Time domain fatigue analysis method for marine high-temperature and high-pressure container

Abstract

The invention relates to the technical field of high-temperature and high-pressure containers, and discloses a time-domain fatigue analysis method for a marine high-temperature and high-pressure container. S1, establishing a finite element model of the marine high-temperature and high-pressure container; s2, calculating internal pressure and thermal load borne by the marine high-temperature and high-pressure container; s3, calculating the wave load borne by the marine high-temperature and high-pressure container; s4, selecting a fatigue damage evaluation position; s5, calculating a hot-pressing stress time history; and S6, calculating a wave stress time history. By adopting the time domain fatigue analysis method combining the internal pressure, the thermal load and the wave load, the fatigue behaviors of the marine high-temperature and high-pressure container under different working conditions can be comprehensively evaluated. Compared with a single load analysis method in the prior art, the method has the advantages that the complex stress state of the container in the actual working environment can be reflected more accurately by superposing stress time history of various loads, and the defect that load coupling effect is neglected in traditional analysis is effectively overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature and high-pressure vessels, and in particular to a time-domain fatigue analysis method for a marine high-temperature and high-pressure vessel. Background Art

[0002] In the existing design and fatigue analysis of marine high-temperature and high-pressure vessels, traditional methods mostly rely on static analysis or single load action evaluation. These methods often ignore the interaction between multiple loads in actual working conditions, resulting in inaccurate fatigue life prediction. In actual use, the container faces the superposition of multiple complex loads such as internal pressure, thermal load and wave load. The analysis method under a single load cannot effectively simulate the actual stress state of the container in a multiple load environment.

[0003] Most fatigue analysis methods in the prior art focus on calculating stress under a single working condition, but for complex marine environments, especially the influence of wave loads, a simple average load processing method is usually used. This method ignores the dynamic characteristics of wave loads, such as the influence of wave period, wave direction and other factors on container fatigue, resulting in an oversimplified fatigue damage assessment, which is difficult to accurately reflect the actual fatigue damage degree of the container.

[0004] In traditional fatigue damage calculation, a simple linear accumulation method is often used, assuming that all stress amplitudes contribute equally to damage. This method fails to consider the differences in stress amplitudes and their different effects on fatigue life, resulting in a rough assessment of container fatigue damage and an inability to provide accurate fatigue life predictions.

[0005] Traditional internal pressure and thermal load analysis methods also have shortcomings. In some cases, these analysis methods do not fully consider the impact of temperature on the mechanical properties of materials, especially under high temperature and high pressure conditions, where parameters such as the elastic modulus and thermal expansion coefficient of the material will change significantly with temperature changes. Existing technologies often ignore this dynamic change, resulting in inaccurate fatigue assessment of containers under extreme working conditions. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a time-domain fatigue analysis method for ship-borne high-temperature and high-pressure vessels, which solves the problem of inaccurate fatigue damage prediction of ship-borne high-temperature and high-pressure vessels under multiple loads, especially under the coupling of wave loads and thermal loads.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: A time domain fatigue analysis method for a marine high-temperature and high-pressure vessel comprises the following steps; S1. Establish the finite element model of marine high temperature and high pressure vessels; S2. Calculate the internal pressure and thermal load of marine high temperature and high pressure vessels; S3. Calculate the wave loads on marine high temperature and high pressure vessels; S4. Select the fatigue damage assessment location; S5. Calculate the time history of thermal compression stress; S6. Calculate the time history of wave stress; S7, time history of superimposed wave stress and thermal pressure stress; S8. Calculate stress amplitude using rain flow counting method; S9. Calculate the cumulative fatigue damage of high-temperature and high-pressure marine vessels.

[0008] Preferably, the model in step S1 includes the geometric shape, material properties, boundary conditions and load area of ​​the container.

[0009] Preferably, the internal pressure calculation in step S2 is performed by coupling calculation of temperature field and pressure field based on the working conditions and material properties of the container.

[0010] Preferably, when calculating the wave load in step S3, the three-dimensional potential flow software ANSYSAQWA is used to perform hydrodynamic calculations on the exported model file, determine the frequency and wave direction of the design wave, and calculate the wave energy spectral density function.

[0011] Preferably, the fatigue damage assessment position in step S4 is selected based on a stress distribution diagram of a finite element analysis, and an area with large stress fluctuations and prone to fatigue damage is selected.

[0012] Preferably, when the stress time histories of the wave load and the thermal load in step S7 are superimposed, the initial phase of the regular wave is adjusted to more accurately reflect the coupling effect of the multiple loads.

[0013] Preferably, the rain flow counting method in step S8 is used to identify peaks and valleys in the stress cycle and accurately calculate the stress amplitude.

[0014] Preferably, the fatigue damage calculation in step S9 is performed by using the Miner damage accumulation criterion, and is cumulatively calculated based on the number of cycles under the stress amplitude and the fatigue life of the material.

[0015] Preferably, when calculating the thermal pressure stress time history and the wave stress time history in step S5 and step S6, the stress time history is calculated respectively by finite element method.

[0016] Preferably, in the fatigue cumulative damage calculation process in step S9, a multi-phase wave load superposition method is adopted, regular waves with different initial phases are selected and combined with thermal-compression coupling loads to generate multiple stress time histories.

[0017] The present invention provides a time domain fatigue analysis method for a high temperature and high pressure vessel for a ship. It has the following beneficial effects: 1. The present invention adopts a time-domain fatigue analysis method that combines internal pressure, thermal load and wave load, which can comprehensively evaluate the fatigue behavior of marine high-temperature and high-pressure vessels under different working conditions. By superimposing the stress time history of multiple loads, compared with the single load analysis method in the prior art, the present invention can more accurately reflect the complex stress state of the container in the actual working environment, effectively solving the deficiency of traditional analysis that ignores the coupling effect of loads.

[0018] 2. The present invention calculates stress amplitude by applying the rainflow counting method, identifies and extracts key stress cycles from the stress time history. This method makes the fatigue damage assessment of the container more accurate. Compared with the traditional fatigue prediction method based on static stress analysis, the rainflow counting method can better handle the influence of dynamic and irregular loads, overcoming the problem of inaccurate prediction under dynamic loads of the old method.

[0019] 3. The present invention uses the mining damage accumulation criterion in fatigue damage calculation and combines the material stress-life curve to perform accurate damage calculation. This method makes fatigue damage assessment more scientific and systematic. Compared with the simple linear accumulation method in the prior art, the present invention can effectively consider the role of different stress amplitudes and solve the limitations of the traditional method that only considers the maximum stress value.

[0020] 4. The present invention adopts a temperature-dependent material model to model and analyze the material properties under high temperature and high pressure working environment. Through this method, the performance of the container can be reasonably predicted under high temperature environment. Compared with the technical solution in the traditional method that does not fully consider the impact of temperature changes on material properties, the present invention can more accurately simulate the high temperature behavior of the material and solve the technical problem of inaccurate analysis under high temperature conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the method flow of the present invention; Figure 2 It is a schematic diagram of a finite element model of a marine high-temperature and high-pressure container of the present invention; Figure 3 It is a schematic diagram of the maximum value of the thermal pressure load stress of the present invention; Figure 4 This is the hydrodynamic model diagram of the hull structure of this ship; Figure 5 This is a schematic diagram of the stress-time history curve of the verification point of this invention; Figure 6 It is a schematic diagram of the fatigue cumulative damage range results of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Please refer to the attached Figure 1-Figure 6 , an embodiment of the present invention provides a time domain fatigue analysis method for a marine high temperature and high pressure vessel, comprising the following steps; S1. Establish the finite element model of marine high temperature and high pressure vessels; Specifically, in this embodiment, the model in step S1 needs to accurately reflect the geometric structure, material properties and boundary conditions of the container, while ensuring that it can effectively bear the subsequent internal pressure, thermal load and wave load analysis.

[0024] The finite element modeling stage uses a three-dimensional solid modeling method to ensure that the model can truly reflect the complex structure of the container. In local areas, a refined grid division method can be used to improve the calculation accuracy. For example, due to the strong stress concentration effect in the weld area, the grid size needs to be appropriately reduced, while for areas far away from the load area, a larger grid size can be used to reduce the amount of calculation.

[0025] Specifically, in this embodiment, the performance of the container can be reasonably predicted in a high-temperature working environment. The influence of temperature on the mechanical properties of the material is taken into account during modeling. The elastic modulus of the material , Poisson's ratio , thermal expansion coefficient Important parameters such as elastic modulus usually change with temperature, and the material properties are dynamically adjusted by the change of temperature field. The change with temperature can be expressed as;

[0026] in: For temperature The elastic modulus under is the elastic modulus of the material at room temperature; is the temperature dependence coefficient.

[0027] In order to simulate the high temperature behavior of the material more accurately, the temperature-dependent nonlinear material model is used for finite element analysis. Specifically, the creep effect is simulated by the Norton creep equation, which is expressed as follows:

[0028] in: is the creep strain rate; is the creep constant; for stress; is the creep index; is the creep activation energy; is the gas constant; is the absolute temperature.

[0029] In terms of setting boundary conditions, the bottom or supporting part of the container is usually set as a fixed constraint to prevent excessive displacement of the container during the force application process. The elastic support boundary condition is adopted, that is, by introducing the spring stiffness To simulate the deformation of the supporting structure, the stiffness is calculated as follows;

[0030] in: is the elastic modulus of the supporting material; To support the contact area; is the effective length of the supporting structure.

[0031] In this example, a precise model of a high-temperature and high-pressure vessel for ships is established through detailed finite element modeling, combined with the temperature-related properties of the material, the influence of complex loads, and the setting of support boundary conditions. This model not only provides accurate basic data for subsequent fatigue analysis, but also can adapt to stress response and fatigue damage assessment under different working conditions.

[0032] S2. Calculate the internal pressure and thermal load of marine high temperature and high pressure vessels; Specifically, after the finite element model is established, the internal pressure and thermal load of the marine high-temperature and high-pressure container are calculated. The internal pressure and thermal load are the most important stress sources of the container in actual work. Correctly calculating the influence of these two is the premise to ensure the safe operation of the container and the accuracy of fatigue analysis.

[0033] In this embodiment, in a marine container, the internal pressure is usually generated by the fluid medium inside the container. The internal pressure value is estimated by considering the structural dimensions of the container and the pressure of the fluid medium, and the stress is calculated using the classic thin-walled cylinder internal pressure formula;

[0034] in: is the internal pressure, usually set according to the working conditions of the container; is the diameter of the container; is the wall thickness of the container.

[0035] The calculation of internal pressure can be coupled with the temperature field for analysis. Temperature changes not only affect the mechanical properties of the material, but also change the thermal expansion characteristics of the container wall. The temperature-pressure coupling method is used in the calculation, that is, the temperature field inside the container is calculated first, and then the parameters of the internal pressure calculation are adjusted according to the temperature field distribution. Specifically, the temperature field is usually calculated by numerical solution methods, and the finite element method can be used to solve the temperature field. Specifically, thermal stress can be expressed as;

[0036] in; for thermal stress; is the elastic modulus of the material; is the coefficient of thermal expansion; is the temperature difference.

[0037] Coefficient of thermal expansion of the material It will change with the increase of temperature. Therefore, in order to accurately describe the thermal stress, a temperature-dependent model is needed to calculate the thermal expansion coefficient and elastic modulus to ensure its accuracy under actual working conditions.

[0038] After the temperature and internal pressure coupling calculation is completed, the structural response of the container wall needs to be considered. Since the thermal expansion caused by the temperature difference will cause additional stress inside the container, it is necessary to perform a composite stress analysis combined with the internal pressure to finally obtain the stress distribution of the container.

[0039] By calculating the effects of internal pressure and thermal load, the stress conditions of the container in the working environment can be comprehensively evaluated. The calculation results provide essential data support for fatigue analysis in subsequent steps. By reasonably coupling the temperature field and the pressure field, this embodiment can accurately capture the thermal stress changes of the container in actual working conditions, providing a basis for fatigue damage prediction of the container.

[0040] S3. Calculate the wave loads on marine high temperature and high pressure vessels; Specifically, in this embodiment, it is first necessary to calculate the wave load through the hydrodynamic model based on the marine environment in which the container is located. The wave load is determined by factors such as the wave height, wavelength, and wave direction of the surface waves. These factors directly affect the hydrodynamic pressure on the container surface. The three-dimensional potential flow software ANSYSAQWA is used to perform hydrodynamic calculations on the exported model file to determine the frequency and wave direction of the design wave. In the hydrodynamic calculation, the frequency and wave direction of the design wave must first be determined. The model based on potential flow theory can be used to calculate the hydrodynamic pressure distribution. According to the principles of fluid dynamics, waves will generate pressure on the container surface during propagation, and the pressure can be calculated using the following formula;

[0041] in: is the density of seawater; is the acceleration due to gravity; is the effective wave height; is the wave angular frequency; For time; is the initial phase of the wave.

[0042] When the wave load is more complex or irregular, you can also consider using multiple wave spectra for simulation. The wave spectrum (JONSWAP spectrum or Pierson-Moskowitz spectrum) reflects the energy distribution of different wave frequencies. Different wave spectra can more accurately simulate the impact of actual sea conditions on containers. The wave spectrum can calculate the stress responses of multiple different waves and superimpose them to simulate the stress conditions of the container under actual sea conditions.

[0043] The vibration of the container structure may affect the effect of waves, so it is very important to use modal analysis to consider the natural frequency of the container and its interaction with wave loads. Modal analysis can help identify the response characteristics of the container at different wave frequencies and effectively reduce errors.

[0044] Specifically, through the above-mentioned hydrodynamic analysis, the present invention can accurately calculate the wave load borne by the container under different wave conditions, and couple it with the finite element model of the container to obtain the dynamic stress effect of the wave load on the container.

[0045] S4. Select the fatigue damage assessment location; Specifically, ensure that detailed analysis is performed in the areas of the container that are most susceptible to fatigue damage, so as to obtain accurate fatigue life prediction. By accurately selecting areas with large stress fluctuations or high loading frequency, according to the calculation results of the finite element model, internal pressure and thermal load in the previous steps, and by analyzing the stress distribution of the container under different working conditions, the appropriate fatigue damage assessment location is selected.

[0046] The stress distribution diagram of the vessel under working pressure, thermal load and wave load is obtained through finite element analysis. The stress distribution diagram can help engineers identify which areas have the largest stress fluctuations. In this way, the location of the vessel fatigue damage assessment can be effectively determined.

[0047] In combination with the complex working conditions that may arise in actual engineering applications, by reasonably selecting the evaluation location, not only the accuracy of the container fatigue analysis is improved, but also basic data is provided for the subsequent fatigue life prediction, thereby ensuring that the marine high temperature and high pressure containers can operate stably and reliably under extreme working conditions.

[0048] S5. Calculate the time history of thermal compression stress; S6. Calculate the time history of wave stress; Specifically, in step S5 of this embodiment, the time history of thermal pressure stress of the container under the action of internal pressure and thermal load is calculated. The time history of thermal pressure stress reflects the periodic changes of thermal stress experienced by the container over time in actual operation.

[0049] In order to calculate the time history of thermal pressure stress, the temperature field inside the container must be considered first. When the container is working, it is subjected to the combined effects of high temperature and high pressure. The difference between the internal and external temperatures may cause thermal stress on the surface and inside of the container. The expansion effect caused by temperature changes will cause thermal stress in the container, and these thermal stresses will fluctuate periodically with temperature changes.

[0050] Specifically, in step S6, the stress time history of the container under the wave load is calculated. Like the thermal load, the impact of the wave load on the container is periodic, and the wave force is dynamic and changes over time. Therefore, accurately calculating the stress time history under the wave load is the key to the fatigue analysis of the container. Specifically, in step S6, the hydrodynamic pressure under the wave load is applied to the container surface of the finite element model through the wave load data obtained in step S3, and the stress response of the container under the wave action can be obtained through finite element analysis. The wave load changes with time, so the stress state of the container will also fluctuate with time.

[0051] Specifically, the wave load transfer functions (RAOs) of wave height and wave direction are used to determine the wave direction and period in the design wave parameters. Based on the short-term sea condition information, the wave spectrum (PM spectrum, JONSWAP spectrum) suitable for the hull structure design sea area is selected, and the wave energy spectrum density function is calculated. After obtaining the wave load transfer function and calculating the wave energy spectral density function, the spectrum analysis method can be used to obtain the response spectrum of the platform wave load in irregular waves.

[0052]

[0053] Calculate the maximum possible value of the load response under short-term sea conditions ;

[0054] in; is the 0th order moment of the response spectrum, ; is the number of cycles within the duration, ; D is the duration.

[0055] is the average zero-crossing period of the response, .

[0056] Design wave system amplitude It is determined as follows: the maximum value of the response in all short-term sea conditions Divide by the maximum value of the amplitude-frequency response of the load parameter ,Right now;

[0057] in: is the load factor.

[0058] is the stress time history under thermal-compression coupling load, is the stress time history under wave load. In order to consider the influence of multi-phase waves, the phase difference is defined as , and introduce it into the stress calculation formula. The total stress-time history under these combinations can be expressed as

[0059] in; Indicates The total stress time history under the combination of Indicates The phase difference is n, and multiple different combined stress time histories can be generated in this way. The stress time history can more accurately reflect the multiple loads on the high temperature and high pressure vessel of the ship, especially the complex coupling of thermal load and wave load.

[0060] S7, time history of superimposed wave stress and thermal pressure stress; Specifically, the coupling of different loads in this embodiment will lead to an increase in the local stress peak of the container, and may even cause fatigue damage more serious than that caused by a single load. Accurately superimposing the time history of wave stress and thermal pressure stress is the basis for fatigue damage analysis.

[0061] The superposition of the wave stress time history and the thermal pressure stress time history is based on the calculation results of steps S5 and S6. The wave stress is a periodic stress caused by the hydrodynamic pressure, while the thermal pressure stress is a stress caused by the change of the temperature field. There may be a phase difference between the two in the time dimension. When performing stress superposition, the relative phase of the wave stress and the thermal pressure stress needs to be considered to ensure that the calculation results can truly reflect the effects of multiple loads.

[0062] Specifically, assuming that the wave stress time history is The time history of thermal stress is , the total stress time history after superposition It can be expressed as;

[0063] in: For time Total stress in the container at time t; is the time history of thermal compression stress; is the time history of wave stress; The wave load has a longer periodicity, while the thermal load may change more steadily. Therefore, the superposition of the two needs to take into account their respective periodic characteristics and adjust the superposition method according to the frequency of the wave load and the change period of the thermal pressure stress to ensure that the superposition result can truly reflect the stress fluctuation of the container under working conditions.

[0064] In the superposition process, in addition to direct linear superposition, weighted superposition of stress amplitudes can also be considered. Due to the different modes of action of thermal loads and wave loads, the impact on the container may have different amplitudes. The weights of each stress contribution are adjusted according to the actual load size. Weighted superposition can be expressed by the following formula;

[0065] in: and are the weight coefficients of wave stress and thermal pressure stress, respectively, which depend on the relative influence of the two on the container.

[0066] The weighted superposition method can flexibly adjust the impact of different stress sources on the container according to the actual working conditions, container structure and material properties, thereby obtaining a more accurate stress time history. This method is particularly effective for complex analysis that needs to consider different working conditions and load changes.

[0067] Specifically, by superimposing the time history of wave stress and thermal pressure stress, the comprehensive stress to which the marine high-temperature and high-pressure vessel is subjected in actual operation can be accurately reflected. This superposition process ensures the comprehensiveness and accuracy of fatigue damage assessment and provides a scientific basis for subsequent fatigue life prediction.

[0068] S8. Calculate stress amplitude using rain flow counting method; Specifically, in this embodiment, the obtained stress time history is processed by rain flow counting. As a commonly used stress cycle identification method, the rain flow counting method can effectively decompose the stress data in the time history into different stress cycles, identify the peak and valley values ​​of stress, and thus obtain the amplitude of each stress cycle. The rain flow counting method identifies the change of stress amplitude through continuous stress fluctuations.

[0069] In the stress time history, we first identify a complete stress cycle starting from the maximum and minimum stress values. Then, based on the stress fluctuation trend, we gradually extract the amplitude of each stress cycle by judging the alternation of peak and valley values. In this way, we can ensure that all stress cycles are accurately identified and their amplitudes are calculated. The calculation formula of stress amplitude is in the following form;

[0070] in: is the amplitude of the stress cycle; is the maximum stress in the cycle; is the minimum stress in the cycle; The rainflow counting method can convert the stress time history data into a set of specific stress amplitudes by identifying multiple stress cycles. These amplitudes reflect the stress fluctuations of the container during operation.

[0071] Identify the peaks and valleys from the stress time history, and obtain the stress amplitude by calculating the difference between adjacent peaks and valleys. ;

[0072] Represents stress difference; Indicates The peak value of stress in a cycle; Indicates The valley value of stress in a cycle; Next, the closure condition of the rainflow counting method is used to determine whether the stress cycle is complete. Once a complete cycle is identified, the stress amplitude and number of the cycle are recorded. In this way, the entire stress time history is decomposed into multiple independent stress cycles.

[0073] By calculating the stress amplitude by the rain flow counting method, this embodiment can effectively extract key information from the complex stress time history. The stress amplitude is an important basis for fatigue damage assessment. Through this method, the complex stress changes of the container under working conditions can be converted into data that is easy to analyze, providing reliable data support for subsequent fatigue damage calculations.

[0074] S9. Calculate the cumulative fatigue damage of high-temperature and high-pressure marine vessels.

[0075] Specifically, in this embodiment, the stress amplitude data is used to calculate the fatigue cumulative damage of the marine high-temperature and high-pressure container. This step accumulates the fatigue damage under each stress amplitude and finally obtains the overall fatigue damage of the container under specific working conditions.

[0076] The calculation of fatigue damage is based on Miner's damage accumulation criterion. Fatigue damage accumulates gradually, and the contribution of stress cycles to damage can be calculated independently. Specifically, damage accumulation is based on the number of cycles under the stress amplitude and the fatigue life of the material.

[0077] Specifically, the basic formula of Miner's damage accumulation criterion is:

[0078] in: For cumulative damage; is the stress amplitude The number of cycles under is the fatigue life of the material under this stress amplitude.

[0079] Through this formula, the contribution of different stress amplitudes to fatigue damage is weighted to obtain the overall damage value. When calculating damage, it is necessary to consider the fatigue life under each stress amplitude, which is usually obtained through experimental data or SN curve based on the material. The SN curve is a standard method for describing the fatigue life of materials under different stress amplitudes. By looking up a table or interpolation method, the fatigue life corresponding to each stress amplitude can be obtained. .

[0080] A more accurate material model is used to consider the nonlinear behavior of the material, especially in high temperature and high pressure environments, where the fatigue properties of the material may change with changes in temperature and pressure. In order to improve the calculation accuracy, a temperature-dependent fatigue life prediction model can be used to incorporate the effect of temperature on the fatigue properties of the material into the damage calculation.

[0081] Under high temperature conditions, the fatigue life of materials is usually shortened. Therefore, when the temperature is high, the fatigue life of the material needs to be adjusted by the temperature correction coefficient. At this time, the SN curve needs to be corrected according to the actual temperature to obtain new fatigue life data, which affects the calculation of cumulative damage.

[0082] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A time domain fatigue analysis method for a marine high temperature and high pressure vessel, characterized in that: The steps include: S1. Establish the finite element model of marine high temperature and high pressure vessels; S2. Calculate the internal pressure and thermal load of marine high temperature and high pressure vessels; S3. Calculate the wave loads on marine high temperature and high pressure vessels; S4. Select the fatigue damage assessment location; S5. Calculate the time history of thermal compression stress; S6. Calculate the time history of wave stress; S7, time history of superimposed wave stress and thermal pressure stress; S8. Calculate stress amplitude using rain flow counting method; S9. Calculate the cumulative fatigue damage of high-temperature and high-pressure marine vessels.

2. The time domain fatigue analysis method for a marine high temperature and high pressure vessel according to claim 1 is characterized in that: The model in step S1 includes the geometric shape, material properties, boundary conditions and load area of ​​the container.

3. The time domain fatigue analysis method for a marine high temperature and high pressure vessel according to claim 1 is characterized in that: The internal pressure calculation in step S2 is a coupled calculation of the temperature field and the pressure field based on the working conditions and material properties of the container.

4. The time domain fatigue analysis method for a marine high temperature and high pressure vessel according to claim 1 is characterized in that: When calculating the wave load in step S3, the three-dimensional potential flow software ANSYSAQWA is used to perform hydrodynamic calculations on the exported model file, determine the frequency and wave direction of the design wave, and calculate the wave energy spectrum density function.

5. The time domain fatigue analysis method for a marine high temperature and high pressure vessel according to claim 1 is characterized in that: The selection of the fatigue damage assessment position in step S4 is based on the stress distribution diagram of the finite element analysis, and the area with large stress fluctuation and prone to fatigue damage is selected.

6. The time domain fatigue analysis method for a marine high temperature and high pressure vessel according to claim 1 is characterized in that: When the stress time histories of the wave load and the thermal load in step S7 are superimposed, the initial phase of the regular wave is adjusted to more accurately reflect the coupling effect of multiple loads.

7. The time domain fatigue analysis method for a marine high temperature and high pressure vessel according to claim 1 is characterized in that: The rain flow counting method in step S8 is used to identify peaks and valleys in the stress cycle and accurately calculate the stress amplitude.

8. The time domain fatigue analysis method for a marine high temperature and high pressure vessel according to claim 1, characterized in that: The fatigue damage calculation in step S9 is performed by using the Miner damage accumulation criterion, based on the number of cycles under the stress amplitude and the fatigue life of the material.

9. The time domain fatigue analysis method for a marine high temperature and high pressure vessel according to claim 1, characterized in that: When calculating the thermal pressure stress time history and the wave stress time history in step S5 and step S6, the stress time history is calculated by finite element method respectively.

10. The time domain fatigue analysis method for a marine high temperature and high pressure vessel according to claim 1, characterized in that: In the fatigue cumulative damage calculation process in step S9, a multi-phase wave load superposition method is adopted to select regular waves with different initial phases and combine them with thermal-pressure coupling loads to generate multiple stress time histories.

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