Method for predicting ceramic layer deposition crack structure and reversely designing preparation parameters

Abstract

The invention discloses a method for predicting a ceramic layer deposition crack structure and reversely designing preparation parameters. The method comprises the following steps: 1, establishing a heat conduction beam contact model; 2, establishing a thermal barrier coating discrete element model according to a thermal barrier coating sample to be researched; thirdly, micro parameters of a heat conduction beam contact model in the thermal barrier coating discrete element model are calibrated through the macro parameters of the thermal barrier coating sample; 4, performing discrete element simulation on ceramic layers in the thermal barrier coating discrete element model layer by layer; 5, analyzing the crack structure chart to obtain a crack mode; 6, establishing a preparation parameter and crack mode correlation database; and 7, reversely designing the preparation parameters according to the established preparation parameter and crack mode correlation database. According to the thermal barrier coating discrete element model, layer-by-layer discrete element simulation is conducted on the basis of a heat conduction beam contact model so as to predict a crack structure in the layer-by-layer thermal deposition process of a ceramic layer, and screening is conveniently conducted from a correlation database according to actual preparation requirements so as to reversely design preparation parameters.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic layer preparation in thermal barrier coatings, and in particular relates to a method for predicting a ceramic layer deposition crack structure and reversely designing preparation parameters. Background Art

[0002] Gas turbines are one of the core power equipment of clean and efficient thermal power energy systems. The working environment of gas turbine blades is harsh. Thermal barrier coatings are mainly used for high-pressure turbine blades. They not only have a thermal barrier effect, but also prevent damage to the blades caused by oxidation, corrosion, and foreign matter erosion. In order to improve the long-term service of thermal barrier coating materials, thermal barrier coatings with longitudinal crack structures have begun to emerge. The presence of longitudinal cracks can increase the interface fracture resistance of the coating, thereby extending its service life. Therefore, it is crucial to predict the crack structure during the layer-by-layer thermal deposition of the ceramic layer.

[0003] The formation of cracks during the thermal deposition of ceramic layers layer by layer is difficult to obtain through analytical methods. Currently, scanning electron microscopy is often used to observe cracks in the ceramic layer after deposition, but it cannot capture cracks during the layer-by-layer deposition process. In addition, the numerical simulation technology based on the continuum mechanics method to simulate crack initiation and propagation shows certain limitations.

[0004] Therefore, a method for reasonably designing the prediction of the deposition crack structure of the ceramic layer and reverse designing the preparation parameters is needed. The discrete unit simulation under the action of thermal force is realized by constructing the thermal conductive beam contact model, so that the discrete element model of the thermal barrier coating is simulated layer by layer based on the thermal conductive beam contact model, and the crack structure diagram of the ceramic layer layer by layer discrete element simulation is obtained, so as to realize the prediction of the crack structure of the ceramic layer during the layer-by-layer thermal deposition process, and quickly establish a correlation database of single-pass thickness, deposition temperature difference, intra-layer strength of ceramic layers, and inter-layer strength of ceramic layers and their corresponding crack structure diagrams and crack patterns, and facilitate screening from the correlation database according to actual preparation requirements to reversely design preparation parameters and save preparation costs. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for predicting the deposition crack structure of a ceramic layer and reversely designing preparation parameters in view of the deficiencies in the above-mentioned prior art. The method has simple steps and reasonable design. By constructing a thermal beam contact model, discrete unit simulation under thermal action is realized, so that the discrete element model of the thermal barrier coating is simulated layer by layer by discrete element based on the thermal beam contact model, and a crack structure diagram of the ceramic layer layer by layer discrete element simulation is obtained, so that the crack structure of the ceramic layer in the layer-by-layer thermal deposition process can be predicted, and a correlation database of single-pass thickness, deposition temperature difference, intra-layer strength of ceramic layers and inter-layer strength of ceramic layers and their corresponding crack structure diagrams and crack patterns can be quickly established, and it is convenient to screen from the correlation database according to actual preparation requirements to reversely design preparation parameters, thereby saving preparation costs.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for predicting the deposition crack structure of a ceramic layer and reversely designing preparation parameters, the method comprising the following steps: Step 1: Establish the thermal beam contact model: Setting up discrete elements connected by thermal beams and discrete units , discrete unit The initial temperature is , discrete unit The initial temperature is , establish a thermal beam contact model; wherein the thermal beam contact model is an Euler Bernoulli beam analytical model, and the relaxation length of the thermal beam in the thermal beam contact model for ;in, represents the microscopic thermal expansion coefficient, Represents discrete units The temperature change, Represents discrete units The temperature change, Represents discrete units and discrete units the initial distance between centers; Step 2: Establish a discrete element model of thermal barrier coating according to the thermal barrier coating sample to be studied; Step 3, calibrating the microscopic parameters of the thermal beam contact model in the thermal barrier coating discrete element model through the macroscopic parameters of the thermal barrier coating sample; Step 4: Perform discrete element simulation of the ceramic layer in the discrete element model of the thermal barrier coating layer by layer: The calibrated microscopic parameters are input into the thermal beam contact model corresponding to the discrete element model of the thermal barrier coating, and different single-pass thicknesses, deposition temperature differences, ceramic layer intra-layer strengths, and ceramic layer inter-layer strengths are set. The ceramic layer in the discrete element model of the thermal barrier coating is simulated layer by layer by discrete element, and the crack structure diagram of the ceramic layer is obtained by the discrete element simulation of the ceramic layer layer by layer; Step 5: Analyze the crack structure diagram to obtain the crack mode; Step 6: Establish a database of correlation between preparation parameters and crack patterns: Establish a correlation database of single-pass thickness, deposition temperature difference, ceramic layer intra-layer strength and ceramic layer inter-layer strength preparation parameters and their corresponding crack structure diagrams and crack patterns; Step 7: Reverse design the preparation parameters based on the established preparation parameter and crack mode correlation database: The crack pattern required for preparation is screened from the correlation database established in step six, and the single-pass thickness, deposition temperature difference, intra-layer strength of the ceramic layer and inter-layer strength of the ceramic layer corresponding to the crack pattern required for preparation are used as reverse design preparation parameters.

[0007] The above method for predicting the deposition crack structure of a ceramic layer and reverse designing the preparation parameters, further, the thermal beam contact model in step 1, also includes the following: ; in, Indicates that the heat transfer beam acts on the discrete unit The force on Indicates that the heat transfer beam acts on the discrete unit The force on Indicates that the heat transfer beam acts on the discrete element The torque, Indicates that the heat transfer beam acts on the discrete element The torque, represents the cross-sectional area of ​​the heat conducting beam, represents the microscopic Young's modulus, Indicates the longitudinal extension length of the thermal beam, represents the relaxation length of the thermal beam, Respectively represent the relative discrete units of the center line of the heat conducting beam The rotation amount is the X-axis component, Y-axis component, and Z-axis component in the local coordinate system of the beam; Respectively represent the relative discrete units of the center line of the heat conducting beam The rotation amount is the X-axis component, Y-axis component, and Z-axis component in the local coordinate system of the beam; They represent the X-axis direction, Y-axis direction, and Z-axis direction of the beam local coordinate system respectively; represents the micro shear modulus, represents the polar moment of inertia, Represents the moment of inertia along the Y-axis or Z-axis direction, represents the cross-sectional radius of the heat conducting beam, Represents pi.

[0008] The above-mentioned method for predicting the deposition crack structure of a ceramic layer and reversely designing preparation parameters, further, the thermal barrier coating discrete element model in step 2 includes a substrate discrete element model, a bonding layer discrete element model and a ceramic layer discrete element model, the substrate discrete element model, the bonding layer discrete element model and the ceramic layer discrete element model all satisfy the random close packing condition, and the ceramic layer discrete element model includes a first deposited ceramic layer, a second deposited ceramic layer, ..., an nth deposited ceramic layer, ..., an Nth deposited ceramic layer; wherein n and N are both positive integers, and 1≤n≤N; The crack modes described in step five include a longitudinal crack mode, a mixed crack mode in which longitudinal cracks and transverse cracks coexist, a transverse crack mode, and a crack-free mode.

[0009] The above method for predicting the deposition crack structure of a ceramic layer and reversely designing preparation parameters, further, before step 3, first obtains the relationship between the macroscopic parameters and the microscopic parameters of the thermal beam contact model, the specific process is as follows: Step A, using a computer to establish a cylindrical discrete element model; wherein the cylindrical discrete element model satisfies the random close packing condition, and the initial length of the cylindrical discrete element model is , the initial radius of the cylindrical discrete element model is ; Step B: Use computer to , calculate the dimensionless cross-sectional radius ;in, Represents the average radius of all discrete elements in the cylindrical discrete element model; dimensionless cross-sectional radius The value range of is 0.1~1.0; Step C: Use computer settings The value is 0.1, the microscopic Young's modulus The value is set to 0, and the cylindrical discrete element model is input to simulate the uniaxial tensile test, and the result is The stretched length of the cylindrical discrete element model under the microscopic Young's modulus is 0.1 , the stretched radius of the cylindrical discrete element model and the forces at both ends of the cylindrical discrete element model ; and according to the formula and , and the macroscopic Young's modulus under the microscopic Young's modulus is obtained and macroscopic Poisson's ratio ; Step D: Repeat step C multiple times, gradually increasing the microscopic Young's modulus by 100 GPa , until the microscopic Young's modulus The value of is 1000GPa, and we get The macroscopic Young's modulus and macroscopic Poisson's ratio under different microscopic Young's moduli when is 0.1; Step E, repeating steps C and D multiple times, gradually increasing the dimensionless cross-sectional radius according to a step size of 0.1 until the dimensionless cross-sectional radius takes a value of 1.0, thereby obtaining a linear fitting relationship between the microscopic Young's modulus and the macroscopic Young's modulus under different dimensionless cross-sectional radii and a macroscopic Poisson's ratio under different dimensionless cross-sectional radii; Step F: Setting the micro thermal conductivity using a computer The value is 0, and a one-dimensional numerical heat conduction simulation is performed on the cylindrical discrete element model. According to the analytical solution of one-dimensional heat conduction, the macroscopic thermal conductivity is obtained. ; Step G: Repeat step F multiple times, according to the step length Gradually increase the micro thermal conductivity until the micro thermal conductivity The value is , the linear fitting relationship between micro thermal conductivity and macro thermal conductivity is obtained; Step H: using a computer to establish a cube discrete element model, perform numerical thermal expansion simulation, and obtain a linear fitting relationship between the microscopic thermal expansion coefficient and the macroscopic thermal expansion coefficient.

[0010] The above method for predicting the deposition crack structure of a ceramic layer and reverse designing the preparation parameters further includes step three, and the specific process is as follows: Step 301, linearly interpolating the macroscopic Poisson's ratio under different dimensionless cross-sectional radii in step E to obtain the dimensionless cross-sectional radius corresponding to the ceramic layer; and according to the method of step B, obtaining the cross-sectional radius of the heat-conducting beam corresponding to the ceramic layer; Step 302: According to the linear fitting relationship between the microscopic Young's modulus and the macroscopic Young's modulus at different dimensionless cross-sectional radii in step E, the macroscopic Young's modulus of the ceramic layer and the dimensionless cross-sectional radius corresponding to the ceramic layer in step 301 are input and linearly interpolated to obtain the microscopic Young's modulus of the ceramic layer corresponding to the thermal beam contact model. ; Step 303: According to the linear fitting relationship between the microscopic thermal expansion coefficient and the macroscopic thermal expansion coefficient in step H, the microscopic thermal expansion coefficient of the ceramic layer corresponding to the thermal beam contact model is obtained through the macroscopic thermal expansion coefficient of the ceramic layer; Step 304: according to the linear fitting relationship between the micro thermal conductivity and the macro thermal conductivity in step G, the macro thermal conductivity of the ceramic layer is input to obtain the micro thermal conductivity of the ceramic layer corresponding to the thermal beam contact model; Step 305: Set the microscopic Poisson's ratio of the ceramic layer corresponding to the thermal beam contact model , and according to the formula , the micro shear modulus of the ceramic layer corresponding to the thermal beam contact model is obtained ; Step 306: When the dimensionless cross-sectional radius corresponding to the ceramic layer and the microscopic Young's modulus of the thermal beam contact model corresponding to the ceramic layer are known, the microscopic fracture strength is set to 0 by a computer, and a uniaxial tensile test simulation is performed on the cylindrical discrete element model to obtain the fracture strength when the cylindrical discrete element model is destroyed, which is recorded as the macroscopic strength; Step 307, repeating step 306 multiple times, gradually increasing the microscopic fracture strength with a step length of 1 GPa, until the value of the microscopic fracture strength is 5 GPa, and obtaining a linear fitting relationship between the microscopic fracture strength and the macroscopic strength; Step 308, according to the linear fitting relationship between microscopic fracture strength and macroscopic strength, the ceramic layer intra-layer strength is input to obtain the microscopic fracture strength in the ceramic layer; Step 309, according to the method of step 308, the microscopic fracture strength between the ceramic layers is obtained according to the interlayer strength of the ceramic layers; Step 30A, according to the method of step 301 to step 305, according to the macroscopic Young's modulus, macroscopic Poisson's ratio, macroscopic thermal expansion coefficient and macroscopic thermal conductivity of the bonding layer, the cross-sectional radius of the thermal beam, the microscopic Young's modulus, the microscopic shear modulus, the microscopic thermal expansion coefficient and the microscopic thermal conductivity of the thermal beam contact model corresponding to the bonding layer are obtained; Step 30B, according to the method of steps 301 to 305, based on the macroscopic Young's modulus, macroscopic Poisson's ratio, macroscopic thermal expansion coefficient and macroscopic thermal conductivity of the substrate, obtain the cross-sectional radius of the thermal beam, microscopic Young's modulus, microscopic shear modulus, microscopic thermal expansion coefficient and microscopic thermal conductivity of the thermal beam contact model corresponding to the substrate.

[0011] The above method for predicting the deposition crack structure of a ceramic layer and reverse designing the preparation parameters further includes step 4, and the specific process is as follows: Step 401, using a computer to assign the cross-sectional radius of the heat-conducting beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient and micro thermal conductivity of the heat-conducting beam contact model corresponding to the substrate to the discrete element model of the substrate, assign the cross-sectional radius of the heat-conducting beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient and micro thermal conductivity of the heat-conducting beam contact model corresponding to the bonding layer to the discrete element model of the bonding layer, assign the cross-sectional radius of the heat-conducting beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength in the ceramic layer corresponding to the heat-conducting beam contact model to the first deposited ceramic layer; the micro thermal conductivity of other deposited ceramic layers is set to zero; Step 402, using a computer to set the thickness of the first deposited ceramic layer, the deposition temperature difference, the bottom of the substrate discrete element model and the environment with a temperature of Tc to perform convective heat transfer under a heat transfer coefficient hc, and the top of the first deposited ceramic layer and the spraying environment with a temperature of Ts to perform convective heat transfer under a heat transfer coefficient hs, then the substrate discrete element model, the bonding layer discrete element model and the first deposited ceramic layer are discrete element simulated based on their respective thermal beam contact models, and the crack structure of the first deposited ceramic layer is obtained; wherein the thickness of the first deposited ceramic layer is a single-pass thickness; Step 403, after the discrete element simulation of the first deposited ceramic layer is completed, the cross-sectional radius of the thermal beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength in the ceramic layer corresponding to the thermal beam contact model of the ceramic layer are assigned to the second deposited ceramic layer, the cross-sectional radius of the thermal beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength between ceramic layers corresponding to the thermal beam contact model of the ceramic layer are assigned to the thermal beam contact model between the first deposited ceramic layer and the second deposited ceramic layer, and the micro thermal conductivity of other deposited ceramic layers is set to zero; Step 404, using a computer to set the thickness of the second deposited ceramic layer, the deposition temperature difference, the bottom of the substrate discrete element model and the environment with a temperature of Tc to perform convective heat exchange at a heat transfer coefficient of hc, and the top of the second deposited ceramic layer and the spraying environment with a temperature of Ts to perform convective heat exchange at a heat transfer coefficient of hs, and perform discrete element simulation according to the method of step 402 to obtain the crack structure of the first deposited ceramic layer and the second deposited ceramic layer; wherein the thickness of the second deposited ceramic layer is a single-pass thickness; Step 405, repeating steps 403 and 404 for multiple times, after the discrete element simulation of the nth deposited ceramic layer is completed, the cross-sectional radius of the thermal beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength in the ceramic layer corresponding to the thermal beam contact model of the ceramic layer are assigned to the n+1th deposited ceramic layer, the cross-sectional radius of the thermal beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength between ceramic layers corresponding to the thermal beam contact model of the ceramic layer are assigned to the thermal beam contact model between the nth deposited ceramic layer and the n+1th deposited ceramic layer, and the micro thermal conductivity of other deposited ceramic layers is set to zero; and discrete element simulation is performed according to the method of step 404 to obtain the crack structure of the 1st deposited ceramic layer to the n+1th deposited ceramic layer; wherein n is a positive integer greater than 1; and the thickness of the nth deposited ceramic layer is a single pass thickness; Step 406, repeating step 405 multiple times until the discrete element simulation of the Nth deposited ceramic layer is completed, and a crack structure diagram of the discrete element simulation of the ceramic layer layer by layer is obtained; wherein the thickness of the Nth deposited ceramic layer is a single pass thickness; Step 407, repeat steps 401 to 406 multiple times, change the single pass thickness, deposition temperature difference, ceramic layer intra-layer strength and ceramic layer inter-layer strength, and obtain the crack structure diagram of the ceramic layer layer by layer discrete element simulation under different single pass thickness, deposition temperature difference, ceramic layer intra-layer strength and ceramic layer inter-layer strength.

[0012] Compared with the prior art, the present invention has the following advantages: 1. The method of the present invention has simple steps and reasonable design, and solves the problem that the current continuous medium mechanics method is limited in simulating cracks and the scanning electron microscope experimental method cannot capture cracks in the layer-by-layer deposition process.

[0013] 2. The present invention is based on the discrete element method under thermal action, so as to facilitate the subsequent discretization of the solution space of the discrete element model of the thermal barrier coating into discrete units. The discrete units are connected by thermal beams, and the forces and moments acting on the discrete units are calculated based on the analytical solution of the Euler Bernoulli beam.

[0014] 3. The relaxation length of the thermal beam is set in the thermal beam contact model of the present invention. When considering the initial distance between the centers of the two discrete units, it also changes with the temperature change of the two discrete units, so that the thermal beam contact model can simulate the thermal behavior and mechanical behavior at the same time, and further simulate the crack evolution structure of the thermal barrier coating during the thermal deposition process.

[0015] 4. The present invention establishes a discrete element model of thermal barrier coating and performs layer-by-layer discrete element simulation based on the thermal beam contact model to obtain a crack structure diagram of the ceramic layer by layer discrete element simulation, thereby realizing the prediction of the crack structure of the ceramic layer during the layer-by-layer thermal deposition process, and by changing the preparation parameters of single-pass thickness, deposition temperature difference, intra-layer strength of ceramic layers and inter-layer strength of ceramic layers, a database of correlation between preparation parameters and crack patterns is obtained, so as to facilitate reverse design of preparation parameters according to the established database of correlation between preparation parameters and crack patterns.

[0016] In summary, the method of the present invention has simple steps and reasonable design. By constructing a thermal beam contact model, discrete unit simulation under thermal action is realized, so that the discrete element model of the thermal barrier coating is simulated layer by layer based on the thermal beam contact model, and the crack structure diagram of the ceramic layer layer by layer discrete element simulation is obtained, and the crack structure of the ceramic layer in the layer-by-layer thermal deposition process is predicted. A correlation database of single-pass thickness, deposition temperature difference, ceramic layer intra-layer strength and ceramic layer inter-layer strength and their corresponding crack structure diagrams and crack patterns is quickly established, and it is convenient to screen from the correlation database according to actual preparation requirements to reversely design preparation parameters, thereby saving preparation costs.

[0017] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the initial state of the thermal beam contact model of the present invention.

[0019] Figure 2 This is the deformed state of the thermal beam contact model of the present invention.

[0020] Figure 3 The figure is a flowchart of the method of the present invention.

[0021] Figure 4 This is a diagram of the simulated crack structure when the deposition temperature difference is 100K according to the present invention.

[0022] Figure 5 This is a diagram of the simulated crack structure when the deposition temperature difference is 539K according to the present invention.

[0023] Figure 6 This is a diagram of the simulated crack structure when the deposition temperature difference is 610K according to the present invention. DETAILED DESCRIPTION

[0024] like Figures 1 to 3 As shown, the present invention provides a method for predicting the deposition crack structure of a ceramic layer and reversely designing preparation parameters, comprising the following steps: Step 1: Establish the thermal beam contact model: Setting up discrete elements connected by thermal beams and discrete units , discrete unit The initial temperature is , discrete unit The initial temperature is , establish a thermal beam contact model; wherein the thermal beam contact model is an Euler Bernoulli beam analytical model, and the relaxation length of the thermal beam in the thermal beam contact model for ;in, represents the microscopic thermal expansion coefficient, Represents discrete units The temperature change, Represents discrete units The temperature change, Represents discrete units and discrete units the initial distance between centers; Step 2: Establish a discrete element model of thermal barrier coating according to the thermal barrier coating sample to be studied; Step 3, calibrating the microscopic parameters of the thermal beam contact model in the thermal barrier coating discrete element model through the macroscopic parameters of the thermal barrier coating sample; Step 4: Perform discrete element simulation of the ceramic layer in the discrete element model of the thermal barrier coating layer by layer: The calibrated microscopic parameters are input into the thermal beam contact model corresponding to the discrete element model of the thermal barrier coating, and different single-pass thicknesses, deposition temperature differences, ceramic layer intra-layer strengths, and ceramic layer inter-layer strengths are set. The ceramic layer in the discrete element model of the thermal barrier coating is simulated layer by layer by discrete element, and the crack structure diagram of the ceramic layer is obtained by the discrete element simulation of the ceramic layer layer by layer; Step 5: Analyze the crack structure diagram to obtain the crack mode; Step 6: Establish a database of correlation between preparation parameters and crack patterns: Establish a correlation database of single-pass thickness, deposition temperature difference, ceramic layer intra-layer strength and ceramic layer inter-layer strength preparation parameters and their corresponding crack structure diagrams and crack patterns; Step 7: Reverse design the preparation parameters based on the established preparation parameter and crack mode correlation database: The crack pattern required for preparation is screened from the correlation database established in step six, and the single-pass thickness, deposition temperature difference, intra-layer strength of the ceramic layer and inter-layer strength of the ceramic layer corresponding to the crack pattern required for preparation are used as reverse design preparation parameters.

[0025] In this embodiment, the thermal beam contact model in step 1 further includes the following: ; in, Indicates that the heat transfer beam acts on the discrete unit The force on Indicates that the heat transfer beam acts on the discrete unit The force on Indicates that the heat transfer beam acts on the discrete element The torque, Indicates that the heat transfer beam acts on the discrete element The torque, represents the cross-sectional area of ​​the heat conducting beam, represents the microscopic Young's modulus, Indicates the longitudinal extension length of the thermal beam, represents the relaxation length of the thermal beam, Respectively represent the relative discrete units of the center line of the heat conducting beam The rotation amount is the X-axis component, Y-axis component, and Z-axis component in the local coordinate system of the beam; Respectively represent the relative discrete units of the center line of the heat conducting beam The rotation amount is the X-axis component, Y-axis component, and Z-axis component in the local coordinate system of the beam; They represent the X-axis direction, Y-axis direction, and Z-axis direction of the beam local coordinate system respectively; represents the micro shear modulus, represents the polar moment of inertia, Represents the moment of inertia along the Y-axis or Z-axis direction, represents the cross-sectional radius of the heat conducting beam, Represents pi.

[0026] In this embodiment, the discrete element model of the thermal barrier coating in step 2 includes a substrate discrete element model, a bonding layer discrete element model and a ceramic layer discrete element model, and the substrate discrete element model, the bonding layer discrete element model and the ceramic layer discrete element model all satisfy the random close packing condition, and the ceramic layer discrete element model includes a first deposited ceramic layer, a second deposited ceramic layer, ..., an nth deposited ceramic layer, ..., an Nth deposited ceramic layer; wherein n and N are both positive integers, and 1≤n≤N; The crack modes described in step five include a longitudinal crack mode, a mixed crack mode in which longitudinal cracks and transverse cracks coexist, a transverse crack mode, and a crack-free mode.

[0027] In this embodiment, before step 3, the relationship between the macroscopic parameters and the microscopic parameters of the thermal beam contact model is first obtained, and the specific process is as follows: Step A, using a computer to establish a cylindrical discrete element model; wherein the cylindrical discrete element model satisfies the random close packing condition, and the initial length of the cylindrical discrete element model is , the initial radius of the cylindrical discrete element model is ; Step B: Use computer to , calculate the dimensionless cross-sectional radius ;in, Represents the average radius of all discrete elements in the cylindrical discrete element model; dimensionless cross-sectional radius The value range of is 0.1~1.0; Step C: Use computer settings The value is 0.1, the microscopic Young's modulus The value is set to 0, and the cylindrical discrete element model is input to simulate the uniaxial tensile test, and the result is The stretched length of the cylindrical discrete element model under the microscopic Young's modulus is 0.1 , the stretched radius of the cylindrical discrete element model and the forces at both ends of the cylindrical discrete element model ; and according to the formula and , and the macroscopic Young's modulus under the microscopic Young's modulus is obtained and macroscopic Poisson's ratio ; Step D: Repeat step C multiple times, gradually increasing the microscopic Young's modulus by 100 GPa , until the microscopic Young's modulus The value of is 1000GPa, and we get The macroscopic Young's modulus and macroscopic Poisson's ratio under different microscopic Young's moduli when is 0.1; Step E, repeating steps C and D multiple times, gradually increasing the dimensionless cross-sectional radius according to a step size of 0.1 until the dimensionless cross-sectional radius takes a value of 1.0, thereby obtaining a linear fitting relationship between the microscopic Young's modulus and the macroscopic Young's modulus under different dimensionless cross-sectional radii and a macroscopic Poisson's ratio under different dimensionless cross-sectional radii; Step F: Setting the micro thermal conductivity using a computer The value is 0, and a one-dimensional numerical heat conduction simulation is performed on the cylindrical discrete element model. According to the analytical solution of one-dimensional heat conduction, the macroscopic thermal conductivity is obtained. ; Step G: Repeat step F multiple times, according to the step length Gradually increase the micro thermal conductivity until the micro thermal conductivity The value is , the linear fitting relationship between micro thermal conductivity and macro thermal conductivity is obtained; Step H: using a computer to establish a cube discrete element model, perform numerical thermal expansion simulation, and obtain a linear fitting relationship between the microscopic thermal expansion coefficient and the macroscopic thermal expansion coefficient.

[0028] In this embodiment, step three, the specific process is as follows: Step 301, linearly interpolating the macroscopic Poisson's ratio under different dimensionless cross-sectional radii in step E to obtain the dimensionless cross-sectional radius corresponding to the ceramic layer; and according to the method of step B, obtaining the cross-sectional radius of the heat-conducting beam corresponding to the ceramic layer; Step 302: According to the linear fitting relationship between the microscopic Young's modulus and the macroscopic Young's modulus at different dimensionless cross-sectional radii in step E, the macroscopic Young's modulus of the ceramic layer and the dimensionless cross-sectional radius corresponding to the ceramic layer in step 301 are input and linearly interpolated to obtain the microscopic Young's modulus of the ceramic layer corresponding to the thermal beam contact model. ; Step 303: According to the linear fitting relationship between the microscopic thermal expansion coefficient and the macroscopic thermal expansion coefficient in step H, the microscopic thermal expansion coefficient of the ceramic layer corresponding to the thermal beam contact model is obtained through the macroscopic thermal expansion coefficient of the ceramic layer; Step 304: according to the linear fitting relationship between the micro thermal conductivity and the macro thermal conductivity in step G, the macro thermal conductivity of the ceramic layer is input to obtain the micro thermal conductivity of the ceramic layer corresponding to the thermal beam contact model; Step 305: Set the microscopic Poisson's ratio of the ceramic layer corresponding to the thermal beam contact model , and according to the formula , the micro shear modulus of the ceramic layer corresponding to the thermal beam contact model is obtained ; Step 306: When the dimensionless cross-sectional radius corresponding to the ceramic layer and the microscopic Young's modulus of the thermal beam contact model corresponding to the ceramic layer are known, the microscopic fracture strength is set to 0 by a computer, and a uniaxial tensile test simulation is performed on the cylindrical discrete element model to obtain the fracture strength when the cylindrical discrete element model is destroyed, which is recorded as the macroscopic strength; Step 307, repeating step 306 multiple times, gradually increasing the microscopic fracture strength with a step length of 1 GPa, until the value of the microscopic fracture strength is 5 GPa, and obtaining a linear fitting relationship between the microscopic fracture strength and the macroscopic strength; Step 308, according to the linear fitting relationship between microscopic fracture strength and macroscopic strength, the ceramic layer intra-layer strength is input to obtain the microscopic fracture strength in the ceramic layer; Step 309, according to the method of step 308, the microscopic fracture strength between the ceramic layers is obtained according to the interlayer strength of the ceramic layers; Step 30A, according to the method of step 301 to step 305, according to the macroscopic Young's modulus, macroscopic Poisson's ratio, macroscopic thermal expansion coefficient and macroscopic thermal conductivity of the bonding layer, the cross-sectional radius of the thermal beam, the microscopic Young's modulus, the microscopic shear modulus, the microscopic thermal expansion coefficient and the microscopic thermal conductivity of the thermal beam contact model corresponding to the bonding layer are obtained; Step 30B, according to the method of steps 301 to 305, based on the macroscopic Young's modulus, macroscopic Poisson's ratio, macroscopic thermal expansion coefficient and macroscopic thermal conductivity of the substrate, obtain the cross-sectional radius of the thermal beam, microscopic Young's modulus, microscopic shear modulus, microscopic thermal expansion coefficient and microscopic thermal conductivity of the thermal beam contact model corresponding to the substrate.

[0029] In this embodiment, step 4, the specific process is as follows: Step 401, using a computer to assign the cross-sectional radius of the heat-conducting beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient and micro thermal conductivity of the heat-conducting beam contact model corresponding to the substrate to the discrete element model of the substrate, assign the cross-sectional radius of the heat-conducting beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient and micro thermal conductivity of the heat-conducting beam contact model corresponding to the bonding layer to the discrete element model of the bonding layer, assign the cross-sectional radius of the heat-conducting beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength in the ceramic layer corresponding to the heat-conducting beam contact model to the first deposited ceramic layer; the micro thermal conductivity of other deposited ceramic layers is set to zero; Step 402, using a computer to set the thickness of the first deposited ceramic layer, the deposition temperature difference, the bottom of the substrate discrete element model and the environment with a temperature of Tc to perform convective heat transfer under a heat transfer coefficient hc, and the top of the first deposited ceramic layer and the spraying environment with a temperature of Ts to perform convective heat transfer under a heat transfer coefficient hs, then the substrate discrete element model, the bonding layer discrete element model and the first deposited ceramic layer are discrete element simulated based on their respective thermal beam contact models, and the crack structure of the first deposited ceramic layer is obtained; wherein the thickness of the first deposited ceramic layer is a single-pass thickness; Step 403, after the discrete element simulation of the first deposited ceramic layer is completed, the cross-sectional radius of the thermal beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength in the ceramic layer corresponding to the thermal beam contact model of the ceramic layer are assigned to the second deposited ceramic layer, the cross-sectional radius of the thermal beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength between ceramic layers corresponding to the thermal beam contact model of the ceramic layer are assigned to the thermal beam contact model between the first deposited ceramic layer and the second deposited ceramic layer, and the micro thermal conductivity of other deposited ceramic layers is set to zero; Step 404, using a computer to set the thickness of the second deposited ceramic layer, the deposition temperature difference, the bottom of the substrate discrete element model and the environment with a temperature of Tc to perform convective heat exchange at a heat transfer coefficient of hc, and the top of the second deposited ceramic layer and the spraying environment with a temperature of Ts to perform convective heat exchange at a heat transfer coefficient of hs, and perform discrete element simulation according to the method of step 402 to obtain the crack structure of the first deposited ceramic layer and the second deposited ceramic layer; wherein the thickness of the second deposited ceramic layer is a single-pass thickness; Step 405, repeating steps 403 and 404 for multiple times, after the discrete element simulation of the nth deposited ceramic layer is completed, the cross-sectional radius of the thermal beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength in the ceramic layer corresponding to the thermal beam contact model of the ceramic layer are assigned to the n+1th deposited ceramic layer, the cross-sectional radius of the thermal beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength between ceramic layers corresponding to the thermal beam contact model of the ceramic layer are assigned to the thermal beam contact model between the nth deposited ceramic layer and the n+1th deposited ceramic layer, and the micro thermal conductivity of other deposited ceramic layers is set to zero; and discrete element simulation is performed according to the method of step 404 to obtain the crack structure of the 1st deposited ceramic layer to the n+1th deposited ceramic layer; wherein n is a positive integer greater than 1; and the thickness of the nth deposited ceramic layer is a single pass thickness; Step 406, repeating step 405 multiple times until the discrete element simulation of the Nth deposited ceramic layer is completed, and a crack structure diagram of the discrete element simulation of the ceramic layer layer by layer is obtained; wherein the thickness of the Nth deposited ceramic layer is a single pass thickness; Step 407, repeat steps 401 to 406 multiple times, change the single pass thickness, deposition temperature difference, ceramic layer intra-layer strength and ceramic layer inter-layer strength, and obtain the crack structure diagram of the ceramic layer layer by layer discrete element simulation under different single pass thickness, deposition temperature difference, ceramic layer intra-layer strength and ceramic layer inter-layer strength.

[0030] In this embodiment, further, in the thermal barrier coating sample to be studied, the substrate is a nickel-based high-temperature alloy substrate, the bonding layer is an anti-oxidation bonding layer, and the ceramic layer is a zirconium oxide YSZ ceramic layer; the number of deposition times of the ceramic layer is N. The thickness of the substrate is 2 mm, the thickness of the bonding layer is 0.5 mm, and the thickness of the ceramic layer is 400 μm to 1500 μm.

[0031] In this embodiment, further, a discrete element model of the thermal barrier coating is established by converting the three-dimensional thermal barrier coating sample to be studied into a two-dimensional model, so that the rectangular thermal barrier coating sample is converted into a rectangular discrete element model.

[0032] In this embodiment, further, Figure 1 and Figure 2 The middle heat conducting beam is represented by the middle line, and one end of the heat conducting beam is located at the discrete unit The center of the circle The other end of the thermal beam is located at the discrete unit The center of the circle . Represents the centerline of the heat transfer beam relative to the discrete unit The amount of rotation, Represents the centerline of the heat transfer beam relative to the discrete unit The amount of rotation.

[0033] In this embodiment, further, in the initial state, in the discrete unit The center of the circle Establish axis, Axis and Local reference system of the axis , in discrete units The center of the circle Establish axis, Axis and Local reference system of the axis ; Among them, the local reference system In Axes and Local Reference Frames In The axes are close to each other along the center line of the heat conducting beam; After the heat transfer beam is deformed, the local coordinate system of the beam The origin and center of the circle Coincident, the X-axis along the discrete unit and discrete units Connect the lines and Point to the center , the Y axis is perpendicular to both the X axis and The Z axis is perpendicular to both the X and Y axes.

[0034] In this embodiment, it should be noted that the macroscopic Poisson's ratio Only with related.

[0035] In this embodiment, the macroscopic Young's modulus of the matrix is ​​set to 211 GPa, the macroscopic Poisson's ratio is set to 0.3, and the macroscopic thermal expansion coefficient is set to , the macroscopic thermal conductivity is ; The macroscopic Young's modulus of the bonding layer is set to 183 GPa, the macroscopic Poisson's ratio is set to 0.3, and the macroscopic thermal expansion coefficient is set to , the macroscopic thermal conductivity is ; The macroscopic Young's modulus of the ceramic layer is 20 GPa, the macroscopic Poisson's ratio is 0.22, and the macroscopic thermal expansion coefficient is , the macroscopic thermal conductivity is , the ceramic layer intra-layer strength ranges from 60MPa to 200MPa; the ceramic layer inter-layer strength ranges from 60MPa to 200MPa; The thickness of the first deposited ceramic layer to the thickness of the Nth deposited ceramic layer are all single-pass thicknesses, and the value is 50 μm to 100 μm.

[0036] The deposition temperature difference is the difference between the initial temperature of each deposited ceramic layer and the initial temperature of the substrate, and the deposition temperature difference is 100K to 610K.

[0037] In this embodiment, Tc is 298K, hc is , Ts is 748K, hs is .

[0038] In this embodiment, the micro Poisson's ratio of the ceramic layer corresponding to the thermal beam contact model, the micro Poisson's ratio of the bonding layer corresponding to the thermal beam contact model and the micro Poisson's ratio of the substrate corresponding to the thermal beam contact model are further set to 0.3, and can also be adjusted between 0 and 1 according to design requirements.

[0039] In this embodiment, Figures 4 to 6 , the bottom corresponds to the substrate and bonding layer, and the upper part corresponds to the ceramic layer. Discrete element simulation is performed layer by layer to obtain the simulated crack structure diagram when the intra-layer strength of the ceramic layer is 110MPa, the inter-layer strength of the ceramic layer is 100MPa, and the deposition temperature difference is 100K, 539K and 610K. Figure 4 The middle is the crack-free mode. Figure 5 The middle one is the longitudinal crack mode. Figure 6 It is a mixed crack mode with coexistence of longitudinal cracks and transverse cracks. The cross section of the thermal barrier coating sample was scanned with a scanning electron microscope to obtain the actual crack structure when the deposition temperature difference was 100K, 539K and 610K. The simulated crack structure diagram was compared with the actual crack structure. The crack mode obtained by layer-by-layer discrete element simulation was consistent with the actual crack mode.

[0040] In this embodiment, discrete element simulation is performed layer by layer under a deposition temperature difference of 100K, with the intra-layer strength and inter-layer strength of the ceramic layers changed and the value range of 60MPa to 200MPa to obtain various crack structure diagrams.

[0041] In this embodiment, further, the method is also applicable to other coatings prepared by thermal deposition methods, such as SiO 2 Coating, Cr 2 O 3 Coatings, enamel coatings and environmental barrier coatings (EBC).

[0042] In summary, the method of the present invention has simple steps and reasonable design. By constructing a thermal beam contact model, discrete unit simulation under thermal action is realized, so that the discrete element model of the thermal barrier coating is simulated layer by layer based on the thermal beam contact model, and the crack structure diagram of the ceramic layer layer by layer discrete element simulation is obtained, and the crack structure of the ceramic layer in the layer-by-layer thermal deposition process is predicted. A correlation database of single-pass thickness, deposition temperature difference, ceramic layer intra-layer strength and ceramic layer inter-layer strength and their corresponding crack structure diagrams and crack patterns is quickly established, and it is convenient to screen from the correlation database according to actual preparation requirements to reversely design preparation parameters, thereby saving preparation costs.

[0043] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for predicting the deposition crack structure of a ceramic layer and reverse designing preparation parameters, characterized in that: The method comprises the following steps: Step 1: Establish the thermal beam contact model: Setting up discrete elements connected by thermal beams and discrete units , discrete unit The initial temperature is , discrete unit The initial temperature is , establish a thermal beam contact model; wherein the thermal beam contact model is an Euler Bernoulli beam analytical model, and the relaxation length of the thermal beam in the thermal beam contact model for ;in, represents the microscopic thermal expansion coefficient, Represents discrete units The temperature change, Represents discrete units The temperature change, Represents discrete units and discrete units the initial distance between centers; Step 2: Establish a discrete element model of thermal barrier coating according to the thermal barrier coating sample to be studied; Step 3, calibrating the microscopic parameters of the thermal beam contact model in the thermal barrier coating discrete element model through the macroscopic parameters of the thermal barrier coating sample; Step 4: Perform discrete element simulation of the ceramic layer in the discrete element model of the thermal barrier coating layer by layer: The calibrated microscopic parameters are input into the thermal beam contact model corresponding to the discrete element model of the thermal barrier coating, and different single-pass thicknesses, deposition temperature differences, ceramic layer intra-layer strengths, and ceramic layer inter-layer strengths are set. The ceramic layer in the discrete element model of the thermal barrier coating is simulated layer by layer by discrete element, and the crack structure diagram of the ceramic layer is obtained by the discrete element simulation of the ceramic layer layer by layer; Step 5: Analyze the crack structure diagram to obtain the crack mode; Step 6: Establish a database of correlation between preparation parameters and crack patterns: Establish a correlation database of single-pass thickness, deposition temperature difference, ceramic layer intra-layer strength and ceramic layer inter-layer strength preparation parameters and their corresponding crack structure diagrams and crack patterns; Step 7: Reverse design the preparation parameters based on the established preparation parameter and crack mode correlation database: The crack pattern required for preparation is screened from the correlation database established in step six, and the single-pass thickness, deposition temperature difference, intra-layer strength of the ceramic layer and inter-layer strength of the ceramic layer corresponding to the crack pattern required for preparation are used as reverse design preparation parameters.

2. A method for predicting the deposition crack structure of a ceramic layer and reversely designing preparation parameters according to claim 1, characterized in that: The thermal beam contact model described in step 1 also includes the following: ； in, Indicates that the heat transfer beam acts on the discrete unit The force on Indicates that the heat transfer beam acts on the discrete unit The force on Indicates that the heat transfer beam acts on the discrete element The torque, Indicates that the heat transfer beam acts on the discrete element The torque, represents the cross-sectional area of ​​the heat conducting beam, represents the microscopic Young's modulus, Indicates the longitudinal extension length of the thermal beam, represents the relaxation length of the thermal beam, Respectively represent the relative discrete units of the center line of the heat conducting beam The rotation amount is the X-axis component, Y-axis component, and Z-axis component in the local coordinate system of the beam; Respectively represent the relative discrete units of the center line of the heat conducting beam The rotation amount is the X-axis component, Y-axis component, and Z-axis component in the local coordinate system of the beam; They represent the X-axis direction, Y-axis direction, and Z-axis direction of the beam local coordinate system respectively; represents the micro shear modulus, represents the polar moment of inertia, Represents the moment of inertia along the Y-axis or Z-axis direction, represents the cross-sectional radius of the heat conducting beam, Represents pi.

3. A method for predicting the deposition crack structure of a ceramic layer and reversely designing preparation parameters according to claim 2, characterized in that: The thermal barrier coating discrete element model in step 2 includes a substrate discrete element model, a bonding layer discrete element model and a ceramic layer discrete element model, the substrate discrete element model, the bonding layer discrete element model and the ceramic layer discrete element model all satisfy the random close packing condition, and the ceramic layer discrete element model includes a first deposited ceramic layer, a second deposited ceramic layer, ..., an nth deposited ceramic layer, ..., an Nth deposited ceramic layer; wherein n and N are both positive integers, and 1≤n≤N; The crack modes described in step five include a longitudinal crack mode, a mixed crack mode in which longitudinal cracks and transverse cracks coexist, a transverse crack mode, and a crack-free mode.

4. A method for predicting the deposition crack structure of a ceramic layer and reversely designing preparation parameters according to claim 3, characterized in that: Before step 3, first obtain the relationship between the macroscopic parameters and the microscopic parameters of the thermal beam contact model. The specific process is as follows: Step A, using a computer to establish a cylindrical discrete element model; wherein the cylindrical discrete element model satisfies the random close packing condition, and the initial length of the cylindrical discrete element model is , the initial radius of the cylindrical discrete element model is ; Step B: Use computer to , calculate the dimensionless cross-sectional radius ;in, Represents the average radius of all discrete elements in the cylindrical discrete element model; dimensionless cross-sectional radius The value range of is 0.1~1.0; Step C: Use computer settings The value is 0.1, the microscopic Young's modulus The value is set to 0, and the cylindrical discrete element model is input to simulate the uniaxial tensile test, and the result is The stretched length of the cylindrical discrete element model under the microscopic Young's modulus is 0.1 , the stretched radius of the cylindrical discrete element model and the forces at both ends of the cylindrical discrete element model ; and according to the formula and , and the macroscopic Young's modulus under the microscopic Young's modulus is obtained and macroscopic Poisson's ratio ; Step D: Repeat step C multiple times, gradually increasing the microscopic Young's modulus by 100 GPa , until the microscopic Young's modulus The value of is 1000GPa, and we get The macroscopic Young's modulus and macroscopic Poisson's ratio under different microscopic Young's moduli when is 0.1; Step E, repeating steps C and D multiple times, gradually increasing the dimensionless cross-sectional radius according to a step size of 0.1 until the dimensionless cross-sectional radius takes a value of 1.0, thereby obtaining a linear fitting relationship between the microscopic Young's modulus and the macroscopic Young's modulus under different dimensionless cross-sectional radii and a macroscopic Poisson's ratio under different dimensionless cross-sectional radii; Step F: Setting the micro thermal conductivity using a computer The value is 0, and a one-dimensional numerical heat conduction simulation is performed on the cylindrical discrete element model. According to the analytical solution of one-dimensional heat conduction, the macroscopic thermal conductivity is obtained. ; Step G: Repeat step F multiple times, according to the step length Gradually increase the micro thermal conductivity until the micro thermal conductivity The value is , the linear fitting relationship between micro thermal conductivity and macro thermal conductivity is obtained; Step H: using a computer to establish a cube discrete element model, perform numerical thermal expansion simulation, and obtain a linear fitting relationship between the microscopic thermal expansion coefficient and the macroscopic thermal expansion coefficient.

5. A method for predicting the deposition crack structure of a ceramic layer and reversely designing preparation parameters according to claim 4, characterized in that: Step 3: The specific process is as follows: Step 301, linearly interpolating the macroscopic Poisson's ratio under different dimensionless cross-sectional radii in step E to obtain the dimensionless cross-sectional radius corresponding to the ceramic layer; and according to the method of step B, obtaining the cross-sectional radius of the heat-conducting beam corresponding to the ceramic layer; Step 302: According to the linear fitting relationship between the microscopic Young's modulus and the macroscopic Young's modulus at different dimensionless cross-sectional radii in step E, the macroscopic Young's modulus of the ceramic layer and the dimensionless cross-sectional radius corresponding to the ceramic layer in step 301 are input and linearly interpolated to obtain the microscopic Young's modulus of the ceramic layer corresponding to the thermal beam contact model. ; Step 303: According to the linear fitting relationship between the microscopic thermal expansion coefficient and the macroscopic thermal expansion coefficient in step H, the microscopic thermal expansion coefficient of the ceramic layer corresponding to the thermal beam contact model is obtained through the macroscopic thermal expansion coefficient of the ceramic layer; Step 304: according to the linear fitting relationship between the micro thermal conductivity and the macro thermal conductivity in step G, the macro thermal conductivity of the ceramic layer is input to obtain the micro thermal conductivity of the ceramic layer corresponding to the thermal beam contact model; Step 305: Set the microscopic Poisson's ratio of the ceramic layer corresponding to the thermal beam contact model , and according to the formula , the micro shear modulus of the ceramic layer corresponding to the thermal beam contact model is obtained ; Step 306: When the dimensionless cross-sectional radius corresponding to the ceramic layer and the microscopic Young's modulus of the thermal beam contact model corresponding to the ceramic layer are known, the microscopic fracture strength is set to 0 by a computer, and a uniaxial tensile test simulation is performed on the cylindrical discrete element model to obtain the fracture strength when the cylindrical discrete element model is destroyed, which is recorded as the macroscopic strength; Step 307, repeating step 306 multiple times, gradually increasing the microscopic fracture strength with a step length of 1 GPa, until the value of the microscopic fracture strength is 5 GPa, and obtaining a linear fitting relationship between the microscopic fracture strength and the macroscopic strength; Step 308, according to the linear fitting relationship between microscopic fracture strength and macroscopic strength, the ceramic layer intra-layer strength is input to obtain the microscopic fracture strength in the ceramic layer; Step 309, according to the method of step 308, the microscopic fracture strength between the ceramic layers is obtained according to the interlayer strength of the ceramic layers; Step 30A, according to the method of step 301 to step 305, according to the macroscopic Young's modulus, macroscopic Poisson's ratio, macroscopic thermal expansion coefficient and macroscopic thermal conductivity of the bonding layer, the cross-sectional radius of the thermal beam, the microscopic Young's modulus, the microscopic shear modulus, the microscopic thermal expansion coefficient and the microscopic thermal conductivity of the thermal beam contact model corresponding to the bonding layer are obtained; Step 30B, according to the method of steps 301 to 305, based on the macroscopic Young's modulus, macroscopic Poisson's ratio, macroscopic thermal expansion coefficient and macroscopic thermal conductivity of the substrate, obtain the cross-sectional radius of the thermal beam, microscopic Young's modulus, microscopic shear modulus, microscopic thermal expansion coefficient and microscopic thermal conductivity of the thermal beam contact model corresponding to the substrate.

6. A method for predicting the deposition crack structure of a ceramic layer and reversely designing preparation parameters according to claim 5, characterized in that: Step 4: The specific process is as follows: Step 401, using a computer to assign the cross-sectional radius of the heat-conducting beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient and micro thermal conductivity of the heat-conducting beam contact model corresponding to the substrate to the discrete element model of the substrate, assign the cross-sectional radius of the heat-conducting beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient and micro thermal conductivity of the heat-conducting beam contact model corresponding to the bonding layer to the discrete element model of the bonding layer, assign the cross-sectional radius of the heat-conducting beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength in the ceramic layer corresponding to the heat-conducting beam contact model to the first deposited ceramic layer; the micro thermal conductivity of other deposited ceramic layers is set to zero; Step 402, using a computer to set the thickness of the first deposited ceramic layer, the deposition temperature difference, the bottom of the substrate discrete element model and the environment with a temperature of Tc to perform convective heat transfer under a heat transfer coefficient hc, and the top of the first deposited ceramic layer and the spraying environment with a temperature of Ts to perform convective heat transfer under a heat transfer coefficient hs, then the substrate discrete element model, the bonding layer discrete element model and the first deposited ceramic layer are discrete element simulated based on their respective thermal beam contact models, and the crack structure of the first deposited ceramic layer is obtained; wherein the thickness of the first deposited ceramic layer is a single-pass thickness; Step 403, after the discrete element simulation of the first deposited ceramic layer is completed, the cross-sectional radius of the thermal beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength in the ceramic layer corresponding to the thermal beam contact model of the ceramic layer are assigned to the second deposited ceramic layer, the cross-sectional radius of the thermal beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength between ceramic layers corresponding to the thermal beam contact model of the ceramic layer are assigned to the thermal beam contact model between the first deposited ceramic layer and the second deposited ceramic layer, and the micro thermal conductivity of other deposited ceramic layers is set to zero; Step 404, using a computer to set the thickness of the second deposited ceramic layer, the deposition temperature difference, the bottom of the substrate discrete element model and the environment with a temperature of Tc to perform convective heat exchange at a heat transfer coefficient of hc, and the top of the second deposited ceramic layer and the spraying environment with a temperature of Ts to perform convective heat exchange at a heat transfer coefficient of hs, and perform discrete element simulation according to the method of step 402 to obtain the crack structure of the first deposited ceramic layer and the second deposited ceramic layer; wherein the thickness of the second deposited ceramic layer is a single-pass thickness; Step 405, repeating steps 403 and 404 for multiple times, after the discrete element simulation of the nth deposited ceramic layer is completed, the cross-sectional radius of the thermal beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength in the ceramic layer corresponding to the thermal beam contact model of the ceramic layer are assigned to the n+1th deposited ceramic layer, the cross-sectional radius of the thermal beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity and micro fracture strength between ceramic layers corresponding to the thermal beam contact model of the ceramic layer are assigned to the thermal beam contact model between the nth deposited ceramic layer and the n+1th deposited ceramic layer, and the micro thermal conductivity of other deposited ceramic layers is set to zero; and discrete element simulation is performed according to the method of step 404 to obtain the crack structure of the 1st deposited ceramic layer to the n+1th deposited ceramic layer; wherein n is a positive integer greater than 1; and the thickness of the nth deposited ceramic layer is a single pass thickness; Step 406, repeating step 405 multiple times until the discrete element simulation of the Nth deposited ceramic layer is completed, and a crack structure diagram of the discrete element simulation of the ceramic layer layer by layer is obtained; wherein the thickness of the Nth deposited ceramic layer is a single pass thickness; Step 407, repeat steps 401 to 406 multiple times, change the single pass thickness, deposition temperature difference, ceramic layer intra-layer strength and ceramic layer inter-layer strength, and obtain the crack structure diagram of the ceramic layer layer by layer discrete element simulation under different single pass thickness, deposition temperature difference, ceramic layer intra-layer strength and ceramic layer inter-layer strength.

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