ELECTRO-MECHANICAL PROBLEMS IN SUPERCONDUCTING COILS Giorgio Zavarise 1 Daniela Boso 2 1 Dipartimento di Ingegneria Strutturale e Geotecnica, Politecnico di Torino Corso Duca degli Abruzzi, 24, I-10129, Torino, Italy 2 Dipartimento di Costruzioni e Trasporti, Università di Padova Via F. Marzolo, 9, I-35131, Padova, Italy SUMMARY: This paper presents the most recent research activity performed by the authors in the field of contact problems in superconducting coils. The research is related to the development of the coils for the experimental nuclear fusion machine “ITER”. The results here summarized are related to the inter-strand electromechanical behavior and its dependence on the electromechanical contact resistance. The effects related to the distribution of the superconducting zones within the wire, and of the mechanical properties of the materials are presented. Moreover a microscopical formulation for a more accurate treatment of the contact resistance is formulated. The adopted strategy is based on the statistical characterization of the surface roughness and the electro-mechanical behavior of the contacting asperities. In such a way the contact resistance is build up starting from a physical background. KEYWORDS: contact mechanics, superconducting coils, coupled problems, thermal constriction resistance, electrical constriction resistance, mechanical constriction resistance, micromechanics, INTRODUCTION In the current design of the ITER nuclear fusion machine the Toroidal Field coils (TF) are made of Nb 3 Sn multifilamentary strands, while the Poloidal Field coils (PF) are manufactured with NbTi strands, since the brittleness of Nb 3 Sn requires a relatively expensive manufacture process, and the PF coils occupy a field region where NbTi strands can be used [1]. Hence both the super conducting alloys behaviour must be investigated. This research activity regards mainly the investigation of the NbTi multifilamentary strands. This kind of systems present a strong interaction among the electromagnetic, the thermal and the mechanical field. To predict the cable operation limits, a complex solution of 3D time- dependent coupled problems (in the electromagnetic, thermal and mechanical fields) must be found.