Past exam of the materials science course of the University of Cambridge / 2019 / Paper 1 / 5 / d / Solution

The number and spacing of primary slip planes remain fixed, so the length projected on their normal is invariant: $l_0\cos {\varphi }_0=l_1\cos {\varphi }_1$. The initial and boundary loading directions are $[514]$ and $[211]$, respectively. With normal $[1\bar{1}1]$,ThereforeThis is engineering plastic strain in the ideal geometric model; its corresponding logarithmic strain is $\ln (4/\sqrt{7})$. Elastic extension and changes in slip resistance are neglected, as required by this construction.