Method for evaluating creep life of dense exhaust film hole based on equivalence

Abstract

The invention provides a model-based dense exhaust film hole creep life evaluation method. The evaluation method comprises the following steps: determining whether a model meets a nickel-based single crystal dense exhaust film hole turbine blade model or not; if yes, deriving a creep constitutive equation of the nickel-based single crystal alloy based on a crystal plasticity theory, and establishing a relational expression among creep damage, creep time, stress and strain rate; deriving a creep life prediction model based on continuous damage mechanics, and establishing a creep life prediction model between creep damage and creep life of the equivalent model; according to the principle that the creep deformations under the same load and temperature and the same creep time are the same, a neural network method is adopted to obtain creep equivalent parameters; simplifying the blade model with the dense gas film holes into an equivalent model containing a small number of gas film holes; and substituting the creep equivalent parameters of the equivalent model into the equivalent model for calculation to obtain the creep damage of the equivalent model, and evaluating the creep life according to the established creep life prediction model.

Description

Technical Field

[0001] The invention relates to the technical field of aero-engines, and in particular to a method for evaluating creep life of a film hole based on equivalent airtight exhaust. 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 will lead to a reduction in the creep life of the blades. Therefore, it is necessary to conduct a creep life assessment and analysis of the blades.

[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 invention, 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 method for evaluating the creep life of a sealed vent hole based on equivalence.

[0006] According to one aspect of the present disclosure, a method for evaluating creep life of a gas-tight vent film hole based on equivalent is provided, comprising:

[0007] Determine whether the model satisfies the nickel-based single crystal dense exhaust film hole turbine blade model;

[0008] If satisfied, then based on the crystal plasticity theory, the creep constitutive equation of nickel-based single crystal alloy is derived, and the relationship between creep damage and creep time, stress, and strain rate is established; the creep life prediction model based on continuous damage mechanics is derived, and a creep life prediction model between creep damage and creep life of an equivalent model is established;

[0009] According to the principle that creep deformation is the same under the same load and temperature and the same creep time, the creep equivalent parameters are obtained by using the neural network method.

[0010] The blade model with dense film holes is simplified to an equivalent model with a small number of film holes.

[0011] The creep equivalent parameters of the equivalent model are brought into the equivalent model for calculation to obtain the creep damage of the equivalent model, and the creep life is evaluated according to the established creep life prediction model.

[0012] In an exemplary embodiment of the present disclosure, the creep damage includes hole damage and material degradation, and the crystal plasticity theory is combined with the continuous damage mechanics model to obtain the shear strain rate expression:

[0013]

[0014] in, represents the initial shear strain rate, ω (α) is hole damage, n represents material parameters, S (α) represents the material degradation damage of slip system α, and e is a natural constant.

[0015] In an exemplary embodiment of the present disclosure, the initial shear strain rate The expression is:

[0016]

[0017] Among them, A represents material parameters, Q represents activation energy, R represents gas law constant, and T represents Kelvin temperature.

[0018] In an exemplary embodiment of the present disclosure, the hole damage rate The expression is:

[0019]

[0020] in, is the initial damage rate.

[0021] In an exemplary embodiment of the present disclosure, the creep deformation u of a unit cell model with a single hole is c The expression is:

[0022]

[0023] Among them, P and c represent material parameters, R (α) express.

[0024] In an exemplary embodiment of the present disclosure, the creep deformation u of the equivalent model c The expression is:

[0025]

[0026]

[0027] Here, S represents the Schmidt factor.

[0028] In an exemplary embodiment of the present disclosure, the creep equivalent parameters are creep parameters after simplifying the model, and the creep equivalent parameters include A, n, ω0 and m.

[0029] In an exemplary embodiment of the present disclosure, the equivalent creep parameter is obtained by a preset compiled algorithm, including:

[0030] Generate random numbers for each equivalent creep parameter, and the range of these random numbers refers to the creep constitutive parameters obtained by experimental fitting;

[0031] The creep deformation of the equivalent solid model is obtained. The theoretical expression of the creep deformation is derived from the creep constitutive model. The random number of each equivalent creep parameter is used as input, and the corresponding creep deformation of the equivalent solid model is obtained as output;

[0032] Training the BP neural network, taking the creep deformation of the equivalent solid model as the input of the BP neural network, and taking the random number of each equivalent creep parameter as the output;

[0033] Obtain the expected creep deformation. According to the equivalence principle, under the same load conditions, the creep deformation of the equivalent solid model without holes and the single-cell model with a single hole are the same. The creep deformation of the single-cell model with a single hole can be obtained through the creep constitutive model, that is, the expected creep deformation of the equivalent solid model can be obtained;

[0034] To obtain equivalent creep parameters, after the BP neural network training is completed, the creep deformation of the non-porous equivalent solid model is used as the input of the neural network, and the trained neural network is used to obtain the corresponding equivalent creep parameters.

[0035] 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, and the unit cell model is regarded as an equivalent solid model with equivalent creep parameters.

[0036] In an exemplary embodiment of the present disclosure, the relationship between the pore size and the pore distribution density is:

[0037] d=1-η

[0038] Where d is the pore size and η is the pore distribution density.

[0039] The present disclosure provides a creep life assessment method based on equivalent dense air film holes. Considering the creep deformation characteristics of nickel-based single crystal alloys, a creep equivalent method is proposed for the dense air film hole arrangement mode that is more common 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. A specific method for obtaining equivalent creep parameters using a neural network is proposed. Under the premise that the creep deformation is the same under the same load and temperature and the same creep time, an equivalent model with equivalent creep parameters is used to replace the original model for finite element analysis within the creep range, which can greatly reduce the calculation amount of turbine cooling blades with dense air film holes, and at the same time obtain accurate creep damage distribution. On the basis of creep equivalence, the creep damage distribution of the equivalent model is obtained. Based on the crystal plasticity theory and continuous damage mechanics, the relationship between creep time, creep stress, creep strain rate and creep damage is established, and a creep life assessment method for nickel-based single crystal turbine blades is proposed.

[0040] 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

[0041] 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:

[0042] Figure 1 A flowchart of a method for evaluating the creep life of a vented film hole based on equivalent airtightness is provided for one embodiment of the present disclosure.

[0043] Figure 2 A schematic diagram of the arrangement of air film holes provided in one embodiment of the present disclosure.

[0044] Figure 3 A schematic diagram of the relationship between f(η) and pore distribution density η is provided for one embodiment of the present disclosure.

[0045] Figure 4 A schematic diagram of a BP neural network provided for an embodiment of the present disclosure.

[0046] Figure 5 A flow chart for calculating equivalent creep parameters provided for one embodiment of the present disclosure.

[0047] Figure 6 A flat plate model with airtight vent holes is provided for one embodiment of the present disclosure.

[0048] Figure 7 for Figure 6 A partial enlarged view of part A in the middle.

[0049] Figure 8 A schematic diagram of a unit cell model provided for one embodiment of the present disclosure.

[0050] Fig. 9 A schematic diagram of an equivalent solid model provided for one embodiment of the present disclosure.

[0051] Fig.10 A schematic diagram of an equivalent flat plate model provided for one embodiment of the present disclosure.

[0052] Fig.11 for Fig.10 A partial enlarged view of part B in the middle.

[0053] Fig.12 A schematic diagram for comparing creep curves with η=0.6 provided for an embodiment of the present disclosure.

[0054] Fig.13 A schematic diagram for comparing creep curves with η=0.8 provided for an embodiment of the present disclosure.

[0055] Fig.14 A schematic diagram of a creep life error band provided for an embodiment of the present disclosure. DETAILED DESCRIPTION

[0056] 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.

[0057] 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.

[0058] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities may be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0059] 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.

[0060] Since the air film holes on the cooling blades have the characteristics of small aperture and dense arrangement, it is difficult to mesh the air film holes when performing finite element calculations, which brings great difficulties to the creep life assessment of the blades. It is necessary to study the equivalent method of the air film holes and to conduct creep life assessment of the blades on this basis.

[0061] Turbine cooling blades usually contain a large number of densely packed film holes, which causes the blades to be in a complex stress state. Currently, creep life assessment for a single stress state has been widely used, but the creep life assessment method that considers the influence of complex stress states is not yet mature. The film holes are densely arranged on the turbine cooling blades, with small apertures and large numbers, making it difficult to mesh the cooling blades during finite element analysis, 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 on the hole edge is corrected by the stress concentration factor (usually 3), and the calculated results are not very accurate.

[0062] Based on the above situation, the present disclosure provides a method for evaluating the creep life of a vent hole based on an equivalent airtight vent film, such as Figure 1 As shown, including:

[0063] Step S100, determining whether the model satisfies the nickel-based single crystal dense exhaust film hole turbine blade model;

[0064] Step S200: If the conditions are met, derive the creep constitutive equation of the nickel-based single crystal alloy based on crystal plasticity theory, and establish the relationship between creep damage and creep time, stress, and strain rate; derive a creep life prediction model based on continuous damage mechanics, and establish a creep life prediction model between creep damage and creep life of an equivalent model;

[0065] Step S300, according to the principle that creep deformation is the same under the same load and temperature and the same creep time, a neural network method is used to obtain creep equivalent parameters;

[0066] Step S400, simplifying the blade model with densely spaced film holes into an equivalent model with a small number of film holes;

[0067] Step S500: bringing the creep equivalent parameters of the equivalent model into the equivalent model for calculation to obtain the creep damage of the equivalent model, and evaluating the creep life according to the established creep life prediction model.

[0068] The present disclosure provides a creep life assessment method based on equivalent dense air film holes. Considering the creep deformation characteristics of nickel-based single crystal alloys, a creep equivalent method is proposed for the dense air film hole arrangement mode that is more common 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. A specific method for obtaining equivalent creep parameters using a neural network is proposed. Under the premise that the creep deformation is the same under the same load and temperature and the same creep time, an equivalent model with equivalent creep parameters is used to replace the original model for finite element analysis within the creep range, which can greatly reduce the calculation amount of turbine cooling blades with dense air film holes, and at the same time obtain accurate creep damage distribution. On the basis of creep equivalence, the creep damage distribution of the equivalent model is obtained. Based on the crystal plasticity theory and continuous damage mechanics, the relationship between creep time, creep stress, creep strain rate and creep damage is established, and a creep life assessment method for nickel-based single crystal turbine blades is proposed.

[0069] Below, each step of the creep life assessment method of the airtight vent film based on equivalent airtight venting provided by the present disclosure will be introduced in detail.

[0070] In step S100, it is determined whether the model satisfies the nickel-based single crystal dense exhaust film hole turbine blade model.

[0071] Specifically, it is first determined whether the model is a nickel-based single crystal blade model containing dense venting film holes. If so, the creep life evaluation can be performed according to the method provided in the present disclosure.

[0072] In step S200, if the conditions are met, the creep constitutive equation of the nickel-based single crystal alloy is derived based on the crystal plasticity theory, and the relationship between creep damage and creep time, stress, and strain rate is established; a creep life prediction model based on continuous damage mechanics is derived, and a creep life prediction model between creep damage and creep life of an equivalent model is established.

[0073] Specifically, based on the crystal plasticity theory, the creep constitutive model of the densely-filled pore structure of nickel-based single crystal alloy is derived, and the expression of creep deformation is obtained as follows:

[0074] For a single crystal air film hole plate under multiaxial stress state, the shear stress τ (α) According to the equivalent stress σ * It is deduced that:

[0075]

[0076] in, is the Schmidt factor.

[0077] Among them, the definition parameters Reflects the distribution density of holes. Figure 2 As 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.

[0078] The trend of f(η) changing with the pore density is obtained by calculating the air film pore density function. f(η) is an unknown function about η:

[0079]

[0080] in, μ H The relationship between the value of and η is shown in Table 1, μ is the Poisson's ratio of the nickel-based single crystal alloy material, and μ is taken as 0.3. E represents the elastic modulus, E H Represents the equivalent elastic modulus; μ H represents the equivalent Poisson's ratio.

[0081] Table 1. Elastic constant values ​​under quadrilateral and triangular arrangements

[0082]

[0083] like Figure 3 As shown, 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 can be fitted using Matlab software.

[0084] Equivalent stressσ * According to the stress σ and the hole distribution density f(η), we can get:

[0085] σ * =σ0f(η)

[0086] Orowan stress τ orowan Used to describe the structural hardening / softening caused by the microstructural evolution of nickel-based single crystal superalloys, the expression is:

[0087]

[0088] Among them, G represents the shear modulus, B represents the size of the Burgers vector (for the dislocation motion on the octahedral slip system of nickel-based single crystal, the value of B is 0.254nm), w represents the γ channel width on the

[001] orientation, and λ represents the correction coefficient.

[0089] The γ channel width w can be defined as a function of the creep time t:

[0090]

[0091] Wherein, w0 is the initial value of the γ channel width (for nickel-based single crystal high-temperature alloys, w0 = 0.05 μm), and k1 represents the rafting rate of the material.

[0092] Stress caused by dislocation network formed in γ phase It also hinders creep deformation as shown below:

[0093]

[0094] Among them, k2 is a geometric factor, ρ (α) Indicates the dislocation density of a / 2<110>.

[0095] ρ (α) The evolution law can be expressed by the following formula:

[0096]

[0097] Among them, r1 and r2 are constitutive parameters representing dislocation stress hardening and dislocation stress recovery, respectively. The influence of can be ignored.

[0098] The creep rupture or tensile failure of nickel-based single crystal materials at a certain temperature depends on the relationship between the applied stress and the yield stress. The failure criteria are defined as follows:

[0099]

[0100] When R (α) ≤0, shear stress τ (α) is smaller than the critical value for dislocations to enter the γ matrix phase, and no slip deformation occurs, so when Obvious creep deformation can be observed.

[0101] The creep model combining crystal plasticity theory and continuum damage mechanics is based on the stress R (α) Shear strain rate The damage in the creep process mainly includes hole damage and material degradation. The crystal plasticity theory is combined with the continuum damage mechanics model to obtain the following expression:

[0102]

[0103] in, represents the initial shear strain rate, ω (α) is hole damage, n represents material parameters, S (α) Indicates the material degradation damage of slip system α.

[0104] Initial shear strain rate It can be expressed as:

[0105]

[0106] Among them, A is the material parameter, Q is the activation energy (Q octahedron =6.97E-19 J / atom), R is the gas law constant, and T is the Kelvin temperature.

[0107] Hole damage rate It can be expressed as:

[0108]

[0109] in, is the initial damage rate.

[0110] Material degradation damage of slip system α This can be derived in the following way:

[0111]

[0112] Among them, C and P represent material parameters. It should be noted that material parameters can be understood as constants related to the material, and C and P of different materials are different.

[0113] The total creep damage includes hole damage and material degradation, and its calculation formula is as follows:

[0114] D=D S +ω

[0115] Among them, the damage caused by material degradation D S It can be expressed as:

[0116]

[0117] The axial creep strain can be calculated by the following expression:

[0118]

[0119] Among them, γ (α) represents the shear strain, Represents the transform coefficients.

[0120] The creep strain rate can be expressed as:

[0121]

[0122] The creep strain can be obtained by integrating the equation for the creep strain rate:

[0123]

[0124] The creep deformation of a unit cell model with a single hole can be calculated using the following formula:

[0125]

[0126] In step S300, according to the principle that creep deformation is the same for the same load and temperature and the same creep time, a neural network method is used to obtain creep equivalent parameters.

[0127] Specifically, according to the established method for analyzing the creep characteristics of a specimen with densely arranged air film holes, a unit cell model with a single hole is regarded as the corresponding equivalent solid model without holes.

[0128] The creep deformation of the equivalent model can be expressed as:

[0129]

[0130] The equivalent creep parameters are obtained based on the fact that the creep deformation of the unit cell model with a single hole and the equivalent solid model without a hole are the same under the same stress and temperature. Where S represents the Schmidt factor.

[0131] make:

[0132]

[0133] A method for predicting equivalent creep parameters based on BP neural network is proposed. The typical schematic diagram of BP neural network is as follows: Figure 4 As shown. The BP neural network consists of an input layer, an output layer, and one or more hidden layers. The unique feature of the BP neural network is that it is a feedforward neural network trained by the error back propagation algorithm.

[0134] A general BP neural network with k input neurons, j hidden neurons and i output neurons is considered. The training sample set of the BP neural network is defined as Among them, x l is the input of the lth training sample, y l is the expected output of the lth training sample. The weight matrix between the input layer and the hidden layer is W1=(w st ) j×k and w s =(w s1 ,w s1 ,…,w sp ), where s = 1, 2, …, j. The weight matrix between the hidden layer and the output layer is defined as W2 = (w rs ) i×j ,in where r = 1, 2, ..., i, Where s = 1, 2, …, j. The total weight matrix is ​​defined as follows:

[0135]

[0136] The present disclosure defines g and f as the corresponding activation functions of the hidden layer and output layer of the BP neural network, respectively, and defines two vector-valued functions to simplify the representation of g and f.

[0137]

[0138] F(W2G(W1x l ))=(f(w b1 ·G(w1·x l )),…,f(w bi ·G(w1·x l ))) T

[0139] make and w are the input matrix and weight matrix of the neural network respectively, then the error of the network can be given by the following formula:

[0140]

[0141] in, l=1,2,…,L.

[0142] The gradient of the error function of the weight matrix can be expressed as:

[0143]

[0144]

[0145] Definition E w for:

[0146]

[0147] The equivalent creep parameters are obtained by compiling a special algorithm. The basic steps are as follows:

[0148] Step 1: Generate random numbers for each equivalent creep parameter. The range of these random numbers refers to the creep constitutive parameters obtained by experimental fitting.

[0149] Step 2: Obtain the creep deformation of the equivalent solid model. The theoretical expression of creep deformation is derived from the creep constitutive model. The random number of each equivalent creep parameter is used as input, and the corresponding creep deformation of the equivalent solid model is obtained as output.

[0150] Step 3: Train the BP neural network. The creep deformation of the equivalent solid model is used as the input of the BP neural network, and the random number of each equivalent creep parameter is used as the output.

[0151] Step 4: Obtain the expected creep deformation. According to the equivalence principle, under the same load conditions, the creep deformation of the equivalent solid model without a hole and the single cell model with a single hole are the same. The creep deformation of the single cell model with a single hole can be obtained through the creep constitutive model, that is, the expected creep deformation of the equivalent solid model can be obtained.

[0152] Step 5: Obtain equivalent creep parameters. After the BP neural network training is completed, the creep deformation of the equivalent solid model without holes in step 4 is used as the input of the neural network, and the corresponding equivalent creep parameters are obtained using the trained neural network.

[0153] The flow chart for calculating equivalent creep parameters is as follows: Figure 5 shown.

[0154] In step S400, the blade model with densely packed film holes is simplified to an equivalent model with a small number of film holes.

[0155] Specifically, the simplification is performed according to the following equivalent model:

[0156] The number of model holes listed below is proposed by the applicant based on the number of film holes in commercial blades. The air distribution is consistent with the distribution of film cooling holes in commercial cooling blades. The plate size is calculated based on the formula and can be adjusted based on 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.

[0157] The flat plate model with airtight vent holes is as follows: Figure 6 and Figure 7 As shown, the model includes 150 holes. The length of the plate 10 in the figure is 35 mm and the width is 6 mm. The numerical simulation is performed using a three-dimensional plate model. In the present disclosure, the spacing p between the holes is 1; wherein the value of p is selected based on literature and the optimal spacing between holes in engineering, and other values ​​may also be selected; for different hole distribution densities η, the hole diameter size d is different; the relationship between the hole diameter and the hole distribution density is:

[0158] d=1-η

[0159] According to the periodicity and symmetry of the hole arrangement, a unit cell model is selected from the entire plate 10, and the unit cell model is equivalent to a solid material. The equivalent principle is as follows: Figure 8 and Fig. 9 As shown, the unit cell model is considered as an equivalent solid model with equivalent creep parameters.

[0160] Considering the anisotropic characteristics of nickel-based single crystal materials, in order to analyze the mechanical properties of turbine blades in service, the equivalent plate model of plate 10 retains 9 typical holes in the middle to analyze the stress state around the holes, and the positions of the remaining holes are replaced by equivalent solid materials, such as Fig.10 and Fig.11 As 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. Among them: the dense air film hole model is simplified to the middle 9-hole model, which is to analyze the circumferential stress state of the middle hole under multi-hole interference. The position of the 9 holes can also be selected according to the situation. It can be selected in the middle to analyze the stress state of the hole under multi-hole interference, or it can be selected on the corners. However, if it is selected at the corners, it is impossible to analyze the stress state of the hole under the multi-hole interference of the surrounding holes. In addition, the relationship between the middle 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.

[0161] In step S500, the creep equivalent parameters of the equivalent model are brought into the equivalent model for calculation to obtain the creep damage of the equivalent model, and the creep life is evaluated according to the established creep life prediction model.

[0162] Specifically, finite element analysis is performed on the equivalent model of the blade to obtain the creep damage and then evaluate the creep life.

[0163] Abaqus was used to calculate the directionally solidified nickel-based single crystal alloy dense vent hole plate and the equivalent single hole plate model, and the creep curve was obtained and the creep life was evaluated. Fig.12 and Fig.13 As shown in the figure, by comparing the predicted values ​​and experimental values ​​of creep life under different conditions, the rationality of the creep life evaluation method based on equivalent airtight vent film holes has been verified.

[0164] like Fig.14 As shown in the figure, the creep time calculated by the equivalent model is not much different from the creep life obtained by the experiment, and the error is less than 15%, indicating that the proposed creep life assessment method based on equivalent airtight vent hole can achieve good life assessment. Figure 12 to Figure 14 In the table, Experiment means experiment, Model Plate means plate model, Simplified model means equivalent model, Creep strain in the ordinate means creep strain, and Creep time in the abscissa means creep time. Square means quadrilateral arrangement, Triangular means triangular arrangement, Creep time of simplifiedmodel in the ordinate means creep time of equivalent model, and Creep time of experimental results in the abscissa means experimental value of creep time.

[0165] The creep life assessment method provided by the present invention takes into account the influence of the complex stress state caused by dense air film holes, and has higher accuracy than the existing method that only considers the uniaxial stress state and the method that uses specific coefficient correction; this equivalent method takes into account the viscoplastic and anisotropic characteristics of the material when equating the creep parameters of the material, and is more practical than the existing method that approximates the material as an isotropic material; an air film hole density function is introduced to effectively characterize the distribution of air film holes; according to the viscoplastic and anisotropic characteristics, a corresponding equivalent formula of the creep constitutive model based on crystal plasticity theory and continuous damage mechanics is proposed; it is proposed to use a neural network method to solve the equivalent creep parameters, which has wide applicability; the simplified method containing dense air film holes takes into account its feasibility and accuracy in calculating the strength life of nickel-based single crystal cooling blades.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] 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 method for evaluating creep life of a gas-tight film hole based on equivalent gas-tight film, characterized in that: include: Determine whether the model satisfies the nickel-based single crystal dense exhaust film hole turbine blade model; If satisfied, then based on the crystal plasticity theory, the creep constitutive equation of nickel-based single crystal alloy is derived, and the relationship between creep damage and creep time, stress, and strain rate is established; the creep life prediction model based on continuous damage mechanics is derived, and a creep life prediction model between creep damage and creep life of an equivalent model is established; According to the principle that creep deformation is the same under the same load and temperature and the same creep time, the creep equivalent parameters are obtained by using the neural network method. The blade model with dense film holes is simplified to an equivalent model with a small number of film holes. The creep equivalent parameters of the equivalent model are brought into the equivalent model for calculation to obtain the creep damage of the equivalent model, and the creep life is evaluated according to the established creep life prediction model.

2. The life assessment method according to claim 1, characterized in that: The creep damage includes hole damage and material degradation. The crystal plasticity theory is combined with the continuous damage mechanics model to obtain the shear strain rate expression: in, represents the initial shear strain rate, ω (α) is hole damage, n represents material parameters, S (α) represents the material degradation damage of slip system α, and e is a natural constant.

3. The life assessment method according to claim 2, characterized in that: The initial shear strain rate The expression is: Among them, A represents material parameters, Q represents activation energy, R represents gas law constant, and T represents Kelvin temperature.

4. The life assessment method according to claim 3, characterized in that: Hole damage rate The expression is: in, is the initial damage rate.

5. The life assessment method according to claim 4, characterized in that: Creep deformation u of a unit cell model with a single hole c The expression is: Among them, P and c represent material parameters, R (α) express.

6. The life assessment method according to claim 1, characterized in that: Creep deformation u of the equivalent model c The expression is: Here, S represents the Schmidt factor.

7. The life assessment method according to claim 1, characterized in that: The creep equivalent parameters are creep parameters after simplifying the model, and the creep equivalent parameters include A, n, ω0 and m.

8. The life assessment method according to claim 1, characterized in that: The equivalent creep parameters are obtained through preset compiled algorithms, including: Generate random numbers for each equivalent creep parameter, and the range of these random numbers refers to the creep constitutive parameters obtained by experimental fitting; The creep deformation of the equivalent solid model is obtained. The theoretical expression of the creep deformation is derived from the creep constitutive model. The random number of each equivalent creep parameter is used as input, and the corresponding creep deformation of the equivalent solid model is obtained as output; Training the BP neural network, taking the creep deformation of the equivalent solid model as the input of the BP neural network, and taking the random number of each equivalent creep parameter as the output; Obtain the expected creep deformation. According to the equivalence principle, under the same load conditions, the creep deformation of the equivalent solid model without holes and the single-cell model with a single hole are the same. The creep deformation of the single-cell model with a single hole can be obtained through the creep constitutive model, that is, the expected creep deformation of the equivalent solid model can be obtained; To obtain equivalent creep parameters, after the BP neural network training is completed, the creep deformation of the non-porous equivalent solid model is used as the input of the neural network, and the trained neural network is used to obtain the corresponding equivalent creep parameters.

9. The life assessment method according to claim 1, characterized in that: According to the periodicity and symmetry of the hole arrangement, the unit cell model is selected from the entire plate, and the unit cell model is equivalent to a solid material. The unit cell model is regarded as an equivalent solid model with equivalent creep parameters.

10. The life assessment method according to claim 1, characterized in that: The relationship between pore size and pore distribution density is: d=1-η Where d is the pore size and η is the pore distribution density.

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