High-low cycle composite fatigue life prediction method and system considering amplitude-frequency ratio, electronic equipment and medium

Abstract

The invention belongs to the field of fatigue life prediction, and particularly provides a high-low cycle composite fatigue life prediction method considering an amplitude-frequency ratio, and the method comprises the steps: enabling loads under different stress ratio conditions to be equivalent to equivalent stress under stress ratios through employing a Gerber average stress correction method for a high cycle fatigue load, and achieving the data unification under different load conditions; mathematical expressions of high-cycle fatigue life and low-cycle fatigue life are unified in a power exponent form, and a weighting function reflecting the influence of the high-cycle and low-cycle stress amplitude ratio on accumulated damage and a strengthening function considering the interaction of the high-cycle and low-cycle stress amplitude ratio and the frequency ratio are established; and a high-low cycle composite fatigue life prediction model is constructed. The method solves the problem of low life prediction precision caused by the fact that an existing high-low cycle composite fatigue life prediction method does not consider the influence of a high-low cycle stress amplitude ratio and a high-low cycle stress frequency ratio on accumulated damage, and has high prediction precision.

Description

Technical Field

[0001] This invention belongs to the field of fatigue life prediction, specifically relating to a method, system, electronic equipment, and medium for predicting the high- and low-cycle composite fatigue life of key components such as turbine runners, considering the amplitude-to-frequency ratio. Background Technology

[0002] Hydropower, as my country's most technologically mature and flexibly dispatchable clean energy source, possesses three strategic functions: clean energy supply, optimized water resource allocation, and grid security assurance, making it a core pillar of the national energy strategy. With the increasing proportion of hydropower in my country's power system and the improvement in turbine head and capacity, reducing the failure rate of large turbine units is becoming increasingly important for the safe operation of the entire power generation system. The turbine runner, as a key component for energy conversion in turbine units, endures complex and extreme loads over long periods during its service life. Many turbine unit failures are caused by runner fatigue failure, which can lead to irreversible losses or even catastrophic consequences. Therefore, ensuring the fatigue strength and reliability of the runner is of paramount importance.

[0003] Fatigue is one of the main failure modes of turbine runners. As a core component for energy conversion, the runner blades endure complex and extreme high- and low-cycle combined fatigue loads over long periods during service. An investigation of crack initiation and propagation locations in the runner revealed that cracks initiate at the connection between the blade and the upper crown / lower ring, and tend to propagate towards the blade substrate. Furthermore, a comparison with fluid-structure interaction simulation results confirms that the maximum stress occurs at the connection between the blade and the upper crown / lower ring. Therefore, it can be further confirmed that the key location for fatigue failure of the runner lies at the connection between the runner blade and the upper crown / lower ring. These blades have complex shapes and are connected to the upper crown / lower ring via welding, making them prone to stress concentration at the connection under complex and extreme loads. If the design is inadequate, the fatigue life cannot be guaranteed.

[0004] In summary, to achieve fatigue life prediction for turbine runners, ensure their safe and reliable operation, and propose scientific and effective operation and maintenance solutions, research on turbine runner fatigue life prediction should be conducted first. However, current methods for predicting the combined high- and low-cycle fatigue life of turbine runners face the following problems: The methods for predicting the combined high- and low-cycle fatigue life of turbine runners are not yet perfect. Current mainstream methods include Miner's linear rule and the nonlinear cumulative damage criterion developed from it, but whether these methods are applicable to the prediction of the combined high- and low-cycle fatigue life of turbine runners has not been verified. During service, turbine runners are subjected to combined high- and low-cycle fatigue loads, and fatigue life prediction requires consideration of the damage caused by different types of loads and their coupling effects. Therefore, developing an efficient and accurate method for predicting the combined high- and low-cycle fatigue life of turbine runner materials is one of the main problems that urgently needs to be solved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method, system, electronic device and medium for predicting high-low cycle composite fatigue life that takes into account the amplitude-frequency ratio. This solves the problem that current high-low cycle composite fatigue life prediction methods do not consider the influence of the high-low cycle stress amplitude ratio and the high-low cycle stress frequency ratio on cumulative damage, resulting in low life prediction accuracy.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for predicting the combined fatigue life of high and low cycles considering the amplitude-frequency ratio, comprising the following steps: S1. Convert the high-cycle fatigue load into a stress ratio using the Gerber mean stress correction method. The equivalent stress under; S2. Fit the high-cycle fatigue life and low-cycle fatigue life using a power-law form. S3. Based on the high- and low-cycle combined fatigue load spectrum, construct a weighting function that reflects the influence of the high- and low-cycle stress amplitude ratio on cumulative damage. ; S4. Based on the high-low cycle composite fatigue load spectrum, construct a strengthening function that reflects the influence of the high-low cycle stress amplitude ratio and the high-low cycle stress frequency ratio on cumulative damage. ; S5. Construct a high-low cycle combined fatigue life prediction model and substitute the high-low cycle combined fatigue test data into the model parameters. S6. Calculate the number of load blocks when the cumulative damage reaches the critical damage level, and complete the fatigue life prediction.

[0007] In a preferred embodiment, the step S1 of converting high-cycle fatigue loads using the Gerber mean stress correction method includes the following steps: S101, First, convert the high-cycle fatigue load to a stress ratio. Equivalent stress The calculation formula is: (1); in, This represents the stress amplitude under high-cycle fatigue load. This represents the average stress under high-cycle fatigue loads. The tensile strength of the welding material for the rotating wheel; S102, After solving the problem, the stress ratio can be obtained by inversely solving the Gerber formula. Equivalent stress The calculation formula is: (2); in, Stress ratio The mean of the equivalent stress, and ; Indicates to Solve the problem.

[0008] In the preferred embodiment, in step S2, the power-law fitting expression for low-cycle fatigue life is: (3); in, This represents the stress amplitude under low-cycle fatigue loads. These are the fitting parameters for the model.

[0009] In the preferred embodiment, in step S2, the power-law fitting expression for high-cycle fatigue life is: (4); in, This represents the stress amplitude under high-cycle fatigue load. These are the fitting parameters for the model.

[0010] In a preferred embodiment, the weighting function constructed in step S3 that reflects the influence of the high-cycle and low-cycle stress amplitude ratio on cumulative damage... The expression is: (5); in, This represents the maximum stress under combined high- and low-cycle fatigue loads. This represents the average stress under combined high- and low-cycle fatigue loads.

[0011] In the preferred embodiment, the Reflecting the ratio of high- and low-cycle stress amplitudes, under the same maximum stress, an increase in the ratio of high- and low-cycle stress amplitudes indicates an increase in average stress. Decrease, making Increase; decrease the ratio of high- and low-cycle stress amplitudes, then the average stress Increase, making Decrease.

[0012] In a preferred embodiment, in step S4, the constructed strengthening function reflects the influence of the ratio of high-cycle stress amplitude and the ratio of high-cycle stress frequency on cumulative damage. The expression is: (6); in, This represents the threshold for low-load enhancement.

[0013] In a preferred embodiment, the low-load strengthening threshold This was determined by analyzing high- and low-cycle combined fatigue test data.

[0014] In the preferred embodiment, in step S5, the formula for calculating the cumulative damage of a single load block in the high-low cycle combined fatigue life prediction model is: (7); in, It represents the ratio of high-frequency to low-frequency stress.

[0015] In a preferred embodiment, the formula for calculating the number of load blocks when the accumulated damage reaches the critical damage in step S6 is as follows: (8); in, This represents the number of load blocks.

[0016] The present invention also provides a high-low cycle composite fatigue life prediction system considering the amplitude-frequency ratio, for performing the above-described high-low cycle composite fatigue life prediction method considering the amplitude-frequency ratio, comprising: The equivalent stress conversion module is used to convert high-cycle fatigue loads into stress ratios using the Gerber mean stress correction method. The equivalent stress under; The life fitting module is used to fit high-cycle fatigue life and low-cycle fatigue life in a unified power-law form. The weighting function construction module is used to construct a weighting function that reflects the influence of the high-low cycle stress amplitude ratio on cumulative damage based on the high-low cycle combined fatigue load spectrum. ; The reinforcement function construction module is used to construct reinforcement functions based on the high-low cycle combined fatigue load spectrum, reflecting the influence of the high-low cycle stress amplitude ratio and the high-low cycle stress frequency ratio on cumulative damage. ; The model building and parameter fitting module is used to build a high-low cycle combined fatigue life prediction model and fit the model parameters by substituting high-low cycle combined fatigue test data. The life calculation module is used to calculate the number of load blocks when the cumulative damage reaches the critical damage level, and to complete the fatigue life prediction.

[0017] The present invention also provides an electronic device for predicting high- and low-frequency combined fatigue life considering the amplitude-to-frequency ratio, comprising a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the high- and low-frequency combined fatigue life prediction method considering the amplitude-to-frequency ratio as described above.

[0018] The present invention also provides a storage medium for predicting high- and low-frequency composite fatigue life considering the amplitude-frequency ratio. The storage medium is a computer-readable storage medium, and a computer program is stored on the computer-readable storage medium. When the computer program is executed by a processor, it implements the high- and low-frequency composite fatigue life prediction method considering the amplitude-frequency ratio as described above.

[0019] The present invention provides a method, system, electronic device, and medium for predicting high- and low-frequency composite fatigue life considering the amplitude-to-frequency ratio, which has the following beneficial effects: 1. Based on high-low cycle combined fatigue tests, this invention further clarifies the influence of the high-low cycle stress amplitude ratio and the high-low cycle stress frequency ratio on fatigue life through analysis of test results. It proposes a high-low cycle combined fatigue life prediction model based on nonlinear cumulative damage and considering different high-low cycle stress amplitude ratios and high-low cycle stress frequency ratios. The model fitting parameters are calibrated using high-low cycle combined fatigue test data, eliminating the need to conduct separate low-cycle and high-cycle fatigue tests.

[0020] 2. The established high- and low-cycle composite fatigue life prediction model has high prediction accuracy. Experimental data validates that the model's average fatigue life prediction accuracy is within the 2x error band, meeting the accuracy requirements for engineering life prediction. When dealing with practical engineering problems where fatigue life exhibits significant dispersion, the proposed model demonstrates good robustness and reliability, effectively addressing prediction uncertainties caused by material defects, manufacturing process differences, and other factors, ensuring the stability and safety of life assessment.

[0021] 3. The proposed model uses unified parameters for fitting high-cycle and low-cycle fatigue lives, avoiding the fitting errors and uncertainties caused by the need to separately fit pure low-cycle and pure high-cycle fatigue life curves in traditional methods. Through unified fitting parameters, the model can directly characterize material fatigue performance based on high- and low-cycle composite fatigue test data without relying on additional pure fatigue tests, reducing the experimental burden. This approach not only improves the stability and consistency of parameter fitting but also effectively reduces the impact of life dispersion caused by material defects and welding processes, making the model more applicable and practical in engineering applications.

[0022] 4. The proposed model considers the influence of the high-cycle stress amplitude ratio and the high-cycle stress frequency ratio on fatigue life. Based on the cumulative damage theory, these influences are transformed into a modulating effect on damage accumulation through a modulation function. The influence of the high-cycle stress amplitude ratio is reflected by introducing a weighting function to show the weight difference in the contribution of different high-cycle fatigue load ratios to fatigue damage. The influence of the high-cycle stress frequency ratio is controlled by a strengthening function to regulate the proportion of cumulative damage of high-cycle fatigue load within a load block.

[0023] 5. A characterization mechanism for low-load strengthening effect was introduced in the model construction by setting a maximum stress threshold. Furthermore, by incorporating the physical mechanism of low-load strengthening, the damage evolution behavior under different load levels was differentiated. This model can effectively handle situations where the maximum stress is below a threshold. At that time, the phenomenon of increased fatigue life caused by high-cycle fatigue loads provides a unified description of the competing effects of low-load strengthening and fatigue damage, expanding the applicability and explanatory power of traditional fatigue life models. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 Standard dimensions of the welding joint for the wheel material provided in this invention example; Figure 2 The load spectrum of high- and low-cycle combined fatigue test; Figure 3 A flowchart of a solution provided for an example of the present invention; Figure 4 The effect of the ratio of high- and low-cycle stress amplitudes on fatigue life; Figure 5 The effect of the high-low cycle stress frequency ratio on fatigue life; Figure 6 This is a comparison between the prediction results of the method of the present invention and the average test lifespan; Figure 7 This is a comparison chart of the prediction accuracy of the method of the present invention and the PM model; Figure 8 This is a comparison chart of the prediction accuracy of the method of the present invention and the TK model. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0026] Example 1: This invention utilizes high- and low-cycle combined fatigue tests on standard welded joint components of turbine runner materials. Based on the test data, the proposed life prediction method is fitted and validated. The base material of the standard welded joint components used in the tests is ZG04Cr13Ni5Mo, and the welding material is ER316L. Its dimensions are as follows... Figure 1 As shown, (a) represents the geometric dimensions of the standard welded joint of the turbine material; (b) represents the bevel geometric dimensions of the standard welded joint of the turbine material. The design and fabrication of the standard welded joint of the turbine material are carried out in accordance with "GB / T 3075-2021 Method for Axial Force Control in Fatigue Testing of Metallic Materials" and "GB / T 985.1-2008 Recommended Bevels for Gas Welding, Shielded Metal Arc Welding, and Gas Shielded Welding with High Energy Beams". The high-low cycle composite fatigue test is conducted at room temperature, and the load spectrum used in the test is as follows: Figure 2As shown in Table 1, specific experimental parameters were used, employing three load spectra covering different high- and low-cycle stress amplitude ratios and high- and low-cycle stress frequency ratios. Each load spectrum included six stress levels. The mechanical properties of ER316L material are detailed in Table 2. For tensile strength, For yield strength, Elongation after fracture, Reduction of area The elastic modulus is obtained through static tensile testing. The physical meaning of the parameters can be found in the material datasheets for those skilled in the art, and will not be elaborated in detail here.

[0027]

[0028]

[0029] A method for predicting high- and low-cycle combined fatigue life that considers the amplitude-to-frequency ratio, such as Figure 3 As shown, it includes the following steps: S1. To ensure that the constructed model has a unified evaluation benchmark, the high-cycle fatigue load needs to be equivalently converted into a stress ratio using the Gerber mean stress correction method. The equivalent stress under the condition is maintained at the same stress reference as the low-cycle fatigue load. Specifically, this includes the following steps: S101, First, convert the high-cycle fatigue load to a stress ratio. Equivalent stress The calculation formula is: (1); in, This represents the stress amplitude under high-cycle fatigue load. This represents the average stress under high-cycle fatigue loads. In this embodiment, the tensile strength of the welding material for the rotating wheel is considered. .

[0030] S102, After solving the problem, the stress ratio can be obtained by inversely solving the Gerber formula. Equivalent stress The expression is: (2); in, Stress ratio The mean of the equivalent stress, and ; Indicates to Solve the problem.

[0031] S2. The high-cycle fatigue life and low-cycle fatigue life are fitted using a power-law form.

[0032] To avoid introducing errors by separately fitting the fatigue SN curves of pure low-cycle and pure high-cycle, which would lead to error propagation and superposition during high-low cycle combined fatigue tests and result in poor prediction accuracy, the high-cycle fatigue life and low-cycle fatigue life are uniformly fitted using a power exponential form.

[0033] The power-law fit expression for low-cycle fatigue life is: (3); in, This represents the stress amplitude under low-cycle fatigue loads. These are the fitting parameters for the model.

[0034] The power-law fitting expression for high-cycle fatigue life is: (4); in, This represents the stress amplitude under high-cycle fatigue load. The fitting parameters for the model are specifically determined by substituting high- and low-cycle combined fatigue test data and using the least squares method for fitting. The specific values ​​of the fitting parameters in this example are: .

[0035] S3. Based on the high- and low-cycle combined fatigue load spectrum, construct a weighting function that reflects the influence of the high- and low-cycle stress amplitude ratio on cumulative damage. .

[0036] Based on the analysis of the test results, such as Figure 4 As shown, under the same maximum stress, fatigue life decreases as the ratio of high-cycle to low-cycle stress amplitudes increases. Based on this, to improve the physical rationality and prediction accuracy of the model, the influence of the high-cycle to low-cycle stress amplitude ratio is introduced into the damage model, constructing a weighting function that reflects the effect of the high-cycle to low-cycle stress amplitude ratio on cumulative damage. .

[0037] Weighting function The expression is: (5); in, This represents the maximum stress under combined high- and low-cycle fatigue loads. This represents the average stress under combined high- and low-cycle fatigue loads.

[0038] Essentially, it reflects the ratio of high- and low-cycle stress amplitudes. Under the same maximum stress, an increase in the ratio of high- and low-cycle stress amplitudes indicates an increase in average stress. Decrease, making Increase; decrease the ratio of high- and low-cycle stress amplitudes, then the average stress Increase, making Decrease.

[0039] S4. Based on the high-low cycle composite fatigue load spectrum, construct a strengthening function that reflects the influence of the high-low cycle stress amplitude ratio and the high-low cycle stress frequency ratio on cumulative damage. .

[0040] Based on the failure mechanism analysis of high-cycle and low-cycle combined fatigue, when the material is subjected to a low level of fatigue load, the frequent excitation of high-cycle fatigue load causes periodic compression of the material near the crack tip, thereby enhancing the crack closure effect and alleviating fatigue damage. As the high-cycle and low-cycle stress frequency ratio increases, the number of high-cycle fatigue load cycles within a single load block increases, making this crack closure effect more complete, further enhancing the strengthening effect, and increasing fatigue life. Furthermore, based on the analysis of experimental results, if... Figure 5 As shown, the strengthening effect has a threshold. A reinforcement function was constructed. The coupling effect of the high-low cycle stress amplitude ratio and the high-low cycle stress frequency ratio on the low load strengthening effect is comprehensively considered.

[0041] Strengthening function The expression is: (6); in, The low-load strengthening threshold. In this embodiment, to determine the method by analyzing high- and low-cycle combined fatigue test data, .

[0042] S5. Construct a high-low cycle combined fatigue life prediction model and substitute the high-low cycle combined fatigue test data into the model parameters.

[0043] Substituting the high-low cycle combined fatigue test data into the model parameters using the least squares method, a high-low cycle combined fatigue life prediction model is established. The formula for calculating the cumulative damage of a single load block is as follows: (7); in, It represents the ratio of high-frequency to low-frequency stress.

[0044] S6. Calculate the number of load blocks when the cumulative damage reaches the critical damage level, and complete the fatigue life prediction.

[0045] High- and low-cycle combined fatigue life is measured by the number of load blocks at which cumulative damage reaches critical damage. The formula for calculating the number of load blocks is: (8); in, This represents the number of load blocks.

[0046] To verify the effectiveness of the high-low cycle combined fatigue life prediction method considering the amplitude-frequency ratio proposed in this invention, the fatigue life prediction results obtained by this method are compared with the average test life of standard welded joint parts of turbine materials obtained under high-low cycle combined fatigue tests. Figure 6 As shown, the predicted fatigue life obtained by the calculation method of this invention has an error of less than 100% compared with the average actual fatigue life obtained in the experiment. Within the error band, this indicates that the proposed method achieves good prediction results for high- and low-cycle combined fatigue life estimation, and at the same time, it has higher accuracy than existing models. Figure 7 and Figure 8 As shown.

[0047] Example 2: This embodiment provides a high-low cycle combined fatigue life prediction system considering the amplitude-frequency ratio, used to execute the high-low cycle combined fatigue life prediction method considering the amplitude-frequency ratio described in Embodiment 1, including: The equivalent stress conversion module is used to convert high-cycle fatigue loads into stress ratios using the Gerber mean stress correction method. The equivalent stress under; The life fitting module is used to fit the weekly fatigue life and low-cycle fatigue life in a power-law form. The weighting function construction module is used to construct a weighting function that reflects the influence of the high-low cycle stress amplitude ratio on cumulative damage based on the high-low cycle combined fatigue load spectrum. ; The reinforcement function construction module is used to construct reinforcement functions based on the high-low cycle combined fatigue load spectrum, reflecting the influence of the high-low cycle stress amplitude ratio and the high-low cycle stress frequency ratio on cumulative damage. ; The model building and parameter fitting module is used to build a high-low cycle combined fatigue life prediction model and fit the model parameters by substituting high-low cycle combined fatigue test data. The life calculation module is used to calculate the number of load blocks when the cumulative damage reaches the critical damage level, and to complete the fatigue life prediction.

[0048] Example 3: This embodiment provides an electronic device for predicting high- and low-frequency composite fatigue life considering the amplitude-to-frequency ratio, including a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the high- and low-frequency composite fatigue life prediction method considering the amplitude-to-frequency ratio as described in Embodiment 1.

[0049] Example 4: This embodiment provides a storage medium for predicting high- and low-frequency composite fatigue life considering the amplitude-frequency ratio. The storage medium is a computer-readable storage medium, and a computer program is stored on the computer-readable storage medium. When the computer program is executed by a processor, it implements the high- and low-frequency composite fatigue life prediction method considering the amplitude-frequency ratio as described in Embodiment 1.

[0050] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for predicting high- and low-cycle combined fatigue life considering amplitude-frequency ratio, characterized in that, Includes the following steps: S1. Convert the high-cycle fatigue load into a stress ratio using the Gerber mean stress correction method. The equivalent stress under; S2. Fit the high-cycle fatigue life and low-cycle fatigue life using a power-law form. S3. Based on the high- and low-cycle combined fatigue load spectrum, construct a weighting function that reflects the influence of the high- and low-cycle stress amplitude ratio on cumulative damage. ; S4. Based on the high-low cycle composite fatigue load spectrum, construct a strengthening function that reflects the influence of the high-low cycle stress amplitude ratio and the high-low cycle stress frequency ratio on cumulative damage. ; S5. Construct a high-low cycle combined fatigue life prediction model and substitute the high-low cycle combined fatigue test data into the model parameters. S6. Calculate the number of load blocks when the cumulative damage reaches the critical damage level, and complete the fatigue life prediction.

2. The method for predicting high- and low-frequency composite fatigue life considering amplitude-frequency ratio according to claim 1, characterized in that, The step S1, which uses the Gerber mean stress correction method to convert high-cycle fatigue loads, includes the following steps: S101, First, convert the high-cycle fatigue load to a stress ratio. Equivalent stress The calculation formula is: （1）； in, This represents the stress amplitude under high-cycle fatigue load. This represents the average stress under high-cycle fatigue loads. The tensile strength of the welding material for the rotating wheel; S102, After solving the problem, the stress ratio can be obtained by inversely solving the Gerber formula. Equivalent stress The expression is: （2）； in, Stress ratio The mean of the equivalent stress, and ; Indicates to Solve the problem.

3. The method for predicting high- and low-cycle combined fatigue life considering amplitude-frequency ratio according to claim 1, characterized in that, In step S2, the power-law fitting expression for low-cycle fatigue life is: (3)； in, This represents the stress amplitude under low-cycle fatigue loads. These are the fitting parameters for the model.

4. The method for predicting high- and low-frequency composite fatigue life considering amplitude-frequency ratio according to claim 1, characterized in that, In step S2, the power-law fitting expression for high-cycle fatigue life is: (4)； in, This represents the stress amplitude under high-cycle fatigue load. These are the fitting parameters for the model.

5. The method for predicting high- and low-frequency composite fatigue life considering amplitude-frequency ratio according to claim 1, characterized in that, The weighting function constructed in step S3, which reflects the influence of the high-cycle and low-cycle stress amplitude ratio on cumulative damage, The expression is: (5)； in, This represents the maximum stress under combined high- and low-cycle fatigue loads. This represents the average stress under combined high- and low-cycle fatigue loads.

6. The method for predicting high- and low-cycle combined fatigue life considering amplitude-frequency ratio according to claim 5, characterized in that, The Reflecting the ratio of high- and low-cycle stress amplitudes, under the same maximum stress, an increase in the ratio of high- and low-cycle stress amplitudes indicates an increase in average stress. Decrease, making Increase; decrease the ratio of high- and low-cycle stress amplitudes, then the average stress Increase, making Decrease.

7. The method for predicting high- and low-cycle combined fatigue life considering amplitude-frequency ratio according to claim 1, characterized in that, In step S4, the constructed reinforcement function reflects the influence of the high-low cycle stress amplitude ratio and the high-low cycle stress frequency ratio on cumulative damage. The expression is: (6)； in, This represents the threshold for low-load enhancement.

8. The method for predicting high- and low-cycle composite fatigue life considering amplitude-frequency ratio according to claim 7, characterized in that, The low-load strengthening threshold This was determined by analyzing high- and low-cycle combined fatigue test data.

9. The method for predicting high- and low-cycle composite fatigue life considering amplitude-frequency ratio according to claim 1, characterized in that, In step S5, the formula for calculating the cumulative damage of a single load block in the high-low cycle combined fatigue life prediction model is as follows: (7)； in, It represents the ratio of high-frequency to low-frequency stress.

10. The method for predicting high- and low-frequency composite fatigue life considering amplitude-frequency ratio according to claim 1, characterized in that, In step S6, the formula for calculating the number of load blocks when the accumulated damage reaches the critical damage is as follows: (8)； in, This represents the number of load blocks.

11. A high- and low-frequency composite fatigue life prediction system considering amplitude-to-frequency ratio, characterized in that, The method for predicting high- and low-cycle combined fatigue life considering amplitude-frequency ratio as described in any one of claims 1 to 10 includes: The equivalent stress conversion module is used to convert high-cycle fatigue loads into stress ratios using the Gerber mean stress correction method. The equivalent stress under; The life fitting module is used to fit high-cycle fatigue life and low-cycle fatigue life in a unified power-law form. The weighting function construction module is used to construct a weighting function that reflects the influence of the high-low cycle stress amplitude ratio on cumulative damage based on the high-low cycle combined fatigue load spectrum. ; The reinforcement function construction module is used to construct reinforcement functions based on the high-low cycle combined fatigue load spectrum, reflecting the influence of the high-low cycle stress amplitude ratio and the high-low cycle stress frequency ratio on cumulative damage. ; The model building and parameter fitting module is used to build a high-low cycle combined fatigue life prediction model and fit the model parameters by substituting high-low cycle combined fatigue test data. The life calculation module is used to calculate the number of load blocks when the cumulative damage reaches the critical damage level, and to complete the fatigue life prediction.

12. An electronic device for predicting the combined fatigue life of high and low frequency cycles considering the amplitude-to-frequency ratio, characterized in that, The method includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the high-low cycle composite fatigue life prediction method considering the amplitude-frequency ratio as described in any one of claims 1 to 10.

13. A high-frequency composite fatigue life prediction storage medium considering amplitude-frequency ratio, characterized in that, The storage medium is a computer-readable storage medium, and a computer program is stored on the computer-readable storage medium. When the computer program is executed by a processor, it implements the high-low cycle composite fatigue life prediction method considering the amplitude-frequency ratio as described in any one of claims 1 to 10.

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