Method, device and product for comprehensive safety assessment of vertical cylindrical high-temperature molten salt storage tank

Abstract

This application discloses a comprehensive safety assessment method, equipment, and product for a vertical cylindrical high-temperature molten salt storage tank, relating to the field of industrial simulation. The method includes conducting uniaxial tensile and strain-controlled fatigue tests on a target finite element model at multiple test temperatures to obtain constitutive parameters and strain-life curves of the target material at these temperatures, which are then configured onto the target finite element model. The target material is the material of the vertical cylindrical high-temperature molten salt storage tank. The method also involves setting the operating condition spectrum of the vertical cylindrical high-temperature molten salt storage tank and load combinations under different operating conditions, generating a load spectrum based on the operating condition spectrum and load combinations under different operating conditions, applying the load spectrum to the target finite element model to calculate a stress distribution cloud map, and conducting a comprehensive safety assessment of the vertical cylindrical high-temperature molten salt storage tank based on the stress distribution cloud map, evaluation methods for different failure modes, and strain-life curves. This application achieves a comprehensive assessment of the vertical cylindrical high-temperature molten salt storage tank.

Description

Technical Field

[0001] This application relates to the field of industrial simulation, and in particular to a comprehensive safety assessment method, equipment and product for a vertical cylindrical high-temperature molten salt storage tank. Background Technology

[0002] Molten salt storage tanks are the core equipment of molten salt thermal energy storage systems, and are generally divided into cold tanks and hot tanks. Among them, the operating temperature of hot tanks is usually as high as 400℃-565℃, and the liquid level and temperature of the tank will change periodically during the process of heat absorption and energy storage and heat release and power generation. This high-temperature and variable load operating environment poses severe mechanical challenges to the tank structure.

[0003] Existing tank design standards (such as API 650) are mostly for ambient or low-temperature oil tanks, lacking systematic evaluation methods for complex failure modes (especially creep-fatigue interaction, ratchet effect, etc.) of high-temperature molten salt tanks. Moreover, they often only consider static strength, making it difficult to accurately predict structural safety throughout the entire life cycle. Summary of the Invention

[0004] The purpose of this application is to provide a comprehensive safety assessment method, equipment, and product for vertical cylindrical high-temperature molten salt storage tanks, which can achieve a comprehensive assessment of vertical cylindrical high-temperature molten salt storage tanks.

[0005] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a comprehensive safety assessment method for a vertical cylindrical high-temperature molten salt storage tank, including: Construct the target finite element model of a vertical cylindrical high-temperature molten salt storage tank; Multiple test temperatures are selected from the actual service temperature of the vertical cylindrical high-temperature molten salt storage tank. Based on the target finite element model, uniaxial tensile tests and strain-controlled fatigue tests are carried out on the target material at the multiple test temperatures to obtain the constitutive parameters and strain-life curves of the target material at the multiple test temperatures and configure them to the target finite element model. The target material is the material of the vertical cylindrical high-temperature molten salt storage tank. The operating condition spectrum and load combinations under different operating conditions of the vertical cylindrical high-temperature molten salt storage tank are set, and a load spectrum is generated based on the operating condition spectrum and the load combinations under different operating conditions. The load spectrum is applied to the target finite element model to generate a stress distribution cloud map; Based on the stress distribution cloud map, the evaluation methods for different failure modes, and the strain-life curve, a comprehensive safety assessment is conducted on the vertical cylindrical high-temperature molten salt storage tank. The comprehensive safety assessment includes assessment of plastic collapse and local failure, buckling stability, stability and ratchet effect, fatigue failure, creep failure, and fatigue and creep interaction failure.

[0006] In a second aspect, this application provides a computer device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the comprehensive safety assessment method for the vertical cylindrical high-temperature molten salt storage tank described in any one of the above-mentioned methods.

[0007] Thirdly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the comprehensive safety assessment method for the vertical cylindrical high-temperature molten salt storage tank described above.

[0008] Fourthly, this application provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the comprehensive safety assessment method for the vertical cylindrical high-temperature molten salt storage tank described above.

[0009] According to the specific embodiments provided in this application, the following technical effects are disclosed: This application provides a comprehensive safety assessment method, equipment, and product for vertical cylindrical high-temperature molten salt storage tanks. The method employs simulation to evaluate the tanks. First, a target finite element model of the tank is constructed, and material constitutive parameters and strain-life curves at multiple different temperatures are calculated to facilitate subsequent comprehensive safety assessment calculations. Furthermore, the load spectrum construction considers various load combinations under different operating conditions, rather than using a constant load combination throughout the entire lifespan, thus better reflecting actual conditions and improving the accuracy of the subsequent comprehensive safety assessment. Finally, the comprehensive safety assessment includes multiple evaluations such as plastic collapse and local failure assessment, buckling stability assessment, stability and ratchet effect assessment, fatigue failure assessment, creep failure assessment, and fatigue and creep interactive failure assessment. This considers various complex failure modes of vertical cylindrical high-temperature molten salt storage tanks, thereby enabling a comprehensive evaluation of the tanks. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a flowchart illustrating the comprehensive safety assessment method for vertical cylindrical high-temperature molten salt storage tanks in this invention. Figure 2 This is the target finite element model of the vertical cylindrical high-temperature molten salt storage tank in this embodiment of the invention; Figure 3 This is a diagram showing the stress intensity results of the large fillet weld mesh in an embodiment of the present invention; Figure 4 This is a stress intensity cloud diagram of the seismic condition in an embodiment of the present invention; Figure 5 This is a model diagram of the shell and support beam in an embodiment of the present invention; Figure 6 This is a first-order buckling mode diagram of the tank top and the supporting beam in an embodiment of the present invention; Figure 7 This is a stress cloud diagram of the cyclic loading condition in an embodiment of the present invention; Figure 8 This is a fatigue design curve diagram of 304 steel in an embodiment of the present invention; Figure 9 For the strain-life (S) embodiment of the present invention SN (Line graph) Detailed Implementation

[0012] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0013] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0014] The comprehensive safety assessment method for vertical cylindrical high-temperature molten salt storage tanks provided in this application embodiment can be applied to computer equipment, which includes terminal equipment and servers. The terminal can be, but is not limited to, various desktop computers, laptops, smartphones, and tablets. The server can be a standalone server, a server cluster consisting of multiple servers, or a cloud server.

[0015] In the embodiments of this application, such as Figure 1 As shown, a comprehensive safety assessment method for a vertical cylindrical high-temperature molten salt storage tank is provided. This method is executed by computer equipment, specifically by a terminal or server alone, or by both a terminal and a server. In this embodiment, the method is described using a terminal device as an example, and includes the following steps S110 to S150.

[0016] Step S110: Construct the target finite element model of the vertical cylindrical high-temperature molten salt storage tank.

[0017] In this step, the vertical cylindrical high-temperature molten salt storage tank is simulated using finite element software to generate a target finite element model of the simulated vertical cylindrical high-temperature molten salt storage tank.

[0018] Preferably, step S110 specifically includes: establishing an initial finite element model of the vertical cylindrical high-temperature molten salt storage tank using 3D modeling software based on the design drawings of the vertical cylindrical high-temperature molten salt storage tank; obtaining the target finite element model by locally refining the mesh in the stress concentration area of ​​the initial finite element model; determining the final mesh density of the stress concentration area through mesh independence verification during the local mesh refinement process; the stress concentration area includes the large fillet weld and the tank top connection.

[0019] For example, the geometric model of the cold / hot molten salt storage tank and its foundation can be obtained using 3D modeling software, including the initial finite element model of the vertical cylindrical high-temperature molten salt storage tank, as referenced. Figure 2 This is the initial finite element model of a vertical cylindrical high-temperature molten salt storage tank. It should be noted that during the modeling process, for structures with symmetry, a 1 / 2 model can be used and symmetry constraints can be applied to improve computational efficiency. That is, the initial finite element model is only half of the structure of the vertical cylindrical high-temperature molten salt storage tank.

[0020] To improve the simulation accuracy of vertical cylindrical high-temperature molten salt storage tanks and eliminate the influence of mesh density on the calculation results, the mesh of the stress concentration region in the initial finite element model is locally refined (the mesh generation can use Solid185 solid elements), and the final mesh density of the stress concentration region is determined by mesh independence verification.

[0021] The specific operation is as follows: set different numbers of mesh layers in the thickness direction of the stress concentration region, and calculate the maximum stress intensity under the reference operating conditions; when the maximum stress intensity tends to stabilize as the number of mesh layers increases, determine the final mesh division scheme.

[0022] For example, 3, 4, 6, 8, and 10 mesh layers are respectively set in the thickness direction of the large fillet weld, and 1 and 3 mesh layers are set in the thickness direction of the tank wall. (Refer to...) Figure 3 The comparison results show that when the number of mesh layers at the large fillet weld exceeds 8, the maximum stress intensity tends to stabilize (approximately 112 MPa). Therefore, it is determined that 8 mesh layers should be divided in the thickness direction of the large fillet weld. Meanwhile, the maximum stress intensity at the tank wall is almost unaffected by the number of mesh layers, so 3 mesh layers can be divided in the thickness direction at the connection between the tank wall and the tank top, and 1 mesh layer can be divided in the thickness direction of the remaining tank wall areas.

[0023] Step S120: Select multiple test temperatures from the actual service temperature of the vertical cylindrical high-temperature molten salt storage tank. Based on the target finite element model, conduct uniaxial tensile tests and strain-controlled fatigue tests on the target material at the multiple test temperatures. Simultaneously, consult a material handbook to obtain the constitutive parameters and strain-life of the target material at the multiple test temperatures. SN The stress-strain curves and isochronous stress-strain curves are assigned to the target finite element model. The target material is the material of a vertical cylindrical high-temperature molten salt storage tank.

[0024] For example, the target material can be 347H stainless steel, and 4-5 temperatures can be selected as test temperatures based on the actual service temperature range of the storage tank. Constitutive parameters can include elastic modulus, Poisson's ratio, Young's modulus, coefficient of thermal expansion, thermal conductivity, and specific heat capacity, etc. The actual service temperature of a vertical cylindrical high-temperature molten salt storage tank is typically from 25℃ to 600℃. After obtaining the constitutive parameters of the target material at different temperatures, a material constitutive model can be constructed in finite element software, thereby configuring the material constitutive parameters to the target finite element model.

[0025] For example, some constitutive parameters (Young's modulus) of 347H stainless steel at different temperatures. E Coefficient of thermal expansion α T Thermal conductivity l As shown in Table 1.

[0026] Table 1. Partial constitutive parameters of 347H stainless steel at different temperatures.

[0027] Step S130: Set the operating condition spectrum of the vertical cylindrical high-temperature molten salt storage tank and the load combination under different operating conditions, and generate the load spectrum based on the operating condition spectrum and the load combination under different operating conditions.

[0028] In this step, it is necessary to extract and construct a combined transient and service fatigue load spectrum that fully considers various safety factors such as tank self-weight, tank top live load, hydraulic pressure, wind load, seismic load, snow load, and settlement, based on local climate and geological conditions and the actual operating conditions of the molten salt thermal storage system.

[0029] For example, the loads of the vertical cylindrical high-temperature molten salt storage tank are determined based on the peak-shaving operation characteristics and actual operating conditions of the thermal power unit, including constant load, live load, environmental load, and abnormal load.

[0030] Constant loads: self-weight, design internal pressure, and hydrostatic pressure of the liquid column.

[0031] Live load: tank top live load, snow load.

[0032] Environmental loads: wind loads and seismic loads (applied in the forward or reverse direction).

[0033] Abnormal load: Non-uniform settlement of the foundation.

[0034] For example, the operating condition spectrum includes the operating conditions of the vertical cylindrical high-temperature molten salt storage tank at various time points during its life cycle. The operating conditions are divided into normal operating conditions, seismic operating conditions, and settlement operating conditions. The load combination under normal operating conditions includes self-weight, design internal pressure, and hydrostatic pressure of the liquid column. The load combination under seismic operating conditions includes self-weight, hydrostatic pressure of the liquid column, seismic load, part of the snow load, and part of the design internal pressure. The load combination under settlement operating conditions includes self-weight, hydrostatic pressure of the liquid column, design internal pressure, and non-uniform settlement displacement of the foundation.

[0035] The load spectrum includes the load values ​​of the vertical cylindrical high-temperature molten salt storage tank at various time points throughout its life cycle.

[0036] The load spectrum is generated based on the operating condition spectrum and load combinations under different operating conditions. Specifically, it includes: based on the service status changes of the vertical cylindrical high-temperature molten salt storage tank, the load combination of each time node in the parametric operating condition spectrum is used to generate the load spectrum. The service status changes are an alternating cycle of salt inlet state and static state.

[0037] For example, for any time point in the load spectrum, the operating conditions at that time point are first determined to determine the corresponding load combination, and then the service status at that time point is determined to determine the specific values ​​of each load.

[0038] Step S140: Load the load spectrum onto the target finite element model to generate a stress distribution cloud map.

[0039] The load spectrum can be automatically loaded using APDL automated analysis software.

[0040] Specifically, the APDL automated analysis software used in this step achieves automated analysis through the following steps. The software is based on the Parametric Design Language (APDL), and the specific process is as follows: The software has a built-in dedicated data structure that automatically imports the load spectrum data generated in step S130 and material constitutive parameters (such as Young's modulus, coefficient of thermal expansion, etc.) at different temperatures through read commands (such as VREAD), mapping them into internal arrays. The software constructs a time-step-based main loop structure to traverse the load spectrum and uses a built-in logic algorithm to identify the working condition type: if it is determined to be a normal working condition, it automatically calls a subroutine to apply self-weight, design internal pressure, and hydrostatic pressure of the liquid column; if it is a seismic working condition, it superimposes the seismic acceleration vector on the foundation load, adjusts the internal pressure coefficient, and applies part of the snow load; if it is a settlement working condition, it applies non-uniform settlement displacement constraints to the foundation nodes. The software automatically creates a contact pair between the foundation and the tank bottom based on the characteristics of the tank bottom and defines the friction coefficient to simulate the foundation contact friction boundary conditions. After configuring each load step, the system automatically executes the solver command (SOLVE) to perform nonlinear solutions, and uses extraction commands (such as GET) to obtain key node data. It integrates and generates a continuous stress distribution cloud map, and supports structured storage and visualization output of the data, realizing full automation from data import to result generation.

[0041] Step S150: Based on the stress distribution cloud map, evaluation methods for different failure modes, and strain-life curves, a comprehensive safety assessment is conducted on the vertical cylindrical high-temperature molten salt storage tank. The comprehensive safety assessment includes assessment of plastic collapse and local failure, buckling stability, stability and ratchet effect, fatigue failure, creep failure, and fatigue and creep interaction failure.

[0042] Specifically, this step employs different assessment methods for different failure modes (plastic collapse and local failure, buckling stability, stability and ratcheting effect, fatigue failure, creep failure, and fatigue and creep interaction).

[0043] This step aims to establish a comprehensive safety assessment system covering static strength, stability, and the entire life cycle. This system includes the following graded assessment modules: a module for checking plastic collapse and local failure based on the ultimate load criterion; a module for assessing eigenvalues ​​and nonlinear buckling stability considering initial defects; a module for assessing elastic stability and inelastic ratchet effect under high-temperature cyclic conditions; and a module for assessing creep, fatigue, and creep-fatigue interactive failure based on the linear cumulative damage theory.

[0044] To address the complex stress characteristics and transients of vertical cylindrical high-temperature molten salt storage tanks throughout their service life, a comprehensive safety assessment method and process covering static strength, plastic collapse, local failure, stability, creep, fatigue, and creep-fatigue was established.

[0045] Plastic collapse and local failure assessment includes: Based on the stress distribution contour plot, determine the analysis path of the first target area in the target finite element model and perform stress linearization, decouple the total stress in the first target area into membrane stress, bending stress, and secondary stress; the first target area includes geometric discontinuity areas and smooth areas, the membrane stress in the geometric discontinuity area is the primary local membrane stress, and the membrane stress in the smooth area is the primary general membrane stress; judge whether the primary general membrane stress is less than the allowable stress; judge whether the primary local membrane stress is less than 1.5 times the allowable stress; judge whether the sum of the primary local membrane stress and the bending stress is less than 1.5 times the allowable stress; judge whether the sum of the primary local membrane stress, the bending stress, and the secondary stress is less than 3 times the allowable stress. Among them, the primary general membrane stress P m and the primary local membrane stress P L are obtained in exactly the same way and calculated in the same manner, and the only difference lies in the definition of the stress linearization path; the analysis path of the primary local membrane stress is selected in the geometric discontinuity area (welds, chamfers, etc.); the analysis path of the primary general membrane stress is selected in the smooth area (especially the smooth area far from the geometric discontinuity area), such as the tank wall of the tank body. The secondary stress is caused by deformation coordination or constraints and is the stress generated to meet the geometric continuity requirements.

[0046] Among them, the first target area is the area prone to plastic collapse and local failure, such as large fillet welds (belonging to geometric discontinuity areas), liquid level fluctuation areas (the tank wall within the liquid level fluctuation height range, belonging to smooth areas), etc.

[0047] Specifically, the plastic collapse and local failure assessment is based on the static analysis method, uses commands such as PATH / PRSECT to automatically define the analysis path of the first target area (such as large fillet welds, liquid level fluctuation areas) and perform stress linearization, and decouple the total stress into membrane stress, bending stress P b and secondary stress Q . The membrane stress is divided into primary general membrane stress P m and primary local membrane stress P L . The following criteria are used for checking: primary general membrane stress P m < S (allowable stress); primary local membrane stress P L < 1.5S; primary local membrane stress + bending stress P L + P b<1.5S; Primary local membrane stress + bending stress + secondary stress P L + P b + Q <3S. And introduce the sum of principal stresses criterion ( Yes i <4 S Local failure determination is performed.

[0048] For example, taking the most dangerous seismic condition (self-weight + hydrostatic pressure of liquid column + seismic load (positive / negative gravitational acceleration) + partial snow load + partial internal pressure) as an example, the calculated maximum stress is located at the large fillet weld at the bottom of the tank. The calculated stress intensity cloud map (stress distribution cloud map) is as follows: Figure 4 As shown. The local membrane stress is obtained. P L The stress is 10.74 MPa, representing localized membrane stress plus bending stress. P L + P b The allowable stress S of 347H stainless steel at the design temperature is 116 MPa, which is 139.88 MPa. The verification results show that: P m <1S, P L + P b The failure time is less than 1.5 seconds, which meets the requirements for plastic collapse. At the same time, the sum of the maximum principal stresses is 239.75 MPa, which is less than 4 seconds, thus meeting the requirements for local failure.

[0049] Buckling stability assessment includes: The first-order buckling mode and ideal critical load of the second target region in the target finite element model are determined by elastic buckling analysis; the first-order buckling mode is introduced into the target finite element model as an initial geometric defect through nonlinear analysis and the ideal critical load is corrected by displacement-load response to obtain the actual critical load of the second target region; the actual critical load is divided by a preset safety factor to obtain the actual allowable load, and it is determined whether the actual allowable load is greater than the design external pressure of the vertical cylindrical high-temperature molten salt storage tank.

[0050] The second target area is the part that is prone to buckling, mainly the tank top (including the support beams) and tank wall structure.

[0051] For example, the tank top model, which includes the shell and supporting beams, is constructed as follows: Figure 5 As shown; Figure 6The first-order buckling mode of the tank top was demonstrated, characterized by local collapse. The ideal critical load obtained from elastic buckling analysis was 93.6 kPa. Further nonlinear buckling analysis was conducted, introducing the first-order buckling mode as the initial geometric imperfection. The calculated actual critical load was 50.88 kPa. Dividing this by a safety factor of 3.0, the actual allowable load was 16.96 kPa, which is much greater than the design external pressure of 0.25 kPa, indicating that the tank top structure will not experience buckling instability.

[0052] Stability and ratchet effect assessment includes: for high-temperature cyclic conditions, elastic analysis and simplified inelastic analysis are used. The assessment is verified through elastic analysis. S m Limits and verification of service time and creep strain constraints are specifically as follows: Elastic analysis is based on extracting the overall or local membrane stress at any location along the cross-sectional thickness of the tank. P m and P L Apply a bending stress P b With secondary stress Q The sum and 3 S m The ratio, where S m It is the design stress strength of the target material at the service temperature to determine whether the structure is in a stable state; further, to ensure no significant creep damage during the design life, the storage tank is required to maintain a stable temperature during its service life. T i During the total duration of the stress, 1.25 was applied. S y | T i The accumulated strain is less than the creep strain limit of 0.2%. Based on the Bree diagram principle and isochronous stress-strain curves, a simplified inelastic analysis is used to calculate the cumulative ratchet strain over the entire lifespan. Specifically, the inelastic analysis process is simplified by dividing the primary and secondary stresses by the yield stress of the target material to obtain dimensionless primary and secondary stress parameters. These two dimensionless parameters are then mapped onto the Bree diagram to determine the structural response region. For each region category corresponding to the Bree diagram, the effective creep stress is calculated. Combined with the material holding time, the corresponding inelastic strain increment is obtained by interpolation based on the isochronous stress-strain curve at the corresponding temperature. The cumulative creep ratchet strain over the entire lifespan is then calculated. This ensures that the average strain along the thickness direction of the target material is <1%, and the weld strain is <0.5%.

[0053] For example, a vertical cylindrical high-temperature molten salt storage tank is checked for high-temperature cyclic conditions, and a simplified inelastic analysis is performed based on the Bree diagram principle. The analysis is based on the primary and secondary stresses calculated by finite element method, combined with the yield strength corresponding to the average temperature during the cyclic process. S y The dimensionless parameter was calculated and mapped to the elastic region in the Bree diagram. The corresponding effective creep stress was 126.16 MPa. At this stress level and operating temperature, the creep strain increment was negligible, the cyclic plastic strain increment was 0, and the corresponding inelastic strain in the isochronous stress-strain curve was 0.41%. The total ratchet creep strain was obtained by summing the strains of the above three parts, and the final total ratchet creep strain was 0.41%. The results show that the total ratchet creep strain at the top and bottom of the vertical cylindrical high-temperature molten salt storage tank is about 0.41%, which is less than the limit value of 1% for the target material, and meets the structural stability requirements.

[0054] Fatigue failure assessment includes determining the fatigue damage score based on elastic analysis or elastoplastic analysis.

[0055] Among them, the elastic analysis method is based on the linear elastic finite element analysis results of the target finite element model. The maximum nominal strain amplitude is extracted from the linear elastic finite element analysis results. The maximum nominal strain amplitude is corrected by multiaxial plasticity and Poisson's ratio adjustment coefficient and stress concentration factor to obtain the maximum equivalent strain amplitude. The fatigue damage fraction is calculated based on the maximum equivalent strain amplitude and the strain-life curve of the target material.

[0056] For example, in the case where the target material is 347H stainless steel, the maximum equivalent stress amplitude under each working condition is calculated, the strain-life curve of 347H stainless steel is consulted, and the cumulative fatigue damage is calculated. D f =0.22, cumulative damage D f If the value is less than 1.0, the structure is deemed to meet fatigue safety requirements.

[0057] Specifically, the first step is to calculate the total strain range (twice the maximum equivalent amplitude) for each working condition. .in, K v For multiaxial plasticity and Poisson's ratio adjustment factors, D This represents the corrected maximum equivalent strain range. K e This is the elastic-plastic strain correction factor. No max It is the maximum equivalent strain range (twice the maximum nominal strain amplitude). K Stress concentration factor No cThis represents the creep strain increment. Taking a complete cycle of "salt inlet-resting-salt outlet-resting" as an example, the stress intensity contour map calculated by the model is as follows: Figure 7 As shown, the maximum equivalent strain range in the cycle No max =3.06e -4 After revision e mod =4.19e -4 The maximum stress during the cycle was 107.7 MPa. The creep strain increment during this cycle can be obtained from the isochronous stress-strain curve of the material. No c Negligible, therefore the total strain range e t =4.19e -4 ;Depend on Figure 8 It can be seen that the allowed number of loops is greater than 10. 6 This cycle is expected to run 20,000 times within the 30-year design life of the vertical cylindrical high-temperature molten salt storage tank. Therefore, the fatigue damage coefficient under this condition can be conservatively calculated to be 0.02. The calculation for other design conditions is the same as above.

[0058] The elastoplastic analysis method uses the Chaboche cyclic elastoplastic constitutive model to perform nonlinear finite element cyclic analysis to obtain stress-strain tensor time history data of key nodes. Based on the stress-strain tensor time history data, the maximum strain amplitude of the vertical cylindrical high-temperature molten salt tank during the cycle is calculated. The fatigue life is calculated based on the maximum strain amplitude and the strain-life curve of the target material, and the fatigue damage fraction is determined.

[0059] The governing equations of the Chaboche cyclic elastoplastic constitutive model are: (1); (2); (3); (4); (5); (6); Among them, the total strain tensor e It can be divided into elastic strain tensor e e and plastic strain tensor e p The linear elastic behavior of formula (2) satisfies Hooke's law, where... E and v These represent the elastic modulus and Poisson's ratio, respectively. s and tr(s)Represents the stress tensor and the trace of the stress tensor. I Represents the second-order unit tensor; Equation (3) represents the von Mises yield equation. f ,in S and α These represent the deviators of the stress tensor and the back stress tensor, respectively. The symbol : represents the inner product of the second-order tensors. s y0 The initial yield stress, R To reflect the isotropic hardening variable of the yield surface size; when f When <0, it is in an elastic state; when f Plastic flow occurs when = 0; Equation (4) is the rule for associated flow. he / she p Represents the plastic strain rate tensor. l̇ This represents the plasticity multiplier. Equation (5) is the Chaboche kinematic hardening criterion, where... α i For the first i Each back stress component C i and c i For the material parameters of each back stress component, ṗ Let be the cumulative plastic strain rate. Equation (6) is the isotropic hardening evolution equation. Q and b These are material parameters describing the yield surface saturation value and evolution rate, respectively.

[0060] Furthermore, fatigue life is evaluated using a method based on the maximum strain amplitude. This method extracts the strain tensor component data within a cycle and calculates the maximum variation range of each strain component within a cycle. Based on the von Mises equivalence criterion, the maximum strain amplitude is calculated as shown in formula (7): (7); (8); in, e x ,he y ,he z For normal strain components; c xy ,c yz ,c zx For engineering shear strain components, No eq This represents the equivalent total strain range. e aThis represents the maximum strain amplitude. Based on the strain-life curve of the target material, the corresponding allowable number of cycles (i.e., fatigue life) can be obtained by referring to or interpolating the strain-life curve according to the calculated maximum strain amplitude. N f ,like Figure 7 As shown. Based on the actual number of cycles experienced by the vertical cylindrical high-temperature molten salt storage tank. n And the fatigue life obtained from the consultation N f Calculate the fatigue damage fraction of a vertical cylindrical high-temperature molten salt storage tank. D f .in: (9).

[0061] For example, Chaboche model parameters are obtained by fitting data from uniaxial strain cyclic experiments of 347H stainless steel at operating temperature. These parameters include: initial yield strength. s y ; Kinematic hardening parameters: Select 3 components (M=3) and obtain them by fitting. C 1-3 and c 1-3 Isotropic hardening parameters: Saturation stress parameters are obtained by fitting data from the cyclic steady-state process. Q and rate parameters b Substitute the above model parameters into the finite element analysis software. Calculate and extract the stress tensor and strain tensor time history data of key nodes in the critical area under stable cycle cycles. Within one load cycle, identify two time points. t 1 and t 2. This maximizes the strain amplitude between these two moments. The formulas for calculating the maximum strain amplitude are as shown in formulas (7) and (8) above.

[0062] Based on the strain-life curve of 347H stainless steel, the fatigue life can be obtained by referring to or interpolating the strain-life curve according to the calculated maximum strain amplitude. N f Based on the actual number of cycles experienced by the vertical cylindrical high-temperature molten salt storage tank n And the fatigue life obtained from the consultation N f Calculate the fatigue damage fraction of a vertical cylindrical high-temperature molten salt storage tank. D f .

[0063] like D f If the value is less than 1.0, the structure of the vertical cylindrical high-temperature molten salt storage tank is deemed to meet the fatigue safety requirements.

[0064] Creep failure assessment includes determining the creep damage score based on elastic analysis and elastoplastic analysis.

[0065] Among them, the elastic analysis method, based on the single stress grading limit, the minimum creep fracture strength curve, and the service duration, determines the creep life and creep damage fraction under service load. D c The elastoplastic analysis method uses a strain-strengthened creep equation to describe the creep behavior of the target material during the high-temperature loading stage, and calculates the creep damage fraction based on the strain energy density depletion (SEDE) model. D c The creep equation for strain-strengthened creep is: (10); in, he / she c The equivalent creep strain rate is... e cr For equivalent creep strain, q̃ For equivalent deviatoric stress, ψ c , m c as well as n c These are the temperature-related model parameters.

[0066] Creep damage can be described using formulas (11) and (12): (11); (12) (13).

[0067] in, B 1 and n 1 represents the material-related model parameters. R 0 is the universal gas constant. Q SEDE The activation energy is the strain energy density depletion model. Yes in The inelastic strain energy density dissipation rate during the load-holding phase. w f ( Yes in , T The equation for the failure strain energy density is determined by both the inelastic strain rate and temperature. Equation (10) describes the material creep constitutive equation and is used to calculate the equivalent creep strain rate under specific stress and temperature fields. he / she c This parameter, combined with the load-bearing stress, yields the inelastic strain energy density dissipation rate. Yes in and through Yes in Formula (11) defines the critical dissipation energy threshold and the damage accumulation integral of formula (12).

[0068] For example, taking the "filled and then left to stand" condition as an example, a creep assessment is performed on a dangerous point of a vertical cylindrical high-temperature molten salt storage tank, and the calculated stress intensity cloud diagram is shown below. Figure 7 As shown, the operating temperature is set at 430℃. The overall membrane stress is checked once, and the allowable value of the material at this temperature is found. S t The stress is 140 MPa; the calculation results under the operating conditions are extracted, and the overall membrane stress is calculated in one step. P m It is 64.543 MPa, which meets the requirements. P m < S t Strength requirements. Verify the combined stress of the membrane under bending and bending conditions, and the allowable limits of the material. S m The strength is 116 MPa, and the section modulus is used for rectangular sections. K =1.5, calculate the shape correction factor. K t =1.25; Extract combined stress P L + P b The pressure is 75.932 MPa, which is less than the limit value of 1.5. S m (174MPa), and the combined stress after shape correction of 77.55MPa is also less than the allowable value. S t This meets the local stress control requirements. Finally, a cumulative damage check is performed, and based on the above stress level, the allowable bearing time for this working condition is estimated to be approximately 1.2 × 10⁻⁶. 6 h, calculate the cumulative creep damage fraction for this working condition. D c = 0.067; other operating conditions are the same as above. Calculate the cumulative fatigue damage for each high-temperature load-bearing condition (after filling and settling, after salt removal and settling, etc.). D c = 0.21. Cumulative fatigue damage D c If the value is less than 1.0, the structure is deemed to meet the creep safety requirements.

[0069] Elastoplastic creep analysis: In creep constitutive models, the Norton-Bailey creep constitutive model requires different temperatures. A , n , m Three model parameters; strain-strengthened creep constitutive models require different temperatures. ψ c , m c as well as n c Three model parameters. Creep damage is calculated using formulas (11) and (12).

[0070] Based on the critical failure energy density defined by the strain energy density depletion model, the creep damage is accurately calculated through full-time integral. The total damage meets the design requirements, and the equipment is deemed safe.

[0071] The fatigue-creep failure assessment includes: linearly superimposing the fatigue damage score and the creep damage score. If the result of the linear superposition is less than 1, the vertical cylindrical high-temperature molten salt storage tank is considered safe within the design cycle and holding time.

[0072] In summary, step S150 establishes a comprehensive safety assessment system for LE1, encompassing static strength, stability, and the entire life cycle. Based on this comprehensive safety assessment system, a post-processing program can be developed using ANSYS command flow (APDL) technology to identify key areas and paths, obtain key stress, strain, and response information, and achieve an automated comprehensive safety assessment of high-temperature molten salt storage tanks considering multiple failure modes, thereby generating an assessment report.

[0073] In summary, this embodiment provides a comprehensive safety assessment method for vertical cylindrical high-temperature molten salt storage tanks. It employs simulation to evaluate the tank, first constructing a target finite element model and calculating material constitutive parameters and strain-life curves at multiple temperatures to facilitate subsequent comprehensive safety assessment calculations. Furthermore, the load spectrum construction considers various load combinations under different operating conditions, rather than using a constant load combination throughout the entire lifespan, thus better reflecting actual conditions and improving the accuracy of the subsequent comprehensive safety assessment. Finally, the comprehensive safety assessment includes multiple evaluations such as plastic collapse and local failure assessment, buckling stability assessment, stability and ratchet effect assessment, fatigue failure assessment, creep failure assessment, and fatigue and creep interactive failure assessment. This considers various complex failure modes of vertical cylindrical high-temperature molten salt storage tanks, thereby enabling a comprehensive evaluation of these tanks.

[0074] In one exemplary embodiment, a computer device is also provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above-described method embodiments.

[0075] In one exemplary embodiment, a computer-readable storage medium is provided storing a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.

[0076] In one exemplary embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.

[0077] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0078] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM).

[0079] The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0080] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0081] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A comprehensive safety assessment method for a vertical cylindrical high-temperature molten salt storage tank, characterized in that, include: Construct the target finite element model of a vertical cylindrical high-temperature molten salt storage tank; Multiple test temperatures are selected from the actual service temperature of the vertical cylindrical high-temperature molten salt storage tank. Based on the target finite element model, uniaxial tensile tests and strain-controlled fatigue tests are carried out on the target material at the multiple test temperatures to obtain the constitutive parameters, strain-life curves and isochronous stress-strain curves of the target material at the multiple test temperatures and configure them to the target finite element model. The target material is the material of the vertical cylindrical high-temperature molten salt storage tank. The operating condition spectrum and load combinations under different operating conditions of the vertical cylindrical high-temperature molten salt storage tank are set, and a load spectrum is generated based on the operating condition spectrum and the load combinations under different operating conditions. The load spectrum is applied to the target finite element model to generate a stress distribution cloud map; A comprehensive safety assessment of the vertical cylindrical high-temperature molten salt storage tank is conducted based on the stress distribution cloud map. The comprehensive safety assessment includes assessment of plastic collapse and local failure, buckling stability, stability and ratchet effect, fatigue failure, creep failure, and fatigue and creep interaction failure.

2. The comprehensive safety assessment method for vertical cylindrical high-temperature molten salt storage tanks according to claim 1, characterized in that, Constructing the target finite element model of a vertical cylindrical high-temperature molten salt storage tank, specifically including: Based on the design drawings of the vertical cylindrical high-temperature molten salt storage tank, an initial finite element model of the vertical cylindrical high-temperature molten salt storage tank was established using 3D modeling software. The target finite element model is obtained by locally refining the mesh in the stress concentration region of the initial finite element model. During the local mesh refinement process, the final mesh density of the stress concentration region is determined by mesh independence verification. The stress concentration region includes the large fillet weld and the tank top connection.

3. The comprehensive safety assessment method for vertical cylindrical high-temperature molten salt storage tanks according to claim 1, characterized in that, The operating condition spectrum includes the operating conditions of the vertical cylindrical high-temperature molten salt storage tank at various time points during its life cycle. The operating conditions are divided into normal operating conditions, seismic operating conditions, and settlement operating conditions. The load combination under the normal operating conditions includes self-weight, design internal pressure, and hydrostatic pressure of the liquid column. The load combination under the seismic operating conditions includes self-weight, hydrostatic pressure of the liquid column, seismic load, part of the snow load, and part of the design internal pressure. The load combination under the settlement operating conditions includes self-weight, hydrostatic pressure of the liquid column, design internal pressure, and non-uniform settlement displacement of the foundation. The load spectrum includes the load values ​​of the vertical cylindrical high-temperature molten salt storage tank at various time points during its life cycle. A load spectrum is generated based on the aforementioned operating condition spectrum and load combinations under different operating conditions, specifically including: Based on the service status changes of the vertical cylindrical high-temperature molten salt storage tank, the load combination of each time node in the operating condition spectrum is parameterized to generate the load spectrum. The service status changes are an alternating cycle of salt inlet state and static state.

4. The comprehensive safety assessment method for vertical cylindrical high-temperature molten salt storage tanks according to claim 1, characterized in that, The assessment of plastic collapse and localized failure includes: Based on the stress distribution cloud map, the analysis path of the first target region in the target finite element model is determined and stress linearization is performed. The total stress of the first target region is decoupled into membrane stress, bending stress and secondary stress. The first target region includes a geometric change region and a smooth region. The membrane stress of the geometric change region is a primary local membrane stress, and the membrane stress of the smooth region is a primary overall membrane stress. Determine whether the overall primary film stress is less than the permissible stress; Determine whether the localized membrane stress is less than 1.5 times the permissible stress; Determine whether the sum of the primary local membrane stress and the bending stress is less than 1.5 times the permissible stress; Determine whether the sum of the primary local membrane stress, the bending stress, and the secondary stress is less than three times the permissible stress.

5. The comprehensive safety assessment method for vertical cylindrical high-temperature molten salt storage tanks according to claim 1, characterized in that, The buckling stability assessment includes: The first-order buckling mode and ideal critical load of the second target region in the target finite element model were determined by elastic buckling analysis. The first-order buckling mode is introduced into the target finite element model as an initial geometric defect through nonlinear analysis, and the ideal critical load is corrected by displacement-load response to obtain the actual critical load of the second target region. Divide the actual critical load by a preset safety factor to obtain the actual allowable load, and determine whether the actual allowable load is greater than the design external pressure of the vertical cylindrical high-temperature molten salt storage tank.

6. The comprehensive safety assessment method for vertical cylindrical high-temperature molten salt storage tanks according to claim 1, characterized in that, The stability and ratchet effect assessment includes: 3 was verified through elasticity analysis. S m Limits and verification service time and creep strain limits; By simplifying the inelastic analysis based on the Bree diagram principle and the isochronous stress-strain curve, the cumulative ratchet strain over the entire life cycle is calculated.

7. The comprehensive safety assessment method for vertical cylindrical high-temperature molten salt storage tanks according to claim 1, characterized in that, The fatigue failure assessment includes: determining the fatigue damage score based on elastic analysis or elastoplastic analysis. The elastic analysis method is based on the linear elastic finite element analysis results of the target finite element model. The maximum nominal strain amplitude is extracted from the linear elastic finite element analysis results. The maximum nominal strain amplitude is corrected by multiaxial plasticity and Poisson's ratio adjustment coefficient and stress concentration factor to obtain the maximum equivalent strain amplitude. The fatigue damage fraction is calculated based on the maximum equivalent strain amplitude and the strain-life curve. The elastoplastic analysis method is as follows: a nonlinear finite element cyclic analysis is performed using the Chaboche cyclic elastoplastic constitutive model to obtain stress-strain tensor time history data of key nodes; based on the stress-strain tensor time history data, the maximum strain amplitude of the vertical cylindrical high-temperature molten salt storage tank during the cyclic process is calculated; fatigue life is calculated based on the maximum strain amplitude and the strain-life curve; and fatigue damage fraction is determined based on the fatigue life. The creep failure assessment includes: determining the creep damage score based on elastic analysis and elastoplastic analysis; The elastic analysis method is based on the single stress grading limit, the minimum creep fracture strength curve and the service time to determine the creep life and the creep damage fraction under the service load; The elastoplastic analysis method uses a strain-strengthened creep equation to describe the creep behavior of the target material during the high-temperature load stage, and calculates the creep damage fraction based on the strain energy density depletion model.

8. The comprehensive safety assessment method for vertical cylindrical high-temperature molten salt storage tanks according to claim 7, characterized in that, The fatigue-creep failure assessment includes: The fatigue damage score and the creep damage score are linearly superimposed. If the result of the linear superposition is less than 1, the vertical cylindrical high-temperature molten salt storage tank is determined to be safe within the design cycle and holding time.

9. A computer device, comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the computer program to implement the comprehensive safety assessment method for the vertical cylindrical high-temperature molten salt storage tank according to any one of claims 1-8.

10. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the comprehensive safety assessment method for the vertical cylindrical high-temperature molten salt storage tank as described in any one of claims 1-8.

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