CN117332622B

CN117332622B - Crack propagation life determining method, device, equipment and storage medium

Info

Publication number: CN117332622B
Application number: CN202311632094.XA
Authority: CN
Inventors: 李瑾亮; 杨学伟
Original assignee: Wuxi Huatian Aviation Power Co ltd; Wuxi Huatian Gas Turbine Co ltd
Current assignee: Wuxi Huatian Aviation Power Co ltd; Wuxi Huatian Gas Turbine Co ltd
Priority date: 2023-12-01
Filing date: 2023-12-01
Publication date: 2024-02-13
Anticipated expiration: 2043-12-01
Also published as: CN117332622A

Abstract

The invention relates to the technical field of fatigue life calculation, and discloses a crack propagation life determining method, a crack propagation life determining device, crack propagation life determining equipment and a storage medium, wherein the crack propagation life determining method comprises the following steps: acquiring the material size, the initial crack length and the crack propagation parameters of a structure to be analyzed; acquiring a history load history of a structure to be analyzed in actual use; calculating critical crack length of a crack part of the structure to be analyzed based on the history load process and the material size; calculating an equivalent stress level of the historical load history based on the load cycle type in the historical load history and the number of cycles corresponding to the load cycle type; the number of crack propagation cycles is calculated based on the stress level, critical crack length, initial crack length, and crack propagation parameters. According to the invention, the stress at different load levels is converted into the equivalent zero-tensile stress level, so that the influence on the material under the actual use condition can be comprehensively considered, and the accuracy of crack extension life prediction is improved.

Description

Crack propagation life determining method, device, equipment and storage medium

Technical Field

The invention relates to the technical field of fatigue life calculation, in particular to a crack propagation life determining method, a crack propagation life determining device, crack propagation life determining equipment and a storage medium.

Background

Crack propagation life refers to the number of load cycles or time that a crack-containing structure experiences from an initial crack propagation to a critical crack length under fatigue loading. Taking a gas turbine engine disk as an example, the gas turbine engine disk is an important component of a gas turbine engine for rotating a compressor and a turbine. It is typically made of a high temperature alloy material to withstand the high temperature and high speed operating environment. The design and manufacture of a gas turbine engine disk is critical to the performance and reliability of the gas turbine engine. Gas turbine engine disks are the most important key components in rotor components, and the presence of defects or cracks has a significant impact on the useful life of the disk, and once broken in service, can pose an extremely serious hazard.

Wheel disc cracks may refer to cracks that occur in a metal structure such as a rim or tire. The presence of a crack in the wheel disc may lead to serious structural damage and safety hazards, so it becomes very important to accurately evaluate the crack propagation life on the wheel disc. Currently, methods for estimating the crack growth life exist, but the crack growth life cannot be accurately estimated without considering the growth behavior of the crack under different loads.

Disclosure of Invention

In view of the above, the present invention provides a method and an apparatus for determining crack propagation life, so as to solve the problem of inaccurate crack life estimation in the prior art.

In a first aspect, the present invention provides a crack growth life determining method comprising:

acquiring the material size, the initial crack length and the crack propagation parameters of a structure to be analyzed;

acquiring a history load history of the structure to be analyzed in actual use, wherein the history load history is a process of changing variable amplitude load of the structure to be analyzed along with time;

calculating critical crack length of a crack part of the structure to be analyzed based on historical load history, material size;

calculating an equivalent stress level of the historical load history based on the load cycle type in the historical load history and the number of cycles corresponding to the load cycle type;

the number of crack propagation cycles is calculated based on the stress level, critical crack length, initial crack length, and crack propagation parameters.

In an alternative embodiment, calculating the critical crack length of the crack site of the structure to be analyzed based on the historical load history, the material dimensions, comprises:

obtaining fracture toughness of a structure to be analyzed obtained through experiments;

determining a maximum external load in the history of the load;

calculating the maximum nominal stress according to the material size and the maximum external load;

the following formula is combined to calculate the critical crack length:

wherein,is critical crack length%>Is fracture toughness, < >>For maximum nominal stress in history of load, +.>Is the width in the dimension of the material.

In an alternative embodiment, the equivalent stress level is calculated by the following formula:

wherein,is stress level, +.>Equivalent zero-tensile stress for once per cycle, +.>Indicate->Type of load cycle,/->For the total number of cycles of all load cycle types in the history of load, the +.>Is the crack growth rate index in the crack growth parameters.

In an alternative embodiment, the corresponding equivalent zero-tensile stress is calculated once per cycle by the following formula:

wherein,maximum nominal stress in the load cycle type corresponding to the current cycle, (-), for example>Is stress ratio, +.>Is the residual strength factor in the crack propagation parameters.

In an alternative embodiment, the maximum nominal stress is calculated by the following formula:

wherein,is the maximum external load->Is the thickness in the dimension of the material.

In an alternative embodiment, the crack growth cycle number is calculated by the following formula:

wherein,for crack propagation cycle number,/->For initial crack length, < >>Is a crack growth rate constant among the crack growth parameters.

In an alternative embodiment, the method further comprises:

and carrying out ratio operation on the crack expansion cycle times and the total cycle times, and calculating the failure cycle times of the load process.

In a second aspect, the present invention provides a crack growth life determining device, the device comprising:

the first acquisition module is used for acquiring the material size, the initial crack length and the crack expansion parameter of the structure to be analyzed;

the second acquisition module is used for acquiring the history load history of the structure to be analyzed in actual use, wherein the history load history is the process of changing the variable amplitude load of the structure to be analyzed along with time;

the critical crack length calculation module is used for calculating the critical crack length of the crack part of the structure to be analyzed based on the history load process and the material size;

the stress level calculation module is used for calculating the equivalent stress level of the historical load process based on the load cycle type in the historical load process and the cycle times corresponding to the load cycle type;

and the cycle number calculation module is used for calculating the cycle number of crack expansion based on the stress level, the critical crack length, the initial crack length and the crack expansion parameter.

Based on the history load history and the material size, calculating the critical crack length of the crack part of the structure to be analyzed, wherein the method comprises the following steps:

determining a maximum external load in the history of the load;

the following formula is combined to calculate the critical crack length:

In a third aspect, the present invention provides a computer device comprising: the crack growth life determining device comprises a memory and a processor, wherein the memory and the processor are in communication connection, the memory stores computer instructions, and the processor executes the computer instructions, so that the crack growth life determining method of the first aspect or any corresponding implementation mode of the first aspect is executed.

In a fourth aspect, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to perform the crack growth life determining method of the first aspect or any one of its corresponding embodiments.

According to the crack extension life determining method provided by the invention, the influence of the load on the crack extension life is fully considered, the influence on the material under the actual use condition can be comprehensively considered by converting the stress under different load levels into the equivalent zero-tensile stress level, the accuracy of crack extension life prediction is improved, and more reliable basis is provided for material selection and design.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

FIG. 1 is a flow chart of a crack growth life determination method according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of historical load history according to an embodiment of the invention;

FIG. 3 is a schematic diagram of exemplary calculations in accordance with an embodiment of the present invention;

FIG. 4 is a block diagram of a crack growth life determining device according to an embodiment of the present invention;

fig. 5 is a schematic diagram of a hardware structure of a computer device according to an embodiment of the present invention.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The gas turbine engine disk is the most important key component in its rotor components, and the most important mode of failure is low cycle fatigue damage, which can cause extremely serious damage once it is broken in service. Therefore, in design, the wheel disc is generally designed as a life limiting member. In the design, the influence of defects or cracks generated in material preparation, blank forming, manufacturing, assembly and transportation and use on the service life of the wheel disc is considered, fatigue crack growth analysis under typical working conditions is required to be carried out, and whether the crack growth life from initial defects to critical crack sizes meets the requirements of the design full life period or the maintenance period is judged.

In practical use, because the characteristic part of the wheel disc has initial defects or cracks, under the action of cyclic load, the initial defects or cracks of the characteristic part start to expand, so that the bearing capacity of the wheel disc is weakened, the residual strength of the wheel disc gradually decreases along with the growth of the cracks, when the crack length of the characteristic part of the wheel disc expands to a certain size (generally called critical crack size), and under the action of the maximum limiting load of the wheel disc, when the stress intensity factor of the front edge of the crack reaches the fracture toughness of a material, the cracks of the characteristic part can be instable and expanded, and the wheel disc is broken. Thus, the maximum limiting load condition of the wheel disc in use is the most important load factor that determines the allowable crack propagation length of the wheel disc feature. The allowable critical crack length is a determinant for determining crack propagation life under the conditions of a certain initial crack length and a certain material propagation rate. The common practice of the current engineering is to adopt a main cycle to analyze the crack propagation life of the wheel disc and also adopt a corresponding test to verify.

However, during use, the stress level of the disk or other disk, where an initial defect exists or where a crack is characterized, is constantly changing due to load uncertainty, and the crack propagation rate and length are changing in real time with the stress level at the crack tip. If the crack propagation life analysis is performed completely according to the main cycle, larger errors and unreliable prediction results are brought.

In view of the foregoing, there is provided in accordance with an embodiment of the invention a crack growth life determining method embodiment, it being noted that the steps illustrated in the flowchart of the figures may be performed in a computer system, such as a set of computer executable instructions, and that, although a logical sequence is illustrated in the flowchart, in some cases, the steps illustrated or described may be performed in a different order than that illustrated herein.

In this embodiment, a crack growth life determining method is provided, which may be executed by a server, a terminal, or the like, and fig. 1 is a flowchart of the crack growth life determining method according to an embodiment of the present invention, as shown in fig. 1, and the flowchart includes the steps of:

step S101, obtaining the material size, initial crack length and crack propagation parameters of the structure to be analyzed.

In this embodiment, the structure to be analyzed is exemplified by a center cracked flat plate made of AISI4340 steel, and the material dimensions include: plate thicknessThe width of the plate is->The length of the plate is 500mm; initial crack length +.>. According to experimental measurement, the AISI4340 steel has the yield strength of 1255MPa and the fracture toughness of +.>. Crack propagation parameters in Walker equation: />、/>、/>(R is more than or equal to 0). In this embodiment, the Walker equation may be used to predict the crack growth rate of the material in a specific stress state, and the crack growth rate of the material may be determined through experiments to obtain an empirical constant +.>、/>And->Is a value of (2).

The Walker equation is as follows:

wherein,for the current crack length->For the number of crack growth cycles, ">、/>、/>Is crack propagation parameter->Is stress intensity factor range->Is the maximum stress intensity factor->Is stress ratio, +.>Is equivalent to the stress intensity factor range under the zero-stretching condition, +.>Is the maximum nominal stress->Is the minimum nominal stress, F is a dimensionless function of the geometric feature and the relative crack length, +.>Is the circumference ratio.

Step S102, obtaining a history load history of the structure to be analyzed in actual use, wherein the history load history is a process of changing variable amplitude load of the structure to be analyzed along with time.

The historical load history may be shown in fig. 2, which is the historical load history of the structure to be analyzed selected in the present embodiment during actual use, where the abscissa is time and the ordinate is load. Referring to fig. 2, which includes four kinds of load cycle types, three sections divided by dotted lines correspond to the three kinds of load cycle types, respectively, and a black thick line portion in fig. 2 corresponds to a fourth middle load cycle type, which are different in load. In this embodiment, the actual complex cycle type and the corresponding cycle number can be converted into an equivalent stress level, so as to facilitate subsequent calculation.

In the embodiment, the actual load process can be approximately processed into a repetition of a loading sequence with a limited length, so that the crack extension life can be accurately estimated conveniently, a basis is provided for the establishment of a load spectrum of a subsequent crack extension test, and test verification is convenient.

Step S103, calculating the critical crack length of the crack part of the structure to be analyzed based on the history load process and the material size.

In some optional embodiments, step S103, which calculates the critical crack length of the crack portion of the structure to be analyzed based on the history of the load and the material size, includes:

obtaining fracture toughness of the structure to be analyzed obtained through experiments；

Determining maximum external load in historic load history；

Calculating the maximum nominal stress according to the material size and the maximum external load；

The following formula is combined to calculate the critical crack length:

In some alternative embodiments, the maximum nominal stress is calculated by the following formula:

The maximum external load here isThe maximum external load in the history of the historical load can be calculated, or the maximum external load in each load cycle type can be calculated, namely, a formula for calculating the maximum nominal stress can be calculated, or the historical load can be calculatedThe maximum nominal stress in the history may also be calculated in the load cycle type corresponding to the current cycle.

Taking the center crack plate of AISI4340 steel as an example, the calculated critical crack length is 15.8mm, and the geometric shape coefficient F is 1.11.

Step S104, calculating the equivalent stress level of the historical load history based on the load cycle type and the cycle times corresponding to the load cycle type in the historical load history.

In this embodiment, for a given history load history in actual use, a rain flow counting method may be adopted to obtain a corresponding load cycle type and a cycle number corresponding to the load cycle type.

Specifically, as shown in fig. 2, a rain flow counting method is used to process a given historical load history. The parameters corresponding to the four load cycle types are as follows:

cycle type one: number of cycles，/>，/>；

Cycle type two: number of cycles，/>，/>；

Cycle type three: number of cycles，/>，/>；

Cycle type four: number of cycles，/>，/>。

The specific results are shown with reference to fig. 3, wherein,is of the circulation type->The number of cycles corresponding to the current cycle type, < >>，/>，/>、/>Is->And->Is a product of (a) and (b).

Since the different cycle types are all translated into equivalent zero-tensile stress, i.e. r=0, the Walker equation is deformed as follows:

in some alternative embodiments, the equivalent stress level is calculated by the following formula:

wherein,is stress level, +.>Equivalent zero-tensile stress for once per cycle, +.>，/>Indicate->Type of load cycle,/->For the total number of cycles of all load cycle types in the history of load, the +.>Is the crack growth rate index in the crack growth parameters.

In some alternative embodiments, the corresponding equivalent zero-tensile stress is calculated once per cycle by the following formula:

wherein,maximum nominal stress in the load cycle type corresponding to the current cycle, (-), for example>Stress ratio of minimum nominal stress to maximum nominal stress, +.>Is the residual strength factor in the crack propagation parameters. It should be noted that the number of cycles corresponding to each load type is at least once, so +.>And the maximum nominal stress corresponding to the load cycle type of the current cycle number is shown.

The specific reasoning process is as follows:

define the total cycle number in the actual load course asThen->Sub-cycling;

due to any circulationN=1) is:

wherein,the crack length after each cycle is given.

The crack length increment for a given history of actual use load history is:

the average crack propagation rate for a given history of actual use load history is:

wherein,the equivalent stress intensity factor range in the history load process of actual use;

since K and S are in direct proportion, then:

for the load in actual use, there is the following equation:

where k is a variable, and its maximum value is the total number of cycles in the history of the load.

Calculating equivalent zero-tensile stress levels in history of actual useThe method comprises the following steps:

in this example, taking the above-mentioned material as AISI4340 steel and a center crack plate as an example, the obtained stress level was calculated311.3MPa.

Step S105, calculating the number of crack growth cycles based on the stress level, the critical crack length, the initial crack length, and the crack growth parameter.

In some alternative embodiments, the crack growth cycle number is calculated by the following formula:

wherein,for crack propagation cycle number,/->For the initial crack length, k is a variable, the maximum is the total number of load cycle types, +.>Is a crack growth rate constant among the crack growth parameters.

In this example, taking the center crack plate of AISI4340 steel as an example, the number of crack growth cycles obtained was calculatedIs->。

In some alternative embodiments, the method further comprises: and carrying out ratio operation on the crack expansion cycle times and the total cycle times, and calculating the failure cycle times of the load process.

That is, the number of failure cycles of the load history can be calculatedThe method comprises the following steps: />。

In this embodiment, taking the center crack plate of AISI4340 steel as an example, the number of failure cycles obtained is calculated1477 repetitions. I.e. over 1477 given load courses, the beltThe flat plate with the central crack can fail and break.

In the embodiment, the influence of the load on the crack extension life is fully considered, and according to the corresponding cycle times of the main cycle (0-max-0), the sub-cycle (sub-max-sub-maximum), the sub-cycle and the like, the influence on the material under the actual use condition can be comprehensively considered by converting the stress under different load levels into the equivalent zero-tensile stress level, the accuracy of the crack extension life prediction is improved, and more reliable basis is provided for material selection and design.

In this embodiment, a crack growth life determining device is further provided, and the crack growth life determining device is used to implement the foregoing embodiments and preferred embodiments, and is not described in detail. As used below, the term "module" may be a combination of software and/or hardware that implements a predetermined function. While the means described in the following embodiments are preferably implemented in software, implementation in hardware, or a combination of software and hardware, is also possible and contemplated.

The present embodiment provides a crack growth life determining device, as shown in fig. 4, the device including:

a first obtaining module 301, configured to obtain a material size, an initial crack length, and a crack propagation parameter of a structure to be analyzed;

the second obtaining module 302 is configured to obtain a history load history of the structure to be analyzed in actual use, where the history load history is a process that a variable amplitude load of the structure to be analyzed changes with time;

the critical crack length calculation module 303 is configured to calculate a critical crack length of a crack portion of the structure to be analyzed based on the history load history and the material size;

a stress level calculation module 304, configured to calculate an equivalent stress level of the historical load history based on the load cycle type in the historical load history and the number of cycles corresponding to the load cycle type;

the cycle number calculation module 305 is configured to calculate the number of crack propagation cycles based on the stress level, the critical crack length, the initial crack length, and the crack propagation parameter.

determining a maximum external load in the history of the load;

the following formula is combined to calculate the critical crack length:

The crack growth life determining means in this embodiment is presented in the form of functional units, here means ASIC circuits, processors and memories executing one or more software or fixed programs, and/or other devices that can provide the above described functionality.

Further functional descriptions of the above respective modules and units are the same as those of the above corresponding embodiments, and are not repeated here.

The embodiment of the invention also provides computer equipment, which is provided with the crack growth life determining device shown in the figure 4.

Referring to fig. 5, fig. 5 is a schematic structural diagram of a computer device according to an alternative embodiment of the present invention, as shown in fig. 5, the computer device includes: one or more processors 10, memory 20, and interfaces for connecting the various components, including high-speed interfaces and low-speed interfaces. The various components are communicatively coupled to each other using different buses and may be mounted on a common motherboard or in other manners as desired. The processor may process instructions executing within the computer device, including instructions stored in or on memory to display graphical information of the GUI on an external input/output device, such as a display device coupled to the interface. In some alternative embodiments, multiple processors and/or multiple buses may be used, if desired, along with multiple memories and multiple memories. Also, multiple computer devices may be connected, each providing a portion of the necessary operations (e.g., as a server array, a set of blade servers, or a multiprocessor system). One processor 10 is illustrated in fig. 5.

The processor 10 may be a central processor, a network processor, or a combination thereof. The processor 10 may further include a hardware chip, among others. The hardware chip may be an application specific integrated circuit, a programmable logic device, or a combination thereof. The programmable logic device may be a complex programmable logic device, a field programmable gate array, a general-purpose array logic, or any combination thereof.

Wherein the memory 20 stores instructions executable by the at least one processor 10 to cause the at least one processor 10 to perform the methods shown in implementing the above embodiments.

The memory 20 may include a storage program area that may store an operating system, at least one application program required for functions, and a storage data area; the storage data area may store data created from the use of the computer device of the presentation of a sort of applet landing page, and the like. In addition, the memory 20 may include high-speed random access memory, and may also include non-transitory memory, such as at least one magnetic disk storage device, flash memory device, or other non-transitory solid-state storage device. In some alternative embodiments, memory 20 may optionally include memory located remotely from processor 10, which may be connected to the computer device via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.

Memory 20 may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as flash memory, hard disk, or solid state disk; the memory 20 may also comprise a combination of the above types of memories.

The computer device also includes a communication interface 30 for the computer device to communicate with other devices or communication networks.

The embodiments of the present invention also provide a computer readable storage medium, and the method according to the embodiments of the present invention described above may be implemented in hardware, firmware, or as a computer code which may be recorded on a storage medium, or as original stored in a remote storage medium or a non-transitory machine readable storage medium downloaded through a network and to be stored in a local storage medium, so that the method described herein may be stored on such software process on a storage medium using a general purpose computer, a special purpose processor, or programmable or special purpose hardware. The storage medium can be a magnetic disk, an optical disk, a read-only memory, a random access memory, a flash memory, a hard disk, a solid state disk or the like; further, the storage medium may also comprise a combination of memories of the kind described above. It will be appreciated that a computer, processor, microprocessor controller or programmable hardware includes a storage element that can store or receive software or computer code that, when accessed and executed by the computer, processor or hardware, implements the methods illustrated by the above embodiments.

Although embodiments of the present invention have been described in connection with the accompanying drawings, various modifications and variations may be made by those skilled in the art without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope of the invention as defined by the appended claims.

Claims

1. A crack growth life determining method, the method comprising:

calculating critical crack length of the crack part of the structure to be analyzed based on the historical load history and the material size;

calculating an equivalent stress level of the historical load history based on a load cycle type in the historical load history and a number of cycles corresponding to the load cycle type;

calculating crack propagation cycle times based on the stress level, the critical crack length, the initial crack length, the crack propagation parameter;

the calculating the critical crack length of the crack part of the structure to be analyzed based on the historical load history and the material size comprises the following steps:

obtaining fracture toughness of the structure to be analyzed obtained through experiments;

determining a maximum external load in the history of the historical load;

calculating a maximum nominal stress based on the material dimensions and the maximum external load;

the critical crack length is calculated in combination with the following formula:

wherein,for the critical crack length,/->For the fracture toughness,/->For said maximum nominal stress in said history of historical loads,/o>Is the width in the dimension of the material.

2. The method of claim 1, wherein the equivalent stress level is calculated by the formula:

wherein,for the stress level,/->Equivalent zero-tensile stress for once per cycle, +.>Indicate->The carrier is plantedCharge cycle type,/->For the total number of cycles of all said load cycle types in said history, +.>Is the crack growth rate index in the crack growth parameters.

3. The method according to claim 2, characterized in that the corresponding equivalent zero-tensile stress is calculated once per cycle by the following formula:

wherein,for the maximum nominal stress in the load cycle type corresponding to the current cycle, ++>Is a stress ratio,Is a residual strength factor in the crack growth parameters.

4. A method according to claim 3, characterized in that the maximum nominal stress is calculated by the following formula:

wherein,for said maximum external load,/->Is the thickness in the dimension of the material.

5. A method according to claim 3, wherein the crack growth cycle number is calculated by the formula:

wherein,for the number of crack growth cycles,/->For the initial crack length,/->Is a crack growth rate constant among the crack growth parameters.

6. The method as recited in claim 2, further comprising:

7. A crack growth life determining device, the device comprising:

the critical crack length calculation module is used for calculating the critical crack length of the crack part of the structure to be analyzed based on the historical load history and the material size;

the cycle number calculation module is used for calculating the cycle number of crack expansion based on the stress level, the critical crack length, the initial crack length and the crack expansion parameter;

determining a maximum external load in the history of the historical load;

8. A computer device, comprising:

a memory and a processor in communication with each other, the memory having stored therein computer instructions, the processor executing the computer instructions to perform the crack growth life determining method of any of claims 1-6.

9. A computer-readable storage medium storing computer instructions for causing the computer to perform the crack growth life determining method of any one of claims 1-6.