Turbine blade life assessment method and system based on material microscopic damage evolution

Abstract

The present invention discloses a turbine blade life assessment method and system based on material micro-damage evolution. The method first generates a test force load spectrum based on an external field rotation speed load spectrum to facilitate creep fatigue testing. Then, based on the generated test force load spectrum, a material-level creep fatigue test and a simulated component-level creep fatigue test are successively performed to construct a material-level creep micro-damage evolution model and a simulated component-level creep micro-damage evolution model. The microstructure evolution of the creep fatigue test is quantitatively described in a step-by-step manner, the relationship between creep damage and microstructure evolution is established, and the accurate prediction of the creep life of the turbine blade is achieved, thereby providing a technical reference for the overhaul and blade replacement of aircraft engines.

Description

Technical Field

[0001] The present invention relates to the technical field of blade remaining life assessment, and in particular, to a method and system for assessing turbine blade life based on material microscopic damage evolution. Background Art

[0002] The existing life assessment methods for aircraft engine turbine blades are mainly based on the service time of the engine blades. The remaining life of the blades is obtained by subtracting the service time from the blade design service life, thereby determining the replacement time interval of the aircraft engine blades. After the key components of the engine have undergone rigorous service environment assessments, their material microstructures will change, such as the rafting of single-crystal turbine blades. The microscopic damage characteristics of the material record the service history it has experienced, which is of great guiding significance for analyzing its remaining life. However, the existing assessment methods do not take into account the damage caused to the material by different working environments such as cruising and acceleration during the service of the aircraft engine, and cannot obtain the real-time use status of nickel-based single crystal materials. The estimation of material degradation is very inaccurate, and the accuracy of life assessment is poor, which increases the use risk of aircraft engine blades and reduces the reliability of aircraft engine use. At the same time, it may also cause material waste and increase engine maintenance costs. Summary of the invention

[0003] The present invention provides a turbine blade life assessment method and system based on material micro-damage evolution, so as to solve the technical problem of poor assessment accuracy in existing turbine blade life assessment methods.

[0004] According to one aspect of the present invention, a method for evaluating the life of a turbine blade based on the evolution of material microscopic damage is provided, comprising the following contents:

[0005] Obtain the external field speed load spectrum and generate the test force load spectrum;

[0006] Conduct material-level creep fatigue tests based on the test force load spectrum, and build a material-level creep micro-damage evolution model based on the test results;

[0007] A simulated component-level creep fatigue test is conducted based on the test force load spectrum, and a simulated component-level creep micro-damage evolution model is constructed based on the test results and the material-level creep micro-damage evolution model;

[0008] The creep life of turbine blades is predicted using a component-level creep micro-damage evolution model.

[0009] Furthermore, the following contents are also included:

[0010] The creep microdamage prediction and analysis of real blades is carried out based on the simulated component-level creep microdamage evolution model, and the working time sampling scheme of the real blade is determined according to the prediction and analysis results. Microscopic tests are carried out on the samples after slicing, and the microscopic test results are compared with the creep microdamage prediction and analysis results. When the two results are significantly different, the simulated component-level creep microdamage evolution model is corrected.

[0011] Furthermore, the process of generating the test force load spectrum includes the following contents:

[0012] The external field speed load spectrum is standardized by using the rain flow counting method to obtain the standard speed load spectrum;

[0013] The creep damage equivalent method is used to shorten the test time of the standard speed load spectrum to form the creep test accelerated load spectrum;

[0014] The creep test acceleration load spectrum is equivalent to the test force load spectrum.

[0015] Furthermore, before conducting material-level creep fatigue tests, the following are also included:

[0016] The creep fatigue life and material creep curve of the material-grade test piece are obtained by the test. Based on the creep fatigue life and material creep curve, the load duration is distributed as 0, t / 4, t / 2, 0.9t and t, where t represents the creep fatigue life.

[0017] Furthermore, the material-level creep micro-damage evolution model is:

[0018]

[0019] in, represents the creep damage rate, represents the initial creep damage rate, ξ, φ, β are temperature-dependent constants, τ c represents the yield stress, r s represents the isotropic hardening stress, represents the steady-state creep rate, τ s represents the hardening stress, represents the shear strain rate on the sth octahedral slip system, d s represents the creep damage factor, χ s represents the kinematic hardening stress, K and n′ are temperature-dependent constants, sign() represents the sign function, and <> represents the yield condition. s -x s |-r s When the slip system is less than 0, the slip system activation condition is not met, and only elastic deformation occurs and is not included in the Medium, d 0represents the initial creep damage variable, d 0 =η 1 d 1 +η 2 d 2 +η 3 d 3 , η 1 , η 2 , η 3 represents the weight coefficient, η 1 +η 2 +η 3 =1,d 1 represents the creep damage variable characterized by the coarsening of the channel width, d 2 represents the creep damage variable characterized by void generation, d 3 Represents the creep damage variable characterized by TCP phase precipitation.

[0020] Furthermore, the simulated component-level creep micro-damage evolution model is:

[0021]

[0022] in, represents the shear strain rate field intensity in the creep affected zone, Ω represents the creep affected zone, S represents the size of the creep affected zone, represents the weight function, It represents the shear strain rate of the node at position (i, j) in the creep affected zone.

[0023] Furthermore, the modified component-level creep micro-damage evolution model is:

[0024]

[0025] in, and are the node shear strain rate considering structural correction and the shear strain rate field intensity in the creep influence zone, is the corrected shear strain rate, k 1 Represents the structural influence coefficient.

[0026] Furthermore, the process of performing creep micro-damage prediction analysis of real blades based on the simulated component-level creep micro-damage evolution model and determining the working time sampling scheme of the real blades according to the prediction analysis results is specifically as follows:

[0027] The creep microdamage evolution model at the simulated component level is used to predict and analyze the creep microdamage of the real blade. The curves of the coarsening of the matrix channel width changing with time, the curves of the generation of holes changing with time, and the curves of the precipitation of TCP phase changing with time are obtained. The working time interval in which the three curves change significantly is determined, and this working time interval is used as the working time sampling scheme for the real blade.

[0028] Furthermore, the geometry, material, temperature and loss control parameters during creep of the simulation-level test piece are all consistent with those of the real blade.

[0029] In addition, the present invention also provides a turbine blade life assessment system based on material microscopic damage evolution, which adopts the above method and includes:

[0030] A load spectrum generation module is used to obtain the external field speed load spectrum and generate the test force load spectrum;

[0031] The first model building module is used to perform material-level creep fatigue tests based on the test force load spectrum, and to build a material-level creep micro-damage evolution model based on the test results;

[0032] The second model building module is used to simulate the component-level creep fatigue test based on the test force load spectrum, and to construct a simulated component-level creep micro-damage evolution model based on the test results and the material-level creep micro-damage evolution model;

[0033] The prediction module is used to predict the creep life of turbine blades by simulating the component-level creep micro-damage evolution model.

[0034] The present invention has the following effects:

[0035] The turbine blade life assessment method based on material microscopic damage evolution of the present invention first generates a test force load spectrum based on an external field speed load spectrum to facilitate creep fatigue testing, and then performs material-level creep fatigue testing and simulated component-level creep fatigue testing based on the generated test force load spectrum to construct a material-level creep microscopic damage evolution model and a simulated component-level creep microscopic damage evolution model, quantitatively describes the microstructural evolution of the creep fatigue test in a step-by-step manner, establishes the relationship between creep damage and microstructural evolution, and realizes accurate prediction of the creep life of turbine blades, thereby providing a technical reference for aircraft engine overhaul and blade replacement.

[0036] In addition, the turbine blade life assessment system based on material microscopic damage evolution of the present invention also has the above advantages.

[0037] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0039] Figure 1 It is a flow chart of a turbine blade life assessment method based on material microscopic damage evolution according to a preferred embodiment of the present invention.

[0040] Figure 2 yes Figure 1 Schematic diagram of the sub-process of step S1 in FIG.

[0041] Figure 3 It is a schematic diagram of the principle of the rain flow counting method of the preferred embodiment of the present invention.

[0042] Figure 4 It is a schematic diagram of the evolution of rafting of a material-level test piece over time under the same load condition obtained in a preferred embodiment of the present invention.

[0043] Figure 5 It is a schematic diagram of the relationship curve between the damage and the width of the substrate channel obtained by fitting in the preferred embodiment of the present invention.

[0044] Figure 6 It is a schematic diagram of the damage field strength method considering stress / temperature gradient in a preferred embodiment of the present invention.

[0045] Figure 7 It is a flow chart of a method for assessing the life of a turbine blade based on the evolution of material microscopic damage according to another embodiment of the present invention.

[0046] Figure 8 It is a schematic diagram of the module structure of a turbine blade life assessment system based on material micro-damage evolution according to another embodiment of the present invention. DETAILED DESCRIPTION

[0047] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0048] like Figure 1 As shown, a preferred embodiment of the present invention provides a turbine blade life assessment method based on material microscopic damage evolution, comprising the following contents:

[0049] Step S1: Obtaining the external field speed load spectrum and generating the test force load spectrum;

[0050] Step S2: performing a material-level creep fatigue test based on the test force load spectrum, and constructing a material-level creep micro-damage evolution model based on the test results;

[0051] Step S3: performing a simulated component-level creep fatigue test based on the test force load spectrum, and constructing a simulated component-level creep micro-damage evolution model based on the test results and the material-level creep micro-damage evolution model;

[0052] Step S4: Predict the creep life of the turbine blade using a simulated component-level creep micro-damage evolution model.

[0053] It can be understood that the turbine blade life assessment method based on material micro-damage evolution of the present embodiment first generates a test force load spectrum based on the external field speed load spectrum to facilitate creep fatigue testing, and then performs material-level creep fatigue testing and simulated component-level creep fatigue testing based on the generated test force load spectrum, so as to construct a material-level creep micro-damage evolution model and a simulated component-level creep micro-damage evolution model, quantitatively describe the microstructure evolution of the creep fatigue test in a step-by-step manner, establish the relationship between creep damage and microstructure evolution, and achieve accurate prediction of the creep life of turbine blades, thereby providing a technical reference for the overhaul and blade replacement of aircraft engines.

[0054] Specifically, Figure 2 As shown, in step S1, the process of generating the test force load spectrum includes the following contents:

[0055] Step S11: standardizing the external field speed load spectrum by using the rain flow counting method to obtain a standard speed load spectrum;

[0056] Step S12: shortening the test time of the standard speed load spectrum by adopting a creep damage equivalent method to form a creep test accelerated load spectrum;

[0057] Step S13: Equivalent the creep test acceleration load spectrum to the test force load spectrum.

[0058] It can be understood that the external speed load spectrum records the operating status of the engine, and is also the design basis for material-level test loads and simulated component-level test loads. A good test load spectrum design can more effectively explore the microscopic damage evolution laws between real blades, simulated component-level and material-level tests. However, the external speed load spectrum is usually very complex and cannot be directly used as a test load. Therefore, the present invention first uses the rain flow counting method to standardize the external speed load spectrum to form a standard speed load spectrum. The rain flow counting method is also called the tower top method. It assumes that raindrops start from peaks and valleys and flow downward. The load cycle is determined according to the trajectory of the raindrop flow. The rain flow method is based on counting the closed stress-strain hysteresis loops one by one, which better reflects the whole process of random loading. Among them, the counting rules of the rain flow counting method of the present invention are as follows:

[0059] (1) The starting point of the raindrops is on the inner side of each peak (or valley) in turn;

[0060] (2) The raindrop falls from the next peak (or valley) until there is a larger peak (or larger valley);

[0061] (3) When the raindrops meet the raindrops flowing down from the roof above, they stop;

[0062] (4) Take out all full cycles and record their respective amplitudes and means.

[0063] For example, Figure 3 As shown, the first raindrop flows down from the inside of the first valley at point 0, falls from point 1 to 1', flows to 5, and then falls. The second raindrop flows from the inside of the peak point 1 to point 2 and falls. Since the peak value at point 1 is lower than the peak value at point 5, it stops. The third raindrop flows from the inside of the valley point 2 to point 3, falls from 3 to 3', flows to 1' and stops when it hits the raindrop flowing from the roof above. By analogy, we can get 7 full cycles: 3-4-3', 1-2-1', 6-7-6', 8-9-8', 11-12-11', 13-14-13' and 12-15-12'.

[0064] Although the waveform of the standard speed load spectrum can be used for testing, if the load is loaded according to the standard speed load, it will usually lead to a long test time, increase the difficulty of the test, and increase the cost of the test. Therefore, the present invention adopts a creep damage equivalence method to reduce the duration of the small state load in the standard load spectrum and increase the duration of the large state load accordingly, and the creep damage in the reduced small state load duration is equivalent to the creep damage in the increased large state load duration. For example, assuming that the large state load σ 1 The creep life is t 1 , small state σ 2 The creep life is t 2 , assuming that the total creep damage of the component is 1, the creep damage per hour corresponding to the large state load is 1 / t 1 , the creep damage per hour corresponding to the small state is 1 / t 2 , assuming that the duration of the small state in the load spectrum is t 2 'The creep damage caused by the small state load is t 2 ' / t 2 , assuming that the large state load is at the equivalent time t 1 The creep damage and small load in the time are consistent, that is: t 1 ' / t 1 =t 2 ' / t 2 , then t 1 '=t 1 *t 2 ' / t 2, thereby forming an accelerated load spectrum for creep tests, improving test efficiency and reducing test costs.

[0065] However, since the rotation speed load spectrum cannot be directly applied to the creep fatigue test, the present invention uses a finite element calculation method to convert the creep test acceleration load spectrum into a force load spectrum that can be used in the test.

[0066] It can be understood that before conducting material-level creep fatigue testing, the following also includes:

[0067] The creep fatigue life and material creep curve of the material-grade test piece are obtained by the test. Based on the creep fatigue life and material creep curve, the load duration is distributed as 0, t / 4, t / 2, 0.9t and t, where t represents the creep fatigue life.

[0068] Specifically, in order to study the influence of load size on the evolution law of material microstructure, different load conditions need to be designed based on the test force load spectrum, and creep tests with different load durations need to be performed under the same load condition. In order to determine the load duration, the present invention first conducts the creep fatigue life of the test piece under each load condition, that is, the creep fatigue test stops after the test piece breaks, and the creep life is recorded as t. Then, the load duration is allocated according to the creep life t combined with the material creep curve, and the load time is allocated as 0, t / 4, t / 2, 0.9t, t. Among them, the non-creep state is recorded at time 0. Generally speaking, creep is in the second stage at t / 4-t / 2, and the microstructure evolution phenomenon is relatively obvious at this time. The state after creep fracture is recorded at time 0.9tt. Such a load duration allocation scheme can obtain the microstructure evolution law of the first, second and third stages of creep.

[0069] It can be understood that in the step S2, the process of conducting the material-level creep fatigue test is specifically as follows: conducting a creep fatigue test on a material-level standard test piece to obtain the creep fatigue life under various load conditions; after the test, determining the key dangerous parts of the test piece, and slicing the test piece at that part, and performing a series of microscopic test pre-treatments such as inlaying, grinding, and polishing on the slices, and then conducting metallographic analysis of the test piece slices and a series of microstructure observations. The instruments used are respectively an ultra-depth of field microscope, an X-ray analyzer, and a scanning electron microscope. For creep fatigue, the present invention focuses on the rafting phenomenon of the microstructure. Under the continuous action of stress and temperature, the rafted structure is destroyed after being stable for a period of time, and the regular rafted structure becomes coarsened and fractured, which is called rafting, and manifests itself as material damage on a macro scale. With the evolution of the rafting of the material microstructure, the material continues to deteriorate, the macroscopic mechanical properties decline, and the remaining life of the material also continues to decay. Through observation, a graph of the evolution of the rafting of the material-level test piece over time under the same load condition can be obtained, as shown in the figure below. Figure 4As shown in the figure, the relationship between material microstructure rafting and creep damage can be studied, and the material-level creep micro-damage evolution curve can be obtained. Under service conditions, with the accumulation of creep damage, the material performance will degrade, which is mainly reflected in the coarsening of the matrix channel width, the generation of pores and the precipitation of topologically closed packed phase (TCP) in the morphology and composition of the microstructure.

[0070] The coarsening of the matrix channel width is usually caused by rafting, which will reduce the Orowan bypass stress and reduce the yield strength of the material. The present invention calculates the critical shear stress τ by establishing a viscoplastic constitutive model that describes the uniaxial tensile behavior of the high-temperature alloy. c After calculating the relationship between yield stress and channel width, the damage factor d 1 Characterize the creep damage caused by the coarsening of the channel width, and use the traditional damage evolution model to fit the relationship between damage and channel width. The Gaussian formula is used for fitting, as shown in Equation 1. The fitting results are shown in Figure 5 shown.

[0071]

[0072] Among them, d 1 represents the creep damage factor characterized by the coarsening of the channel width, a 1 , b 1 、c 1 、a 2 , b 2 、c 2 are all fitting parameters, and x represents the channel width.

[0073] The formation of voids is the most common form of creep damage, which is generally measured by the volume fraction of voids, i.e., porosity. To characterize the degree of damage 2 , the specific expression is:

[0074]

[0075] Among them, d 2 represents the creep damage factor characterized by void generation, represents the initial porosity of the original material before service, It indicates the limiting (maximum) porosity of the material after creep rupture. Represents the porosity during creep.

[0076] In addition, the precipitation of TCP phase is caused by the segregation of refractory elements such as W and Re inside the blade material at high temperature. The precipitation of TCP phase will weaken the solid solution strengthening effect of the matrix phase. Moreover, since it is a hard and brittle phase, it is easy to cause dislocation pile-up and stress concentration to form crack sources, which deteriorates the material properties. Therefore, TCP phase is generally considered to be a harmful phase. Therefore, the volume fraction of TCP phase is adopted in the present invention. Characterization of creep damage 3 , the specific expression is:

[0077]

[0078] Among them, d 3 represents the creep damage factor characterized by TCP phase precipitation, represents the volume fraction of TCP phase precipitated during creep, It indicates the volume fraction of TCP phase in the material when creep rupture occurs.

[0079] On this basis, the present invention introduces a microstructure evolution model, considers the strengthening mode of dislocation movement during creep and the degradation of material mechanical properties caused by creep damage, and develops a creep constitutive model. Since the blade material is a nickel-based single crystal material, its crystal structure is mainly a face-centered cubic crystal structure (FCC). For the FCC structure, the octahedral slip system is more easily activated, so the present invention only considers the octahedral slip system. For the octahedral slip system, the total strain ε m By elastic strain ε e and the inelastic strain ε in Composition, where ε in It can be expressed as the sum of the shear strains on the octahedral slip system, specifically:

[0080] ε m =ε e +ε in Formula (4)

[0081]

[0082] in, represents the shear strain rate on the sth octahedral slip system, P 0 s represents the orientation factor of the octahedral slip system.

[0083]

[0084] in, represents the slip direction vector of the sth octahedral slip system, represents the normal vector of the slip surface, and the superscript T represents the transpose.

[0085] but:

[0086] σ=D:ε e Formula (7)

[0087] Where σ represents the elastic stress and D represents the elastic matrix of the material.

[0088] Then the shear stress on the slip system is expressed as:

[0089]

[0090] The shear strain rate on the sth octahedral slip system is It can be expressed as:

[0091]

[0092] Among them, τ s and d s denote hardening stress and creep damage factor, respectively, s represents the kinematic hardening stress, which is used to describe the Bauschinger effect. Since the load during creep is constant, the Bauschinger effect will basically not occur, so it can also be ignored. K and n′ are temperature-related constants, and sign() represents the sign function. <> represents the yield condition, when |τ s -x s |-r s When the slip system is less than 0, the slip system activation condition is not met, and only elastic deformation occurs and is not included in the In. s It represents the isotropic hardening stress, also known as the resistance stress, which can be expressed as the sum of the resistance stresses under different dislocation motion strengthening mechanisms. The calculation expression is:

[0093]

[0094] in, represents the initial resistive stress due to solid solution strengthening, are the resistive stress caused by dislocation, the resistive stress caused by Orowan bypass stress, and the resistive stress caused by shear stress, respectively. 0 It indicates the proportion of dislocations that bypass the γ′ phase when they encounter it, and the remaining proportion (1-p 0 ) will cut the γ′ phase.

[0095] For materials that have been in service for a period of time at high temperatures, due to the accumulation of creep damage, the microstructure inside the material has changed, and its mechanical properties have degraded, resulting in a decrease in the remaining creep life over time. Therefore, in combination with the creep damage quantification method, the present invention introduces an initial creep damage variable d in the creep constitutive model for evaluating the creep damage of the service material. 0 , so for formula (9), it can be rewritten as:

[0096]

[0097] d 0 =η 1 d 1 +η 2 d 2 +η 3 d 3 Formula (12)

[0098] Among them, η 1 , η 2 , η 3 Represent the weight coefficients of the three types of damage factors, η 1 +η 2 +η 3 =1.

[0099] The microstructure evolution model does not appear explicitly in the creep constitutive model, but is indirectly introduced by affecting the dislocation movement resistance through the change of the matrix channel width. Therefore, based on the traditional phenomenological KR damage evolution model and combining the damage evolution law, the present invention establishes a creep damage evolution model dominated by both the shear stress and the shear strain rate, that is, the material-level creep microscopic damage evolution model is expressed as:

[0100]

[0101] in, represents the creep damage rate, represents the initial creep damage rate, ξ, φ, β are temperature-dependent constants, τ c represents the yield stress, r s represents the isotropic hardening stress, represents the steady-state creep rate.

[0102] Therefore, combining the microscopic test results of various load conditions can study the relationship between load and microstructure rafting, obtain the parameters in each formula, and thus establish a blade material-level creep microscopic damage evolution model.

[0103] It can be understood that in step S3, the process of conducting the simulated component level creep fatigue test is consistent with the material level creep fatigue test process in step S2, and the only difference is that the test piece is different, that is, the material level test piece is replaced by the simulated component level test piece, so the specific process of the simulated component level creep fatigue test will not be repeated here. Among them, the geometry, material, temperature and loss control parameters of the simulated component level test piece in the creep process are consistent with the real blade. For simulated parts with blade structural characteristics, in addition to considering the load, the influence of stress gradient and temperature gradient on creep microdamage must also be considered. The present invention uses the blade material level creep microdamage evolution model to predict the blade simulated component level creep microdamage evolution and creep life, and then compares the predicted results with the test results to analyze the influence of stress gradient and temperature gradient caused by structural characteristics on the predicted results. However, in the finite element calculation, the creep damage is no longer characterized by the damage parameter of a point, but the influence of stress / temperature gradient is considered. The present invention draws on the stress-strain field intensity method to consider the damage parameter distribution of nodes in a certain area, such as Figure 6 As shown. Among them, the expression of the simulated component-level creep microscopic damage evolution model constructed based on the creep damage field intensity method is:

[0104]

[0105] in, It represents the shear strain rate field intensity in the creep influence zone, Ω represents the creep influence zone, which can be selected according to the actual situation. Generally, a sphere centered on the danger point is selected. S represents the size of the creep influence zone. represents the weight function, where b 1 is a parameter related to the shear strain rate, represents the shear strain rate of the node at position (i, j) in the creep influence zone, which is calculated based on formula (11), is the shear strain rate at the most dangerous point, α 1 is the direction angle, and r is the distance from the danger point. The creep damage field strength method characterizes creep damage by the shear strain rate field strength in a region rather than a danger point. Finally, according to formula (14) and the analysis results, the material-level microscopic damage evolution model is modified to To replace the formula (13) The creep micro-damage evolution model of blade simulation component level is established as follows:

[0106]

[0107] It can be understood that in step S4, the creep life of the turbine blade can be predicted by using the simulated component-level creep micro-damage evolution model, specifically: the creep damage rate is obtained according to formula (15): As time goes by, the creep damage parameter d s will also increase when d s When the accumulation reaches 1, the test piece is in creep failure, and the time recorded at this time is the creep life.

[0108] Alternatively, if Figure 7 As shown, in another embodiment of the present invention, the turbine blade life assessment method based on material microscopic damage evolution also includes the following contents:

[0109] Step S5: Predict and analyze the creep microdamage of the real blade based on the simulated component-level creep microdamage evolution model, and determine the working time sampling plan of the real blade according to the prediction and analysis results. Perform microscopic testing on the samples after slicing, and compare the microscopic testing results with the creep microdamage prediction and analysis results. When the two results differ greatly, modify the simulated component-level creep microdamage evolution model.

[0110] Specifically, for the experimental study of microstructural damage of real blades, it is first necessary to contact the external field to provide a blade working time sampling plan. In order to improve efficiency, the present invention uses the simulated component-level creep micro-damage evolution model to predict and analyze the creep micro-damage of real blades, and obtains the curve of the coarsening of the matrix channel width over time, the curve of the generation of holes over time, and the curve of the precipitation of the TCP phase over time. Then, the working time interval in which the three curves change significantly is determined, and the working time interval is used as the working time sampling plan of the real blade. Then, samples are taken from the external field according to the working time sampling plan of the real blade, and microscopic tests are performed on the sampled slices. The test method is the same as the blade material-level microscopic test. Finally, the test results are compared with the predicted results to verify the accuracy of the simulated component-level creep micro-damage evolution model. If the verification effect is good, there is no need to modify the model. If the verification effect is not good, it is necessary to modify formula (11) and introduce the structural influence coefficient k 1 , correct formula (11) to:

[0111]

[0112] is the corrected shear strain rate, which is substituted into equations (14) and (15) Right now:

[0113]

[0114] in, and are the node shear strain rate considering structural correction and the shear strain rate field intensity in the creep damage area. At the same time, k can also be calculated based on the actual life. 1 The value of is calculated and corrected, and finally the microscopic damage evolution model of the real blade is constructed.

[0115] In addition, if Figure 8 As shown, another embodiment of the present invention further provides a turbine blade life assessment system based on material microscopic damage evolution, preferably using the assessment method as described above, the system comprising:

[0116] A load spectrum generation module is used to obtain the external field speed load spectrum and generate the test force load spectrum;

[0117] The first model building module is used to perform material-level creep fatigue tests based on the test force load spectrum, and to build a material-level creep micro-damage evolution model based on the test results;

[0118] The second model building module is used to simulate the component-level creep fatigue test based on the test force load spectrum, and to construct a simulated component-level creep micro-damage evolution model based on the test results and the material-level creep micro-damage evolution model;

[0119] The prediction module is used to predict the creep life of turbine blades by simulating the component-level creep micro-damage evolution model.

[0120] It can be understood that the turbine blade life assessment system based on material micro-damage evolution of this embodiment first generates a test force load spectrum based on the external field speed load spectrum to facilitate creep fatigue testing, and then performs material-level creep fatigue testing and simulated component-level creep fatigue testing based on the generated test force load spectrum, so as to construct a material-level creep micro-damage evolution model and a simulated component-level creep micro-damage evolution model, and quantitatively describes the microstructural evolution of the creep fatigue test in a step-by-step manner, establishes the relationship between creep damage and microstructural evolution, and realizes the accurate prediction of the creep life of turbine blades, thereby providing a technical reference for the overhaul and blade replacement of aircraft engines.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A turbine blade life assessment method based on material microscopic damage evolution, characterized in that: Includes the following: Obtain the external field speed load spectrum and generate the test force load spectrum; A material-level creep fatigue test is performed based on the test force load spectrum, and a material-level creep microscopic damage evolution model is constructed based on the test results, wherein the material-level creep microscopic damage evolution model is: in, represents the creep damage rate, represents the initial creep damage rate, ξ, φ, β are temperature-dependent constants, τ c represents the yield stress, r s represents the isotropic hardening stress, represents the steady-state creep rate, τ s represents the hardening stress, represents the shear strain rate on the sth octahedral slip system, d s represents the creep damage factor, χ s represents the kinematic hardening stress, K and n′ are temperature-dependent constants, sign() represents the sign function, and < > represents the yield condition. s -x s |-r s When the slip system is less than 0, the slip system activation condition is not met, and only elastic deformation occurs and is not included in the In the equation, d0 represents the initial creep damage variable, d0=η1d1+η2d2+η3d3, η1, η2, η3 represent weight coefficients, η1+η2+η3=1, d1 represents the creep damage variable characterized by channel width coarsening, d2 represents the creep damage variable characterized by void generation, and d3 represents the creep damage variable characterized by TCP phase precipitation; A simulated component-level creep fatigue test is performed based on the test force load spectrum, and a simulated component-level creep micro-damage evolution model is constructed based on the test results and the material-level creep micro-damage evolution model, wherein the simulated component-level creep micro-damage evolution model is: in, represents the shear strain rate field intensity in the creep affected zone, Ω represents the creep affected zone, S represents the size of the creep affected zone, represents the weight function, represents the shear strain rate of the node at position (i, j) in the creep influence zone; The creep life of turbine blades is predicted using a component-level creep micro-damage evolution model.

2. The turbine blade life assessment method based on material microscopic damage evolution according to claim 1, characterized in that: Also included are the following: The creep microdamage prediction and analysis of real blades is carried out based on the simulated component-level creep microdamage evolution model, and the working time sampling scheme of the real blade is determined according to the prediction and analysis results. Microscopic tests are carried out on the samples after slicing, and the microscopic test results are compared with the creep microdamage prediction and analysis results. When the two results are significantly different, the simulated component-level creep microdamage evolution model is corrected.

3. The turbine blade life assessment method based on material microscopic damage evolution according to claim 1, characterized in that: The process of generating the test force load spectrum includes the following: The external field speed load spectrum is standardized by using the rain flow counting method to obtain the standard speed load spectrum; The creep damage equivalent method is used to shorten the test time of the standard speed load spectrum to form the creep test accelerated load spectrum; The creep test acceleration load spectrum is equivalent to the test force load spectrum.

4. The turbine blade life assessment method based on material microscopic damage evolution according to claim 1, characterized in that: Before conducting material level creep fatigue tests, the following also needs to be included: The creep fatigue life and material creep curve of the material-grade test piece are obtained by the test. Based on the creep fatigue life and material creep curve, the load duration is distributed as 0, t / 4, t / 2, 0.9t and t, where t represents the creep fatigue life.

5. The turbine blade life assessment method based on material microscopic damage evolution according to claim 2, characterized in that: The modified component-level creep micro-damage evolution model is: in, and are the node shear strain rate considering structural correction and the shear strain rate field intensity in the creep influence zone, is the corrected shear strain rate, and k1 represents the structural influence coefficient.

6. The turbine blade life assessment method based on material microscopic damage evolution according to claim 2, characterized in that: The process of performing creep micro-damage prediction and analysis of real blades based on the simulated component-level creep micro-damage evolution model and determining the working time sampling scheme of the real blades according to the prediction and analysis results is specifically as follows: The creep microdamage evolution model at the simulated component level is used to predict and analyze the creep microdamage of the real blade. The curves of the coarsening of the matrix channel width changing with time, the curves of the generation of holes changing with time, and the curves of the precipitation of TCP phase changing with time are obtained. The working time interval in which the three curves change significantly is determined, and this working time interval is used as the working time sampling scheme for the real blade.

7. The turbine blade life assessment method based on material microscopic damage evolution according to claim 1, characterized in that: The geometry, material, temperature and loss control parameters during creep of the simulation-level test piece are all consistent with those of the real blade.

8. A turbine blade life assessment system based on material microscopic damage evolution, using the method according to any one of claims 1 to 7, characterized in that: include: A load spectrum generation module is used to obtain the external field speed load spectrum and generate the test force load spectrum; The first model building module is used to perform material-level creep fatigue tests based on the test force load spectrum, and to build a material-level creep micro-damage evolution model based on the test results; The second model building module is used to simulate the component-level creep fatigue test based on the test force load spectrum, and to construct a simulated component-level creep micro-damage evolution model based on the test results and the material-level creep micro-damage evolution model; The prediction module is used to predict the creep life of turbine blades by simulating the component-level creep micro-damage evolution model.

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