CN114186444A - Load spectrum compiling method, medium, terminal and application of high-temperature part of aircraft engine - Google Patents
Load spectrum compiling method, medium, terminal and application of high-temperature part of aircraft engine Download PDFInfo
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Abstract
The invention discloses a load spectrum compiling method, medium, terminal and application of a high-temperature component of an aircraft engine, and relates to the technical field of structural integrity of aircraft engines. Performing heat-force multi-field coupling analysis on the evaluated high-temperature component by combining the use working condition and the actually measured flight data, and determining a service life assessment area and typical loaded state parameters thereof; establishing an equivalent conversion model of fatigue-creep load and fatigue load; in order to determine model parameters, the calculated state parameters are used as input conditions, a material test is carried out, and the life cycle number and the damage index corresponding to each stress level and the load-holding time are determined; and identifying the duration of equivalent and small-amplitude cycles in the data compression process, and converting the equivalent and small-amplitude cycles into fatigue cycles by using the established equivalent conversion model. The fatigue-creep load equivalent conversion model established based on material test and simulation analysis is introduced to serve as a technical pivot between a failure mechanism and a cycle counting process of the structure and the material.
Description
Technical Field
The invention relates to the technical field of structural integrity of aero-engines, in particular to a load spectrum compiling method, a computer readable storage medium and an information data processing terminal suitable for high-temperature components of aero-engines.
Background
The research on the structural integrity of the aircraft engine depends on the authenticity of a load spectrum to a great extent, the load spectrum is obtained by properly compressing the load-time history of actually measured flight data, and the statistical processing of the random load history mainly adopts a rain flow counting method at present. The rain flow counting method is a double-parameter counting method which is provided based on the relation between material fatigue damage and stress and strain. Because the counting rule is consistent with the stress-strain hysteresis loop, time-independent key information (average amplitude cycle) can be simply and conveniently extracted, and the service life estimation result obtained based on the method has better correlation with the test result.
The classical rain flow counting method comprises two steps of data compression (steps of pseudo data replacement, constant point compression, peak-valley value detection, small amplitude removal and the like) and cyclic extraction. The equivalence point compression and the ineffective amplitude omission are simplified steps based on the idea that damage is completely contributed by fatigue cycles, a large number of small cycles (particularly the amplitude is below 10%) outside a main cycle in a load process are filtered, and only fatigue cycle information is kept. The theoretical basis is as follows: at lower temperature conditions, the time-dependent creep behavior of the material is generally negligible. However, for hot-end components that are extremely loaded and complex (e.g., aircraft engine turbine disks), the creep behavior of the material at high temperatures becomes significant, and the fatigue-creep interaction during the dwell time significantly limits its useful life. Obviously, at this time, if a significant portion of the damage contributed by the small cyclic loads, which are long in time or have large average stresses, is neglected by the conventional rain flow counting method, the life prediction will be biased toward danger.
The difficulty in solving the technical problems is as follows: in the existing method in the field, only a small cycle of stopping below a certain threshold is regarded as not contributing to damage and is completely rejected, and practice shows that the creep behavior of the material at a high temperature causes the simple rejection of a small amplitude value to bring an unacceptable life evaluation result which is biased to danger. This problem is always lack of a solution which has a certain theory, experimental support and is easy to implement, and becomes one of the aeipathia in the field of structural integrity.
The significance of solving the technical problems is as follows: the existing spectrum-editing method sets a certain threshold value (standard of stress, percentage or fatigue strength limit) according to experience for small-cycle processing methods in a load process, and then considers that the contribution damage is negligible and then eliminates the damage. These methods lack the rationale and accuracy of theory and experimentation. It is particularly noted that the load spectrum processing works are in fact subject to large individual differences. Even if a reasonable threshold value is found in the application, the threshold value is changed to the engines of different models, use units and environments and flight missions, and the threshold value is generally not applicable any more and needs to be determined again. For high temperature conditions, the existing method cannot quantitatively consider the creep contributed by small cyclic load and the increasing trend of fatigue-creep coupled damage along with the increase of temperature, so that the given life prediction result only has reference value. Based on a fatigue-creep equivalent conversion model determined by a material test, the invention can quantitatively convert a large number of small cycles (the small cycle less than 3% of the maximum value in a certain rotating speed spectrum can account for more than 95% of the total number of cycles) and other damages in a load-time sequence and count the damages into a cycle extraction matrix. Particularly, a load spectrum compilation strategy under a high-temperature condition is optimized, load compression and fidelity are well balanced, and technical support is provided for guarantee work such as damage assessment, service life prediction and the like.
Disclosure of Invention
Aiming at the problem that the damage in the load-holding time is neglected or insufficient to be considered by the existing high-temperature condition load processing method, the invention discloses a load spectrum compiling method suitable for high-temperature components of an aircraft engine. Once the model is established, the equivalent transformation ratio of small cycles (including equivalent loads) can be adaptively adjusted to account for the differentiated usage load spectrum. The method has engineering value for load spectrum compilation of other fields (agricultural machinery, aviation and rail transit) and alloy materials.
The load spectrum compiling method suitable for the high-temperature part of the aircraft engine comprises the following steps of:
the method comprises the following steps of firstly, carrying out thermal-force multi-field coupling analysis on an evaluated high-temperature component by combining use conditions and actually measured flight data, and determining a service life assessment area and typical loaded state parameters thereof;
step two, establishing an equivalent conversion model of fatigue-creep load and fatigue load;
step three, in order to determine model parameters, the calculated state parameters are used as input conditions, a material test is carried out, and the life cycle number and the damage index corresponding to each stress level and the load retention time are determined;
and fourthly, identifying the duration of equivalent and small-amplitude cycles in the data compression process, converting the equivalent and small-amplitude cycles into fatigue cycles by using the established equivalent conversion model, superposing the fatigue cycle statistical matrix obtained in the cycle counting process to obtain a total cycle statistical matrix, and verifying the life prediction precision.
In one embodiment, the performing a material test comprises: tensile test, fatigue-creep test under individual and combined loading.
In one embodiment, the first step specifically includes the following steps:
firstly, determining common and typical working condition intervals;
and secondly, determining boundary conditions of finite element calculation according to the actual loading condition of the examined component, and performing multi-field coupling solution.
In one embodiment, the establishment of the equivalent scaled model of fatigue-creep load and fatigue load comprises the steps of:
firstly, determining a model architecture of load conversion processing to be in a second-order polynomial form:
ciis a material parameter;
secondly, determining the relationship between the tensile strength and the temperature of the material by a material tensile test;
thirdly, determining stress S at each temperature T according to the finite element calculation resultTCorresponding to a reference temperature T0Equivalent stress of
And fourthly, carrying out a low-cycle fatigue test, and determining a damage index and further determining model parameters according to the life cycle numbers corresponding to different load-holding times under the condition of single and multi-stage stress level combined loading.
In one embodiment, the determining that the model architecture of the load conversion process is a second-order polynomial form specifically includes the following steps:
firstly, determining a load processing method aiming at a high-temperature condition based on a generalized fatigue-creep load equivalent conversion theory;
according to the fatigue-creep load equivalent conversion theory, if oneGroup fatigue-creep recombination (load-holding time t)BNot equal to 0) another set of pure fatigue (t) loaded with the same peak-to-valley valueB0) the loading contribution is equal, i.e.:
secondly, determining a model architecture of load conversion processing;
the equivalent transformation ratio of the fatigue load to the fatigue-creep composite load can be obtained according to the deformation of the formula (2)
Definition of (1):
wherein, a and b are respectively damage index and cycle number during pure fatigue and fatigue-creep composite loading; n is a radical off，
The service lives of the two are respectively corresponding to the service lives, and the parameters are obtained by low cycle fatigue test; corresponding to a certain operating point (stress level S, dwell time t)BA temperature T),
the meaning of (1) is: t is tBImpairment contributed by 1 cycle when not equal to 0 corresponds to tBWhen equal to 0
One cycle;
thirdly, carrying out adaptive simplification adjustment on the model architecture by combining with actual application conditions;
the fatigue damage to a material caused by the stress level at temperature T, which is determined by the common stress criterion, depends on the stress STAnd tensile strength of material at temperature T
The ratio of (A) to (B); therefore, the stress S corresponding to the temperature T of each working condition point in the solution resultTAre all converted to a certain reference temperature T0Lower isokinetic force
Thus, the equivalent conversion ratio
The definition can be simplified to a form that contains only two parameters:
the left side of the above formula can be determined by polynomial series approximation, and the coefficient is obtained by least square regression test data; taking the fitting precision and the solving difficulty into consideration, selecting a second-order polynomial form:
ciis a material parameter.
In one embodiment, step three specifically includes the following:
firstly, carrying out material tensile tests at different temperatures; obtaining the relationship between the tensile strength and the temperature of the material at different temperatures by the tensile test fitting at different temperatures;
secondly, carrying out low cycle fatigue tests under independent and combined loading; calculating the resultant reference temperature T using finite elements0And its corresponding equivalent stress
As input conditions;
thirdly, determining model parameters by using test data; determining damage indexes of loads at all levels by using life cycle data of single and combined loading tests through a nonlinear loss accumulation method, substituting into equivalent conversion ratio of fatigue load and fatigue-creep composite load
The model parameters are determined by the definitional formula of (2), and the modeling is completed.
In one embodiment, step four specifically includes the following:
firstly, processing an equivalence point; before extracting a peak-valley value in a rain flow counting process, identifying the duration of an equivalent load, calling a model to convert the equivalent load into a fatigue cycle, and compressing the fatigue cycle into a point in an original load-time process;
step two, small amplitude cyclic processing; after extracting the peak-valley value, identifying the small amplitude circulating peak-valley value in the interval above the slow vehicle rotating speed, identifying the position of the circulating peak-valley value in the original process to calculate the alternate load-holding time, and converting the position into fatigue circulation by a model; the small amplitude is defined according to the percentage threshold value which is smaller than a certain rotating speed or stress, and the threshold value is determined by the reduction trend change of the total damage value when the small amplitude is removed according to different amplitudes;
thirdly, completing statistics; obtaining a total cyclic statistical matrix, and superposing the asymmetric stress cyclic statistical matrix obtained in the cyclic extraction step with the converted fatigue cyclic statistical matrix obtained in the previous step to obtain the total cyclic statistical matrix;
fourthly, verifying the life prediction precision; and obtaining damage values of the T-RC and the I-RC by using a life-time fraction prediction method.
Another object of the present invention is to provide a computer-readable storage medium, in which a computer program is stored, which, when being executed by a processor, causes the processor to carry out the method for load-profiling a high-temperature component for an aircraft engine.
Another object of the present invention is to provide an information data processing terminal comprising a memory and a processor, the memory storing a computer program, the computer program, when executed by the processor, causing the processor to execute the load spectrum compilation method suitable for high-temperature components of aircraft engines.
Another object of the present invention is to provide an aircraft engine implementing the method for compiling a load spectrum suitable for high-temperature components of aircraft engines.
The technical scheme provided by the embodiment of the invention has the following beneficial effects:
the fatigue-creep load equivalent conversion model built based on material test and simulation analysis is introduced to serve as a technical pivot between a failure mechanism and a cycle counting process of a structure and a material. Quantitatively converting a large number of small cycles in the load-time sequence and damages such as damages in the load-holding time into a cycle extraction matrix, and once a model is established, the process can be adaptively adjusted for the differentiated load process. Compared with the prior art, the method has the advantages that the prediction precision is improved by two orders of magnitude, and the optimization effect is obvious. The invention provides a breakthrough solution for the compilation work of the component use load spectrum of the determined metal material in various working environments and working processes, and has considerable engineering application prospect.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure.
FIG. 1 is a flow chart of an implementation of a load spectrum compilation method suitable for high-temperature components of an aircraft engine provided by the invention.
Fig. 2 is a theoretical schematic diagram of step S2 provided by the present invention.
Fig. 3 is a schematic diagram of the modeling result of step S3 provided by the present invention.
FIG. 4 is a flowchart illustrating an implementation of step S4;
wherein, fig. 4(a) is a schematic diagram of data processing; FIG. 4(b) is a flow chart of the embodiment.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention is capable of other embodiments than those described herein.
According to one aspect of the disclosure, a load spectrum compiling method suitable for high-temperature components of an aircraft engine comprises the following steps:
s1: performing heat-force multi-field coupling analysis on the evaluated high-temperature component (such as a turbine disc) by combining the use working condition and the actually measured flight data, and determining a service life assessment area and typical state parameters of the service life assessment area under load;
s2: establishing an equivalent conversion model of fatigue-creep load and fatigue load;
(1) determining the model architecture of the load conversion processing to be in a second-order polynomial form:
ciis a material parameter.
(2) Determining the relationship between the tensile strength and the temperature of the material by a material tensile test;
(3) determining stress S at each temperature T according to finite element calculation resultsTCorresponding to a reference temperature T0Equivalent stress of
(4) Carrying out a low-cycle fatigue test, determining a damage index and further determining model parameters according to the life cycle numbers corresponding to different load-holding times under the combined loading of single stress levels and multi-level stress levels;
s3: in order to determine model parameters, the state parameters calculated in the step S1 are used as input conditions, material tests (tensile, fatigue-creep under single and combined loading) are carried out, and the life cycle number and damage index corresponding to each stress level and the load-holding time are determined;
s4: and identifying the duration (load-holding) duration of the equivalent and small-amplitude cycles in the data compression process, converting the equivalent conversion model established in the steps S2 and S3 into a fatigue cycle, superposing a fatigue cycle statistical matrix obtained in the cycle counting process to obtain a total cycle statistical matrix, and verifying the life prediction precision.
In an embodiment of the present disclosure, the step S1 includes the following specific steps:
s11: common and typical working condition intervals are determined. Generally, at least working points such as slow vehicle, cruise and maximum are covered, and the measured flight data of a certain type of engine is taken as an example (hereinafter, this is the case unless specifically stated), as shown in table 1;
s12: and determining boundary conditions of finite element calculation according to the actual loading condition of the examined component, and performing multi-field coupling solution. According to at least one embodiment of the present disclosure, the input information of the thermal-structure finite element calculation includes: material parameters, loading, constraints, thermal boundaries, algorithms. And setting each working condition point as a time sub-step, and carrying out transient analysis.
TABLE 1 high pressure turbine disc calculation parameters under typical conditions
Preferably, multiple fields, thermal-structure-acoustic-vibration-flow, etc., can be coupled simultaneously to maximize the simulation of centrifugal force, thermal stress, aerodynamic shock, rotor vibration, etc., loading.
In an embodiment of the present disclosure, as shown in fig. 2, the step S2 includes the following specific steps:
s21: determining a load processing method aiming at high-temperature conditions based on a generalized fatigue-creep load equivalent conversion theory;
the damage process of the material is considered to be nonlinear, and damage values generated by each stage of load under complex loading are accumulated in a nonlinear mode. The generalized fatigue-creep load equivalent conversion theory considers that: 1) if it isSet of fatigue-creep recombination (dwell time t)BNot equal to 0) another set of pure fatigue (t) loaded with the same peak-to-valley valueB0) damage contributed by loading is equal, i.e.:
here, a small amplitude cycle below a certain threshold is also considered as a payload; in particular, a "small amplitude" may be defined as being less than a certain rotational speed or stress percentage threshold. The threshold is determined by the change of the total damage value falling trend when the total damage value is removed according to different amplitudes, such as 0.3%. According to a large amount of statistics, the small circulation mainly focuses on the rotating speed range with the peak-valley value of more than 80%, which is the region where the engine is frequently used, and the throttle lever moves more in a small range; a part of the slow vehicle rotating speed interval is also provided; the interval below the slow vehicle speed can be ignored.
S22: determining a model architecture of load conversion processing;
the equivalent transformation ratio of the fatigue load to the fatigue-creep composite load can be obtained by the deformation of the S21 formula
Definition of (1):
wherein, a and b are respectively damage index and cycle number during pure fatigue and fatigue-creep composite loading; n is a radical off，
The respective life-time of the two is obtained by a low cycle fatigue (fatigue-creep) test. Corresponding to a certain operating point (stress level S, dwell time t)BA temperature T),
the meaning of (1) is: t is t B1 cycle contribution of damage equivalent when not equal to 0At tBWhen equal to 0
And (4) circulating.
S23: the model architecture is adaptively simplified and adjusted by combining actual application conditions;
the fatigue damage to a material caused by the stress level at temperature T, which is determined by the common stress criterion, depends on the stress STAnd tensile strength of material at temperature T
The ratio of. Therefore, the stress S corresponding to each operating point temperature T in the solution result of step S1 can be obtainedTAre all converted to a certain reference temperature T0Equivalent stress of
Thus, the equivalent conversion ratio
The definition can be simplified to a form that contains only two parameters:
the left side of the above equation can be determined by polynomial series approximation (Weierstrass approximation theorem) and the coefficients are derived from least squares regression test data. Taking the fitting precision and the solving difficulty into consideration, selecting a second-order polynomial form:
ciis a material parameter.
In an embodiment of the present disclosure, the step S3 includes the following specific steps:
s31: carrying out material tensile tests at different temperatures; the relationship between the tensile strength and the temperature of the material at different temperatures is obtained by fitting tensile tests at different temperatures, taking a certain nickel-based superalloy material as an example:
determining that the stress at different temperatures corresponds to the equivalent stress at the reference temperature:
according to the actual working temperature of the engine in the application case and the finite element analysis result, taking the reference temperature T of the root part of the sealing labyrinth behind the turbine disc0The temperature was 550 ℃.
S32: developing low cycle fatigue (fatigue-creep) tests under individual and combined loading; calculating the result reference temperature T by using finite elements0And its corresponding equivalent stress
As input conditions, the equivalent stresses at the reference temperature of 550 ℃ of 4 typical working condition points are 1066MPa, 1144 MPa, 1244MPa and 1287MPa respectively. Low cycle fatigue (fatigue-creep) tests were carried out under individual and combined loading. The test waveform is controlled to be triangular/trapezoidal wave, and the load retention time does not exceed the maximum load retention time in the load history.
S33: determining model parameters by using the test data; determining damage indexes of loads at all levels by using life cycle data of single and combined loading tests through a nonlinear loss accumulation method, and substituting the damage indexes into an equivalent conversion ratio of fatigue load to fatigue-creep composite load
The definitional formula of (2) determines the model parameters to complete modeling, as shown in fig. 3;
in one embodiment of the present disclosure, as shown in fig. 4(a) and 4(b), the step S4 includes the following specific steps:
s41: and (5) processing the equivalent points. Before extracting peak-valley values in a rain flow counting process, identifying the duration (load retention time) of an equivalent load, calling a model to convert the duration into fatigue cycle, and compressing the fatigue cycle into a point in an original load-time process;
s42: and (5) carrying out small-amplitude cyclic processing. After extracting the peak-valley value, identifying a small amplitude circulating peak-valley value in a region above the rotating speed of the slow vehicle, identifying the position of the circulating peak-valley value in the original process to calculate the alternate load-holding time, and converting the model into fatigue circulation; the "small amplitude" may be defined as a threshold value less than a certain rotational speed or stress percentage, the threshold value being determined by the change in the trend of the total damage value decrease when removed at different amplitudes, e.g. 0.3%. The small circulation mainly focuses on the rotating speed range with the peak-valley value of more than 80%, which is the area where the engine is frequently used, and the throttle lever moves more in a small range; a part of the slow vehicle rotating speed interval is also provided; the interval below the slow vehicle speed can be ignored.
S43: completing statistics to obtain a total cyclic statistic matrix; and superposing the asymmetric stress cyclic statistical matrix obtained in the cyclic extraction step with the converted fatigue cyclic statistical matrix obtained in the previous step to obtain a total cyclic statistical matrix. Selecting flight data of a certain type of aero-engine 591 group, wherein the total working time is 532.3 hours, and counting stress cycle spectra of a life assessment area by respectively using a traditional rain flow method (T-RC) and the method (I-RC) disclosed by the invention, as shown in Table 2. The total number of cycles counted for the two is 35508 and 65574 respectively.
TABLE 2 high pressure turbine disk equivalent stress cycle statistics
S44: and verifying the life prediction precision. The damage values of the T-RC and I-RC obtained from Table 2 by the life-time score prediction method are 0.0988 and 0.3935, respectively. It can be calculated that the damage considered by the conversion of the equivalent points of the local speed interval corresponds to 61.34% of the pure fatigue cycle (T-RC result), whereas the damage introduced by the full condition equivalent and small amplitude load handling of the method of the present disclosure corresponds to 298.25% of the pure fatigue cycle. The predicted residual life of the two methods is 4857.2h and 822.0h respectively; the total life was 5388.5h and 1354.4 h. At present, the given service life of a high-pressure turbine disc of the engine is 1250h, and the predicted deviation of three methods obtained by calculation is respectively as follows: 331.08% and 8.35%.
Therefore, the service life prediction result of the load spectrum compiling method suitable for the high-temperature part of the aircraft engine is accurate and obvious in optimization; fully verifies that the load treatment under the high-temperature condition must be considered aiming at the fatigue-creep coupling damage in the load-holding time; the larger error obtained by the traditional rain flow method is due to neglect or under-consideration of this part of the load, which contributes most of the total damage (74.89% in the present embodiment). The method is suitable for the structural integrity research of components with extreme and complex service environments, such as key components at the hot end of the engine, and the like, and can give a load processing result which is real and reliable enough on the premise of known flight data and not harsh test conditions; and has sufficient reference value for other fields with high-temperature condition load spectrum compilation requirements.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
It will be understood that the present disclosure is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the disclosure should be limited only by the attached claims.
Claims (10)
1. A load spectrum compiling method suitable for high-temperature components of an aircraft engine is characterized by comprising the following steps of:
the method comprises the following steps of firstly, carrying out thermal-force multi-field coupling analysis on an evaluated high-temperature component by combining use conditions and actually measured flight data, and determining a service life assessment area and typical loaded state parameters thereof;
step two, establishing an equivalent conversion model of fatigue-creep load and fatigue load;
step three, in order to determine model parameters, the calculated state parameters are used as input conditions, a material test is carried out, and the life cycle number and the damage index corresponding to each stress level and the load retention time are determined;
and fourthly, identifying the duration of equivalent and small-amplitude cycles in the data compression process, converting the equivalent and small-amplitude cycles into fatigue cycles by using the established equivalent conversion model, superposing the fatigue cycle statistical matrix obtained in the cycle counting process to obtain a total cycle statistical matrix, and verifying the life prediction precision.
2. The method of claim 1, wherein the developing a material test comprises: tensile test, fatigue-creep test under individual and combined loading.
3. The method for compiling a load spectrum applicable to a high-temperature component of an aircraft engine according to claim 1, wherein the first step specifically comprises the following steps:
firstly, determining common and typical working condition intervals;
and secondly, determining boundary conditions of finite element calculation according to the actual loading condition of the examined component, and performing multi-field coupling solving.
4. The method for compiling a load spectrum suitable for an aircraft engine high-temperature component according to claim 1, wherein the establishment of the equivalent conversion model of the fatigue-creep load and the fatigue load comprises the following steps:
firstly, determining a model architecture of load conversion processing to be in a second-order polynomial form:
ciis a material parameter;
secondly, determining the relationship between the tensile strength and the temperature of the material by a material tensile test;
thirdly, determining stress S at each temperature T according to the finite element calculation resultTCorresponding to the reference temperature T0Equivalent stress of
And fourthly, carrying out a low-cycle fatigue test, and determining a damage index and further determining model parameters according to the life cycle numbers corresponding to different load-holding times under the condition of single and multi-stage stress level combined loading.
5. The method for compiling a load spectrum applicable to a high-temperature component of an aircraft engine according to claim 4, wherein the step of determining that the model architecture of the load conversion process is in the form of a second-order polynomial specifically comprises the following steps:
firstly, determining a load processing method aiming at a high-temperature condition based on a generalized fatigue-creep load equivalent conversion theory;
according to the fatigue-creep load equivalent conversion theory, if a set of fatigue-creep compounds (the load-holding time t)BNot equal to 0) another set of pure fatigue (t) loaded with the same peak-to-valley valueB0) damage contributed by loading is equal, i.e.:
secondly, determining a model architecture of load conversion processing;
the equivalent transformation ratio of the fatigue load to the fatigue-creep composite load can be obtained according to the deformation of the formula (2)
Definition of (1):
wherein, a and b are respectively damage index and cycle number during pure fatigue and fatigue-creep composite loading; n is a radical off，
The service lives of the two are respectively corresponding to the service lives, and the parameters are obtained by a low cycle fatigue test; corresponding to a certain operating point (stress level S, dwell time t)BA temperature T),
the meaning of (1) is: t is tBImpairment contributed by 1 cycle when not equal to 0 corresponds to tBWhen equal to 0
One cycle;
thirdly, carrying out adaptive simplification adjustment on the model architecture by combining with actual application conditions;
the fatigue damage to a material caused by the stress level at temperature T, which is determined by the common stress criterion, depends on the stress STAnd tensile strength of material at temperature T
The ratio of (A) to (B); therefore, the stress S corresponding to the temperature T of each working condition point in the solution resultTAre all converted to a referenceTemperature T0Equivalent stress of
Equivalent conversion ratio
The definition can be simplified to a form that contains only two parameters:
the left side of the above formula can be determined by polynomial series approximation, and the coefficient is obtained by least square regression test data; taking the fitting precision and the solving difficulty into consideration, selecting a second-order polynomial form:
ciis a material parameter.
6. The method for compiling a load spectrum suitable for a high-temperature component of an aircraft engine according to claim 1, wherein the third step specifically comprises the following steps:
firstly, carrying out material tensile tests at different temperatures; obtaining the relationship between the tensile strength and the temperature of the material at different temperatures by fitting tensile tests at different temperatures;
secondly, carrying out low cycle fatigue tests under independent and combined loading; reference temperature T using finite element calculation0And its corresponding equivalent stress
As input conditions;
thirdly, determining model parameters by using test data; determining damage indexes of loads at all levels by using life cycle data of single and combined loading tests through a nonlinear loss accumulation method, substituting into equivalent conversion ratio of fatigue load and fatigue-creep composite load
The model parameters are determined by the definitional formula of (2), and the modeling is completed.
7. The method for compiling a load spectrum suitable for a high-temperature component of an aircraft engine according to claim 1, wherein the fourth step specifically comprises the following steps:
firstly, processing an equivalence point; before extracting a peak-valley value in a rain flow counting process, identifying the duration of an equivalent load, calling a model to convert the equivalent load into a fatigue cycle, and compressing the fatigue cycle into a point in an original load-time process;
step two, small amplitude cyclic processing; after extracting the peak-valley value, identifying the small amplitude circulating peak-valley value in the interval above the slow vehicle rotating speed, identifying the position of the circulating peak-valley value in the original process to calculate the alternate load-holding time, and converting the model into fatigue circulation; the small amplitude is defined according to the percentage threshold value less than a certain rotating speed or stress, and the threshold value is determined by the descending trend change of the total damage value when the small amplitude is removed according to different amplitudes;
thirdly, completing statistics; obtaining a total cyclic statistical matrix, and superposing the asymmetric stress cyclic statistical matrix obtained in the cyclic extraction step with the converted fatigue cyclic statistical matrix obtained in the previous step to obtain the total cyclic statistical matrix;
fourthly, verifying the life prediction precision; and obtaining damage values of the T-RC and the I-RC by using a life-time fraction prediction method.
8. A computer-readable storage medium, in which a computer program is stored which, when being executed by a processor, causes the processor to carry out a method for load-profiling a high-temperature component for an aircraft engine according to any one of claims 1 to 7.
9. An information data processing terminal, characterized in that the information data processing terminal comprises a memory and a processor, the memory stores a computer program, and the computer program is executed by the processor, so that the processor executes the load spectrum compilation method suitable for the high-temperature component of the aircraft engine according to any one of claims 1 to 7.
10. An aircraft engine, characterized in that it implements a load spectrum compilation method suitable for high-temperature components of aircraft engines, as claimed in any one of claims 1 to 7.
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| CN116029180A (en) * | 2023-03-30 | 2023-04-28 | 湖南云箭科技有限公司 | Airborne store fatigue simulation method and system |
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| CN115983081A (en) * | 2023-03-17 | 2023-04-18 | 湖南云箭科技有限公司 | Method and system for processing parameters of outsourcing object for replacing prototype airborne equipment |
| CN116029180A (en) * | 2023-03-30 | 2023-04-28 | 湖南云箭科技有限公司 | Airborne store fatigue simulation method and system |
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