The Effect Of Voids On Mechanical Properties For The Multistage Cables Of Four Kinds Of Superconducting Coils

International Thermonuclear Experimental Reactor(ITER)project is one of the largest and most far-reaching international scientific research cooperation projects in the world.The tokamak device in ITER is a fully superconducting magnet device that can continuously generate a huge magnetic field to achieve nuclear fusion reactions.Tokamak magnets contain four kinds of superconducting coils which are made using superconducting strands twisted by helical winding ways.This winding pattern results in a void in the coils.The void will affect various properties of the superconducting coil in actual operation.This thesis studies the effect of voids on the mechanical properties of superconducting cables.The main contents are as follows:Firstly,the parametric equations of four kinds of superconducting coils(Toroidal Field Coils,Central Solenoid Coils,Correction Coils,Poloidal Field Coils)are established.Using the established parametric equations,the geometric models of the four kinds of superconducting coils can be built,which are a foundation for the subsequent research.Secondly,the definition of void of superconducting cable is given.The theoretical model of equivalent tensile stiffness for various coils under higher stages structures are derived.The variation of winding number and voids and the effect of voids on the equivalent tensile stiffness are analyzed by designing winding modes of multi-stage cables.In addition,the corresponding numerical model is established to verify the theoretical analysis results.The results show that the theoretical model is in good agreement with the numerical results,which demonstrates the correctness of the theoretical model.Finally,we analyzed the variation of equivalent elastic modulus of TF fifth-stage cable with the void by establishing a numerical model of TF fifth-stage cable,and compared with the corresponding experimental results.The results show that our model results are in good agreement with the experimental results,which certify the fifth-stage cable model adopted by us is reasonable.On this basis,the method of establishing the fifth-stage cable model is extended to other kinds of coils.By designing the corresponding cable winding mode,the complete structure of the four kinds of coils is analyzed accordingly,which is a good attempt to analyze the fifth-stage cable structure for the superconducting coils.