A prediction of the stress state in Nb3Sn superconducting composites

Abstract

The critical current Ic as a function of applied tensile strain depends upon the residual stress state that exists in Nb3Sn bronze-process composite conductors after cooling from the reaction temperature to 4.2 K. This paper presents a simple analytical method to predict the residual stress state and the stress-strain curves of Nb3Sn composites at 4.2 K. The method requires only a prior knowledge of the volume fraction of the composite components and the percentage of Nb converted to Nb3Sn. Experimental results and analytically derived values are compared and good agreement is generally found.

Elastic Anisotropy in Multifilament <inline-formula> <tex-math notation="TeX">$\hbox{Nb}_{3}\hbox{Sn}$</tex-math></inline-formula> Superconducting Wires

“…Nevertheless, the higher E-moduli of the RRP wire and filaments with respect to those of PIT wire and filaments could be explained partly by the higher Nb3Sn E-modulus in axial direction in the RRP wire. Similar RT Nb3Sn E-moduli have been published elsewhere [22,23,24]. The Young's modulus obtained by averaging the single crystal data from [12] dramatically harden below the phase transformation temperature TM, while the moduli obtained from ultrasonic data exhibit a smooth profile with almost no hardening below TM as demonstrated in [25].…”

Strain Gauge Method for Evaluating a Three-Dimensional Residual Strain State in ${\rm Nb}_{3}{\rm Sn}$ Wires

“…However, the detailed mechanism of the strain effect for wires still remains unsettled. Moreover, such strain sensitivity depends on the wire manufacturing process and the wire architecture [3]. Therefore, there is no practical model that unit- Manuscript edly shows the relation between superconducting properties and strains.…”

Electromechanical properties of superconductors for DOE fusion applications

“…4, the stress that causes a given amount of I c degradation at 9 T is almost two times smaller for transverse stress than for axial stress. In contrast, this ratio for Nb 3 Sn at 10 T is approximately five [3], As indicated in Fig. 4 Fig.…”

“…Fig. 3 ( a ) over a wide range shows that the stress which causes a given amount of critical-current degradation at 10 T is generally about seven times less for transverse stress than for axial stress. This ratio will increase at higher magnetic fields Figure 3(b) shows the critical current of a piece of the same conductor which was flattened to a rectangular cross section 0.38x0.76 mm prior to reacting.…”

“…I Bronze process Nb 3 $n I c -vs -stress curves at 8 and 10 T. The critical current has been normalized by its maximum value, Icm. The "Unloaded" data points indicate the measured I c at 10 T after unloading the sample from the indicated stress level. Internal tin process NbjSn I c -vs-stress curves at 7,8, and 9 T. The critical current has been normalized by its maximum value, Icm.…”