= Solution
For the <aluminium> alloy, write $K_{IC,\rm Al}$ and $\sigma_{y,\rm Al}$ for the appropriate data-book properties at the relevant material state and <temperature>. The yield-limited screening bounds from part(c), with $r\simeq0.70\,\mathrm m$, are
$$
\boxed{t_{\max,\rm Al}=\frac1\pi
\left(\frac{K_{IC,\rm Al}}{Y\sigma_{y,\rm Al}}\right)^2,
\qquad t_{\rm yield,\rm Al}\simeq\frac{7\,\mathrm{MPa\,m}}{\sigma_{y,\rm Al}}.}
$$
For $K$ in $\mathrm{MPa\sqrt m}$ and $\sigma_y$ in $\mathrm{MPa}$, the numerical substitutions are $t_{\max}(\mathrm{mm})=318.31[K/(Y\sigma_y)]^2$ and $t_{\rm yield}(\mathrm{mm})=7000/\sigma_y$.
A high-strength alloy's large yield <stress> can require a small allowable leak-before-break thickness even when its minimum pressure thickness is modest. FCC structure generally favors low-temperature plasticity, but does not by itself establish the alloy's <fracture toughness>, weld performance, corrosion behavior or fatigue resistance.
\b[TODO: numerical thickness cannot be completed without the 2018 NST Data Book values and alloy condition, which are unavailable.] The accessible Engineering2011/revised2019 book is not confirmed as the supplied edition; generic <aluminium> property ranges are not substituted as if they were the exam's values.
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