Plastic Limit Structure Analysis Of In-wall Shielding Block

The vacuum vessel with a double-shell structure of International Thermonuclear Experimental Reactor (ITER) device is the operating place of nuclear fusion. The in-wall shielding (IWS) set in the inside of the double-shell is composed of in-wall shielding blocks, which are used for shielding neutrons produced by fusion reactions. In normal operating conditions of nuclear fusion, the in-wall shielding block will be subject to a variety of load force. Such as the bolt preload, the gravity of the structure, eddy current electromagnetic force, the magnetization electromagnetic force (ferromagnetic material), possible seismic load, vertical displacement event and so on. Therefore, the structural safety and reliability of the in-wall shielding block and the whole in-wall shielding have especially importance.The finite element simulation method must be used to check the structure strength in the detail design of in-wall shielding block, as the in-wall shielding block is a complex assembly. In most of the engineering analysis, finite element elastic analysis application is more extensive. But the classification of the stress is much difficult in the post-processing of the elastic analysis. The results of the analysis are inevitably more conservative, while the plastic limit analysis to avoid this problem.The loads and boundary conditions of the single component are hard to determine in the finite element analysis of in-wall shielding block. In order to accurately analyze and calculate the forces of in-wall shielding block, the overall structure finite element analysis is adopted. And, the contacts are set between components concerned about Therefore, the pre-process of the finite element model is much complex, this article will be detailed.First, the assembly and the detailed design of the components of in-wall shielding block have been introduced. Then the finite element elastic analysis is operated to the in-wall shielding block. And, the structure strength of in-wall shielding block is checked based on elastic analysis. The results show that stresses of some components are much larger than the allowable stress. For this reason, this paper focuses on the plastic limit analysis of in-wall shielding block. Using the true stress-strain curves is realistic for plastic limit analysis, as the relationship of materials stress-strain are complex curves. In order to simplify the calculation, the materials are assumed as the elastic-perfectly plastic material. The real loads are loaded into the in-wall shielding block to a certain load factor. The load factor is enlarged until convergence failure. Extracting the results and drawing the load-strain curves, then, check the results of plastic limit analysis according to the criteria.The results of plastic limit analysis show that the strain did not reach the strain value of the limit load. Therefore, the real load is smaller than the limit load, and, the structural strength of in-wall shielding block is safe. The plastic limit analysis, therefore, fully explores the potential of the material. Not only the materials are saved, but also the redesign of the in-wall shielding block is avoided. Plastic limit analysis method provides references to highly nonlinear plastic limit analysis with multi-contact.Correspondingly, many contacts are set in the plastic limit analysis of in-wall shielding block. This plastic limit analysis provides convincing references to highly nonlinear plastic limit analysis with multi-contact...