Method for predicting multi-shaft high-low cycle composite fatigue life of multi-duct casing system

Abstract

The invention discloses a multi-duct casing system multi-shaft high-low-cycle composite fatigue life prediction method, and relates to the technical field of multi-duct casing system multi-shaft high-low-cycle composite fatigue life prediction, and the method comprises the steps: determining a multi-shaft low-cycle load stress state borne by a casing key examination part; performing dynamic analysis on the cartridge receiver to obtain multi-axis high-cycle load stress information; constructing a multi-axis high-low-cycle combined load spectrum at a cartridge receiver examination part; modeling and classifying the multi-axis high-low cycle compound fatigue damage; constructing a multi-axis high-low cycle fatigue coupling damage item based on the multi-axis fatigue damage parameter; the equivalent fatigue damage amount corresponding to each load block is obtained through calculation; and establishing a multi-axis high-low cycle composite fatigue life prediction model, and outputting a fatigue life prediction result of the multi-duct casing system. According to the method, the multi-axis high-low cycle composite fatigue load spectrum is decomposed, a coupling damage item for measuring the severity of the multi-axis high-low cycle fatigue interaction is provided, and the fatigue life prediction precision is improved.

Description

Technical Field

[0001] This invention relates to the field of multi-axis high- and low-cycle combined fatigue life prediction technology for multi-duct casing systems, and in particular to a method for predicting multi-axis high- and low-cycle combined fatigue life of multi-duct casing systems. Background Technology

[0002] Some engineering components of aero-engines, such as engine shafts and casings, are subjected to multiaxial loads during service, which can lead to engine failure due to multiaxial fatigue. Engine casings, in particular, are subjected to typical multiaxial high- and low-cycle combined fatigue loads, and their fatigue failure mechanisms are complex. Currently, research on multiaxial high- and low-cycle combined fatigue is limited, making it difficult to predict the fatigue life of casings. Existing life prediction methods suffer from poor accuracy and unsatisfactory prediction results when predicting the life under multiaxial high- and low-cycle combined fatigue loads.

[0003] Therefore, it is necessary to design a new method for predicting the multi-axis high- and low-cycle combined fatigue life of multi-duct casing systems to solve the above problems. Summary of the Invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the problem to be solved by the present invention is to address the difficulty of existing life prediction methods in simultaneously considering the combined effects of multiaxial low-cycle loads and multiaxial high-cycle vibration loads, thereby achieving reliable prediction of fatigue life.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] In a first aspect, embodiments of the present invention provide a method for predicting the multiaxial high- and low-cycle composite fatigue life of a multi-duct casing system, comprising: acquiring the structural model and load condition information of the multi-duct casing system under service conditions, and performing strength analysis on the casing based on the structural model to determine the multiaxial low-cycle load stress state borne by the key test parts of the casing.

[0008] Using the aforementioned multiaxial low-cycle load stress state as a prestressing condition, dynamic analysis of the casing is performed to obtain multiaxial high-cycle load stress information;

[0009] Based on the multiaxial low-cycle load stress and multiaxial high-cycle load stress, a multiaxial high-low cycle composite load spectrum is constructed at the test site of the casing.

[0010] For the multiaxial high-low cycle composite load spectrum, the multiaxial high-low cycle composite fatigue damage is modeled and classified;

[0011] Construct a multiaxial high- and low-cycle fatigue coupled damage term based on multiaxial fatigue damage parameters;

[0012] Using the load block as the basic analysis unit, the equivalent fatigue damage corresponding to each load block is calculated.

[0013] Accumulate multiaxial high- and low-cycle combined fatigue damage, establish a multiaxial high- and low-cycle combined fatigue life prediction model, and output the fatigue life prediction results of the multi-duct casing system.

[0014] As a preferred embodiment of the multiaxial high- and low-cycle composite fatigue life prediction method for a multi-duct casing system described in this invention, the method includes: performing strength analysis on the casing based on a structural model to determine the multiaxial low-cycle load stress state borne by key test components of the casing, including:

[0015] Static strength analysis of the casing was performed to obtain the spatial distribution of equivalent stress, equivalent strain, normal stress and maximum shear stress of the casing under low cycle load.

[0016] The key test parts of the casing are identified from the analysis results, and the stress states corresponding to the key test parts are extracted. The stress states include the maximum equivalent stress, the maximum equivalent strain, the maximum shear stress, and the maximum normal stress in the X direction. The stress states are used as the stress input for multi-axis low-cycle loads.

[0017] As a preferred embodiment of the multi-axial high- and low-cycle composite fatigue life prediction method for a multi-duct casing system described in this invention, the method involves: using the multi-axial low-cycle load stress state as a prestressing condition, performing dynamic analysis on the casing to obtain multi-axial high-cycle load stress information, including:

[0018] Modal analysis of the casing under prestressed conditions was performed to obtain the natural frequencies and mode shapes of the casing under low-cycle load conditions.

[0019] Based on the modal analysis results, the excitation frequency range and excitation form covering the resonant frequency range of the casing are determined;

[0020] Under the prestressed condition, the excitation is applied to the casing, and harmonic response analysis is performed on the casing to obtain the axial stress amplitude and shear stress amplitude of the key test parts of the casing under the excitation. The axial stress amplitude and shear stress amplitude are then used as multiaxial high-cycle load stress information.

[0021] As a preferred embodiment of the multi-axis high-low cycle composite fatigue life prediction method for a multi-duct casing system according to the present invention, the method includes: constructing a multi-axis high-low cycle composite load spectrum at the casing testing location, including:

[0022] At the critical test points of the casing, multi-axis low-cycle load stress and multi-axis high-cycle load stress are superimposed to form a composite load that simultaneously includes multi-axis low-cycle load and multi-axis high-cycle load.

[0023] Using a characteristic low-cycle load event and its corresponding complete high-cycle vibration process as the basic analysis unit, a multiaxial high- and low-cycle composite fatigue load block is constructed.

[0024] Based on the load block, the number of high-cycle cycles n within the load block is determined according to the number of high-cycle vibrations experienced within a typical task profile time corresponding to a low-cycle load cycle.

[0025] One or more load blocks are arranged in the order of the actual service mission time of the casing to form a multi-axis high-low cycle composite load spectrum characterizing the actual working conditions of the casing.

[0026] As a preferred embodiment of the multiaxial high- and low-cycle combined fatigue life prediction method for a multi-duct casing system described in this invention, the method includes: modeling and classifying multiaxial high- and low-cycle combined fatigue damage, including:

[0027] The multiaxial high- and low-cycle combined fatigue damage is divided into multiaxial low-cycle fatigue damage, multiaxial high-cycle fatigue damage and multiaxial high- and low-cycle combined fatigue coupled damage.

[0028] Among them, the determination of multiaxial low-cycle fatigue damage is based on the plastic strain amplitude generated during load cycling;

[0029] The determination of multiaxial high-cycle fatigue damage is based on the superimposed multiaxial high-cycle vibration stress amplitude under the static average stress formed by low-cycle load.

[0030] The multiaxial high- and low-cycle combined fatigue coupled damage is used to characterize the influence of material state changes caused by low-cycle loading on the evolution of high-cycle fatigue damage.

[0031] As a preferred embodiment of the multi-axis high- and low-cycle combined fatigue life prediction method for a multi-duct casing system according to the present invention, the method for constructing a multi-axis high- and low-cycle fatigue coupled damage term based on multi-axis fatigue damage parameters includes: using multi-axis low-cycle fatigue damage parameters and multi-axis high-cycle fatigue damage parameters as variables to construct a multi-axis high- and low-cycle combined fatigue coupled damage term, which is used to characterize the interaction and mutual amplification effect between multi-axis low-cycle fatigue damage and multi-axis high-cycle fatigue damage.

[0032] The coupled damage term includes: a factor characterizing the effect of high-cycle normal stress on the multiaxial high-low cycle combined fatigue life; a factor characterizing the effect of high-cycle shear stress on the multiaxial high-low cycle combined fatigue life; and a factor considering the nonlinear deviation effect of low-cycle cycling on high-cycle fatigue life.

[0033] As a preferred embodiment of the multi-axis high- and low-cycle composite fatigue life prediction method for a multi-duct casing system described in this invention, the method involves: using load blocks as the basic analysis unit to calculate the equivalent fatigue damage corresponding to each load block, including:

[0034] The multi-axis high- and low-cycle composite load spectrum is divided into multiple load blocks, each of which contains characteristic low-cycle load events and the complete high-cycle vibration process it carries.

[0035] Based on the terms of multiaxial low-cycle fatigue damage, multiaxial high-cycle fatigue damage, and multiaxial high- and low-cycle combined fatigue coupled damage, the equivalent low-cycle fatigue damage, equivalent high-cycle fatigue damage, and equivalent coupled damage corresponding to each load block are calculated.

[0036] The equivalent fatigue damage of each load block is obtained by accumulating the equivalent low-cycle fatigue damage, equivalent high-cycle fatigue damage, and equivalent coupling damage.

[0037] As a preferred embodiment of the multi-axis high-low cycle combined fatigue life prediction method for a multi-duct casing system according to the present invention, the method includes: accumulating multi-axis high-low cycle combined fatigue damage, establishing a multi-axis high-low cycle combined fatigue life prediction model, and outputting the fatigue life prediction results of the multi-duct casing system, including:

[0038] Based on the equivalent fatigue damage corresponding to each load block, the multi-axis low-cycle fatigue damage, multi-axis high-cycle fatigue damage, and multi-axis high-low cycle combined fatigue coupled damage are cumulatively calculated according to the order of appearance and repetition of the load blocks in the load spectrum of the entire life of the casing.

[0039] When the accumulated multi-axis high-low cycle composite fatigue damage reaches the preset failure criterion, fatigue failure is determined to have occurred at the test part of the casing, and the corresponding number of loads or equivalent service time is taken as the fatigue life of the casing.

[0040] Based on the aforementioned accumulation process and failure determination results, a multi-axis high-low cycle composite fatigue life prediction model Ncode is established.

[0041] In Ncode, a fatigue analysis module is built. The load spectrum is input to calculate the multiaxial low-cycle fatigue life, the multiaxial high-cycle fatigue life under low-cycle stress, and the high-low cycle load cycle ratio n in the fatigue load block. The results are then substituted into the multiaxial high-low cycle composite fatigue damage model to calculate the multiaxial high-cycle stress level multiaxial high-low cycle composite fatigue load block life.

[0042] In a second aspect, embodiments of the present invention provide a computer device, including a memory and a processor, wherein the memory stores a computer program, wherein: when the computer program instructions are executed by the processor, they implement the steps of a multi-axis high- and low-cycle composite fatigue life prediction method for a multi-duct casing system as described in the first aspect of the present invention.

[0043] Thirdly, embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program instructions are executed by a processor, they implement the steps of a multi-axis high- and low-cycle composite fatigue life prediction method for a multi-duct casing system as described in the first aspect of the present invention.

[0044] The beneficial effects of this invention are as follows: This invention addresses the problem of predicting the combined fatigue life of multiaxial high- and low-cycle loads by incorporating the coupled damage of multiaxial high- and low-cycle loads and decomposing the multiaxial high- and low-cycle combined fatigue load spectrum. Based on the DP damage parameter, a coupled damage term is proposed to measure the intensity of the interaction between multiaxial high- and low-cycle fatigue, which improves the accuracy of fatigue life prediction and simplifies the process of determining model parameters, making it more suitable for solving specific engineering problems. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a flowchart of the prestressed modal analysis of the present invention; Figure 3 These are the mode shapes of the high-pressure compressor casing of the present invention. Figure 4 This is a flowchart of the harmonic response analysis of the present invention; Figure 5 This is a diagram showing the application of pressure excitation according to the present invention; Figure 6 This invention provides a stress-strain amplitude response diagram for a high-pressure compressor casing. Figure 7 This is a schematic diagram of the multiaxial high-low cycle composite fatigue load spectrum of the present invention; Figure 8 This is the life distribution diagram of the Ncode multi-axis pure low-cycle fatigue simulation of the present invention; Figure 9 This is a schematic diagram of the multiaxial high-cycle load spectrum under low-cycle stress according to the present invention; Figure 10 This is a schematic diagram of the fatigue life dispersion bands under two multiaxial high-cycle stress levels and different phase differences according to the present invention. Figure 6 In the middle: a) Axial stress amplitude response curve; b) Shear stress amplitude response curve; c) Axial strain amplitude response curve; d) Shear strain amplitude response curve. Detailed Implementation

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0048] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0049] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0050] Example 1

[0051] Reference Figures 1-10 This is the first embodiment of the present invention, which provides a method for predicting the multi-axis high- and low-cycle combined fatigue life of a multi-duct casing system, including:

[0052] S1: Obtain the structural model and load condition information of the multi-duct casing system under service conditions, and perform strength analysis on the casing based on the structural model to determine the multiaxial low-cycle load stress state of the key test parts of the casing.

[0053] Furthermore, a static strength analysis was performed on the casing to obtain the spatial distribution of the equivalent stress, equivalent strain, normal stress, and maximum shear stress of the casing under low-cycle load.

[0054] The key test parts of the casing are identified from the analysis results, and the stress states corresponding to the key test parts are extracted. The stress states include the maximum equivalent stress, the maximum equivalent strain, the maximum shear stress, and the maximum normal stress in the X direction. The stress states are used as the stress input for multi-axis low-cycle loads.

[0055] S2: Using the multi-axis low-cycle load stress state as the prestressing condition, perform dynamic analysis on the casing to obtain multi-axis high-cycle load stress information.

[0056] Furthermore, modal analysis was performed on the casing under prestressed conditions to obtain the natural frequencies and mode shapes of the casing under low-cycle load conditions;

[0057] Based on the modal analysis results, the excitation frequency range and excitation form covering the resonant frequency range of the casing are determined;

[0058] Under the prestressed condition, the excitation is applied to the casing, and harmonic response analysis is performed on the casing to obtain the axial stress amplitude and shear stress amplitude of the key test parts of the casing under the excitation. The axial stress amplitude and shear stress amplitude are then used as multiaxial high-cycle load stress information.

[0059] S3: Based on the multi-axis low-cycle load stress and multi-axis high-cycle load stress, construct a multi-axis high-low cycle composite load spectrum at the test location of the casing.

[0060] Furthermore, at the key test parts of the casing, the multi-axis low-cycle load stress and the multi-axis high-cycle load stress are superimposed to form a composite load that simultaneously includes multi-axis low-cycle load and multi-axis high-cycle load.

[0061] Using a characteristic low-cycle load event and its corresponding complete high-cycle vibration process as the basic analysis unit, a multiaxial high- and low-cycle composite fatigue load block is constructed.

[0062] Based on the load block, the number of high-cycle cycles n within the load block is determined according to the number of high-cycle vibrations experienced within a typical task profile time corresponding to a low-cycle load cycle.

[0063] One or more load blocks are arranged in the order of the actual service mission time of the casing to form a multi-axis high-low cycle composite load spectrum characterizing the actual working conditions of the casing.

[0064] S4: For the multiaxial high-low cycle composite load spectrum, model and classify the multiaxial high-low cycle composite fatigue damage.

[0065] Furthermore, the multiaxial high- and low-cycle combined fatigue damage is divided into multiaxial low-cycle fatigue damage, multiaxial high-cycle fatigue damage, and multiaxial high- and low-cycle combined fatigue coupled damage.

[0066] Among them, the determination of multiaxial low-cycle fatigue damage is based on the plastic strain amplitude generated during load cycling;

[0067] The determination of multiaxial high-cycle fatigue damage is based on the superimposed multiaxial high-cycle vibration stress amplitude under the static average stress formed by low-cycle load.

[0068] The multiaxial high- and low-cycle combined fatigue coupled damage is used to characterize the influence of material state changes caused by low-cycle loading on the evolution of high-cycle fatigue damage.

[0069] S5: Construct a multiaxial high- and low-cycle fatigue coupled damage term based on multiaxial fatigue damage parameters.

[0070] Furthermore, using multiaxial low-cycle fatigue damage parameters and multiaxial high-cycle fatigue damage parameters as variables, a multiaxial high- and low-cycle composite fatigue coupled damage term is constructed to characterize the interaction and mutual amplification effect between multiaxial low-cycle fatigue damage and multiaxial high-cycle fatigue damage.

[0071] The coupled damage term includes: a factor characterizing the effect of high-cycle normal stress on the multiaxial high-low cycle combined fatigue life; a factor characterizing the effect of high-cycle shear stress on the multiaxial high-low cycle combined fatigue life; and a factor considering the nonlinear deviation effect of low-cycle cycling on high-cycle fatigue life.

[0072] S6: Using the load block as the basic analysis unit, calculate the equivalent fatigue damage corresponding to each load block.

[0073] Furthermore, the multi-axis high- and low-cycle composite load spectrum is divided into multiple load blocks, each of which contains characteristic low-cycle load events and the complete high-cycle vibration process they bear.

[0074] Based on the terms of multiaxial low-cycle fatigue damage, multiaxial high-cycle fatigue damage, and multiaxial high- and low-cycle combined fatigue coupled damage, the equivalent low-cycle fatigue damage, equivalent high-cycle fatigue damage, and equivalent coupled damage corresponding to each load block are calculated.

[0075] The equivalent fatigue damage of each load block is obtained by accumulating the equivalent low-cycle fatigue damage, equivalent high-cycle fatigue damage, and equivalent coupling damage.

[0076] S7: Accumulate multiaxial high- and low-cycle combined fatigue damage, establish a multiaxial high- and low-cycle combined fatigue life prediction model, and output the fatigue life prediction results of the multi-duct casing system.

[0077] Furthermore, based on the equivalent fatigue damage corresponding to each load block, the multiaxial low-cycle fatigue damage, multiaxial high-cycle fatigue damage, and multiaxial high-low cycle combined fatigue coupled damage are cumulatively calculated according to the order of appearance and repetition of the load blocks in the full life load spectrum of the casing.

[0078] When the accumulated multi-axis high-low cycle composite fatigue damage reaches the preset failure criterion, fatigue failure is determined to have occurred at the test part of the casing, and the corresponding number of loads or equivalent service time is taken as the fatigue life of the casing.

[0079] Based on the aforementioned accumulation process and failure determination results, a multi-axis high-low cycle composite fatigue life prediction model Ncode is established.

[0080] In Ncode, a fatigue analysis module is built. The load spectrum is input to calculate the multiaxial low-cycle fatigue life, the multiaxial high-cycle fatigue life under low-cycle stress, and the high-low cycle load cycle ratio n in the fatigue load block. The results are then substituted into the multiaxial high-low cycle composite fatigue damage model to calculate the multiaxial high-cycle stress level multiaxial high-low cycle composite fatigue load block life.

[0081] For example, this embodiment describes a method for predicting the multiaxial high- and low-cycle combined fatigue life of a multi-duct casing system. Taking the high-pressure compressor casing of a certain type of engine as an example, the method derived in this study will be explained step by step to predict its multiaxial high- and low-cycle combined fatigue life. The steps include the following:

[0082] Step 1: Determine the geometry, dimensions, and materials of the casing to be analyzed, as well as the constraints and loads it is subject to, and import this information into the finite element analysis software.

[0083] Step 2 involves performing a static strength analysis on the model. This analysis yields the equivalent stress, equivalent strain, normal stress, and maximum shear stress magnitude and distribution of the high-pressure compressor casing. From this analysis, the values ​​and locations of the maximum equivalent stress, maximum equivalent strain, maximum shear stress, and maximum normal stress in the X-direction are determined. This stress is then used as the low-cycle load stress on the high-pressure compressor casing, and this location will be the evaluation site in subsequent steps.

[0084] Step 3: Input the stress obtained from the static strength analysis into the prestress modal analysis module to perform modal analysis under prestress. First, obtain the natural frequencies of each order through modal analysis. Then, determine the frequency and form of the excitation force to ensure coverage of the resonant frequency range. Typically, the excitation force can be in the form of a triangular wave or a sine wave.

[0085] Step 4, as follows Figure 3 As shown, the stress obtained from the static strength analysis is used as the prestress input to the harmonic response analysis module for harmonic response analysis. The excitation frequency band should cover the natural frequency range obtained in step 3. A pressure excitation perpendicular to the wall surface is applied to the high-pressure compressor casing. The pressure distribution curve fitted by the inlet and outlet pressure data at the design point is used to obtain the axial stress amplitude and shear stress amplitude of the test part. This stress is used as a reference for high-cycle load.

[0086] Step 5, as follows Figures 4-7 As shown, multiaxial high-cycle stress is superimposed on the multiaxial low-cycle stress at the test part of the high-pressure compressor casing, and a suitable number of high-cycle cycles n is selected to obtain the load spectrum. The multiaxial high-cycle stress is obtained by appropriately amplifying the maximum stress amplitude in the harmonic response analysis.

[0087] Step 6, as follows Figure 8As shown, a fatigue analysis module was built in the Ncode fatigue analysis software. The load spectrum was input to calculate the multiaxial low-cycle fatigue life, the multiaxial high-cycle fatigue life under low-cycle stress, and the high-low cycle load cycle ratio n in the fatigue load block. These values ​​were then substituted into the multiaxial high-low cycle composite fatigue damage model to calculate the multiaxial high-cycle stress level multiaxial high-low cycle composite fatigue load block life. The formula for the multiaxial high-low cycle composite fatigue damage model is as follows:

[0088] ;

[0089] ;

[0090] In the formula, a and b are material constants that are only related to temperature; n is the high-cycle and low-cycle load ratio; To indicate low-cycle fatigue life; To indicate high-cycle fatigue life; This represents the low-cycle load stress amplitude. This represents the stress amplitude under high-cycle loads. The lifespan of the multi-axis high-low cycle composite fatigue load block.

[0091] Step 7, as follows Figures 9-10 As shown, the high-cycle fatigue load cell life is required when calculating the combined high- and low-cycle fatigue life of a multi-axis system. To ensure consistency between the high-cycle and low-cycle fatigue life calculated by the fatigue software and the new model, the multiaxial high-cycle fatigue life under low-cycle stress maintenance was also calculated using the fatigue life predicted by the Ncode fatigue simulation software, thus obtaining the multiaxial high-cycle and low-cycle composite fatigue life. The formula for multiaxial high- and low-cycle combined fatigue life is as follows:

[0092]

[0093] In the formula, Multiaxial high- and low-cycle composite fatigue life; Multiaxial low-cycle fatigue life; For multi-axis high-cycle fatigue life; These are the multiaxial high-cycle fatigue damage parameters; This represents the equivalent normal stress amplitude during high-cycle fatigue. The equivalent shear stress amplitude for high-cycle fatigue; lg(N) HCF ) is a commonly used logarithmic value for multiaxial high-cycle fatigue life; lg(N) LCF () is a commonly used logarithmic value for multiaxial low-cycle fatigue life.

[0094] This embodiment also provides a computer device applicable to a method for predicting the multi-axis high- and low-cycle composite fatigue life of a multi-duct casing system, including a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to realize the method for predicting the multi-axis high- and low-cycle composite fatigue life of a multi-duct casing system as proposed in the above embodiment.

[0095] The computer device can be a terminal, comprising a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0096] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements a multi-axis high- and low-cycle composite fatigue life prediction method for a multi-duct casing system as proposed in the above embodiment.

[0097] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for predicting the multi-axis high- and low-cycle combined fatigue life of a multi-duct casing system, characterized in that, include: Obtain the structural model and load condition information of the multi-duct casing system under service conditions, and perform strength analysis on the casing based on the structural model to determine the multiaxial low-cycle load stress state of the key test parts of the casing. Using the aforementioned multiaxial low-cycle load stress state as a prestressing condition, dynamic analysis of the casing is performed to obtain multiaxial high-cycle load stress information; Based on the multiaxial low-cycle load stress and multiaxial high-cycle load stress, a multiaxial high-low cycle composite load spectrum is constructed at the test site of the casing. For the multiaxial high-low cycle composite load spectrum, the multiaxial high-low cycle composite fatigue damage is modeled and classified; Construct a multiaxial high- and low-cycle fatigue coupled damage term based on multiaxial fatigue damage parameters; Using the load block as the basic analysis unit, the equivalent fatigue damage corresponding to each load block is calculated. Accumulate multiaxial high- and low-cycle combined fatigue damage, establish a multiaxial high- and low-cycle combined fatigue life prediction model, and output the fatigue life prediction results of the multi-duct casing system.

2. The method for predicting the multi-axis high- and low-cycle composite fatigue life of a multi-duct casing system as described in claim 1, characterized in that, The strength analysis of the casing based on the structural model determines the multiaxial low-cycle load stress state of the key test parts of the casing, including: Static strength analysis of the casing was performed to obtain the spatial distribution of equivalent stress, equivalent strain, normal stress and maximum shear stress of the casing under low cycle load. The key test parts of the casing are identified from the analysis results, and the stress states corresponding to the key test parts are extracted. The stress states include the maximum equivalent stress, the maximum equivalent strain, the maximum shear stress, and the maximum normal stress in the X direction. The stress states are used as the stress input for multi-axis low-cycle loads.

3. The method for predicting the multi-axis high- and low-cycle composite fatigue life of a multi-duct casing system as described in claim 1, characterized in that, The method of using multiaxial low-cycle load stress state as prestressing condition to perform dynamic analysis on the casing and obtain multiaxial high-cycle load stress information includes: Modal analysis of the casing under prestressed conditions was performed to obtain the natural frequencies and mode shapes of the casing under low-cycle load conditions. Based on the modal analysis results, the excitation frequency range and excitation form covering the resonant frequency range of the casing are determined; Under the prestressed condition, the excitation is applied to the casing, and harmonic response analysis is performed on the casing to obtain the axial stress amplitude and shear stress amplitude of the key test parts of the casing under the excitation. The axial stress amplitude and shear stress amplitude are then used as multiaxial high-cycle load stress information.

4. The method for predicting the multi-axis high- and low-cycle composite fatigue life of a multi-duct casing system as described in claim 1, characterized in that, The construction of a multi-axis high- and low-cycle composite load spectrum at the casing testing site includes: At the critical test points of the casing, multi-axis low-cycle load stress and multi-axis high-cycle load stress are superimposed to form a composite load that simultaneously includes multi-axis low-cycle load and multi-axis high-cycle load. Using a characteristic low-cycle load event and its corresponding complete high-cycle vibration process as the basic analysis unit, a multiaxial high- and low-cycle composite fatigue load block is constructed. Based on the load block, the number of high-cycle cycles n within the load block is determined according to the number of high-cycle vibrations experienced within a typical task profile time corresponding to a low-cycle load cycle. One or more load blocks are arranged in the order of the actual service mission time of the casing to form a multi-axis high-low cycle composite load spectrum characterizing the actual working conditions of the casing.

5. The method for predicting the multi-axis high- and low-cycle composite fatigue life of a multi-duct casing system as described in claim 1, characterized in that, The modeling and classification of multiaxial high- and low-cycle combined fatigue damage includes: The multiaxial high- and low-cycle combined fatigue damage is divided into multiaxial low-cycle fatigue damage, multiaxial high-cycle fatigue damage and multiaxial high- and low-cycle combined fatigue coupled damage. Among them, the determination of multiaxial low-cycle fatigue damage is based on the plastic strain amplitude generated during load cycling; The determination of multiaxial high-cycle fatigue damage is based on the superimposed multiaxial high-cycle vibration stress amplitude under the static average stress formed by low-cycle load; The multiaxial high- and low-cycle combined fatigue coupled damage is used to characterize the influence of material state changes caused by low-cycle loading on the evolution process of high-cycle fatigue damage.

6. The method for predicting the multi-axis high- and low-cycle composite fatigue life of a multi-duct casing system as described in claim 1, characterized in that, The construction of a multiaxial high- and low-cycle fatigue coupled damage term based on multiaxial fatigue damage parameters includes: using multiaxial low-cycle fatigue damage parameters and multiaxial high-cycle fatigue damage parameters as variables, constructing a multiaxial high- and low-cycle composite fatigue coupled damage term to characterize the interaction and mutual amplification effect between multiaxial low-cycle fatigue damage and multiaxial high-cycle fatigue damage. The coupled damage term includes: a factor characterizing the effect of high-cycle normal stress on the multiaxial high-low cycle combined fatigue life; a factor characterizing the effect of high-cycle shear stress on the multiaxial high-low cycle combined fatigue life; and a factor considering the nonlinear deviation effect of low-cycle cycling on high-cycle fatigue life.

7. The method for predicting the multi-axis high- and low-cycle composite fatigue life of a multi-duct casing system as described in claim 1, characterized in that, The calculation of the equivalent fatigue damage corresponding to each load block, using the load block as the basic analysis unit, includes: The multi-axis high- and low-cycle composite load spectrum is divided into multiple load blocks, each of which contains characteristic low-cycle load events and the complete high-cycle vibration process it carries. Based on the terms of multiaxial low-cycle fatigue damage, multiaxial high-cycle fatigue damage, and multiaxial high- and low-cycle combined fatigue coupled damage, the equivalent low-cycle fatigue damage, equivalent high-cycle fatigue damage, and equivalent coupled damage corresponding to each load block are calculated. The equivalent fatigue damage of each load block is obtained by accumulating the equivalent low-cycle fatigue damage, equivalent high-cycle fatigue damage, and equivalent coupling damage.

8. The method for predicting the multi-axis high- and low-cycle composite fatigue life of a multi-duct casing system as described in claim 1, characterized in that, The process involves accumulating multiaxial high- and low-cycle combined fatigue damage, establishing a multiaxial high- and low-cycle combined fatigue life prediction model, and outputting the fatigue life prediction results for the multi-duct casing system, including: Based on the equivalent fatigue damage corresponding to each load block, the multi-axis low-cycle fatigue damage, multi-axis high-cycle fatigue damage, and multi-axis high-low cycle combined fatigue coupled damage are cumulatively calculated according to the order of appearance and repetition of the load block in the load spectrum of the entire life of the casing. When the accumulated multi-axis high-low cycle composite fatigue damage reaches the preset failure criterion, fatigue failure is determined to have occurred at the test part of the casing, and the corresponding number of loads or equivalent service time is taken as the fatigue life of the casing. Based on the aforementioned accumulation process and failure determination results, a multi-axis high-low cycle composite fatigue life prediction model Ncode is established. In Ncode, a fatigue analysis module is built. The load spectrum is input to calculate the multiaxial low-cycle fatigue life, the multiaxial high-cycle fatigue life under low-cycle stress, and the high-low cycle load cycle ratio n in the fatigue load block. The results are then substituted into the multiaxial high-low cycle composite fatigue damage model to calculate the multiaxial high-cycle stress level multiaxial high-low cycle composite fatigue load block life.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the multi-axis high- and low-cycle composite fatigue life prediction method for a multi-duct casing system as described in any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the multi-axis high- and low-cycle composite fatigue life prediction method for a multi-duct casing system as described in any one of claims 1 to 8.

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