Available limit value determination method for crack damage of aero-engine part

Abstract

The invention discloses a method for determining an available limit value for crack damage of an aero-engine part. The method comprises the following steps: carrying out part crack damage evolution analysis; according to a part crack damage evolution analysis result, determining a part crack damage available limit value based on aero-engine maintenance inspection; and according to a part crack damage evolution analysis result, determining a part crack damage available limit value based on aero-engine rebuilding inspection.

Description

Technical Field

[0001] This invention relates to the fields of aero-engine strength analysis, life management, and continued airworthiness, and particularly to a method for determining the available limit values ​​for crack damage in aero-engine parts. Background Technology

[0002] According to the requirements of CCAR 33.4 for the preparation of continuing airworthiness documents, engine maintenance manuals and overhaul manuals need to be compiled. During maintenance or overhaul, the usability limits for damaged parts in the manuals should be used to determine whether parts can continue to be used.

[0003] Furthermore, according to the airworthiness verification requirements of CCAR 33.87, CCAR 33.88, and CCAR 33.90, the engine must be completely disassembled after testing, and all components must be inspected to determine whether they are within the usability limits. Therefore, these requirements specify the usability limits for engine components after testing. Determining these usability limits is crucial for supporting the conduct of the tests.

[0004] Crack damage is a typical type of damage to aero-engine components, commonly occurring on parts such as blades and turbine outer rings. Currently, there is no systematic research in China on the establishment of usable limit values ​​for crack damage in aero-engine components. Based on aero-engine maintenance and overhaul strategies, this invention proposes a method for establishing usable limit values ​​for components, providing solid support for the compilation of continued airworthiness documents and the evaluation of various airworthiness tests. Summary of the Invention

[0005] This invention systematically studies the formulation of usable limit values ​​for crack damage in aero-engine parts and proposes a method for determining usable limit values ​​for parts, providing solid support for the compilation of continued airworthiness documents and the evaluation of various airworthiness tests.

[0006] This invention provides a method for determining available limit values ​​for crack damage in aero-engine parts, comprising:

[0007] Perform crack damage evolution analysis on the parts;

[0008] Based on the results of the crack damage evolution analysis of the aforementioned parts, usable limit values ​​for crack damage of parts based on aero-engine maintenance inspections were determined; and

[0009] Based on the results of the crack damage evolution analysis, usable limit values ​​for crack damage of parts based on aero-engine overhaul inspection are determined.

[0010] In one embodiment, the crack damage evolution analysis of the part includes:

[0011] Determine the relevant parameters of crack damage in the part;

[0012] Calculate the crack propagation rate in low-cycle fatigue;

[0013] Calculate high cyclic fatigue strength.

[0014] In one embodiment, determining the parameters related to crack damage in the part includes:

[0015] Based on the material information, geometric characteristics, and finite element analysis results of the aero-engine components, the relevant parameters for crack damage of the components are determined. These parameters include at least geometric parameters, stress, temperature, and material properties.

[0016] In one embodiment, calculating the low-cycle fatigue crack propagation degree includes:

[0017] Based on the crack damage parameters of the part, the relationship between crack length and cycle number is calculated using the Paris formula.

[0018] In one embodiment, calculating the high cyclic fatigue strength includes:

[0019] Based on the crack damage parameters of the part, the relationship between allowable vibration stress and crack length is calculated using stress ratio and shape factor.

[0020] In one embodiment, determining the available limit value for component crack damage based on aero-engine maintenance inspection includes:

[0021] Safety analysis is conducted based on both low-cycle fatigue and high-cycle fatigue, and the minimum value between the available limit value for crack damage of parts that meets the requirements for crack propagation in low-cycle fatigue and the available limit value for crack damage of parts that meets the requirements for high-cycle fatigue strength is taken as the available limit value for crack damage of parts based on aero-engine maintenance inspection.

[0022] The safety analysis, based on both low-cycle fatigue and high-cycle fatigue, includes:

[0023] Regarding low-cycle fatigue, based on the results of the crack damage evolution analysis of the part, taking the critical damage size corresponding to the part failure as the endpoint, and backwards by N times the maintenance and inspection interval, the usable limit value of the part crack damage that meets the requirements of low-cycle fatigue crack propagation is obtained, where N>1.

[0024] In terms of high cyclic fatigue, the damage stress intensity factor is ensured to be within the high cyclic fatigue threshold value, and the allowable limit value for crack damage of the part that meets the high cyclic fatigue strength requirements is obtained based on the relationship between the allowable vibration stress and the crack length and the magnitude of the allowable vibration stress.

[0025] In one embodiment, determining the available limit value for component crack damage based on aero-engine maintenance inspection further includes:

[0026] If the crack damage of a component exceeds the available limit, the maintenance and inspection interval is modified to X times the original, where X < 1, and the safety analysis based on low-cycle fatigue and high-cycle fatigue is repeated to obtain the shortened maintenance and inspection interval for extended service life and the corresponding available limit for component crack damage.

[0027] In one embodiment, determining the available limit value for component crack damage based on aero-engine maintenance inspection further includes:

[0028] If the crack length of the part is greater than a preset length, the damage stress intensity factor exceeds the high-cycle fatigue threshold value, and exceeds the high-cycle fatigue strength limit, then the aero-engine is removed within Y cycles, where Y>1.

[0029] In one embodiment, determining the available limit value for component crack damage based on aero-engine overhaul inspection includes:

[0030] For damage that cannot be detected by maintenance inspections but can be detected by overhaul inspections, the available limit value for component crack damage based on aero-engine overhaul inspections is determined using the same method as the safety analysis based on both low-cycle fatigue and high-cycle fatigue. In this case, the overhaul inspection interval is set to be greater than the maintenance inspection interval. At the same time, it is ensured that the functional degradation of the component does not exceed a preset value.

[0031] For damage that can be detected by both maintenance and overhaul inspections, ensure that the damaged part does not develop to exceed the available limit value for part crack damage based on aircraft engine maintenance inspection within Z overhaul inspection intervals, where Z≥1; and using the available limit value for part crack damage based on aircraft engine maintenance inspection as the endpoint, based on the relationship between crack length and cycle number, backward by Z times the overhaul inspection interval to obtain the available limit value for part crack damage based on aircraft engine overhaul inspection.

[0032] In one embodiment, the method for determining the available limit value for crack damage in aero-engine components further includes:

[0033] The available limit values ​​for component crack damage based on aircraft engine maintenance inspection are used as the available limit values ​​for component crack damage in the aircraft engine maintenance manual.

[0034] The available limit values ​​for component crack damage based on aero-engine overhaul inspection are used as the available limit values ​​for component crack damage in the aero-engine overhaul manual. Attached Figure Description

[0035] The above-described invention and the following detailed description will be better understood when read in conjunction with the accompanying drawings. It should be noted that the drawings are merely examples of the claimed invention. In the drawings, the same reference numerals represent the same or similar elements.

[0036] Figure 1 A flowchart illustrating a method for determining usable limit values ​​for crack damage in parts according to an embodiment of the present invention;

[0037] Figure 2 A typical Kitagawa-Takahashi diagram;

[0038] Figure 3 A schematic diagram illustrating the available limitations for determining the requirements for low-cycle fatigue crack propagation according to an embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram illustrating the economic analysis of the available limit values ​​for the refurbishment manual according to an embodiment of the present invention. Detailed Implementation

[0040] The following detailed description of the features and advantages of the present invention provides sufficient information for any person skilled in the art to understand and implement the invention. Furthermore, based on the specification, claims, and drawings disclosed herein, those skilled in the art can easily understand the related objectives and advantages of the invention. Although the description of the invention is presented in conjunction with preferred embodiments, this does not mean that the features of the invention are limited to these embodiments. On the contrary, the purpose of describing the invention in conjunction with embodiments is to cover other options or modifications that may arise based on the claims of the invention. To provide a thorough understanding of the invention, numerous specific details will be included in the following description. The invention may also be implemented without using these details. Moreover, to avoid confusion or obscuring the focus of the invention, some specific details will be omitted in the description.

[0041] 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.

[0042] Furthermore, the terms "upper," "lower," "left," "right," "top," "bottom," "horizontal," and "vertical" used in the following description should be understood as the orientations shown in the relevant paragraphs and accompanying drawings. These relative terms are for illustrative purposes only and do not imply that the described apparatus must be manufactured or operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0043] It is understood that while terms such as "first," "second," and "third" may be used herein to describe various components, channels, assemblies, regions, layers, and / or parts, these components, channels, assemblies, regions, layers, and / or parts should not be limited by these terms, and these terms are only used to distinguish different components, channels, assemblies, regions, layers, and / or parts. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0044] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0045] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of scope in some embodiments of this application are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0046] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0047] Engine maintenance is generally performed on the wing, such as borescope inspection of high-pressure turbine components. These inspections are conducted at short intervals and require less manpower and financial resources. Engine overhaul, on the other hand, requires removing the engine from the aircraft and completely disassembling its components for maintenance to a better performance condition. This requires more manpower and financial resources and often involves the replacement of parts.

[0048] Existing manuals for aircraft engines and aircraft indicate that the available limits involved in engine maintenance and overhaul differ, and the criteria for determining these available limits also differ. Currently, no one in China has systematically studied the differences between these two strategies, nor has anyone researched methods for determining damage available limits based on maintenance and overhaul strategies. This is detrimental to the compilation of engine continued airworthiness documents and the evaluation of various airworthiness tests.

[0049] Figure 1 A flowchart illustrating a method for determining the available limit value of crack damage in aero-engine parts based on damage tolerance according to an embodiment of the present invention is shown.

[0050] The method includes the following steps:

[0051] Step 101: Analysis of the evolution of crack damage in the part.

[0052] Step 102: Determine the available limit values ​​for component crack damage based on aircraft engine maintenance inspections.

[0053] Step 103: Determine the available limit values ​​for component crack damage based on aircraft engine overhaul inspection.

[0054] The crack damage evolution analysis of the part in step 101 can specifically include the following sub-steps:

[0055] Step 1: Calculate the relevant parameters of crack damage in the part.

[0056] In one embodiment, based on the component material information, geometric characteristics, and finite element analysis results of the aero-engine components, parameters related to component crack damage are obtained. These parameters may include geometric parameters, stress, temperature, material properties, and other parameters.

[0057] Step 2: Calculate the degree of low-cycle fatigue crack propagation.

[0058] In one embodiment, based on the calculated crack damage-related parameters of the part, the relationship between crack length and cycle number is calculated using the Paris formula.

[0059] Step 3: Calculate high-cycle fatigue strength;

[0060] Based on the calculated parameters related to crack damage in the part, the relationship between allowable vibration stress and crack length is calculated using stress ratio and shape factor, i.e., the Kitagawa-Takahashi diagram (KT diagram), as shown below. Figure 2 As shown.

[0061] Determining the usable limit value for component crack damage based on aero-engine maintenance inspection in step 102 may specifically include the following sub-steps:

[0062] Step 1: Conduct a safety analysis based on both low-cycle fatigue and high-cycle fatigue.

[0063] The safety analysis criterion is that, considering the risk of missed damage detection, the component should not fail within N (N>1) times the maintenance and inspection interval. This criterion can be broken down into two aspects: low-cycle fatigue and high-cycle fatigue. Regarding low-cycle fatigue, based on the crack damage evolution calculation results above, using the critical damage size corresponding to component failure as the endpoint, and working backwards through N times the maintenance and inspection interval, we obtain the crack availability limit that meets the low-cycle fatigue crack propagation requirements, such as... Figure 3 As shown. Regarding high-cyclic fatigue, since the frequencies corresponding to high-cyclic fatigue are generally very high, parts are prone to failure in a short period. Therefore, it is necessary to ensure that the damage stress intensity factor is within the high-cyclic fatigue threshold value, meaning that the damage will not propagate due to high-cyclic fatigue. Based on the Kitagawa-Takahashi diagram corresponding to crack damage and the magnitude of vibration stress, the usable limit value for cracks that meet the high-cyclic fatigue strength requirements is obtained. The minimum usable limit value for both low-cycle and high-cycle fatigue is taken to obtain the usable limit value for crack damage from the maintenance manual.

[0064] Step 2: Life Extension Operation Analysis.

[0065] If the crack damage to a component exceeds the usable limit, in order to avoid premature engine removal and improve service economy, a service life extension analysis exceeding the service limit is required. The method is to modify the maintenance and inspection interval to X times the original (X < 1), and repeat the above high- and low-cycle fatigue analysis to obtain the shortened maintenance and inspection interval for extended service life and the corresponding usable limit.

[0066] Step 3: Remove engine analysis.

[0067] If the crack length of a part is too long, the damage stress intensity factor exceeds the high-cycle fatigue threshold value, and exceeds the high-cycle fatigue strength limit, then it is stipulated that the engine should be removed within Y (Y>1) cycles.

[0068] Combining steps one through three above, summarize the available limit values ​​for component crack damage based on aircraft engine maintenance inspections, and write these values ​​into the maintenance manual.

[0069] Determining the usable limit value for component crack damage based on aero-engine overhaul inspection in step 103 may specifically include the following sub-steps:

[0070] Step 1: Security Analysis

[0071] Damage that cannot be detected during maintenance inspections but can be detected during overhaul inspections (such as damage to blade tenons or root extensions) may go undetected. Therefore, it is necessary to confirm the usable limit values ​​from a safety perspective. The procedure for safety analysis in the overhaul manual is the same as that in the maintenance manual; the difference is that the overhaul inspection interval is generally longer than the maintenance inspection interval.

[0072] Step Two: Functional Analysis

[0073] Since engine overhauling requires restoring the engine to a high performance level, the performance of components cannot be excessively degraded. The criterion for functional assessment is to ensure that the functional degradation of components does not exceed a certain value. For example, for blade leading-edge crack damage, the usable limit value for crack damage should be obtained by limiting the leakage and overheating rate, based on the relationship between crack size, leakage rate, and overheating degree.

[0074] Step 3: Economic Analysis

[0075] For damage that can be detected by both maintenance and overhaul inspections (such as blade surface cracks), the possibility of missing detection during overhaul and only being exposed during the next overhaul is very small due to the multiple maintenance inspections within the overhaul cycle. Therefore, for these types of damage, usable limit values ​​should be established based on economic efficiency. The economic analysis criterion is to ensure that the part with the damage will not develop to exceed the usable limit value in the maintenance manual within Z (Z≥1) overhaul inspection intervals, leading to premature overhaul or shortened maintenance inspection intervals, thus impairing engine economy. Before conducting an economic analysis based on the overhaul manual, the corresponding usable limit value in the maintenance manual should be obtained. The operating method is to use the usable limit value corresponding to the maintenance manual as the endpoint, and based on the relationship between crack length and cycle number, backwards by Z times the overhaul inspection interval to obtain the damage size, which is the usable limit value. Figure 4 As shown.

[0076] Combining steps one through three above, summarize the available limit values ​​for component crack damage based on aircraft engine overhaul inspection, and write these values ​​into the overhaul manual.

[0077] Those skilled in the art will understand that the various illustrative components, modules, blocks, units, circuits, systems, and steps described in conjunction with the embodiments disclosed herein can be implemented in hardware, software (including firmware, resident software, microcode, etc.), or a combination of both. To clearly illustrate this interchangeability between hardware and software, the various illustrative components, modules, blocks, units, circuits, systems, and steps described above are generalized in their functional form. Whether such functionality is implemented in hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in different ways for each specific application, but such implementation decisions should not be construed as departing from the scope of the invention.

[0078] This application uses flowcharts to illustrate the operations or steps performed by a system according to embodiments of this application. It should be understood that the preceding or following operations or steps are not necessarily performed in exact order. Instead, various operations or steps can be processed in reverse order or simultaneously. Furthermore, other operations or steps may be added to these processes, or one or more operations or steps may be removed from these processes.

[0079] Unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or the use of other names described in this application are not intended to limit the order of the processes and methods of this application.

[0080] Furthermore, aspects of this application may be manifested as a computer product located on one or more computer-readable media, the product including computer-readable program code.

[0081] A computer-readable signal medium may contain a propagated data signal containing computer program encoding, for example, on baseband or as part of a carrier wave. This propagated signal may take various forms, including electromagnetic, optical, and so on, or suitable combinations thereof. A computer-readable signal medium can be any computer-readable medium other than a computer-readable storage medium, which can be connected to an instruction execution system, apparatus, or device to enable communication, propagation, or transmission of a program for use. The program encoding located on the computer-readable signal medium can be propagated through any suitable medium, including radio, cable, fiber optic cable, RF, or similar media, or any combination of the above media.

[0082] The computer program code required for the operation of each part of this application can be written in any one or more programming languages, including object-oriented programming languages ​​such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C#, VB.NET, Python, etc., conventional procedural programming languages ​​such as C, Visual Basic, Fortran 2003, Perl, COBOL 2002, PHP, ABAP, dynamic programming languages ​​such as Python, Ruby, and Groovy, or other programming languages. This program code can run entirely on the user's computer, or as a standalone software package on the user's computer, or partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer can be connected to the user's computer through any network, such as a local area network (LAN) or wide area network (WAN), or connected to an external computer (e.g., via the Internet), or in a cloud computing environment, or used as a service such as Software as a Service (SaaS).

[0083] Those skilled in the art will understand that information, signals, and data can be represented using any of a variety of different techniques and arts. For example, the data, instructions, commands, information, signals, bits, symbols, and chips described throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or optical particles, or any combination thereof.

[0084] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of both. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read and write information to / from the storage medium. In an alternative, the storage medium may be integrated into the processor. In an alternative, the processor and storage medium may reside as discrete components in the user terminal.

[0085] In one or more exemplary embodiments, the described functionality may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software as a computer program product, the functionality may be stored or transmitted as one or more instructions or code on or through a computer-readable medium. A computer-readable medium includes both computer storage media and communication media, encompassing any medium that facilitates the transfer of a computer program from one location to another. A storage medium may be any available medium accessible to a computer. By way of example and not limitation, such a computer-readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disc storage, disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and is accessible to a computer. Any connection is also legitimately referred to as a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of a medium. As used in this article, disk and disc include compact discs (CDs), laser discs, optical discs, digital multi-purpose discs (DVDs), floppy disks, and Blu-ray discs. Disks typically reproduce data magnetically, while discs reproduce data optically using lasers. Combinations of these should also be included within the scope of computer-readable media.

[0086] The terminology and expressions used above are for descriptive purposes only, and the invention should not be limited to these terms and expressions. The use of these terms and expressions does not mean excluding any illustrative and descriptive equivalent features (or parts thereof), and it should be recognized that various modifications that may exist should also be included within the scope of the claims. Other modifications, variations, and substitutions may also exist. Accordingly, the claims should be considered to cover all such equivalents.

[0087] Similarly, it should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the subject matter of the present application requires more features than those mentioned in the claims.

[0088] Similarly, it should be noted that although the present invention has been described with reference to the specific embodiments described above, those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and various equivalent changes or substitutions can be made without departing from the spirit of the present invention. Therefore, any changes or modifications to the above embodiments within the scope of the essential spirit of the present invention will fall within the scope of the claims of this application.

Claims

1. A method for determining available limit values ​​for crack damage in aero-engine parts, characterized in that, The method includes: Perform crack damage evolution analysis on the parts; Based on the results of the crack damage evolution analysis of the aforementioned parts, usable limit values ​​for crack damage of parts based on aero-engine maintenance inspections were determined; and Based on the results of the crack damage evolution analysis of the parts, the available limit values ​​for crack damage of parts based on the overhaul inspection of aero-engines are determined.

2. The method for determining usable limit values ​​for crack damage in aero-engine parts as described in claim 1, characterized in that, The crack damage evolution analysis of the component includes: Determine the relevant parameters of crack damage in the part; Calculate the crack propagation rate in low-cycle fatigue; Calculate high cyclic fatigue strength.

3. The method for determining usable limit values ​​for crack damage in aero-engine parts as described in claim 1, characterized in that, The parameters related to determining crack damage in the part include: Based on the material information, geometric characteristics, and finite element analysis results of the aero-engine components, the relevant parameters for crack damage of the components are determined. These parameters include at least geometric parameters, stress, temperature, and material properties.

4. The method for determining usable limit values ​​for crack damage in aero-engine parts as described in claim 3, characterized in that, The calculation of low-cycle fatigue crack propagation includes: Based on the crack damage parameters of the part, the relationship between crack length and cycle number is calculated using the Paris formula.

5. The method for determining usable limit values ​​for crack damage in aero-engine parts as described in claim 3, characterized in that, The calculation of high cyclic fatigue strength includes: Based on the crack damage parameters of the part, the relationship between allowable vibration stress and crack length is calculated using stress ratio and shape factor.

6. The method for determining usable limit values ​​for crack damage in aero-engine parts as described in claim 3, characterized in that, The available limit values ​​for determining component crack damage based on aero-engine maintenance inspections include: Safety analysis is conducted based on both low-cycle fatigue and high-cycle fatigue, and the minimum value between the available limit value for crack damage of parts that meets the requirements for crack propagation in low-cycle fatigue and the available limit value for crack damage of parts that meets the requirements for high-cycle fatigue strength is taken as the available limit value for crack damage of parts based on aero-engine maintenance inspection. The safety analysis, based on both low-cycle fatigue and high-cycle fatigue, includes: In terms of low-cycle fatigue, based on the results of the crack damage evolution analysis, taking the critical damage size corresponding to the part failure as the endpoint, and backwards by N times the maintenance and inspection interval, the available limit value of the part crack damage that meets the requirements of low-cycle fatigue crack propagation is obtained, where N>1. In terms of high cyclic fatigue, the damage stress intensity factor is ensured to be within the high cyclic fatigue threshold value, and the allowable limit value for crack damage of the part that meets the high cyclic fatigue strength requirements is obtained based on the relationship between the allowable vibration stress and the crack length and the magnitude of the allowable vibration stress.

7. The method for determining usable limit values ​​for crack damage in aero-engine parts as described in claim 6, characterized in that, The determination of usable limit values ​​for component crack damage based on aero-engine maintenance inspections also includes: If the crack damage of a component exceeds the available limit, the maintenance and inspection interval is modified to X times the original, where X < 1, and the safety analysis based on low-cycle fatigue and high-cycle fatigue is repeated to obtain the shortened maintenance and inspection interval for extended service life and the corresponding available limit for component crack damage.

8. The method for determining usable limit values ​​for crack damage in aero-engine parts as described in claim 6, characterized in that, The determination of usable limit values ​​for component crack damage based on aero-engine maintenance inspections also includes: If the crack length of the part is greater than a preset length, the damage stress intensity factor exceeds the high cycle fatigue threshold value, and exceeds the high cycle fatigue strength limit, then the engine is removed within Y cycles, where Y>1.

9. The method for determining usable limit values ​​for crack damage in aero-engine parts as described in claim 6, characterized in that, The available limit values ​​for determining component crack damage based on aero-engine overhaul inspection include: For damage that cannot be detected by maintenance inspections but can be detected by overhaul inspections, the available limit value for component crack damage based on overhaul inspections of aero-engines is determined using the same method as the safety analysis based on low-cycle fatigue and high-cycle fatigue in claim 6. The overhaul inspection interval is set to be greater than the maintenance inspection interval. At the same time, the functional degradation of the component is ensured not to exceed a preset value. For damage that can be detected by both maintenance and overhaul inspections, ensure that the damaged part does not develop to exceed the available limit value for part crack damage based on aircraft engine maintenance inspection within Z overhaul inspection intervals, where Z≥1; and using the available limit value for part crack damage based on aircraft engine maintenance inspection as the endpoint, based on the relationship between crack length and cycle number, backward by Z times the overhaul inspection interval to obtain the available limit value for part crack damage based on aircraft engine overhaul inspection.

10. The method for determining usable limit values ​​for crack damage in aero-engine parts as described in claim 1, characterized in that, Also includes: The available limit values ​​for component crack damage based on aircraft engine maintenance inspection are used as the available limit values ​​for component crack damage in the aircraft engine maintenance manual. The available limit values ​​for component crack damage based on aero-engine overhaul inspection are used as the available limit values ​​for component crack damage in the aero-engine overhaul manual.

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