Hole extrusion strength prediction method and system for ceramic matrix composite parts

Abstract

The present invention belongs to the field of composite material mechanics technology and provides a method and system for predicting the hole extrusion strength of ceramic-matrix composite parts. The method comprises: meshing a finite element geometric model of the ceramic-matrix composite part to be tested; obtaining the stress field of each mesh element through finite element simulation; based on the stress field, using the three-dimensional Hashin criterion or the MMF3 criterion to determine the type of mesh element damage and perform stiffness degradation to obtain a stiffness matrix; using the stiffness matrix and the applied displacement load to obtain the current force load, and then obtaining the hole extrusion strength based on the current force load and the hole contact area. The method of the present invention can accurately predict the hole extrusion strength of a part, laying the foundation for mechanical connection performance analysis of composite materials and high-fidelity simulation calculations of composite structures.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material mechanics, and relates to a method and system for predicting the hole extrusion strength of a ceramic-based composite material part. Background Art

[0002] Ceramic matrix composite connectors significantly impact the overall performance of composite structures. For example, aircraft structures utilize various joining methods, such as mechanical joining and brazing, to integrate numerous complex and complex parts into a single structure. Among these various joining methods, mechanical joining is widely favored by designers due to its robust stability, reliability, and flexible disassembly.

[0003] Mechanical connections require drilling holes in the connectors, then connecting them to the components with holes using bolts or rivets to form a new load-bearing structure. Because composite materials are complex, anisotropic materials, weak spots are often found near the edges of the holes. The stress distribution and damage patterns around these holes are much more complex than those in traditional metal structures, resulting in different mechanical behaviors when subjected to tensile and compressive loads.

[0004] Therefore, it is of great significance to the safety and stability of composite materials structures to deeply analyze their mechanical connections to determine their force forms and stress distribution, and to reasonably and effectively establish a tensile and compressive damage model for composite mechanical connections. Summary of the Invention

[0005] In order to analyze the hole edges of composite materials connected by mechanical connection and improve the safety and stability of the connected composite materials, the present invention discloses a method for predicting the hole extrusion strength of ceramic matrix composite parts, which includes the following steps:

[0006] S1. Meshing the finite element geometric model of the ceramic matrix composite part to be tested;

[0007] S2. Applying elastic modulus to each grid cell for nonlinear analysis through finite element simulation method to obtain the stress field of each grid cell;

[0008] S3. Based on the stress field, use the three-dimensional Hashin criterion or the MMF3 (modified micromechanics failure criterion) criterion to determine the damage type of the mesh unit, and perform stiffness degradation on each mesh unit according to the damage type to obtain a stiffness matrix;

[0009] S4. Using the stiffness matrix and the loaded displacement load, obtain the current force load according to the force load peak value calculated in the previous iteration, and obtain the hole extrusion strength according to the current force load and the hole contact area.

[0010] Furthermore, in the above step S2, a finite element simulation method is used to apply an elastic modulus to each grid unit for nonlinear analysis to obtain the stress field of each grid unit, including:

[0011] S21. Using the finite element method, assign a tensile elastic modulus to each direction of each grid unit to perform linear static analysis and obtain the material principal direction stress of each grid unit;

[0012] S22. Assign a tensile elastic modulus to each direction of all the grid units whose main direction stress of the material is positive, and assign a compressive elastic modulus to each direction of all the grid units whose main direction stress of the material is negative, to obtain the stress field of each grid unit.

[0013] Furthermore, in the above step S3, based on the stress field, a three-dimensional Hashin criterion or an MMF3 criterion is used to determine mesh unit damage, and stiffness degradation is performed on the mesh unit determined to be damaged to calculate the stiffness matrix, including:

[0014] S31, calculating the sum of the normal stresses of the stress field of each grid unit, and taking the sum of the normal stresses as the stress invariant;

[0015] S32, judging the positive or negative value of the stress invariant of each mesh unit; if the value is positive, determining the damage type of the mesh unit using the three-dimensional Hashin criterion according to the stress field; if the value is negative, determining the damage type of the mesh unit using the MMF3 criterion according to the stress field;

[0016] S33. Calculate the stiffness matrix of each mesh unit according to the damage type using the stiffness reduction coefficient matrix and the initial material stiffness matrix.

[0017] Furthermore, in the above step S32, the damage type of the grid unit is determined according to the stress field using a three-dimensional Hashin criterion, including:

[0018] when When , the damage type is fiber stretching;

[0019] when When , the damage type is fiber compression;

[0020] when When , the damage type is matrix stretching;

[0021] when When , the damage type is matrix compression;

[0022] when When , the damage type is fiber-matrix shear;

[0023] when When , the damage type is tensile delamination;

[0024] when When , the damage type is compression delamination;

[0025] Among them, the defined fiber direction is represented by 1, the in-plane direction perpendicular to the fiber direction is represented by 2, and the out-of-plane direction perpendicular to the fiber direction is represented by 3; is the normal stress in direction 1, is the normal stress in two directions, is the normal stress in three directions, is the shear stress in directions 1 and 2, is the shear stress in the 2nd and 3rd directions, is the shear stress in directions 1 and 3, is the tensile strength in 1 direction; is the shear strength in directions 1 and 2; is the compressive strength in one direction.

[0026] Furthermore, in the above step S32, judging the damage type of the grid unit using the MMF3 criterion according to the stress field includes:

[0027] when When , the damage type is judged to be fiber tensile failure;

[0028] when When , the damage type is judged to be fiber compression failure;

[0029] when When , the damage type is judged to be matrix failure;

[0030] in, T f is the fiber tensile strength, C f is the fiber compressive strength, T m is the matrix tensile strength, C m is the matrix compressive strength, S m is the matrix shear strength, k m is the matrix stress distribution coefficient, k f is the fiber stress distribution coefficient; the fiber direction is defined as 1, the in-plane direction perpendicular to the fiber direction is defined as 2, and the out-of-plane direction perpendicular to the fiber direction is defined as 3; is the normal stress in direction 1, is the normal stress in two directions, is the normal stress in three directions, is the in-plane shear stress in directions 1 and 2, is the interlaminar shear stress in the 1-direction and the 3-direction.

[0031] Preferably, the matrix stress distribution coefficient and the fiber stress distribution coefficient are expressed by the formula Calculated, where E m is the matrix elastic modulus, E f is the fiber elastic modulus, V m is the volume ratio of the matrix in the part, V f is the fiber volume fraction in the part.

[0032] Furthermore, in the above step S4, the stiffness matrix and the applied displacement load are used to obtain the current force load according to the force load peak value calculated in the previous iteration, and the hole extrusion strength is obtained according to the current force load and the hole contact area, including:

[0033] S41, calculating the current force load by multiplying the stiffness matrix and the displacement load;

[0034] S42, comparing the current force load with the force load peak value calculated in the previous iteration, and if the current force load is less than a set multiple of the force load peak value, stopping the iteration to obtain the maximum force load in the current iteration calculation;

[0035] S43. Calculate the ratio of the maximum force load to the hole contact area to obtain the hole extrusion strength.

[0036] An embodiment of the present invention also provides a hole extrusion strength prediction system for ceramic matrix composite parts, including a finite element model building module, a stress field calculation module, a damage type judgment module, a stiffness degradation module and a hole extrusion strength calculation module.

[0037] Wherein, the finite element model building module is used to perform meshing on the finite element geometric model of the part to be tested of the ceramic matrix composite material;

[0038] The stress field calculation module is used to apply elastic modulus to each grid unit to perform nonlinear analysis through finite element simulation method to obtain the stress field of each grid unit;

[0039] The damage type judgment module is used to judge the damage type of the grid unit according to the stress field using the three-dimensional Hashin criterion or the MMF3 criterion;

[0040] The stiffness degradation module is used to perform stiffness degradation on each of the grid elements according to the damage type to obtain a stiffness matrix;

[0041] The hole extrusion strength calculation module is used to use the stiffness matrix and the loaded displacement load to obtain the current force load according to the force load peak value calculated in the previous iteration, and obtain the hole extrusion strength according to the current force load and the hole contact area.

[0042] Compared with the prior art, the beneficial effects achieved by at least one of the above-mentioned technical solutions adopted in the embodiments of this specification include at least the following: the method of the present invention can accurately obtain and characterize the pore extrusion strength of ceramic-based composite materials. This method fully considers the different mechanical characteristics and constitutive features of ceramic-based composite materials in tension and compression based on progressive damage. Based on the use of different elastic moduli for tension and compression, the composite material pore extrusion mechanical model units are divided into two categories for damage determination. That is, for tension units, the three-dimensional Hashin criterion is used for damage determination; for compression units, the MMF3 theory is used for damage determination. The present invention can relatively accurately obtain constitutive curves that characterize composite materials, laying the foundation for performance analysis of composite materials and high-fidelity simulation calculations of composite material structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0044] Figure 1 This is a flow chart of a method for predicting hole extrusion strength of a ceramic matrix composite part disclosed in an embodiment of the present invention;

[0045] Figure 2 This is a diagram illustrating the framework for predicting the hole extrusion strength of a ceramic matrix composite part disclosed in an embodiment of the present invention;

[0046] Among them, 201, finite element model establishment module; 202, stress field calculation module; 203, damage type judgment module; 204, stiffness degradation module; 205, hole extrusion strength calculation module. DETAILED DESCRIPTION

[0047] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0048] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the features of the following embodiments and embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of this application.

[0049] The embodiment of the present invention discloses a method for predicting the hole extrusion strength of a ceramic matrix composite material part. Figure 1 As shown, the method includes the following steps:

[0050] S1. Meshing the finite element geometric model of the ceramic matrix composite part to be tested;

[0051] S2. Applying elastic modulus to each grid cell for nonlinear analysis through finite element simulation method to obtain the stress field of each grid cell;

[0052] S3. Based on the stress field, use the three-dimensional Hashin criterion or the MMF3 criterion to determine the damage type of the mesh unit, and perform stiffness degradation on each mesh unit according to the damage type to obtain a stiffness matrix;

[0053] S4. Using the stiffness matrix and the loaded displacement load, obtain the current force load according to the force load peak value calculated in the previous iteration, and obtain the hole extrusion strength according to the current force load and the hole contact area.

[0054] Furthermore, when implementing the above step S1, commercial pre-processing software can be used to mesh the finite element geometric model of the ceramic matrix composite part. When meshing, the hole edge is mapped and divided with the hole center as the center to improve the accuracy of the calculation results. Generally speaking, the mesh size of the hole edge should not be larger than 1 / 16 of the hole circumference, and positions without holes can be freely divided.

[0055] For example, for a 3D single-bolt composite connection structure finite element model, where the ply layup sequence is [45 / 0 / -45 / 90] 2sThe total thickness of the laminate is 3.2 mm, with consistent thickness and material properties across all layers. General finite element software was used to assign plies to the laminate and mesh the model using the corresponding modules within the software. Because fully integrated elements are prone to shear self-locking, reduced integration was used to improve model reliability, reduce computational errors, and save time and effort.

[0056] Furthermore, after the finite element model is established in step S1, stress calculation is performed. When calculating stress, a static load is first used to assign a tensile elastic modulus to all grid cells (including tensile elastic moduli applied in the fiber direction and along the perpendicular direction of the laminate), and a preliminary analysis is performed to obtain the initial stress field. Subsequently, the stress in the main direction of the material is extracted for each grid cell based on the initial stress field. If the stress is positive, a tensile elastic modulus is assigned in that direction. If the stress is negative, a compressive elastic modulus is assigned in that direction to reorganize the stiffness matrix and obtain the stress field in the initial state. Specifically, in the above step S2, an elastic modulus is applied to each grid cell through a finite element simulation method to perform a nonlinear analysis to obtain the stress field of each grid cell, including the following steps:

[0057] S21. Using the finite element method, assign a tensile elastic modulus to each direction of each grid unit to perform linear static analysis and obtain the material principal direction stress of each grid unit;

[0058] S22. Assigning a tensile elastic modulus to all mesh cells in each direction where the material stress is positive in the principal direction, and assigning a compressive elastic modulus to all mesh cells in each direction where the material stress is negative in the principal direction, thereby obtaining a stress field for each mesh cell. In this step, the assigned compressive elastic modulus and tensile elastic modulus have different values.

[0059] Furthermore, in the above step S3, based on the stress field, a three-dimensional Hashin criterion or an MMF3 criterion is used to determine mesh unit damage, and stiffness degradation is performed on the mesh unit determined to be damaged to calculate the stiffness matrix, including:

[0060] S31, calculating the sum of the normal stresses of the stress field of each grid unit, and taking the sum of the normal stresses as the stress invariant;

[0061] S32, judging the positive or negative value of the stress invariant of each mesh unit; if the value is positive, determining the damage type of the mesh unit using the three-dimensional Hashin criterion according to the stress field; if the value is negative, determining the damage type of the mesh unit using the MMF3 criterion according to the stress field;

[0062] S33. Calculate the stiffness matrix of each mesh unit according to the damage type using the stiffness reduction coefficient matrix and the initial material stiffness matrix.

[0063] Furthermore, in the above step S32, the damage type of the grid unit is determined according to the stress field using a three-dimensional Hashin criterion, including:

[0064] (1) When When , the damage type is fiber stretching;

[0065] (2) When When , the damage type is fiber compression;

[0066] (3) When When , the damage type is matrix stretching;

[0067] (4) When When , the damage type is matrix compression;

[0068] (5) When When , the damage type is fiber-matrix shear;

[0069] (6) When When , the damage type is tensile delamination;

[0070] (7) When When , the damage type is compression delamination;

[0071] Among them, the defined fiber direction is represented by 1, the in-plane direction perpendicular to the fiber direction is represented by 2, and the out-of-plane direction perpendicular to the fiber direction is represented by 3; is the normal stress in direction 1, is the normal stress in two directions, is the normal stress in three directions, is the shear stress in directions 1 and 2, is the shear stress in the 2nd and 3rd directions, is the shear stress in directions 1 and 3, is the tensile strength in 1 direction; is the shear strength in directions 1 and 2; is the compressive strength in one direction.

[0072] Furthermore, a cross-scale failure criterion based on the MMF3 criterion is used to simulate damage to composite materials under compressive loads. This can analyze the stress state of the fiber and matrix at a microscopic level and define the failure behavior of the fiber and matrix respectively, thereby truly reflecting the material properties of the fiber and matrix. Specifically, in step S32, the damage type of the grid cell is determined based on the stress field using the MMF3 criterion, including:

[0073] (1) When When , the damage type is judged to be fiber tensile failure;

[0074] (2) When When , the damage type is judged to be fiber compression failure;

[0075] (3) When When , the damage type is judged to be matrix failure;

[0076] Where, is the macroscopic stress of a single-layer plate, and five microscopic strength parameters are specified for the fiber and matrix, namely .in, T f is the fiber tensile strength, C f is the fiber compressive strength, T m is the matrix tensile strength, C m is the matrix compressive strength, S m is the matrix shear strength. The above strength parameters are all material properties and can be obtained from the material manual. k m is the matrix stress distribution coefficient, k f is the fiber stress distribution coefficient; the fiber direction is defined as 1, the in-plane direction perpendicular to the fiber direction is defined as 2, and the out-of-plane direction perpendicular to the fiber direction is defined as 3; is the normal stress in direction 1, is the normal stress in two directions, is the normal stress in three directions, is the in-plane shear stress in directions 1 and 2, is the interlaminar shear stress in the 1-direction and the 3-direction.

[0077] Furthermore, the matrix stress distribution coefficient and the fiber stress distribution coefficient are expressed by the formula Calculated, where E m is the matrix elastic modulus, E f is the fiber elastic modulus, V m is the volume ratio of the matrix in the part, V f is the fiber volume fraction in the part.

[0078] When damage is detected and the damage type is determined in step S32, the stiffness reduction coefficient matrix is used in step S33. M This method also introduces the damage variable matrix in damage mechanics. D The concept of instantaneous degradation model is as follows:

[0079] ;

[0080] In the above formula, failure occurs and affects the material. At this time, the stiffness matrix is expressed as E * express, E represents the initial material stiffness matrix, M is the stiffness reduction coefficient matrix, 0≤ M ≤1. In the gradual degradation model, the material stiffness will change as the stress and strain increase, that is, the material stiffness parameters degrade in the form of a linear or nonlinear function.

[0081] Furthermore, in the above step S4, the stiffness matrix and the applied displacement load are used to obtain the current force load according to the force load peak value calculated in the previous iteration, and the hole extrusion strength is obtained according to the current force load and the hole contact area, including:

[0082] S41, calculating the current force load by multiplying the stiffness matrix and the displacement load;

[0083] S42: Compare the current force load with the force load peak value calculated in the previous iteration. If the current force load is less than a set multiple of the force load peak value, stop the iteration to obtain the maximum force load in the current iteration. In this embodiment, the calculation is stopped when the current force load drops to 40% of the force load peak value.

[0084] S43. Calculate the ratio of the maximum force load to the hole contact area to obtain the hole extrusion strength.

[0085] The method of the present invention accurately characterizes the pore extrusion strength of ceramic-matrix composites. Based on progressive damage, the method fully considers the different mechanical constitutive characteristics of ceramic-matrix composites in tension and compression. Using different elastic moduli for tension and compression, the composite pore extrusion mechanical model elements are divided into two categories for damage determination: for tension elements, the three-dimensional Hashin criterion is used for damage determination; for compression elements, the MMF3 theory is used for damage determination. This method can relatively accurately obtain constitutive curves characterizing composite materials, laying the foundation for composite material performance analysis and high-fidelity simulation calculations of composite material structures.

[0086] Based on the same inventive concept, an embodiment of the present invention further provides a hole extrusion strength prediction system for ceramic-based composite parts, as described in the following embodiments. Since the principle of solving the problem by the hole extrusion strength prediction system for ceramic-based composite parts is similar to the hole extrusion strength prediction method for ceramic-based composite parts disclosed in the above embodiments, the implementation of the hole extrusion strength prediction system for ceramic-based composite parts can refer to the implementation of the hole extrusion strength prediction method for ceramic-based composite parts, and the repeated parts will not be repeated. As used below, the term "unit" or "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, implementation in hardware, or a combination of software and hardware, is also possible and conceivable.

[0087] Figure 2 This is a structural block diagram of a hole extrusion strength prediction system for ceramic matrix composite parts disclosed in an embodiment of the present invention, such as Figure 2 As shown, the system includes a finite element model building module 201, a stress field calculation module 202, a damage type judgment module 203, a stiffness degradation module 204 and a hole extrusion strength calculation module 205. The structure is described below.

[0088] Wherein, the finite element model building module 201 is used to perform meshing on the finite element geometric model of the part to be tested of the ceramic matrix composite material;

[0089] The stress field calculation module 202 is used to apply elastic modulus to each grid unit to perform nonlinear analysis through finite element simulation method to obtain the stress field of each grid unit;

[0090] The damage type judgment module 203 is used to judge the damage type of the grid unit according to the stress field using the three-dimensional Hashin criterion or the MMF3 criterion;

[0091] The stiffness degradation module 204 is used to perform stiffness degradation on each of the grid elements according to the damage type to obtain a stiffness matrix;

[0092] The hole extrusion strength calculation module 205 is used to use the stiffness matrix and the loaded displacement load to obtain the current force load according to the force load peak value calculated in the previous iteration, and obtain the hole extrusion strength according to the current force load and the hole contact area.

[0093] In this embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, any of the above-mentioned methods for predicting the hole extrusion strength of ceramic-based composite parts is implemented.

[0094] Specifically, the computer device may be a computer terminal, a server or a similar computing device.

[0095] In this embodiment, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program for executing any of the above-mentioned methods for predicting the hole extrusion strength of a ceramic matrix composite material part.

[0096] Specifically, computer-readable storage media include permanent and non-permanent, removable and non-removable media that can be used to store information by any method or technology. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer-readable storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable storage media does not include transitory media such as modulated data signals and carrier waves.

[0097] Obviously, those skilled in the art should understand that the various modules or steps of the above-mentioned embodiments of the present invention can be implemented using a general-purpose computing device, they can be concentrated on a single computing device, or distributed across a network composed of multiple computing devices. Alternatively, they can be implemented using program code executable by the computing device, so that they can be stored in a storage device and executed by the computing device. In some cases, the steps shown or described can be performed in a different order than herein, or they can be made into separate integrated circuit modules, or multiple modules or steps can be made into a single integrated circuit module for implementation. Thus, the embodiments of the present invention are not limited to any specific combination of hardware and software.

[0098] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for predicting the hole extrusion strength of a ceramic matrix composite part, characterized in that: include: Meshing the finite element geometric model of the ceramic matrix composite part to be tested; By applying the elastic modulus to each grid element for nonlinear analysis through the finite element simulation method, the stress field of each grid element is obtained; According to the stress field, a three-dimensional Hashin criterion or an MMF3 criterion is used to determine the damage type of the grid unit, and stiffness degradation is performed on each of the grid units according to the damage type to obtain a stiffness matrix, including: calculating the positive stress sum of the stress field of each grid unit, and using the positive stress sum as a stress invariant; judging the positive and negative values of the stress invariant of each grid unit, if it is positive, determining the damage type of the grid unit according to the stress field using the three-dimensional Hashin criterion; if it is negative, determining the damage type of the grid unit according to the stress field using the MMF3 criterion; and calculating the stiffness matrix of each grid unit according to the damage type using a stiffness reduction factor matrix and an initial material stiffness matrix; Wherein, judging the damage type of the grid unit by using the MMF3 criterion according to the stress field includes: when When , the damage type is judged to be fiber tensile failure; when When , the damage type is judged to be fiber compression failure; when When , the damage type is judged to be matrix failure; T f is the fiber tensile strength, C f is the fiber compressive strength, T m is the matrix tensile strength, C m is the matrix compressive strength, S m is the matrix shear strength, k m is the matrix stress distribution coefficient, k f is the fiber stress distribution coefficient; the fiber direction is defined as 1, the in-plane direction perpendicular to the fiber direction is defined as 2, and the out-of-plane direction perpendicular to the fiber direction is defined as 3. is the normal stress in direction 1, is the normal stress in two directions, is the normal stress in three directions, is the in-plane shear stress in directions 1 and 2, is the interlaminar shear stress in directions 1 and 3; The stiffness matrix and the applied displacement load are used to obtain the current force load according to the force load peak value obtained by the previous iterative calculation, and the hole extrusion strength is obtained according to the current force load and the hole contact area.

2. The method for predicting the hole extrusion strength of a ceramic matrix composite part according to claim 1, characterized in that: Finite element simulation methods are used to apply elastic modulus to each grid cell for nonlinear analysis to obtain the stress field of each grid cell, including: By using the finite element method, a tensile elastic modulus is assigned to each direction of each grid unit for linear static analysis to obtain the material principal direction stress of each grid unit; The tensile elastic modulus is assigned to each direction of all the grid units whose main direction stress of the material is positive, and the compressive elastic modulus is assigned to each direction of all the grid units whose main direction stress of the material is negative, so as to obtain the stress field of each grid unit.

3. The method for predicting hole extrusion strength of ceramic matrix composite parts according to claim 1, characterized in that: The damage type of the grid unit is determined based on the stress field using a three-dimensional Hashin criterion, including: when When , the damage type is fiber stretching; when When , the damage type is fiber compression; when When , the damage type is matrix stretching; when When , the damage type is matrix compression; when When , the damage type is fiber-matrix shear; when When , the damage type is tensile delamination; when When , the damage type is compression delamination; Among them, the defined fiber direction is represented by 1, the in-plane direction perpendicular to the fiber direction is represented by 2, and the out-of-plane direction perpendicular to the fiber direction is represented by 3; is the normal stress in direction 1, is the normal stress in two directions, is the normal stress in three directions, is the shear stress in directions 1 and 2, is the shear stress in the 2nd and 3rd directions, is the shear stress in directions 1 and 3, is the tensile strength in 1 direction; is the shear strength in directions 1 and 2; is the compressive strength in one direction.

4. The method for predicting hole extrusion strength of ceramic matrix composite parts according to claim 1, characterized in that: The matrix stress distribution coefficient and fiber stress distribution coefficient are expressed by the formula Calculated, where E m is the matrix elastic modulus, E f is the fiber elastic modulus, V m is the volume ratio of the matrix in the part, V f is the fiber volume fraction in the part.

5. The method for predicting hole extrusion strength of ceramic matrix composite parts according to claim 1, characterized in that: The stiffness matrix and the applied displacement load are used to obtain the current force load according to the force load peak value calculated in the previous iteration, and the hole extrusion strength is obtained according to the current force load and the hole contact area, including: The current force load is calculated by multiplying the stiffness matrix and the displacement load; Compare the current force load with the force load peak value calculated in the previous iteration. If the current force load is less than a set multiple of the force load peak value, stop the iteration and obtain the maximum force load in the current iteration calculation. The ratio of the maximum force load to the hole contact area is calculated to obtain the hole extrusion strength.

6. A hole extrusion strength prediction system for ceramic matrix composite parts, characterized in that: include: A finite element model building module, wherein the finite element model building module is used to perform meshing on a finite element geometric model of a part to be tested made of a ceramic matrix composite material; A stress field calculation module, wherein the stress field calculation module is used to apply an elastic modulus to each grid unit to perform nonlinear analysis through a finite element simulation method to obtain a stress field of each grid unit; A damage type judgment module is configured to judge the damage type of a mesh unit based on the stress field using a three-dimensional Hashin criterion or an MMF3 criterion, including: calculating the sum of the normal stresses of the stress field of each mesh unit and using the sum of the normal stresses as a stress invariant; judging the positive or negative value of the stress invariant of each mesh unit; if the value is positive, judging the damage type of the mesh unit based on the stress field using a three-dimensional Hashin criterion; if the value is negative, judging the damage type of the mesh unit based on the stress field using an MMF3 criterion; and calculating the stiffness matrix of each mesh unit based on the damage type using a stiffness reduction factor matrix and an initial material stiffness matrix; wherein judging the damage type of the mesh unit based on the stress field using the MMF3 criterion includes: when When , the damage type is judged to be fiber tensile failure; when When , the damage type is judged to be fiber compression failure; when When , the damage type is judged to be matrix failure; T f is the fiber tensile strength, C f is the fiber compressive strength, T m is the matrix tensile strength, C m is the matrix compressive strength, S m is the matrix shear strength, k m is the matrix stress distribution coefficient, k f is the fiber stress distribution coefficient; the fiber direction is defined as 1, the in-plane direction perpendicular to the fiber direction is defined as 2, and the out-of-plane direction perpendicular to the fiber direction is defined as 3. is the normal stress in direction 1, is the normal stress in two directions, is the normal stress in three directions, is the in-plane shear stress in directions 1 and 2, is the interlaminar shear stress in directions 1 and 3; A stiffness degradation module, configured to perform stiffness degradation on each of the grid elements according to the damage type to obtain a stiffness matrix; The hole extrusion strength calculation module is used to use the stiffness matrix and the loaded displacement load to obtain the current force load based on the force load peak value calculated in the previous iteration, and obtain the hole extrusion strength based on the current force load and the hole contact area.

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