A method for simulating thermal shock damage of si c coating across scales
By combining cross-scale simulation methods with molecular dynamics and finite element models, the problem of inaccurate failure prediction of SiC coatings under extreme environments was solved, and quantitative optimization design of coating structures was realized, thereby improving the thermal shock resistance of SiC coatings.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTH CHINA UNIV OF TECH
- Filing Date
- 2026-03-23
- Publication Date
- 2026-06-05
AI Technical Summary
Existing technologies lack cross-scale modeling methods and cannot effectively combine the atomic-scale grain boundary thermal weakening mechanism with the micron-scale coating damage evolution, resulting in inaccurate failure prediction of SiC coatings in extreme aerospace environments, and lack of quantitative design criteria for microstructure parameters.
Molecular dynamics simulations were used to obtain the mechanical properties of SiC single crystals and grain boundaries. A cross-scale parameter mapping model was established to transform the intrinsic properties at the atomic scale into temperature-dependent constitutive relations in the mesoscopic finite element model. A finite element model of the coating, including parameterized interface roughness and polycrystalline structure, was constructed. Thermo-mechanical coupling calculations were performed to simulate the damage initiation and propagation process of the coating and to optimize the microstructure parameters.
It achieves cross-scale prediction from the atomic scale to the mesoscale, provides quantitative design criteria for thermal shock resistance of coatings, and improves the accuracy of failure prediction and structural design optimization capabilities of SiC coatings under extreme environments.
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Figure CN122154336A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of materials calculation and performance simulation technology, and in particular relates to a cross-scale simulation method for thermal shock damage of SiC coatings. Background Technology
[0002] C / SiC composites possess high specific strength, high specific modulus, low coefficient of thermal expansion, and excellent high-temperature mechanical properties, making them ideal candidate materials for thermal components such as thrust chambers and nozzle extensions in liquid rocket engines. However, during actual service, the oxidizing atmosphere (such as water vapor and oxygen) within the engine combustion chamber causes severe oxidation and ablation of carbon-based composites, significantly limiting their long-term service life. To address this issue, a SiC coating is typically applied to the C / SiC surface as an environmental barrier layer.
[0003] However, SiC coatings still face severe failure challenges in the extreme environments of the aerospace field, mainly in the following aspects: The coupled failure mechanism of "ablation-stripping" is complex: during service, the coating not only undergoes high-temperature oxidation but also endures severe thermal shock cycles (rapid heating and cooling rates with large temperature differences). The cyclic thermal stress caused by this thermal shock often leads to the initiation and propagation of microcracks in the coating, ultimately resulting in large-area peeling of the coating. Currently, the industry's understanding of coating failure is still limited to macroscopic morphological observation, lacking a deep understanding of its evolution from atomic bond breakage to micron-level cracks.
[0004] The mechanism of grain boundary thermal weakening at the atomic scale remains unclear: Existing research largely focuses on the theoretical strength of single-crystal SiC, but in actual fabrication (such as CVD), SiC coatings often exist in a polycrystalline morphology. At high temperatures, the atomic arrangement at grain boundaries is more disordered, and their thermal stability and intrinsic mechanical strength decrease much faster than within the grains (i.e., the "thermal weakening" phenomenon). Traditional simulation models often simplify the coating as an isotropic, homogeneous, continuous medium, neglecting the constitutive differences between grain boundaries with different orientations at high temperatures, leading to significant deviations between predicted results and actual failure modes.
[0005] The lack of quantitative design criteria for microstructure parameters: The thermal shock resistance of the coating is affected by the synergistic influence of various micro-geometric parameters such as interface roughness, grain size, and coating thickness.
[0006] Interface roughness: Although a rough interface can provide "mechanical interlocking" force, excessive roughness can cause severe stress concentration and become the source of cracks.
[0007] Grain size: Fine grains can strengthen materials, but high-density grain boundaries may provide more diffusion paths and failure sites at high temperatures.
[0008] Thickness effect: Thicker coatings provide better thermal shielding, but the increased residual stress also increases the risk of peeling.
[0009] The lack of cross-scale modeling methods: Most current simulation methods are limited to a single scale. Pure molecular dynamics simulations are too small (nanometer-scale) to reflect the geometric characteristics of real coatings; while traditional finite element simulations are too large (millimeters and above) to incorporate the physical essence of microstructure evolution. Existing technologies lack a cross-scale computational framework that can accurately map the evolution of grain boundary strength at the atomic scale to the micrometer-scale coating damage evolution.
[0010] Therefore, there is an urgent need to develop a cross-scale prediction method that can comprehensively consider atomic-scale thermal weakening mechanisms and micron-scale structural features, so as to achieve quantitative evaluation and precise optimization of the thermal shock resistance performance of SiC coatings. Summary of the Invention
[0011] The purpose of this invention is to provide a cross-scale simulation method for thermal shock damage of SiC coatings, which avoids the limitations of single-scale simulation and provides an effective tool for understanding the failure mechanism of coatings under complex environments and for rational structural design.
[0012] To achieve the above objectives, this invention provides a method for multi-scale simulation of thermal shock damage to SiC coatings, comprising the following steps: The evolution function of the mechanical properties of SiC single crystals and grain boundaries with temperature was obtained through molecular dynamics simulations. A cross-scale parameter mapping model is established based on the evolution function, which transforms the intrinsic properties (such as strength and fracture energy) at the atomic scale into temperature-dependent constitutive relations in the mesoscopic finite element model. A finite element model of the coating system, including parameterized interface roughness and polycrystalline structure, was constructed. The damage initiation and propagation process under thermal shock load was simulated by thermo-mechanical coupling calculation. The effects of microstructure parameters and thermal shock temperature on the thermal shock resistance of the coating were evaluated. Based on the evaluation results, the optimization range of each parameter (interface roughness Ra, coating grain size d, coating thickness t, initial interfacial bonding strength σ0, and service thermal shock temperature) is determined, and a quantitative design criterion for coating thermal shock resistance is formed.
[0013] Preferably, the evolution of the mechanical properties of SiC single crystals and grain boundaries with temperature is obtained through molecular dynamics simulations, specifically including: A SiC single crystal and a SiC bicrystal model containing grains, typical grain boundaries, and pre-cracks were constructed. The Tersoff potential function was used to describe the interatomic interactions. Tensile simulations were performed in the temperature range of 300K to 1900K to obtain the intrinsic mechanical properties of silicon carbide single crystal and at least one typical grain boundary structure at different temperatures, and the evolution function of the performance parameters with temperature was established.
[0014] Preferably, a cross-scale parameter mapping model is established based on the evolution function, transforming the intrinsic property laws at the atomic scale into temperature-dependent constitutive relations in the mesoscopic finite element model, specifically including: Based on the obtained evolution function, a cross-scale parameter mapping method is established to map atomic-scale intrinsic property parameters to mesoscale finite element model material constitutive relations. The method is numerically implemented by writing a user-defined material subroutine in Fortran.
[0015] Preferably, the damage initiation and propagation process under thermal shock load is simulated through thermo-mechanical coupling calculations, specifically including: The material constitutive parameters related to temperature within the grain interior, grain boundaries, coating / substrate interface and in the model are determined by using the mapping method. Cohesive elements are embedded, and thermal shock loads are applied to the coating finite element model to perform thermo-mechanical coupling calculations and simulate the damage evolution process of the coating system.
[0016] Preferably, the typical grain boundary structure includes at least one of (111)-(100), (110)-(111), and (110)-(100) interfaces.
[0017] Preferably, the performance parameters of the material required for the mesoscopic model at temperature T are... , representing the required room temperature reference properties of the material. With the normalized evolution factor extracted from molecular dynamics simulations The product of, i.e. ,in, , These are the performance values at temperature T obtained from molecular dynamics simulations. These are the room temperature performance values obtained from molecular dynamics simulations.
[0018] Preferably, the rough morphology of the coating / substrate interface adopts a periodic function. Perform parametric geometric modeling; Among them, amplitude The wavelength λ is used to control the average roughness Ra; the polycrystalline structure of the coating is generated by the Voronoi mosaic algorithm, and cohesive elements are embedded at the grain interfaces and coating-matrix interfaces to simulate damage.
[0019] Preferably, the thermo-mechanical coupling calculation adopts a sequential coupling method, first calculating the transient temperature field during the thermal shock process, and then using the temperature field as a predefined field for stress and damage analysis.
[0020] Preferably, the microstructure parameters specifically include interface roughness, grain size, coating thickness, and initial bonding strength.
[0021] Preferably, the determined design criteria include at least one of the following: The optimal range for the interface roughness Ra is 1.6 μm to 20 μm; The optimal range for coating grain size d is 5 μm to 20 μm; The coating thickness t should be greater than 10 μm; The initial interfacial bonding strength σ0 should not be less than 10 MPa; It is recommended that the thermal shock temperature of the coating during service should not exceed 1350℃.
[0022] Therefore, the present invention employs the above-mentioned method for cross-scale simulation of thermal shock damage to SiC coatings, and the technical effects are as follows: (1) Mechanism-driven cross-scale prediction was achieved: the atomic mechanism of high-temperature “thermal weakening” of grain boundaries was revealed through molecular dynamics, and its physical effects were introduced into the mesoscopic damage model through parameter mapping, overcoming the limitations of single-scale simulation.
[0023] (2) A refined mesoscopic structure model was established: a model containing rough interfaces and real polycrystalline morphology was constructed by parametric method, which can more realistically reflect the microstructure characteristics of the coating and its influence on thermal stress distribution and crack path.
[0024] (3) Provides quantitative design optimization tools: Through systematic parameterization research, the influence of each microstructure parameter on the thermal shock resistance of the coating (often non-monotonic) is clarified, and specific optimization ranges are extracted, providing direct theoretical basis and data support for the rational design and process control of high-performance coatings. Attached Figure Description
[0025] Figure 1 This is a schematic diagram of the molecular dynamics model of a single SiC crystal and a single crystal containing pre-existing cracks, based on the SiC coating thermal shock damage multi-scale simulation method of the present invention. Figure 1 (a) is a schematic diagram of the molecular dynamics model of SiC single crystal; Figure 1 (b) is a schematic diagram of the molecular dynamics model of a single crystal of SiC containing pre-existing cracks; Figure 2 This is a schematic diagram of the atomic configuration of three typical bicrystalline interfaces of SiC, based on a cross-scale simulation method for thermal shock damage of SiC coatings according to the present invention. Figure 2 (a) is a schematic diagram of the atomic configuration of a low-energy coherent interface; Figure 2 (b) is a schematic diagram of the atomic configuration of a medium-energy interface; Figure 2 (c) is a schematic diagram of the atomic configuration of common high-energy interfaces; Figure 3 Stress-strain curves of SiC single crystals at different temperatures are provided by the present invention for a cross-scale simulation method of thermal shock damage to SiC coatings. Figure 4 Stress-strain curves of three grain boundaries at different temperatures are presented in this invention's method for multi-scale simulation of thermal shock damage to SiC coatings. Figure 4 (a) shows the stress-strain curves of the low-energy coherent interface at different temperatures; Figure 4 (b) shows the stress-strain curves of a medium-energy interface at different temperatures; Figure 4 (c) shows the stress-strain curves of common high-energy interfaces at different temperatures; Figure 5 The evolution curves of normalized fracture energy of SiC single crystal and different grain boundaries with temperature are provided for the cross-scale simulation method of thermal shock damage of SiC coating according to the present invention. Figure 6 The evolution curves of normalized tensile strength of SiC single crystal and different grain boundaries as a function of temperature are provided for the cross-scale simulation method of thermal shock damage of SiC coating according to the present invention. Figure 7 This is a comparison of thermal shock damage morphology of SiC coatings under different interface roughnesses using a cross-scale simulation method for thermal shock damage of SiC coatings according to the present invention. Figure 7 (a) Comparison of thermal shock damage morphology of coatings with an interface roughness of 30.5 μm; Figure 7 (b) is a comparison of the thermal shock damage morphology of the coating when the interface roughness is 13.28 μm; Figure 7 (c) is a comparison of the thermal shock damage morphology of the coating when the interface roughness is 6.64 μm; Figure 7 (d) is a comparison of the thermal shock damage morphology of the coating when the interface roughness is 3.32 μm; Figure 7 (e) is a comparison of the thermal shock damage morphology of the coating when the interface roughness is 1.66 μm; Figure 7 (f) is a comparison of the thermal shock damage morphology of the coating when the interface roughness is 0 μm; Figure 8 This is a comparison of thermal shock damage morphology of SiC coatings under different grain sizes using a cross-scale simulation method for thermal shock damage of SiC coatings according to the present invention. Figure 8 (a) Comparison of thermal shock damage morphology of coatings with a grain size of 0.05 μm; Figure 8 (b) is a comparison of the thermal shock damage morphology of the coating when the grain size is 0.1 μm; Figure 8 (c) is a comparison of the thermal shock damage morphology of the coating when the grain size is 0.5 μm; Figure 8 (d) is a comparison of the thermal shock damage morphology of the coating when the grain size is 1 μm; Figure 8 (e) is a comparison of the thermal shock damage morphology of the coating when the grain size is 5 μm; Figure 8 (f) is a comparison of the thermal shock damage morphology of the coating when the grain size is 10 μm; Figure 8 (g) is a comparison of the thermal shock damage morphology of the coating when the grain size is 20 μm; Figure 8(h) is a comparison of the thermal shock damage morphology of the coating when the grain size is 30 μm; Figure 8 (i) Comparison of thermal shock damage morphology of coatings with a grain size of 50 μm; Figure 9 This is a comparison of thermal shock damage morphology under different coating thicknesses using a cross-scale simulation method for thermal shock damage of SiC coatings according to the present invention. Figure 9 (a) Comparison of thermal shock damage morphology when the coating thickness is 100 μm; Figure 9 (b) Comparison of thermal shock damage morphology when the coating thickness is 70 μm; Figure 9 (c) is a comparison of thermal shock damage morphology when the coating thickness is 40 μm; Figure 9 (d) is a comparison of thermal shock damage morphology when the coating thickness is 20 μm; Figure 9 (e) is a comparison of thermal shock damage morphology when the coating thickness is 10 μm; Figure 10 This is a comparison of thermal shock damage morphology under different initial bonding strengths in a cross-scale simulation method for thermal shock damage of SiC coatings according to the present invention. Figure 10 (a) Comparison of thermal shock damage morphology when the initial bond strength is 1 MPa; Figure 10 (b) Comparison of thermal shock damage morphology when the initial bond strength is 6 MPa; Figure 10 (c) Comparison of thermal shock damage morphology when the initial bond strength is 10 MPa; Figure 10 (d) is a comparison of thermal shock damage morphology when the initial bond strength is 15 MPa; Figure 10 (e) is a comparison of thermal shock damage morphology when the initial bond strength is 20 MPa; Figure 11 This is a comparison of coating damage morphology at different thermal shock temperatures using a cross-scale simulation method for thermal shock damage of SiC coatings according to the present invention. Figure 11 (a) Comparison of coating damage morphology at a thermal shock temperature of 1200℃; Figure 11 (b) Comparison of coating damage morphology at a thermal shock temperature of 1300℃; Figure 11 (c) is a comparison of coating damage morphology at a thermal shock temperature of 1400℃; Figure 11 (d) is a comparison of coating damage morphology at a thermal shock temperature of 1500℃; Figure 11 (e) is a comparison of coating damage morphology at a thermal shock temperature of 1600℃; Figure 12 The curves show the influence of various process parameters on the adhesion strength retention rate of the SiC coating after thermal shock, according to the present invention's method for multi-scale simulation of thermal shock damage. Figure 12 (a) is the curve showing the effect of interface undulation scale on the coating adhesion strength retention rate; Figure 12(b) is the curve showing the effect of grain size on the coating adhesion strength retention rate; Figure 12 (c) is the curve showing the effect of coating thickness on the coating bond strength retention rate; Figure 12 (d) is the curve showing the effect of initial bonding strength on the coating bonding strength retention rate; Figure 12 (e) is the curve showing the effect of thermal shock temperature on the coating bond strength retention rate. Detailed Implementation
[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.
[0027] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.
[0028] Example 1 A method for multi-scale simulation of thermal shock damage to SiC coatings includes the following steps: Step 1: Obtaining the evolution law of atomic-scale performance: In this step, such as Figure 1 and Figure 2 As shown, a 3C-SiC single-crystal model with pre-cracks and three representative symmetric tilted bicrystalline models were constructed: (111)-(100) interface (low-energy coherent interface), (110)-(111) interface (medium-energy interface), and (110)-(100) interface (high-energy common interface). The Tersoff potential function was used to describe the interatomic interactions. The simulation was performed in the LAMMPS environment. First, energy minimization was performed, and then the system was relaxed to equilibrium at temperatures of 300K, 600K, 900K, 1200K, 1500K, and 1900K under the NPT ensemble. For each equilibrium system, uniaxial tension was applied along the
[010] direction under the NVT ensemble, with a strain rate set to 1×10⁻⁶. 9 s -1 Record the stress-strain curves of each model until fracture.
[0029] Figure 3 The stress-strain curves of SiC single crystals at different temperatures are shown. Figure 4 Stress-strain curves for three types of grain boundaries at different temperatures are presented. The ultimate tensile strength at each temperature is extracted from the stress-strain curves. The fracture energy is estimated by calculating the area under the stress-strain curve. The retention rates (i.e., normalized strength and normalized fracture energy) of the strength and fracture energy of single crystals and various grain boundaries relative to their 300K strength and fracture energy are calculated. The data on the retention rates versus temperature are nonlinearly fitted to obtain functions describing the evolution of the strength and fracture energy of single crystals and various grain boundaries with temperature. Figure 5The curves show the evolution of normalized fracture energy as a function of temperature for SiC single crystals and different grain boundaries. Figure 6 The curves show the evolution of normalized tensile strength as a function of temperature for SiC single crystal and different grain boundaries. The results show that the grain boundary strength decays at a significantly faster rate than that of the single crystal.
[0030] Step 2: Establishing a cross-scale parameter mapping model: The normalized strength / normalized fracture energy-temperature evolution function obtained from atomic-scale simulations is used as the temperature dependence of material properties in the mesoscopic finite element model. Specifically, when defining material properties in the finite element software (Abaqus), the material strength or fracture energy at room temperature (which can be obtained experimentally) is multiplied by the corresponding normalized evolution function obtained from the atomic-scale simulation, thus obtaining the temperature-dependent constitutive parameters of the material. This process is implemented using a user-defined material subroutine (VUMAT) written in Fortran.
[0031] Step 3: Construction and simulation of mesoscale thermo-mechanical coupled damage model: The construction and simulation of mesoscale thermo-mechanical coupling damage models include the following steps: (1) Geometric modeling: A two-dimensional plane strain model was established in the finite element software Abaqus. The matrix surface was modeled using a sinusoidal function. Describe its roughness, where, x These are the position coordinates along the horizontal direction of the interface. y ( x () represents the height of the interface outline corresponding to that location. A The amplitude is the value of the interface undulation, which is positively correlated with the average roughness Ra. The wavelength controls the period of interface fluctuations. y 0 represents the baseline offset, used to adjust the average height of the interface. This is achieved by adjusting the amplitude. Different arithmetic mean roughness Ra are defined (e.g., Ra is set to 0 μm (ideal smooth), 1.66 μm, 3.32 μm, 6.64 μm, 13.28 μm, and 30.5 μm). The coating thickness is set to 70 μm. To account for polycrystalline structures, polygons representing different grains are generated within the coating area using a Voronoi tessellation algorithm called via a Python script, with the average grain size set to 10 μm.
[0032] (2) Material Definition and Mesh Generation: The matrix is defined as a linear elastic material. The coating material is divided into grain interior and grain boundaries: the properties of the grain interior are obtained by atomic-scale simulation mapping of the single-crystal performance evolution law; zero-thickness cohesive elements (such as COH2D4) are inserted at all grain interfaces and the coating-matrix physical interface, and their constitutive parameters (such as strength and fracture energy) are obtained by atomic-scale simulation mapping of the corresponding grain boundary performance evolution law. The damage behavior is described by the bilinear traction force-separation criterion. Damage initiation adopts the secondary stress criterion, and its mathematical expression is as follows: ; in, t n , t s , t t These are the normal traction force, the first tangential traction force, and the second tangential traction force, respectively. N Normal intensity S The tangential intensity is used. Damage evolution is based on the energy criterion (BK criterion) under mixed-mode loading. The core formula of the BK criterion is: ; in, Normal fracture energy, The tangential fracture energy, This represents the energy dissipation value in the shear direction. This represents the total energy dissipation value. The correlation coefficient for the BK criterion, determined through mixed-mode experiments, reflects the influence of the shear mode on damage propagation; a typical value is 1-5. Mesh convergence analysis is performed to determine a suitable global mesh size (e.g., 0.1 μm).
[0033] (3) Loading and Solution: The simulation depicts the coating undergoing a rapid temperature rise from room temperature (25℃) to 1300℃ followed by a cooling process (i.e., thermal shock). First, a transient heat conduction analysis is performed to calculate the temperature field distribution. In the mesoscale thermal shock simulation, the transient temperature field is obtained by solving the heat conduction equation. The mathematical expression of the heat conduction equation is as follows: ; in, For density, c For specific heat capacity, Thermal conductivity, T For temperature, t Let time be the time factor. Then, the temperature field is imported as a predefined field into the static analysis step, and the displacement of the bottom edge of the model is constrained to calculate the thermal stress and damage caused by thermal expansion mismatch. The thermal strain caused by the temperature field is: ; in, The coefficient of thermal expansion is... The temperature difference is considered. The assignment is submitted for thermo-mechanical sequential coupling analysis. During the calculation, the cohesive elements determine whether damage initiation and propagation occur based on the defined damage criteria.
[0034] Step 4: Parameter Influence Analysis and Criterion Extraction With other parameters fixed, the interface roughness Ra, grain size d, coating thickness t, initial bonding strength σ0, and thermal shock temperature T are changed systematically. max Repeat step 3 to perform the simulation. The strength retention rate is defined as "remaining interfacial bond strength after thermal shock / initial bond strength". .
[0035] Interface roughness Ra: such as Figure 7 and Figure 12 As shown, the simulation found The coating first increases and then decreases with Ra, and the retention rate is the highest (>95%) in the Ra=1.6-20μm range, with Ra=6.64μm being the optimal value. Excessive smoothness (Ra=0) easily leads to internal cracking of the coating, while excessive roughness (Ra=30.5μm) causes stress concentration and delamination at the interface.
[0036] Grain size d: such as Figure 8 and Figure 12 As shown, The optimal range for d is 5-20 μm, with the grain boundary density increasing first and then decreasing. When d < 1 μm, the excessively high grain boundary density becomes the main cause of weakening; when d > 30 μm, the coarse grains make the cracks prone to unstable propagation.
[0037] Coating thickness t: such as Figure 9 and Figure 12 As shown, It increases with increasing t, but when t < 10 μm, A sharp drop to below 40% results in catastrophic interface stripping. Therefore, 10 μm was determined as the safe design threshold.
[0038] Initial bonding strength σ0: as Figure 10 and Figure 12 As shown, there is a significant threshold effect; the interface is highly susceptible to failure when σ0 < 6 MPa; and when σ0 ≥ 10 MPa, It can be maintained at a high level of over 95%.
[0039] Thermal shock temperature T max :like Figure 11 and Figure 12 As shown, T max At ≤1350℃, It can be maintained above 90%; above 1500℃, Rapid deterioration.
[0040] Based on the above analysis, the following quantitative design guidelines are established: the recommended range for interface roughness is 1.6-20μm, the recommended range for grain size is 5-20μm, the recommended coating thickness is 70μm, with 10μm as the failure threshold, the recommended initial bonding strength is 10MPa, and not less than 5MPa, and the recommended service temperature is controlled below 1350°C, with a maximum of 1500°C.
[0041] Therefore, this invention employs the aforementioned cross-scale simulation method for thermal shock damage of SiC coatings, realizing cross-scale physical correlations from atomic-scale mechanisms to mesoscale morphology to macroscale failures. This enables more accurate prediction of the thermal shock failure behavior of SiC coatings, providing theoretical tools for coating performance evaluation and microstructure design.
[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A method for multi-scale simulation of thermal shock damage to SiC coatings, characterized in that, Includes the following steps: The evolution function of the mechanical properties of SiC single crystals and grain boundaries with temperature was obtained through molecular dynamics simulations. A cross-scale parameter mapping model is established based on the evolution function, which transforms the intrinsic property laws at the atomic scale into temperature-dependent constitutive relations in the mesoscopic finite element model. A finite element model of the coating system, including parameterized interface roughness and polycrystalline structure, was constructed. The damage initiation and propagation process under thermal shock load was simulated by thermo-mechanical coupling calculation. The effects of microstructure parameters and thermal shock temperature on the thermal shock resistance of the coating were evaluated. Based on the evaluation results, the optimization range of each parameter is determined, and a quantitative design criterion for coating thermal shock resistance is formed.
2. The method for multi-scale simulation of thermal shock damage to SiC coatings according to claim 1, characterized in that, The evolution of the mechanical properties of SiC single crystals and grain boundaries with temperature was obtained through molecular dynamics simulations, specifically including: A SiC single crystal and a SiC bicrystal model containing grains, typical grain boundaries, and pre-cracks were constructed. The Tersoff potential function was used to describe the interatomic interactions. Tensile simulations were performed in the temperature range of 300K to 1900K to obtain the intrinsic mechanical properties of silicon carbide single crystal and at least one typical grain boundary structure at different temperatures, and the evolution function of the performance parameters with temperature was established.
3. The method for multi-scale simulation of thermal shock damage to SiC coatings according to claim 1, characterized in that, A cross-scale parameter mapping model is established based on the evolution function, transforming the intrinsic property laws at the atomic scale into temperature-dependent constitutive relations in the mesoscopic finite element model. Specifically, this includes: Based on the obtained evolution function, a cross-scale parameter mapping method is established to map atomic-scale intrinsic property parameters to mesoscale finite element model material constitutive relations. The method is numerically implemented by writing a user-defined material subroutine in Fortran.
4. The method for multi-scale simulation of thermal shock damage to SiC coatings according to claim 1, characterized in that, The damage initiation and propagation process under thermal shock load is simulated through thermo-mechanical coupling calculations, specifically including: The material constitutive parameters related to temperature within the grain interior, grain boundaries, coating / substrate interface and in the model are determined by using the mapping method. Cohesive elements are embedded, and thermal shock loads are applied to the coating finite element model to perform thermo-mechanical coupling calculations and simulate the damage evolution process of the coating system.
5. The method for multi-scale simulation of thermal shock damage to SiC coatings according to claim 2, characterized in that, Typical grain boundary structures include at least one of the (111)-(100), (110)-(111), and (110)-(100) interfaces.
6. The method for multi-scale simulation of thermal shock damage to SiC coatings according to claim 3, characterized in that, The performance parameters of the materials required for the mesoscopic model at temperature T. , representing the required room temperature reference properties of the material. With the normalized evolution factor extracted from molecular dynamics simulations The product of, i.e. ,in, , These are the performance values at temperature T obtained from molecular dynamics simulations. These are the room temperature performance values obtained from molecular dynamics simulations.
7. The method for multi-scale simulation of thermal shock damage to SiC coatings according to claim 4, characterized in that, The rough morphology of the coating / substrate interface is adopted using a periodic function. Perform parametric geometric modeling; Among them, amplitude The wavelength λ is used to control the average roughness Ra; the polycrystalline structure of the coating is generated by the Voronoi mosaic algorithm, and cohesive elements are embedded at the grain interfaces and coating-matrix interfaces to simulate damage.
8. The method for multi-scale simulation of thermal shock damage to SiC coatings according to claim 4, characterized in that, The thermo-mechanical coupling calculation adopts a sequential coupling method, first calculating the transient temperature field during the thermal shock process, and then using the temperature field as a predefined field for stress and damage analysis.
9. The method for multi-scale simulation of thermal shock damage to SiC coatings according to claim 1, characterized in that, Microstructure parameters specifically include interface roughness, grain size, coating thickness, and initial bonding strength.
10. The method for multi-scale simulation of thermal shock damage to SiC coatings according to claim 1, characterized in that, The determined design criteria include at least one of the following: The optimal range for the interface roughness Ra is 1.6 μm to 20 μm; The optimal range for coating grain size d is 5 μm to 20 μm; The coating thickness t should be greater than 10 μm; The initial interfacial bonding strength σ0 should not be less than 10 MPa; It is recommended that the thermal shock temperature of the coating during service should not exceed 1350℃.