Calculation method and system for creep damage and creep life of ceramic matrix composites

Abstract

The present invention belongs to the field of aeroengines and relates to composite material numerical simulation and life prediction technology. It provides a method and system for calculating creep damage and creep life of ceramic-based composite materials. The method comprises: obtaining the material failure strain of a simulated test piece and multiple time-strain curves at multiple load levels at each creep temperature; solving the creep damage evolution parameters of the composite material using a probabilistic t-distribution method and a fitting method based on all time-strain curves at each creep temperature to obtain a creep rate formula; and obtaining the creep damage and creep life of the test piece based on the creep rate formula and the material failure strain using a finite element simulation method. The method of the present invention takes into account the dispersion of material parameters, quickly and reasonably predicts the creep damage and creep life of the composite material, provides support for the forward design of ceramic-based composite structures, and improves the iteration speed and R&D efficiency of ceramic-based composite structures.

Description

Technical Field

[0001] The present invention belongs to the field of aero-engines and relates to composite material numerical simulation and life prediction technology, and specifically to a method and system for calculating creep damage and creep life of ceramic-based composite materials. Background Art

[0002] With the development of aero-engine technology and the improvement of its performance, in addition to improvements and optimization of structures and cooling solutions, higher requirements are being placed on aero-engine materials. Ceramic matrix composites (CMCs), due to their lightweight, high-temperature resistance, and high strength, are widely used in aero-engine hot-end components such as combustion chambers, turbines, and tail nozzles. The use of CMCs can significantly reduce the weight of the structure itself, thereby reducing the mass of the hot-end stator, blisk, and transmission system. It can also further increase the temperature before the turbine, which is of great significance to improving engine efficiency.

[0003] During the use of CMCs in hot-end components, they are subjected to long-term high temperatures and high stresses, which can cause creep. This can have two effects: (1) deformation due to creep can cause contact or even compression with other components; (2) long-term creep can degrade material performance or even cause failure. Therefore, it is necessary to study the creep damage and lifespan of CMCs to provide a basis for their future practical application.

[0004] Continuous fiber reinforced CMCs components are difficult to be treated with traditional creep models. For this type of material, there are several models based on the classical law of mixtures, shear lag analysis models and damage mechanics models. If you want to make the established model effective, you need to consider the following two main factors: first, you should consider the redistribution of stress between the fiber and the matrix as it changes with time when creep occurs, and second, you should be able to describe the damage accumulation process. For example, Ju Xiaorong et al. established a model suitable for SiC f / SiC small composite material high temperature creep micromechanical model, the model includes fiber creep model, matrix creep model, matrix cracking model, interface debonding model, fiber fracture model, the above models are combined with the shear lag model to finally realize SiC f Output of creep strain-time curve of C / SiC composite material. Combining statistical analysis with creep damage mechanism, based on the high temperature creep experiment of C / SiC, displacement was used as the main control variable to study the creep fracture displacement law and establish a C / SiC creep life estimation model considering the random characteristics of the material. For another example, Zhang Weihua et al. established 2DC / (SiC-BC x )2 Composite material residual strength prediction model, combined with CVD-BC x The oxidation kinetics of SiC-BC and the volatilization rate of B2O3 were used to predict the creep process of 2DC / (SiC-BC in a static water-oxygen coupling environment based on the solid-phase diffusion mass transfer mechanism.x )2 residual strength variation law, based on the gas convection mass transfer mechanism, predicted the creep process of 2DC / (SiC-BC x The variation pattern of the residual strength of )2 is consistent with that of the test results.

[0005] However, most of the commonly used creep methods currently target unidirectional composite materials where the fibers are arranged in the same direction, or only achieve material-level predictions based on unit cells. The methods used are mostly based on the shear lag model, fracture mechanics interface debonding criterion and fiber failure model to obtain the fiber axial stress distribution equation under creep load. However, these methods are difficult to meet the actual strength design requirements for complex structures in engineering due to the excessive number of microscopic parameters and the large amount of calculation.

[0006] Therefore, it is necessary to provide a simple, effective and highly applicable method to solve the current problems of difficult and complex calculations in composite material structure modeling and the lack of forward design. Summary of the Invention

[0007] In response to the shortcomings of the existing technology, the present invention discloses a method for calculating the creep damage and creep life of ceramic matrix composite materials. This method takes into account the dispersion of the material parameters of the composite materials and can quickly and reasonably predict the creep deformation, creep damage and creep life of the ceramic matrix composite materials. This provides support for the forward design and engineering application of ceramic matrix composite structures and improves the iteration speed and R&D efficiency of ceramic matrix composite structures. Specifically, the method includes the following steps:

[0008] S1. Conduct creep tests on simulated test pieces to obtain material failure strain and multiple time-strain curves at multiple load levels at each creep temperature;

[0009] S2. Based on all the time-strain curves at each creep temperature, solving the creep damage evolution parameters of the composite material by a probabilistic t-distribution method and a fitting method to obtain a creep rate formula;

[0010] S3. Using a finite element simulation method, the creep damage and creep life of the ceramic matrix composite material under test are obtained according to the creep rate formula and the material failure strain.

[0011] Furthermore, in step S1, a creep test is performed on the simulated test piece to obtain the material failure strain and multiple time-strain curves at multiple load levels at each creep temperature, including:

[0012] S11. Performing a tensile test on the simulated test piece at a given creep temperature to obtain a tensile curve, and obtaining the material tensile ratio limit and the material failure strain from the tensile curve;

[0013] S12. Obtain the stresses corresponding to the 80% material tensile ratio limit, the 100% material tensile ratio limit, and the 120% material tensile ratio limit, respectively, load each of the stresses at each creep temperature, and perform an in-plane tensile creep test to obtain a time-strain curve.

[0014] Furthermore, in step S2, based on all the time-strain curves at each creep temperature, the creep damage evolution parameters of the composite material are solved by the probabilistic t distribution method and the fitting method to obtain the creep rate formula, including:

[0015] S21, extracting mechanical property parameters of the composite material from each time-strain curve at each creep temperature, wherein the mechanical property parameters of the composite material include initial modulus and maximum fracture strain;

[0016] S22. According to the probabilistic t-distribution method, the homogeneity of the mechanical property parameters of the composite material at each creep temperature is determined, and the time-strain curves corresponding to the mechanical property parameters of the composite material determined to be non-homogeneous are eliminated;

[0017] S23. Using the stress, creep temperature, and time-strain of all the remaining time-strain curves after elimination, fitting and solving are performed to obtain creep damage evolution parameters of the composite material and obtain a creep rate formula.

[0018] Furthermore, in step S22, the homogeneity of the mechanical property parameters of the composite material at each creep temperature is judged according to the probabilistic t-distribution method, including:

[0019] S221. When performing homogeneity judgment on the composite material mechanical property parameters at each creep temperature in each round, select the maximum or minimum composite material mechanical property parameter in that round as the judgment data, and calculate the remaining average values ​​and standard deviations of all the remaining composite material mechanical property parameters;

[0020] S222. Calculate a distribution coefficient using the determined data, the remaining average values, and the remaining standard deviations. When the distribution coefficient is greater than the t distribution coefficient, determine that the determined data is non-homogeneous and eliminate it.

[0021] Furthermore, in step S222, when performing homogeneity judgment, the initial modulus is first judged, and then the maximum fracture strain is judged, until the final time-strain curve at each creep temperature is obtained.

[0022] Furthermore, the creep rate formula is , where σ is stress, t is creep time, and T is creep temperature; ε c is the strain, and C1~C7 are the creep damage evolution parameters of the composite material.

[0023] Furthermore, in step S3, the creep damage and creep life of the ceramic matrix composite material under test are obtained according to the creep rate formula and the material failure strain by a finite element simulation method, including:

[0024] S31, performing finite element meshing on the ceramic matrix composite material to be tested, and extracting the fiber direction of each mesh unit;

[0025] S32, applying a test stress and a test temperature field to the ceramic matrix composite material under test by a simulation method, obtaining a simulated stress field and a simulated structural displacement field under the current stress, and extracting the current simulated stress of each grid unit along the fiber direction;

[0026] S33, calculating the current simulation strain using the creep rate formula according to the current simulation stress;

[0027] S34, calculating a current equivalent modulus of each of the mesh cells using the simulated stress and the simulated strain, and calculating a current creep damage of each of the mesh cells based on the current equivalent modulus and a previous equivalent modulus of the mesh cell under a previous stress;

[0028] S35. Determine the damage of the ceramic matrix composite material under test according to the material damage strain and the simulated structural displacement field using a damage criterion, and obtain the time corresponding to when the structure is judged to be damaged as the creep life.

[0029] Furthermore, in step S35, the failure criterion is used to determine the failure of the ceramic matrix composite material under test according to the material failure strain and the simulated structural displacement field, including:

[0030] S351, judging that the mesh unit is destroyed when the current simulation strain of the mesh unit is greater than the material failure strain according to the unit failure criterion in the failure criterion;

[0031] S352. Obtain a maximum displacement from the simulated structural displacement field using a structural destruction criterion in the destruction criterion. When the maximum displacement increment in a current unit time is greater than a given multiple of the maximum displacement increment in a previous unit time, it is determined that the tested ceramic matrix composite material structure is destroyed.

[0032] An embodiment of the present invention further provides a system for calculating creep damage and creep life of ceramic matrix composite materials, comprising a time-strain curve acquisition module, a parameter calculation module, and a creep damage and creep life calculation module.

[0033] The time-strain curve acquisition module is used to carry out creep tests on the simulated test piece to obtain the material failure strain and multiple time-strain curves at multiple load levels at each creep temperature;

[0034] The parameter calculation module is used to solve the creep damage evolution parameters of the composite material by the probabilistic t distribution method and the fitting method according to all the time-strain curves at each creep temperature, so as to obtain the creep rate formula;

[0035] The creep damage and creep life calculation module is used to obtain the creep damage and creep life of the tested ceramic matrix composite material according to the creep rate formula and the material failure strain through a finite element simulation method.

[0036] Compared with existing technologies, the present invention's method for calculating creep damage and creep life of ceramic matrix composites can quickly and reasonably predict creep damage and creep life of ceramic matrix composites, providing support for the forward design and engineering application of ceramic matrix composite structures, and improving the iteration speed and R&D efficiency of ceramic matrix composite structures. It has the following advantages:

[0037] 1. Considering the invalidity of data caused by various factors during the test, invalid data were eliminated;

[0038] 2. Taking into account the dispersion of effective data caused by the preparation process of ceramic matrix composite materials during the test, different creep fitting parameters were randomly selected during the calculation process to calculate the creep, ensuring the accuracy of the calculation;

[0039] 3. The creep analysis is performed in an iterative manner, taking into account creep damage and then the stress relaxation during the creep process of ceramic matrix composites, thereby improving the accuracy of creep analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] 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.

[0041] Figure 1 Flowchart of the method for calculating creep damage and creep life of the ceramic matrix composite material of the present invention;

[0042] Figure 2 The present invention is an implementation process of the method for calculating creep damage and creep life of ceramic matrix composite materials;

[0043] Figure 3The present invention provides an architecture for a system for calculating creep damage and creep life of ceramic matrix composite materials.

[0044] Figure 4 Creep curve of composite material plate with holes at 300℃-100Mpa;

[0045] Among them, 301 is a time-strain curve acquisition module; 302 is a parameter calculation module; 303 is a creep damage and creep life calculation module. DETAILED DESCRIPTION

[0046] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0047] 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.

[0048] The present invention discloses a method for calculating creep damage and creep life of ceramic matrix composite materials. Figure 1 and Figure 2 As shown, the method includes the following steps:

[0049] S1. Conduct creep tests on simulated test pieces to obtain material failure strain and multiple time-strain curves at multiple load levels at each creep temperature;

[0050] S2. Based on all the time-strain curves at each creep temperature, solving the creep damage evolution parameters of the composite material by a probabilistic t-distribution method and a fitting method to obtain a creep rate formula;

[0051] S3. Using a finite element simulation method, the creep damage and creep life of the ceramic matrix composite material under test are obtained according to the creep rate formula and the material failure strain.

[0052] Furthermore, in step S1, a creep test is performed on the simulated test piece to obtain the material failure strain and multiple time-strain curves at multiple load levels at each creep temperature, including:

[0053] S11. Performing a tensile test on the simulated test piece at a given creep temperature to obtain a tensile curve, and obtaining the material tensile ratio limit and the material failure strain from the tensile curve;

[0054] S12. Obtain the stresses corresponding to the 80% material tensile limit, the 100% material tensile limit, and the 120% material tensile limit, respectively. Apply each of the stresses at each creep temperature, and perform in-plane tensile creep tests to obtain time-strain curves. During implementation, 5-10 tests can be performed at each creep temperature for each of the 80% material tensile limit, the 100% material tensile limit, and the 120% material tensile limit to ensure sufficient data for subsequent calculation of creep damage evolution parameters for the composite material.

[0055] Furthermore, in step S2, based on all the time-strain curves at each creep temperature, the creep damage evolution parameters of the composite material are solved by the probabilistic t distribution method and the fitting method to obtain the creep rate formula, including:

[0056] S21, extracting mechanical property parameters of the composite material from each time-strain curve at each creep temperature, wherein the mechanical property parameters of the composite material include initial modulus and maximum fracture strain;

[0057] S22. According to the probabilistic t-distribution method, the homogeneity of the mechanical property parameters of the composite material at each creep temperature is determined, and the time-strain curves corresponding to the mechanical property parameters of the composite material determined to be non-homogeneous are eliminated;

[0058] S23. Using the stress, creep temperature, and time-strain of all the remaining time-strain curves after elimination, fitting and solving are performed to obtain creep damage evolution parameters of the composite material and obtain a creep rate formula.

[0059] Furthermore, in step S22, the homogeneity of the mechanical property parameters of the composite material at each creep temperature is judged according to the probabilistic t-distribution method, including:

[0060] S221. When performing homogeneity judgment on the composite material mechanical property parameters at each creep temperature in each round, select the maximum or minimum composite material mechanical property parameter in that round as the judgment data, and calculate the remaining average values ​​and standard deviations of all the remaining composite material mechanical property parameters;

[0061] S222. Calculate a distribution coefficient using the determined data, the remaining average values, and the remaining standard deviations. When the distribution coefficient is greater than the t distribution coefficient, determine that the determined data is non-homogeneous and eliminate it.

[0062] In specific implementation, the following formula can be used , make a homogeneity judgment if: When the judged data X i It is not homogeneous with the average value of the remaining (n-1) data and is not valid test data and needs to be eliminated. It is worth noting that: is the t distribution coefficient, which can be found from the t test critical value table. i is the i-th judged data, is the average value of all data except the i-th data, is the standard deviation of the data other than the i-th data.

[0063] Furthermore, in step S222, when performing homogeneity judgment, the initial modulus is first judged, and then the maximum fracture strain is judged, until the final time-strain curve at each creep temperature is obtained.

[0064] Furthermore, the creep rate formula is , where σ is stress, t is creep time, and T is creep temperature; ε c is the strain, and C1 to C7 are the creep damage evolution parameters of the composite material. When solving the creep rate formula for the creep damage evolution parameters of the composite material, the remaining strain-time curve after removing invalid data can be randomly selected and fitted with seven strain-time curves under different conditions (load, temperature). This process can be repeated multiple times to obtain multiple sets of different creep damage evolution parameters.

[0065] Furthermore, in step S3, the creep damage and creep life of the ceramic matrix composite material under test are obtained according to the creep rate formula and the material failure strain by a finite element simulation method, including:

[0066] S31, performing finite element meshing on the ceramic matrix composite material to be tested, and extracting the fiber direction of each mesh unit;

[0067] S32, applying a test stress and a test temperature field to the ceramic matrix composite material under test by a simulation method, obtaining a simulated stress field and a simulated structural displacement field under the current stress, and extracting the current temperature of each grid unit and the current simulated stress along the fiber direction;

[0068] S33, calculating the current simulation strain using the creep rate formula according to the current temperature, the current simulation stress and the creep time;

[0069] S34, calculating a current equivalent modulus of each of the mesh cells using the simulated stress and the simulated strain, and calculating a current creep damage of each of the mesh cells based on the current equivalent modulus and a previous equivalent modulus of the mesh cell under a previous stress;

[0070] S35. Determine the damage of the ceramic matrix composite material under test according to the material damage strain and the simulated structural displacement field using a damage criterion, and obtain the time corresponding to when the structure is judged to be damaged as the creep life.

[0071] Furthermore, in step S35, the failure criterion is used to determine the failure of the ceramic matrix composite material under test according to the material failure strain and the simulated structural displacement field, including:

[0072] S351. According to the unit destruction criterion in the destruction criterion, when the current simulation strain of the mesh unit is greater than the material destruction strain, it is determined that the mesh unit is destroyed.

[0073] S352. Obtain a maximum displacement from the simulated structural displacement field using a structural destruction criterion in the destruction criterion. When the maximum displacement increment in a current unit time is greater than a given multiple of the maximum displacement increment in a previous unit time, it is determined that the tested ceramic matrix composite material structure is destroyed.

[0074] During implementation, the grid unit failure is first determined. If the grid unit is not destroyed, the test stress and temperature field are continuously applied until the grid unit failure conditions are met. Then, the ceramic matrix composite material structure is determined to be damaged. If the structure is not destroyed, the test stress and temperature field are continuously applied until the structure is destroyed and the loading is stopped.

[0075] Based on the same inventive concept, an embodiment of the present invention further provides a system for calculating creep damage and creep life of ceramic matrix composite materials, as described in the following embodiments. Since the principle of solving the problem by the system for calculating creep damage and creep life of ceramic matrix composite materials is similar to the method for calculating creep damage and creep life of ceramic matrix composite materials, the implementation of the system for calculating creep damage and creep life of ceramic matrix composite materials can refer to the implementation of the method for calculating creep damage and creep life of ceramic matrix composite materials disclosed in the above embodiments, 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, the implementation of hardware, or a combination of software and hardware, is also possible and conceived.

[0076] Figure 3 This is a structural block diagram of a calculation system for creep damage and creep life of ceramic matrix composite materials disclosed in an embodiment of the present invention, such as Figure 3 As shown, the system includes a time-strain curve acquisition module 301, a parameter calculation module 302 and a creep damage and creep life calculation module 303. The structure is described below.

[0077] The time-strain curve acquisition module 301 is used to perform a creep test on a simulated test piece to obtain the material failure strain and multiple time-strain curves at each creep temperature;

[0078] The parameter calculation module 302 is used to solve the creep damage evolution parameters of the composite material by the probabilistic t-distribution method and the fitting method according to all the time-strain curves at each creep temperature, and obtain the creep rate formula;

[0079] The creep damage and creep life calculation module 303 is used to obtain the creep damage and creep life of the ceramic matrix composite material under test according to the creep damage evolution parameter of the composite material and the material failure strain through a finite element simulation method.

[0080] The present invention illustrates the calculation method of creep damage and creep life of the ceramic matrix composite material through the following examples:

[0081] Step 1: Conduct creep tests on simulated test pieces to obtain creep data (time-strain curves) at different temperatures.

[0082] Step 2: Eliminate invalid data and fit to determine the creep damage evolution parameters of the composite material. Taking five sets of time-strain curves under the same conditions of 80 MPa-1100 °C as an example, the mechanical properties parameters of the composite material of five samples under the same temperature conditions are obtained as shown in Table 1, and the t distribution coefficient is shown in Table 2 below:

[0083] Table 1: Mechanical properties of composite materials from time-strain curves

[0084]

[0085] Table 2: t distribution coefficient

[0086]

[0087] The homogeneity of the data in Table 1 above is determined according to the method of steps S221 and S222:

[0088] First, among the five curves under the same temperature condition, the data of the first sample is used as the judged data, and the initial modulus mean of the other four curves is 182.75 and the standard deviation is 6.18. Obviously, at this time, t i It is 6.19, which is greater than t4, 0.005. The data of the first sample should be eliminated.

[0089] Secondly, for the remaining four sets of data, the data of the third sample is used as the judgment data. The mean creep rupture strain of the remaining three samples is 3271, and the standard deviation is 31.59. Obviously, at this time t iThe value is 11.3, which is greater than t3, 0.005. The third set of data should be eliminated. The validity of the remaining data is determined to be valid.

[0090] Again, for the remaining second, fourth, and fifth samples, together with the valid data of other time-strain curves under temperature conditions, data are randomly extracted and fitted to the creep rate formula respectively, and 10 groups of creep damage evolution parameters of composite materials can be obtained as shown in Table 3 below:

[0091] Table 3: Extracting different curves to obtain multiple sets of composite material creep damage evolution parameters

[0092]

[0093] 3. Using the finite element method and iterative calculation method, the creep damage, creep strain and creep life of ceramic matrix composite materials are analyzed. Figure 4 As shown, the creep curve under 1300℃-100Mpa can be obtained. Figure 4 As shown in Figure 2, the creep life can be predicted to be 154 h using the failure criterion.

[0094] Compared with the existing technology, the calculation method of creep damage and creep life of ceramic matrix composite materials of the present invention can quickly and reasonably predict the creep damage and creep life of ceramic matrix composite materials, provide support for the forward design and engineering application of ceramic matrix composite structures, improve the iteration speed and R&D efficiency of ceramic matrix composite structures, and have the following advantages:

[0095] 1. Considering the invalidity of data caused by various factors during the test, invalid data were eliminated;

[0096] 2. Taking into account the dispersion of effective data caused by the preparation process of ceramic matrix composite materials during the test, different creep fitting parameters were randomly selected during the calculation process to calculate the creep, ensuring the accuracy of the calculation;

[0097] 3. The creep analysis is performed in an iterative manner, taking into account creep damage and then the stress relaxation during the creep process of ceramic matrix composites, thereby improving the accuracy of creep analysis.

[0098] 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 calculating creep damage and creep life of ceramic-based composite materials is implemented.

[0099] Specifically, the computer device may be a computer terminal, a server or a similar computing device.

[0100] 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 calculating creep damage and creep life of ceramic matrix composite materials.

[0101] 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.

[0102] 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.

[0103] 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 calculating creep damage and creep life of ceramic matrix composite materials, characterized in that: include: Conduct creep tests on simulated test pieces to obtain material failure strain and multiple time-strain curves at multiple load levels at each creep temperature; According to all the time-strain curves at each creep temperature, the creep damage evolution parameters of the composite material are solved by the probability theory t distribution method and the fitting method to obtain the creep rate formula, including: extracting the mechanical property parameters of the composite material from each time-strain curve at each creep temperature, the mechanical property parameters of the composite material including the initial modulus and the maximum fracture strain; according to the probability theory t distribution method, performing homogeneity judgment on the mechanical property parameters of the composite material at each creep temperature, and eliminating the time-strain curves corresponding to the mechanical property parameters of the composite material judged to be non-homogeneous; using the stress, creep temperature and time-strain of all the remaining time-strain curves after elimination, performing fitting and solving to obtain the creep damage evolution parameters of the composite material, and obtaining the creep rate formula, wherein the creep rate formula is , σ is stress, t is creep time, T is creep temperature; ε c is the strain, C1~C7 are the creep damage evolution parameters of the composite material; The creep damage and creep life of the tested ceramic matrix composite material are obtained by a finite element simulation method according to the creep rate formula and the material failure strain.

2. The method for calculating creep damage and creep life of ceramic matrix composite materials according to claim 1, characterized in that: Conduct creep tests on simulated test pieces to obtain material failure strain and multiple time-strain curves at each creep temperature, including: Performing a tensile test on a simulated test piece at a given creep temperature to obtain a tensile curve, and obtaining the material tensile ratio limit and the material failure strain from the tensile curve; The stresses corresponding to the 80% material tensile ratio limit, the 100% material tensile ratio limit, and the 120% material tensile ratio limit are obtained respectively, and each of the stresses is loaded at each creep temperature. An in-plane tensile creep test is performed to obtain a time-strain curve.

3. The method for calculating creep damage and creep life of ceramic matrix composite materials according to claim 1, characterized in that: According to the probability theory t distribution method, the homogeneity of the mechanical property parameters of the composite material at each creep temperature is judged, including: When performing each round of homogeneity judgment on the mechanical property parameters of the composite material at each creep temperature, the maximum or minimum mechanical property parameter of the composite material in the round is selected as the judgment data, and the remaining average values ​​and standard deviations of all the remaining mechanical property parameters of the composite material are calculated; The distribution coefficient is calculated by the judged data, the remaining average values, and the remaining standard deviations. When the distribution coefficient is greater than the t distribution coefficient, the judged data is judged to be non-homogeneous and is eliminated.

4. The method for calculating creep damage and creep life of ceramic matrix composite materials according to claim 3, characterized in that: When making a homogeneity judgment, the initial modulus is first judged, and then the maximum fracture strain is judged, until the final time-strain curve at each creep temperature is obtained.

5. The method for calculating creep damage and creep life of ceramic matrix composite materials according to claim 1, characterized in that: The creep damage and creep life of the tested ceramic matrix composite material are obtained by a finite element simulation method according to the creep rate formula and the material failure strain, including: Perform finite element meshing on the tested ceramic matrix composite material and extract the fiber direction of each mesh unit; Applying a test stress and a test temperature field to the ceramic matrix composite material under test by a simulation method, obtaining a simulated stress field and a simulated structural displacement field under the current stress, and extracting the current temperature of each grid unit and the current simulated stress along the fiber direction; Calculating the current simulation strain using the creep rate formula based on the current simulation stress, current temperature, and creep time; Calculating a current equivalent modulus of each of the mesh cells using the simulated stress and the simulated strain, and calculating a current creep damage of each of the mesh cells based on the current equivalent modulus and a previous equivalent modulus of the mesh cell under a previous stress; The ceramic matrix composite material under test is judged to be damaged by using a damage criterion, according to the material damage strain and the simulated structural displacement field, and the time corresponding to the judgment of structural damage is obtained as the creep life.

6. The method for calculating creep damage and creep life of ceramic matrix composite materials according to claim 5, characterized in that: The method comprises: determining the damage of the ceramic matrix composite material under test according to the damage criterion and the material damage strain and the simulated structural displacement field, including: According to the unit destruction criterion in the destruction criterion, when the current simulation strain of the grid unit is greater than the material destruction strain, the grid unit is determined to be destroyed; The maximum displacement is obtained from the displacement field of the simulated structure by using the structural destruction criterion in the destruction criterion. When the maximum displacement increment in the current unit time is greater than a given multiple of the maximum displacement increment in the previous unit time, it is determined that the tested ceramic matrix composite material structure is destroyed.

7. A calculation system for creep damage and creep life of ceramic matrix composite materials, characterized in that: include: A time-strain curve acquisition module, which is used to perform creep tests on simulated test pieces to obtain material failure strain and multiple time-strain curves at multiple load levels at each creep temperature; A parameter calculation module is used to solve the creep damage evolution parameters of the composite material according to all the time-strain curves at each creep temperature by a probabilistic t distribution method and a fitting method to obtain a creep rate formula, including: extracting the mechanical performance parameters of the composite material from each time-strain curve at each creep temperature, wherein the mechanical performance parameters of the composite material include an initial modulus and a maximum fracture strain; performing a homogeneity judgment on the mechanical performance parameters of the composite material at each creep temperature according to the probabilistic t distribution method, and eliminating the time-strain curves corresponding to the mechanical performance parameters of the composite material that are judged to be non-homogeneous; using the stress, creep temperature, and time-strain of all the remaining time-strain curves after elimination to perform fitting and solve to obtain the creep damage evolution parameters of the composite material, and obtain a creep rate formula, wherein the creep rate formula is , σ is stress, t is creep time, T is creep temperature; ε c is the strain, C1~C7 are the creep damage evolution parameters of the composite material; A creep damage and creep life calculation module is used to obtain the creep damage and creep life of the tested ceramic matrix composite material according to the creep rate formula and the material failure strain through a finite element simulation method.

Images