CN115931532B - Electric power high-temperature part damage state judging method based on correction time fractional method - Google Patents
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Abstract
The application discloses a method for judging the damage state of an electric power high-temperature part based on a correction time fraction method, which comprises the following steps: obtaining a plurality of samples with the same material and dividing the samples into three parts; performing a fatigue test on the first part of samples, performing a creep test on the second part of samples, and performing a creep fatigue test on the third part of samples; acquiring fatigue damage parameters based on the fatigue test data, and acquiring creep damage parameters based on the creep test data; determining fatigue damage based on fatigue behavior of the creep fatigue test, and determining creep damage based on creep behavior of the creep fatigue test; predicting the cycle life of the creep fatigue test specimen based on the fatigue damage and the creep damage; the total damage state of the high-temperature electric component at any time is judged based on the accumulated fatigue damage and the accumulated creep damage. The method is modified based on a widely accepted time fractional method, has definite physical significance from the classical energy point of coupling creep strain dissipation, is applicable to various creep fatigue loads, and has high prediction accuracy.
Description
Technical Field
The application belongs to the field of life prediction and damage assessment, and particularly relates to a method for judging a damage state of an electric power high-temperature part based on a correction time score method.
Background
In the fields of aviation, aerospace, petrochemical industry and the like, many parts such as transmission rotation, compression bearing and the like run in a severe high Wen Bianzai environment for a long time. The past numerous catastrophic failure cases have led scientists to increasingly recognize that failure of typical life limiting components, such as turbine rotors, nuclear reactor components, and aero-engine turbine components, is not caused by a single fatigue failure, most often failure caused by fatigue and creep interactions at high temperatures. Therefore, damage assessment and life prediction technology under creep fatigue interaction load are one of the most concerned problems of equipment design and manufacture.
The linear damage accumulation method is the most commonly used creep fatigue damage assessment method, and the precondition of the method is to accurately calculate the fatigue damage and creep damage in the cyclic loading process. Fatigue damage is typically expressed in terms of life fraction, but creep damage is more difficult to calculate due to stress relaxation introduced by load retention, and several versions have been deduced. Creep damage, expressed in time fractions, is widely accepted and has been adopted by ASME III-NH (boiler and pressure vessel design Specification) and RCC-MR (Nuclear island mechanical facilities design and construction Specification). The accuracy of this approach has proven to be significantly lower than the creep damage representation that takes into account energy dissipation. In addition, the stress-strain hybrid control creep fatigue load developed in recent years presents a significant challenge to existing approaches. Therefore, the application needs to invent a high-temperature component creep fatigue damage state judging method based on a time score method and fused with an energy dissipation concept so as to meet the recognition and judgment of damage states under various creep fatigue loads.
Disclosure of Invention
The application aims to provide a method for judging the damage state of an electric power high-temperature part based on a correction time fractional method so as to solve the problems in the prior art.
In order to achieve the above object, the present application provides a method for determining a damaged state of an electric power high-temperature component based on a correction time-division method, comprising the steps of:
obtaining a plurality of samples with the same material, and dividing the plurality of samples into a first part of samples, a second part of samples and a third part of samples;
performing a fatigue test on the first part of samples to obtain fatigue test data;
performing a creep test on the second part of samples to obtain creep test data;
performing a creep fatigue test on the third part of samples to obtain creep fatigue data;
acquiring fatigue damage parameters based on the fatigue test data, and acquiring creep damage parameters based on the creep test data;
acquiring fatigue damage of the creep fatigue test based on the fatigue damage parameters and the fatigue behavior of the creep fatigue test; acquiring creep damage of the creep fatigue test based on the creep damage parameters and the creep behavior of the creep fatigue test;
predicting a cycle life of a creep fatigue specimen based on the fatigue damage and the creep damage;
the total damage state of the high-temperature electric component at any time is judged based on the accumulated fatigue damage and the accumulated creep damage.
Optionally, the fatigue damage parameter is obtained based on the fatigue test data, and the creep damage parameter is obtained based on the creep test data, which comprises the following steps:
acquiring a relation between a fatigue strain amplitude and a cycle life based on the fatigue test data;
and obtaining key variables and relations among the key variables based on the creep test data, wherein the key variables comprise creep life, creep rupture strain, creep strain energy dissipation rate, critical creep strain energy dissipation rate and initial creep evolution.
Optionally, the critical creep strain energy dissipation rate is obtained based on the creep test data, and the process includes:
the critical creep strain energy dissipation rateIs determined according to the distribution of creep test points in a base 10 double logarithmic coordinate system, wherein the abscissa of the double logarithmic coordinate system is creep strain energy dissipation rate +.>The ordinate is creep rupture strain epsilon f The method comprises the steps of carrying out a first treatment on the surface of the In this coordinate system, all creep test points will show two possible trends; first, if the creep rupture strain ε f Always with the creep strain energy dissipation rate +.>Is increased by the increase of (2), then it is considered that there is no critical creep strain energy dissipation rate +.>Second, if the rate of energy dissipation is +.>Is increased in creep rupture strain epsilon f If a saturation value exists, the minimum creep strain energy dissipation rate corresponding to the saturation value is considered to be critical creep strain energy dissipation rate +.>
Optionally, the fatigue damage of the creep fatigue test is obtained based on the fatigue damage parameter and the fatigue behavior of the creep fatigue test, and the process comprises the following steps:
based on the relation between the fatigue strain amplitude and the cycle life and the fatigue strain evolution of the creep fatigue test half life cycle along with time, the rain flow counting method is adopted to obtain the strain amplitude born in the actual loading process,further, the fatigue damage of the creep fatigue test is determinedThe following formula is shown:
wherein Ni (Δε i ) For a strain amplitude of delta epsilon i Cycle life of fatigue test of (a), strain amplitude delta epsilon i The actual bearing strain amplitude after being determined by a rain flow method, p i For the strain amplitude delta epsilon i Is a ratio of (c) to (d).
Optionally, obtaining the creep damage of the creep fatigue test based on the creep damage parameter and the creep behavior of the creep fatigue test comprises the following steps:
based on the creep behavior of the half life cycle of the creep fatigue test, a creep strain energy dissipation rate evolution rule is obtained, the strain control creep fatigue and the stress strain hybrid control creep fatigue test all follow the creep strain energy dissipation rate evolution of the index, as shown in the following formula,
wherein The creep strain energy dissipation rate at the time of the load retention t is represented, p represents the dissipation rate evolution coefficient, and q represents the dissipation rate evolution index;
obtaining creep strain evolution term of correction time fractional methodThe following formula is shown:
wherein the creep coefficient C 1 Creep time related index C 2 The creep stress related indexes k are all the creep damage parameters; the elastic modulus E is the basic performance of the test material and the retention time t d Load retention stress sigma of hybrid control creep fatigue test d All are test conditions of creep fatigue test; relaxation stress of half life cycle of strain control creep fatigue testPeak stress sigma of first cycle of strain control creep fatigue test 0 Creep strain +/for half life cycle of hybrid control creep fatigue test>All are test data obtained by creep fatigue test;
obtaining a creep strain energy dissipation rate related term R of a correction time fractional method ENE The following formula is shown:
wherein the stress-induced creep failure coefficient S, the stress-induced creep failure index n, the failure coefficient E based on the creep strain energy dissipation rate c And the failure index m based on the creep strain energy dissipation rate is the creep damage parameter, sigma d (t) is the evolution of the retention stress over time, given by:
wherein the stress relaxation coefficient p r Stress relaxation index q r Obtained by fitting a stress relaxation curve during strain retention; for the mixed control creep fatigue, the retention stress belongs to the test input parameter and is constant and always kept at sigma d ；
Creep strain evolution termRelated to creep strain energy dissipation Rate term R ENE Multiplying to obtain fatigue damage of creep fatigue test>The following formula is shown:
optionally, predicting the cycle life of the creep fatigue test specimen based on said fatigue damage and said creep damage comprises:
based on the fatigue damage and the creep damage, the cycle life of the creep fatigue test sample is predicted by using a linear damage accumulation rule.
Optionally, the step of judging the total damage state of the high-temperature electric power component at any time based on the accumulated fatigue damage and the accumulated creep damage comprises the following steps:
accumulating according to the cycle time based on the fatigue damage and the creep damage to obtain accumulated fatigue damage and accumulated creep damage, and further obtaining a continuous creep fatigue failure envelope;
for any creep fatigue loaded component, calculating accumulated fatigue damage and accumulated creep damage, and finally judging the damage state of the creep fatigue loaded component at any time by using the continuous creep fatigue failure envelope curve: if the damage state point is outside the failure envelope, the material is judged to be failed, otherwise, the material is judged to be not failed.
The application has the technical effects that:
(1) According to the application, the influence of the changed strain amplitude is included in the fatigue damage, so that the fatigue damage is more accurate;
(2) The application corrects based on widely accepted time fractional method, and has definite physical meaning in terms of classical energy of coupling creep strain dissipation;
(3) The application has wide applicability and is mainly embodied on material applicability and creep fatigue load applicability;
(4) The method has high life prediction precision, and can judge the damage state of the material under any creep fatigue loading moment.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
FIG. 1 is a flow chart of a method for determining a damaged state of an electric power high-temperature component based on a correction time-division method according to the present application;
FIG. 2 is a graph of predicted life results for P92 steel in an embodiment of the application;
FIG. 3 is a graph of predicted lifetime results for 304 stainless steel in an embodiment of the application;
FIG. 4 is a graph of predicted lifetime results for GH4169 alloy in an embodiment of the application;
FIG. 5 is a continuous creep fatigue failure envelope in an embodiment of the present application;
fig. 6 is a graph showing a creep fatigue damage state determination in the embodiment of the present application.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
It should be noted that the steps illustrated in the flowcharts of the figures may be performed in a computer system such as a set of computer executable instructions, and that although a logical order is illustrated in the flowcharts, in some cases the steps illustrated or described may be performed in an order other than that illustrated herein.
Example 1
As shown in fig. 1, the present embodiment provides a method for determining a damage state of a high-temperature component of electric power based on a correction time-division method, which includes the following steps:
step S1, taking a plurality of samples of the same material, and performing three different types of tests at the same temperature. Carrying out strain control fatigue tests with the same strain rate and different strain amplitudes on the first part of samples to obtain fatigue test data [ national standard GB/T26077-2010 ], and turning to step S2; carrying out creep tests of different stresses on the second part of samples to obtain creep test data [ national standard GB/T2039-2012 ], and turning to step S3; performing creep fatigue tests on a third part of the samples (including a strain control creep fatigue test [ American Standard ASTM E2714-13 ] and a stress-strain hybrid control creep fatigue test [ Zhang T, wang X, ji Y, et al, periodic deformation and damage mechanisms of 9%Cr steel under hybrid stress-strain controlled creep fatigue interaction loadings [ J ]. International Journal of Fatigue, (2021), 151:106357 ]), and obtaining creep fatigue data, and simultaneously transferring to step S4 and step S5;
step S2, obtaining the relation between the fatigue strain amplitude and the cycle life according to the strain control fatigue test result, specifically as shown in a formula (1),
in the formula (1), E represents the elastic modulus of the material at the test temperature, the fatigue strength coefficient sigma' and the fatigue strength index n 1 Fatigue ductility coefficient ε' and fatigue ductility index m 1 Can be obtained by fitting.
The process proceeds to step S4.
Step S3, obtaining a plurality of key parameters of creep life, fracture strain, creep strain energy dissipation rate, critical creep strain energy dissipation rate, initial creep evolution and the like and the relation among the key parameters according to creep test data, wherein the key parameters are specifically as follows:
step S31, creep life t f Is a basic test result parameter, can be easily obtained, and can further be based on the applied creep stress sigma and creep life t f The relation between the two is obtained as shown in a formula (2), wherein the stress-induced creep failure coefficient S and the stress-induced creep are as followsThe failure index n was fitted from the two test data described above.
t f ＝S·σ n (2)
Step S32, creep rupture strain ε f The test result parameter is also a basic test result parameter, and can be easily obtained.
Step S33, creep strain energy dissipation RateFollowing formula (3), wherein σ is creep stress, ε f For creep rupture strain, t f Is creep life. According to the creep strain energy dissipation rate obtained +.>Creep life t in step S31 f The relationship between the two can be obtained as shown in the formula (4). Wherein the failure coefficient E is based on the rate of creep strain energy dissipation c And a failure index m based on the creep strain energy dissipation rate was fitted from the two test data described above.
Step S34, critical creep strain energy dissipation RateCan be determined from the distribution of creep test points in a 10-base double logarithmic coordinate system, wherein the abscissa of the coordinate system is creep strain energy dissipation rate +.>The ordinate is creep rupture strain epsilon f . In this coordinate system, all creep test points will exhibit two possible trends. First, if creep rupture strainε f Always with creep strain energy dissipation rate +.>Is increased by the increase of (2), then it is considered that there is no critical creep strain energy dissipation rate +.>Second, if the rate of energy dissipation is +.>Is increased in creep rupture strain epsilon f If a saturation value exists, the minimum creep strain energy dissipation rate corresponding to the saturation value is considered to be critical creep strain energy dissipation rate +.>
Step S35, initial creep evolution means creep strain ε in the first stage of creep c The relation between (t) and creep time t, which follows formula (5), wherein C 1 For creep coefficient, C 2 And k is creep stress related index. These parameters can be obtained by fitting the creep first stage of creep test under a plurality of groups of different stresses.
The process proceeds to step S5.
Step S4, based on the fatigue strain evolution of the creep fatigue test half life cycle time, obtaining the strain amplitude born in the actual loading process by adopting a rain flow counting method, and further determining the fatigue damage of the creep fatigue testAs shown in formula (6):
wherein Ni (Δε i ) Shows fatigue test (strain amplitude is delta epsilon) i ) The specific relationship thereof has been given by the formula (1). Strain amplitude delta epsilon i The actual bearing strain amplitude after being determined by a rain flow method, p i For the strain amplitude delta epsilon i Is a ratio of (c) to (d).
The process proceeds to step S6.
Step S5, according to creep strain energy dissipation rate evolution of a half life cycle of a creep fatigue test, calculating creep damage of each cycle by utilizing a correction time fractional method, wherein the method comprises the following steps of:
step S51, obtaining a creep strain energy dissipation rate evolution rule of a half life cycle of a creep fatigue test, wherein the strain control creep fatigue and the stress strain hybrid control creep fatigue load all follow the creep strain energy dissipation rate evolution of an index, as shown in a formula (7),
wherein The creep strain energy dissipation rate at the time of the retention t is represented, p represents the dissipation ratio evolution coefficient, and q represents the dissipation ratio evolution index.
Step S52, obtaining creep strain evolution item of correction time fractional methodAs shown in formula (8).
Wherein the creep coefficient C 1 Creep time related index C 2 The creep stress-related index k is obtained in step S35. The elastic modulus E is the basic performance of the test material in the step S1, and the retention time t d Load retention stress sigma of hybrid control creep fatigue test d All are input parameters for the creep fatigue test performed in step S1. Relaxation stress of half life cycle of strain control creep fatigue testPeak stress sigma of first cycle of strain control creep fatigue test 0 Creep strain +/for half life cycle of hybrid control creep fatigue test>All are the results of the creep fatigue test conducted in step S1.
Step S53, obtaining a creep strain energy dissipation rate related term R of a correction time fractional method ENE As shown in formula (9), wherein the critical creep strain energy dissipation rateObtained from step S34, according to step S34, if there is no critical creep strain energy dissipation rate +.>Then the first term of equation (9) is 0, leaving only the second term at 0-t d Integration over.
Further, the dissipation ratio evolution coefficient p in the formula (9), the dissipation ratio evolution index q is obtained by step S51. Stress-induced creep failure coefficient S and stress-induced creep failure index n are obtained from step S31, failure coefficient E based on the rate of dissipation of creep strain energy c And a failure index m based on the creep strain energy dissipation rate is obtained by step S33. Sigma (sigma) d (t) is the evolution of the retention stress over time given by formula (10), wherein the stress relaxation coefficient p r Stress relaxation index q r Obtained by fitting a stress relaxation curve during strain retention. While for hybrid control creep fatigueThe retention stress is a test input parameter and is constant and always kept at sigma d 。
Step S54, the creep strain evolution item in step S52Item R related to creep strain energy dissipation Rate in step S53 ENE Multiplying to obtain fatigue damage of creep fatigue test>As shown in formula (11), each of the parameters has been explained in the foregoing steps.
The process proceeds to step S6.
Step S6, utilizing the linear damage accumulation rule, according to the fatigue damageCreep damage->Predicting the cycle life N of the material under creep fatigue loading c-f Represented by formula (12):
the process proceeds to step S7.
Step S7, calculating accumulated fatigue damage D according to a large amount of creep fatigue failure data f (n) and cumulative creep damage D c (n) as shown in formula (13), wherein n represents the number of cycles. Finally determining the continuous vermicular motionA control parameter α in a fatigue failure envelope, wherein the continuous creep fatigue failure envelope is represented by formula (14).
Wherein D in formula (14) c Represents the total creep damage suffered by creep fatigue failure, D f Indicating the total fatigue damage experienced upon creep fatigue failure.
The process proceeds to step S8.
Step S8, for any creep fatigue load bearing part, based on the determined accumulated fatigue damage D f (n) cumulative creep damage D c (n) and the continuous creep fatigue failure envelope determined in step S7), and finally determining the damage state of the creep fatigue load bearing member at any time:
if the damage state point is outside the failure envelope, the material is judged to be failed, otherwise, the material is judged to be not failed.
Example two
As shown in fig. 2-4, the present embodiment predicts the cycle life of different temperatures and different materials under strain control and stress-strain hybrid creep fatigue load by using a method for determining the damage state of an electric high temperature component based on a modified time-division method according to the present application.
The material selected is P92 steel, 304 stainless steel and GH4169 alloy.
For P92 steel, strain control fatigue test data refer to paper data [ Wang X, zhang W, zhang T, et al A New Empirical Life Prediction Model for 9-12%Cr Steels under Low Cycle Fatigue and Creep Fatigue Interaction Loadings[J ]. Metals,2019,9 (2) ], different stress creep tests refer to paper data [ Kimura K, takahashi Y.evaluation of Long-Term Creep Strength of ASME Grades 91,92,and 122Type Steels[C ]// ASME 2012Pressure Vessels and Piping Conference.2012 ], strain control creep fatigue tests refer to paper data [ Zhang T, wang X, zhang W, et al Fatigue-creep interaction of P steel and modified constitutive modelling for simulation of the responses [ J ]. Metals, (2020), 10:307; zhang T, wang X, zhou D, et al A universal constitutive model for hybrid stress-strain controlled creep-fatigue deformation [ J ]. International Journal of Mechanical Sciences, (2022), 225:107369. the stress strain hybrid control creep fatigue test is described in the paper data [ Zhang T, wang X, ji Y, et al P92 steel core-fatigue interaction responses under hybrid stress-strain controlled loading and a life prediction model [ J ]. International Journal of Fatigue, (2020): 105837; zhang T, wang X, ji Y, et al cycle deformation and damage mechanisms of 9%Cr steel under hybrid stress-strain controlled creep fatigue interaction loadings [ J ]. International Journal of Fatigue, (2021), 151: 106357;
for 304 stainless steel, strain control Fatigue tests and strain control creep Fatigue tests refer to paper data [ Conway J, stentz R, berling J, fatigue, tensie, and relaxation behavior of stainless steels. No. TID-26135.Mar-Test, inc., cincinnati, ohio (USA), 1975 ] creep tests for different stresses refer to paper data [ Sikka V, booker M, assessment of tensile and creep data for Types304and 316stainless steel,Journal of Pressure Vessel Technology (1977) 99:298-313 ];
for GH4169 alloys, strain-controlled fatigue tests, creep tests and strain-controlled creep fatigue tests refer to paper data [ Wang Runzi ] creep-fatigue life prediction models and applications based on energy density dissipation criteria [ D ]. University of eastern chemical, 2019 ].
Firstly, according to the step S2 of the application, the relation between the fatigue strain amplitude and the cycle life is obtained according to the strain control fatigue test result; then, according to the step S3, a plurality of key parameters such as creep life, fracture strain, creep strain energy dissipation rate, critical creep strain energy dissipation rate, initial creep evolution and the like and the relation among the key parameters are determined; then determining fatigue damage according to the relation between the fatigue strain amplitude and the cycle life obtained in the step S2 and the fatigue strain evolution and a rainfall method of the creep fatigue test half life cycle; meanwhile, according to the key parameters and the relation of the creep test obtained in the step S3 and the creep strain energy dissipation rate evolution of the half life cycle of the creep fatigue test, determining creep damage by utilizing a correction time score method; finally, predicting the cycle life of the material under creep fatigue load according to the fatigue damage and the creep damage by utilizing a linear damage accumulation rule.
From the results of fig. 2, 3 and 4, it can be seen whether P92 steel, or 304 stainless steel, or GH4169 alloy; whether it is a strain-controlled creep fatigue or a stress-strain-mixed-controlled creep fatigue test, the life predicted by the present application is within a 2-fold error band. Therefore, the method for judging the creep fatigue damage state of the electric power high-temperature component based on the correction time fraction method has universality on test materials, creep fatigue loads and test temperatures.
Example III
As shown in fig. 5, this embodiment adopts a method for determining a damage state of a high-temperature electric power component based on a correction time-division method according to the present application to determine a continuous creep fatigue failure envelope.
Also, the same test data as in example 1 are used in this example, and then, according to step S2 of the present application, the relationship between the fatigue strain amplitude and the cycle life is obtained from the strain control fatigue test result; then, according to the step S3, a plurality of key parameters such as creep life, fracture strain, creep strain energy dissipation rate, critical creep strain energy dissipation rate, initial creep evolution and the like and the relation among the key parameters are determined; then determining fatigue damage according to the relation between the fatigue strain amplitude and the cycle life obtained in the step S2 and the fatigue strain evolution and a rainfall method of the creep fatigue test half life cycle; meanwhile, according to the key parameters and the relation of the creep test obtained in the step S3 and the creep strain energy dissipation rate evolution of the half life cycle of the creep fatigue test, determining creep damage by utilizing a correction time score method; and finally, calculating accumulated creep damage and accumulated fatigue damage according to a large amount of creep fatigue failure data, so as to determine a continuous creep fatigue failure envelope curve.
From the results of fig. 5, it can be seen that the creep fatigue failure data in the formula (14) in the specification can be obtained.
Example IV
As shown in fig. 6, this embodiment adopts a method for determining a damaged state of an electric power high-temperature component based on a modified time-division method according to the present application to determine a damaged state of a material at any time of strain control and stress-strain hybrid control creep fatigue load.
Also, the same test data as in example 1 are used in this example, and then, according to step S2 of the present application, the relationship between the fatigue strain amplitude and the cycle life is obtained from the strain control fatigue test result; then, according to the step S3, a plurality of key parameters such as creep life, fracture strain, creep strain energy dissipation rate, critical creep strain energy dissipation rate, initial creep evolution and the like and the relation among the key parameters are determined; then determining fatigue damage according to the relation between the fatigue strain amplitude and the cycle life obtained in the step S2 and the fatigue strain evolution and a rainfall method of the creep fatigue test half life cycle; meanwhile, according to the key parameters and the relation of the creep test obtained in the step S3 and the creep strain energy dissipation rate evolution of the half life cycle of the creep fatigue test, determining creep damage by utilizing a correction time score method; and finally, for any creep fatigue loaded component, calculating the accumulated fatigue and accumulated creep damage to which the component is subjected, and finally judging the creep fatigue damage state of the component by matching with the determined continuous creep fatigue failure envelope curve: if the damage state point is outside the envelope, the material is judged to be invalid, otherwise, the material is judged to be not invalid.
As can be seen from the results of fig. 6, a plurality of test damage status points (including different creep fatigue loads) are located within the continuous creep fatigue failure envelope, which indicates that the test samples corresponding to the test points do not fail and are consistent with the actual damage status; other points are located outside the envelope, which indicates that the specimens corresponding to these test points fail and are consistent with the actual damage state. Therefore, the application can judge the damage state of the material under the creep fatigue and the moment.
From the results of example two, example three and example four, it is seen that: by adopting the method provided by the application, the cycle life of different materials under the creep fatigue load of strain control and stress-strain mixed control can be predicted, and the prediction precision is stabilized within a double error band. In addition, based on the creep and fatigue damage of the application, a general creep fatigue damage envelope curve can be provided, and based on the envelope curve, the damage state of the material at any moment under the creep fatigue load can be judged.
The present application is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present application are intended to be included in the scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.
Claims (4)
1. The method for judging the damage state of the electric power high-temperature part based on the correction time fractional method is characterized by comprising the following steps of:
obtaining a plurality of samples with the same material, and dividing the plurality of samples into a first part of samples, a second part of samples and a third part of samples;
performing a fatigue test on the first part of samples to obtain fatigue test data;
performing a creep test on the second part of samples to obtain creep test data;
performing a creep fatigue test on the third part of samples to obtain creep fatigue data;
acquiring fatigue damage parameters based on the fatigue test data, and acquiring creep damage parameters based on the creep test data;
acquiring fatigue damage of the creep fatigue test based on the fatigue damage parameters and the fatigue behavior of the creep fatigue test; acquiring creep damage of the creep fatigue test based on the creep damage parameters and the creep behavior of the creep fatigue test;
and acquiring fatigue damage of the creep fatigue test based on the fatigue damage parameters and the fatigue behavior of the creep fatigue test, wherein the fatigue damage acquiring process comprises the following steps:
based on the relation between the fatigue strain amplitude and the cycle life and the fatigue strain evolution of the creep fatigue test half life cycle along with time, the strain amplitude born in the actual loading process is obtained by adopting a rain flow counting method, and the fatigue damage of the creep fatigue test is further determinedThe following formula is shown:
wherein Ni (Δε i ) For a strain amplitude of delta epsilon i Cycle life of fatigue test of (a), strain amplitude delta epsilon i The actual bearing strain amplitude after being determined by a rain flow method, p i For the strain amplitude delta epsilon i Is the ratio of (2);
and obtaining creep damage of the creep fatigue test based on the creep damage parameters and the creep behavior of the creep fatigue test, wherein the creep damage comprises the following steps:
based on the creep behavior of the half life cycle of the creep fatigue test, a creep strain energy dissipation rate evolution rule is obtained, the strain control creep fatigue and the stress strain hybrid control creep fatigue test all follow the creep strain energy dissipation rate evolution of the index, as shown in the following formula,
wherein The creep strain energy dissipation rate at the time of the load retention t is represented, p represents the dissipation rate evolution coefficient, and q represents the dissipation rate evolution index;
obtaining creep strain evolution term of correction time fractional methodThe following formula is shown:
wherein the creep coefficient C 1 Creep time related index C 2 The creep stress related indexes k are all the creep damage parameters; the elastic modulus E is the basic performance of the test material and the retention time t d Load retention stress sigma of hybrid control creep fatigue test d All are test conditions of creep fatigue test; relaxation stress of half life cycle of strain control creep fatigue testPeak stress sigma of first cycle of strain control creep fatigue test 0 Creep strain +/for half life cycle of hybrid control creep fatigue test>All are test data obtained by creep fatigue test;
obtaining a creep strain energy dissipation rate related term R of a correction time fractional method ENE The following formula is shown:
wherein ,is critical creep strain energy consumptionRate of dissipation, stress-induced creep failure coefficient S, stress-induced creep failure index n, failure coefficient E based on rate of creep strain energy dissipation c And the failure index m based on the creep strain energy dissipation rate is the creep damage parameter, sigma d (t) is the evolution of the retention stress over time, given by:
wherein the stress relaxation coefficient p r Stress relaxation index q r Obtained by fitting a stress relaxation curve during strain retention; for the mixed control creep fatigue, the retention stress belongs to the test input parameter and is constant and always kept at sigma d ；
Creep strain evolution termRelated to creep strain energy dissipation Rate term R ENE Multiplying to obtain fatigue damage of creep fatigue test>The following formula is shown:
predicting a cycle life of a creep fatigue test specimen based on the fatigue damage and the creep damage, the process comprising:
predicting the cycle life of a creep fatigue test sample by using a linear damage accumulation rule based on the fatigue damage and the creep damage;
accumulating according to the cycle time based on the fatigue damage and the creep damage to obtain accumulated fatigue damage and accumulated creep damage, and further obtaining a continuous creep fatigue failure envelope;
the total damage state of the high-temperature electric component at any time is judged based on the accumulated fatigue damage and the accumulated creep damage.
2. The method for determining the damage state of an electric power high-temperature component based on the correction time score method according to claim 1, wherein the fatigue damage parameter is obtained based on the fatigue test data, and the creep damage parameter is obtained based on the creep test data, and the process comprises:
acquiring a relation between a fatigue strain amplitude and a cycle life based on the fatigue test data;
and obtaining key variables and relations among the key variables based on the creep test data, wherein the key variables comprise creep life, creep rupture strain, creep strain energy dissipation rate, critical creep strain energy dissipation rate and initial creep evolution.
3. The method for determining the damage state of the electric power high-temperature component based on the correction time fractional method according to claim 2, wherein the process of obtaining the critical creep strain energy dissipation rate based on the creep test data comprises the following steps:
the critical creep strain energy dissipation rateIs determined according to the distribution of creep test points in a base 10 double logarithmic coordinate system, wherein the abscissa of the double logarithmic coordinate system is creep strain energy dissipation rate +.>The ordinate is creep rupture strain epsilon f The method comprises the steps of carrying out a first treatment on the surface of the In this coordinate system, all creep test points will show two possible trends; first, if the creep rupture strain ε f Always with the creep strain energy dissipation rate +.>Is increased by the increase of (a),then it is considered that there is no critical creep strain energy dissipation rate +>Second, if the rate of energy dissipation is +.>Is increased in creep rupture strain epsilon f If a saturation value exists, the minimum creep strain energy dissipation rate corresponding to the saturation value is considered to be critical creep strain energy dissipation rate +.>
4. The method for determining the damage state of a high-temperature electric power component based on the correction time-division method according to claim 1, wherein the step of determining the total damage state of the high-temperature electric power component at any time based on the accumulated fatigue damage and the accumulated creep damage includes:
for any creep fatigue loaded component, calculating accumulated fatigue damage and accumulated creep damage, and finally judging the damage state of the creep fatigue loaded component at any time by using the continuous creep fatigue failure envelope curve: if the damage state point is outside the failure envelope, the material is judged to be failed, otherwise, the material is judged to be not failed.
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