Background
The turbine moving blade is used as a core component of the gas turbine, and is the component with the worst working environment, the most complex structure, the most faults and the highest replacement cost. The high-temperature parts are inevitably subjected to different degrees of thermal mechanical fatigue damage after being placed in service at high temperature, high stress and frequent start and stop for a long time, and the high-temperature parts become decisive factors influencing the service life of the high-temperature parts. In order to reasonably utilize the service life of components and make a reasonable overhaul period and repair scheme to ensure the safe, economic and continuous operation of gas turbine power generation equipment, the method for evaluating the thermal mechanical fatigue life of the oriented alloy material used by the gas turbine moving blade is concerned by researchers at home and abroad.
At present, the domestic and foreign research on the high-temperature alloy thermomechanical fatigue life evaluation method mainly focuses on three aspects: the life prediction models such as the Manson-coffee equation, the microcrack propagation model, the stretching hysteresis energy (Ostergren) and the like have the following defects: the elastic modulus influencing the service life prediction accuracy of the model is used in calculation, the model cannot reflect the fatigue limit of the material, the fatigue limit is inconsistent with the actual situation, the physical significance of the model is unclear, the processing method is complex, and the like. In addition, under the existing cyclic thermal load and mechanical load, the damage mechanism of the material is more complex, and the interaction among fatigue damage, oxidation damage and creep damage is very complex and difficult to quantitatively describe. The thermal mechanical fatigue experiment has great difficulty, long period and high cost, and if experimental data obtained with great cost cannot be reasonably represented and processed to obtain a life prediction model with higher precision, the great waste is caused, and the development of structural strength design and life prediction work is not facilitated. Therefore, the development of the life evaluation method which has a simple expression form, clear equation parameter physical significance and higher life prediction precision and is formed by accelerating the thermal mechanical fatigue test is significant, and becomes an important subject for the research of scholars at home and abroad.
From the current research situation at home and abroad, the existing assessment method for the thermal mechanical fatigue life of the high-temperature part has defects, and the development of the assessment method for the residual thermal mechanical fatigue life of the high-temperature part of the gas turbine, which has strong applicability, relatively simple operation and high accuracy, has important practical significance.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method for evaluating the residual service life of the thermal mechanical fatigue of the oriented alloy material, which quantitatively calculates and obtains the thermal mechanical fatigue life of the oriented alloy material used by the component according to the actual service temperature cycle and the strain range of the component.
The invention is realized by the following technical scheme:
a method for evaluating residual life of oriented alloy material in thermomechanical fatigue comprises the following steps:
step 1, obtaining the service temperature cycle range and the strain load range of the directional alloy material used by the component;
step 2, selecting the same material as the material in the step 1 to prepare an oriented alloy fatigue sample, and performing a thermomechanical fatigue test in the temperature cycle range in the step 1 and under the condition that the temperature cycle range is larger than the strain load range in the step 1 to obtain thermomechanical fatigue temperature cycle times corresponding to the oriented alloy fatigue sample in different strain load ranges;
step 3, determining a thermomechanical fatigue life curve of the directional alloy material according to the obtained different strain load ranges and the corresponding thermomechanical fatigue temperature cycle times;
step 4, determining the total thermo-mechanical fatigue life value of the oriented alloy material used by the component according to the temperature cycle range and the strain load range of the component in the step 1 and by combining the thermo-mechanical fatigue life curve of the oriented alloy material obtained in the step 3;
and 5, subtracting the temperature cycle times of the component in the step 1 according to the total thermal mechanical fatigue life value of the oriented alloy material to obtain the residual life of the oriented alloy material used by the service component.
Preferably, the method of the thermomechanical fatigue test in step 2 is as follows:
the test is carried out on a high-temperature fatigue testing machine, the temperature cycle range is 20-1200 ℃, and the strain load range is 0.5-2%.
Preferably, the different strain ranges Δ ∈ to be obtained in step 3 and the corresponding thermomechanical fatigue cycle times NfLinear fitting of Delta Epsilon-N on dual logarithmic coordinatesfCurve obtained lgNfThe thermomechanical fatigue life curve of the partially oriented alloy material was obtained by logarithm analysis.
Preferably, the expression of the thermomechanical fatigue life curve is as follows:
Nf=c(△ε)n
wherein a, b and c are constants.
Preferably, in the step 4, the corresponding cycle times N are found on the fatigue curve according to the temperature cycle and the strain load actually suffered by the alloy material in the step 1fAnd obtaining the total thermo-mechanical fatigue life value of the high-temperature alloy material used for the component.
Preferably, the directional alloy material is a directional solidification nickel-based superalloy material.
Preferably, the oriented alloy material is DS GTD111, DS GTD-222, DS GTD-444, DS CM-247, DS MGA1400, MAR-M200Hf, DS MAR-M002, SC PWA 1480, SC PWA 1483, SX Ren N5, CMSX-2, CMSX-4, CMSX-10 or TMS 275.
Compared with the prior art, the invention has the following beneficial technical effects:
the method combines the actual service condition, a large-strain accelerated thermal mechanical fatigue test and life model analysis, considers the actual service condition of a service part, and also considers the problems of large error, time consumption and the like of the traditional Manson-Coffin equation, obtains a thermal mechanical fatigue curve of the oriented alloy material used by the part through testing under the conditions of different temperature cycles and large strain ranges, and fits the curve to form a new thermal mechanical fatigue life analysis model. And quantitatively calculating the thermomechanical fatigue life of the oriented alloy material used by the component according to the actual service temperature cycle and the strain range of the component. The method is simple to operate, reliable, accurate in result, high in applicability and universality, and capable of meeting the requirement of evaluating the residual thermo-mechanical fatigue life of the directional alloy material used by the gas turbine and guiding the reasonable formulation of the maintenance plan.
Detailed Description
The present invention will now be described in further detail with reference to the attached drawings, which are illustrative, but not limiting, of the present invention.
As shown in fig. 1 and fig. 2, a method for evaluating the residual life of the thermomechanical fatigue of the oriented alloy material comprises the following steps:
1) and (3) determining test conditions: and obtaining the service temperature cycle and the strain range of the directional alloy material used by the component by a calculation method.
The directionally alloyed materials described above include directionally solidified (including single crystal) nickel base superalloy materials used in modern gas turbine blades, including DS GTD111, DS GTD-222, DS GTD-444, DS CM-247, DS MGA1400, MAR-M200Hf, DS MAR-M002, SC PWA 1480, SC PWA 1483, SX Ren be N5, CMSX-2, CMSX-4, CMSX-10, TMS 275, and the like.
2) Thermo-mechanical fatigue (TMF) test: processing directional alloy fatigue sample according to standard fatigue sample, and under the conditions of different temperature cycles and large strain range, obtaining the accelerated testObtaining a thermomechanical fatigue life curve of the oriented alloy material used by the component, and recording thermomechanical fatigue cycle times N corresponding to different strain ranges Delta epsilon under each temperature cycle conditionf。
The thermo-mechanical fatigue (TMF) test is carried out on a high-temperature fatigue testing machine, the temperature cycle range is 20-1200 ℃, the strain range is 0.5-2%, and the testing times under each condition are 3 times.
3) Establishing a thermomechanical fatigue (TMF) life model: the obtained delta epsilon and NfLinear fitting of Delta Epsilon-N on dual logarithmic coordinatesfCurve, lgN can be obtainedfThe thermomechanical fatigue life curve expression of the oriented alloy material used for the part is obtained logarithmically: n is a radical off=c(△ε)nWherein a, b and c are constants and are obtained by curve fitting.
The thermomechanical fatigue (TMF) life model is a power function of the total strain range versus cycle number.
4) TMF fatigue life analysis: finding out corresponding cycle times N on a fatigue curve according to the actual temperature cycle and strain load of the directional alloy material used by the componentfNamely the total thermal mechanical fatigue life value of the high-temperature alloy material used by the component.
The number of cycles N that have elapsed is subtracted from the total thermo-mechanical fatigue life value according to the following formulatObtaining the residual TMF life N of the oriented alloy material used for the service partr。
Nr=Nf-Nt
The method takes the service load (including temperature cycle and strain range) of the turbine blade of the gas turbine as the load reference condition of the thermomechanical fatigue test, tests the thermomechanical fatigue life of the oriented alloy material used by the part under the conditions of different temperature cycles and large strain ranges, and records the thermomechanical fatigue cycle times N corresponding to different strain ranges Delta epsilon under each temperature cycle conditionf. The obtained delta epsilon and NfLinear fitting of Delta Epsilon-N on dual logarithmic coordinatesfCurve, lgN can be obtainedf=a+b×lg△ε,Obtaining the expression of the thermomechanical fatigue life curve of the oriented alloy material used by the part by logarithm calculation: n is a radical off=c(△ε)nWherein a, b and c are constants and are obtained by curve fitting. Finding out corresponding service life data points N in a thermomechanical fatigue life curve according to the strain range of the actual turbine moving blade in servicefThe number of times that the component has been in service is NtThe residual TMF life estimation formula of the oriented superalloy material used for the component is as follows: n is a radical off-Nt. Taking the oriented alloy material DS GTD111 used by the turbine moving blade in service as an example, the residual fatigue life estimation values of the oriented alloy material DS GTD111 used by the turbine moving blade obtained by the thermal mechanical fatigue life estimation method of the invention are 3760 times respectively, the residual fatigue life test value of the oriented alloy material DS GTD111 used by the turbine moving blade is 3445 times, and the error between the thermal mechanical fatigue life estimation value and the test value is about 9.14 percent.
Example 1
The strain range of a certain local dangerous area of a turbine moving blade of a certain service set is obtained by calculation and analysis, the temperature cycle of the area under the start-stop working condition is 300-900 ℃, and the number of start-stop times is 1350. Intercepting a directional alloy fatigue sample from a DS GTD111 directional superalloy material used by the component, and testing the thermal mechanical fatigue life of the directional alloy material used by the component under the conditions that the temperature cycle is 300-900 ℃ and the large strain ranges are 1.0%, 0.8%, 0.6% and 0.5% respectively; recording the number of thermo-mechanical fatigue cycles corresponding to different large strain ranges Delta epsilon under each temperature cycle condition as 26, 220, 334 and 2721 times respectively. The obtained delta epsilon and NfLinear fitting of Delta Epsilon-N on double logarithmic coordinatesfCurve, the LogN can be obtainedfThe thermomechanical fatigue life curve expression of the oriented alloy material used for the part is finally obtained from 1.66216 to 4.9079Log Δ ∈: n is a radical off=0.53977(△ε)0.1752. According to the strain range of 0.28% of a local dangerous area of the turbine moving blade in actual service, corresponding life data is found to be about 7110 times in a thermal mechanical fatigue life curve, and the residual directional high-temperature alloy material used by the component is subtracted by 1350 times of the component in serviceTMF lifetime is approximately: 5760 times.
FIG. 3 shows the calculation results of the thermo-mechanical fatigue life of the oriented superalloy material. Taking the DS GTD111 as an example of the oriented alloy material used for the turbine moving blade in service, the thermal mechanical fatigue life evaluation method of the invention is used to obtain that the estimated value of the thermal mechanical fatigue life of the DS GTD111 of the oriented alloy material used for the turbine moving blade is 5110 times under the conditions that the temperature cycle is 300-900 ℃ and the strain range is 0.4%, and the estimated value of the residual thermal mechanical fatigue life is about: 3760 times. The testing value of the thermal mechanical fatigue life of the directional alloy material DS GTD111 used by the turbine moving blade is 4795 times, and the measured value of the residual thermal mechanical fatigue life is about: 3445 times. The error between the estimated value of the residual thermo-mechanical fatigue life and the test value obtained by the thermo-mechanical fatigue life evaluation method is less than 10 percent.
The embodiment result shows that the method for evaluating the residual thermal mechanical fatigue life of the oriented alloy material combines the actual service condition, the large-strain accelerated thermal mechanical fatigue test and the novel life model analysis, not only considers the actual service condition of the service part, but also considers the problems of the traditional Manson-Coffin equation, obtains a thermal mechanical fatigue curve of the oriented alloy material used by the part through testing under the conditions of different temperature cycles and large strain ranges, obtains a new thermal mechanical fatigue life analysis model through fitting the curve, and quantitatively calculates and obtains the thermal mechanical fatigue life of the oriented alloy material used by the part according to the actual service temperature cycle and the strain range of the part.
The invention discloses a method for evaluating residual life of thermomechanical fatigue of an oriented alloy material, which mainly comprises the steps of determining test conditions, carrying out a large-strain accelerated thermomechanical fatigue test, establishing a life model, analyzing the life and the like, testing and obtaining a thermomechanical fatigue curve of the oriented alloy material used by a part under the acceleration conditions of different temperature cycles (the temperature cycle range is between 20 and 1200 ℃) and large strain ranges (the strain range is between 0.5 and 2 percent), and fitting the curve to obtain a new thermomechanical fatigue life analysis model, namely obtaining a power function relation between the total strain range and the cycle frequency. And quantitatively calculating the thermomechanical fatigue life of the oriented alloy material used by the component according to the actual service temperature cycle and the strain range of the component. The method has the advantages of simple operation, reliable method, accurate result, strong applicability and universality, can meet the requirement of residual thermo-mechanical fatigue life evaluation of the directional alloy material used by the gas turbine, guides the reasonable formulation of maintenance plans, is generally suitable for thermo-mechanical fatigue life evaluation of the directional alloy material used by the turbine moving blades of the heavy-duty gas turbine, including directional solidification (containing single crystal) nickel-based high-temperature alloy material used by the turbine blades of the modern gas turbine, and has extremely strong universality. The problem that the service life of high-temperature components of active E-class and F-class gas turbines and even H-class gas turbines is large in error and time-consuming in evaluation by adopting the traditional Manson-coffee equation is solved.
Firstly, the method considers the actual service condition of the service part, also considers the problems of large error, time consumption and the like of the traditional method of the traditional Manson-coffee equation, finally obtains a new thermal mechanical fatigue life analysis model by testing the thermal mechanical fatigue life of the directional alloy material used by the part under the acceleration condition and fitting a life curve, quantitatively calculates the residual thermal mechanical fatigue life of the directional alloy material used by the part, and has extremely strong applicability and accuracy.
Secondly, the method for evaluating the thermomechanical fatigue life of the oriented alloy material used by the component can accurately predict the residual thermomechanical fatigue life of the component, and the thermomechanical fatigue life is a main parameter for determining the performance of the component material.
In addition, the thermomechanical fatigue life evaluation method can accurately evaluate the residual thermomechanical fatigue life of the oriented alloy material used by the component. And determining the available state of the component according to the evaluation result, determining whether the component can be continuously used, repaired and scrapped, and setting a maintenance period. For the component which can be repaired and has a prolonged service life, the component can be continuously used for the next overhaul period after being repaired and prolonged, so that the rejection rate of the component is reduced and great economic benefit is brought.
Finally, the thermomechanical fatigue life evaluation method mainly comprises test condition determination, thermomechanical fatigue (TMF) test, novel thermomechanical fatigue (TMF) life model establishment, thermomechanical fatigue (TMF) life analysis and the like, the main analysis processes of different oriented alloy materials are basically the same, and the test and test workload is less, and the timeliness is high. Therefore, the recovery method provided by the invention has the advantages of low cost, simplicity in operation, high timeliness and convenience for flow operation.
In conclusion, the method is simple to operate, reliable, accurate in result, high in applicability and universality, capable of meeting the requirement of analyzing the residual service life of the turbine moving blade of the gas turbine and guiding the reasonable formulation of a maintenance plan and the determination of a repair service life-prolonging scheme.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.