Full-scale friction test on tilted sliding bearings for Wendelstein 7-X coils

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• 作者：Dag Hathiramani ; Johann Lingertat ; Paul van Eeten ; Manfred Sochor ; Michael Laux ; Victor Bykov ; Felix Schauer ; Bernd Heinemann ; Patrick Junghanns ; Albrecht Brenner ; Christoph Zauner ; Harald Langer
• 关键词：Stellarator ; Wendelstein 7-X ; Mechanical structure ; Narrow support elements ; MoS₂ lubrication
• 刊名：Fusion Engineering and Design
• 出版年：2009
• 出版时间：June 2009
• 年：2009
• 卷：84
• 期：2-6
• 页码：899-902
• 全文大小：634 K

文摘

Narrow support elements (NSEs) are sliding bearings between neighboring non-planar coils of the Wendelstein 7-X magnet structure. Here an aluminium bronze pad slides with its spherical surface against the plane steel housing of the adjacent coil. Both sliding surfaces are coated with MoS₂. Electromagnetic forces of >1 MN, relative movements of few millimeters as well as tilting of up to 1° with respect to the adjacent surfaces are expected. Under these conditions mechanical disturbances like stick–slip have to be avoided since they may initiate quenches of the superconducting coils. Two types of pads are employed with diameters of 73 mm and 60 mm, designed for forces of 1.5 MN and 1.0 MN, respectively. The functionality of a 60 mm pad narrow support element was shown on a full-scale friction test including a relative tilting of 1° at full load. The expected operating cycles of Wendelstein 7-X were simulated at different normal forces. Two experiments were performed with pad material according to the specification and one with pad material not according to the specification. More than 4800 sliding cycles were performed at over-loads of up to 1.5 MN and sliding strokes of 2 mm. The tests were executed in cryo-vacuum at 77 K and accompanied by detailed FE simulations. Smooth sliding for more than 4000 load cycles could be shown at maximal normal forces corresponding to the NSE design load, which is the nominal W7-X load plus 30 % safety factor. Applying normal forces fare above the design load, the coefficient of friction started to increase significantly and stick–slips occurred after about 200 load cycles.