Mechanical influence on long-term dielectric performance of insulants

The dielectric properties of insulating materials used in superconducting m agnets were reviewed; especially the degradation of the dielectric properti es of the insulating materials that were used under loaded conditions at cr yogenic temperatures was paid attention. It was clarified that the drastic degradation was mainly brought by the introduction of mechanical defects to the insulating materials. The relationship between mechanical defects and mechanical loading was also discussed. Long-term mechanical properties such as creep and fatigue were surveyed and the mechanical defects induced by c reep and fatigue were estimated. The mechanical influence on long-term diel ectric properties of insulating materials was discussed. (C) 1998 Elsevier Science Ltd. Ail rights reserved.