A multi-stage fatigue cumulative damage prediction method and system based on load sequence relationship

Abstract

The application relates to a multi-stage fatigue cumulative damage prediction method and system based on a load sequence relationship, which comprises the following steps: obtaining material performance data of a material to be predicted; calculating equivalent stress amplitude of each stage of load and total equivalent stress amplitude of each stage based on maximum normal stress and maximum shear stress amplitude; obtaining load cycle times and fatigue life of the next stage under each stage of load, and calculating the ratio of the load cycle times and the fatigue life; further determining an interaction effect coefficient; calculating a sequence effect coefficient according to the loading sequence of each stage of load and the interaction effect coefficient; calculating a weight factor of the next stage under each stage of load based on the ratio of the equivalent stress amplitude and the total equivalent stress amplitude of each stage and the sequence effect coefficient; and calculating the multi-stage fatigue cumulative total damage of the material to be predicted based on the weight factor, the equivalent stress amplitude and the total equivalent stress amplitude of each stage. Compared with the prior art, the application can accurately predict the multi-axial fatigue cumulative damage of the material.

Description

Technical Field

[0001] This invention relates to the field of load spectrum compilation technology for mechanical structure fatigue tests, and in particular to a multi-level fatigue cumulative damage prediction method and system based on load sequence relationship. Background Technology

[0002] Fatigue failure is one of the main failure modes of mechanical parts and engineering components, and its cumulative fatigue damage is a crucial and indispensable part of the structural design process. Because multiaxial fatigue cumulative damage is influenced by multiple dimensions of parameters such as stress concentration, material properties, load paths, and environmental factors, nominal stress methods and local stress-strain methods are commonly used in engineering for prediction. However, these methods have significant limitations in the application of multiaxial, multi-cycle loading conditions such as those affecting airfoils: insufficient prediction accuracy and large result dispersion. Fundamentally, these methods fail to reflect multiaxial stress interactions, ignore the damage acceleration effect under non-proportional loading, do not consider the inelastic deformation characteristics of multiaxial loads, and have unclear critical plane selection. This multi-scale, variable loading significantly increases the complexity of the damage accumulation mechanism under multiaxial loading, rendering the physical characterization capability of traditional single-dimensional prediction models insufficient, ultimately limiting the accuracy and stability of fatigue cumulative damage prediction.

[0003] While the Miner model's fatigue cumulative damage model is relatively simple and easy to calculate, it neglects the influence of load path and the magnitude and relationship of equivalent stress on the damage throughout the loading process, resulting in a conservative life prediction. The Morrow model, while considering the relationship between load levels, fails to account for the impact of load sequence on fatigue cumulative damage, and the influence of the number of loading cycles on the load relationship, leading to a decrease in prediction accuracy. The Masion model, while considering the relationship between fatigue life and reference life corresponding to each load level on damage prediction, does not consider the influence of loading path and the magnitude and relationship of equivalent stress on the overall fatigue cumulative damage prediction; moreover, the coefficient of variation increases significantly with the number of loading stages. Although these models are simple and easy to use, they all ignore the effect of load sequence. Therefore, this invention optimizes these models accordingly.

[0004] The invention disclosed in CN114036654B presents a method for compiling a multi-parameter fatigue test spectrum based on damage equivalence, comprising the following steps: obtaining a multi-parameter fatigue test spectrum model that fully incorporates the characteristics of actual multi-parameter loads; converting the preprocessed multi-parameter component load spectrum into the stress-strain history of fatigue test points, and solving the linear equations of local stress-strain and component load; discretizing the stress-strain history of fatigue test points over time, and determining the critical plane using a weight function based on time-varying damage parameters; calculating the total cumulative damage of the original load spectrum according to a multiaxial fatigue damage model; establishing the relationship between external loads and multiaxial damage, and optimizing the parameters of the multi-parameter fatigue test spectrum model; and randomly splicing each load level to synthesize a multi-parameter fatigue test spectrum with load characteristics and damage consistent with the original load spectrum. However, this scheme does not consider the influence of load sequence effects on fatigue cumulative damage, resulting in low prediction accuracy. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a multi-level fatigue cumulative damage prediction method and system based on load sequence relationship.

[0006] The objective of this invention can be achieved through the following technical solutions: A multi-level fatigue cumulative damage prediction method based on load sequence relationship includes: Obtain the material property data of the material to be predicted and determine the maximum normal stress and maximum shear stress amplitude of each load level; based on the maximum normal stress and maximum shear stress amplitude, calculate the equivalent stress amplitude of each load level and the sum of the equivalent stress amplitudes of each load level; Obtain the load cycle count and fatigue life of the next level of load at each level, and calculate the ratio of load cycle count to fatigue life; determine the interaction effect coefficient based on the ratio of load cycle count to fatigue life; calculate the sequence effect coefficient according to the loading order of each level of load and the interaction effect coefficient. Based on the ratio of the equivalent stress amplitude and the sum of the equivalent stress amplitudes at each level, and the order effect coefficient, the weighting factor of the next level of load is calculated; based on the weighting factor, the equivalent stress amplitude, and the sum of the equivalent stress amplitudes at each level, the total cumulative fatigue damage of the material to be predicted, including multi-level fatigue cumulative damage, is calculated.

[0007] Furthermore, based on the ratio of the equivalent stress amplitude and the sum of the equivalent stress amplitudes at each level, and the order effect coefficient, the weighting factor for the next level of load at each level is calculated, and the corresponding calculation formula is as follows: in, As the weighting factor for the next level, This is the order effect coefficient. This represents the ratio of the equivalent stress amplitude to the total stress amplitude under the next load level. This represents the number of cycles for the next load level. This represents the fatigue life corresponding to the next level of load. The accumulated damage value for the i-th level of loading.

[0008] Furthermore, the ratio of the equivalent stress amplitude to the sum of the equivalent stress amplitudes at each level is calculated using the following formula: in, It is the ratio of the equivalent stress amplitude to the total stress amplitude. Let be the equivalent stress of each load level, and k be the number of loading levels.

[0009] Furthermore, the total cumulative damage from multi-level fatigue is obtained by summing the cumulative damage from the first level fatigue, the cumulative damage from the second level fatigue, and the cumulative damage from the multi-level fatigue. Based on the equivalent stress amplitude and the sum of the equivalent stress amplitudes at each level, an initial weighting factor is calculated. The number of load cycles and the fatigue life corresponding to the first level load are obtained, and the ratio of the number of load cycles to the fatigue life is calculated. Based on the initial weighting factor and the ratio of the number of load cycles to the fatigue life, the first level fatigue cumulative damage is calculated.

[0010] Furthermore, the cumulative fatigue damage of the first stage is calculated using the following formula: in, This represents the first level of fatigue cumulative damage. The number of load cycles for the first level. This represents the fatigue life corresponding to Level 1 load. As the initial weighting factor, It is the ratio of the equivalent stress amplitude of the first-level load to the total stress amplitude.

[0011] Furthermore, the cumulative damage of the first-level fatigue and the cumulative damage of the second-level fatigue are summed to obtain the total cumulative damage of the two levels of fatigue. The corresponding calculation formula is as follows: in, This represents the cumulative total damage from two levels of fatigue. This represents the first level of fatigue cumulative damage. This represents the second level of fatigue cumulative damage. As the weighting factor for the first-level load, As a weighting factor for the second-level load, This represents the number of cycles for the first-stage load. This represents the fatigue life corresponding to the first level of load. This represents the number of cycles for the second-stage load. This represents the fatigue life corresponding to the second-level load.

[0012] Furthermore, the cumulative total damage from the multi-stage fatigue is calculated using the following formula: in, The total damage is accumulated from multiple levels of fatigue. As a weighting factor, For each load cycle, This represents the fatigue life corresponding to each load level.

[0013] Furthermore, a multi-axis cyclic block loading method based on random multi-level was used to conduct variable amplitude fatigue tests on different metallic materials and determine the maximum normal stress and maximum shear stress amplitude of each level.

[0014] Furthermore, based on the maximum normal stress and maximum shear stress amplitudes, the equivalent stress amplitude at each stage and the sum of the equivalent stress amplitudes at each stage are calculated. The corresponding calculation formula is as follows: in, This is the equivalent stress amplitude. For the maximum normal stress, This represents the maximum shear stress amplitude.

[0015] The present invention also provides a system for predicting multi-level fatigue cumulative damage based on load sequence relationship, including a memory and a processor, wherein the memory stores a computer program, and the processor calls the computer program to execute the steps of the method described above.

[0016] Compared with the prior art, the present invention has the following advantages: (1) This invention overcomes the inherent defect of the traditional Miner linear accumulation method, which completely ignores the influence of load sequence, by introducing interaction effect coefficients and sequence effect coefficients that consider the loading sequence of each load level. The traditional method assumes that the cumulative damage caused by high stress and low stress is the same regardless of the order in which they appear. However, a large number of experiments have shown that loading sequences of high stress followed by low stress and low stress followed by high stress lead to significantly different fatigue lives. By introducing sequence effect coefficients, this invention can quantify the enhancing or weakening effect of the previous load on the damage capability of the next load level. Furthermore, by designing interaction effect coefficients, it can further capture the coupling effect between load levels under different sequences. This allows the prediction results to truly reflect the nonlinear cumulative effect of load sequence on fatigue damage during the actual loading process, significantly improving the accuracy of fatigue life prediction under variable amplitude multiaxial loads.

[0017] (2) This invention successfully transforms complex multiaxial fatigue problems into equivalent uniaxial fatigue problems by converting the maximum normal stress and maximum shear stress under multiaxial stress states into equivalent stress amplitudes. Traditional fatigue cumulative damage methods are mostly designed for uniaxial tension, compression, or bending loads, and are difficult to apply directly to multiaxial loading conditions such as tension-torsion combined and bending-torsion combined. This invention effectively solves this limitation and can uniformly handle the common contribution of different stress components to fatigue damage under multiaxial stress states. This allows the method to be widely applied to engineering structures such as aero-engine turbine disks, vehicle axles, and wind turbine blades that bear complex multiaxial loads, greatly expanding the engineering applicability of fatigue life prediction methods.

[0018] (3) This invention requires relatively little experimental data while ensuring prediction accuracy, thus possessing good engineering feasibility. This invention primarily relies on the standard SN curve of the material, the number of cycles under various load levels, and limited multiaxial amplitude fatigue test data to complete model calibration and damage calculation. In contrast, many existing complex multiaxial fatigue models often require a large amount of system test data under different load paths, phase differences, and loading sequences to determine multiple empirical parameters, resulting in high data acquisition costs and long cycles, making them difficult to promote and apply in practical engineering. This invention simplifies the process through reasonable physical mechanisms, reducing the requirement for experimental data without significantly sacrificing accuracy, making the method more easily adopted and used by engineering design departments. Attached Figure Description

[0019] Figure 1 This is a flowchart of a multi-level fatigue cumulative damage prediction method based on load sequence relationship provided in an embodiment of the present invention; Figure 2 This is a simplified flowchart of a multi-level fatigue cumulative damage prediction method based on load sequence relationship provided in an embodiment of the present invention; Figure 3 The geometric shape of a 2024-T4 aluminum alloy sample is shown in the embodiment of the present invention for a multi-level fatigue cumulative damage prediction method based on load sequence relationship. Figure 4 The cumulative damage calculation results and bar charts for each model of 2024-T4 aluminum alloy based on a multi-level fatigue cumulative damage prediction method based on load sequence relationship provided in this embodiment of the invention are shown. Figure 5 The geometric shape of a 7075-T651 aluminum alloy sample is shown in the embodiment of the present invention for a multi-level fatigue cumulative damage prediction method based on load sequence relationship. Figure 6 The cumulative damage calculation results and bar charts for various models of 7075-T651 aluminum alloy are presented using a multi-level fatigue cumulative damage prediction method based on load sequence relationship. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0023] Definitions: Multiaxial cyclic block loading method: This is a loading method used in multiaxial fatigue testing to simulate actual complex load conditions. It divides the entire loading process into several loading blocks that are applied sequentially. Each loading block represents a relatively stable multiaxial stress state, and the same set of multiaxial load cycles are repeatedly applied within the block, such as a constant amplitude tensile-torsion composite load or a bending-torsion composite load. The magnitude, direction, phase difference, or combination of loads can be changed between different blocks, thereby forming a random multi-level or program-spectrum variable amplitude loading sequence.

[0024] The Miner model is the most classic and widely used cumulative damage theory in fatigue analysis. This model is based on two core assumptions: first, when a material is cyclically loaded at a certain stress level, the share of life consumed in each cycle is equal, meaning the damage caused by a single cycle is inversely proportional to the total fatigue life; second, fatigue damage caused by different stress levels can be linearly superimposed, independent of each other, and unaffected by the order in which the loads are applied.

[0025] Example 1 like Figure 1 As shown, this embodiment provides a multi-level fatigue cumulative damage prediction method based on load sequence relationship. The method includes the following steps: S1: Obtain the material property data of the material to be predicted and determine the maximum normal stress and maximum shear stress amplitude of each load level; based on the maximum normal stress and maximum shear stress amplitude, calculate the equivalent stress amplitude of each load level and the sum of the equivalent stress amplitudes of each load level; S101: Obtain material property data of the material to be predicted, conduct amplitude fatigue tests on different metal materials based on random multi-level multiaxial cyclic block loading, and determine the maximum normal stress and maximum shear stress amplitude at each level; S102: Based on Von Mise theory, the equivalent stress amplitude of each stage is calculated according to the maximum normal stress and maximum shear stress of each stage in the experiment; Preferred, If the equivalent stress amplitude is determined by using a multi-stage loading test method and the critical surface method, the specific method is as follows: conduct fatigue tests under multi-stage loading conditions, obtain the test normal stress and shear stress values ​​under each loading condition, and use the Von Mise formula to calculate the equivalent stress amplitude, thereby obtaining the equivalent stress amplitude of each stage of the metallic material.

[0026] Preferred, The equivalent stress Von Mise formula is: in, This is the equivalent stress amplitude. For the maximum normal stress, This represents the maximum shear stress amplitude.

[0027] S103: Based on the load relationship of each loading stage, establish a weighting factor based on the ratio of the equivalent stress amplitude to the sum of the equivalent stress amplitudes at each stage; S2: Obtain the load cycle count and fatigue life of the next level of load at each level, and calculate the ratio of load cycle count to fatigue life; determine the interaction effect coefficient based on the ratio of load cycle count to fatigue life; calculate the sequence effect coefficient according to the loading order of each level of load and the interaction effect coefficient; S201: Based on Miner's theory, a method for calculating multiaxial fatigue cumulative damage under various loading levels is established by introducing weighting factors to correct the damage caused by each level of load. Preferred, The fatigue life corresponding to each loading level can be calculated from fatigue tests or SN curves. The cumulative damage of each loading level can be predicted according to Miner's rule. in, For the first i The accumulated damage value under load level, For each load cycle, This represents the fatigue life corresponding to each load level.

[0028] S202: Based on the multiaxial fatigue cumulative damage calculation method under various loading levels, considering the load loading sequence, a sequence effect coefficient is introduced to correct the weighting factor. Preferred, The Miner model and weighting factors are modified based on the equivalent stress amplitude ratio and the total number of loading levels: in, The equivalent stress for each load level, k For loading levels, It is the ratio of the equivalent stress amplitude to the total stress amplitude. As a weighting factor, As the initial weighting factor, This represents the ratio of the equivalent stress amplitude under first-order load to the total stress amplitude. For each load cycle, This represents the fatigue life corresponding to each load level.

[0029] Preferred, Based on the enhancing or weakening effect of preceding high or low stress on subsequent damage, the weighting factor for the next level is adjusted according to the loading sequence as follows: in, As the weighting factor for the next level, This is the order effect coefficient. It is the ratio of the equivalent stress amplitude of the next level of load to the total stress amplitude.

[0030] Preferred, The formula for calculating the order effect coefficient is: Preferred, An interaction effect coefficient is introduced into the order effect coefficient of the weighting factor. This allows for the correction of cumulative fatigue damage across two or even multiple levels and axes. in, This represents the number of cycles for the next load level. This represents the fatigue life corresponding to the next level of load.

[0031] S3: Based on the ratio of the equivalent stress amplitude and the sum of the equivalent stress amplitudes at each level, and the order effect coefficient, calculate the weighting factor of the next level under each load level; based on the weighting factor, the equivalent stress amplitude, and the sum of the equivalent stress amplitudes at each level, calculate the total cumulative fatigue damage of the material to be predicted, including the cumulative fatigue damage at multiple levels.

[0032] S301: Based on the multiaxial cumulative damage calculation method and correction weighting factor under each level of loading, a multiaxial fatigue cumulative damage model under first-level loading is established. Preferred, The first-order damage model is as follows: in, This represents the damage value under first-level loading. The number of first-level load cycles, This represents the fatigue life corresponding to the first-level load.

[0033] S302: Based on the number of second-level cycles and its corresponding fatigue life ratio, the two-level loading model is further modified to obtain a multiaxial fatigue cumulative damage model. S303: Derive a multi-level multiaxial cumulative damage model based on a two-level cumulative damage model; predict fatigue cumulative damage of materials based on loading data from multiaxial tests.

[0034] Preferred, Based on the impact of the next level of loading cycles on the sequence effect coefficient and subsequent damage, the secondary damage model and even the multi-level damage model are further modified as follows: The total damage is: in, For the total damage under two-stage loading, This represents the total damage from multi-stage loading.

[0035] Preferred, The cumulative damage of the first-level fatigue and the cumulative damage of the second-level fatigue are summed to obtain the total cumulative damage of the two levels of fatigue. The corresponding calculation formula is as follows: in, This represents the cumulative total damage from two levels of fatigue. This represents the first level of fatigue cumulative damage. This represents the second level of fatigue cumulative damage. This is the weighting factor for the first-level load. As a weighting factor for the second-level load, This represents the number of cycles for the first-stage load. This represents the fatigue life corresponding to the first level of load. This represents the number of cycles for the second-stage load. This represents the fatigue life corresponding to the second-level load.

[0036] Example 2 like Figure 2As shown, this embodiment provides a method for predicting multiaxial fatigue cumulative damage, where the predicted material is 2024-T4 aluminum alloy, and includes the following steps: like Figure 3 The image shows the mechanical properties and specimen geometry of 2024-T4 aluminum alloy. Fatigue tests were conducted under multiple loading conditions to construct multiple loading spectra, obtaining the number of test cycles under each loading condition. The ratio of the number of cycles at each loading level to the corresponding fatigue life was calculated, thereby determining the total cumulative damage value. In this embodiment, the number of cycles at each loading level is 5% of the corresponding fatigue life at that level. Number of blocks loaded: in, This represents the total cumulative damage value. For each load cycle, This represents the fatigue life corresponding to each load level.

[0037] Fatigue tests were conducted under multiple load conditions to obtain the normal stress and shear stress values ​​and corresponding lifespans under each load condition. The Von Mise equivalent stress amplitude was used to obtain the equivalent stress amplitudes for each load level in the metallic material.

[0038] The equivalent stress Von Mise formula is: in, This is the equivalent stress amplitude. For the maximum normal stress, This represents the maximum shear stress.

[0039] The Miner model and weighting factors are modified based on the equivalent stress amplitude ratio and the total number of loading levels: in, The equivalent stress for each load level, k For loading levels, It is the ratio of the equivalent stress amplitude to the total stress amplitude. As a weighting factor, As the initial weighting factor, It is the ratio of the equivalent stress amplitude of the first-level load to the total stress amplitude.

[0040] Based on the enhancing or weakening effect of preceding high or low stress on subsequent damage, the weighting factor for the next level is adjusted as follows: in, As the weighting factor for the next level, This is the order effect coefficient. To further refine the Miner model to account for the influence of the equivalent stress amplitude of the next-level load and the number of loading cycles based on the next level on the sequence effect coefficient and subsequent damage, an interaction effect coefficient is introduced into the sequence effect coefficient part of the model. This yields a modified two-level or even multi-level multiaxial fatigue cumulative damage model: The first-order damage model is as follows: in, This represents the damage value under first-level loading. The number of load cycles for the first level. This represents the fatigue life corresponding to the first-level load.

[0041] Based on the influence of the number of loading cycles at the next level on the sequential effect coefficient and subsequent damage, further corrections are made to obtain a two-level or even multi-level multiaxial fatigue cumulative damage model: The total damage is: in, The total damage is due to two levels of loading. This represents the total damage from multi-stage loading.

[0042] To verify the effectiveness of the multiaxial fatigue cumulative damage prediction method based on load sequence and load interaction proposed in this invention, the model prediction results of 2024-T4 aluminum alloy obtained by the method proposed in this invention for predicting fatigue cumulative damage were compared with the prediction results of the Miner model, Morrow model, and Masion model. Figure 4 Wherein, Palmgren-Miner law represents the Miner model, Morrow's law represents the Morrow model, Masion's law represents the Masion model, and the Proposed model represents the fatigue cumulative damage prediction model of this invention.

[0043] The results show that, when the multiaxial fatigue cumulative damage value obtained by the prediction method of this invention is compared with the multiaxial fatigue cumulative damage value obtained by the Miner model, Morrow model and Masion model, the prediction result obtained by this invention is closer to the actual cumulative damage value and has higher accuracy.

[0044] Example 3 This embodiment provides a method for predicting multiaxial fatigue cumulative damage, where the predicted material is 7075-T651 aluminum alloy, and includes the following steps: like Figure 5 The image shows the mechanical properties and specimen geometry of 7075-T651 aluminum alloy. Fatigue tests were conducted on a single piece under two-stage loading conditions. The number of test cycles under the loading conditions was obtained, and the ratio of the number of cycles per stage to the corresponding fatigue life was calculated, thereby determining the total cumulative damage value. in, This represents the total cumulative damage value. For each load cycle, This represents the fatigue life corresponding to each load level.

[0045] Fatigue tests were conducted under multiple load conditions to obtain the normal stress and shear stress values ​​and corresponding lifespans under each load condition, and the equivalent stress corresponding to each path was calculated. The Von Mise equivalent stress amplitude was used to obtain the equivalent stress amplitudes for each load level in the metallic material.

[0046] The equivalent stress Von Mise formula is: in, This is the equivalent stress amplitude. For the maximum normal stress, This represents the maximum shear stress.

[0047] To determine the loading path and sequence, as well as the number of loading cycles and lifetime at each stage, the Miner model and weighting factors are modified based on the equivalent stress amplitude ratio and the total number of loading stages: in, The equivalent stress of each load level, k For loading levels, It is the ratio of the equivalent stress amplitude to the total stress amplitude. As a weighting factor, As the initial weighting factor, It is the ratio of the equivalent stress amplitude of the first-level load to the total stress amplitude.

[0048] Based on the correction of the enhancing or weakening effect of preceding high or low stress on subsequent damage, the weighting factor for the next level is: in, As the weighting factor for the next level, This is the order effect coefficient. To further adjust the weighting factors for the influence of the equivalent stress amplitude of the next-level load and the number of loading cycles based on the next level on the sequence effect coefficient and subsequent damage, an interaction effect coefficient is introduced into the sequence effect coefficient part of the model. The corrected weighting factor is obtained as follows: The two-stage or even multi-stage multiaxial fatigue cumulative damage model is further modified based on the influence of the number of loading cycles at the next stage on the sequential effect coefficient and subsequent damage: in, The total damage is due to two levels of loading.

[0049] To verify the effectiveness of the multiaxial fatigue cumulative damage prediction method based on load sequence and load interaction proposed in this invention, the model prediction results of 7075-T651 aluminum alloy obtained by the method proposed in this invention for predicting fatigue cumulative damage were compared with the prediction results of the Miner model, Morrow model, and Masion model. Figure 6 The results show that, when the multiaxial fatigue cumulative damage value obtained by the prediction method of this invention is compared with the multiaxial fatigue cumulative damage values ​​obtained by the Miner model, Morrow model and Masion model, the prediction result obtained by this invention is closer to the actual cumulative damage value1, and has higher accuracy.

[0050] Example 4 This embodiment also provides an electronic device, including a processor, a memory, and a program stored in the memory, wherein the processor executes the program to implement any of the methods described above.

[0051] Example 5 This embodiment also provides a computer-readable storage medium storing a corresponding program that, when executed, implements all the methods described above.

[0052] If the aforementioned functions are implemented as software functional modules and are sold or used independently, they can be packaged and stored in a computer-readable storage medium. Under this technical architecture, the innovative technical features of this invention (including technical solutions or components that substantially improve upon existing technologies) can be presented through standardized software carriers. Such computer software products can reside in any applicable storage medium, and their built-in program instructions can guide computing devices (including personal terminals, server clusters, and network devices, etc.) to fully or partially execute the technical processes defined in the various embodiments of this invention. Applicable storage media include, but are not limited to, the following types: semiconductor memories (such as ROM read-only memory, RAM random access memory), magnetic storage media (such as portable hard drives, magnetic disks), optical storage media (such as CD / DVD discs), and flash memory devices (such as USB flash drives), etc., which are physical carriers capable of persistently storing program instructions.

[0053] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A multi-level fatigue cumulative damage prediction method based on load sequence relationship, characterized in that, include: Obtain material property data of the material to be predicted and determine the maximum normal stress and maximum shear stress amplitude under each load level; Based on the maximum normal stress and maximum shear stress amplitudes, calculate the equivalent stress amplitude for each load level and the sum of the equivalent stress amplitudes for each load level; Obtain the load cycle count and fatigue life of the next level of load at each level, and calculate the ratio of load cycle count to fatigue life; Based on the ratio of the number of load cycles to the fatigue life, the interaction effect coefficient is determined; according to the loading sequence of each load level and the interaction effect coefficient, the sequence effect coefficient is calculated. Based on the equivalent stress amplitude and the ratio of the sum of equivalent stress amplitudes at each level, and the order effect coefficient, calculate the weighting factor for the next level of load at each level; Based on the weighting factor, the equivalent stress amplitude, and the sum of the equivalent stress amplitudes at each level, the total cumulative fatigue damage of the material to be predicted, including the cumulative fatigue damage at multiple levels, is calculated.

2. The multi-level fatigue cumulative damage prediction method based on load sequence relationship according to claim 1, characterized in that, Based on the ratio of the equivalent stress amplitude and the sum of the equivalent stress amplitudes at each level, and the order effect coefficient, the weighting factor for the next level of load at each level is calculated, and the corresponding calculation formula is as follows: in, As the weighting factor for the next level, This is the order effect coefficient. This represents the ratio of the equivalent stress amplitude to the total stress amplitude under the next load level. This represents the number of load cycles for the next level. This represents the fatigue life corresponding to the next level of load. The accumulated damage value for the i-th level of loading.

3. The multi-level fatigue cumulative damage prediction method based on load sequence relationship according to claim 2, characterized in that, The ratio of the equivalent stress amplitude to the sum of the equivalent stress amplitudes at each level is calculated using the following formula: in, It is the ratio of the equivalent stress amplitude to the total stress amplitude. Let be the equivalent stress of each load level, and k be the number of loading levels.

4. The multi-level fatigue cumulative damage prediction method based on load sequence relationship according to claim 1, characterized in that, The total cumulative damage from multi-level fatigue is obtained by summing the cumulative damage from the first level fatigue, the cumulative damage from the second level fatigue, and the cumulative damage from multi-level fatigue; an initial weighting factor is calculated based on the equivalent stress amplitude and the sum of the equivalent stress amplitudes at each level. Obtain the load cycle number and fatigue life corresponding to the first level load, and calculate the ratio of load cycle number to fatigue life; The first-level fatigue cumulative damage is calculated based on the ratio of the initial weighting factor, the number of load cycles, and the fatigue life.

5. The multi-level fatigue cumulative damage prediction method based on load sequence relationship according to claim 4, characterized in that, The formula for calculating the first-level fatigue cumulative damage is as follows: in, This represents the first level of fatigue cumulative damage. The number of first-level load cycles, This represents the fatigue life corresponding to Level 1 load. As the initial weighting factor, It is the ratio of the equivalent stress amplitude of the first-level load to the total stress amplitude.

6. The multi-level fatigue cumulative damage prediction method based on load sequence relationship according to claim 4, characterized in that, The cumulative fatigue damage of the first stage and the cumulative fatigue damage of the second stage are summed to obtain the total cumulative fatigue damage of the two stages. The corresponding calculation formula is as follows: in, This represents the cumulative total damage from two levels of fatigue. This represents the first level of fatigue cumulative damage. This represents the second level of fatigue cumulative damage. This is the weighting factor for the first-level load. As a weighting factor for the second-level load, This represents the number of cycles for the first-stage load. This represents the fatigue life corresponding to the first level of load. This represents the number of cycles for the second-stage load. This represents the fatigue life corresponding to the second-level load.

7. The multi-level fatigue cumulative damage prediction method based on load sequence relationship according to claim 4, characterized in that, The formula for calculating the cumulative total damage from the multi-stage fatigue is as follows: in, The total damage is accumulated from multiple levels of fatigue. As a weighting factor, For each load cycle, This represents the fatigue life corresponding to each load level.

8. The multi-level fatigue cumulative damage prediction method based on load sequence relationship according to claim 1, characterized in that, A multi-axis cyclic block loading method based on random multi-level was used to conduct variable amplitude fatigue tests on different metallic materials and determine the maximum normal stress and maximum shear stress amplitude of each level.

9. The multi-level fatigue cumulative damage prediction method based on load sequence relationship according to claim 1, characterized in that, Based on the maximum normal stress and maximum shear stress amplitudes, the equivalent stress amplitude at each stage and the sum of the equivalent stress amplitudes at each stage are calculated. The corresponding calculation formula is as follows: in, This is the equivalent stress amplitude. For the maximum normal stress, This represents the maximum shear stress amplitude.

10. A system for predicting multi-level fatigue cumulative damage based on load sequence relationships, characterized in that, It includes a memory and a processor, the memory storing a computer program, the processor invoking the computer program to perform the steps of the method as described in any one of claims 1 to 9.

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