Method for determining the irreversible strain limit of Nb3Sn wires

Published

June 6, 2011

Author(s)

Loren F. Goodrich, Najib Cheggour, Xifeng Lu, Jolene D. Splett, Theodore C. Stauffer, Bernard J. Filla

Abstract

We have defined a rigorous and reliable method for determining the irreversible strain limit of Nb₃Sn wires. The critical current (I_c) is measured as a function of applied longitudinal strain (ε), I_c(ε), at one magnetic field and a temperature of 4.0 K. The sample is loaded and partially unloaded at progressively higher strain levels to determine the irreversible strain limit, ε_irr, which is defined as the maximum loaded strain where I_c is still reversible. Our method uses a polynomial fit of the loaded I_c(ε) to derive the I_c residuals for the loaded and unloaded points that are analyzed to determine the limit of irreversibility. The effect of varying the amount of strain unloading was also studied. The possibility and issues of using the strain dependent n-value (indicating the steepness of the electric field-current, E-I, curve) to determine ε_irr are discussed. The method presented here has proven to be appropriate and the ε_irr results are repeatable for many types of commercial Nb₃Sn wires. This method can also be more generally used to determine ε_irr for any brittle low-temperature or high-temperature superconducting material.

Citation

Superconductor Science and Technology

Volume

24

Pub Type

Journals

Keywords

Axial strain, critical current, irreversible strain limit, niobium-tin, n-value

Citation

Goodrich, L. , Cheggour, N. , Lu, X. , Splett, J. , Stauffer, T. and Filla, B. (2011), Method for determining the irreversible strain limit of Nb₃Sn wires, Superconductor Science and Technology (Accessed October 27, 2025)