(Solved): The aluminum rod (E1=69GPa) is reinforced with a firmly bonded steel tube (E2=202GPa). The di ...

The aluminum rod $\left(E_1=69\mathrm{GPa}\right)$ is reinforced with a firmly bonded steel tube $\left(E_2=202\mathrm{GPa}\right)$. The diameter of the aluminum rod is $d=23\mathrm{mm}$ and the outside diameter of the steel tube is $D=45\mathrm{mm}$. The length of the composite column is $L=750\mathrm{mm}$. A force $P=88\mathrm{kN}$ is applied at the top surface, distributed across both the rod and tube. Determine the normal stress in the aluminum rod. Hint: remember that sign convention.