CN112329299A - Gas diffusion and oxidation evolution calculation method in ceramic matrix composite structure - Google Patents
Gas diffusion and oxidation evolution calculation method in ceramic matrix composite structure Download PDFInfo
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Abstract
The invention discloses a gas diffusion and oxidation evolution calculation method in a ceramic matrix composite structure, which comprises the following steps: determining temperature and load distribution in the structural member; determining a matrix crack distribution in the structure; establishing an equivalent diffusion coefficient model of the fiber bundle dimension based on matrix crack distribution, and predicting a gas flow channel in the fiber bundle; averaging the total gas diffusion amount in the channel, and establishing a fiber bundle composite material scale equivalent diffusion coefficient model related to matrix crack distribution; establishing an RVE model; establishing an equivalent diffusion coefficient model of RVE scale, and calculating gas concentration and oxidation product distribution in the structure; calculating the growth thickness of the oxide at the positions of cracks and pores in each unit; and updating the filling condition of the gas channel, and calculating a new equivalent diffusion coefficient field and an oxidation product distribution again. The evolution conditions of gas channels with different scales in the ceramic matrix composite structure are predicted; the calculation of the change of the gas concentration distribution in the structure caused by the channel difference is realized.
Description
Technical Field
The invention belongs to the field of oxidation analysis of ceramic matrix composites, and particularly relates to a calculation method for structural oxidation of a woven ceramic matrix composite, in particular to a calculation method for oxidation evolution and gas concentration distribution of oxidation products with uneven distribution caused by considering gas concentration distribution difference inside a structure.
Background
The ceramic matrix Composite Materials (CMCs) have excellent mechanical properties at high temperature, so that the ceramic matrix composite materials have wide application prospects in the field of hot end parts of aircraft engines. In the service process, the ceramic matrix composite structural member is subjected to the coupling action of high temperature, stress and oxidation, so that the structural strength is reduced. The oxidation calculation of the CMCs structure in the high-temperature environment is realized, the oxidized morphology is obtained, initial parameters can be provided for the calculation of the residual mechanical properties after oxidation, and the method is the basis of the strength analysis and the service life prediction of the oxidized CMCs structure.
In order to reliably apply the ceramic matrix composite material to engineering practice, a plurality of scholars at home and abroad research the oxidation behavior of the ceramic matrix composite material under the stress oxidation environment. At present, most of the existing methods are material-grade oxidation kinetic analysis, and the structural-grade oxidation research of the ceramic matrix composite is not disclosed. Such as: a prediction method of the internal oxidation morphology of a one-way ceramic matrix composite material under a stress water vapor environment (Chinese patent CN110246548A) discloses a prediction method of the internal oxidation morphology of a one-way ceramic matrix composite material under a stress water vapor environment. A prediction method for the internal oxidation morphology of a ceramic matrix composite material in a stress oxidation environment (Chinese patent CN111243681A) discloses a prediction method for the internal oxidation morphology of a unidirectional SiC/SiC composite material in a stress oxidation environment, which considers the morphology change of an oxidation notch of a C interface.
The method is mainly based on an oxidation kinetic model to calculate the oxidation of the CMCs material grade, and needs to determine the environmental parameters (such as temperature, pressure, gas concentration and the like) of the contact surface of the material and the oxidation environment in advance. However, because of the difference of internal matrix cracks and the distribution of pores among fiber bundles in the actual CMCs structure, oxidation gas channels with different sizes exist. This phenomenon results in different concentrations of gas at various points within the structure and therefore different degrees of oxidation. Based on the existing material-level model, the gas concentration at each point inside the structure is difficult to determine, and the distribution of oxidation products inside the structural member in the reaction diffusion process cannot be predicted. Therefore, it is necessary to provide a calculation method for the structural oxidation of the woven ceramic matrix composite, which solves the problem of gas distribution caused by the difference of diffusion channels and realizes the structural oxidation calculation of the CMCs.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a calculation method for gas diffusion and oxidation evolution in a ceramic matrix composite structure.
In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:
the gas diffusion and oxidation evolution calculation method in the ceramic matrix composite structure comprises the following steps:
step 1: determining temperature and load distribution in the structural member;
step 2: determining the matrix crack distribution in the structure: calculating the temperature and stress related matrix crack density rho in the structure based on the matrix crack model according to the temperature field and the stress field in the step 1crackWidth d of crack of matrixcrack；
And step 3: establishing an equivalent diffusion coefficient model of the fiber bundle dimension based on matrix crack distribution, and predicting a gas flow channel in the fiber bundle; based on the matrix crack distribution, it is considered that in the fiber bundle composite material having an axial length L, the matrix crack width is dcrackThe density of matrix cracks is rhocrackAveraging the total gas diffusion amount in the channel, and establishing a fiber bundle composite material scale equivalent diffusion coefficient model related to matrix crack distribution;
and 4, step 4: establishing a weaving ceramic matrix composite representative volume unit model, namely an RVE model; carrying out image recognition on an XCT scanning image of a woven CMCs mesoscopic structure used by a structural member, describing the warp yarn trend by adopting a cosine function, describing the weft yarn by a straight line form, observing and acquiring geometric parameters, and establishing a corresponding RVE model;
and 5: establishing an equivalent diffusion coefficient model of RVE scale, and representing the gas circulation of the structure; based on pore characteristics, regarding the fiber bundles as homogeneous materials, substituting the fiber bundle composite material equivalent diffusion coefficient model constructed in the step 3 into yarns of the RVE model, and establishing an equivalent diffusion coefficient model of the weaving CMCs on the RVE scale;
step 6: calculating a gas concentration distribution in the structure; solving by adopting a finite difference method, and calculating the gas concentration distribution of each unit in the structure along the transmission direction;
and 7: calculating the distribution of oxidation products in the structure; calculating the growth thickness z of the oxide at the cracks and the pores in each unit according to the gas concentration calculated in the step 6;
and 8: and (4) calculating the filling condition of the gas channel according to the result of the step (7), including the change of the crack width and the pore characteristic quantity, substituting the new gas channel characteristic quantity into the step (3-5), calculating a new equivalent diffusion coefficient field, realizing the recalibration of the gas channel, repeating the step (6-7), and realizing the calculation of the distribution of the oxidation products in the structural member at different times.
The preferred scheme is as follows:
in the second step, the calculation method of the crack density of the matrix comprises the following steps:
where σ represents the stress in the fiber bundle; m, b0Respectively representing Weibull modulus and Weibull matrix cracking characteristic strength, and can be determined by fitting a transition section of a tensile test curve; l issatThe saturated crack spacing can be obtained through experimental observation;
the calculation method of the crack width of the matrix comprises the following steps:
in the formula (d)0Crack width at Normal temperature, T0The temperature of the material preparation, delta T is the temperature difference between the current temperature and the normal temperature, EfIs the modulus of elasticity, V, of the fibermIs the volume content, alpha, of the matrix in the fiber bundle compositem、αfThe thermal expansion coefficients of the matrix and the fiber are respectively.
In the third step, the first step is that,
the fiber bundle composite material scale equivalent diffusion coefficient model related to matrix crack distribution is as follows:
in the formula, NAIn order to be a gas diffusion flux,
denotes the concentration gradient, DgasThe diffusion coefficient of oxygen in a single crack channel;
considering that in the range of 0-1500 deg.C, O2Has a molecular mean free path of 10-7m order of magnitude, the crack size is 10-7m order of magnitude, belonging to mixed diffusion and can be determined according to diffusion coefficient DFRelative Fick diffusion and diffusion coefficient DKThe associated Knudsen diffusion empirical formula is calculated:
wherein Fick diffusion:
in a binary diffusion system (O)2in-CO), parameters
Can be calculated by the following formula:
wherein A, B respectively represent gas O2And CO;
knudsen diffusion:
therefore, the mathematical relationship between the equivalent diffusion coefficient of the fiber bundle composite material and the matrix crack distribution can be established:
in the formula, T is ambient temperature and has a unit of K, P is ambient pressure and has a unit of Pa, RgIs a gas constant, and has the unit J/(mol/K), ΣvIs the volume of diffusion of the molecules,
is the molar mass of the mixed gas.
In the fifth step, the construction method of the equivalent diffusion coefficient model of the RVE scale comprises the following steps: the length of any yarn i is assumed to be LiStress value set to σiThe yarn has a matrix crack width of
Equivalent diffusion coefficient in yarn:
gas diffusion in each yarn crack in RVE model:
wherein A isiIs the cross-sectional area of the yarn flow, Ai＝2πrLi，
Is the concentration gradient in the direction of gas flow;
the gas diffusion in the pores in the RVE model obeys Fick's law, and the gas diffusion quantity is as follows:
wherein A isporeThe cross section of the pores vertical to the gas flow direction can be converted by the porosity; dFFick diffusion coefficient;
the average calculation of the amount of the fluent gas was made from the cross-sectional area a of the RVE model perpendicular to the diffusion direction, the gas diffusion flux in RVE being:
equivalent diffusion coefficient of RVE model:
in the sixth step, the method for calculating the gas concentration distribution in the structure comprises the following steps: the relationship between diffusion and oxidation kinetics in the oxidation process can be described by a partial differential equation according to the mass conservation law:
wherein ε is the porosity of CMCs, cAIs the gas concentration, t is the time，DeffIs the RVE equivalent diffusion coefficient, R, in step 5AIs the reaction rate.
In the seventh step, the calculation method of the oxide growth thickness z at the cracks and pores in each unit is as follows:
in the formula (I), the compound is shown in the specification,
is SiO2The molar mass of (a) is,
is SiO2The density of (a) of (b),
is O2In SiO2Diffusion coefficient of (1), c0In terms of oxygen concentration, t is the oxidation time.
In the eighth step, the method for calculating the change of the crack width and the pore characteristic quantity comprises the following steps:
width of crack:
d′crack＝dcrack-2dz
variation in pore characteristics:
wherein dz represents the thickness variation of the material, and is the difference between the growth thickness of the oxide layer and the recession thickness of SiC, and can be obtained according to the ratio of the oxidation chemical equation:
VRVErepresenting RVE model volume, dV represents pore volume change, related to oxidation product thickness:
dV＝4πrL·dz
wherein r is the equivalent radius of the fiber bundle and L is the length of the warp fiber bundle.
Compared with the prior art, the invention has the following advantages:
1. the calculation method for the oxidation of the ceramic matrix composite structure provided by the invention considers the gas concentration distribution change caused by the difference of gas channels in the structure in the reaction diffusion process. Based on the porous medium diffusion theory, an equivalent diffusion coefficient model of the fiber bundle composite material scale and the woven RVE scale is provided, the oxidation process after the reaction diffusion interaction is simulated, and the method is the basis of strength analysis and service life prediction of a structural member.
2. Establishing equivalent diffusion coefficient fields related to crack and pore distribution, and predicting the evolution conditions of gas channels with different scales in the ceramic matrix composite structure;
3. the change calculation of the gas concentration distribution in the structure caused by channel difference is realized;
4. the oxidation evolution of the CMCs structure level and the calculation of the gas concentration distribution under different working conditions are realized.
Drawings
FIG. 1 is a flow chart of the structural oxidation evolution and gas concentration distribution of a woven ceramic matrix composite;
FIG. 2 is a RVE model of the woven ceramic matrix composite material created;
FIG. 3 is an equivalent diffusion coefficient distribution in a CMCs structure at an initial stage of oxidation;
FIG. 4 is a thickness distribution of oxidation products in a CMCs structure at an initial stage of oxidation.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
Example (b): the calculation method for the structural oxidation of the woven ceramic matrix composite material is used for calculating the distribution of oxidation products of the CMCs regulating sheet based on the initial conditions of the actual working conditions.
Step 1: establishing a macroscopic geometric model of the adjusting sheet, applying linearly changed temperature and pressure loads on the inner side of the adjusting sheet, applying constant loads on the outer side of the adjusting sheet, and calculating the temperature and stress distribution in the adjusting sheet through finite elements;
step 2: determining a matrix crack distribution in the structure. Calculating the temperature and stress related matrix crack density rho in the structure based on the matrix crack model according to the temperature field and the stress field in the step 1crackWidth d of crack of matrixcrack。
Wherein the matrix crack density is:
m，b0respectively representing the Weibull modulus and the Weibull matrix cracking characteristic strength. By fitting the transition section of the tensile test curve, m can be determined to be 3, b0160 MPa; through experimental observation, the saturated crack spacing Lsat＝357.1um。
The crack width of the matrix is:
in the formula (d)0Crack width at Normal temperature, T0The temperature of the material preparation, delta T is the temperature difference between the current temperature and the normal temperature, EfIs the modulus of elasticity, V, of the fibermIs the volume content, alpha, of the matrix in the fiber bundle compositem、αfThe thermal expansion coefficients of the matrix and the fiber are respectively.
The material parameters are listed in the following table:
TABLE 1 SiC/SiC fiber bundle composite parameters
And step 3: and establishing an equivalent diffusion coefficient model of the fiber bundle dimension based on matrix crack distribution, and predicting the gas flow channel in the fiber bundle. Based on the matrix crack distribution, consider a crack having an axial length ofL fiber bundle composite material having a matrix crack width dcrackThe density of matrix cracks is rhocrackAveraging the total gas diffusion amount in the channel, and establishing a fiber bundle composite material scale equivalent diffusion coefficient model related to matrix crack distribution:
wherein N isAIn order to be a gas diffusion flux,
denotes the concentration gradient, DgasIs the diffusion coefficient of oxygen in a single crack channel.
Considering O in the range of 0-1500 DEG C2Has a molecular mean free path of 10-7m order of magnitude, the crack size is 10-7m order of magnitude, belonging to mixed diffusion and can be diffused according to Fick (diffusion coefficient D)F) Diffusion with Knudsen (diffusion coefficient D)K) An empirical formula is used for calculation:
wherein Fick diffusion:
knudsen diffusion:
in the formula, T is the ambient temperature (K), P is the ambient pressure (Pa), and R isgIs the gas constant (J/(mol/K)) ΣvIs the volume of diffusion of the molecules,
is a mixed gasIn a binary diffusion system (O)2in-CO), parameters
Can be obtained by the following calculation (A, B represents gas O respectively)2With CO):
wherein M isA＝32g/mol，MA＝28g/mol，ΣvA＝16cm3/mol，ΣvB＝18.9cm3/mol。
Substituting the formulas into a fiber bundle composite material scale equivalent diffusion coefficient model to establish a mathematical relation between the fiber bundle composite material equivalent diffusion coefficient and matrix crack distribution (crack density and crack width):
substituting the finite element calculation result of the adjusting sheet, and calculating the equivalent diffusion coefficient of the fiber bundle in each unit.
And 4, step 4: and establishing an RVE model. And carrying out image recognition on the mesoscopic structure of the woven ceramic matrix composite material used by the structural member to obtain the mesoscopic geometric parameters. Selecting a single-layer fiber cloth in the z direction, selecting a part between two weft yarns in the x direction, and selecting two warp yarns in different winding directions in the y direction to obtain a Representative Volume Element (RVE) of the woven ceramic matrix composite. The fiber bundles (with the cross section width of 0.94mm and the height of 0.22mm) in the model are arranged in the same way as the actual material structure, the warp yarn trend is described by adopting a cosine function (with the amplitude of 0.22mm and the wavelength of 10mm), and the weft yarns are distributed in a straight line form.
And 5: and establishing an equivalent diffusion coefficient model of the RVE scale. Based on the pore characteristics, the yarns are regarded as homogeneous materials, and the fiber bundle composite equivalent diffusion coefficient model constructed in the step 3 is substituted to establish an equivalent diffusion coefficient model of the weaving ceramic matrix composite in RVE scale. For RVE modelType, in which the length of any yarn i is assumed to be LiStress value set to σiThe yarn has a matrix crack width of
Equivalent diffusion coefficient in yarn:
gas diffusion in each yarn crack in RVE model:
wherein A isiIs the cross-sectional area of the yarn flow, Ai＝2πrLi，
Is the concentration gradient in the direction of gas flow. The gas diffusion in the pores in the RVE model obeys Fick's law, and the gas diffusion quantity is as follows:
wherein A isporeThe cross section of the pores vertical to the gas flow direction can be converted by the porosity; dFThe Fick diffusion coefficient.
The average calculation of the amount of the fluent gas was made from the cross-sectional area a of the RVE model perpendicular to the diffusion direction, the gas diffusion flux in RVE being:
calculating the equivalent diffusion coefficient of each unit RVE model of the adjusting sheet:
step 6: and solving the gas concentration distribution in the regulating sheet. The following assumptions were made for the model: (1) the same unit is regarded as a uniform material, the condition parameters are equal, the diffusion phenomenon does not occur inside, and the diffusion is only carried out between the adjacent units; (2) in a small time increment (dt ═ 1s), the gas diffusion process is treated as a one-dimensional steady-state mass transfer.
The relationship between diffusion and oxidation kinetics in the oxidation process can be described by a partial differential equation according to the mass conservation law:
wherein ε is the porosity of CMCs, cAIs the gas concentration, t is the time, DeffIs the RVE equivalent diffusion coefficient, R, in step 5AIs the reaction rate. And solving by adopting a finite difference method, and calculating the gas concentration distribution of each unit in the structure along the transmission direction.
And 7: solving the distribution of the degree of oxidation in the conditioning disk, according to the gas concentration calculated in step 6, passing the SiO gas in unit section through the SiC oxidation kinetic model in time increment dt2O of (A) to (B)2The amount of substance is dn, then:
and calculating the growth thickness of the oxide at the cracks and pores in each unit according to the chemical reaction formula and the boundary conditions:
fig. 4 shows the oxide thickness profile in nm at the initial stage of oxidation.
And 8: and (3) calculating the filling condition of the gas channel according to the oxide thickness distribution in the step (7), wherein the filling condition comprises the change of the crack width and the pore characteristic quantity:
d′crack＝dcrack-2dz
wherein dz represents the thickness variation of the material, and is the difference between the growth thickness of the oxide layer and the recession thickness of SiC, and can be obtained according to the ratio of the oxidation chemical equation:
VRVErepresenting RVE model volume, dV represents pore volume change, related to oxidation product thickness:
dV＝4πrL·dz
the equivalent radius r of the fiber bundle is 0.36mm, and the length L of the warp yarn is 1.6 mm.
If d'crack0, the crack channel within the unit heals,
the gas diffuses within the cell only through the pores. Substituting the new gas channel characteristic quantity into the step 3-5 to calculate a new equivalent diffusion coefficient field, and repeating the step 6-7 to realize the calculation of the distribution of the oxidation products in the CMCs regulating sheet at different times.
In the embodiment, according to given temperature and load conditions, reaction diffusion simulation can be performed on different CMCs structural members under different oxidation times, so that oxidation calculation of the structural members can be realized.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.
Claims (7)
1. The gas diffusion and oxidation evolution calculation method in the ceramic matrix composite structure is characterized by comprising the following steps: the method comprises the following steps:
step 1: determining temperature and load distribution in the structural member;
step 2: determining the matrix crack distribution in the structure: calculating the temperature and stress related matrix crack density rho in the structure based on the matrix crack model according to the temperature field and the stress field in the step 1crackWidth d of crack of matrixcrack；
And step 3: establishing an equivalent diffusion coefficient model of the fiber bundle dimension based on matrix crack distribution, and predicting a gas flow channel in the fiber bundle; based on the matrix crack distribution, it is considered that in the fiber bundle composite material having an axial length L, the matrix crack width is dcrackThe density of matrix cracks is rhocrackAveraging the total gas diffusion amount in the channel, and establishing a fiber bundle composite material scale equivalent diffusion coefficient model related to matrix crack distribution;
and 4, step 4: establishing a weaving ceramic matrix composite representative volume unit model, namely an RVE model; carrying out image recognition on an XCT scanning image of a woven CMCs mesoscopic structure used by a structural member, describing the warp yarn trend by adopting a cosine function, describing the weft yarn by a straight line form, observing and acquiring geometric parameters, and establishing a corresponding RVE model;
and 5: establishing an equivalent diffusion coefficient model of RVE scale, and representing the gas circulation of the structure; based on pore characteristics, regarding the fiber bundles as homogeneous materials, substituting the fiber bundle composite material equivalent diffusion coefficient model constructed in the step 3 into yarns of the RVE model, and establishing an equivalent diffusion coefficient model of the weaving CMCs on the RVE scale;
step 6: calculating a gas concentration distribution in the structure; solving by adopting a finite difference method, and calculating the gas concentration distribution of each unit in the structure along the transmission direction;
and 7: calculating the distribution of oxidation products in the structure; calculating the growth thickness z of the oxide at the cracks and the pores in each unit according to the gas concentration calculated in the step 6;
and 8: and (4) calculating the filling condition of the gas channel according to the result of the step (7), including the change of the crack width and the pore characteristic quantity, substituting the new gas channel characteristic quantity into the step (3-5), calculating a new equivalent diffusion coefficient field, realizing the recalibration of the gas channel, repeating the step (6-7), and realizing the calculation of the distribution of the oxidation products in the structural member at different times.
2. The method for calculating gas diffusion and oxidation evolution in a ceramic matrix composite structure of claim 1, wherein: in the second step, the calculation method of the crack density of the matrix comprises the following steps:
where σ represents the stress in the fiber bundle; m, b0Respectively representing Weibull modulus and Weibull matrix cracking characteristic strength, and can be determined by fitting a transition section of a tensile test curve; l issatThe saturated crack spacing can be obtained through experimental observation;
the calculation method of the crack width of the matrix comprises the following steps:
in the formula (d)0Crack width at Normal temperature, T0The temperature of the material preparation, delta T is the temperature difference between the current temperature and the normal temperature, EfIs the modulus of elasticity, V, of the fibermIs the volume content, alpha, of the matrix in the fiber bundle compositem、αfThe thermal expansion coefficients of the matrix and the fiber are respectively.
3. The method for calculating gas diffusion and oxidation evolution in a ceramic matrix composite structure of claim 1, wherein: in the third step, the first step is that,
the fiber bundle composite material scale equivalent diffusion coefficient model related to matrix crack distribution is as follows:
in the formula, NAIn order to be a gas diffusion flux,
denotes the concentration gradient, DgasThe diffusion coefficient of oxygen in a single crack channel;
considering that in the range of 0-1500 deg.C, O2Has a molecular mean free path of 10-7m order of magnitude, the crack size is 10-7m order of magnitude, belonging to mixed diffusion and can be determined according to diffusion coefficient DFRelative Fick diffusion and diffusion coefficient DKThe associated Knudsen diffusion empirical formula is calculated:
wherein Fick diffusion:
in a binary diffusion system (O)2in-CO), parameters
Can be calculated by the following formula:
wherein A, B respectively represent gas O2And CO;
knudsen diffusion:
therefore, the mathematical relationship between the equivalent diffusion coefficient of the fiber bundle composite material and the matrix crack distribution can be established:
in the formula, T is ambient temperature and has a unit of K, P is ambient pressure and has a unit of Pa, RgIs a gas constant, and has the unit J/(mol/K), ΣvIs the volume of diffusion of the molecules,
is the molar mass of the mixed gas.
4. The method for calculating gas diffusion and oxidation evolution in a ceramic matrix composite structure of claim 1, wherein: in the fifth step, the construction method of the equivalent diffusion coefficient model of the RVE scale comprises the following steps: the length of any yarn i is assumed to be LiStress value set to σiThe yarn has a matrix crack width of
Equivalent diffusion coefficient in yarn:
gas diffusion in each yarn crack in RVE model:
wherein A isiIs the cross-sectional area of the yarn flow, Ai＝2πrLi，
Is the concentration gradient in the direction of gas flow;
the gas diffusion in the pores in the RVE model obeys Fick's law, and the gas diffusion quantity is as follows:
wherein A isporeThe cross section of the pores vertical to the gas flow direction can be converted by the porosity; dFFick diffusion coefficient;
the average calculation of the amount of the fluent gas was made from the cross-sectional area a of the RVE model perpendicular to the diffusion direction, the gas diffusion flux in RVE being:
equivalent diffusion coefficient of RVE model:
5. the method for calculating gas diffusion and oxidation evolution in a ceramic matrix composite structure of claim 1, wherein: in the sixth step, the method for calculating the gas concentration distribution in the structure comprises the following steps: the relationship between diffusion and oxidation kinetics in the oxidation process can be described by a partial differential equation according to the mass conservation law:
wherein ε is the porosity of CMCs, cAIs the gas concentration, t is the time, DeffIs the RVE equivalent diffusion coefficient, R, in step 5ATo speed up the reactionAnd (4) rate.
6. The method for calculating gas diffusion and oxidation evolution in a ceramic matrix composite structure of claim 1, wherein: in the seventh step, the calculation method of the oxide growth thickness z at the cracks and pores in each unit is as follows:
in the formula (I), the compound is shown in the specification,
is SiO2The molar mass of (a) is,
is SiO2The density of (a) of (b),
is O2In SiO2Diffusion coefficient of (1), c0In terms of oxygen concentration, t is the oxidation time.
7. The method for calculating gas diffusion and oxidation evolution in a ceramic matrix composite structure of claim 1, wherein: in the eighth step, the method for calculating the change of the crack width and the pore characteristic quantity comprises the following steps:
width of crack:
d′crack＝dcrack-2dz
variation in pore characteristics:
wherein dz represents the thickness variation of the material, and is the difference between the growth thickness of the oxide layer and the recession thickness of SiC, and can be obtained according to the ratio of the oxidation chemical equation:
VRVErepresenting RVE model volume, dV represents pore volume change, related to oxidation product thickness:
dV＝4πrL·dz
wherein r is the equivalent radius of the fiber bundle and L is the length of the warp fiber bundle.
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| CN113139300A (en) * | 2021-05-14 | 2021-07-20 | 南京工程学院 | Ceramic micropore cracking strength quantitative prediction method, device, computer equipment and storage medium |
| CN113408181A (en) * | 2021-07-23 | 2021-09-17 | 南京航空航天大学 | Oxidation life prediction method for ceramic matrix composite structure |
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| CN113051794A (en) * | 2021-03-12 | 2021-06-29 | 武汉理工大学 | Method and device for calculating concentration diffusion of impurity elements of quartz and storage medium |
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| CN114491831A (en) * | 2021-12-24 | 2022-05-13 | 哈尔滨工业大学 | Non-uniform material dispersion crack J integration method based on phase-breaking field method |
| CN114491831B (en) * | 2021-12-24 | 2023-07-18 | 哈尔滨工业大学 | Non-uniform material diffusion crack J integration method based on fracture phase field method |
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