Equivalent crack optimization iteration method and aero-engine
By using the equivalent crack optimization and iteration method, the problem of lack of basis for decision-making on the impact damage of the compressor disk flow channel surface was solved, and efficient and high-precision remaining life prediction was achieved, meeting aviation safety requirements.
Patent Information
- Application Number
- CN202511000227.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-21
- Publication Date
- 2026-01-13
AI Technical Summary
The lack of existing technology provides a basis for decision-making regarding the impact damage to the compressor disk flow channel surface, making it impossible to effectively predict its remaining lifespan and affecting flight safety.
An equivalent crack optimization iterative method was adopted. Performance parameters were obtained through material tensile, crack propagation and fracture toughness tests. A fatigue crack propagation model was established. Combined with finite element analysis and crack propagation software simulation, the length equivalence factor β was iteratively optimized until the predicted life met the aviation safety requirements.
It achieves efficient and high-precision prediction of the remaining life of compressor disk flow channel surface impact damage, is applicable to different damage types and materials, meets aviation safety requirements, and has strong engineering applicability.
Smart Images
Figure CN121328167A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aero-engine technology, and in particular, to an equivalent crack optimization iterative method. Furthermore, this invention also relates to an aero-engine incorporating the aforementioned equivalent crack optimization iterative method. Background Technology
[0002] Compressor flow channels are a critical component of the compressor section in turbomachinery such as aero engines and gas turbines. During takeoff and landing, aircraft are prone to ingesting metal debris or other hard particles from the surrounding environment into the high-speed airflow channels of the engine, causing impact damage to the compressor blades and rotor flow channels. The damage morphology mainly includes scratch-like or elliptical pit-like damage. Under cyclic loading, this damage significantly accelerates the initiation of fatigue cracks, leading to premature fatigue failure of the compressor rotor flow channels and seriously threatening flight safety. Therefore, to ensure flight safety and reduce maintenance costs, impact damage should be detected as early as possible during engine operation, and the remaining service life should be predicted based on the damage size. Combined with the overhaul cycle, it should be determined whether the damaged compressor rotor needs repair or replacement.
[0003] However, existing technologies have not conducted relevant research on methods for predicting the remaining life of compressor disc flow channels after impact damage, and there is a lack of basis for decision-making regarding the repair or scrapping of flow channel surfaces. Summary of the Invention
[0004] This invention provides an equivalent crack optimization iteration method and an aero-engine to solve the technical problem of lack of basis for decision-making on impact damage of compressor disk flow channel surface in the prior art.
[0005] According to one aspect of the present invention, an equivalent crack optimization iteration method is provided, applied to the prediction of remaining fatigue life with impact damage, the equivalent crack optimization iteration method comprising:
[0006] S1. Conduct tensile tests, crack propagation tests, and fracture toughness tests on the material respectively to obtain basic material performance parameters and crack propagation performance data;
[0007] S2. The obtained experimental data were fitted using a crack propagation model;
[0008] S3. Conduct impact tests on simulated components;
[0009] S4. Conduct fatigue and crack propagation tests involving impact damage;
[0010] S5. Observe the location of crack initiation and the size of damage;
[0011] S6. Finite element stress analysis;
[0012] S7. Set the preliminary equivalent initial crack method, define the length equivalence factor β = equivalent sharp crack surface length / actual impact damage length, and initially set the β value;
[0013] S8. Calculate crack propagation life;
[0014] S9. Analyze the calculation error of the predicted lifetime and continuously iterate and optimize.
[0015] As a further improvement to the above technical solution, step S2 includes: designing a piecewise linear crack propagation model based on the Paris formula for fitting, with the expression being, where Ci and ni are material parameters, ki is the inflection point of the propagation rate, ΔK is the amplitude of the stress intensity factor, a is the crack length, and N is the number of cycles.
[0016] As a further improvement to the above technical solution, step S3 also includes: using a pre-configured bullet to impact the simulated part at multiple pre-configured angles at a pre-configured impact speed using a high-speed impact test device to cause damage. The pre-configured part includes a square and / or cylindrical shape, and a pre-configured number of pre-configured angles are set in the range of 3° to 10°.
[0017] As a further improvement to the above technical solution, step S3 also includes: using a square bullet with a side length of 3.6mm to impact a simulated object at an impact speed of 200m / s to 300m / s at 10°, 5° and 3° respectively through a high-speed impact testing device to produce scratch-type damage.
[0018] As a further improvement to the above technical solution, step S5 includes: recording the maximum damage length and maximum damage depth at the damage location.
[0019] As a further improvement to the above technical solution, step S6 includes: performing elastoplastic stress analysis on the feature simulation part using finite element software to extract stress gradient data at the design point.
[0020] As a further improvement to the above technical solution, step S8 includes: using crack propagation analysis software to insert an initial crack based on the one determined in step S7 at the design point of the simulated part, inputting the material property parameters from step S1, and calculating the crack propagation life.
[0021] As a further improvement to the above technical solution, step S9 includes:
[0022] S91. Determine if the calculated lifetime is too conservative; if the condition is not met, increase the β value and go to step S8 to recalculate.
[0023] S92. Determine whether the calculated lifetime error is within the three-fold dispersion band. If the condition is not met, reduce the β value and return to step S8 to recalculate.
[0024] As a further improvement to the above technical solution, step S9 also includes:
[0025] S93. Further reduce the β value;
[0026] S94. Determine whether the calculated life of an individual test piece is greater than the test life. If the condition is not met, return to step S92. If the condition is met, output the β value and the iterative optimization ends.
[0027] According to another aspect of the present invention, an aero-engine is also provided, which includes the above-described equivalent crack optimization iteration method.
[0028] The present invention has the following beneficial effects:
[0029] This equivalent crack optimization iterative method obtains material performance parameters and conducts tensile tests, crack propagation tests, and fracture toughness tests. Based on the experimental data, a fatigue crack propagation model is established. Impact tests are conducted on characteristic simulated parts to obtain simulated parts with initial impact damage. Fatigue and crack propagation tests are then conducted on the simulated parts with impact damage to obtain the remaining fatigue life of the simulated parts. Actual damage dimensions are measured. The stress distribution at critical points in the simulated parts is analyzed using finite element software, and the stress gradient at design points is extracted. A fracture mechanics-based method is used to equate the impact damage to initial sharp cracks of a specific size. Combined with crack propagation software simulation, the remaining fatigue life of simulated parts with different damage sizes is predicted. An initial value for the length equivalence factor β is set, and the calculation error of the predicted life is analyzed. Based on the prediction results, the equivalent crack method is iteratively optimized until the predicted life meets the requirements, and the impact damage of the characteristic simulated parts based on fracture mechanics is output. The β value of the impact damage equivalence method is ultimately determined to treat impact damage as a sharp crack with the same damage depth and proportional damage length, meeting aviation safety requirements and possessing strong engineering applicability. This method establishes a crack propagation model by acquiring workpiece test parameters, conducts impact tests on simulated parts by simulating impact damage and performs analysis, and uses commercial crack propagation analysis software to perform analysis and calculation by equating impact damage to an initial sharp crack. This achieves efficient and high-precision prediction of the remaining life of the flow channel surface after impact damage. Furthermore, for different damage types such as pitting, notch, indentation, and processing defects, as well as different test materials and test conditions, this method can ultimately match different length equivalence factors to equate the damage to a sharp crack with the same depth and proportional damage length. The analysis and calculation are then performed using commercial crack propagation analysis software. The method is simple and efficient, with strong applicability.
[0030] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description
[0031] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:
[0032] Figure 1 This is a flowchart of a preferred embodiment of the present invention;
[0033] Figure 2 This is a schematic diagram of the crack propagation characteristics of TC4 special material for compressor disk flow channel surface in the prior art;
[0034] Figure 3 This is a schematic diagram of fitting a piecewise linear crack propagation model based on the Paris formula according to a preferred embodiment of the present invention;
[0035] Figure 4 This is a schematic diagram of the impact damage morphology of a square bullet according to Embodiment 1 of the present invention;
[0036] Figure 5 This is the impact damage morphology of a cylindrical bullet according to Embodiment 1 of the present invention;
[0037] Figure 6 This is a stress distribution cloud diagram of a simulated component with a nominal stress of 600 MPa, representing a preferred embodiment of the present invention.
[0038] Figure 7 This is a schematic diagram of the extracted design point stress gradient according to a preferred embodiment of the present invention;
[0039] Figure 8 This is a schematic diagram comparing the predicted life and the experimental life of an equivalent crack with an actual depth and a length of 1 / 20 in Embodiment 1 of the present invention.
[0040] Legend: Detailed Implementation
[0041] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.
[0042] Figure 1 This is a flowchart of a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of the crack propagation characteristics of TC4 special material for compressor disk flow channel surface in the prior art; Figure 3 This is a schematic diagram of fitting a piecewise linear crack propagation model based on the Paris formula according to a preferred embodiment of the present invention; Figure 4 This is a schematic diagram of the impact damage morphology of a square bullet according to Embodiment 1 of the present invention; Figure 5 This is the impact damage morphology of a cylindrical bullet according to Embodiment 1 of the present invention; Figure 6 This is a stress distribution cloud diagram of a simulated component with a nominal stress of 600 MPa, representing a preferred embodiment of the present invention. Figure 7 This is a schematic diagram of the extracted design point stress gradient according to a preferred embodiment of the present invention; Figure 8 This is a schematic diagram comparing the predicted life and the experimental life of an equivalent crack with an actual depth and a length of 1 / 20 in Embodiment 1 of the present invention.
[0043] like Figure 1 As shown, the equivalent crack optimization iteration method in this embodiment is applied to the prediction of remaining fatigue life with impact damage. The equivalent crack optimization iteration method includes:
[0044] S1. Conduct tensile tests, crack propagation tests, and fracture toughness tests on the material to obtain basic material performance parameters and crack propagation performance data; specifically, this method is applied to predict the remaining life of compressor disc flow channel surface impact damage, and the compressor disc flow channel surface uses TC4 special material;
[0045] S2. The obtained experimental data were fitted using a crack propagation model;
[0046] S3. Conduct impact tests on simulated parts; obtain characteristic simulated parts with different degrees of damage;
[0047] S4. Conduct fatigue and crack propagation tests on specimens with impact damage; specifically, use a hydraulic servo machine to conduct fatigue and crack propagation tests on specimens with impact damage. The test temperature should be close to the actual temperature of the flow channel surface, and the stress ratio should be close to or the same as that of the crack propagation tests conducted previously.
[0048] S5. Observe the location of crack initiation and the size of damage;
[0049] S6. Finite element stress analysis;
[0050] S7. A preliminary equivalent initial crack method is established, defining the length equivalence factor β = equivalent sharp crack surface length / actual impact damage length, with an initial β value set. For example, scratch-type damage is characterized by being "long and shallow." The mainstream defect equivalence principle often equates the depth of the pit or notch to a standard semi-circular crack at a certain ratio. However, for impact damage such as "scratch-type" damage, since the damage itself is relatively long, it is unreasonable to ignore the damage length and only focus on the damage depth when equivaling the crack. This method uses a fracture mechanics-based approach to equate impact damage to a semi-elliptical sharp crack of equal depth and proportional damage length, defining the length equivalence factor β = equivalent sharp crack surface length / actual impact damage length, with an initial β value set to 1.
[0051] S8. Calculate crack propagation life;
[0052] S9. Analyze the calculation error of the predicted lifetime and continuously iterate and optimize.
[0053] Understandably, this equivalent crack optimization iterative method involves obtaining material performance parameters and conducting tensile tests, crack propagation tests, and fracture toughness tests; establishing a fatigue crack propagation model based on the test data; conducting impact tests on characteristic simulated parts to obtain characteristic simulated parts with initial impact damage; conducting fatigue and crack propagation tests on characteristic simulated parts with impact damage to obtain the remaining fatigue life of the simulated parts; measuring the actual damage size; analyzing the stress distribution at critical points of the simulated parts using finite element software and extracting the stress gradient at the design points; using a fracture mechanics-based method to equate the impact damage to initial sharp cracks of a specific size, and combining crack propagation software simulation to predict the remaining fatigue life of simulated parts with different damage sizes; setting an initial value for the length equivalence factor β, analyzing the calculation error of the predicted life, and iteratively optimizing the equivalent crack method based on the prediction results until the predicted life meets the requirements, outputting a characteristic crack based on fracture mechanics. The β value of the simulated impact damage equivalence method is ultimately determined to treat impact damage as a sharp crack with the same damage depth and proportional damage length, meeting aviation safety requirements and possessing strong engineering applicability. This method establishes a crack propagation model by acquiring workpiece test parameters, conducts simulated impact tests on the simulated part, and analyzes the results. By equating the impact damage to an initial sharp crack, commercial crack propagation analysis software is used for analysis and calculation, achieving efficient and high-precision prediction of the remaining life of the flow channel surface after impact damage. Furthermore, for different damage types such as pitting, notch, indentation, and machining defects, as well as different test materials and test conditions, this method can ultimately match different length equivalence factors to equate the damage to a sharp crack with the same depth and proportional damage length. Commercial crack propagation analysis software is used for analysis and calculation, making the operation simple, efficient, and highly applicable.
[0054] It should be noted that in step S1,
[0055] In this embodiment, step S2 includes: designing a piecewise linear crack propagation model based on the Paris formula for fitting, the expression being: In the formula, Ci and ni are material parameters, ki is the inflection point of the propagation rate, ΔK is the stress intensity factor amplitude, a is the crack length, and N is the number of cycles. It should be noted that this method is applied to predict the remaining life of compressor disk flow channel surfaces after impact damage. The compressor disk flow channel surfaces are made of TC4 special material. Since the mainstream crack propagation model is the Paris model, this model is only suitable for describing the second stage of crack propagation, i.e., the stable propagation stage. It cannot describe the "piecewise linear" crack propagation rate curve of TC4 special material using the traditional Paris formula. (Refer to...) Figure 2 Based on the crack propagation characteristics of the TC4 special material in the compressor disk flow channel surface, and referring to Figure 3 A piecewise linear crack propagation model based on the Paris formula was designed for fitting, thereby obtaining better fitting accuracy.
[0056] In this embodiment, step S3 further includes: using a pre-configured bullet to impact a simulated part at multiple pre-configured angles at a pre-configured impact speed using a high-speed impact testing device to generate damage. The pre-configured shape includes square and / or cylindrical, and a pre-configured number of pre-configured angles are set within the range of small angles from 3° to 10°. It should be noted that in the prior art, the study of impact damage often focuses on the blade area. The damage form based on the blade is mainly to produce "pitted" or "notched" damage morphologies. This type of damage needs to be pre-fabricated by using a large angle (≥30°) or a straight impact (90°). This method focuses on the flow channel surface structure to generate "scratch-type" damage. It uses a high-precision high-speed impact testing device to conduct small-angle impacts to ensure consistency. In a specific embodiment, step S3 includes: using a square bullet with a side length of 3.6mm to impact a simulated part at 10°, 5° and 3° at an impact speed of 200m / s to 300m / s using a high-speed impact testing device to generate scratch-type damage.
[0057] In this embodiment, step S5 includes: recording the maximum damage length and maximum damage depth at the damage location; specifically, measuring the impact damage size using a microscopic device. After completing the impact damage test, the damage size should be measured. This method focuses on the maximum damage length and maximum damage depth. The damage depth can be measured by photographing the fracture surface of the test piece after completing the fatigue and crack propagation tests (the fracture location must be at the damage site).
[0058] In this embodiment, step S6 includes: performing elastoplastic stress analysis on the feature simulation part using finite element software and extracting stress gradient data at the design point; specifically, performing elastoplastic stress analysis on the feature simulation part using the finite element ANSYS-Workbench module and extracting stress gradient data at the design point, which is used as the stress distribution for subsequent crack propagation analysis.
[0059] In this embodiment, step S8 includes: using crack propagation analysis software to insert an initial crack based on the one determined in step S7 at the design point of the simulated part, inputting the material property parameters from step S1, and calculating the crack propagation life.
[0060] In this embodiment, step S9 includes:
[0061] S91. Determine if the calculated life is too conservative; if the condition is not met, increase the β value and go to step S8 to recalculate; it should be understood that this method will eventually be directly applied to the prediction of the remaining life of components with impact damage in engineering. Therefore, based on the principle of fully considering safety, the predicted life is required to be lower than the actual life. If the condition is not met, increase the β value and return to step S8 to recalculate. If the condition is met, proceed to step S92 to ensure safety.
[0062] S92. Determine if the calculated life error is entirely within the three-fold dispersion band. If the condition is not met, decrease the β value and return to step S8 to recalculate. The three-fold dispersion band refers to setting the reasonable fluctuation range of the predicted value to be 1 / 3 to 3 times the experimental value, based on the material fatigue life test value. If the predicted value falls within this range, the predicted result is considered to have acceptable consistency with the experimental data, meeting the requirements of engineering design or quality control. For example, define the predicted life index. like If the prediction result is considered to meet the three-fold dispersion band and the predicted lifetime is more conservative; if the condition is not met, decrease the β value and return to step S8.
[0063] Furthermore, step S9 also includes:
[0064] S93. Further reduce the β value; after step S92, the predicted lifetime error meets the requirement of three times the dispersion band and the predicted value is relatively conservative. The value is around 0.33. To achieve better prediction accuracy, the predicted value should be as close to the experimental value as possible. This step makes... Approaching 1 but not greater than 1;
[0065] S94. Determine whether the calculated life of an individual test piece is greater than the test life. If the condition is not met, return to step S92. If the condition is met, output the β value and the iterative optimization ends. The predicted life error of the final equivalent method is within three times the dispersion band and the predicted life is always lower than the test life, which meets the aviation safety requirements and has strong engineering applicability.
[0066] On the other hand, a preferred embodiment of the present invention also provides an aero-engine that applies the above-mentioned equivalent crack optimization iteration method.
[0067] Example 1
[0068] In this embodiment, the equivalent crack optimization iteration method of the preferred embodiment is used to predict the remaining fatigue life of the compressor flow channel surface with impact damage. Impact tests are conducted on characteristic simulated parts. Two types of impact projectiles are used: spherical steel balls with a diameter of 2mm (referred to as cylindrical projectiles) and cubic projectiles with a side length of 3.6mm (referred to as square projectiles). The impact angles are set to 30°, 10°, 5°, and 3°, and the impact velocities are 200m / s and 300m / s (the actual impact velocity will fluctuate, but the fluctuation range will not exceed 10% of the set value). The impact damage forms of the square / circular projectiles are as follows: Figure 4 , Figure 5 As shown, through actual impact tests, it was determined that under the test conditions proposed in this invention, square bullets cause scratch-type damage, while round bullets cause elliptical plastic deformation.
[0069] Based on the TC4 standard crack propagation test data and the crack propagation model proposed in this invention, the fitting result of the crack propagation model under 0 stress ratio is as follows: Figure 3 As shown, the model fits the actual experimental data well, and the specific parameters of the model are shown in Table 1.
[0070] Table 1. Parameters of the piecewise linear extended model for TC4 special material at 150℃, R=0
[0071]
[0072]
[0073] Using the proposed method of equating impact damage to a sharp crack with the same damage depth but 1 / 20th the actual damage length, lifetime prediction was performed using crack propagation analysis software. Figure 8 The prediction error is within three times the dispersion band, and the predicted value is more conservative than the experimental value. The comparison results between the prediction and the experiment are shown in Table 2.
[0074] Table 2 compares the calculated lifespan with the tested lifespan using the 1 / 20 impact damage length equivalence rule.
[0075]
[0076] In this embodiment, the equivalent method for the final determination of the flow channel surface structure (equivalent to a sharp crack of equal depth, β=1 / 20) predicts the lifetime error within three times the dispersion band, and the predicted lifetime is always lower than the test lifetime, which meets aviation safety requirements and has strong engineering applicability.
[0077] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.
[0078] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. An equivalent crack optimization iterative method, applied to predicting remaining fatigue life with impact damage, characterized in that, The equivalent crack optimization iteration method includes: S1. Conduct tensile tests, crack propagation tests, and fracture toughness tests on the material respectively to obtain basic material performance parameters and crack propagation performance data; S2. The obtained experimental data were fitted using a crack propagation model; S3. Conduct impact tests on simulated components; S4. Conduct fatigue and crack propagation tests involving impact damage; S5. Observe the location of crack initiation and the size of damage; S6. Finite element stress analysis; S7. Set the preliminary equivalent initial crack method, define the length equivalence factor β = equivalent sharp crack surface length / actual impact damage length, and initially set the β value; S8. Calculate crack propagation life; S9. Analyze the calculation error of the predicted lifetime and continuously iterate and optimize.
2. The equivalent crack optimization iterative method according to claim 1, characterized in that, Step S2 includes: designing a piecewise linear crack propagation model based on the Paris formula and fitting it, the expression being... In the formula, Ci and ni are material parameters, ki is the inflection point of the propagation rate, ΔK is the stress intensity factor amplitude, a is the crack length, and N is the number of cycles.
3. The equivalent crack optimization iterative method according to claim 1, characterized in that, Step S3 further includes: using a pre-configured bullet to impact a simulated object at multiple pre-configured angles at a pre-configured impact speed using a high-speed impact test device to cause damage. The pre-configured shape includes square and / or cylindrical, and a pre-configured number of pre-configured angles are set in the range of 3° to 10°.
4. The equivalent crack optimization iterative method according to claim 3, characterized in that, Step S3 further includes: using a square bullet with a side length of 3.6mm, and passing it through a high-speed impact testing device to impact a simulated object at an impact speed of 200m / s to 300m / s at 10°, 5° and 3° respectively to produce scratch-type damage.
5. The equivalent crack optimization iterative method according to claim 1, characterized in that, Step S5 includes: recording the maximum damage length and maximum damage depth at the damage location.
6. The equivalent crack optimization iterative method according to claim 1, characterized in that, Step S6 includes: performing elastoplastic stress analysis on the feature simulation part using finite element software and extracting stress gradient data at the design point.
7. The equivalent crack optimization iterative method according to claim 1, characterized in that, Step S8 includes: using crack propagation analysis software to insert an initial crack based on the one determined in step S7 at the design point of the simulated part, inputting the material property parameters from step S1, and calculating the crack propagation life.
8. The equivalent crack optimization iterative method according to claim 1, characterized in that, Step S9 includes: S91. Determine if the calculated lifetime is too conservative; if the condition is not met, increase the β value and go to step S8 to recalculate. S92. Determine whether the calculated lifetime error is within the three-fold dispersion band. If the condition is not met, reduce the β value and return to step S8 to recalculate.
9. The equivalent crack optimization iterative method according to claim 8, characterized in that, Step S9 also includes: S93. Further reduce the β value; S94. Determine whether the calculated life of an individual test piece is greater than the test life. If the condition is not met, return to step S92. If the condition is met, output the β value and the iterative optimization ends.
10. An aircraft engine, characterized in that, The application uses the equivalent crack optimization iterative method as described in any one of claims 1-9.