the key to judging the initiation and evolution of material damage. At present, there are many damage criteria, such as the cohesion criterion and the maximum shear strain criterion, each of which has certain advantages in different application scenarios.

[0004] However, although these studies have improved the accuracy of prediction to a certain extent, the following problems still exist when dealing with cracked plates of different thicknesses: due to their special geometric characteristics and mechanical properties, crack propagation paths and fracture mechanisms of cracked plates of different thicknesses often have significant differences. Therefore, how to select appropriate damage criteria to accurately predict the damage and fracture behavior of cracked plates of different thicknesses has become an urgent problem to be solved. Summary of the invention

[0005] At present, most simulation studies focus on two-dimensional models or three-dimensional models of fixed size, and do not fully consider the impact of plate thickness changes on fracture morphology. The present invention breaks through this limitation and simulates the mechanical properties and fracture modes of pre-cracked aluminum plates of different thicknesses by combining the crystal plasticity finite element method (CPFEM) with the two damage criteria of bilinear cohesion (CZM) and maximum shear strain (MSS), and provides a method for predicting crack path propagation of pre-cracked plates based on crystal plasticity. The method specifically includes the following steps:

[0006] S1: Acquire microscopic data of the sample plate, process the microscopic data, extract physical information of the grains of the sample plate, and construct a finite element model of the real morphology of the grains based on the physical information;

[0007] S2: Based on the bilinear cohesion criterion and the maximum shear stress criterion, a crystal plasticity constitutive model is constructed, and the crystal plasticity constitutive model is used to perform multiple crystal plasticity finite element simulations on the finite element model according to boundary conditions to obtain microscopic deformation parameters of the crystal material during the plastic deformation process;

[0008] S3: fitting the micro deformation parameters with the stress-strain data of the sample plate during the tensile test to determine the fitting parameters during the plastic deformation process;

[0009] S4: Based on the fitting parameters, multiple mode grain models are established, and different mode grain models are simulated using the crystal plasticity constitutive model. The simulation results are compared with the experimental results to determine the grain model that meets the prediction conditions, and the crack propagation path of the pre-cracked plate to be predicted is predicted using the grain model.

[0010] In one embodiment of the present invention, the crystal plasticity constitutive model includes a damage evolution model of bilinear cohesion and a damage evolution model of maximum slip shear strain.

[0011] In one embodiment of the present invention, the method for constructing the damage evolution model of the bilinear cohesive force includes:

[0012] For opening, sliding and tearing crack damage, the stress of the cohesive element in the normal direction and two orthogonal tangential directions is analyzed:

[0013]

[0014] Among them, the subscripts n, s, and t represent the normal direction of the separation traction force T and the two tangential directions that are orthogonal to each other, σ n , σ s and σ t They represent the stress of the cohesive element in the n, s and t directions respectively, and σ max , τ max Indicates the maximum stress that the cohesive interface can withstand in the normal and tangential directions; They represent the initial thickness of the cohesive unit in the normal and tangential directions respectively; δ represents the separation traction force T at the cohesive interface with the relative displacement of the upper and lower surfaces;

[0015] Among them, the critical fracture energy of the cohesive force unit in the n direction, s direction and t direction is expressed as:

[0016]

[0017] In the formula, and represent the critical fracture energy of the cohesive unit in the n, s and t directions respectively; represents the separation displacement of the cohesive element in the n direction, represents the separation displacement of the cohesive force unit in the s direction, represents the separation displacement of the cohesive force unit in the t direction;

[0018] For mixed cracking damage, the strains in the three directions of the cohesive element are defined by the initial thickness T0 of the cohesive element in the undamaged state and the separation displacement of the element node from its initial unloading position:

[0019]

[0020] Among them, ε n represents the strain in the n direction, ε s represents the strain in the s direction, ε t represents the strain in the t direction;

[0021] Based on the strain ε in three directions in the cohesive element n , ε s and ε t , and the stress displacement is obtained:

[0022]

[0023] Among them, δ m is the effective displacement, which is used to describe the equivalent damage evolution parameter under the combination of normal deformation and tangential deformation of the fracture interface. m ) represents the damage evolution, represents the initial separation displacement of the cohesive unit, represents the separation displacement corresponding to the complete separation failure of the cohesive unit interface, K nn , K ss , K tt They represent the stiffness of the cohesive force model in the normal direction and the two tangential directions respectively.

[0024] In one embodiment of the present invention, the initial damage criterion of the damage evolution model of the bilinear cohesive force is:

[0025]

[0026] in, and They represent the maximum stress that the cohesive force interface can withstand in the normal direction and two orthogonal tangential directions respectively; <> means that the normal stress of the cohesive force model is not negative, that is, the cohesive force unit is not compressed in the normal direction.

[0027] In one embodiment of the present invention, the effective displacement δ m The conditions met are:

[0028]

[0029] Among them, δ n represents the displacement of the separation traction force T in the n direction, δ srepresents the displacement of the separation traction force T in the s direction, δ t Represents the displacement of the separation traction force T in the t direction.

[0030] In one embodiment of the present invention, the method for constructing the damage evolution model of the maximum slip shear strain includes:

[0031] When the maximum slip shear strain in all slip systems reaches the specified critical value, damage begins to occur and accumulate, and the damage degree D of the material is expressed as:

[0032]

[0033] Among them, γ m is the maximum shear strain in all slip systems; γ m,ini is the critical value at the beginning of damage, that is, when the maximum shear strain in all slip systems reaches this value, the material begins to be damaged; γ m,max It is the critical value when the damage degree is the largest, that is, when the maximum shear strain in all slip systems reaches this value, the damage degree of the material reaches the upper limit value D max ; M is the damage evolution index of the material;

[0034] Based on the damage degree D of the material, the expression of effective shear stress is obtained:

[0035]

[0036] Where τ represents the shear stress tensor;

[0037] Substituting the expression of effective shear stress into equation (7) yields:

[0038]

[0039]

[0040] Therefore, the slip system strength The calculation formula evolves into:

[0041]

[0042] Among them, h αβ is the slip hardening modulus, and the variation range in the α and β slip systems is summed over all slip systems, so h αα and h αβ represent the self-hardening modulus and potential hardening modulus respectively.

[0043] In one embodiment of the present invention, the microscopic deformation parameters of the crystalline material during plastic deformation include material constants in the elastic stage, cohesive force parameters of grain boundary fracture and intracrystalline fracture, and maximum shear strain damage parameters, which are obtained by:

[0044] The actual microscopic model is given boundary conditions according to the actual experimental conditions to conduct multiple crystal plasticity finite element simulations to obtain the material constants in the elastic stage;

[0045] The UMAT subroutine written based on the two damage criteria, the bilinear cohesion criterion and the maximum shear stress criterion, was used to perform multiple crystal plasticity finite element simulations to determine the cohesion parameters of grain boundary fracture and intragranular fracture as well as the maximum shear strain damage parameters.

[0046] In one embodiment of the present invention, the boundary condition is to fix one end of the sample plate, apply a displacement load to the other end of the sample plate, and calibrate the obtained simulation data results with the stress-strain response data obtained from the tensile test.

[0047] In one embodiment of the present invention, the method for acquiring microscopic data includes: characterizing the tensile fracture of the sample plate using electron backscatter diffraction technology to obtain the microscopic data of the sample plate.

[0048] Based on the same inventive concept, the present invention also provides a system for predicting crack path propagation of a pre-cracked plate based on crystal plasticity, which is used to implement the method for predicting crack path propagation of a pre-cracked plate. The prediction system includes the following modules:

[0049] A finite element model building module for the real morphology of grains, which is used to obtain microscopic data of the sample plate, process the microscopic data, extract physical information of the grains of the sample plate, and build a finite element model of the real morphology of the grains based on the physical information;

[0050] A micro deformation parameter acquisition module is used to construct a crystal plasticity constitutive model based on a bilinear cohesion criterion and a maximum shear stress criterion, and to use the crystal plasticity constitutive model to perform multiple crystal plasticity finite element simulations on the finite element model according to boundary conditions to obtain micro deformation parameters of the crystal material during the plastic deformation process;

[0051] A fitting parameter calculation module, used to fit the micro deformation parameters with the stress-strain data of the sample plate during the tensile test to determine the fitting parameters during the plastic deformation process;

[0052] The crack propagation path prediction module is used to establish multiple mode grain models based on the fitting parameters, simulate different mode grain models using the crystal plasticity constitutive model, compare the simulation results with the experimental results, determine the grain model that meets the prediction conditions, and use the grain model to predict the crack propagation path of the pre-cracked plate to be predicted.

[0053] The above technical solution of the present invention has the following advantages compared with the prior art:

[0054] 1. By combining the crystal plasticity constitutive model and two damage criteria (bilinear cohesion criterion and maximum shear stress criterion), the present invention can more accurately simulate and predict the crack propagation path of the pre-cracked plate during the plastic deformation process, which is useful for identifying potential risk areas in advance in practical applications, so as to take corresponding preventive or remedial measures.

[0055] 2. The present invention establishes multiple grain models and performs simulation comparisons. The method can determine the grain model that best meets the prediction conditions. This means that the method has stronger adaptability and flexibility and can be applied to the crack path prediction of pre-cracked plates with different materials and different grain structures.

[0056] 3. By deeply understanding and predicting the crack propagation path, this method can provide important theoretical basis and practical guidance for optimizing material design and improving material performance. It can be applied to aerospace, automobile manufacturing, construction engineering and other fields, and the application of this method will help improve product safety and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

[0058] Figure 1 It is a flow chart for realizing a method for predicting crack path propagation of a pre-cracked plate based on crystal plasticity provided in an embodiment of the present invention;

[0059] Figure 2 It is the algorithm flow chart of CPFEM coupling CZM damage criterion and MSS damage criterion respectively;

[0060] Figure 3 (a) shows the grain orientation diagram, (b) shows the pole figure, (c) shows the grain size distribution, (d) shows the tensile test device, and (e) shows the tensile specimens with different thicknesses.

[0061] Figure 4 In (a), I represents the actual morphology distribution of grains, II represents the normal distribution of Voronoi polygons, III represents the normal distribution of grain growth morphology, IV represents the uniform distribution of Voronoi polygons, (b) represents the simulation results based on the maximum shear strain damage model, and (c) represents the simulation results based on the bilinear cohesive damage model;

[0062] Figure 5(a) shows the tensile test results, (b) shows the 2D, 2.5D and 3D grain models constructed based on the maximum shear strain damage criterion and the bilinear cohesion damage criterion, respectively, (c) shows the comparison between the simulation results of the bilinear cohesion damage model and the experimental data, and (d) shows the comparison between the simulation results of the maximum shear strain damage model and the experimental data.

[0063] Figure 6 It is a structural diagram of a crack path propagation prediction system for a pre-cracked plate based on crystal plasticity provided in an embodiment of the present invention;

[0064] Explanation of the reference numerals in the specification: 100, a finite element model building module for the real morphology of grains; 200, a micro deformation parameter acquisition module; 300, a fitting parameter calculation module; 400, a crack propagation path prediction module. DETAILED DESCRIPTION

[0065] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0066] Embodiment 1

[0067] Reference Figures 1-2 As shown, the present invention provides a method for predicting crack path propagation of a pre-cracked plate based on crystal plasticity, mainly through Figure 2 The CPFEM model that couples the CZM damage criterion with the MSS damage criterion in the proposed method realizes the crack path prediction of the pre-cracked plate. The method specifically includes the following steps:

[0068] S1: Select an aluminum plate as a sample plate, characterize the tensile fracture of the sample plate using electron backscatter diffraction technology (EBSD), obtain microscopic data of the sample plate, process the microscopic data using the MTEX ​​toolbox in MATLAB software, extract the physical information of the grains of the sample plate, and construct a finite element model of the real morphology of the grains based on the physical information;

[0069] S2: Based on the bilinear cohesion criterion and the maximum shear stress criterion, a crystal plasticity constitutive model is constructed using a FORTRAN subroutine. In the ABAQUS finite element analysis software, based on the crystal plasticity constitutive model, multiple crystal plasticity finite element simulations are performed on the finite element model according to boundary conditions to obtain the microscopic deformation parameters of the crystal material during the plastic deformation process;

[0070] S3: cutting the sample plate into standard specimens for tensile testing, obtaining stress-strain data, and fitting the microscopic deformation parameters with the stress-strain data to determine the fitting parameters in the plastic deformation process;

[0071] S4: Based on the fitting parameters, multiple mode grain models are established, and different mode grain models are simulated using the crystal plasticity constitutive model. The simulation results are compared with the experimental results to determine the grain model that meets the prediction conditions, and the crack propagation path of the pre-cracked plate to be predicted is predicted using the grain model.

[0072] In this embodiment, the crystal plasticity constitutive model includes a damage evolution model of bilinear cohesive force and a damage evolution model of maximum slip shear strain.

[0073] The method for constructing the damage evolution model of the bilinear cohesive force includes:

[0074] For opening, sliding and tearing crack damage, the stress of the cohesive element in the normal direction and two orthogonal tangential directions is analyzed:

[0075]

[0076] Among them, the subscripts n, s, and t represent the normal direction of the separation traction force T and the two tangential directions that are orthogonal to each other, σ n , σ s and σ t They represent the stress of the cohesive element in the n, s and t directions respectively, and σ max , τ max Indicates the maximum stress that the cohesive interface can withstand in the normal and tangential directions; They represent the initial thickness of the cohesive unit in the normal and tangential directions respectively; δ represents the separation traction force T at the cohesive interface with the relative displacement of the upper and lower surfaces;

[0077] Among them, the critical fracture energy of the cohesive force unit in the n direction, s direction and t direction is expressed as:

[0078]

[0079] In the formula, and represent the critical fracture energy of the cohesive unit in the n, s and t directions respectively; represents the separation displacement of the cohesive element in the n direction, represents the separation displacement of the cohesive force unit in the s direction, represents the separation displacement of the cohesive force unit in the t direction;

[0080] For mixed cracking damage, the strains in the three directions of the cohesive element are defined by the initial thickness T0 of the cohesive element in the undamaged state and the separation displacement of the element node from its initial unloading position:

[0081]

[0082] Among them, ε n represents the strain in the n direction, ε s represents the strain in the s direction, ε t represents the strain in the t direction;

[0083] Based on the strain ε in three directions in the cohesive element n , ε s and ε t , and the stress displacement is obtained:

[0084]

[0085] Among them, δ m is the effective displacement, which is used to describe the equivalent damage evolution parameter under the combination of normal deformation and tangential deformation of the fracture interface. m ) represents the damage evolution, represents the initial separation displacement of the cohesive unit, represents the separation displacement corresponding to the complete separation failure of the cohesive unit interface, K nn , K ss , K tt They represent the stiffness of the cohesive force model in the normal direction and the two tangential directions respectively.

[0086] Furthermore, the initial damage criterion of the damage evolution model of the bilinear cohesive force is:

[0087]

[0088] in, and They represent the maximum stress that the cohesive force interface can withstand in the normal direction and two orthogonal tangential directions respectively; <> means that the normal stress of the cohesive force model is not negative, that is, the cohesive force unit is not compressed in the normal direction.

[0089] Specifically, the effective displacement δ m The conditions met are:

[0090]

[0091] Among them, δ n represents the displacement of the separation traction force T in the n direction, δ s represents the displacement of the separation traction force T in the s direction, δ t Represents the displacement of the separation traction force T in the t direction.

[0092] In this embodiment, the method for constructing the damage evolution model of the maximum slip shear strain includes:

[0093] When the maximum slip shear strain in all slip systems reaches the specified critical value, damage begins to occur and accumulate, and the damage degree D of the material is expressed as:

[0094]

[0095] Among them, γ m is the maximum shear strain in all slip systems; γ m,ini is the critical value at the beginning of damage, that is, when the maximum shear strain in all slip systems reaches this value, the material begins to be damaged; γ m,max It is the critical value when the damage degree is the largest, that is, when the maximum shear strain in all slip systems reaches this value, the damage degree of the material reaches the upper limit value D max ; M is the damage evolution index of the material;

[0096] Based on the damage degree D of the material, the expression of effective shear stress is obtained:

[0097]

[0098] Where τ represents the shear stress tensor;

[0099] Substituting the expression of effective shear stress into equation (7) yields:

[0100]

[0101]

[0102] Therefore, the slip system strength The calculation formula evolves into:

[0103]

[0104] Among them, h αβ is the slip hardening modulus, and the variation range in the α and β slip systems is summed over all slip systems, so h αα and h αβ Represent the self-hardening modulus and potential hardening modulus respectively.

[0105] In this embodiment, the microscopic deformation parameters of the crystalline material during the plastic deformation process include material constants in the elastic stage, cohesive force parameters of grain boundary fracture and intracrystalline fracture, and maximum shear strain damage parameters, which are obtained by:

[0106] In the ABAQUS finite element analysis software, boundary conditions are assigned to the actual microscopic model according to the actual experimental conditions, and the UMAT subroutine is used to perform multiple crystal plasticity finite element simulations to obtain the material constants in the elastic stage;

[0107] The UMAT subroutine written based on the two damage criteria of bilinear cohesion criterion and maximum shear stress criterion was used for multiple crystal plastic finite element simulations to determine the cohesion parameters of grain boundary fracture and intragranular fracture and the maximum shear strain damage parameters. In this embodiment, the cohesion grain boundary fracture parameter stiffness E is 42000Mpa, the maximum nominal stress T is 220Mpa, and the interface energy fracture critical value G is 0.00012N / mm; the cohesion intergranular fracture parameter stiffness E is 42000Mpa, the maximum nominal stress T is 200Mpa, and the interface energy fracture critical value G is 0.00015N / mm; the critical value γ at the onset of maximum shear strain damage m,ini is 0.1, the critical value γ when the damage degree is maximum m,max is 0.4, the exponent M of the damage evolution order is 1, and the damage degree reaches the upper limit value D max is 0.8.

[0108] In step S2, the finite element model is subjected to multiple crystal plastic finite element simulations according to boundary conditions, wherein one end of the aluminum plate is fixed and a displacement load is applied to the other end of the aluminum plate, and the obtained simulation data results are calibrated with the stress-strain response data obtained from the tensile test. Figure 3 (a) to (c) show the grain orientation diagram, pole figure and grain size distribution bar diagram, respectively. Figure 3 (d) and (e), the material constants of the aluminum plate in the elastic stage are finally determined to be C11: 106750Mpa, C12: 64410Mpa and C44: 28340Mpa, with reference to the shear rate is 0.001, the strain rate sensitivity factor n is 10, the plasticity parameter h0 is 280Mpa, τ s It is 24.15Mpa and τ0 is 20Mpa.

[0109] In step S4, Figure 4 As shown in (a), four different modes of grain models are established. The morphological distribution of grains is (I) actual morphological distribution of grains, (II) normal distribution of Voronoi polygons, (III) normal distribution of grain growth morphology, and (IV) uniform distribution of Voronoi polygons. The stress-strain data obtained by simulating based on the MSS model and the CZM model are compared with the experimental results. The experimental results are shown in Figure 4 (b) and Figure 4 As shown in (c), the MSS model has little effect on the results due to the lack of grain boundary insertion; while in the CZM model, the grain morphology has a greater effect on the stress-strain curve, but it is also within a reasonable range. Considering various factors, the uniform model III should be selected to obtain higher computational efficiency and convergence.

[0110] In order to explore the effect of different thickness plates on tensile properties, the material selected for the experiment was 1060 aluminum alloy. Aluminum plates with thicknesses of 1mm, 5mm, and 10mm were cut into standard tensile specimens and cracks were pre-set on one side of the middle of the specimens. Quasi-static tensile tests were all conducted on an MTS Landmark 370.10 testing machine. The loading speed of the uniaxial tensile test was 2mm / min. A room temperature extensometer was used to measure the strain of the specimen during tension. Tensile tests were conducted on pre-cracked specimens with thicknesses of 1mm, 5mm, and 15mm and crack lengths fixed at 1.5mm. The fracture morphology and mechanical properties of these specimens are shown in Figure 2. Figure 4 As shown. Three grain models of different scales, 2D, 2.5D and 3D, were established. Two damage criteria were used to simulate the three different scale models. The simulated crack extension results were compared with the experimental results.

[0111] from Figure 5 As can be seen in (a), as the thickness increases, a ductile-brittle transition occurs. Figure 4 This is also demonstrated by the stress-strain curves in (c). In addition, 2D, 2.5D, and 3D models with two failure criteria were established using CPFEM to describe the effect of specimen thickness. Figure 5 (b) and (c) also give the stress contours and mechanical property comparisons between the two failure criteria and the experiment. For all specimens, the three finite element models using the MSS criterion showed similar fracture modes and mechanical behaviors to the experiment compared with the CZM. In addition, the 2D model and the 2.5D model using the CZM have the same number of cohesive elements inserted, so the stress-strain curves are similar, as shown in Figure 2. Figure 5 (c). On the other hand, inserting more cohesive elements in the 3D model leads to higher stress-strain curves. Generally speaking, in the MSS criterion, the damage process of each element is calculated independently, which provides a more effective method for evaluating the overall mechanical behavior of metal materials.

[0112] Embodiment 2

[0113] Based on the same inventive concept as in Example 1, Figure 6 As shown, the present invention also provides a system for predicting crack path propagation of a pre-cracked plate based on crystal plasticity, which is used to implement the method for predicting crack path propagation of a pre-cracked plate, and the prediction system includes the following modules:

[0114] The finite element model construction module 100 of the real grain morphology is used to obtain the microscopic data of the sample plate, process the microscopic data through the MTEX ​​toolbox in the MATLAB software, extract the physical information of the grains of the sample plate, and construct the finite element model of the real grain morphology based on the physical information;

[0115] A micro deformation parameter acquisition module 200 is used to construct a crystal plasticity constitutive model based on a bilinear cohesion criterion and a maximum shear stress criterion using a FORTRAN subroutine, and in an ABAQUS finite element analysis software, based on the crystal plasticity constitutive model, perform multiple crystal plasticity finite element simulations on the finite element model according to boundary conditions to obtain micro deformation parameters of the crystal material during the plastic deformation process;

[0116] A fitting parameter calculation module 300 is used to fit the micro deformation parameters with the stress-strain data of the sample plate during the tensile test to determine the fitting parameters during the plastic deformation process;

[0117] The crack propagation path prediction module 400 is used to establish multiple mode grain models based on the fitting parameters, simulate different mode grain models using the crystal plasticity constitutive model, compare the simulation results with the experimental results, determine the grain model that meets the prediction conditions, and use the grain model to predict the crack propagation path of the pre-cracked plate to be predicted.

[0118] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0119] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0120] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1A function specified in one or more boxes.

[0121] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0122] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for predicting crack path propagation of a pre-cracked plate based on crystal plasticity, characterized in that: The following steps are involved: S1: Acquire microscopic data of the sample plate, process the microscopic data, extract physical information of the grains of the sample plate, and construct a finite element model of the real morphology of the grains based on the physical information; S2: Based on the bilinear cohesion criterion and the maximum shear stress criterion, a crystal plasticity constitutive model is constructed, and the crystal plasticity constitutive model is used to perform multiple crystal plasticity finite element simulations on the finite element model according to boundary conditions to obtain microscopic deformation parameters of the crystal material during the plastic deformation process; S3: fitting the micro deformation parameters with the stress-strain data of the sample plate during the tensile test to determine the fitting parameters during the plastic deformation process; S4: Based on the fitting parameters, multiple mode grain models are established, and different mode grain models are simulated using the crystal plasticity constitutive model. The simulation results are compared with the experimental results to determine the grain model that meets the prediction conditions, and the crack propagation path of the pre-cracked plate to be predicted is predicted using the grain model.

2. The method for predicting crack path propagation of a pre-cracked plate based on crystal plasticity according to claim 1, characterized in that: The crystal plasticity constitutive model includes a damage evolution model of bilinear cohesive force and a damage evolution model of maximum slip shear strain.

3. The method for predicting crack path propagation of a pre-cracked plate based on crystal plasticity according to claim 2, characterized in that: The method for constructing the damage evolution model of the bilinear cohesive force includes: For opening, sliding and tearing crack damage, the stress of the cohesive element in the normal direction and two orthogonal tangential directions is analyzed: Among them, the subscripts n, s, and t represent the normal direction of the separation traction force T and the two tangential directions of the orthogonal relationship, σ n , σ s and σ t They represent the stress of the cohesive element in the n, s and t directions respectively, and σ max , τ max Indicates the maximum stress that the cohesive interface can withstand in the normal and tangential directions; They represent the initial thickness of the cohesive unit in the normal and tangential directions respectively; δ represents the separation traction force T at the cohesive interface with the relative displacement of the upper and lower surfaces; Among them, the critical fracture energy of the cohesive force unit in the n direction, s direction and t direction is expressed as: In the formula, and represent the critical fracture energy of the cohesive unit in the n, s and t directions respectively; represents the separation displacement of the cohesive element in the n direction, represents the separation displacement of the cohesive force unit in the s direction, represents the separation displacement of the cohesive force unit in the t direction; For mixed cracking damage, the strains in the three directions of the cohesive element are defined by the initial thickness T0 of the cohesive element in the undamaged state and the separation displacement of the element node from its initial unloading position: Among them, ε n represents the strain in the n direction, ε s represents the strain in the s direction, ε t represents the strain in the t direction; Based on the strain ε in three directions in the cohesive element n , ε s and ε t , and the stress displacement is obtained: Among them, δ m is the effective displacement, which is used to describe the equivalent damage evolution parameter under the combination of normal deformation and tangential deformation of the fracture interface. m ) represents the damage evolution, represents the initial separation displacement of the cohesive unit, represents the separation displacement corresponding to the complete separation failure of the cohesive unit interface, K nn , K ss , K tt They represent the stiffness of the cohesive force model in the normal direction and two orthogonal tangential directions respectively.

4. The method for predicting crack path propagation of a pre-cracked plate based on crystal plasticity according to claim 3 is characterized in that: The initial damage criterion of the damage evolution model of bilinear cohesion is: in, and They represent the maximum stress that the cohesive force interface can withstand in the normal direction and two orthogonal tangential directions respectively; <> means that the normal stress of the cohesive force model is not negative, that is, the cohesive force unit is not compressed in the normal direction.

5. The method for predicting crack path propagation of a pre-cracked plate based on crystal plasticity according to claim 3, characterized in that: The effective displacement δ m The conditions met are: Among them, δ n represents the displacement of the separation traction force T in the n direction, δ s represents the displacement of the separation traction force T in the s direction, δ t Represents the displacement of the separation traction force T in the t direction.

6. The method for predicting crack path propagation of a pre-cracked plate based on crystal plasticity according to claim 1, characterized in that: The method for constructing the damage evolution model of the maximum slip shear strain includes: When the maximum slip shear strain in all slip systems reaches the specified critical value, damage begins to occur and accumulate, and the damage degree D of the material is expressed as: Among them, γ m is the maximum shear strain in all slip systems; γ m,ini is the critical value at the beginning of damage, that is, when the maximum shear strain in all slip systems reaches this value, the material begins to be damaged; γ m,max It is the critical value when the damage degree is the largest, that is, when the maximum shear strain in all slip systems reaches this value, the damage degree of the material reaches the upper limit value D max ; M is the damage evolution index of the material; Based on the damage degree D of the material, the expression of effective shear stress is obtained: Where τ represents the shear stress tensor; Substituting the expression of effective shear stress into equation (7) yields: in, represents the effective shear stress in direction α, represents the slip rate, It represents the slip amount after the interaction between slip systems reaches the peak value, g α is a variable representing the current strength of the slip system, and n represents the rate-dependent sensitivity coefficient; Therefore, the slip system strength The calculation formula evolves into: Among them, h αβ is the slip hardening modulus, and the variation range in the α and β slip systems is summed over all slip systems, so h αα and h αβ represent the self-hardening modulus and potential hardening modulus respectively.

7. The method for predicting crack path propagation of a pre-cracked plate based on crystal plasticity according to claim 1, characterized in that: The microscopic deformation parameters of the crystalline material during plastic deformation include material constants in the elastic stage, cohesive force parameters of grain boundary fracture and intracrystalline fracture, and maximum shear strain damage parameters, which are obtained by: The actual microscopic model is given boundary conditions according to the actual experimental conditions to conduct multiple crystal plasticity finite element simulations to obtain the material constants in the elastic stage; The UMAT subroutine written based on the two damage criteria, the bilinear cohesion criterion and the maximum shear stress criterion, was used to perform multiple crystal plasticity finite element simulations to determine the cohesion parameters of grain boundary fracture and intragranular fracture as well as the maximum shear strain damage parameters.

8. The method for predicting crack path propagation of a pre-cracked plate based on crystal plasticity according to claim 1, characterized in that: The boundary condition is to fix one end of the sample plate, apply a displacement load to the other end of the sample plate, and calibrate the obtained simulation data results with the stress-strain response data obtained from the tensile test.

9. The method for predicting crack path propagation of a pre-cracked plate based on crystal plasticity according to claim 1, characterized in that: The method for acquiring microscopic data comprises: characterizing the tensile fracture of the sample plate by using electron backscatter diffraction technology to obtain the microscopic data of the sample plate.

10. A crack path propagation prediction system for a pre-cracked plate based on crystal plasticity, characterized in that: Used to implement the method for predicting crack path propagation of a pre-cracked plate according to any one of claims 1 to 9, the prediction system comprises the following modules: A finite element model building module for the real morphology of grains, which is used to obtain microscopic data of the sample plate, process the microscopic data, extract physical information of the grains of the sample plate, and build a finite element model of the real morphology of the grains based on the physical information; A micro deformation parameter acquisition module is used to construct a crystal plasticity constitutive model based on a bilinear cohesion criterion and a maximum shear stress criterion, and to use the crystal plasticity constitutive model to perform multiple crystal plasticity finite element simulations on the finite element model according to boundary conditions to obtain micro deformation parameters of the crystal material during the plastic deformation process; A fitting parameter calculation module, used to fit the micro deformation parameters with the stress-strain data of the sample plate during the tensile test to determine the fitting parameters during the plastic deformation process; The crack propagation path prediction module is used to establish multiple mode grain models based on the fitting parameters, simulate different mode grain models using the crystal plasticity constitutive model, compare the simulation results with the experimental results, determine the grain model that meets the prediction conditions, and use the grain model to predict the crack propagation path of the pre-cracked plate to be predicted.

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