A method for predicting the crack structure of ceramic layer deposition and reverse designing preparation parameters

Abstract

The present invention discloses a method for predicting the crack structure of ceramic layer deposition and reverse designing preparation parameters, including: 1. Establishing a heat conduction beam contact model; 2. Establishing a discrete element model of the thermal barrier coating according to the thermal barrier coating specimen to be studied; 3. Calibrating the microscopic parameters of the heat conduction beam contact model in the discrete element model of the thermal barrier coating through the macroscopic parameters of the thermal barrier coating specimen; 4. Conducting discrete element simulations layer by layer on the ceramic layer in the discrete element model of the thermal barrier coating; 5. Analyzing the crack structure diagram to obtain the crack pattern; 6. Establishing a correlation database between preparation parameters and crack patterns; 7. Reverse designing the preparation parameters according to the established correlation database between preparation parameters and crack patterns. The discrete element model of the thermal barrier coating in the present invention is based on the heat conduction beam contact model for layer-by-layer discrete element simulation to predict the crack structure during the layer-by-layer thermal deposition process of the ceramic layer, and it is convenient to screen from the correlation database according to the actual preparation requirements to reverse design the 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] To solve the above technical problems, the technical solution adopted by the present invention is: a method for predicting the crack structure of a ceramic layer deposition and reverse-designing preparation parameters, the method comprising the following steps:

[0007] Step 1: Establish a heat-conducting beam contact model:

[0008] Set discrete elements connected by a heat-conducting beam and discrete element , discrete element has an initial temperature of , discrete element has an initial temperature of , and establish a heat-conducting beam contact model; wherein, the heat-conducting beam contact model is an Euler-Bernoulli beam analytical model, and the relaxation length of the heat-conducting beam in the heat-conducting beam contact model is ; wherein, represents the microscopic thermal expansion coefficient, represents the temperature change of discrete element , represents the temperature change of discrete element , represents the initial distance between the centers of discrete element and discrete element ;

[0009] Step 2: Establish a discrete element model of the thermal barrier coating according to the thermal barrier coating specimen to be studied;

[0010] Step 3: Calibrate the microscopic parameters of the heat-conducting beam contact model in the discrete element model of the thermal barrier coating through the macroscopic parameters of the thermal barrier coating specimen;

[0011] Step 4: Conduct discrete element simulation layer by layer for the ceramic layer in the discrete element model of the thermal barrier coating:

[0012] Input the calibrated microscopic parameters into the heat-conducting beam contact model corresponding to the discrete element model of the thermal barrier coating, set different single-pass thicknesses, deposition temperature differences, in-layer strengths of the ceramic layer, and inter-layer strengths of the ceramic layer, and conduct discrete element simulation layer by layer for the ceramic layer in the discrete element model of the thermal barrier coating to obtain the crack structure diagram of the discrete element simulation layer by layer for the ceramic layer;

[0013] Step 5: Analyze the crack structure diagram to obtain the crack mode;

[0014] Step 6: Establish a correlation database between preparation parameters and crack modes:

[0015] Establish a correlation database between preparation parameters such as single-pass thickness, deposition temperature difference, in-layer strength of the ceramic layer, and inter-layer strength of the ceramic layer, and their corresponding crack structure diagrams and crack modes;

[0016] Step 7: Reverse design the preparation parameters based on the established correlation database between the preparation parameters and the crack patterns:

[0017] Screen from the correlation database established in Step 6 according to the crack pattern required for the preparation, and use the single-pass thickness, deposition temperature difference, in-layer strength of the ceramic layer, and inter-layer strength of the ceramic layer corresponding to the crack pattern required for the preparation as the reverse-designed preparation parameters.

[0018] For the above method for predicting the deposition crack structure of the ceramic layer and reverse-designing the preparation parameters, further, the heat conduction beam contact model described in Step 1 further includes the following:

[0019] ;

[0020] Among them, represents the force exerted by the heat conduction beam on the discrete element ; represents the force exerted by the heat conduction beam on the discrete element ; represents the moment exerted by the heat conduction beam on the discrete element ; represents the moment exerted by the heat conduction beam on the discrete element ; represents the cross-sectional area of the heat conduction beam, represents the microscopic Young's modulus, represents the longitudinal extension length of the heat conduction beam, represents the relaxation length of the heat conduction beam, respectively represent the X-axis component, Y-axis component, and Z-axis component of the rotation amount of the center line of the heat conduction beam relative to the discrete element in the local coordinate system of the beam; respectively represent the X-axis component, Y-axis component, and Z-axis component of the rotation amount of the center line of the heat conduction beam relative to the discrete element in the local coordinate system of the beam; respectively represent the X-axis direction, Y-axis direction, and Z-axis direction of the local coordinate system of the beam; represents the microscopic shear modulus, represents the polar moment of inertia, represents the moment of inertia along the Y-axis direction or Z-axis direction, represents the cross-sectional radius of the heat conduction beam, represents the pi.

[0021] 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;

[0022] 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.

[0023] 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:

[0024] 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 ;

[0025] 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;

[0026] 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 ;

[0027] Step D: Repeat step C multiple times, gradually increasing the microscopic Young's modulus by 100 GPa , until the value of the microscopic Young's modulus is 1000 GPa, to obtain the macroscopic Young's modulus and macroscopic Poisson's ratio at different microscopic Young's moduli when it is 0.1;

[0028] Step E: Repeat steps C and D multiple times, gradually increase the dimensionless cross-sectional radius in steps of 0.1 until the dimensionless cross-sectional radius takes a value of 1.0, then the linear fitting relationship between the microscopic Young's modulus and the macroscopic Young's modulus at different dimensionless cross-sectional radii and the macroscopic Poisson's ratio at different dimensionless cross-sectional radii can be obtained;

[0029] Step F: Use a computer to set the value of the microscopic thermal conductivity to be 0, perform one-dimensional numerical heat conduction simulation on the cylindrical discrete element model, and according to the analytical solution method of one-dimensional heat conduction, obtain the macroscopic thermal conductivity ;

[0030] Step G: Repeat step F multiple times, gradually increase the microscopic thermal conductivity in steps of until the value of the microscopic thermal conductivity takes a value of , to obtain the linear fitting relationship between the microscopic thermal conductivity and the macroscopic thermal conductivity;

[0031] Step H: Use a computer to establish a cubic discrete element model, perform numerical thermal expansion simulation, and obtain the linear fitting relationship between the microscopic thermal expansion coefficient and the macroscopic thermal expansion coefficient.

[0032] For the above method for predicting the crack structure of ceramic layer deposition and reverse designing the preparation parameters, further, step three, the specific process is as follows:

[0033] Step 301: Perform linear interpolation on the macroscopic Poisson's ratio at 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 in step B, obtain the cross-sectional radius of the thermal conduction beam corresponding to the ceramic layer;

[0034] 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, input the macroscopic Young's modulus of the ceramic layer and the dimensionless cross-sectional radius corresponding to the ceramic layer in step 301 and perform linear interpolation to obtain the microscopic Young's modulus of the thermal conduction beam contact model corresponding to the ceramic layer ;

[0035] 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 thermal conduction beam contact model corresponding to the ceramic layer can be obtained through the macroscopic thermal expansion coefficient of the ceramic layer;

[0036] Step 304: Input the macroscopic thermal conductivity of the ceramic layer according to the linear fitting relationship between the microscopic thermal conductivity and the macroscopic thermal conductivity in Step G to obtain the microscopic thermal conductivity of the ceramic layer corresponding to the thermal beam contact model.

[0037] Step 305: Set the microscopic Poisson's ratio of the ceramic layer corresponding to the thermal beam contact model , and according to the formula , obtain the microscopic shear modulus of the ceramic layer corresponding to the thermal beam contact model .

[0038] Step 306: Given the dimensionless cross-sectional radius of the ceramic layer and the microscopic Young's modulus of the ceramic layer corresponding to the thermal beam contact model, use a computer to set the value of the microscopic fracture strength to 0 and perform a uniaxial tensile experiment simulation on the cylindrical discrete element model to obtain the fracture strength at the failure of the cylindrical discrete element model, denoted as the macroscopic strength.

[0039] Step 307: Repeat Step 306 multiple times, gradually increase the microscopic fracture strength by a step of 1 GPa until the value of the microscopic fracture strength is 5 GPa to obtain the linear fitting relationship between the microscopic fracture strength and the macroscopic strength.

[0040] Step 308: Input the in-layer strength of the ceramic layer according to the linear fitting relationship between the microscopic fracture strength and the macroscopic strength to obtain the microscopic fracture strength within the ceramic layer.

[0041] Step 309: According to the method in Step 308, obtain the microscopic fracture strength between the layers of the ceramic layer based on the inter-layer strength of the ceramic layer.

[0042] Step 30A: According to the method in 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 bonding layer, 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 bonding layer corresponding to the thermal beam contact model.

[0043] Step 30B: According to the method in 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 substrate corresponding to the thermal beam contact model.

[0044] For the above method for predicting the deposition crack structure of the ceramic layer and reverse designing the preparation parameters, further, Step Four is specifically as follows:

[0045] Step 401: Use a computer to assign the beam cross-sectional radius, 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 matrix to the discrete element model of the matrix, assign the beam cross-sectional radius, 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, and assign the beam cross-sectional radius, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity, and micro fracture strength within the ceramic layer of the heat-conducting beam contact model corresponding to the ceramic layer to the first deposited ceramic layer; set the micro thermal conductivity of other deposited ceramic layers to zero;

[0046] Step 402: Use a computer to set the thickness of the first deposited ceramic layer, deposition temperature difference, perform convective heat transfer between the bottom of the discrete element model of the matrix and the environment with temperature Tc under heat transfer coefficient hc, and perform convective heat transfer between the top of the first deposited ceramic layer and the spraying environment with temperature Ts under heat transfer coefficient hs. Then, the discrete element models of the matrix, bonding layer, and the first deposited ceramic layer perform discrete element simulations based on their respective heat-conducting beam contact models, and obtain the crack structure of the first deposited ceramic layer; among them, the thickness of the first deposited ceramic layer is the single-pass thickness;

[0047] Step 403: After the discrete element simulation of the first deposited ceramic layer is completed, assign the beam cross-sectional radius, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity, and micro fracture strength within the ceramic layer of the heat-conducting beam contact model corresponding to the ceramic layer to the second deposited ceramic layer, and assign the beam cross-sectional radius, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, micro thermal conductivity, and micro fracture strength between the ceramic layers of the heat-conducting beam contact model corresponding to the ceramic layer to the heat-conducting beam contact model between the first deposited ceramic layer and the second deposited ceramic layer; set the micro thermal conductivity of other deposited ceramic layers to zero;

[0048] Step 404: Use a computer to set the thickness of the second deposited ceramic layer, deposition temperature difference, perform convective heat transfer between the bottom of the discrete element model of the matrix and the environment with temperature Tc under heat transfer coefficient hc, and perform convective heat transfer between the top of the second deposited ceramic layer and the spraying environment with temperature Ts under heat transfer coefficient hs. Perform discrete element simulation according to the method in Step 402 to obtain the crack structures of the first deposited ceramic layer and the second deposited ceramic layer; among them, the thickness of the second deposited ceramic layer is the single-pass thickness;

[0049] Step 405: Repeat Step 403 and Step 404 multiple times. After the discrete element simulation of the nth deposited ceramic layer is completed, the cross-sectional radius of the heat conduction beam, the microscopic Young's modulus, the microscopic shear modulus, the microscopic coefficient of thermal expansion, the microscopic thermal conductivity of the heat conduction beam contact model corresponding to the ceramic layer, and the microscopic fracture strength within the ceramic layer are assigned to the (n + 1)th deposited ceramic layer. The cross-sectional radius of the heat conduction beam, the microscopic Young's modulus, the microscopic shear modulus, the microscopic coefficient of thermal expansion, the microscopic thermal conductivity of the heat conduction beam contact model corresponding to the ceramic layer, and the microscopic fracture strength between the layers of the ceramic layer are assigned to the heat conduction beam contact model between the nth deposited ceramic layer and the (n + 1)th deposited ceramic layer. The microscopic thermal conductivities of other deposited ceramic layers are set to zero; and the discrete element simulation is performed according to the method in Step 404 to obtain the crack structure of the 1st deposited ceramic layer to the (n + 1)th deposited ceramic layer; where n is a positive integer greater than 1; the thickness of the nth deposited ceramic layer is the single-pass thickness;

[0050] Step 406: Repeat Step 405 multiple times until the discrete element simulation of the Nth deposited ceramic layer is completed to obtain the crack structure diagram of the discrete element simulation layer by layer of the ceramic layer; where the thickness of the Nth deposited ceramic layer is the single-pass thickness;

[0051] Step 407: Repeat Step 401 to Step 406 multiple times, change the single-pass thickness, deposition temperature difference, in-layer strength of the ceramic layer, and inter-layer strength of the ceramic layer to obtain the crack structure diagrams of the discrete element simulation layer by layer of the ceramic layer under different single-pass thicknesses, deposition temperature differences, in-layer strengths of the ceramic layer, and inter-layer strengths of the ceramic layer.

[0052] The present invention has the following advantages compared with the prior art:

[0053] 1. The method steps of the present invention are simple and reasonably designed, solving the problems of the limitations of using the continuous medium mechanics method to simulate cracks and the inability of the scanning electron microscope experiment method to capture cracks during the layer-by-layer deposition process.

[0054] 2. The present invention is based on the discrete element method under thermal and mechanical actions, facilitating subsequent discretization of the solution space of the thermal barrier coating discrete element model into discrete elements, connecting the discrete elements through heat conduction beams, and calculating the forces and torques acting on the discrete elements according to the analytical solution of the Euler-Bernoulli beam.

[0055] 3. The relaxation length of the heat conduction beam is set in the heat conduction beam contact model of the present invention. When considering the initial distance between the centers of two discrete elements, it also changes with the temperature change amount of the two discrete elements, enabling the heat conduction beam contact model to simultaneously simulate thermal and mechanical behaviors, and further enabling the simulation of the crack evolution structure of the thermal barrier coating during the thermal deposition process.

[0056] 4. The discrete element model of the thermal barrier coating established in the present invention is based on the thermal conduction beam contact model for layer-by-layer discrete element simulation, obtaining the crack structure diagram of the ceramic layer through layer-by-layer discrete element simulation, thereby realizing the prediction of the crack structure during the layer-by-layer thermal deposition process of the ceramic layer. And by changing the preparation parameters such as the single-pass thickness, deposition temperature difference, in-layer strength of the ceramic layer, and inter-layer strength of the ceramic layer, a correlation database between the preparation parameters and the crack mode is obtained, so as to reverse design the preparation parameters according to the established correlation database between the preparation parameters and the crack mode.

[0057] In summary, the method steps of the present invention are simple and reasonably designed. By constructing the thermal conduction beam contact model, the discrete element simulation under thermal and mechanical actions is realized, so that the discrete element model of the thermal barrier coating is based on the thermal conduction beam contact model for layer-by-layer discrete element simulation, obtaining the crack structure diagram of the ceramic layer through layer-by-layer discrete element simulation, realizing the prediction of the crack structure during the layer-by-layer thermal deposition process of the ceramic layer, quickly establishing a correlation database between the single-pass thickness, deposition temperature difference, in-layer strength of the ceramic layer, and inter-layer strength of the ceramic layer and their corresponding crack structure diagrams and crack modes, and facilitating the screening from the correlation database according to the actual preparation requirements to reverse design the preparation parameters, saving the preparation cost.

[0058] Next, through the drawings and embodiments, the technical solutions of the present invention will be further described in detail. Description of the Drawings

[0059] Figure 1 This is the initial state of the thermal conduction beam contact model of the present invention.

[0060] Figure 2 This is the deformed state of the thermal conduction beam contact model of the present invention.

[0061] Figure 3 This is the method flow block diagram of the present invention.

[0062] Figure 4 This is the crack structure diagram of the simulation when the deposition temperature difference of the present invention is 100K.

[0063] Figure 5 This is the crack structure diagram of the simulation when the deposition temperature difference of the present invention is 539K.

[0064] Figure 6 This is the crack structure diagram of the simulation when the deposition temperature difference of the present invention is 610K. Detailed Embodiments

[0065] As Figures 1 to 3 shown, a method for predicting the deposition crack structure of a ceramic layer and reverse designing preparation parameters in the present invention includes the following steps:

[0066] Step 1. Establish a thermal conduction beam contact model:

[0067] Set discrete elements connected by a heat-conducting beam and the discrete elements , the initial temperature of the discrete element is , the initial temperature of the discrete element is , and establish a heat-conducting beam contact model; wherein, the heat-conducting beam contact model is an Euler-Bernoulli beam analytical model, and the relaxation length of the heat-conducting beam in the heat-conducting beam contact model is ; wherein, represents the coefficient of micro-thermal expansion, represents the temperature change of the discrete element , represents the temperature change of the discrete element , represents the initial distance between the centers of the discrete element and the discrete element ;

[0068] Step 2: Establish a discrete element model of the thermal barrier coating according to the thermal barrier coating specimen to be studied;

[0069] Step 3: Calibrate the microparameters of the heat-conducting beam contact model in the thermal barrier coating discrete element model through the macroscopic parameters of the thermal barrier coating specimen;

[0070] Step 4: Conduct discrete element simulations layer by layer on the ceramic layer in the thermal barrier coating discrete element model:

[0071] Input the calibrated microparameters into the heat-conducting beam contact model corresponding to the thermal barrier coating discrete element model, set different single-pass thicknesses, deposition temperature differences, in-layer strengths of the ceramic layer, and inter-layer strengths of the ceramic layer, conduct discrete element simulations layer by layer on the ceramic layer in the thermal barrier coating discrete element model, and obtain the crack structure diagram of the discrete element simulation layer by layer of the ceramic layer;

[0072] Step 5: Analyze the crack structure diagram to obtain the crack pattern;

[0073] Step 6: Establish a correlation database between the preparation parameters and the crack pattern:

[0074] Establish a correlation database between the preparation parameters of the single-pass thickness, deposition temperature difference, in-layer strength of the ceramic layer, and inter-layer strength of the ceramic layer and their corresponding crack structure diagrams and crack patterns;

[0075] Step 7: Reverse design the preparation parameters according to the established correlation database between the preparation parameters and the crack pattern:

[0076] Screen from the correlation database established in Step 6 according to the required crack pattern for preparation, and use the single-pass thickness, deposition temperature difference, in-layer strength of the ceramic layer, and inter-layer strength of the ceramic layer corresponding to the required crack pattern for preparation as the reverse design preparation parameters.

[0077] In this embodiment, the thermal conduction beam contact model described in Step 1 further includes the following:

[0078] ;

[0079] Among them, represents the force exerted by the thermal conduction beam on the discrete element ; represents the force exerted by the thermal conduction beam on the discrete element ; represents the moment exerted by the thermal conduction beam on the discrete element ; represents the moment exerted by the thermal conduction beam on the discrete element ; represents the cross-sectional area of the thermal conduction beam, represents the microscopic Young's modulus, represents the longitudinal extension length of the thermal conduction beam, represents the relaxation length of the thermal conduction beam, respectively represent the X-axis component, Y-axis component, and Z-axis component of the rotation amount of the center line of the thermal conduction beam relative to the discrete element in the local coordinate system of the beam; respectively represent the X-axis component, Y-axis component, and Z-axis component of the rotation amount of the center line of the thermal conduction beam relative to the discrete element in the local coordinate system of the beam; respectively represent the X-axis direction, Y-axis direction, and Z-axis direction of the local coordinate system of the beam; represents the microscopic shear modulus, represents the polar moment of inertia, represents the moment of inertia along the Y-axis direction or Z-axis direction, represents the cross-sectional radius of the thermal conduction beam, represents the pi.

[0080] In this embodiment, the thermal barrier coating discrete element model described in Step 2 includes a substrate discrete element model, a bond coat discrete element model, and a ceramic layer discrete element model. The substrate discrete element model, the bond coat discrete element model, and the ceramic layer discrete element model all satisfy the random close packing condition. The ceramic layer discrete element model includes the 1st deposited ceramic layer, the 2nd deposited ceramic layer,..., the nth deposited ceramic layer,..., the Nth deposited ceramic layer; where n and N are both positive integers, and 1 ≤ n ≤ N;

[0081] The crack patterns described in step five include a longitudinal crack pattern, a mixed crack pattern with coexisting longitudinal and transverse cracks, a transverse crack pattern, and a crack-free pattern.

[0082] In this embodiment, before step three, the relationship between the macroscopic parameters and the microscopic parameters of the heat conduction beam contact model is obtained first. The specific process is as follows:

[0083] Step A: Use a computer to establish a cylindrical discrete element model; wherein, the cylindrical discrete element model satisfies the condition of random close packing, and the initial length of the cylindrical discrete element model is , and the initial radius of the cylindrical discrete element model is ;

[0084] Step B: Use a computer to calculate the dimensionless cross-sectional radius according to ; wherein, represents the average radius of all discrete elements in the cylindrical discrete element model; the value range of the dimensionless cross-sectional radius is 0.1 to 1.0;

[0085] Step C: Use a computer to set to take the value of 0.1, and the microscopic Young's modulus to take the value of 0, input it into the cylindrical discrete element model for uniaxial tensile experiment simulation, and obtain as the tensile length of the cylindrical discrete element model, the tensile radius of the cylindrical discrete element model, and the force at both ends of the cylindrical discrete element model; and according to the formulas and , obtain the macroscopic Young's modulus and the macroscopic Poisson's ratio under this microscopic Young's modulus;

[0086] Step D: Repeat step C multiple times, and gradually increase the microscopic Young's modulus in steps of 100 GPa until the value of the microscopic Young's modulus is 1000 GPa, and obtain as the macroscopic Young's modulus and macroscopic Poisson's ratio under different microscopic Young's moduli when it is 0.1;

[0087] Step E: Repeat steps C and D multiple times, and gradually increase the dimensionless cross-sectional radius in steps of 0.1 until the dimensionless cross-sectional radius takes the value of 1.0, then obtain the linear fitting relationship between the microscopic Young's modulus and the macroscopic Young's modulus under different dimensionless cross-sectional radii and the macroscopic Poisson's ratio under different dimensionless cross-sectional radii;

[0088] Step F: Use a computer to set the microscopic thermal conductivity Take the value as 0, conduct one-dimensional numerical heat conduction simulation on the cylindrical discrete element model, and obtain the macroscopic thermal conductivity according to the analytical solution of one-dimensional heat conduction ;

[0089] Step G: Repeat Step F multiple times, and gradually increase the microscopic thermal conductivity in accordance with the step size until the value of the microscopic thermal conductivity is , to obtain the linear fitting relationship between the microscopic thermal conductivity and the macroscopic thermal conductivity;

[0090] Step H: Use a computer to establish a cubic discrete element model, conduct numerical thermal expansion simulation, and obtain the linear fitting relationship between the microscopic thermal expansion coefficient and the macroscopic thermal expansion coefficient.

[0091] In this embodiment, Step 3 is specifically as follows:

[0092] Step 301: Conduct linear interpolation on the macroscopic Poisson's ratios at 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 in Step B, obtain the cross-sectional radius of the heat conduction beam corresponding to the ceramic layer;

[0093] 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, input the macroscopic Young's modulus of the ceramic layer and the dimensionless cross-sectional radius corresponding to the ceramic layer in Step 301 and conduct linear interpolation to obtain the microscopic Young's modulus of the heat conduction beam contact model corresponding to the ceramic layer ;

[0094] Step 303: According to the linear fitting relationship between the microscopic thermal expansion coefficient and the macroscopic thermal expansion coefficient in Step H, obtain the microscopic thermal expansion coefficient of the heat conduction beam contact model corresponding to the ceramic layer through the macroscopic thermal expansion coefficient of the ceramic layer;

[0095] Step 304: According to the linear fitting relationship between the microscopic thermal conductivity and the macroscopic thermal conductivity in Step G, input the macroscopic thermal conductivity of the ceramic layer to obtain the microscopic thermal conductivity of the heat conduction beam contact model corresponding to the ceramic layer;

[0096] Step 305: Set the microscopic Poisson's ratio of the heat conduction beam contact model corresponding to the ceramic layer, and according to the formula , obtain the microscopic shear modulus ;

[0097] Step 306: Given the dimensionless cross-sectional radius corresponding to the ceramic layer and the micro Young's modulus of the contact model of the heat-conducting beam corresponding to the ceramic layer, use a computer to set the value of the micro fracture strength to 0, perform a uniaxial tensile experiment simulation on the cylindrical discrete element model, and obtain the fracture strength at the failure of the cylindrical discrete element model, denoted as the macroscopic strength.

[0098] Step 307: Repeat Step 306 multiple times, gradually increase the micro fracture strength by a step size of 1 GPa until the value of the micro fracture strength reaches 5 GPa, and obtain the linear fitting relationship between the micro fracture strength and the macroscopic strength.

[0099] Step 308: Input the in-layer strength of the ceramic layer according to the linear fitting relationship between the micro fracture strength and the macroscopic strength to obtain the micro fracture strength within the ceramic layer.

[0100] Step 309: According to the method of Step 308, obtain the micro fracture strength between the layers of the ceramic layer based on the inter-layer strength of the ceramic layer.

[0101] Step 30A: 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 bonding layer, obtain 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 contact model of the heat-conducting beam corresponding to the bonding layer.

[0102] 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 heat-conducting beam, micro Young's modulus, micro shear modulus, micro thermal expansion coefficient, and micro thermal conductivity of the contact model of the heat-conducting beam corresponding to the substrate.

[0103] In this embodiment, Step Four is specifically as follows:

[0104] Step 401: Use 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 contact model of the heat-conducting beam corresponding to the substrate to the substrate discrete element model, 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 contact model of the heat-conducting beam corresponding to the bonding layer to the bonding layer discrete element model, and 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 the micro fracture strength within the ceramic layer of the contact model of the heat-conducting beam corresponding to the ceramic layer to the first deposited ceramic layer; the micro thermal conductivity of other deposited ceramic layers is set to zero.

[0105] Step 402: Use a computer to set the thickness of the first deposited ceramic layer, the deposition temperature difference, the bottom of the matrix discrete element model, and the convective heat transfer under the environment with a temperature of Tc and a heat transfer coefficient of hc, and the top of the first deposited ceramic layer and the spraying environment with a temperature of Ts and a heat transfer coefficient of hs for convective heat transfer. Then, the matrix discrete element model, the bonding layer discrete element model, and the first deposited ceramic layer perform discrete element simulations based on their respective thermal conductive beam contact models, and obtain the crack structure of the first deposited ceramic layer; where the thickness of the first deposited ceramic layer is the single-pass thickness;

[0106] After the discrete element simulation of the first deposited ceramic layer is completed, assign the thermal conductive beam cross-sectional radius, microscopic Young's modulus, microscopic shear modulus, microscopic coefficient of thermal expansion, microscopic thermal conductivity, and microscopic fracture strength within the ceramic layer of the thermal conductive beam contact model corresponding to the ceramic layer to the second deposited ceramic layer, and assign the thermal conductive beam cross-sectional radius, microscopic Young's modulus, microscopic shear modulus, microscopic coefficient of thermal expansion, microscopic thermal conductivity, and microscopic fracture strength between the ceramic layers of the thermal conductive beam contact model corresponding to the ceramic layer to the thermal conductive beam contact model between the first deposited ceramic layer and the second deposited ceramic layer, and set the microscopic thermal conductivity of other deposited ceramic layers to zero;

[0107] Step 404: Use a computer to set the thickness of the second deposited ceramic layer, the deposition temperature difference, the bottom of the matrix discrete element model, and the convective heat transfer under the environment with a temperature of Tc and a heat transfer coefficient of hc, and the top of the second deposited ceramic layer and the spraying environment with a temperature of Ts and a heat transfer coefficient of hs for convective heat transfer. Perform discrete element simulations according to the method in Step 402 to obtain the crack structures of the first deposited ceramic layer and the second deposited ceramic layer; where the thickness of the second deposited ceramic layer is the single-pass thickness;

[0108] Repeat Step 403 and Step 404 multiple times. After the discrete element simulation of the nth deposited ceramic layer is completed, assign the thermal conductive beam cross-sectional radius, microscopic Young's modulus, microscopic shear modulus, microscopic coefficient of thermal expansion, microscopic thermal conductivity, and microscopic fracture strength within the ceramic layer of the thermal conductive beam contact model corresponding to the ceramic layer to the (n + 1)th deposited ceramic layer, and assign the thermal conductive beam cross-sectional radius, microscopic Young's modulus, microscopic shear modulus, microscopic coefficient of thermal expansion, microscopic thermal conductivity, and microscopic fracture strength between the ceramic layers of the thermal conductive beam contact model corresponding to the ceramic layer to the thermal conductive beam contact model between the nth deposited ceramic layer and the (n + 1)th deposited ceramic layer, and set the microscopic thermal conductivity of other deposited ceramic layers to zero; and perform discrete element simulations according to the method in Step 404 to obtain the crack structures of the first deposited ceramic layer to the (n + 1)th deposited ceramic layer; where n is a positive integer greater than 1; the thickness of the nth deposited ceramic layer is the single-pass thickness;

[0109] Step 406: Repeat Step 405 multiple times until the discrete element simulation of the Nth deposited ceramic layer is completed, obtaining the crack structure diagram of the discrete element simulation of the ceramic layer layer by layer; where the thickness of the Nth deposited ceramic layer is the single-pass thickness;

[0110] Step 407: Repeat Steps 401 to 406 multiple times, changing the single-pass thickness, deposition temperature difference, in-layer strength of the ceramic layer, and inter-layer strength of the ceramic layer, to obtain the crack structure diagrams of the discrete element simulation of the ceramic layer layer by layer under different single-pass thicknesses, deposition temperature differences, in-layer strengths of the ceramic layer, and inter-layer strengths of the ceramic layer.

[0111] In this embodiment, further, in the thermal barrier coating specimen to be studied, the substrate is a nickel-based superalloy substrate, the bond coat is an oxidation-resistant bond coat, and the ceramic layer is a yttria-stabilized zirconia (YSZ) ceramic layer; the number of depositions of the ceramic layer is N. The thickness of the substrate is 2 mm, the thickness of the bond coat is 0.5 mm, and the thickness of the ceramic layer is 400 μm to 1500 μm.

[0112] In this embodiment, further, the discrete element model of the thermal barrier coating is transformed from three-dimensional to two-dimensional for the thermal barrier coating specimen to be studied, so that the cuboid thermal barrier coating specimen is transformed into a rectangular discrete element model.

[0113] In this embodiment, further, Figure 1 and Figure 2 the midline of the heat conduction beam is represented, and one end of the heat conduction beam is located at the center of the discrete element and the other end of the heat conduction beam is located at the center of the discrete element ; ; . represents the rotation amount of the midline of the heat conduction beam relative to the discrete element , represents the rotation amount of the midline of the heat conduction beam relative to the discrete element .

[0114] In this embodiment, further, in the initial state, a local reference system of the axis, axis, and axis is established at the center of the discrete element , and a local reference system of the axis, axis, and axis is established at the center of the discrete element ; where the axis in the local reference system and the in the local reference system axis and the in the local reference system The axes are close to each other along the center line of the heat conducting beam;

[0115] 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.

[0116] In this embodiment, it should be noted that the macroscopic Poisson's ratio Only with related.

[0117] 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 ;

[0118] 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 ;

[0119] 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;

[0120] 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.

[0121] 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.

[0122] In this embodiment, Tc is 298K, hc is , Ts is 748K, hs is .

[0123] 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.

[0124] In this embodiment,Figures 4 to 6 The bottom corresponds to the substrate and the bonding layer, and the upper part corresponds to the ceramic layer. The discrete element simulation is carried out layer by layer to obtain the crack structure diagrams simulated when the in-layer strength of the ceramic layer is 110 MPa, the inter-layer strength of the ceramic layer is 100 MPa, and the deposition temperature differences are 100 K, 539 K, and 610 K. Figure 4 There is a crack-free mode in [diagram reference 1], Figure 5 There is a longitudinal crack mode in [diagram reference 2], Figure 6 There is a mixed crack mode with the coexistence of longitudinal cracks and transverse cracks in [diagram reference 3]. The cross-section of the thermal barrier coating specimen is scanned with a scanning electron microscope to obtain the actual crack structures when the deposition temperature differences are 100 K, 539 K, and 610 K. By comparing the simulated crack structure diagrams with the actual crack structures, the crack modes obtained by the layer-by-layer discrete element simulation are consistent with the actual crack modes.

[0125] In this embodiment, when the deposition temperature difference is 100 K, the in-layer strength and the inter-layer strength of the ceramic layer are also changed, and the discrete element simulation is carried out layer by layer within the value range of 60 MPa to 200 MPa to obtain each crack structure diagram.

[0126] In this embodiment, further, this method is also applicable to other coatings prepared by thermal deposition methods, such as SiO 2 coatings, Cr 2 O 3 coatings, enamel coatings, and environmental barrier coatings EBC.

[0127] In summary, the method of the present invention has simple steps and reasonable design. By constructing a thermal conduction beam contact model, the discrete element simulation under thermal and mechanical actions is realized, so that the discrete element model of the thermal barrier coating is subjected to layer-by-layer discrete element simulation based on the thermal conduction beam contact model to obtain the crack structure diagrams of the layer-by-layer discrete element simulation of the ceramic layer, realizing the prediction of the crack structure during the layer-by-layer thermal deposition process of the ceramic layer, quickly establishing a correlation database of the single-pass thickness, deposition temperature difference, in-layer strength and inter-layer strength of the ceramic layer and their corresponding crack structure diagrams and crack modes, and facilitating the screening from the correlation database according to the actual preparation requirements to reverse design the preparation parameters, saving the preparation cost.

[0128] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent structural changes made to the above embodiments according to the technical essence of the present invention still fall 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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