Anti-seismic force calculation method for camera shield support frame of nuclear fusion experimental device

Abstract

This invention discloses a method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device. The method includes the following steps: initializing a simulated horizontal camera shield support frame under static conditions, specifically: performing static analysis on the static condition to obtain the deformation and stress distribution of the support frame under static load, and performing strength verification; performing dynamic analysis on the seismic dynamic condition, including at least modal analysis and spectral analysis based on seismic load, to obtain the dynamic response of the support frame under seismic load; and combining the static analysis results with the dynamic analysis results to perform a comprehensive strength verification of the support frame under seismic conditions. This invention, through precise finite element modeling, static and dynamic analysis, and strength verification, solves problems such as the complexity of mechanical analysis of irregular structures, the difficulty in balancing load-bearing capacity and lightweight design, and the balance between high-intensity seismic resistance requirements and structural efficiency.

Description

Technical Field

[0001] This invention belongs to the technical field of nuclear fusion experimental devices, and particularly relates to a method for calculating the seismic stress of a camera shield support frame used in nuclear fusion experimental devices. Background Technology

[0002] The nuclear fusion experimental device is a key large-scale scientific instrument for simulating the reactions inside the sun and exploring future clean energy sources. Its operation involves extreme physical conditions, making real-time and accurate diagnosis of the plasma state inside the device crucial. The camera system, as one of the core optical diagnostic devices, bears the heavy responsibility of high-resolution imaging and monitoring of plasma morphology and radiation distribution. To ensure the camera system can operate stably and accurately for extended periods in harsh environments with strong magnetic fields, high vacuum, and strong radiation, a dedicated support frame with sufficient rigidity, high stability, and precise positioning must be designed.

[0003] However, in the extremely complex and crowded engineering environment of a nuclear fusion device, designing a camera support frame that meets all requirements presents a series of interconnected and highly challenging technical problems: 1. Limited Support Structure Topology and Complex Mechanical Analysis: The nuclear fusion device's main unit and surrounding area are already filled with complex coils, vacuum chambers, cold shields, feeder systems, and various diagnostic ports, leaving extremely narrow and irregular installation space for the camera support frame. This directly results in the main support column at the bottom of the frame not being able to adopt a symmetrical, regular grid arrangement, but instead being forced to present a unique "I / F" shaped asymmetrical and irregular topology. This "fitting in the gaps" layout severely violates the simplified analysis premise of traditional structural mechanics based on regular frameworks, making the force path of the structure unclear and the internal force flow distribution exceptionally complex. Traditional structural mechanics manual calculation methods or calculation models based on simple assumptions are insufficient to accurately assess the internal force distribution and deformation of such irregular structures under static loads, and cannot provide a reliable basis for optimization design.

[0004] 2. The Sharp Contradiction Between Extreme Load-Bearing Capacity and Ultimate Lightweight Design: To shield neutrons and gamma rays generated by nuclear fusion reactions and protect delicate optical camera components, the support frame needs to support heavy shielding materials weighing over 20 tons (such as boron-polyethylene, lead, and other composite materials). This requires the support frame to possess extremely high load-bearing strength and stiffness. However, on the other hand, to reduce the load on the plant floor, facilitate transportation and installation during remote maintenance, and strictly adapt to the millimeter-level clearance in the surrounding installation space to avoid interference, every effort must be made to achieve lightweight design of the support frame itself. "Heavy load" and "lightweight" form a fundamental design conflict. Simply increasing the material cross-section will sacrifice space and increase the burden, while excessively pursuing lightweight design may lead to insufficient stiffness, instability, or fatigue failure.

[0005] 3. The Difficult Balance Between High-Intensity Seismic Safety and Structural Efficiency: Many nuclear fusion devices are built in seismically active zones, and their seismic design must meet standards such as China's "GB50011-2010 Code for Seismic Design of Buildings" and even more stringent seismic standards for nuclear facilities. The support frame must ensure that it does not overturn, collapse, or fail under the action of a design earthquake or even a rare earthquake, guaranteeing the integrity of the camera diagnostic circuitry. Traditional seismic design strategies often tend to increase diagonal bracing, enlarge component cross-sections, and set redundant constraints, but this inevitably leads to a surge in structural weight and low material utilization, directly contradicting the aforementioned "lightweighting" goal. Therefore, how to endow irregular lightweight structures with high seismic performance through ingenious mechanical design and precise calculations without significantly increasing weight and complexity is a cutting-edge problem involving multiple disciplines such as dynamics and structural optimization.

[0006] 4. Limitations of Existing Design Methods and Calculation Tools: Faced with the aforementioned complex challenges, conventional design processes and calculation tools reveal significant shortcomings. First, for irregular supports of the "I / F" shape, traditional static equivalent methods struggle to accurately account for their three-dimensional coupled vibration modes and dynamic amplification effects under seismic dynamic loads. Second, lightweight design under the dual constraints of heavy load and seismic resistance is a typical "multi-objective optimization" problem. Iterative trial-and-error methods relying on engineer experience are inefficient and struggle to find the global optimum. While existing general-purpose finite element software can perform the analysis, it lacks integrated, parameterized, and automated calculation methods specifically designed for such problems. This results in complex initial modeling, long calculation cycles, limited optimization exploration space, and an inability to quickly respond to tight project deadlines.

[0007] In summary, the core of designing the camera support frame for a nuclear fusion experimental device lies in solving the synergistic optimization problem of four mutually restrictive and demanding conditions: "irregular topology," "heavy load," "lightweight design," and "high seismic resistance." Currently, there is a lack of a dedicated stress analysis and seismic calculation method that can systematically, accurately, and efficiently solve this complex engineering problem. Summary of the Invention

[0008] This invention addresses the problems existing in the prior art by proposing a method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device. The aim is to solve the problem of synergistic optimization of four mutually restrictive and demanding conditions: "irregular topology," "heavy load," "lightweight," and "high seismic resistance."

[0009] To solve its technical problems, the present invention proposes the following technical solutions: A method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device is provided. The method is based on an irregularly shaped camera support frame, which includes: an irregularly topological first-layer platform (1) and a second-layer platform (2) arranged on the first-layer platform; the irregularly topological first-layer platform is provided with a first-layer support structure (1-1) and a second-layer support structure; the first-layer support structure (1-1) is composed of multiple irregularly topological and vertically arranged main support columns (1-1-1) and lower connecting beams (1-1-2) connecting the main support columns; the second-layer support structure is located above the first-layer support structure (1-1) and is composed of multiple top ends of multiple irregularly topological main support columns (1-1-1) and at least two interconnected rectangular frame units (1-2-1) arranged on the multiple top ends. The second-layer platform (2) is a cuboid support body, which is fixedly installed on the second-layer support structure. The cuboid support body is composed of multiple vertical support columns (2-1) and crossbeams (2-2) connected between the support columns. The support surface (2-3) on the second-layer platform (2) is used to directly support the camera irregular shield. The calculation method is characterized by the following steps: Step 1: Initialize the simulated camera shield support frame operating conditions. The specific process is as follows: (1) Construct a finite element simulation model of the camera support frame, and set the connection relationship between each component according to the actual structure of the support frame; (2) Assign preset material mechanical parameters to the materials in the simulation model; (3) Mesh the simulation model; (4) Apply loads and boundary conditions to the simulation model. The loads include at least: gravity loads, pressure loads simulating the weight of the camera, and seismic loads calculated based on seismic fortification requirements; and set analysis conditions including static and seismic dynamic conditions. (5) The weld strength of the welded structure of the support frame is checked; Step 2: Perform static analysis on the static working condition to obtain the deformation and stress distribution of the support frame under static load, and perform strength verification. Step 3: Perform dynamic analysis on the earthquake dynamic conditions. The dynamic analysis includes at least modal analysis and spectral analysis based on earthquake loads to obtain the dynamic response of the support frame under earthquake loads. Step 4: Combine the static analysis results with the dynamic analysis results to perform a comprehensive strength check on the support frame under seismic conditions.

[0010] Furthermore, in step one (1), when constructing the finite element simulation model, shell elements are used for modeling based on the ratio of the thickness to the length of the support frame structure, and common node processing is performed at the connection and intersection.

[0011] Furthermore, in step one, process (3), the main load-bearing structural components are divided using quadrilateral grids.

[0012] Furthermore, in step one, process (4), the seismic load is calculated and determined according to GB 50011-2010 "Code for Seismic Design of Buildings", and the input of the seismic load is the seismic acceleration spectrum in the horizontal direction.

[0013] Furthermore, in step two, the strength verification is performed using the fourth strength theory, and the maximum stress must be less than the design stress intensity of the material. The design stress intensity is obtained by dividing the yield strength of the material by the safety factor, which is 2.

[0014] Further, the weld strength verification in step one (5) is as follows: based on the stress state of the fillet weld, and based on the preset safety factor and the yield strength of the supporting structure base material, the allowable stress of the weld is calculated, and the allowable stress is selected as 108MPa.

[0015] Furthermore, in step three, the spectral analysis is a response spectral analysis.

[0016] Furthermore, in step four, the comprehensive strength verification includes: combining static stress and dynamic response stress, and comparing the combined stress with a preset allowable stress limit; wherein the allowable stress limit is determined based on the ultimate strength and yield strength of the material under accident conditions.

[0017] Furthermore, the allowable stress limit is taken as the smaller of (material ultimate strength Su / 3) and (2 times the material yield strength Sy / 3), which is 165.6 MPa.

[0018] Furthermore, in the strength verification of step two and / or step four, the stress in the stress concentration area is linearized, and the sum of the membrane stress and bending stress obtained by the linearization process is compared with the design stress of the material. Advantages and effects of the present invention

[0019] 1. Solves the problem of complex mechanical analysis of irregular topological structures: Addressing the difficulty of accurate mechanical analysis of asymmetric support structures such as "I / F" shapes using existing technologies, this invention constructs a precise finite element model to realistically reflect irregular topological structures, avoiding errors caused by simplification assumptions. By assigning accurate material mechanics parameters to the simulation model, the authenticity and reliability of the calculation results are ensured, providing a solid foundation for subsequent optimization design.

[0020] 2. Balancing the contradiction between ultimate load-bearing capacity and extreme lightweight design: Addressing the challenge of supporting heavy-duty shielding structures while simultaneously achieving lightweight construction, this invention employs shell element modeling and common-node processing, significantly improving computational efficiency and reducing computation time while maintaining accuracy. By obtaining natural frequencies and mode shapes through modal analysis and combining this with response spectrum analysis, the structural dynamic response can be optimized, weak points identified, and materials rationally allocated to achieve lightweight design while meeting strength and stiffness requirements.

[0021] 3. Achieving a balance between high-intensity seismic safety and structural efficiency: Addressing the structural redundancy issue caused by traditional seismic design, this invention determines the horizontal seismic acceleration spectrum according to the "Code for Seismic Design of Buildings," realistically simulating seismic action and providing accurate input for subsequent dynamic analysis. Through dynamic analysis, including modal analysis and spectral analysis, the dynamic response of the support frame under seismic loads is obtained, solving the problem that traditional static equivalent methods cannot accurately account for three-dimensional coupled vibration modes and dynamic amplification effects.

[0022] 4. Improved computational efficiency and accuracy, overcoming the limitations of existing design methods and computational tools: This invention ensures the safety of the structure under different working conditions by separately verifying the strength of the support frame under static and seismic conditions, and verifying the weld strength of the welded structure. By combining the static analysis results with the dynamic analysis results, the stress in the stress concentration area is linearized, avoiding overly conservative design and making the strength verification more precise and reliable.

[0023] 5. Employing reasonable strength verification standards to ensure structural safety: Static strength verification is performed using the fourth strength theory, with a safety factor of 2 to ensure that the maximum stress is lower than the design stress intensity. The allowable stress of the weld is calculated based on the yield strength of the supporting structure's base material to ensure the safety of the welded structure. The smaller value between (material ultimate strength Su / 3) and (twice the material yield strength Sy / 3) is used as the allowable stress limit to ensure structural safety under accident conditions. Attached Figure Description

[0024] Figure 1a This is a schematic diagram of the overall structure of the camera support bracket of the present invention; Figure 1b This is the first-view perspective of the camera support frame platform of the present invention. Figure 1c This is the second perspective view of the camera support frame's first-layer platform of the present invention; Figure 1d This is an application effect diagram of the camera support bracket of the present invention; Figure 1e This is a schematic diagram of the weld structure of the camera support frame of the present invention; Figure 1f This is a schematic diagram of the welding calculation area for the camera support frame of the present invention; Figure 1g This is a schematic diagram of the stress linearization path of the camera support frame in this invention; Figure 2 This is a simplified schematic diagram of the camera support bracket of the present invention; Figure 3 This is a schematic diagram of the boundary conditions for the camera support frame of the present invention; Figure 4 This is a schematic diagram of the displacement of the camera support bracket of the present invention; Figure 5 This is a schematic diagram of the stress cloud of the camera support bracket of the present invention; Figure 6 This is a schematic diagram of the principal vibration mode in the X direction of the present invention; Figure 7 This is a schematic diagram of the principal vibration mode in the Y direction of the present invention; Figure 8 This is a schematic diagram of stress under seismic load according to the present invention; Figure 9 This is a force cloud diagram of the camera support frame of the present invention; Figure 10 This is a flowchart of the method for calculating the seismic stress of the camera shield support frame according to the present invention; In the diagram: 1: First-floor platform; 1-1: First-floor support structure; 1-1-1: Main support column; 1-1-2: Lower-level connecting beam; 1-2-1: Rectangular frame unit; 2: Second-floor platform; 2-1: Second-floor platform support column; 2-2: Second-floor platform beam; 2-3: Support surface. Detailed Implementation Design principle of the invention

[0025] 1. Precise Modeling and Efficient Analysis: 1) Precise Modeling of Irregular Structures: For asymmetric and irregular support column layouts (such as "I / F" shapes) caused by limited installation space, the finite element method is used for precise modeling, avoiding simplification assumptions and accurately reflecting complex topologies. 2) Shell Element Simplification: For irregular support frames of multi-layer platforms and complex steel structures, shell element modeling is used, and common nodes are handled at the connections, significantly improving computational efficiency while ensuring accuracy. 3) Optimized Mesh Generation: Quadrilateral meshes are used for key load-bearing components to improve stress calculation accuracy, suitable for major load-bearing parts.

[0026] 2. Comprehensive Assessment and Safety Verification of Multiple Loads: 1) Static-Dynamic Coupling Analysis: Combining static analysis (gravity, equipment loads) and dynamic analysis (seismic loads) to obtain the initial stress state and dynamic response of the structure. 2) Code-Based Seismic Loads: Determining the horizontal seismic acceleration spectrum according to the "Code for Seismic Design of Buildings" (GB 50011-2010) to realistically simulate seismic action. 3) Standardized Load Combination: Superimposing the static and dynamic analysis results according to the code for comprehensive strength verification. 4) Multiple Strength Verification Standards: The fourth strength theory is adopted for static load cases, with a safety factor of 2 to ensure that the maximum stress is lower than the design stress intensity. Seismic Load Cases: Combining static stress and dynamic response stress, the allowable stress limit is taken as the smaller value between (ultimate strength Su / 3) and (2 times yield strength Sy / 3). Welded Structure Verification: Weld strength is verified separately. Stress Linearization: The stress concentration area is decomposed into membrane stress and bending stress for precise evaluation to avoid over-conservatism.

[0027] 3. Balancing lightweight design and high seismic resistance: Natural frequencies and mode shapes are obtained through modal analysis, and the structural dynamic response is optimized by combining this with response spectrum analysis. Weak points are identified through precise calculations, and materials are rationally allocated while meeting strength and stiffness requirements to achieve lightweight design.

[0028] In summary, this invention, through precise analysis, standardized verification, and optimized design, achieves a balance between lightweight construction, heavy-duty operation, and high seismic resistance for irregular topologies while ensuring absolute safety. This method provides a reliable and efficient computational basis for the design of camera support frames for nuclear fusion experimental devices. Innovation of this invention:

[0029] 1. Focus on precise analysis of irregular layouts: Traditional methods struggle to handle asymmetrical and irregular main support column layouts, such as "I / F" shapes, formed due to site constraints. This method is the first to clearly define the necessity of precise mechanical and seismic analysis for such special layouts and provides targeted solutions.

[0030] 2. Establishing a simplified and efficient analysis process for irregular structures: For multi-layered platforms and complex steel structures with irregular shapes, an innovative standardized finite element analysis process is proposed. Through key technologies such as shared nodes for shell elements and simplification of detailed features, the modeling and analysis efficiency of complex models is significantly improved while ensuring computational accuracy, laying the foundation for rapid iterative design.

[0031] 3. Achieve comprehensive performance evaluation based on multi-factor coupling: Abandoning single-load verification, a comprehensive evaluation system combining statics (gravity, equipment loads) and dynamics (seismic response) is adopted. Through standardized load combinations, the results of modal analysis and response spectrum analysis are superimposed with static analysis to comprehensively assess the strength and stiffness of the structure during its service life and under accident conditions.

[0032] 4. Introduction of high-standard professional seismic assessment criteria: Exceeding general building seismic codes, the "Class D usage restriction" in the ASME BPVCIII NF code is directly adopted as the assessment standard for accident conditions. Through stress linearization technology, the membrane stress and bending stress in key parts are separated and verified, making the seismic performance assessment more precise, rigorous, and reliable.

[0033] 5. Achieving a balance between lightweight design and high seismic resistance. The ultimate goal of this method is to resolve the conflict between the structural redundancy and bulkiness caused by traditional seismic design and the compact and lightweight requirements of modern precision equipment. Through the above precise analysis and high-standard evaluation, it is possible to optimize material distribution, reduce structural weight, and perfectly adapt to narrow installation spaces while ensuring absolute safety, thus achieving the optimal balance between safety and economy.

[0034] Based on the above principles, this invention designs a method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device, such as... Figure 1a , 1b As shown in 1c, 1d, 1e, 1f, 1g, 2, 3, 4, 5, 6, 7, 8, 9, and 10, this calculation method is based on a camera irregular support frame, which includes: an irregular topological first-layer platform 1 and a second-layer platform 2 arranged on the first-layer platform; the irregular topological first-layer platform is provided with a first-layer support structure 1-1 and a second-layer support structure; the first-layer support structure 1-1 is composed of multiple irregular topological and vertically arranged main support columns 1-1-1 and lower connecting beams 1-1-2 connecting the main support columns; the second-layer support structure 1-2 is set above the first-layer support structure 1-1 and is composed of multiple tops of multiple irregular topological main support columns 1-1-1 and at least two interconnected rectangular frame units 1-2-1 arranged on the multiple tops; The second-layer platform 2 is a cuboid support, which is fixedly installed on the second-layer support structure 1-2. The cuboid support consists of multiple vertical support columns 2-1 and crossbeams 2-2 connecting the support columns. The support surface 2-3 on the second-layer platform 2 is used to directly support the camera irregular shield. Its characteristic is that the calculation method includes the following steps: Step 1: Initialize the simulated camera shield support frame operating conditions. The specific process is as follows: (1) Construct a finite element simulation model of the camera support frame, and set the connection relationship between each component according to the actual structure of the support frame; (2) Assign preset material mechanical parameters to the materials in the simulation model; (3) Mesh the simulation model; (4) Apply loads and boundary conditions to the simulation model. The loads include at least: gravity loads, pressure loads simulating the weight of the camera, and seismic loads calculated based on seismic fortification requirements; and set analysis conditions including static and seismic dynamic conditions. (5) The weld strength of the welded structure of the support frame is checked; Step 2: Perform static analysis on the static working condition to obtain the deformation and stress distribution of the support frame under static load, and perform strength verification. Step 3: Perform dynamic analysis on the earthquake dynamic conditions. The dynamic analysis includes at least modal analysis and spectral analysis based on earthquake loads to obtain the dynamic response of the support frame under earthquake loads. Step 4: Combine the static analysis results with the dynamic analysis results to perform a comprehensive strength check on the support frame under seismic conditions.

[0035] Furthermore, in step one (1), when constructing the finite element simulation model, shell elements are used for modeling based on the ratio of the thickness to the length of the support frame structure, and common node processing is performed at the connection and intersection.

[0036] Supplementary Note 1: The advantages of using shell elements for modeling as described above: (1) "Using shell element modeling" is because the thickness of the support frame structure is much smaller than its length and width.

[0037] (2) Advantages of shell element modeling: A. High computational efficiency: Compared with solid elements, shell elements can greatly reduce the amount of computation and obtain results faster while ensuring accuracy. B. Applicable to thin-walled structures: Shell elements are particularly suitable for simulating thin plates, thin shells and other structures, and can accurately capture the bending deformation and stress distribution of the structure.

[0038] Furthermore, in step one, process (3), the main load-bearing structural components are divided using quadrilateral grids.

[0039] Further, in step one, process (4), the seismic load is calculated and determined according to GB 50011-2010 "Code for Seismic Design of Buildings", and the input of the seismic load is the seismic acceleration spectrum in the horizontal direction.

[0040] Supplementary Explanation 2: The reason for choosing the horizontal seismic acceleration spectrum as the primary input is as follows: (1) The essential distribution of seismic energy: During an earthquake, the energy released by the Earth's crust mainly propagates in the form of shear waves (S-waves), which cause horizontal shaking of the ground. The horizontal vibration component is usually much larger than the vertical component. Therefore, horizontal seismic force is the primary cause of structural damage.

[0041] (2) Characteristics of the structure itself: Gravitational stability: Buildings and support frames are designed to withstand vertically downward gravity (self-weight, equipment weight), and they have high strength and stiffness in the vertical direction (provided by load-bearing components such as columns and walls).

[0042] (3) Relative weakness in the horizontal direction: In comparison, the structure is much weaker in resisting horizontal thrust. Horizontal seismic forces are like suddenly shoving a standing person from the side, which can easily lead to instability, tilting, or collapse. For the precision camera support frame in a nuclear fusion device, horizontal swaying can cause optical alignment misalignment, component collisions, or structural failure, which must be a primary concern in the design.

[0043] Furthermore, in step two, the strength verification is performed using the fourth strength theory, and the maximum stress must be less than the design stress intensity of the material. The design stress intensity is obtained by dividing the yield strength of the material by the safety factor, which is 2.

[0044] Further, the weld strength verification in step one (5) is as follows: based on the stress state of the fillet weld, and based on the preset safety factor and the yield strength of the supporting structure base material, the allowable stress of the weld is calculated, and the allowable stress is selected as 108MPa.

[0045] Supplementary Note 3: Verification of the allowable stress of 108 MPa for the above weld: (1) In this embodiment, the structural components of the camera support frame are connected by fillet welds. The connection method is shown in Figure 1e. To ensure welding strength, the weld leg height is taken as 60% of the plate thickness, i.e., 8.5mm. The main stress direction of the camera support frame is vertical, and the main stress state of the weld is compressive stress. Referring to the weld strength calculation chapter of Volume 1 of the "Mechanical Design Handbook, Sixth Edition", the calculation formula for the fillet weld of the T-joint bearing pressure is: t = p / 2 al Where: P: bearing pressure (N); a: calculated thickness of the fillet weld (mm), generally taken as 0.7K. K is the weld leg height; l: weld length (mm); considering design safety, this welding check only considers the weld strength at the lowest point, as shown in Figure 1f.

[0046] (2) Using a conservative calculation, the load and the overall weight of the device are 24t, with a pressure of 20t. Since there are six welds at the bottom, each weld bears a pressure of 4t. The weld length is 586mm. The calculated thickness of the fillet weld is 5.95mm. Substituting these values ​​into the formula, the calculated welding stress is 5.62MPa.

[0047] (3) According to the "Stress Assessment Criteria" section, the allowable stress of the weld is 108 MPa. The calculated stress of the camera support bracket weld under self-weight and pressure conditions is much lower than this value; therefore, the structural strength meets the requirements. In summary, the weld strength of the camera support bracket under self-weight and pressure conditions meets the design requirements.

[0048] Furthermore, in step three, the spectral analysis is a response spectral analysis.

[0049] Furthermore, in step four, the comprehensive strength verification includes: combining static stress and dynamic response stress, and comparing the combined stress with a preset allowable stress limit; wherein the allowable stress limit is determined based on the ultimate strength and yield strength of the material under accident conditions.

[0050] Furthermore, the combined stress is 77.74 MPa, and the allowable stress limit is the smaller of 2.4 Sm and 0.7 Su, which is 331.2 MPa.

[0051] Supplementary Note 5: The allowable stress limit mentioned above is the smaller of 2.4Sm and 0.7Su, which is 331.2. Explanation of "MPa": (1) Allowable stress intensity limit evaluation criteria: Under accident conditions, the stress evaluation criteria are determined by two values: 2.4Sm and 0.7Su. Among them, Sm and Su represent different stress values.

[0052] (2) Calculation of 0.7Su: 0.7Su has been calculated, and the result is 339.5 MPa. Specifically, Su represents the tensile strength, which is 485 MPa. 0.7 * 485 MPa = 339.5 MPa; (3) Calculation of 2.4Sm: 2.4Sm = 2.4 * 138 = 331.2 MPa; Specifically: Definition and calculation of Sm: Sm is defined as the smaller value between 2Sy / 3 and 2Sy / 3. Here, Sy is the yield strength, with a value of 207 MPa. Therefore: =485MPa / 3=161.5MPa; 2Sy / 3 = 2 * 207 MPa / 3 = 138 MPa; Therefore, Sm takes the smaller value between 161.5 MPa and 138 MPa, so Sm = 138 MPa.

[0053] (4) Conclusion: The stress assessment standard will be the smaller of 2.4Sm=331.2MPa and 0.7Su=339.5MPa, i.e. 331.2MPa.

[0054] Furthermore, in the strength verification of step two and / or step four, the stress in the stress concentration area is linearized, and the sum of the membrane stress and bending stress obtained by the linearization process is compared with the design stress of the material.

[0055] Supplementary Note 6: Explanation of stress linearization treatment: The significance of stress linearization path lies in analyzing the location of critical stresses, that is, "where to look for stress".

[0056] It addresses the question of how to interpret stress at a given location. It uses "maximum values" to indicate the most critical points and "average values" and other linearized results to help you determine the safety of this complex stress state according to engineering specifications. This process serves as a crucial bridge between precise finite element calculations and engineering design standards. A detailed explanation follows: (1) A stress linearization path is a straight line or curve artificially defined within a structure (such as the welded component in the figure) used to assess stress. In engineering fields such as pressure vessels, pipelines, and welded structures, we are not only concerned with the point of highest stress, but also with the distribution of stress along the component wall thickness or critical sections. The linearization path is the path used for "sampling".

[0057] (2) The stress calculated by the finite element method varies continuously in space, especially at geometric abrupt changes (such as welds and openings), where complex peak stresses are generated. By defining a path that traverses these regions, we can extract the stress values ​​along this path for analysis. Figure 1g The code defines three paths: Path 1, Path 2, and Path 3, all of which traverse the weld area. This is typically used to assess the strength of the weld, as welds are weak points in a structure. Simply put, a "stress linearization path" is a line you select that focuses on analyzing stress changes.

[0058] Supplementary Note 7: Explanation of the three paths mentioned above: Path 1, Path 2, and Path 3 Figure 1g In the diagram, Path 1 is the path from A-1 to A-2, Path 2 is the path from B-1 to B-2, and Path 3 is the path from C-1 to C-2.

[0059] (3) Linearization Results: This is the key result obtained after simplifying (linearizing) the extracted complex stress distribution along the above path. The core idea of ​​linearization is to decompose the complex nonlinear stress distribution along the path into equivalent linearly distributed stress and self-balancing nonlinear stress. This is crucial for strength assessment according to standards (such as the ASME Boiler and Pressure Vessel Code).

[0060] (4) The results table typically contains two types of key values: Maximum value: This is the peak value of the original stress directly calculated by finite element analysis on the selected path. It reflects the true stress peak on the path and may contain severe stress concentrations. Average value: This is the average stress value calculated after linearizing the stress distribution on the path. It represents the "uniform tensile / compressive" stress components across the entire path cross-section. If the two differ significantly, it indicates the presence of a significant stress gradient or stress concentration on the path (peak stress is amplified by local geometry). Example 1: Verifying that the support frame meets stress and deformation requirements under a 20-ton load.

[0061] This embodiment verifies from several aspects that the support frame can meet the stress and deformation requirements under a 20-ton load: First, the support model is simplified for easier calculation; then, the load conditions are analyzed, including its own weight and the pressure load from the 20-ton camera shield; then, deformation and stress analyses are performed, which are divided into three types: deformation and stress analysis under static load conditions (see steps three and four); deformation and stress analysis under seismic load conditions (see steps five, six, and seven); and deformation analysis under comprehensive stress conditions (see step eight).

[0062] Step 1: Simplify the camera shield support model. (For example...) Figure 2 As shown, the simplified model is designed for ease of stress and seismic analysis. While retaining the main structural features, 1) the following were removed. Figure 1c 1) Local features such as connecting holes in the original model; 2) Solid features with a length-to-thickness ratio greater than 10, such as I-beams and stiffeners, are converted into shell elements, so that meshing based on hexahedral meshes can be performed based on shell elements. The above two simplification methods can significantly reduce the amount of calculation for stress analysis and seismic analysis, and reduce the calculation time, while ensuring the accuracy of the calculated structure.

[0063] Step 2: Simulate the static load conditions of a camera shield support frame with a load capacity of 20 tons. Figure 3 In the diagram, A represents its own weight, as indicated by the yellow arrow; B represents the fixed surface, as indicated by the blue support plate at the bottom; C and D represent the applied pressure load of 200,000 N. Figure 3 This describes the load conditions set during stress and seismic analysis. Based on actual operating conditions, the six blue support plates at the bottom serve as the fixed surfaces. A downward force of 200,000 N is applied to the top of the support to simulate the weight of a 20-ton camera. At the same time, the weight of the support itself is set, with a gravitational acceleration of 9.8 m / s² applied downwards.

[0064] Step 3: Simulate the overall deformation (mm) of the camera shield support frame structure under static load conditions with a load capacity of 20 tons. Figure 4 This describes the total structural deformation after static load analysis of the support structure, specifically the deformation of the support structure after applying a downward force of 200,000 N to the top of the support and considering its own weight. The deformation is categorized by color, with blue for the smallest deformation and red for the largest. The point of maximum deformation is located at a corner of the first-level platform support surface (red in the figure), with a maximum deformation of 0.73276 mm. Generally, deformation is calculated as 0.15% of the overall height of the support frame. The overall height of the support frame is approximately 4.26 meters, and deformation within 0.15% (i.e., within 6.4 mm) is permissible. Therefore, the maximum deformation of 0.73276 mm is much smaller than 6.4 mm, meaning the total structural deformation after static load analysis is acceptable.

[0065] Step 4: Simulate the stress cloud diagram of the camera shield support frame structure under static load conditions with a load of 20 tons. Figure 5 This diagram describes the stress distribution of the support structure after static load analysis. It shows the stress distribution after applying a downward force of 200,000 N to the top of the support and considering its own weight. The diagram uses different colors to represent the stress magnitude, with blue for the minimum and red for the maximum. The point of maximum stress is located on a connection surface between the first and second platforms (the red area in the diagram). The maximum stress of 71.864 MPa in the diagram is due to software system error, as 71.864 MPa is merely a stress abrupt change point. The actual maximum stress area is selected as 33.304 MPa, which is far less than the stress evaluation standard of 138 MPa.

[0066] Step 5: Simulate the vibration deformation (mm) of a 20-ton load-bearing camera shield support frame in the X direction under a magnitude 7 earthquake. Figure 6 This describes the structural deformation of the support structure in the X direction under a magnitude 7 earthquake. Based on the structural conditions and the load conditions of a magnitude 7 earthquake, the principal frequency in the X direction is calculated to be 14.847 Hz. The figure is divided into different colors according to the magnitude of the deformation, with blue for the smallest and red for the largest. At this vibration frequency, the maximum deformation of the support structure in the X direction is 0.82946 mm, which refers to the maximum amplitude change of the structure during vibration. The width of the support frame in the X direction is 2.8 meters, and 0.15% is 4.2 mm. 0.8294 mm is much smaller than 4.2 mm, therefore the maximum deformation of the support structure in the X direction of 0.82946 mm is within the allowable range. Step 6: Simulate the vibration deformation (mm) stress cloud diagram of a 20-ton load-bearing camera shield support frame in the Y direction under a magnitude 7 earthquake. Figure 7This describes the structural deformation of the support structure in the Y direction under a magnitude 7 earthquake. Based on the structural conditions and the load conditions of the magnitude 7 earthquake, the dominant frequency in the Y direction was calculated to be 23.949 Hz. The figure is divided into different colors according to the magnitude of the deformation, with blue for the smallest and red for the largest. At this vibration frequency, the maximum deformation of the support structure in the Y direction is 1.6179 mm, which refers to the maximum amplitude change of the structure during vibration. The length in the Y direction is approximately 3.3 meters, and 0.15% of this is 4.95 mm. Deformation within 4.95 mm is permissible. Since the maximum deformation of the support structure in the Y direction of 1.6179 mm is much smaller than 4.95 mm, the simulation results indicate that a maximum deformation of 1.6179 mm in the Y direction for a 20-ton load-bearing camera support frame is permissible.

[0067] Step 7: A schematic diagram simulating the stress of a 20-ton load-bearing camera shield support frame under seismic load during a magnitude 7 earthquake. Figure 8 This figure describes the stress distribution of the support frame structure under a magnitude 7 earthquake. Based on the structural conditions and the load conditions of the magnitude 7 earthquake, the stress on the support structure affected by the earthquake is calculated, as shown in the figure. The figure is divided into different colors according to the magnitude of the stress, with blue representing the minimum and red representing the maximum. Under the conditions of a magnitude 7 earthquake, the maximum stress of 12.296 MPa in the figure is a software systematic error, because 12.296 MPa is only a stress abrupt change point. The actual maximum stress range is selected as 10.93 MPa, which is much smaller than the allowable stress limit of 331.2 MPa.

[0068] Step 8: Simulate the overall stress cloud diagram of the camera shield support frame with a load-bearing capacity of 20 tons under the combined force. Figure 9 This figure describes the stress distribution of the support structure under the combined effects of its own weight, applied loads, and a magnitude 7 earthquake. The stresses on the support structure affected by the earthquake, calculated based on the load conditions, are shown in the figure. The stresses are categorized by color according to their magnitude, with blue representing the minimum and red representing the maximum. The maximum stress of 77.744 MPa is a software system error, and the maximum stress point is a stress distortion point. The actual maximum stress region is selected at 69.106 MPa, which is far less than the allowable stress limit of 331.2 MPa.

[0069] It should be emphasized that the above specific embodiments are merely explanations of the present invention and are not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to the above embodiments without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device, the method being based on a horizontal irregularly shaped camera support frame, the irregularly shaped support frame comprising: An irregular topology first-floor platform (1) and a second-floor platform (2) arranged on the first-floor platform; the irregular topology first-floor platform is provided with a first-floor support structure (1-1) and a second-floor support structure; the first-floor support structure (1-1) is composed of multiple irregular topology and vertically arranged main support columns (1-1-1) and lower connecting beams (1-1-2) connecting the main support columns; the second-floor support structure is set above the first-floor support structure (1-1) and is composed of multiple irregular topology main support columns. The support column (1-1-1) consists of multiple tops and at least two interconnected rectangular frame units (1-2-1) arranged on the multiple tops; the second-level platform (2) is a cuboid support body, which is fixedly installed on the second-level support structure; the cuboid support body consists of multiple vertical support columns (2-1) and crossbeams (2-2) connected between the support columns; the support surface (2-3) on the second-level platform (2) is used to directly support the horizontal camera irregular shield; The calculation method is characterized by the following steps: Step 1: Initialize the simulated horizontal camera shield support frame operating conditions. The specific process is as follows: (1) Construct a finite element simulation model of the horizontal camera support frame, and set the connection relationship between each component according to the actual structure of the support frame; (2) Assign preset material mechanical parameters to the materials in the simulation model; (3) Mesh the simulation model; (4) Apply loads and boundary conditions to the simulation model. The loads include at least: gravity loads, pressure loads simulating the weight of the camera, and seismic loads calculated based on seismic fortification requirements; and set analysis conditions including static and seismic dynamic conditions. (5) The weld strength of the welded structure of the support frame is checked; Step 2: Perform static analysis on the static working condition to obtain the deformation and stress distribution of the support frame under static load, and perform strength verification. Step 3: Perform dynamic analysis on the earthquake dynamic conditions. The dynamic analysis includes at least modal analysis and spectral analysis based on earthquake loads to obtain the dynamic response of the support frame under earthquake loads. Step 4: Combine the static analysis results with the dynamic analysis results to perform a comprehensive strength check on the support frame under seismic conditions.

2. The method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device according to claim 1, characterized in that, In step one, when constructing the finite element simulation model, shell elements are used for modeling based on the ratio of the thickness to the length of the support frame structure, and common node processing is performed at the connection and intersection.

3. The method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device according to claim 1 or 2, characterized in that, In step one, process (3), the main load-bearing structural components are divided using quadrilateral grids.

4. The method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device according to claim 1, characterized in that, In step one, process (4), the seismic load is calculated and determined according to GB 50011-2010 "Code for Seismic Design of Buildings", and the input of the seismic load is the seismic acceleration spectrum in the horizontal direction.

5. The method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device according to claim 1, characterized in that, In step two, the strength check is performed using the fourth strength theory, and the maximum stress must be less than the material's design stress strength. The design stress strength is obtained by dividing the material's yield strength by a safety factor, which is 2.

6. The method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device according to claim 1, characterized in that, The weld strength verification in step 1(5) is specifically as follows: based on the stress state of the fillet weld, and based on the preset safety factor and the yield strength of the supporting structure base material, the allowable stress of the weld is calculated, and the allowable stress is selected as 108MPa.

7. The method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device according to claim 1, characterized in that, In step three, the spectral analysis is a response spectral analysis.

8. The method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device according to claim 1, characterized in that, In step four, the comprehensive strength verification includes: combining static stress and dynamic response stress, and comparing the combined stress with a preset allowable stress limit; wherein the allowable stress limit is determined based on the ultimate strength and yield strength of the material under accident conditions.

9. The method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device according to claim 8, characterized in that, The combined stress is 77.74 MPa, and the allowable stress limit is the smaller of 2.4 Sm and 0.7 Su, which is 331.2 MPa.

10. The method for calculating the seismic stress of a camera shield support frame for a nuclear fusion experimental device according to claim 1, characterized in that, In the strength check of step two and / or step four, the stress in the stress concentration area is linearized, and the sum of the membrane stress and bending stress obtained by the linearization process is compared with the design stress of the material.

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