title: Effects of cold-treatment and strain-rate on mechanical properties of NbTi/Cu superconducting composite wires.
abstract: During design and winding of superconducting magnets at room temperature, a pre-tension under different rate is always applied to improve the mechanical stability of the magnets. However, an inconsistency rises for superconductors usually being sensitive to strain and oversized pre-stress which results in degradation of the superconducting composites' critical performance at low temperature. The present study focused on the effects of the cold-treatment and strain-rate of tension deformation on mechanical properties of NbTi/Cu superconducting composite wires. The samples were immersed in a liquid nitrogen (LN2) cryostat for the adiabatic cold-treatment, respectively with 18-hour, 20-hour, 22-hour and 24-hour. A universal testing machine was utilized for tension tests of the NbTi/Cu superconducting composite wires at room temperature; a small-scale extensometer was used to measure strain of samples with variable strain-rate. The strength, elongation at fracture and yield strength of pre-cold-treatment NbTi/Cu composite wires were drawn. It was shown that, the mechanical properties of the superconducting wires are linearly dependent on the holding time of cold-treatment at lower tensile strain-rate, while they exhibit notable nonlinear features at higher strain-rate. The cold-treatment in advance and the strain-rate of pre-tension demonstrate remarkable influences on the mechanical property of the superconducting composite wires.
authors.affiliation: Key Laboratory of Mechanics on Environment and Disaster in Western China, The Ministry of Education of China, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, 730000 P.R. China ; Institute of Modern Physics of Chinese Academy of Science, Lanzhou, 730000 P. R. China.
authors.forename: Mingzhi
authors.initials: M
authors.lastname: Guan
authors.affiliation: Key Laboratory of Mechanics on Environment and Disaster in Western China, The Ministry of Education of China, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, 730000 P.R. China.
authors.forename: Xingzhe
authors.initials: X
authors.lastname: Wang
authors.affiliation: Key Laboratory of Mechanics on Environment and Disaster in Western China, The Ministry of Education of China, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, 730000 P.R. China.
authors.forename: Youhe
authors.initials: Y
authors.lastname: Zhou
keywords: Effect of cold-treatment; Mechanical property; NbTi/Cu composite wires; Strain-rate; Tensile response