Analysis Of Equivalent Modulus And Mechanical Properpties Of CICC Strands

The International Thermonuclear Experimental Reactor(ITER)tokomak is one of the fusion machines used to limit fusion reactions in hot plasma.Confinement of plasma is possible using different superconducting magnets namely Toroidal Field(TF)Coil,Poloidal Field(PF)Coil and Central Solenoid(CS)Coil.These large superconducting magnets are constructed with in-pipe cable conductors(CICC)whose working current runs up to 68 kA and magnetic field is up to 12 T.CICC,Superconducting Cable,is gradually twisted by subcables at all levels.this kind of complex twisted structure makes it has the advantages of high stability,good self-support,large current transmission capacity,low AC loss,high electrical and thermal stability,high voltage resistance,etc.However,it also brings about various mechanical deformation in the design,preparation and operation of CICC superconducting cable.Therefore,the research on the mechanical properties of subcables at all leverls in CICC superconducting cable is helpful to optimize the design of superconducting magnets.This paper is based on homogenization theory and slender rod theory,the equivalent Young's modulus theory of first-order sub-cables is extended to fourth-order sub-cables,and a theoretical model for predicting the equivalent Young's modulus of multi-stage sub-cables of CICC superconducting cables is established.Secondly,the effect of winding cycles on the equivalent Young's modulus of each sub-cable is analyzed.Then the finite element model of the first-order to fourth-order sub-cable is established.The reliability of the theoretical model is verified by comparing the arithmetic solutions of the equivalent modulus with different winding cycles at all levels of sub-cables with theoretical solutions.It was found that the variation of the equivalent Young's modulus of the sub-cables of CICC superconducting cable by the number of winding cycles provides a basis for the rational design of winding patterns.And then on the basis of the theoretical model of the mechanical response of multilayer spiral material,the theoretical model of the maximum normal stress of Nb3 Sn strand in CICC sub cables was established.The relationship between the axial strain and the maximum normal stress of the strand is studied.The relationship between the axial strain and the maximum normal stress of the strand is studied.The effect of the helical angle of multistage subcable on the maximum normal stress of the strand is analyzed.At the same time,the simplified finite element beam-shell model of the subcables is established,and the theoretical and numerical solutions of the maximum normal stress of the strand in each sub-cables are compared to verify the correctness of the theoretical model.It is concluded that they have approximate linear relationship between the axial strain and the maximum normal stress of the strand.With the decrease of helical angle,the maximum normal stress of multistage subcable decreases gradually.In this paper,the mechanical behavior of sub-cables in CICC superconducting cable is studied.