A method for evaluating the life of a vacuum chamber of a nuclear fusion reactor based on a plastic strain correction formula

Abstract

This invention relates to the field of vacuum chamber lifetime assessment technology for nuclear fusion reactors, and in particular to a method for assessing the lifetime of a nuclear fusion reactor vacuum chamber based on a plastic strain correction formula. The proposed method for assessing the lifetime of a nuclear fusion reactor vacuum chamber based on a plastic strain correction formula first constructs a simple finite element analysis model and a plastic strain correction formula; then, it obtains the operating load of the vacuum chamber and infers the stress based on the simple finite element analysis model; finally, it calculates the elastoplastic strain value S of the vacuum chamber under this operating condition using the plastic strain correction formula. total Find the S-N strain fatigue parameter curve of the vacuum chamber structural material and obtain the strain value S. total The corresponding number of fatigue cycles. This invention overcomes the problem that finite element fatigue analysis tools are insufficient for the analysis of vacuum chambers in nuclear fusion reactors, reducing evaluation costs while ensuring evaluation efficiency.

Description

Technical Field

[0001] This invention relates to the field of nuclear fusion reactor vacuum chamber lifetime assessment technology, and in particular to a method for assessing the lifetime of nuclear fusion reactor vacuum chambers based on a plastic strain correction formula. Background Technology

[0002] The vacuum chamber is a key and permanent component of a fusion device. Its function is to provide an ultra-high vacuum operating environment for the thermonuclear fusion reaction, ensuring stable plasma confinement and efficient operation. The primary function of the vacuum chamber is to efficiently remove alpha particle energy and decay heat deposited on the chamber walls and other internal components such as the first wall. Secondly, it provides sufficient rigid support and mounting reference for internal functional components such as the blanket, divertor, and diagnostic system. Furthermore, the vacuum chamber must possess sufficient structural integrity to withstand the enormous electromagnetic forces, thermal shocks, and mechanical loads caused by extreme plasma disruption events, vertical displacement events, and other abnormal transient conditions. Its design and evaluation must comprehensively consider complex thermo-mechanical-electromagnetic multiphysics coupling effects. As a permanent component, fatigue life analysis of the vacuum chamber is crucial. Traditional vacuum chamber life assessment uses the finite element method for fatigue analysis. First, a detailed three-dimensional finite element model of the vacuum chamber structure needs to be established to accurately characterize its geometric features, especially key areas prone to stress concentration such as welds, openings, and support connections. Secondly, based on the operating conditions of the vacuum chamber, the corresponding temperature and electromagnetic force fields are calculated, and these thermo-mechanical multiphysics loads are applied as boundary conditions to the structural model. Subsequently, through nonlinear static or transient dynamic analysis, the stress-strain response of the structure under cyclic loading is solved, focusing on obtaining the stress amplitude and mean stress of key components. Based on this, combined with the material's fatigue performance curves (SN curves) or crack propagation rate data, and selecting an appropriate fatigue damage accumulation model (such as Miner's linear accumulation rule or a more advanced continuous damage mechanics model), the fatigue life of the vacuum chamber is predicted and evaluated. The entire analysis process requires mesh sensitivity verification to ensure result convergence, and is often supplemented with sub-modeling techniques to balance computational efficiency and local accuracy, ultimately providing crucial theoretical basis for the design optimization and maintenance strategies of the vacuum chamber.

[0003] As a critical component that withstands extreme thermal, mechanical, and radiation loads, the structural integrity assessment of the vacuum chamber in a nuclear fusion reactor is of paramount importance. While fatigue analysis using the finite element method has become a common engineering technique, it has several significant limitations and drawbacks when applied to such extreme environments.

[0004] First, there is a contradiction between the extreme complexity of the load spectrum in finite element analysis and the simplified modeling. In actual operation, vacuum chambers are subjected to non-uniform, transient thermo-mechanical-electromagnetic multi-field coupled loads, such as the enormous electromagnetic force and thermal shock generated by plasma rupture. Finite element models typically simplify the loads by periodization, symmetry, or quasi-static methods. This simplification may filter out critical high-frequency dynamic stress components, thus missing some potentially dangerous fatigue damage modes.

[0005] Secondly, balancing computational cost and accuracy is difficult. To capture the detailed evolution of local stress concentrations (such as welds and openings), extremely fine mesh generation and nonlinear transient analysis are required. The vacuum chamber structural model load, and the finite element mesh of a complete vacuum chamber design model, can reach hundreds of millions of elements, placing extremely high demands on computational resources. Taking ITER (International Thermonuclear Experimental Reactor) as an example, its operating conditions number in the hundreds, requiring a vast amount of computational resources. It often requires hundreds of thousands of workstations for finite element simulations, several months for finite element mesh optimization, and a complete finite element fatigue life assessment of a vacuum chamber takes one to two years. Furthermore, it requires personnel with extensive experience in nuclear pressure vessel design and analysis to conduct the life assessment.

[0006] In conclusion, while the finite element fatigue analysis tool is an indispensable analytical tool for the future nuclear fusion reactor vacuum chamber, its inherent shortcomings, such as the difficulty in handling load realism, computational model processing, and high personnel skill requirements, mean that its accuracy, efficiency, and economy cannot meet the rapid design requirements of future commercial fusion reactors. Summary of the Invention

[0007] To overcome the problem that finite element fatigue analysis tools are insufficient for the analysis of vacuum chambers in nuclear fusion reactors, this invention proposes a method for assessing the lifespan of nuclear fusion reactor vacuum chambers based on a plastic strain correction formula, which reduces assessment costs while ensuring assessment efficiency.

[0008] This invention proposes a method for assessing the lifespan of a nuclear fusion reactor vacuum chamber based on a plastic strain correction formula. First, a simple finite element analysis model and a plastic strain correction formula are constructed. The simple finite element analysis model is based on ideal linear elastic parameters and incorporates inertial loads, electromagnetic loads, pressure loads, and thermal loads. The plastic strain correction formula, combined with the stress derived from the simple finite element analysis model and the operating parameters, calculates the elastoplastic strain value S of the vacuum chamber. total ; The operating load of the vacuum chamber is obtained, and the stress is inferred based on a simple finite element analysis model. The elastic-plastic strain value S of the vacuum chamber under this condition is calculated using the plastic strain correction formula. total ; Find the SN strain fatigue parameter curve of the vacuum chamber structural material and obtain the strain value S. total The corresponding number of fatigue cycles.

[0009] Preferably, the plastic strain correction formula is: ( ) +

[0010] in, V is the elastoplastic strain value of the vacuum chamber; v is Poisson's ratio; E is Young's modulus under the corresponding working condition; P m For primary membrane stress, P L For a single bending stress, P Q The stress is secondary, and the three factors are obtained through a simple finite element analysis model. This is the secondary stress-strain correction factor. is the triaxial plastic strain correction factor, K is the pressure constant related to room temperature, and m is a constant related to room temperature; it can be obtained by fitting the formula.

[0011] The preferred method for obtaining the elastic-plastic strain correction formula is as follows: S11. First, filter the operating conditions and statistically analyze the parameters under each operating condition. , K and m; S12. Construct a simple finite element analysis model to calculate the primary membrane stress P obtained under each working condition. m Primary bending stress P L and secondary stress P Q The finite element fatigue analysis tool was used to calculate the elastoplastic strain values ​​of the vacuum chamber under each working condition. ; S13, Construct a working condition sample set {P m ,P L ,P Q , , ,K,m; }; S14, in the working condition sample set {P m ,P L ,P Q , , ,K,m; The fitted elastic-plastic strain correction formula is used.

[0012] Preferred, , The values ​​of K and m are determined according to the nuclear pressure vessel design specifications.

[0013] Preferably, the simple finite element analysis model ignores material plasticity and specified complex features of the vacuum chamber, including fillets, openings, and welds of the vacuum chamber model.

[0014] The present invention proposes a nuclear fusion reactor vacuum chamber lifetime assessment system, comprising a memory and a processor. The memory stores a computer program, and the processor is connected to the memory. The processor is used to execute the computer program to implement the nuclear fusion reactor vacuum chamber lifetime assessment method based on the plastic strain correction formula.

[0015] The present invention proposes a storage medium storing a computer program, which, when executed, is used to implement the nuclear fusion reactor vacuum chamber lifetime assessment method based on the plastic strain correction formula.

[0016] The advantages of this invention are: (1) This invention proposes a simple finite element analysis model that ignores the plasticity of the material and only considers the ideal linear elastic parameters of the material. It combines the plastic strain correction formula to quickly solve the elastic-plastic strain value of the material, and calculates the fatigue cycle life parameter of the nuclear fusion reactor vacuum chamber by comparing it with the SN curve of the vacuum chamber structure material. This invention has significant advantages such as accuracy, efficiency and economy.

[0017] (2) In the complex and harsh fusion operating environment, the vacuum chamber structure faces extreme loads from multiple coupled thermal, electromagnetic, and mechanical fields. While precise numerical simulation using finite element software is accurate, it is time-consuming and expensive. Compared to traditional finite element fatigue life assessment methods, which require complete and detailed finite element analysis models and meshes, this invention can ignore the complex features of the vacuum chamber model, such as fillets, openings, and welds. Through simple and rapid preliminary finite element analysis, it solves the primary and secondary stresses of the vacuum chamber under the corresponding operating conditions. Combining a large amount of engineering experimental data and engineering practice, it constructs an elastic-plastic strain correction formula, which can quickly and accurately estimate the fatigue life and damage of key parts during the fusion reactor design stage. This greatly reduces the difficulty of finite element analysis and the demand for computing resources, significantly improves the efficiency of fusion reactor vacuum chamber life assessment, quickly guides structural engineers to optimize and iterate structural designs, and significantly reduces design costs. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for assessing the lifetime of a nuclear fusion reactor vacuum chamber based on a plastic strain correction formula, as proposed in this invention. Figure 2 This is a flowchart illustrating the construction of the modified formula for elastic-plastic strain. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Reference Figure 1 This invention proposes a method for assessing the lifespan of a nuclear fusion reactor vacuum chamber based on a plastic strain correction formula. This method ignores material plasticity and only considers a simple finite element analysis model and a plastic strain correction formula based on the ideal linear elastic parameters of the material. It can quickly solve for the elastic-plastic strain values ​​of the material and calculate the fatigue cycle life parameters of the nuclear fusion reactor vacuum chamber by comparing them with the SN curves of the vacuum chamber structure material.

[0021] The first step in this method is to construct the elastic-plastic strain correction formula as follows: ( ) + (1) in, V is the elastoplastic strain value of the vacuum chamber; v is Poisson's ratio; E is Young's modulus under the corresponding working condition; P m For primary membrane stress, P L For a single bending stress, P Q The stress is secondary, and all three can be obtained through finite element simulation; This is the secondary stress-strain correction factor. is the triaxial plastic strain correction factor, K is the pressure constant related to room temperature, and m is a constant related to room temperature; it can be obtained by fitting the formula.

[0022] Specifically, the fitting process of the elastic-plastic strain correction formula includes the following steps: S11. First, filter the operating conditions, including normal operating conditions and accident operating conditions; then, statistically analyze the parameters for each operating condition. , K and m; S12. Construct a simple finite element analysis model to calculate the primary membrane stress P obtained under each working condition. m Primary bending stress P L and secondary stress P Q The finite element fatigue analysis tool was used to calculate the elastoplastic strain values ​​of the vacuum chamber under each working condition. ; S13, Construct a working condition sample set {P m ,P L ,P Q , , ,K,m; }; S14, in the working condition sample set {P m ,P L ,P Q , , ,K,m; By fitting the elastic-plastic strain correction formula on the}, we obtain formula (1).

[0023] , The values ​​of K and m are determined according to relevant design specifications, such as the nuclear pressure vessel design specifications, as follows: For secondary stress strain correction factors, the strain correction factors are 1.02, 1.08, 1.15, 1.23, and 1.30 for thermal stresses of 100, 200, 300, 300, and 500 MPa, respectively. For triaxial plastic strain correction factors, the strain correction factors are 1.02, 1.06, 1.10, 1.14, and 1.17 for thermal stresses of 100, 200, 300, 300, and 500 MPa, respectively. K is taken as 798 MPa at room temperature, 772 MPa between 20℃ and 650℃, and 679 MPa above 650℃. m is taken as 0.3387 at room temperature, 0.3025 for 20℃-650℃, and 0.2365 for above 650℃.

[0024] It is worth noting that in the modified elastic-plastic strain formula (1), the primary membrane stress P m Primary bending stress P L and secondary stress P Q .

[0025] This invention proposes a method for assessing the lifetime of a nuclear fusion reactor vacuum chamber based on a plastic strain correction formula, the steps of which are as follows: S1. Determine the operating load of the vacuum chamber and construct a simple finite element analysis model to characterize the mapping of inertial load, electromagnetic load, pressure load and thermal load to the operating conditions. The isotropic linear elastic material adopts the set basic properties.

[0026] In practical implementation, the load under vacuum chamber operation conditions can be determined by the load design specifications for vacuum chambers of nuclear fusion reactors. This will clarify the inertial load, electromagnetic load, pressure load, and thermal load borne by the vacuum chamber under operation or accident conditions, thereby establishing a simplified finite element analysis model of the vacuum chamber, ignoring complex features such as fillets, openings, and welds; and using basic isotropic linear elastic material properties, ignoring the material's elastic-plastic parameters.

[0027] It should be emphasized that the simple finite element analysis model used in this step is consistent with all the simple finite element analysis models used in the fitting sample constructed in step S12, in order to improve the application stability of the elastic-plastic strain correction formula.

[0028] S2. Apply inertial load, electromagnetic load, and pressure load to a simple finite element analysis model. Perform a primary stress analysis using finite element analysis software Workbench or ANSYS Classic. Obtain the primary membrane stress P through stress linearization. m and primary bending stress P L Thermal stress is applied to a simple finite element analysis model, and the secondary stress P is obtained by classical calculation using finite element analysis software Workbench or ANSYS. Q ; S3, the primary film stress P obtained in step S2 m Primary bending stress P L and secondary stress P Q And the Young's modulus E and coefficients corresponding to the operating conditions , Substituting the pressure K and constant m into the elastoplastic strain correction formula (1), the total elastoplastic strain value of the vacuum chamber of the nuclear fusion reactor (referred to as the vacuum chamber elastoplastic strain value) S is calculated. total ; strain value S total The strain consists of four parts: total elastic strain, plastic strain caused by primary stress, plastic strain defined by Nueber's hyperbola rule, and plastic strain caused by triaxial force. In this embodiment, the strain value S is calculated using the elastic-plastic strain correction formula. total This greatly improves computational efficiency.

[0029] S4. Locate the SN strain fatigue parameter curve of the vacuum chamber structural material and obtain the strain value S. total The corresponding number of fatigue cycles is used to determine the number of fatigue cycles under this working condition.

[0030] Of course, those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0031] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0032] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A method for assessing the lifetime of a nuclear fusion reactor vacuum chamber based on a plastic strain correction formula, characterized in that, First, a simple finite element analysis model and a plastic strain correction formula are constructed. The simple finite element analysis model, based on ideal linear elastic parameters, is used to analyze inertial loads, electromagnetic loads, pressure loads, and thermal loads. The plastic strain correction formula, combined with the stress derived from the simple finite element analysis model and the operating parameters, calculates the elastoplastic strain value S of the vacuum chamber. total ; Obtain the operating load of the vacuum chamber and infer the stress based on a simple finite element analysis model; The elastic-plastic strain value S of the vacuum chamber under this working condition was calculated using the plastic strain correction formula. total ; Find the SN strain fatigue parameter curve of the vacuum chamber structural material and obtain the strain value S. total The corresponding number of fatigue cycles.

2. The method for assessing the lifetime of a nuclear fusion reactor vacuum chamber based on a plastic strain correction formula as described in claim 1, characterized in that, The formula for correcting plastic strain is: ( ) + in, V is the elastoplastic strain value of the vacuum chamber; v is Poisson's ratio; E is Young's modulus under the corresponding working condition; P m For primary membrane stress, P L For a single bending stress, P Q The stress is secondary, and the three factors are obtained through a simple finite element analysis model. This is the secondary stress-strain correction factor. is the triaxial plastic strain correction factor, K is the pressure constant related to room temperature, and m is a constant related to room temperature; it can be obtained by fitting the formula.

3. The method for assessing the lifetime of a nuclear fusion reactor vacuum chamber based on a plastic strain correction formula as described in claim 2, characterized in that, The method for obtaining the elastic-plastic strain correction formula is as follows: S11. First, filter the operating conditions and statistically analyze the parameters under each operating condition. , K and m; S12. Construct a simple finite element analysis model to calculate the primary membrane stress P obtained under each working condition. m Primary bending stress P L and secondary stress P Q The finite element fatigue analysis tool was used to calculate the elastoplastic strain values ​​of the vacuum chamber under each working condition. ; S13, Construct a working condition sample set {P m ,P L ,P Q , , ,K,m; }; S14, in the working condition sample set {P m ,P L ,P Q , , ,K,m; The fitted elastic-plastic strain correction formula is used.

4. The method for assessing the lifetime of a nuclear fusion reactor vacuum chamber based on a plastic strain correction formula as described in claim 2, characterized in that, , The values ​​of K and m are determined according to the nuclear pressure vessel design specifications.

5. The method for assessing the lifetime of a nuclear fusion reactor vacuum chamber based on a plastic strain correction formula as described in claim 1, characterized in that, The simple finite element analysis model ignores material plasticity and the specified complex features of the vacuum chamber, which include fillets, openings, and welds in the vacuum chamber model.

6. A life assessment system for a nuclear fusion reactor vacuum chamber, characterized in that, It includes a memory and a processor. The memory stores a computer program, and the processor is connected to the memory. The processor is used to execute the computer program to implement the nuclear fusion reactor vacuum chamber lifetime assessment method based on the plastic strain correction formula as described in any one of claims 1-5.

7. A storage medium, characterized in that, The system contains a computer program that, when executed, implements the method for assessing the lifetime of a nuclear fusion reactor vacuum chamber based on a plastic strain correction formula as described in any one of claims 1-5.

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