Plastic equivalence and simplification method for dense exhaust film holes of engine turbine blade

Abstract

The invention provides a plasticity equivalence and simplification method for a dense exhaust film hole of an engine turbine blade. The plasticity equivalence and simplification method comprises the steps that whether a model is a dense exhaust film hole nickel-based single crystal turbine blade model or not is determined; if yes, a nickel-based single crystal alloy plasticity constitutive equation based on the crystal plasticity theory is determined, the air film hole density of the dense exhaust air film hole nickel-based single crystal blade model is determined according to the arrangement modes of air film holes, an air film hole density function is introduced, and a plasticity stress deformation expression in each arrangement mode is determined; determining that the arrangement mode of the air film holes is triangular arrangement or quadrilateral arrangement, and simplifying the whole blade into an equivalent model containing a small number of air film holes according to the simplification mode of the air film holes in the triangular arrangement or quadrilateral arrangement; plastic equivalent parameters are determined according to the principle that the plastic strains are the same under the same load and temperature for the same time; and substituting corresponding plastic equivalent parameters into the equivalent model for calculation so as to realize plastic equivalence and simplified calculation of the dense exhaust film hole of the turbine blade of the engine.

Description

Technical Field

[0001] The present disclosure relates to the technical field of aero-engines, and in particular to a plastic equivalence and simplification method for dense exhaust film holes of engine turbine blades. Background Art

[0002] As one of the main components of aircraft engines, turbine blades play a decisive role in the overall performance of the engine to some extent. In order to increase the turbine inlet temperature and ensure the reliability of turbine blades working in high temperature environments, the application of turbine blade cooling technology is becoming more and more extensive. Nickel-based single crystal high-temperature alloy materials contain only one grain, eliminating the influence of grain boundaries. Compared with equiaxed crystals and oriented columnar crystals, they have higher strength, life and elongation, which can significantly improve the structural strength and life of turbine cooling blades. At the same time, they have excellent comprehensive properties such as high temperature resistance, corrosion resistance, oxidation resistance, good thermal shock performance, and stable organization. They are the preferred material for turbine cooling blades.

[0003] Turbine cooling blades are often designed with a large number of film holes to improve cooling efficiency. While the cooling efficiency is improved, the presence of film holes damages the continuity of the turbine blade material and structure, changes the stress strain field and surface state of the local area of ​​the film holes, and to some extent leads to a reduction in the blade structural strength and life. Since the film holes on the cooling blades have small apertures and dense arrangement, it is difficult to mesh the film holes when performing finite element calculations, which brings great difficulties to the blade structural strength analysis and life design.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] The purpose of the embodiments of the present disclosure is to provide a plastic equivalent and simplified method for sealing exhaust film holes of engine turbine blades.

[0006] Other features and advantages of the present disclosure will become apparent from the following detailed description, or may be learned in part by the practice of the present disclosure.

[0007] According to one aspect of an embodiment of the present disclosure, a plastic equivalent and simplified method for sealing exhaust film holes of an engine turbine blade is provided, comprising:

[0008] Determine whether the model is a nickel-based single crystal turbine blade model with dense exhaust film holes;

[0009] If so, determine the plastic constitutive equation of nickel-based single crystal alloy based on crystal plasticity theory, determine the density of film holes of the nickel-based single crystal blade model with densely packed film holes according to the arrangement of film holes, and introduce the film hole density function to determine the plastic strain expression under each arrangement;

[0010] Determine that the arrangement of the film holes is a triangular arrangement or a quadrilateral arrangement, and simplify the entire blade into an equivalent model containing a small number of film holes according to the simplified method of the film holes under the triangular arrangement or the quadrilateral arrangement;

[0011] According to the principle that the plastic strain is the same at the same load and temperature for the same time, the plastic equivalent parameters are determined;

[0012] The corresponding plastic equivalent parameters are substituted into the equivalent model for calculation to realize the plastic equivalence and simplified calculation of the dense exhaust film holes of the engine turbine blades.

[0013] In an exemplary embodiment of the present disclosure, the plastic equivalent parameters are obtained by parameter inversion, including:

[0014] Establishing a calculation model, including selecting a unit cell model from a dense air film hole model, and using an equivalent solid model of the unit cell model as a calculation model;

[0015] The optimization parameters are the elastic-plastic constitutive parameters and the shear strain rate. and strain rate sensitivity index m;

[0016] The numerical simulation results of the equivalent solid model include stress S, strain E, displacement U and state variable SDV. The strain values ​​of a preset number of specific stress points on the average stress-strain curve of the unit cell model are selected as test values.

[0017] Integrate the calculation model, optimization parameters and optimization objectives into the optimization control program of the optimization controller;

[0018] The optimization controller optimizes the parameters according to the defined optimization algorithm. The initial values ​​of and m are submitted to the calculation model, and the average strain of the equivalent solid model is obtained after calculation. The average strain of the equivalent solid model is compared with the average strain of the unit cell model. If the optimization target is not reached, the optimization controller will give a new set of optimization parameters and repeat the above calculation process. This process is repeated until the optimization target is reached, and the optimization parameters at this time are the target optimization parameters.

[0019] In an exemplary embodiment of the present disclosure, the objective function is:

[0020]

[0021] Where: max(abs(ε t(i)),abs(ε c (i)))≠0, ε t (i) is the experimental value selected from the average stress-strain curve of the unit cell model, ε c (i) is the average strain value of the equivalent solid model at the same stress point; when f is the smallest, the error between the average strain value of the equivalent solid model and the unit cell model is the smallest.

[0022] In an exemplary embodiment of the present disclosure, the elastic-plastic parameter inversion of nickel-based single crystal material is automatically implemented by integrating Abaqus batch processing files with Isight, including:

[0023] A single cell model and a 1 / 2 model of the equivalent solid model are established in Abaqus. The material properties and elastic-plastic constitutive parameters are imported into Abaqus through the user subroutine test.for. After meshing, setting loads and boundary conditions, the equivalent solid model is submitted to obtain the Job-test.inp file.

[0024] Write the Abaqus batch file test.bat and the post-processing file test.py to call the Job-test.inp file and the Job-test.odb file to implement Abaqus automatic calculation and post-processing, and generate the output file test.txt to store the average strain of a specific frame in the analysis step;

[0025] Isight is used to perform elastic-plastic parameter inversion, and the Simcode program is used to integrate the application input, execution, and output: the input file is the user subroutine test.for, the execution application is the Abaqus batch file test.bat, and the output file is test.txt;

[0026] Use Task Plan component to achieve parameter optimization: the optimization parameters are elastic-plastic constitutive parameters and m, the optimization objective is to minimize the sum of squares of relative errors between the equivalent solid model and the average strain of the unit cell model, and the optimization algorithms are multi-island genetic algorithm and sequential quadratic programming.

[0027] In an exemplary embodiment of the present disclosure, corresponding to the triangular arrangement and the quadrilateral arrangement, the trend of f(η) changing with the pore density is calculated by the air film pore density function; f(η) is an unknown function about η:

[0028]

[0029] Wherein, μ is the Poisson's ratio of the nickel-based single crystal alloy material, and μ=0.3.

[0030] In an exemplary embodiment of the present disclosure, a unit cell model is selected from the entire plate according to the periodicity and symmetry of the hole arrangement, and the unit cell model is equivalent to a solid material. The equivalent models of different hole arrangements are different, and the unit cell model is regarded as an equivalent solid model with equivalent elastic constants.

[0031] In an exemplary embodiment of the present disclosure, the equivalent solid model retains the middle hole to analyze the stress state around the hole, and the positions of the remaining holes are replaced by equivalent solid materials.

[0032] In an exemplary embodiment of the present disclosure, the thinner region in the equivalent solid model is calculated using the elastic constant variation relationship under the plane stress state, and the thicker region is calculated using the generalized plane strain state.

[0033] In an exemplary embodiment of the present disclosure, the air film pore density η of a nickel-based single crystal blade model containing dense air film pores is calculated, and the air film pore density function f(η) is introduced to derive the equivalent formula of plastic parameters under various states;

[0034] Among them, the definition parameters It reflects the distribution density of holes, h is the shortest distance between two holes, and p is the distance between the centers of the two holes.

[0035] In an exemplary embodiment of the present disclosure, the total deformation gradient F of the material is decomposed into an elastic part F e and plastic part F P :

[0036] F=F e F P

[0037] Among them, F e Related to the elastic distortion and rigid body rotation of the lattice, F P Slip deformation caused by dislocation motion in an intermediate configuration without distortion; F P The evolution rate is:

[0038]

[0039] Among them, L P The velocity gradient of plastic deformation is given by the shear strain rate on all active slip systems Superposition:

[0040]

[0041] Among them, m (α) and n (α) is the slip direction of slip system α and the unit vector of the normal line of the slip surface, N is the number of slip systems;

[0042] The relationship between the shear stress and macroscopic stress of the slip system is:

[0043] τ (α) =σ:P (α)

[0044] Among them, τ (α) is the shear stress of each slip, P (α) is the orientation factor, σ is the stress tensor under the crystal axis system;

[0045] Orientation factor P (α) Defined as:

[0046]

[0047] Among them, m (α) represents the slip direction of the αth slip system in the initial configuration, n (α) represents the unit normal vector of the slip plane of the αth slip system in the initial configuration;

[0048] Shear strain rate for each slip system α It is represented by a rate-dependent power function equation:

[0049]

[0050] in, is called the reference shear strain rate, is the critical shear stress, m is the strain rate sensitivity index;

[0051] The evolution of the critical shear stress of the slip system conforms to the following hardening law:

[0052]

[0053] Among them, h αβ It is called the hardening coefficient, which determines the hardening caused by the slip shear in slip system β on slip system α; h αβ It can be determined by the following formula:

[0054] h αβ =q αβ h β

[0055] Among them, q αβ is the matrix describing latent hardening, h β is the single slip hardening rate; where the hardening rate is:

[0056]

[0057] Where h0 is the hardening modulus, τ s and a are model parameters.

[0058] The present invention provides a plastic equivalence and simplification method for dense air film holes in engine turbine blades. Taking into account the plastic deformation characteristics of nickel-based single crystal alloys, a plastic equivalence and simplification method is proposed for the relatively common quadrilateral and triangular dense air film hole arrangements in engineering. The dense air film hole model is simplified into an equivalent model with a single air film hole, and then the entire turbine cooling blade model is simplified into an equivalent model with a very small number of air film holes and an equivalent transformation relationship with corresponding plastic parameters is given. Under the premise of satisfying the same plastic strain under the same load and temperature, the equivalent model is used instead of the original model to perform finite element analysis within the plastic range, which can greatly reduce the calculation amount of the turbine cooling blade with dense air film holes and obtain accurate plastic deformation and damage distribution.

[0059] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present disclosure, and together with the specification, are used to explain the principles of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0061] Figure 1 A flow chart of a plastic equivalent and simplified method for sealing exhaust film holes of an engine turbine blade provided by an embodiment of the present disclosure;

[0062] Figure 2 A schematic diagram of a quadrilateral arrangement of air film holes provided in an embodiment of the present disclosure;

[0063] Figure 3 A schematic diagram of a triangular arrangement of air film holes provided in an embodiment of the present disclosure;

[0064] Figure 4 A schematic diagram of boundary conditions for quadrilateral arrangement of air film holes provided in one embodiment of the present disclosure;

[0065] Figure 5 A schematic diagram of boundary conditions for a triangular arrangement of air film holes provided in one embodiment of the present disclosure;

[0066] Figure 6 A schematic diagram of a test value obtained by measuring eight specific stress points on an average stress-strain curve of a unit cell model provided by an embodiment of the present disclosure;

[0067] Figure 7 An elastic-plastic parameter inversion process of a nickel-based single crystal material provided by an embodiment of the present disclosure;

[0068] Figure 8 An Isight integrated optimization process provided for an embodiment of the present disclosure;

[0069] Fig. 9 The relationship between the quadrilateral arrangement f(η) of the air film holes and the hole distribution density η provided in one embodiment of the present disclosure;

[0070] Fig.10 The relationship between the triangular arrangement f(η) of the air film holes and the hole distribution density η provided in one embodiment of the present disclosure;

[0071] Fig.11 A schematic diagram of a flat plate model of densely packed air film holes arranged in a quadrilateral pattern provided by an embodiment of the present disclosure;

[0072] Fig.12 for Fig.11 A partial enlarged view of the middle A part;

[0073] Fig.13 A schematic diagram of a flat plate model of densely packed air film holes arranged in a triangular pattern provided by an embodiment of the present disclosure;

[0074] Fig.14 for Fig.13 A partial enlarged view of the middle B part;

[0075] Fig.15 A unit cell model of quadrilateral arrangement of air film holes provided in one embodiment of the present disclosure;

[0076] Fig.16 An equivalent solid model of a quadrilateral arrangement of air film holes provided in one embodiment of the present disclosure;

[0077] Fig.17 A unit cell model of triangular arrangement of air film holes provided in one embodiment of the present disclosure;

[0078] Fig.18 An equivalent solid model of a triangular arrangement of air film holes provided in one embodiment of the present disclosure;

[0079] Fig.19 An equivalent flat plate model of quadrilateral arrangement of air film holes provided in one embodiment of the present disclosure;

[0080] Fig. 20 for Fig.19 The equivalent plate model retains the middle hole to analyze the stress state around the hole, and the remaining holes are replaced by equivalent solid materials. The enlarged view of part C;

[0081] Fig.21 An equivalent flat plate model of triangular arrangement of air film holes provided in one embodiment of the present disclosure;

[0082] Fig. 22 for Fig.21 The equivalent plate model retains the middle hole to analyze the stress state around the hole, and the remaining holes are replaced by equivalent solid materials. The enlarged view of part D;

[0083] Fig.23 An equivalent front stress-strain curve when the hole distribution density of the quadrilateral arrangement of the air film holes provided in one embodiment of the present disclosure is 0.4;

[0084] Fig.24 An equivalent post-stress strain curve when the hole distribution density of the quadrilateral arrangement of the air film holes provided in one embodiment of the present disclosure is 0.4;

[0085] Fig.25 An equivalent front stress-strain curve when the hole distribution density of the quadrilateral arrangement of the air film holes provided in one embodiment of the present disclosure is 0.6;

[0086] Fig.26 An equivalent post-stress strain curve when the hole distribution density of the quadrilateral arrangement of the air film holes provided in one embodiment of the present disclosure is 0.6;

[0087] Fig. 27 An equivalent front stress-strain curve when the hole distribution density of the quadrilateral arrangement of the air film holes provided in one embodiment of the present disclosure is 0.8;

[0088] Fig.28 An equivalent post-stress strain curve when the hole distribution density of the quadrilateral arrangement of the air film holes provided in one embodiment of the present disclosure is 0.8;

[0089] Fig.29 An equivalent front stress-strain curve when the hole distribution density of the triangular arrangement of air film holes provided in one embodiment of the present disclosure is 0.4;

[0090] Fig.30 The equivalent post-stress strain curve when the hole distribution density of the triangular arrangement of the air film holes provided in one embodiment of the present disclosure is 0.4;

[0091] Fig.31 An equivalent front stress-strain curve when the hole distribution density of the triangular arrangement of air film holes provided in one embodiment of the present disclosure is 0.6;

[0092] Fig.32 An equivalent post-stress strain curve when the hole distribution density of the triangular arrangement of air film holes provided in one embodiment of the present disclosure is 0.6;

[0093] Fig.33 An equivalent front stress-strain curve when the hole distribution density of the triangular arrangement of air film holes provided in one embodiment of the present disclosure is 0.8;

[0094] Fig.34 An equivalent post-stress strain curve when the hole distribution density of the triangular arrangement of air film holes provided in an embodiment of the present disclosure is 0.8. DETAILED DESCRIPTION

[0095] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be more comprehensive and complete and will fully convey the concept of the example embodiments to those skilled in the art.

[0096] In addition, the described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known methods, devices, implementations or operations are not shown or described in detail to avoid blurring the various aspects of the present disclosure.

[0097] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0098] At present, film holes are densely arranged on turbine cooling blades, with small apertures and large numbers, making it difficult to divide the mesh when performing finite element analysis of cooling blades, which has caused great difficulties in blade structural strength analysis and life prediction. When establishing the finite element model of the actual blade, film cooling holes are generally not made, and the stress at the hole edge is corrected by the stress concentration factor (usually 3), and the calculated results are not very accurate; the equivalence of film holes is mainly applicable to the elastic stage, while blades often undergo plastic deformation due to the combined effects of centrifugal force and thermal stress under actual working conditions, and the current equivalent method is not applicable; and the more common arrangements of dense film holes on turbine cooling blades in engineering are mainly quadrilateral arrangement and triangular arrangement. A single equivalent and simplified method cannot meet all situations.

[0099] In view of the above technical problems, the embodiments of the present disclosure provide a plastic equivalent and simplified method for sealing exhaust film holes of engine turbine blades, such as Figure 1 As shown in the figure, the plastic equivalent and simplified method of the dense exhaust film hole of the engine turbine blade includes:

[0100] Step S100, determining whether the model is a nickel-based single crystal turbine blade model with dense exhaust film holes;

[0101] Step S200: If yes, determine the plastic constitutive equation of the nickel-based single crystal alloy based on the crystal plasticity theory, determine the density of the film holes of the nickel-based single crystal blade model with densely packed film holes according to the arrangement of the film holes, and introduce the film hole density function to determine the plastic strain expression under each arrangement;

[0102] Step S300, determining that the arrangement of the film holes is a triangular arrangement or a quadrilateral arrangement, and simplifying the entire blade into an equivalent model containing a small number of film holes according to the simplified arrangement of the film holes under the triangular arrangement or the quadrilateral arrangement;

[0103] Step S400, determining plastic equivalent parameters according to the principle that the plastic strain at the same time under the same load and temperature is the same;

[0104] Step S500: Substitute corresponding plastic equivalent parameters into the equivalent model for calculation to achieve plastic equivalence and simplified calculation of the dense exhaust film holes of the engine turbine blades.

[0105] The present invention provides a plastic equivalence and simplification method for dense air film holes in engine turbine blades. Taking into account the plastic deformation characteristics of nickel-based single crystal alloys, a plastic equivalence and simplification method is proposed for the relatively common quadrilateral and triangular dense air film hole arrangements in engineering. The dense air film hole model is simplified into an equivalent model with a single air film hole, and then the entire turbine cooling blade model is simplified into an equivalent model with a very small number of air film holes and an equivalent transformation relationship with corresponding plastic parameters is given. Under the premise of satisfying the same plastic strain under the same load and temperature, the equivalent model is used instead of the original model to perform finite element analysis within the plastic range, which can greatly reduce the calculation amount of the turbine cooling blade with dense air film holes and obtain accurate plastic deformation and damage distribution.

[0106] Below, each step of the plastic equivalence and simplification method for sealing exhaust film holes of engine turbine blades provided by the present invention will be described in detail.

[0107] First, determine whether the model is a nickel-based single crystal turbine blade model containing dense exhaust film holes. If so, equivalent and simplified calculations can be performed according to the present disclosure.

[0108] The air film pore density η of the nickel-based single crystal blade model with dense air film pores is calculated, and the air film pore density function f(η) is introduced to derive the equivalent formula of plastic parameters under various states, where:

[0109] Defining parameters Reflects the distribution density of holes. Figure 2 and Figure 3As shown, h is the shortest distance between the two holes, p is the distance between the centers of the two holes, and the values ​​of h and p are constants, which are obtained by measuring the arrangement of film holes on turbine blades in actual engineering.

[0110] The total deformation gradient F of the material is decomposed into two parts, namely the elastic part F e and plastic part F P :

[0111] F=F e F P

[0112] Among them, F e is related to the elastic distortion and rigid body rotation of the lattice, while F P It is attributed to the slip deformation caused by dislocation movement in the intermediate configuration without distortion. P The evolution rate is:

[0113]

[0114] Among them, L P The velocity gradient representing plastic deformation is given by the shear strain rate on all active slip systems. Superposition:

[0115]

[0116] Among them, m (α) and n (α) is the slip direction of slip system α and the unit vector of the slip surface normal, and N is the number of slip systems.

[0117] The relationship between the shear stress and macroscopic stress of the slip system can be expressed as:

[0118] τ (α) =σ:P (α)

[0119] Among them, τ (α) is the shear stress of each slip, P (α) is the orientation factor, and σ is the stress tensor under the crystal axis system.

[0120] Orientation factor P (α) is defined as:

[0121]

[0122] Among them, m (α) represents the slip direction of the αth slip system in the initial configuration, n (α) represents the unit normal vector of the slip plane of the αth slip system in the initial configuration.

[0123] In general, the shear strain rate of each slip system α is It is represented by a rate-dependent power function equation:

[0124]

[0125] in, is called the reference shear strain rate, is the critical shear stress, and m is the strain rate sensitivity index.

[0126] The evolution of the critical shear stress of the slip system conforms to the following hardening law:

[0127]

[0128] Among them, h αβ It is called the hardening coefficient, which determines the hardening caused by the slip shear in slip system β on slip system α.

[0129] h αβ It can be determined by the following formula:

[0130] h αβ =q αβ h β

[0131] Among them, q αβ is the matrix describing latent hardening, h β is the single slip hardening rate, and the hardening rate used in this disclosure is:

[0132]

[0133] Where h0 is the hardening modulus, τ s and a are model parameters.

[0134] The plastic equivalent parameters are obtained by parameter inversion. The methods for inversion of plastic parameters of nickel-based single crystal materials include:

[0135] (1) Establishing a calculation model: Selecting a unit cell model from the dense gas-filled membrane hole model, and using the equivalent solid model of the unit cell model as the calculation model; the dense gas-filled membrane hole flat plate model and its equivalent single hole flat plate model used in the present disclosure are shown in 11~ Fig.14 and Figure 19 to Figure 22 As shown, the unit cell model and the equivalent entity model are as follows Figure 15 to Figure 18 As shown, the boundary conditions are Figure 4 and Figure 5 As shown, y-direction displacement coordination is performed at the top and bottom of the model, for quadrilateral arrangement, x-direction displacement coordination is performed on the right side of the model, and for triangular arrangement, x-direction displacement coordination is performed on the intersection of the two planes on the right side of the model.

[0136] Define optimization parameters: Optimization parameters are elastic-plastic constitutive parameters and m;

[0137] Define the optimization goal: The numerical simulation results of the equivalent solid model generally include stress S, strain E, displacement U and state variable SDV. Considering the optimization efficiency, the strain values ​​of a finite number of specific stress points on the average stress-strain curve of the unit cell model are selected as the test values. Taking the quadrilateral arrangement hole distribution density of 0.4 as an example, according to the change trend of the curve, the strain values ​​at 8 specific stress points are selected as the measured test values, such as Figure 4 In order to make the equivalent single-hole plate model accurately reflect the mechanical properties of the air-tight film hole plate model, the optimization goal is to minimize the sum of squares of the relative errors between the average strain value of the equivalent solid model at the same stress point and the experimental value selected on the average stress-strain curve of the unit cell model. The objective function is:

[0138]

[0139] Where: max(abs(ε t (i)),abs(ε c (i)))≠0, ε t (i) is the experimental value selected from the average stress-strain curve of the unit cell model, ε c (i) is the average strain value of the equivalent solid model at the same stress point, such as Figure 6 As shown in , when f is the smallest, the error between the average strain value of the equivalent solid model and the unit cell model is the smallest. Figure 6 In the figure, Stress-strain curve represents stress-strain curve, Test values ​​represent test values, the vertical coordinate Stress represents stress, and the horizontal coordinate Strain represents strain.

[0140] (4) Integrate the calculation model, optimization parameters and optimization objectives into the optimization control program;

[0141] (5) The optimization controller optimizes the parameters according to the defined optimization algorithm. The initial values ​​of and m are submitted to the calculation model. After calculation, the average strain of the equivalent solid model is obtained, which is compared with the average strain of the unit cell model. If the optimization target is not achieved, the optimization controller will give a new set of optimization parameters and repeat the above calculation process. This process is repeated until the optimization target is achieved. The optimization parameters at this time are the expected optimization parameters.

[0142] The inversion process of elastic-plastic parameters of nickel-based single crystal materials is as follows Figure 7 shown.

[0143] The elastic-plastic parameter inversion of nickel-based single crystal materials is automatically realized by integrating Abaqus batch processing files with Isight. The specific process is as follows:

[0144] (1) Establish a unit cell model and a 1 / 2 model of the equivalent solid model in Abaqus. The material properties and elastic-plastic constitutive parameters are imported into Abaqus through the user subroutine test.for. After meshing, setting the load and boundary conditions, submit the equivalent solid model to obtain the Job-test.inp file.

[0145] (2) Write the Abaqus batch processing file test.bat and the post-processing file test.py to call the Job-test.inp file and the Job-test.odb file to implement Abaqus automatic calculation and post-processing, and generate the output file test.txt to store the average strain of a specific frame in the analysis step;

[0146] (3) Use Isight to perform elastic-plastic parameter inversion, and use Simcode program to integrate application input, execution, and output: the input file is the user subroutine test.for, the execution application is the Abaqus batch file test.bat, and the output file is test.txt. Use Task Plan component to achieve parameter optimization: The optimization parameters are elastic-plastic constitutive parameters and m, the optimization objective is to minimize the sum of squares of relative errors between the equivalent solid model and the average strain of the unit cell model. The optimization algorithms are multi-island genetic algorithm (MIGA) and sequential quadratic programming method (NLPQL). The combination of these two algorithms not only gives play to the advantage of the global optimization algorithm in locating the target area in the overall space, but also reflects the efficiency of the gradient optimization algorithm in accurately optimizing the target area.

[0147] The process of Isight integrated optimization is to find the optimization parameters according to the defined algorithm to minimize the sum of squares of the relative errors between the average strain in the output file test.txt and the average strain of the unit cell model. The optimization process is as follows: Figure 8 shown.

[0148] Corresponding to the two arrangements, the trend of f(η) changing with pore density was obtained by calculating the air film pore density function.

[0149] f(η) is an unknown function about η:

[0150]

[0151] in, μ H The relationship between μ and η is shown in Table 1, where μ is the Poisson's ratio of the nickel-based single crystal alloy material, and μ=0.3.

[0152] Table 1 Elastic constant values ​​under quadrilateral and triangular arrangements

[0153]

[0154] According to the expression As well as the values ​​in the table, the value of f(η) can be calculated, and based on these values, the variable relationship curve of f(η) and η in quadrilateral arrangement and triangular arrangement can be fitted using Matlab software.

[0155] For the quadrilateral arrangement, the fitting result of f(η) is as follows Fig. 9 shown.

[0156] For the triangular arrangement, the fitting result of f(η) is as follows Fig.10 shown.

[0157] Determine the arrangement of the densely packed vent holes on the blade and simplify it according to the following equivalent model.

[0158] The number of holes in the following model is based on the number of film holes in commercial blades. The distribution of holes is consistent with the distribution of film cooling holes in commercial cooling blades. The size of the plate is calculated based on the formula and can be adjusted according to the actual engineering calculation. There are multiple groups of quadrilateral or triangular film holes in the blade. Here, one group is taken as an example for simplification.

[0159] The flat plate model with airtight vent holes is as follows: Figure 11 to Figure 14 As shown, the quadrilateral arrangement model contains 150 holes and the triangular arrangement model contains 171 holes. The plate 10 in the figure is 35 mm long and 6 mm wide. The three-dimensional plate model is used for numerical simulation. The spacing p between the holes in this patent is 1. In fact, the value of p is selected based on literature and the optimal spacing between holes in engineering. Readers can also choose other values. For different hole distribution densities η, the pore size d is different. The relationship between pore size and pore distribution density is:

[0160] d=1-η

[0161] According to the periodicity and symmetry of the arrangement of the holes 100, a unit cell model is selected from the entire plate 10, and the unit cell model is equivalent to a solid material. The equivalent models of different arrangements of the holes 100 are different. The equivalent principles of the quadrilateral arrangement and the triangle arrangement models are as follows: Figure 15 to Figure 18 As shown, the unit cell model is considered as an equivalent solid model with equivalent elastic constants.

[0162] Considering the anisotropic characteristics of nickel-based single crystal materials, in order to analyze the mechanical properties of turbine blades in service, the authors retained the middle hole in the equivalent plate model to analyze the stress state around the hole, and the positions of the remaining holes were replaced by equivalent solid materials, such as Figure 19 to Figure 22As shown, it can not only simplify the difficulty of meshing in finite element simulation, but also directly analyze the air film holes when calculating the strength and life of nickel-based single crystal cooling blades. Note: The dense air film hole model is simplified to an intermediate single hole model, which is used to analyze the circumferential stress state of the intermediate hole under multi-void interference. Readers can select the position of the single hole according to their own situation. It can be selected in the middle to analyze the stress state of the hole under multi-void interference, or it can be selected on the corners. However, if it is selected on the corners, it is impossible to analyze the stress state of the hole under multi-void interference of the surrounding holes. In addition, the relationship between the intermediate hole and the center line is determined according to the position of the center line of the dense air film hole plate, and there is no variable relationship.

[0163] The thinner area in the equivalent blade model is calculated using the elastic constant change relationship under the plane stress state, and the thicker area is calculated using the generalized plane strain state. The transformation formula and the air film pore density function value are provided by steps 2 and 3.

[0164] Among them, Abaqus was used to calculate the directional solidification nickel-based single crystal alloy dense gas film hole plate and equivalent single hole plate model, and their plastic properties were analyzed. By comparing the stress-strain curves of the plate model under different states, the rationality of the equivalent plastic parameter calculation method has been verified.

[0165] Fig.23 and Fig.24 The figure shows the stress-strain curve comparison before and after the equivalent when the distribution density of the quadrilateral arrangement holes is 0.4; Fig.26 and Fig.26 The figure shows the stress-strain curve comparison before and after the equivalent when the distribution density of the quadrilateral arrangement holes is 0.6; Fig. 27 and Fig.28 The figure shows the stress-strain curve comparison before and after the equivalent arrangement of quadrilateral holes with a distribution density of 0.8. Figure 23 to Figure 34 In the figure, Unit cell model represents the unit cell model, Equivalent solid model represents the equivalent solid model, the vertical coordinate Stress represents stress, the horizontal coordinate Strain represents strain, the Plate model represents the plate model, and the Simplification model represents the equivalent model.

[0166] Fig.29 and Fig.30 The figure shows the stress-strain curve comparison before and after the equivalent when the distribution density of the triangular arrangement holes is 0.4; Fig.31 and Fig.32 The figure shows the stress-strain curve comparison before and after the equivalent when the distribution density of the triangular arrangement holes is 0.6; Fig.33 and Fig.34The figure shows the stress-strain curve comparison before and after the equivalent when the distribution density of triangular holes is 0.8. The stress-strain curve calculated based on the equivalent single-hole flat plate model is not much different from the real stress-strain curve of the densely packed air film hole flat plate model, indicating that the proposed air film hole equivalent method can achieve the equivalence of the model well.

[0167] The equivalent and simplified method disclosed in the present invention takes into account the plasticity and anisotropy of nickel-based single crystal materials when simplifying the plastic parameters of materials, which is more in line with reality than the existing method of approximating the material as an isotropic material; an air film pore density function is introduced to effectively characterize the distribution of air film pores; according to the plasticity and anisotropy characteristics, an equivalent method of the plasticity constitutive model based on the parameter inversion method and equivalent plastic parameters are proposed; the simplified method containing dense air film pores takes into account its feasibility and accuracy for the strength and life calculation of nickel-based single crystal cooling blades; for the specific arrangement methods of dense air film pores (quadrilateral arrangement and triangular arrangement), equivalent single hole simplified models are proposed respectively, which greatly improves the accuracy of the calculation results.

[0168] Nickel-based single crystal: Nickel-based single crystal superalloys are the main materials for turbine blades of advanced aircraft engines and industrial gas turbines. Single crystal superalloys are widely used in turbine blades and other components of advanced propulsion systems such as turbine engines due to their high high temperature strength, excellent creep and fatigue resistance, good oxidation resistance, thermal corrosion resistance, structural stability and reliability. Single crystal superalloys eliminate grain boundaries and significantly reduce grain boundary strengthening elements that reduce the melting point, which increases the initial melting temperature of the alloy and enables solution treatment at a higher temperature range. Their strength is significantly higher than that of equiaxed crystals and oriented columnar crystal superalloys, and therefore they have been widely used.

[0169] Turbine blades: Turbine blades of aircraft engines are regarded as the heart of aircraft engines and determine the performance of aircraft. Turbine blades are installed behind the combustion chamber. Improving the thrust of aircraft engines mainly depends on the working condition of the turbine. Most turbine blades are cast blades, which are processed into finished blades by precision casting and machining. They are divided into high-pressure turbine blades and low-pressure turbine blades. They have the characteristics of complex surface, special materials, thin walls, and air film holes. The working conditions of the blades are harsh, and they need to be resistant to high temperature, corrosion, and high strength.

[0170] Film holes: Cooling technologies for advanced gas turbines include film cooling, impingement cooling, divergent cooling, and internal enhanced convection cooling. Film cooling is a common cooling method for high-temperature components of gas turbines. The cooling air is extracted from the compressor and first enters the hollow turbine blades to form internal cooling. The cooling air is injected into the mainstream outside the blades at a certain flow angle, forming a layer of air film on the surface of the blades, isolating the high-temperature gas from the wall surface and taking away part of the heat load of the wall surface. Film holes are processed on the leading edge of the turbine blades, the blade body surface, and other parts for film cooling of the turbine blades. The hole diameter is generally 0.2 to 0.8 mm.

[0171] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present disclosure are indicated by the following claims.

[0172] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A plastic equivalent and simplified method for sealing film holes of engine turbine blades, characterized in that: include: Determine whether the model is a nickel-based single crystal turbine blade model with dense exhaust film holes; If so, determine the plastic constitutive equation of nickel-based single crystal alloy based on crystal plasticity theory, determine the density of film holes of the nickel-based single crystal blade model with densely packed film holes according to the arrangement of film holes, and introduce the film hole density function to determine the plastic strain expression under each arrangement; Determine that the arrangement of the film holes is a triangular arrangement or a quadrilateral arrangement, and simplify the entire blade into an equivalent model containing a small number of film holes according to the simplified method of the film holes under the triangular arrangement or the quadrilateral arrangement; According to the principle that the plastic strain is the same at the same load and temperature for the same time, the plastic equivalent parameters are determined; The corresponding plastic equivalent parameters are substituted into the equivalent model for calculation to realize the plastic equivalence and simplified calculation of the dense exhaust film holes of the engine turbine blades.

2. The plastic equivalence and simplification method according to claim 1, characterized in that: The plastic equivalent parameters are obtained by parameter inversion, including: Establishing a calculation model, including selecting a unit cell model from a dense air film hole model, and using an equivalent solid model of the unit cell model as a calculation model; The optimization parameters are the elastic-plastic constitutive parameters and the shear strain rate. and strain rate sensitivity index m; The numerical simulation results of the equivalent solid model include stress S, strain E, displacement U and state variable SDV. The strain values ​​of a preset number of specific stress points on the average stress-strain curve of the unit cell model are selected as test values. Integrate the calculation model, optimization parameters and optimization objectives into the optimization control program of the optimization controller; The optimization controller optimizes the parameters according to the defined optimization algorithm. The initial values ​​of and m are submitted to the calculation model, and the average strain of the equivalent solid model is obtained after calculation. The average strain of the equivalent solid model is compared with the average strain of the unit cell model. If the optimization target is not reached, the optimization controller will give a new set of optimization parameters and repeat the above calculation process. This process is repeated until the optimization target is reached, and the optimization parameters at this time are the target optimization parameters.

3. The plastic equivalence and simplification method according to claim 2, characterized in that: The objective function is: Where: max(abs(ε t (i)),abs(ε c (i)))≠0, ε t (i) is the experimental value selected from the average stress-strain curve of the unit cell model, ε c (i) is the average strain value of the equivalent solid model at the same stress point; when f is the smallest, the error between the average strain value of the equivalent solid model and the unit cell model is the smallest.

4. The plastic equivalence and simplification method according to claim 2, characterized in that: The elastic-plastic parameter inversion of nickel-based single crystal materials is automatically realized by integrating Abaqus batch files with Isight, including: A single cell model and a 1 / 2 model of the equivalent solid model are established in Abaqus. The material properties and elastic-plastic constitutive parameters are imported into Abaqus through the user subroutine test.for. After meshing, setting loads and boundary conditions, the equivalent solid model is submitted to obtain the Job-test.inp file. Write the Abaqus batch file test.bat and the post-processing file test.py to call the Job-test.inp file and the Job-test.odb file to implement Abaqus automatic calculation and post-processing, and generate the output file test.txt to store the average strain of a specific frame in the analysis step; Isight is used to perform elastic-plastic parameter inversion, and the Simcode program is used to integrate the application input, execution, and output: the input file is the user subroutine test.for, the execution application is the Abaqus batch file test.bat, and the output file is test.txt; Use Task Plan component to achieve parameter optimization: the optimization parameters are elastic-plastic constitutive parameters and m, the optimization objective is to minimize the sum of squares of relative errors between the equivalent solid model and the average strain of the unit cell model, and the optimization algorithms are multi-island genetic algorithm and sequential quadratic programming.

5. The plastic equivalence and simplification method according to claim 1, characterized in that: Corresponding to the triangular arrangement and the quadrilateral arrangement, the trend of f(η) changing with the pore density is calculated by the air film pore density function; f(η) is an unknown function about η: Wherein, μ is the Poisson's ratio of the nickel-based single crystal alloy material, and μ=0.

3.

6. The plastic equivalence and simplification method according to claim 1, characterized in that: According to the periodicity and symmetry of the hole arrangement, a unit cell model is selected from the entire plate and is equivalent to a solid material. The equivalent models for different hole arrangements are different, and the unit cell model is regarded as an equivalent solid model with equivalent elastic constants.

7. The plastic equivalence and simplification method according to claim 6, characterized in that: The equivalent solid model retains the middle hole to analyze the stress state around the hole, and the positions of the remaining holes are replaced by equivalent solid materials.

8. The plastic equivalence and simplification method according to claim 7, characterized in that: The thinner area in the equivalent solid model is calculated using the change relationship of elastic constants under plane stress state, and the thicker area is calculated using generalized plane strain state.

9. The plastic equivalence and simplification method according to claim 1, characterized in that: The air film pore density η of the nickel-based single crystal blade model with dense air film pores is calculated, and the air film pore density function f(η) is introduced to derive the equivalent formula of plastic parameters under various states. Among them, the definition parameters It reflects the distribution density of holes, h is the shortest distance between two holes, and p is the distance between the centers of the two holes.

10. The plastic equivalence and simplification method according to claim 9, characterized in that: The total deformation gradient F of the material is decomposed into the elastic part F e and plastic part F P : F=F e F P Among them, F e Related to the elastic distortion and rigid body rotation of the lattice, F P Slip deformation caused by dislocation motion in an intermediate configuration without distortion; F P The evolution rate is: Among them, L P The velocity gradient of plastic deformation is given by the shear strain rate on all active slip systems Superposition: Among them, m (α) and n (α) is the slip direction of slip system α and the unit vector of the normal line of the slip surface, N is the number of slip systems; The relationship between the shear stress and macroscopic stress of the slip system is: t (α) =s:P (α) Among them, τ (α) is the shear stress of each slip, P (α) is the orientation factor, σ is the stress tensor under the crystal axis system; Orientation factor P (α) Defined as: Among them, m (α) represents the slip direction of the αth slip system in the initial configuration, n (α) represents the unit normal vector of the slip plane of the αth slip system in the initial configuration; Shear strain rate for each slip system α It is represented by a rate-dependent power function equation: in, is called the reference shear strain rate, is the critical shear stress, m is the strain rate sensitivity index; The evolution of the critical shear stress of the slip system conforms to the following hardening law: Among them, h αβ It is called the hardening coefficient, which determines the hardening caused by the slip shear in slip system β on slip system α; h αβ It can be determined by the following formula: h αβ =q αβ h β Among them, q αβ is the matrix describing latent hardening, h β is the single slip hardening rate; where the hardening rate is: Where h0 is the hardening modulus, τ s and a are model parameters.

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