Figure 3.

Minimum-dataset extrapolation tests for the Durham fitting equation, utilizing the very large OST-RRP^® Nb₃Sn dataset. Solid curves show the 12 K results extrapolated from the minimum dataset at 0.0% strain and 4.07 K (i.e., the dashed crosscut in figure 1)., Data points show the measured $I_{\text{c}}$ values. (a) Extrapolation results for the Durham fitting equation parameterized with the Durham $h(t)$ model (i.e., $\mu =2$) and Polynomial $b_{\text{c}2}(\epsilon )$ (appendix B.3 of Part 2), (b) Extrapolation results for ESE, also applied with the same Durham $h(t)$ and Polynomial $b_{\text{c}2}(\epsilon )$. In figure (b) the percentage extrapolation errors at individual data points at high compressive strains are reduced to as little as 1/30th to 1/40th the size of those in figure 3(a) (note the vertical scales are logarithmic). The main differences between the two figures is that in 3(b): (1) the cross-link parameter is set to the constant $w=3.0$, instead of the Durham default value $w=2.2$; and (2) the strain exponent $s$ is freed to be a fitted parameter, instead of fixed at $s=1.0$.