고체역학 (Beer) — Stress and Strain—Axial Loading: Problem 2.125

2.125 The aluminum rod $ABC$ ($E = 10.1 \times 10^6 \text{ psi}$), which consists of two cylindrical portions $AB$ and $BC$, is to be replaced with a cylindrical steel rod $DE$ ($E = 29 \times 10^6 \text{ psi}$) of the same overall length. Determine the minimum required diameter $d$ of the steel rod if its vertical deformation is not to exceed the deformation of the aluminum rod under the same load and if the allowable stress in the steel rod is not to exceed 24 ksi.