Crack propagation simulation analysis method based on cyclic load of thermal barrier coating with real structure

Abstract

The invention discloses a crack propagation simulation analysis method based on a real-structure thermal barrier coating under cyclic load, which comprises the following steps: creating a finite element model according to a thermal barrier coating sample; setting material attributes and section characteristics in the finite element model; after parameters are set, a thermal cycle load is applied to the surface of the finite element model, analysis is carried out after grid division, and an Odb file is obtained; and copying the finite element model, taking the Odb file as a boundary condition, and carrying out thermal-mechanical coupling to obtain thermal stress and crack expansion conditions after thermal circulation. The analysis method is simple, the real service condition and the microstructure are fitted, the expected research effect is achieved for finite element simulation, and accurate simulation data can be obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of finite element modeling and dynamic simulation analysis, and specifically is a crack propagation simulation analysis method based on a real structure thermal barrier coating under cyclic load. Background Art

[0002] Thermal barrier coatings play an important role in the aerospace field, especially in aero-engine parts. Ceramic materials with high melting points and low thermal conductivity are coated on the surface of aero-engine blades made of high-temperature alloys to reduce the temperature of the substrate and increase work efficiency. The structure of thermal barrier coatings usually includes the following four parts: ceramic layer, metal bonding layer, thermally grown oxide, and high-temperature alloy substrate, among which thermally grown oxide is produced during service. During service, the coating fails due to a series of physical and chemical effects such as mechanical loads, thermal stresses, sintering, thermal shock and thermal shock. The failure form is generally the formation, expansion, connection, and peeling of microcracks in the ceramic layer.

[0003] Finite element analysis is a modern computational method that has developed rapidly based on structural mechanics analysis. It is widely used due to its low cost, high efficiency and ability to solve large engineering problems. Currently, the simulation research on crack propagation of thermal barrier coatings (TBC) under high temperature service conditions mainly focuses on the numerical simulation of crack initiation and propagation behavior.

[0004] There are some obvious limitations of current crack propagation simulation technology: 1) The computational cost of the simulation process is high. Since thermal barrier coatings have a multi-layer structure and the material properties of different layers are different, a large amount of computing resources are required to perform a detailed simulation of the entire model. Especially when considering multiple complex physical phenomena such as thermal loads, thermal oxide generation, and ceramic layer sintering, existing methods often face the problems of low computational efficiency and high consumption of computing resources, making it difficult to meet the high efficiency requirements in engineering applications.

[0005] 2) Lack of ideal results for life prediction. Due to the lack of comprehensive simulation of real service conditions and the dynamic expansion process of coating cracks, existing technologies are often unable to accurately evaluate the service life of thermal barrier coatings. Thermal barrier coatings face complex multi-physical field coupling in high-temperature environments, including temperature and stress field changes caused by thermal cycles, the formation of oxide layers, and the microstructural evolution of ceramic layers, including sintering and high-temperature creep. These factors cause cracks to initiate and propagate, and the paths are nonlinear and random. Therefore, this complexity often leads to insufficient accuracy of simulation results, making it difficult to accurately evaluate the fatigue life and overall reliability of the coating. Summary of the invention

[0006] In order to overcome the technical problem of inaccurate prediction of fatigue life and overall reliability of thermal barrier coatings in the prior art, the purpose of the present invention is to provide a crack propagation simulation analysis method under cyclic load of thermal barrier coatings based on real structures, which has accurate prediction.

[0007] In order to achieve the above purpose, the technical solution adopted by the present invention is: A crack propagation simulation analysis method based on a real structure thermal barrier coating under cyclic load, comprising the following steps: Create a finite element model based on thermal barrier coating samples; Set material properties and cross-section characteristics in the finite element model; After setting the parameters, apply thermal cycle load to the surface of the finite element model, divide the mesh and analyze it to obtain the Odb file After copying the finite element model, the Odb file is used as the boundary condition to perform thermal-mechanical coupling to obtain the thermal stress and crack extension after thermal cycling.

[0008] Furthermore, the finite element model includes a high temperature alloy substrate, a bonding layer, a hot metal oxide and a ceramic layer which are arranged in sequence from bottom to top.

[0009] Furthermore, the material of the high-temperature alloy substrate was selected as DD26, and the modeling was 250 μm × 50 μm, and the material properties were determined by experiments; the element types in the first and second jobs were shell elements DC2D4 and CPS4R, respectively; The bonding layer material is NiCrAlY, and the modeling is 250μm×20μm, where the interface between the bonding layer and the ceramic layer is a sinusoidal wave interface. The material properties are determined by experiments, and the unit types are shell elements DC2D4 and CPS4R in the first and second jobs respectively; The thermal metal oxide is a thermal metal oxide, modeled as 250 μm × 2 μm, the material properties are determined experimentally, and the element types are shell elements DC2D4 and CPS4R in the first and second jobs, respectively; The ceramic layer is made of ScYSZ material and is modeled as 250μm×80μm, where the model porosity is 5%. The material properties are determined experimentally, and the unit types are shell elements DC2D4 and CPS4R in the first and second jobs, respectively.

[0010] Furthermore, parameters include assembly parts, analysis steps and variable outputs and contact relationships.

[0011] Furthermore, the analysis steps are as follows: the type is set to Heat transfer, the incremental step type is Automatic, the initial incremental step is 0.1, and the maximum incremental time is set to 108000s according to actual requirements; the contact relationship is: Tie is used to connect the assemblies, and the convective heat transfer coefficient between the ceramic layer and the atmosphere is set to 0.1.

[0012] Furthermore, when dividing the mesh, the mesh type is a full two-dimensional quadrilateral mesh.

[0013] Furthermore, setting the material properties and cross-sectional characteristics in the finite element model includes the following steps: measuring the physical parameters of the ceramic layer, thermally grown oxide, bonding layer and high-temperature alloy matrix through experiments, and determining the material properties based on the physical parameters.

[0014] Further, material properties include elastic modulus, Poisson's ratio, direct expansion coefficient, thermal conductivity, specific heat capacity and density.

[0015] Furthermore, setting material properties and section characteristics in the finite element model includes the following steps: the section characteristics are regarded as solid homogeneity.

[0016] Furthermore, when a thermal cycle load is applied to the surface of the finite element model, the bottom surface of the finite element model is set to be completely fixed.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The analysis method of the present invention is simple. A finite element model with a high-temperature alloy as the substrate is established and coupled with the real thermal barrier coating structure. The sintering of the ceramic layer and the generation of hot metal oxides are considered in the finite element simulation process, and accurate simulation data can be obtained. In addition, local microscopic modeling is adopted to save computing resources and improve efficiency while ensuring accuracy. On the one hand, the present invention obtains the thermodynamic properties of the thermal barrier coating under real service conditions, and on the other hand, the service life of the coating is predicted by the expansion state of the crack, which has a guiding role in engineering applications. The analysis method of the present invention is simple, fits the real service conditions and microstructure, achieves the expected research effect for finite element simulation, and can obtain accurate simulation data. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a flow chart of the simulation analysis method of the present invention; Figure 2 It is a finite element mesh division diagram of the model of the present invention; Figure 3 is the thermal cycle load diagram of the present invention; Figure 4 This is the Odb result diagram of the temperature field after the thermal cycle of the present invention is completed; Figure 5This is the Odb result diagram of the stress field after the thermal cycle of the present invention is completed; Figure 6 This is the Odb result diagram of crack extension at the end of thermal cycling of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Example 1 See also Figure 1-Figure 6 The present invention is a method for simulating and analyzing crack propagation under cyclic load of thermal barrier coating based on real structure. The finite element software abaqus is selected, and the method includes three steps: pre-processing, solving and post-processing. The pre-processing mainly involves finite element modeling and meshing. The solving step is to calculate the built finite element model. The post-processing step is to analyze and process the calculation results.

[0021] The simulation analysis method of the present invention specifically comprises the following steps: A. Create a component in the Part of the finite element software abaqus; according to the laboratory thermal barrier coating sample (the thermal barrier coating sample includes a high-temperature alloy substrate SUB, a bonding layer BC, a thermal metal oxide TGO and a ceramic layer TC, the high-temperature alloy substrate SUB is the bonding layer BC, the bonding layer BC is the thermal metal oxide TGO, and the thermal metal oxide TGO is the ceramic layer TC) use the PYTHON programming language to create a finite element model, namely Part 1 (physical model), see Figure 2 In the present invention, the finite element model includes a high-temperature alloy substrate SUB, a bonding layer BC, a hot metal oxide TGO and a ceramic layer TC. The bonding layer BC is on the high-temperature alloy substrate SUB, the hot metal oxide TGO is on the bonding layer BC, and the ceramic layer TC is on the hot metal oxide TGO. Among them, the material selected for the high-temperature alloy is DD26, which is modeled as 250μm×50μm. The material properties are determined by experiments. The parameters are shown in Table 1. The unit types are shell units DC2D4 and CPS4R in the first and second jobs respectively.

[0022] The bonding layer BC is made of NiCrAlY. It is modeled as 250μm×20μm, where the interface between BC and TC is a sinusoidal wave interface, the interface includes a TGO layer, the material properties are determined by experiment, the parameters are shown in Table 2, and the unit types are shell units DC2D4 and CPS4R in the first and second jobs respectively.

[0023] The TGO layer is a thermal metal oxide, which is modeled as 250 μm×2 μm. The material properties are determined by experiments. The parameters are shown in Table 3. The unit types are shell units DC2D4 and CPS4R in the first and second jobs respectively.

[0024] The TC layer is a ScYSZ material, which is modeled as 250 μm×80 μm, with a model porosity of 5%. The material properties are determined experimentally, and the parameters are shown in Table 4. The interface between the TC layer and the BC layer is a sinusoidal TGO thermal metal oxide, and the unit types are shell units DC2D4 and CPS4R in the first and second jobs, respectively.

[0025] B. Define the material properties and cross-sectional characteristics in the finite element model in Property; measure the physical parameters of the ceramic layer, thermally grown oxide, bonding layer and substrate through experiments (see Table 1, Table 2, Table 3 and Table 4), and determine the material properties (elastic modulus, Poisson's ratio, positive expansion coefficient, thermal conductivity, specific heat capacity and density) based on the physical parameters. The cross-sectional characteristics are considered to be solid homogeneous.

[0026] Table 1 Physical properties of matrix DD26

[0027] Table 2 Physical properties of NiCrAlY bonding layer

[0028] Table 3 Physical properties of thermally grown oxides

[0029] Table 4 Physical properties of ceramic layer material ScYSZ

[0030] C. Define the assembly in Assembly; assemble the components to generate an assembly for finite element calculation.

[0031] D. Set the analysis step and variable output in Step; create analysis step Step1 in the Step function module, set the type to Heat transfer, the incremental step type to Automatic, the initial incremental step to 0.1, and the maximum incremental time to 108000s according to actual requirements.

[0032] E. Define the contact relationship in Interaction; use Tie to connect each assembly, set the convection heat transfer coefficient between the ceramic layer and the atmosphere to 0.1, and meet the convection conditions of the finite element model.

[0033] F. Apply load and boundary conditions in Load; apply the cyclic temperature load measured by infrared thermal imager in the real thermal cycle experiment to the surface of the ceramic layer, such as Figure 3 As shown, the bottom surface of the finite element model is set to be completely fixed.

[0034] G. Divide the mesh in Mesh; the mesh type is a full two-dimensional quadrilateral mesh with good quality. Figure 2 , and obtain a mesh model with boundary conditions.

[0035] H. Submit the job in Job and run the analysis. According to the grid model with boundary conditions in step G, analyze and obtain the thermal calculation result Odb file of the model. Figure 4 .

[0036] I. Copy the finite element model and perform thermal-mechanical coupling; copy Part 1 and change its name to Part 2.

[0037] J. Set the analysis step and variable output in Step; create analysis step Step2, set the type to Static / General, the increment step type to Automatic, and the initial increment to 0.01.

[0038] K. Set crack extension options; in the Interaction module, use the Crack option in the Special section, select the maximum principal stress criterion, and set the corresponding crack extension conditions.

[0039] L. Create boundary conditions for thermal coupling; in the Load function module, set the bottom surface of the finite element model to be completely fixed. In the analysis step Step 2, use the Odb file obtained in step H as the boundary condition in the predefined field.

[0040] M. Submit the calculation results of the Job, that is, obtain the results of thermal-mechanical coupling, that is, the thermal stress and crack extension after thermal cycling. The thermal stress results refer to Figure 5 , the crack growth results are shown in Figure 6 .

[0041] The present invention adopts a sequential coupling method, firstly, a physical model is constructed through step A, material parameters are set in step B, assembly parts are defined in step C, analysis steps are set in step D, contact relationships are specified in step E, loads and boundary conditions are applied through step F, and meshes are divided through step G, and the thermal load of the entire finite element model under thermal cycle conditions is calculated through step H; then, the entire thermal field is introduced into the microstructure field of the ceramic coating as an initial condition through step I; the analysis step is modified in step J; in step K, a crack initiation and propagation criterion is set through a method of extending the finite element by an extended finite element XFEM; new boundary conditions are set in step L; and finally, the thermal stress distribution and crack initiation and propagation process of the model are obtained in step M.

[0042] The present invention adopts a thermal-mechanical sequential coupling method to simulate the thermal cycle results, and adopts fixed boundary conditions to analyze the thermodynamics inside the coating structure. Therefore, the size of the selected area is very small, at the micron level, and the entire model is 250×50μm; at the same time, in order to save computing resources, a 2d method is adopted to establish a two-dimensional shell unit, and the crack propagation simulation is performed in step K through the XFEM extended finite element method, and a completely fixed constraint is adopted for the bottom of the high-temperature alloy substrate.

[0043] The meshing in the present invention is a key link in the finite element model. In general structural simulation, the number and quality of meshes directly affect the calculation results. Since the present invention utilizes the XFEM extended finite element method, only two-dimensional quadrilateral shell elements can be selected in the meshing process, and in order to save computing resources, the mesh is encrypted in the TC area where crack extension is required and the contact surface of the sinusoidal wave, while the mesh inside the matrix and the area with gentle stress can be relatively sparse, which can not only meet the accuracy requirements of the calculation results, but also take into account the calculation efficiency.

[0044] The analysis method of the present invention is simple, and a finite element model under thermal cycle conditions is constructed to achieve the expected research effect for finite element simulation, and accurate simulation data can be obtained.

[0045] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A crack propagation simulation analysis method based on real structure thermal barrier coating under cyclic load, characterized in that: The following steps are involved: Create a finite element model based on thermal barrier coating samples; Set material properties and cross-section characteristics in the finite element model; After setting the parameters, apply thermal cycle load to the surface of the finite element model, divide the mesh and analyze it to obtain the Odb file After copying the finite element model, the Odb file is used as the boundary condition to perform thermal-mechanical coupling to obtain the thermal stress and crack extension after thermal cycling.

2. The crack propagation simulation analysis method based on real structure thermal barrier coating under cyclic load according to claim 1 is characterized in that: The finite element model includes a high-temperature alloy substrate, a bonding layer, a hot metal oxide and a ceramic layer which are arranged in sequence from bottom to top.

3. The crack propagation simulation analysis method based on real structure thermal barrier coating under cyclic load according to claim 2 is characterized in that: The material of the high-temperature alloy matrix is ​​DD26, and the modeling is 250μm×50μm. The material properties are determined by experiments. The element types in the first and second jobs are shell elements DC2D4 and CPS4R respectively. The bonding layer material is NiCrAlY, and the modeling is 250μm×20μm, where the interface between the bonding layer and the ceramic layer is a sinusoidal wave interface. The material properties are determined by experiments, and the unit types are shell elements DC2D4 and CPS4R in the first and second jobs respectively; The thermal metal oxide is a thermal metal oxide, modeled as 250 μm × 2 μm, the material properties are determined experimentally, and the element types are shell elements DC2D4 and CPS4R in the first and second jobs, respectively; The ceramic layer is made of ScYSZ material and is modeled as 250μm×80μm, where the model porosity is 5%. The material properties are determined experimentally, and the unit types are shell elements DC2D4 and CPS4R in the first and second jobs, respectively.

4. The crack propagation simulation analysis method based on real structure thermal barrier coating under cyclic load according to claim 3 is characterized in that: Parameters include assembly parts, analysis steps, and variable output and contact relationships.

5. The crack propagation simulation analysis method based on real structure thermal barrier coating under cyclic load according to claim 4 is characterized in that: The specific analysis steps are as follows: the type is set to Heat transfer, the incremental step type is Automatic, the initial incremental step is 0.1, and the maximum incremental time is set to 108000s according to actual requirements; The contact relationship is: Tie is used to connect the assemblies, and the convection heat transfer coefficient between the ceramic layer and the atmosphere is set to 0.

1.

6. The crack propagation simulation analysis method based on real structure thermal barrier coating under cyclic load according to claim 1, characterized in that: When dividing the mesh, the mesh type is a full two-dimensional quadrilateral mesh.

7. The crack propagation simulation analysis method based on real structure thermal barrier coating under cyclic load according to claim 1, characterized in that: Setting material properties and cross-sectional characteristics in a finite element model includes the following steps: measuring physical property parameters of a ceramic layer, a thermally grown oxide, a bonding layer, and a high-temperature alloy substrate through experiments, and determining material properties based on the physical property parameters.

8. The crack propagation simulation analysis method based on real structure thermal barrier coating under cyclic load according to claim 7, characterized in that: Material properties include elastic modulus, Poisson's ratio, direct expansion coefficient, thermal conductivity, specific heat capacity, and density.

9. The crack propagation simulation analysis method based on real structure thermal barrier coating under cyclic load according to claim 1, characterized in that: Setting the material properties and cross-sectional characteristics in the finite element model includes the following steps: The cross-sectional characteristics are considered to be homogeneous solid.

10. The crack propagation simulation analysis method based on real structure thermal barrier coating under cyclic load according to claim 1, characterized in that: When applying thermal cycle loads to the surface of the finite element model, the bottom surface of the finite element model is set to be completely fixed.

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