Dynamic fracture process simulation and fracture toughness evaluation method for porous structure

Abstract

The invention provides a porous structure-oriented dynamic fracture process simulation and fracture toughness evaluation method, and relates to the technical field of fracture toughness and safety evaluation of structures under the action of dynamic loads. According to the method, an existing second-order phase field dynamic fracture simulation method is expanded to a fourth-order method, so that a C1 continuous primary function is constructed by adopting a PHT spline based on isogeometric analysis; in order to improve the calculation efficiency, a grid adaptive refinement strategy is introduced into a numerical value implementation scheme, a transmission scheme comprising a node field quantity and an integral point field quantity is formulated, most of the existing adaptive phase field fracture methods based on isogeometric analysis neglect the field quantity on a transmission integral point, and the field quantity on the transmission integral point cannot be reduced. Therefore, the phenomenon of crack healing possibly occurring in the loading process of the structure is caused. Compared with a method for carrying out calculation by adopting a fixed grid, the method can greatly improve the calculation efficiency; the calculation result of the method converges to grid refinement and time increment step reduction, and the stability of the calculation result can be effectively guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of fracture toughness and safety assessment of structures under dynamic loads, and in particular to a dynamic fracture process simulation and fracture toughness assessment method for porous structures. Background Art

[0002] Porous structures have the advantages of light weight, vibration isolation and sound absorption, and high damage tolerance, and are widely used in the fields of vehicles, biotechnology, and aerospace. However, common harsh working environments such as impact and high overload can easily cause porous structures to fail due to the initiation and expansion of microcracks. Considering the characteristics of the application field of porous structures, once such local component failure occurs, it is likely to cause serious consequences, causing huge economic losses and casualties to society. Due to the advantages of numerical simulation such as good repeatability, working conditions that can be set as needed, and low cost-effectiveness, investigating the dynamic fracture process and fracture toughness of porous structures through numerical simulation methods has become a hot topic of research today.

[0003] The current calculation methods used for simulation of dynamic fracture process and fracture toughness evaluation of porous structures have the following defects:

[0004] (1) Conventional fracture simulation methods can only simulate simple fracture behaviors and still face many challenges in describing and simulating complex dynamic fracture problems. The phase field fracture method regularizes sharp cracks into crack bands with a certain scale, eliminating the grid dependence phenomenon caused by the use of conventional methods, and can describe complex behaviors such as structural crack initiation, expansion, merging, and bifurcation. However, the existing phase field dynamic fracture simulation methods are mostly based on the second-order regularization theory, which has high requirements on the grid size. The fourth-order regularization theory can relax the requirements on the grid size when regularizing sharp cracks into crack bands with a certain scale. Therefore, it is of great significance to expand the existing second-order phase field dynamic fracture simulation method to the fourth-order method.

[0005] (2) The main strategy used in phase field fracture simulation is to start the calculation from a fixed grid, which needs to be locally refined in the expected crack propagation area. Due to the complexity of the dynamic fracture mode, it is difficult to predict the crack propagation path, so the pre-processing process of the calculation will be very complicated, and even the global mesh refinement is required to ensure the calculation accuracy, which leads to extremely high calculation costs. Summary of the invention

[0006] Purpose of the invention: In view of the deficiencies in the prior art, the present invention proposes a method for simulating the dynamic fracture process and evaluating the fracture toughness of porous structures.

[0007] To achieve the above objectives, the present invention proposes a method for simulating a dynamic fracture process and evaluating fracture toughness of a porous structure, the method comprising the following steps:

[0008] A typical porous structure workpiece is selected as a sample; the fracture process of the sample is modeled and its one-dimensional fracture field model is constructed;

[0009] Analyzing the one-dimensional fracture field model to obtain the displacement field control equation and the fracture field control equation of the porous structure workpiece;

[0010] The displacement field control equation and the fracture field control equation are spatially discretized using PHT splines to obtain an initial fracture assessment model;

[0011] On the basis of the initial fracture assessment model, an adaptive grid refinement strategy based on phase field variables is introduced, and a transmission scheme of each field quantity is introduced for the refined grid to obtain an optimized fracture assessment model;

[0012] The digital modeling of the target porous structure workpiece to be evaluated is imported into the optimized fracture evaluation model, the fracture process simulation and fracture toughness evaluation are completed, and the evaluation result is output.

[0013] In a further embodiment, the fracture process of the sample is modeled to construct a one-dimensional fracture field model. The expression of the one-dimensional fracture field model is as follows:

[0014]

[0015] Where l is the size parameter that controls the normalized width of the crack; d = 0 means that the material is not damaged, and d = 1 means that the material is completely damaged.

[0016] In a further embodiment, the one-dimensional fracture field model is analyzed to obtain the displacement field control equation and the fracture field control equation of the porous structure workpiece, wherein the expression of the displacement field control equation is as follows:

[0017]

[0018] In the formula, σ represents the Cauchy stress; b represents the stress on the structure; ρ represents the material density; represents acceleration; n represents the unit vector of the external normal of the structure; t represents the surface force on the structure; u represents displacement; represents the displacement applied on the surface of the structure; Ω represents the structural area; Indicates the boundary where the surface force is applied; Ω u Represents the boundary to which the displacement is applied.

[0019] In a further embodiment, the one-dimensional fracture field model is analyzed to obtain the displacement field control equation and the fracture field control equation of the porous structure workpiece, wherein the fracture field control equation is expressed as follows:

[0020]

[0021] In the formula, represents the elastic energy density driving crack extension; G c Indicates the critical energy release rate of the material;

[0022] On the basis of the fracture field control equation, a historical variable function is introduced To avoid crack healing;

[0023] The historical variable function expression is as follows:

[0024]

[0025] Where ε represents strain and t is the total time of dynamic loading.

[0026] In a further embodiment, in the parameter space (ξ, η, ζ), the geometric representation of the PHT spline is as follows:

[0027]

[0028] In the formula, is the coordinate of the control point, s is the total number of control points, R i It is the basis function for constructing the shape functions used subsequently, and its form is as follows:

[0029]

[0030] In the formula, w i is the weight of the ith control point, N i Define basis functions for B-splines on a level T grid.

[0031] In a further embodiment, the displacement field control equation and the fracture field control equation are spatially discretized using PHT splines to obtain an initial fracture assessment model:

[0032]

[0033] In the formula, is the spatial discretization form of the displacement field control equation; K d d=F d is the spatial discretization form of the fracture field control equation;

[0034] M represents the overall stiffness matrix of inertia force; K u represents the displacement global stiffness matrix; F u Represents the overall stiffness matrix of external forces; K d represents the overall stiffness matrix of the fracture field; d represents the fracture field; F d Represents the cracking driving force and the global stiffness matrix.

[0035] In a further embodiment, based on the initial fracture assessment model, an adaptive mesh refinement strategy based on phase field variables is introduced, specifically including:

[0036] The structure with holes or gaps initially is realized by refining the mesh at the boundary of the two-phase materials, where the material corresponding to the mesh at the hole or gap is set as the hole material, and the mesh at other parts is identified as a solid and set according to its specific material properties;

[0037] After the numerical simulation begins, when cracks initiate or propagate, only those locations where the fracture field value is greater than the predetermined threshold will be marked and refined to the highest level of the grid.

[0038] In a further embodiment, a transmission scheme for each field quantity is introduced for the refined grid, specifically including:

[0039] The data on the grid nodes are transmitted using shape function projection;

[0040] The data transmission at the integration point adopts the method of shape function projection or directly inherits the value of the nearest integration point of the coarse grid.

[0041] The present invention also proposes an electronic device, which includes a processor and a memory storing computer program instructions; when the processor executes the computer program instructions, the above-mentioned dynamic fracture process simulation and fracture toughness evaluation method for porous structures is implemented.

[0042] The present invention also proposes a computer-readable storage medium, which stores at least one executable instruction. When the executable instruction is run on an electronic device, the electronic device executes the above-mentioned dynamic fracture process simulation and fracture toughness evaluation method for porous structures.

[0043] Beneficial effects: The dynamic fracture process simulation and fracture toughness evaluation method for porous structures proposed in the present invention relaxes the requirements for mesh size and can more accurately simulate the dynamic fracture behavior of the structure. In addition, in order to solve the problem of high computational cost of the phase field fracture method, the method introduces a mesh adaptive refinement strategy in the numerical implementation part, which can greatly reduce the cost of fracture simulation and is of great significance to promoting the application of the method in practical engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The dimensions and loading boundary conditions of the notched plate (left) and the initial mesh model (right).

[0045] Figure 2 This is the crack extension and corresponding mesh encryption process.

[0046] Figure 3Comparison of the crack propagation process between the method of the present invention, the second-order method and the results reported in the prior art.

[0047] Figure 4 Comparison of elastic energy and fracture energy between the method of the present invention, the second-order method and the results reported in the prior art.

[0048] Figure 5 Not transmitted The results obtained, transmission The obtained results are compared with those reported in the prior art.

[0049] Figure 6 Comparison results of elastic energy and fracture energy.

[0050] Figure 7 A schematic diagram of a structure containing a single circular hole.

[0051] Figure 8 This is a diagram showing the influence of the time increment on the final dynamic failure morphology.

[0052] Fig. 9 Plot of the effect of the time increment on the elastic / fracture energy evolution.

[0053] Fig.10 is the minimum grid size h min Impact diagram on the final dynamic failure shape.

[0054] Fig.11 is the minimum grid size h min Plot of the effect on the elastic / fracture energy evolution.

[0055] Fig.12 The structural dimensions and loading boundary conditions of the random multi-circular hole plate (left) and the initial mesh model (right).

[0056] Fig.13 The crack propagation and corresponding mesh encryption process of a random multi-circular hole plate.

[0057] Fig.14 The final dynamic fracture morphology of a plate with random multiple circular holes and the corresponding adaptive mesh model.

[0058] Fig.15 This is the evolution process of elastic energy and fracture energy of a random multi-circular hole plate. DETAILED DESCRIPTION

[0059] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is apparent to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features known in the art are not described.

[0060] This embodiment discloses a method for simulating a dynamic fracture process and evaluating fracture toughness for a porous structure, and the steps are as follows:

[0061] Step 1: Select a typical porous structure workpiece as a sample; model the fracture process of the sample and construct its one-dimensional fracture field model.

[0062] Furthermore, in the fourth-order phase field theory, the one-dimensional fracture field is defined as follows:

[0063]

[0064] Where l is the size parameter that controls the normalized width of the crack, d = 0 means that the material is not damaged, and d = 1 means that the material is completely damaged. Formula (1) is the solution of the following partial differential equation:

[0065]

[0066] The corresponding fracture energy density is given by:

[0067]

[0068] Therefore, the fracture energy can be approximated as:

[0069]

[0070] For a solid with an initial crack, assuming that the body force and surface traction it bears are b and t respectively, the total energy of the solid can be expressed as:

[0071]

[0072] Among them, ψ e is the elastic energy density, ψ k is the kinetic energy density. In order to consider the unilateral effect, the elastic energy density has the following decomposition form:

[0073]

[0074] in,

[0075]

[0076] ε i and n i are the eigenvalue and eigenvector of ε, <x> ± =(x±|x|) / 2, D is the dimension of the problem under study, λ and μ are Lame constants, g(d) = (1-d) 2 +κ is used to weaken the stretching energy. The kinetic energy density has the following form:

[0077]

[0078] Where ρ is the density of the material, For speed.

[0079] According to the variational principle, the first-order inverse of displacement in equation (5) is as follows:

[0080]

[0081] Among them, δ is the variational operator, is the acceleration. In order to save calculation time, the present invention uses the classic hybrid staggered solution method, that is, the anisotropy of the constitutive model is not considered when solving the displacement problem, but the anisotropy of the constitutive model is considered when solving the fracture problem (tensile energy drives fracture). Therefore, the Cauchy stress in formula (9) can be simplified to the following form:

[0082]

[0083] in, is the fourth-order elasticity tensor.

[0084] Step 2: Analyze the one-dimensional fracture field model to obtain the displacement field control equation and fracture field control equation of the porous structure workpiece.

[0085] Furthermore, the governing equations for the displacement problem are as follows:

[0086]

[0087] Similarly, the first-order derivative of equation (5) with respect to the fracture field is as follows:

[0088]

[0089] The governing equations for the fracture problem are as follows:

[0090]

[0091] In addition, in order to avoid the phenomenon of crack healing, a historical variable function is introduced as follows:

[0092]

[0093] Step 3: Use PHT splines to spatially discretize the displacement field control equation and the fracture field control equation to obtain an initial fracture assessment model.

[0094] Since solving equation (13) requires at least C1 continuous basis functions, the numerical discretization part of this method uses PHT splines based on isogeometric analysis, which can also conveniently perform mesh adaptation strategies. In the parameter space (ξ,η,ζ), the geometric representation of the PHT spline entity is as follows:

[0095]

[0096] in, is the coordinate of the control point, s is the total number of control points, R i It is the basis function for constructing the shape functions used subsequently, and its form is as follows:

[0097]

[0098] Among them, w i is the weight of the ith control point, N i Define basis functions for B-splines on a level T grid.

[0099] For the sake of clarity, the discretization of a 2D problem is used as an example. The displacement and fracture field on a certain unit can be approximately expressed as:

[0100] u=N u u e ,d=N d d e (17)

[0101] in,

[0102]

[0103] m is the number of control points of unit e, i = 1, 2, ..., m. The gradient and Laplace parts of equation (17) have the following forms:

[0104]

[0105] in,

[0106]

[0107] For the displacement problem, equation (9) can be discretized as

[0108]

[0109] in,

[0110]

[0111] Λ is the standard isogeometric unit stiffness matrix assembly operator, n elem is the total number of units, C is the fourth-order elastic tensor In addition, in order to solve the dynamic problem, this method adopts the implicit Newmark scheme as follows:

[0112]

[0113] in,

[0114]

[0115] Furthermore, by introducing equation (25) into equation (21), the linear solution form of the displacement problem can be obtained as follows:

[0116]

[0117] in,

[0118]

[0119] For the fracture problem, equation (12) can be discretized into the following linear solution form:

[0120] K d d=F d (30)

[0121] in,

[0122]

[0123]

[0124] Step 4: Based on the initial fracture assessment model, an adaptive grid refinement strategy based on phase field variables is introduced, and a transmission scheme of each field quantity is introduced for the refined grid to obtain an optimized fracture assessment model.

[0125] This section involves the grid adaptive refinement strategy and the transmission of refined data.

[0126] In the mesh refinement part, the initial structure containing holes or gaps is realized by refining the mesh at the boundary of the two-phase material, where the material corresponding to the mesh at the hole or gap is set to the hole material (the material parameters are very small), and the meshes at other parts can be identified as entities and set according to their specific material properties; after the numerical simulation starts, when the crack initiates or expands, only the parts with fracture field values ​​greater than a certain threshold (such as d≥0.8) will be marked and refined to the highest level of the mesh. In addition, in order to maintain the hierarchy of the overall mesh, adjacent meshes that do not meet the hierarchy requirements must also be marked and refined synchronously.

[0127] The data transmission part involves the data transmission of grid nodes and the data transmission of integration points. The data on the grid nodes can be directly transmitted by shape function projection, and the data transmission on the integration points can also be directly inherited from the value of the nearest integration point of the coarse grid in addition to the shape function projection. In order to simplify the numerical implementation scheme and improve the calculation efficiency, this method adopts the method of directly inheriting the value of the nearest integration point of the coarse grid to transmit the integration point data. It is worth noting that the value of the integration point of the method of the present invention is only the historical variable It plays a role in preventing crack healing. If the transmission of this historical variable is ignored, crack healing may occur in some loading steps, resulting in inaccurate calculation results. However, most of the current adaptive mesh refinement phase field fracture methods based on isogeometric analysis ignore the transmission of historical variables. The transmission of can only be used for static problems with monotonic loading, but cannot be directly used for complex dynamic crack propagation problems.

[0128] Step 5: Import the digital model of the target porous structure workpiece to be evaluated into the optimized fracture evaluation model, complete its fracture process simulation and fracture toughness evaluation, and output the evaluation results.

[0129] For example, in step 4, whether the grid needs to be refined is based on the numerical value of the fracture field at that location. If it is greater than or equal to 0.8, the grid at that location needs to be refined and refined to the set maximum grid level. At the same time, in order to maintain the hierarchy of the grid, adjacent grids also need to be refined synchronously.

[0130] For example, in step 5, a plate with a single circular hole and a plate with random multiple circular holes may be used to investigate the effectiveness and efficiency of the method.

[0131] In order to illustrate the effectiveness and superiority of the invention, the calculation method proposed by the present invention is used to reproduce the dynamic fracture problem given in the classic prior art. For this purpose, the same material parameters as in the prior art are used: elastic modulus of 32000MPa, Poisson's ratio of 0.2, density of 2450kg / m 3 , fracture energy constant 3N / m. The crack regularization scale parameter is 0.5mm and the time increment step is 0.1μs.

[0132] Figure 1 The middle left figure shows the size and boundary conditions of the plate studied in this classic dynamic fracture problem. The plate contains a prefabricated notch in the middle, and the upper and lower edges of the plate are subject to a constant stress of 1 MPa. Figure 1 The middle right figure shows the initial mesh model used in the simulation, in which the gap topology is approximately described by mesh refinement at the edge of the gap. It is worth noting that this mesh model is derived from a structured model containing 160 meshes (level 0 mesh), and the maximum level of refinement allowed is 5, so the minimum unit size in the mesh is h min =5 / 32mm.

[0133] Figure 2 The dynamic fracture of the notched plate and the corresponding mesh encryption process calculated by the method of the present invention are given. Obviously, the crack starts from the notch and propagates to the middle of the plate. After propagating a certain distance, the crack bifurcates, which is consistent with the results reported in the prior art (such as Figure 3 ). In addition, it can also be found that the method of the present invention can effectively perform mesh adaptive refinement in the crack propagation area.

[0134] Figure 3 and Figure 4 A comparison between the method of the present invention, the second-order method and the results reported in the prior art is given, including the results obtained by the method of the present invention and the second-order method using adaptive refinement and global encryption, respectively. Figure 3 Among them, (a) adaptive second-order method, (b) global encrypted second-order method, (c) adaptive fourth-order method, (d) global encrypted fourth-order method, and (e) results reported in the prior art. Figure 4 (a) elastic energy comparison, (b) fracture energy comparison.

[0135] It can be found that both the method of the present invention and the second-order method can reproduce the results reported in the prior art, and the results obtained by adaptive refinement are very similar to those obtained by global encryption, which illustrates the effectiveness of the present invention. Figure 4 The curve comparison given in shows that the results obtained by the method of the present invention are closer to the results reported in the prior art, which shows that the method of the present invention is superior to the existing second-order method.

[0136] In order to illustrate the transmission history variable of the present invention In order to eliminate the necessity of crack topology, the constant stress on the upper and lower boundaries is increased to 2.5 MPa to induce complex dynamic crack topology. Figure 5 The untransmitted The results obtained, transmission The results obtained are those reported in the prior art. Figure 5 (a) not transmitted (b) crack propagation process during transmission (c) The results reported in the prior art. The crack healing phenomenon may occur, and the final result obtained is different from the result of the prior art; when the transmission When the cracks are healed, the healing can be effectively avoided, and the obtained results are close to those of the prior art. Figure 6 The comparison results of elastic energy and fracture energy are given in Figure 6 (a) elastic energy comparison, (b) fracture energy comparison. An obvious curve drop can be found in the fracture energy, which indirectly confirms the existence of crack healing.

[0137] The highlights of this method are illustrated by investigating the dynamic fracture of a plate with a circular hole. For example, the calculation results of this method converge to the mesh refinement and the reduction of the time increment. Compared with the globally refined phase-field fracture simulation method, the method of the present invention can significantly improve the calculation efficiency. This method can be applied to complex porous structures.

[0138] Figure 7 A structure with a single circular hole is shown in the figure. The left figure shows the size and loading boundary conditions of the structure, and the right figure shows the initial mesh model. The constant stress on the upper and lower boundaries of the structure is 2.5 MPa, and the minimum mesh size is h min =5 / 32mm, the parameters used are the same as those in the previous simulation example.

[0139] Figure 8 and Fig. 9 The influence of time increment on the final dynamic failure morphology and elastic / fracture energy evolution are given respectively. Figure 8 Among them, (a) Δt = 0.2 μs, (b) Δt = 0.1 μs, (c) Δt = 0.05 μs. Fig. 9 In the figure, (a) elastic energy, (b) fracture energy.

[0140] Fig.10 and Fig.11 The minimum grid size h is given in min Impact on the final dynamic failure morphology and elastic / fracture energy evolution. Fig.10 Among them, (a)hmin=5 / 16mm, (b)hmin=5 / 32mm, (c)hmin=5 / 64mm. Fig.11 In the figure, (a) elastic energy, (b) fracture energy. Obviously, the calculation results obtained by this method converge to the mesh refinement and the reduction of time increment, which shows the stability and reliability of this method.

[0141] In order to illustrate that the present invention is more efficient than the global mesh refinement calculation method, the time required for global refinement calculation is further investigated. Table 1 shows the detailed time comparison of the corresponding calculation methods, and it can be found that the adaptive mesh refinement strategy adopted by the present invention can greatly reduce the calculation time.

[0142] Table 1 Comparison of computational time required for adaptive mesh refinement strategy and global mesh refinement strategy

[0143]

[0144] Furthermore, in order to illustrate the effectiveness of the method of the present invention in complex multi-well plates, we used Fig.12 A dynamic fracture simulation of a structure with nine randomly distributed circular holes is shown. Fig.13 The dynamic fracture and mesh adaptive refinement process are given. Fig.14 The final dynamic failure forms of six randomly distributed circular hole structures and their corresponding adaptive mesh models are given. Fig.15 The corresponding evolution of elastic energy and fracture energy is given. Obviously, the method of the present invention can effectively simulate the dynamic fracture process of complex porous plates and evaluate their fracture toughness.

[0145] The above-mentioned embodiments have proved the effectiveness of the calculation method for simulating the dynamic fracture process of porous structures and evaluating the fracture toughness proposed in the present invention.

[0146] In summary, in order to better adapt to the adaptive mesh refinement strategy and relax the requirements on the mesh size, this method extends the existing second-order phase field dynamic fracture simulation method to a fourth-order method. For this purpose, the PHT spline based on isogeometric analysis is used to construct the C1 continuous basis function; in order to improve the computational efficiency, a mesh adaptive refinement strategy is introduced into the numerical implementation scheme, and a transmission scheme including node field quantities and integration point field quantities is formulated. Most of the existing adaptive phase field fracture methods based on isogeometric analysis ignore the field quantities at the transmission integration points, which may lead to the phenomenon of crack healing in the structure during loading.

[0147] This invention can reproduce the dynamic fracture results reported in the prior art, and the results obtained are better than those obtained by the second-order method; compared with the use of fixed grids for calculations, this method can greatly improve the calculation efficiency; the calculation results of this method converge to the refinement of the grid and the reduction of the time increment step, which can effectively ensure the stability of the calculation results.

[0148] The dynamic fracture process simulation and fracture toughness assessment method for porous structures disclosed in the above embodiments can, in actual application, have its operating logic written into a set of executable instructions, which are written into a storage medium and run on the above electronic device.

[0149] More specific examples of computer-readable storage media mentioned in this embodiment may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), an erasable programmable read-only memory (EPROM or flash memory), an optical storage device, a magnetic storage device, or any suitable combination of the above. Computer-readable storage media may include a data signal propagated in a baseband or as part of a carrier wave, wherein a readable program code is carried. Such propagated data signals may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. The readable signal medium may also be any readable medium other than a readable storage medium, which may send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, device, or device.

[0150] In an exemplary embodiment, a computer program product is provided, including a computer program, which, when executed by a processor, implements the process of the dynamic fracture process simulation and fracture toughness evaluation method for porous structures disclosed in the above embodiment, which will not be described in detail here.

[0151] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.< / x>

Claims

1. A method for dynamic fracture process simulation and fracture toughness evaluation of porous structures, characterized in that: The steps include: A typical porous structure workpiece is selected as a sample; the fracture process of the sample is modeled and its one-dimensional fracture field model is constructed; Analyzing the one-dimensional fracture field model to obtain the displacement field control equation and the fracture field control equation of the porous structure workpiece; The displacement field control equation and the fracture field control equation are spatially discretized using PHT splines to obtain an initial fracture assessment model; On the basis of the initial fracture assessment model, an adaptive grid refinement strategy based on phase field variables is introduced, and a transmission scheme of each field quantity is introduced for the refined grid to obtain an optimized fracture assessment model; The digital modeling of the target porous structure workpiece to be evaluated is imported into the optimized fracture evaluation model, the fracture process simulation and fracture toughness evaluation are completed, and the evaluation result is output.

2. The method for dynamic fracture process simulation and fracture toughness evaluation of porous structures according to claim 1, characterized in that: The fracture process of the sample is modeled to construct a one-dimensional fracture field model. The expression of the one-dimensional fracture field model is as follows: In the formula, It is a size parameter that controls the normalized crack width; d = 0 means that the material is not damaged, and d = 1 means that the material is completely damaged.

3. The method for dynamic fracture process simulation and fracture toughness evaluation of porous structures according to claim 2, characterized in that: By analyzing the above one-dimensional fracture field model, the displacement field control equation and fracture field control equation of the porous structure workpiece are obtained, wherein the expression of the displacement field control equation is as follows: In the formula, σ represents the Cauchy stress; b represents the stress on the structure; ρ represents the material density; ü represents the acceleration; n represents the unit vector of the external normal of the structure; t represents the surface force on the structure; u represents the displacement; represents the displacement applied on the surface of the structure; Ω represents the structural area; Indicates the boundary where the surface force is applied; Ω u Represents the boundary to which the displacement is applied.

4. The method for dynamic fracture process simulation and fracture toughness evaluation of porous structures according to claim 3, characterized in that: The one-dimensional fracture field model is analyzed to obtain the displacement field control equation and the fracture field control equation of the porous structure workpiece, wherein the fracture field control equation is expressed as follows: In the formula, represents the elastic energy density driving crack extension; G c Indicates the critical energy release rate of the material; On the basis of the fracture field control equation, a historical variable function is introduced To avoid crack healing; The historical variable function expression is as follows: Where ε represents strain and t is the total time of dynamic loading.

5. The method for dynamic fracture process simulation and fracture toughness evaluation of porous structures according to claim 1, characterized in that: In the parameter space (ξ,η,ζ), the geometric representation of the PHT spline is as follows: In the formula, is the coordinate of the control point, s is the total number of control points, R i It is the basis function for constructing the shape functions used subsequently, and its form is as follows: In the formula, w i is the weight of the ith control point, N i Define basis functions for B-splines on a level T grid.

6. The method for dynamic fracture process simulation and fracture toughness evaluation of porous structures according to claim 5, characterized in that: The displacement field control equation and the fracture field control equation are spatially discretized using PHT splines to obtain the initial fracture assessment model: In the formula, Mü+K u u=F u is the spatial discretization form of the displacement field control equation; K d d=F d is the spatial discretization form of the fracture field control equation; M represents the overall stiffness matrix of inertia force; K u represents the displacement global stiffness matrix; F u Represents the overall stiffness matrix of external forces; K d represents the overall stiffness matrix of the fracture field; d represents the fracture field; F d Represents the cracking driving force and the global stiffness matrix.

7. The method for dynamic fracture process simulation and fracture toughness evaluation of porous structures according to claim 1, characterized in that: Based on the initial fracture assessment model, an adaptive mesh refinement strategy based on phase field variables is introduced, which includes: The structure with holes or gaps initially is realized by refining the mesh at the boundary of the two-phase materials, where the material corresponding to the mesh at the hole or gap is set as the hole material, and the mesh at other parts is identified as a solid and set according to its specific material properties; After the numerical simulation begins, when cracks initiate or propagate, only those locations where the fracture field value is greater than the predetermined threshold will be marked and refined to the highest level of the grid.

8. The method for dynamic fracture process simulation and fracture toughness evaluation of porous structures according to claim 7, characterized in that: The transmission scheme of each field quantity is introduced for the refined grid, including: The data on the grid nodes are transmitted using shape function projection; The data transmission at the integration point adopts the method of shape function projection or directly inherits the value of the nearest integration point of the coarse grid.

9. An electronic device, characterized in that: The device comprises: a processor and a memory storing computer program instructions; when the processor executes the computer program instructions, the method for dynamic fracture process simulation and fracture toughness evaluation for porous structures as described in any one of claims 1 to 8 is implemented.

10. A computer-readable storage medium, characterized in that: The storage medium stores at least one executable instruction. When the executable instruction is executed on an electronic device, the electronic device executes the method for dynamic fracture process simulation and fracture toughness evaluation for porous structures as described in any one of claims 1 to 8.

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