Mechanical-electro Coupling Analysis Of Multifilamental Twisted Superconductors

The thesis mainly focuses on mechanical-electro coupling performance in multifilamental twisted Nb₃Sn superconducting strands.Based on Maxwell equations,electromagnetic constitutive relation and E-J power law,the governing equation is obtained.And then the electromagnetic characteristics of VAC strand,LMI strand and multifilamental twisted Nb₃Sn superconductors are studied under different work conditions.In mechanical analysis,equivalent elastic parameters for the hybrid composite of Nb₃Sn strand are obtained by mesomechanics,which are compared with numerical simulation results to verify the 3D model.Eventually,a linear E-J relation is exploited,instead of aforementioned nonlinear power law.Based on this simplification,the influence of the strain on the distribution of electro-magnetic field,transport mode and transport capacity are studied.Meanwhile,the expression between coupling loss and strain is established.The following conclusions could be drawn from the research.The contact resistance has significant influence on the current flowing pattern in the transverse orientation.The currents mainly distribute in the superconductors in the longitudinal direction,and also flow along the path of them.The coupling loss is proportional to the square of twist pitch and magnetic amplitude,while increasing with the reduction of n.External force would affect the transport mode and capacity of the strand.The greater force would give rise to dramatical strain,and redistribution of the current.Meanwhile,the transport capacity has noticeabledeterioration.Therefore,theelectro-magneticdistinctionunder mechanical-electro coupling load could provide guidance to the design of superconducting magnet.The designer could appropriately decrease the twist pitch or external load to improve the transport capacity of the superconducting system.