A gun metal rod 2 on diameter screwed at the ends, passes through a steel tube \(2.5 \mathrm{~cm}\) internal and \(3 \mathrm{~cm}\) external diameter. dimameter. The temperature of the whole assembly is raised to \(130^{\circ} \mathrm{C}\) and nuts on the rod are screwed lightly home on the ends of the tube. Find. the stress in the rod and the tube when the common temperature has fallen to \(15^{\circ} \mathrm{C}\).

For gun meter : \(\infty=18 \times 10^{-6}{ }^{\circ} \mathrm{C}, E=906 \mathrm{GPa}\), For steel : \(\propto=12 \times 10^{-6} /{ }^{\circ} \mathrm{C}, E=210 \mathrm{GPa}\).