3. A steel bar is connected to an aluminum bar as shown below. At 70 °F, the stresses in the
steel and the aluminum bars are zero. Calculate the stresses in the steel and in the aluminum
when the temperature rises to 150 °F. Indicate whether the stresses are tensile or
compressive. The properties of the steel and the aluminum are given below. The cross-sectional
areas of the steel and the aluminum are the same. (20 pts.)
Steel
$E_s=30.0 \times 10^6$ psi $\alpha_s=6.5 \times 10^{-6}/^\circ F$
Aluminum
$E_{al}=10.0 \times 10^6$ psi $\alpha_{al}=12.8 \times 10^{-6}/^\circ F$
6"
8"
Steel
Aluminum
