Creep constitutive model construction and its creep prediction method for turbine blade of aero-engine

Abstract

The application provides a creep constitutive model construction method, which comprises the following steps: constructing a creep curve of a deceleration creep stage; constructing a creep curve of a constant speed creep stage; constructing a creep curve of an acceleration creep stage; associating the creep constitutive model parameters with temperature and stress; and constructing a creep constitutive model. The application also provides an aero-engine turbine blade creep prediction method, which comprises the following steps: constructing a turbine blade three-dimensional finite element model, applying working load to the model, and calculating the stress, strain and temperature of nodes of the turbine blade three-dimensional finite element model; and based on the stress, strain and temperature of the nodes of the turbine blade three-dimensional finite element model, calculating the creep deformation and relaxation stress by using the model constructed by the creep constitutive model construction method.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of creep prediction of turbine blades of an aero-engine, and particularly relates to a creep constitutive model construction and a creep prediction method for turbine blades of an aero-engine. BACKGROUND

[0002] Creep refers to a phenomenon that a metal slowly plastically deforms under the action of a continuous stress at a certain temperature, and the occurrence of the creep phenomenon is a result of the joint action of temperature, stress and time. The process mainly includes three stages of deceleration creep stage, constant speed creep stage and acceleration creep stage, and the characteristics are that the deformation, stress and external force no longer maintain a one-to-one correspondence, and the deformation has an irreversible deformation property even when the stress is less than the yield limit.

[0003] The turbine blades of an aero-engine are long time working in a high temperature gas environment, and one of the main failure modes is creep. The creep leads to excessive plastic deformation of the blades or creep stress fracture. Especially with the rapid development of aviation technology, the turbine front temperature is continuously increased, and the creep deformation and creep stress fracture of the turbine blades under the working environment of medium and high temperature for a long time are more prominent.

[0004] The creep of the turbine blades of an aero-engine is predicted to provide effective support for the design and improvement of the turbine blade scheme. An accurate and reliable creep constitutive model is the basis for predicting the creep of the turbine blades of an aero-engine, and the current creep constitutive model has the following defects:

[0005] 1) Only the creep test data of a single crystal / directional crystalline alloy standard specimen are verified, and the numerical simulation analysis convergence of the real turbine blades under complex working conditions is poor.

[0006] 2) The effects of temperature and stress on creep are not fully considered, and the three stages of the creep process cannot be completely described, and the creep deformation and stress values of the turbine blades under non-uniform temperature field and complex stress conditions cannot be accurately calculated.

[0007] The present application is proposed in view of the above technical defects.

[0008] It should be noted that the disclosure of the above background art content is only used to assist in understanding the inventive concept and technical solutions of the present application, and it does not necessarily belong to the prior art of the present patent application. In the absence of explicit evidence that the above content has been disclosed on the filing date of the present application, the above background art should not be used to evaluate the novelty and inventiveness of the present application. SUMMARY

[0009] The application aims to provide a creep constitutive model construction and a turbine blade creep prediction method for an aero-engine, so as to overcome or alleviate at least one aspect of the known technical defects.

[0010] The technical solution of the application is:

[0011] In one aspect, a creep constitutive model construction method is provided, comprising:

[0012] The creep curve of the deceleration creep stage is constructed:

[0013] ε P = βln (αt + 1), t≤t P / S ;

[0014] The creep curve of the constant speed creep stage is constructed:

[0015] t P / S <t≤t S / T ;

[0016] The creep curve of the acceleration creep stage is constructed:

[0017] ε T = θ (exp [ω (t-t S / T )] - 1), t S / T <t;

[0018] The creep constitutive model parameters are associated with temperature and stress:

[0019]

[0020] The creep constitutive model is constructed:

[0021] ε c = ε p + ε s + ε T ;

[0022] Wherein,

[0023] ε P , ε S , ε T are the creep strains of the deceleration creep stage, the constant speed creep stage and the acceleration creep stage;

[0024] are the creep strain rates of the deceleration creep stage, the constant speed creep stage and the acceleration creep stage;

[0025] is the initial creep rate of the deceleration creep stage;

[0026] t is the working time considering creep;

[0027] t P / S is the conversion time of the deceleration creep stage and the constant speed creep stage;

[0028] t S / T is the conversion time of the constant speed creep stage and the acceleration creep stage;

[0029] α, β are parameters of the deceleration creep stage curve, and α is a parameter representing the bending degree of the deceleration creep stage curve;

[0030] ω, θ are parameters of the acceleration creep stage curve, and ω is a parameter representing the bending degree of the acceleration creep stage curve;

[0031] C is a constant;

[0032] ε P / S is the creep strain at the conversion time of the deceleration creep stage and the constant speed creep stage;

[0033] A0, A1, A2 are creep constitutive model parameters, corresponding to α, ω have different parameter values;

[0034] T is the temperature at the time of creep;

[0035] σ is the stress at the time of creep;

[0036] E is the elastic modulus of the material.

[0037] According to at least one embodiment of the present application, the above-mentioned aero-engine turbine blade creep prediction method further comprises:

[0038] According to the creep curve corresponding to different creep temperatures and stresses, the initial creep rate of the deceleration creep stage is fitted:

[0039]

[0040] According to the creep curve corresponding to different creep temperatures and stresses, the creep rate of the constant speed creep stage is fitted:

[0041]

[0042] According to the creep curve corresponding to different creep temperatures and stresses, the bending degree of the deceleration creep stage curve is fitted:

[0043] α = exp{b1+b2 / T+b3In(sinh(b4σ / E))};

[0044] According to the creep curve corresponding to different creep temperatures and stresses, the bending degree of the acceleration creep stage curve is fitted:

[0045] ω = exp{d1 + d2 / T + d3ln(sinh(d4σ / E))};

[0046] wherein,

[0047] a1, a2, a3, a6 are creep constitutive model coefficients of initial creep rate in the deceleration creep stage;

[0048] c1, c2, c3, c6 are creep constitutive model coefficients of creep rate in the constant speed creep stage;

[0049] b1, b2, b3, b6 are creep constitutive model coefficients of bending degree of the deceleration creep stage curve;

[0050] d1, d2, d3, d6 are creep constitutive model coefficients of bending degree of the acceleration creep stage curve.

[0051] According to at least one embodiment of the present application, in the above-mentioned aero-engine turbine blade creep prediction method, when fitting the bending degree of the deceleration creep stage curve according to the creep curves corresponding to different creep temperatures and stresses, the bending degree of the deceleration creep stage curve is obtained by using the corresponding relationship of the conversion time of the deceleration creep stage and the constant speed creep stage:

[0052]

[0053] When fitting the bending degree of the acceleration creep stage curve according to the creep curves corresponding to different creep temperatures and stresses, the bending degree of the acceleration creep stage curve is obtained by using the corresponding relationship of the end time of the acceleration creep stage:

[0054]

[0055] wherein,

[0056] is the creep rate at the end time of the acceleration creep stage;

[0057] t total is the end time of the acceleration creep stage;

[0058] According to at least one embodiment of the present application, the above-mentioned aero-engine turbine blade creep prediction method further comprises:

[0059] According to the elastic modulus measurement data of the material at different temperatures, the relationship between the elastic modulus of the material and the temperature is fitted:

[0060] E = E0 + E1T + E2T 2 + E3T 3 + E4T 4 + E5T 5 ;

[0061] wherein,

[0062] E0, E1, E2, E3, E4, E5 are coefficients for fitting the elastic modulus of the creep material at the temperature of the creep.

[0063] According to at least one embodiment of the present application, the above-mentioned aero-engine turbine blade creep prediction method further comprises:

[0064] The creep strain rate at the constant speed creep stage is fitted to the duration of the constant speed creep stage:

[0065]

[0066]

[0067] wherein,

[0068] K0, K1, K2, K3, K4, K5 are coefficients for fitting the creep strain rate at the constant speed creep stage to the duration of the constant speed creep stage.

[0069] In another aspect, an aero-engine turbine blade creep prediction method is provided, comprising:

[0070] A three-dimensional finite element model of the turbine blade is constructed, a working load is applied thereon, and the stress, strain and temperature of the nodes of the three-dimensional finite element model of the turbine blade are calculated;

[0071] Based on the stress, strain and temperature of the nodes of the three-dimensional finite element model of the turbine blade, the creep strain and the creep stress are calculated by using the model constructed by any of the above-mentioned creep constitutive model construction methods.

[0072] According to at least one embodiment of the present application, in the above-mentioned aero-engine turbine blade creep prediction method, if the calculation of the creep strain and the creep stress does not converge, the time increment step is adjusted until it can converge.

[0073] According to at least one embodiment of the present application, in the above-mentioned aero-engine turbine blade creep prediction method, the material parameters at different temperatures of the turbine blade are obtained by interpolation of the material parameters at a specific temperature.

[0074] According to at least one embodiment of the present application, in the above-mentioned aero-engine turbine blade creep prediction method, the working load comprises a centrifugal load, an aerodynamic load and a temperature load. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 is a schematic diagram of the creep constitutive model construction and the aero-engine turbine blade creep prediction method provided by the embodiments of the present application.

[0076] For better illustrating the present embodiment, some components in the drawings can be omitted, enlarged or reduced, and do not represent the actual product size. In addition, the drawings are only used for illustrative description and cannot be understood as a limitation to the present patent. DETAILED DESCRIPTION

[0077] In order to make the technical solutions of the present application and the advantages thereof clearer, the technical solutions of the present application will be further clearly and completely described in detail below in conjunction with the drawings. It should be understood that the specific embodiments described herein are only some embodiments of the present application, which are used to explain the present application, but not to limit the present application. It should be noted that, for the purpose of description, only parts related to the present application are shown in the drawings, and other related parts can be referred to the general design. In the case of no conflict, the embodiments in the present application and the technical features in the embodiments can be combined to obtain new embodiments.

[0078] In addition, unless otherwise defined, the technical terms or scientific terms used in the present application description should be the general meaning understood by the general technical personnel in the field to which the present application belongs. The words indicating the direction or position relationship such as "upper", "lower", "left", "right", "center", "vertical", "horizontal", "inner", "outer" and the like used in the present application description are only used to indicate the relative direction or position relationship, and not to imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and the relative position relationship can also change accordingly when the absolute position of the described object changes, therefore, it cannot be understood as a limitation to the present application. The "first", "second", "third" and the like used in the present application description are only for the purpose of description, to distinguish different components, and cannot be understood as indicating or implying relative importance. The "one", "an" or "the" and the like used in the present application description should not be understood as an absolute limitation on the quantity, but should be understood as the existence of at least one. The "including" or "containing" and the like used in the present application description means that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, and do not exclude other elements or objects.

[0079] In addition, it should be further noted that, unless otherwise explicitly specified and limited, the "mounting", "connection", "connecting" and the like used in the present application description should be understood in a broad sense, for example, the connection can be a fixed connection, or a detachable connection, or an integral connection; can be a mechanical connection, or an electrical connection; can be a direct connection, or an indirect connection through an intermediate medium, or a connection between two elements inside, and the person skilled in the art can understand the specific meaning of the present application according to the specific circumstances.

[0080] The present application will be further described below in conjunction with the drawings Figure 1 The present application will be further described below in conjunction with the drawings

[0081] The creep constitutive model provided by the application and the creep prediction method of the turbine blade of the aero-engine can be performed according to the following steps.

[0082] Step 1:

[0083] The necessary conditions for creep deformation and stress calculation of the turbine blade of the aero-engine are input, including basic performance data of the turbine blade material, a creep curve, a three-dimensional model of the turbine blade, creep / stress fracture life design requirements, a calculation state for analysis, aerodynamic data and temperature data.

[0084] Step 2:

[0085] The deceleration creep stage of the typical creep curve starts with a relatively high creep rate, and the creep rate gradually decreases until the minimum creep rate is reached at the time of conversion between the deceleration creep stage and the constant speed creep stage. The creep of the constant speed creep stage remains unchanged at the minimum creep rate, and then the creep rate starts to increase at the time of conversion between the constant speed creep stage and the third stage, until the fracture.

[0086] According to the shape of the creep three-stage test curve, formulas of different mathematical forms are given to describe the creep curve.

[0087] The deceleration creep stage is described by a logarithmic model:

[0088] ε P = βln(αt+1), t≤t P / S ;

[0089] The constant speed creep stage keeps the creep rate unchanged, and is described as follows:

[0090] t P / S <t≤t S / T ;

[0091] The acceleration creep stage increases the creep rate, and is described by referring to the θ method:

[0092] ε T = θ(exp[ω(t-t S / T )]-1), t S / T <t;

[0093] The creep constitutive model parameters are associated with temperature and stress, and a stress and temperature association term is introduced:

[0094]

[0095] The creep constitutive model is constructed:

[0096] ε c= ε p + ε s + ε T ;

[0097] wherein,

[0098] ε P , ε S , ε T is the creep strain of the deceleration creep stage, the constant speed creep stage and the acceleration creep stage;

[0099] is the creep strain rate of the deceleration creep stage, the constant speed creep stage and the acceleration creep stage;

[0100] is the initial creep rate of the deceleration creep stage;

[0101] t is the working time considering creep;

[0102] t P / S is the conversion time of the deceleration creep stage and the constant speed creep stage;

[0103] t S / T is the conversion time of the constant speed creep stage and the acceleration creep stage;

[0104] α, β are parameters of the deceleration creep stage curve, and α is a parameter representing the bending degree of the deceleration creep stage curve;

[0105] at t = 0,

[0106] the initial creep rate of the deceleration creep stage

[0107] ω, θ are parameters of the acceleration creep stage curve, and ω is a parameter representing the bending degree of the acceleration creep stage curve;

[0108] at t = t S / T ,

[0109] the creep rate of the constant speed creep stage

[0110] C is a constant;

[0111] ε P / S is the creep strain at the conversion time of the deceleration creep stage and the constant speed creep stage;

[0112] A0, A1, A2 are creep constitutive model parameters, corresponding to α, ω have different parameter values;

[0113] T is the temperature at the time of creep;

[0114] σ is the stress at the time of creep;

[0115] E is the elastic modulus of the material.

[0116] The constructed creep constitutive model comprehensively considers three stages of creep, and the parameters of the three stages in the model are basically independent of each other, and are associated with stress and temperature, and through the design of the creep model and the criterion, the smooth transition of the three-stage creep deformation curve is realized, and the three-stage creep deformation can be completely described.

[0117] Step 3:

[0118] According to the temperature fitting elastic modulus, the temperature is fitted by the material performance data by using 5th order polynomial, and the coefficients of 5th order polynomial are obtained:

[0119] E = E0 + E1T + E2T 2 + E3T 3 + E4T 4 + E5T 5 ;

[0120] According to fitting the duration of constant speed creep stage, the creep duration of constant speed creep stage, and fitting by using 5th order polynomial, and the coefficients of 5th order polynomial are obtained:

[0121]

[0122]

[0123] According to the creep curve corresponding to different creep temperature and stress, the initial creep rate of deceleration creep stage is fitted, and the coefficients a1, a2, a3, a4 are obtained:

[0124]

[0125] According to the creep curve corresponding to different creep temperature and stress, the creep rate of constant speed creep stage is fitted, and the coefficients c1, c2, c3, c4 are obtained:

[0126]

[0127] According to the bending degree of the deceleration creep stage curve corresponding to different creep temperature and stress, the coefficients b1, b2, b3, b4 are obtained:

[0128]

[0129] According to the corresponding relationship of the conversion time of deceleration creep stage and constant speed creep stage, the bending degree of the deceleration creep stage curve is obtained:

[0130]

[0131] According to the creep curve corresponding to different creep temperature, stress, the bending degree of the accelerated creep stage curve is fitted, and the coefficients d1, d2, d3 and d4 are obtained:

[0132] ω=exp{d1+d2 / T+d3In(sinh(d4σ / E))};

[0133] The bending degree of the accelerated creep stage curve is obtained according to the corresponding relationship at the end time of the accelerated creep stage:

[0134]

[0135] Wherein,

[0136] The creep rate at the end time of the accelerated creep stage;

[0137] t total The end time of the accelerated creep stage;

[0138] Step 4:

[0139] The creep constitutive model is combined with the secondary development interface of the commercial finite element ABAQUS, and the creep user subroutine is compiled. In addition to the creep constitutive model algorithm module, the subroutine can also include an interpolation module and an error control module; wherein,

[0140] The main function of the interpolation module is to interpolate the material parameters according to the temperature. For a certain turbine blade material, only the material parameters at several specific temperatures are extracted, but the temperature of the current finite element model calculation node is generally not within these specific temperatures, and the constitutive parameters need to be interpolated according to the temperature of the node;

[0141] The main function of the error control module is to control the error. If the error does not meet the requirements, the increment step is reduced, the stress and strain are recalculated and updated, until the error meets the requirements, the state variables are stored, and the increment step is ended.

[0142] Step 5:

[0143] Based on the finite element software ABAQUS analysis platform, a three-dimensional finite element model of the turbine blade is constructed, and according to the working true load of the turbine blade, the corresponding centrifugal load, aerodynamic load and temperature load are applied, and the calculation is carried out under the non-uniform stress field and temperature field. The stress, strain and temperature of the finite element model node are transmitted to the creep user subroutine.

[0144] Step 6:

[0145] The creep user subroutine carries out creep deformation and stress iteration calculation of the turbine blade, calculates the creep rate and creep increment of the current time increment step of each stage of creep according to the time increment step, if the result converges, the stress and strain and the total amount of creep are updated and the increment step is increased to continue iteration calculation, if the result does not converge, the time increment step is adjusted to recalculate until the requirements are met, and finally the calculation results are fed back to the ABAQUS main program to obtain the creep strain and its creep stress.

[0146] The model constructed by the creep constitutive model construction method provided in the application can accurately describe the creep behavior of the three stages of the creep process, has high simulation precision, and can better meet the actual engineering requirements.

[0147] In the creep constitutive model construction method provided in the application, the temperature variable and the stress variable are taken as model parameters, the influence of the temperature field and the stress field on the component under actual working conditions is unified, the convergence problem caused by the temperature / stress interpolation of the parameters is avoided, and the model has good stability in the full-field temperature and stress range.

[0148] In the creep constitutive model construction method provided in the application, the parameters in the creep constitutive model are expressed as functions of stress and temperature, have interpolation and extrapolation functions, can ensure the convergence of the calculation in the case of less creep data, and have strong engineering applicability.

[0149] When predicting the creep of the turbine blade of the aero-engine, the model constructed by the creep constitutive model construction method provided in the application has high efficiency and can shorten the iteration cycle of the turbine blade design.

[0150] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be mutually referred to.

[0151] So far, the technical solution of the application has been described in combination with the preferred embodiments shown in the drawings. Those skilled in the art should understand that the protection scope of the application is obviously not limited to these specific embodiments. Without deviating from the principles of the application, those skilled in the art can make equivalent changes or replacements to the related technical features. The technical solutions after the changes or replacements will fall within the protection scope of the application.

Claims

1. A method for constructing a creep constitutive model, characterized in that, include: Construct the creep curve for the deceleration creep stage: e P =βln(αt+1), Constructing the creep curve for the constant-rate creep stage: Constructing the creep curve for the accelerated creep phase: e T =θ(exp[ω(tt S / T )]-1), The parameters of this creep morphological model are correlated with temperature and stress: Constructing a creep constitutive model: e c = e p + e s + e T ; in, ε P ε S ε T Creep strain is defined for the deceleration creep stage, the constant-rate creep stage, and the accelerated creep stage. The creep strain rates are for the deceleration creep stage, the constant creep stage, and the acceleration creep stage. The initial creep rate during the deceleration creep phase; t represents the operating time considering creep; t P / S This marks the transition point between the deceleration creep stage and the constant-rate creep stage. t S / T This marks the transition point between the constant-rate creep stage and the accelerated creep stage. α and β are parameters of the deceleration creep stage curve, where α is a parameter characterizing the curvature of the deceleration creep stage curve. At t = 0 s, the initial creep rate of the deceleration creep stage is... ω and θ are parameters of the accelerated creep stage curve, with ω being a parameter characterizing the curvature of the accelerated creep stage curve at t = t S / T At time, creep rate during constant-rate creep stage C is a constant; ε P / S The creep strain during the transition between the deceleration creep stage and the constant-rate creep stage; A0, A1, and A2 are parameters of the creep constitutive model, corresponding to α and ω can have different parameter values; T is the temperature at which creep occurs; σ is the stress during creep; E is the elastic modulus of the material.

2. The method for constructing a creep constitutive model according to claim 1, characterized in that, Also includes: Based on the creep curves corresponding to different creep temperatures and stresses, the initial creep rate of the deceleration creep stage is fitted: Based on the creep curves corresponding to different creep temperatures and stresses, the curvature of the curve during the deceleration creep stage is fitted: α=exp{b1+b2 / T+b3In(sinh(b4σ / E))}; Based on the creep curves corresponding to different creep temperatures and stresses, the creep rate during the constant-rate creep stage is fitted: Based on the creep curves corresponding to different creep temperatures and stresses, the curvature of the accelerated creep stage curve is fitted: ω=exp{d1+d2 / T+d3In(sinh(d4σ / E))}; in, a1, a2, a3, and a4 are the engineering parameters of the creep constitutive model for the initial creep rate during the deceleration creep stage; b1, b2, b3, and b4 are the engineering parameters of the creep constitutive model representing the degree of curvature of the curve during the deceleration creep stage. c1, c2, c3, and c4 are the creep constitutive model engineering parameters for the creep rate during the constant-rate creep stage; d1, d2, d3, and d4 are the engineering parameters of the creep constitutive model representing the degree of curvature of the curve during the accelerated creep stage.

3. The method for constructing a creep constitutive model according to claim 2, characterized in that, When fitting the curvature of the deceleration creep stage curve to different creep temperatures and stresses, the curvature of the deceleration creep stage curve is determined by the correspondence between the transition times of the deceleration creep stage and the constant-rate creep stage. When fitting the curvature of the accelerated creep stage curve to the creep curves corresponding to different creep temperatures and stresses, the curvature of the accelerated creep stage curve is determined by the corresponding relationship at the end of the accelerated creep stage: in, To accelerate the creep rate at the end of the creep phase; t total This is to accelerate the end of the creep stage.

4. The method for constructing a creep constitutive model according to claim 1, characterized in that, Also includes: Based on the elastic modulus measurement data of the material at different temperatures, the relationship between the elastic modulus of the material and temperature is fitted: E=E0+E1T+E2T 2 +E3T 3 +E4T 4 +E5T 5 ; in, E0, E1, E2, E3, E4, and E5 are coefficients used to fit the elastic modulus of the creeping material at the temperature during creep.

5. The method for constructing a creep constitutive model according to claim 1, characterized in that, Also includes: The duration of the constant-rate creep stage is fitted using the creep strain rate of the constant-rate creep stage: in, K0, K1, K2, K3, K4, and K5 are coefficients that fit the creep strain rate of the constant-rate creep stage to the duration of the constant-rate creep stage.

6. A method for predicting creep in aero-engine turbine blades, characterized in that, include: Construct a three-dimensional finite element model of the turbine blade, apply a working load to it, and calculate the stress, strain, and temperature at the nodes of the three-dimensional finite element model of the turbine blade. Based on the stress, strain, and temperature of the nodes in the three-dimensional finite element model of the turbine blade, the creep strain and creep stress are calculated using the creep constitutive model construction method described in any one of claims 1-4.

7. The method for predicting creep in aero-engine turbine blades according to claim 6, characterized in that, If the calculation of creep strain and creep stress does not converge, adjust the time increment step until convergence is achieved.

8. The method for predicting creep in aero-engine turbine blades according to claim 6, characterized in that, The material parameters of the turbine blade at different temperatures are obtained by interpolation of the material parameters at a specific temperature.

9. The method for predicting creep in aero-engine turbine blades according to claim 6, characterized in that, Working loads include centrifugal loads, aerodynamic loads, and temperature loads.

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