Suspension of the W7-X coils
Introduction
The process of general design definition of the central support structure is completed, the particular components have been already ordered and are in process to be manufactured. The analysis and design of the central support structure is a long term task with considerable man-power quota. The milestones to develop the support structure have been published in several journals [1], [2], [3]. The aim of the present investigations is to explain the coherence between particular elements inside the coils support structure which increase the reliability of the machine. Especially the most stressed part of the structure will be taken under consideration.
Inside of the coil support structure, the so called central support elements or extensions are the most stressed part of the structure. These elements (two per coil housing) connect the coil housings with the support ring. These elements of the structure consist of two parts (one belongs to the coil housing and the other to the support ring) which have to be joined together. The loading at the particular central support elements is in a high degree nonuniform. It can even happen, a compressive stress is locally occurs in spite of the fact that the global tension load is acting on the body. This behaviour is the result of a interaction of particular neighbouring parts in the support structure, which should be superimposed with the global loading. The support system of the coils under loading can be imagined as a quasi mechanism. The investigation of the special effects inside the structure postulates some modifications of the existing model which is described in [4]. These modifications lead to a further complexity of the model in terms of higher nonlinear formulations. Consequently, the whole analysis becomes more complex and needs more effort.
Section snippets
Description of the FE-model
The FE-Model is reduced to 1/10 of the whole system by the introduction of special symmetry boundary conditions [5]. The main parts of the current concept are shown in Fig. 1, Fig. 2.
Most of all modification of the FE-model described in [4] have been performed in the area marked in Fig. 2 as connecting zone. These modifications have been realised according to the conceptual design shown in Fig. 3. As a result, the solid connection between support ring and coil housing have been changed by the
Results and discussion
The aim of the FE-analysis is to explain the coherence between particular elements inside the coil support structure and the actual behaviour of the connecting screws of the central support elements during operation. The connecting flanges have been modelled on the basis of the principle shown in Fig. 3.
The deformations of the structure especially in the zone of the central support elements are shown in Fig. 4. The detail “A” shows quantitatively the displacements at the flange of the top
Conclusions
The FE-model based on a half module to represent the whole WENDELSTEIN-7X (W7-X) coil arrangement with the special preparation of connecting elements between coil housing and central support ring have been realised. The centre of interest are the forces and moments at the connecting elements (screws) which join the flanges at the central support elements. Two different formulations of the connecting possibilities—screws and welding—have been analysed. The differences, caused by introduction the
Acknowledgements
The authors are thankful to Jörg Tretter and Franz Kerl for his help during the preparation of this paper.
References (5)
- et al.
Nonlinear global–local finite element analysis of a future plasma fusion experiment
- J. Simon-Weidner, N. Jaksic, E. Harmeyer, On mechanical stress in large helias coil systems and the influence of...