Effects of cold-treatment and strain-rate on mechanical properties of NbTi/Cu superconducting composite wires.

Mingzhi Guan,Youhe Zhou,Xingzhe Wang

doi:10.1186/s40064-015-0860-7

Mingzhi Guan, Youhe Zhou + Show 1 more

Open Access

https://doi.org/10.1186/s40064-015-0860-7

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Journal: SpringerPlus	Publication Date: Feb 13, 2015
Citations: 13	License type: CC BY 4.0

Affiliation: Institute of Modern Physics, Lanzhou University

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.

Highlights

Superconductors have been shown to possess a variety of promising applications in electricity, medical, electronics fields, especially in particle accelerators with superconducting magnets (Allain et al 2013)
Some primary mechanical properties, including the strength, elongation at fracture and yield strength, were extracted and reported. Based on these data generated on the superconducting samples with the diverse holding time of pre-cold-treatment and strain rate, we can draw the conclusion that the nonlinear features for the multifield effect on the NbTi/Cu composite wires’ mechanical behaviors are in existence, provided that a high strain rate condition can be achieved
The observations exhibit that the ultimate tensile strength, elongation and yield strength all depend simultaneously upon the holding time of cold-treatment and tensile strain rate

Summary

Introduction

Superconductors have been shown to possess a variety of promising applications in electricity, medical, electronics fields, especially in particle accelerators with superconducting magnets (Allain et al 2013). The major tensile mechanical parameters of the pre-treated NbTi/Cu composite wire, such as ultimate tensile strength and elongation to fracture, yield strength, were measured at cryogenic temperature in the strain rate range of 10−4 ~ 10−2 s−1 and room temperature.

Results

Conclusion