A composite bar made up of aluminium and steel is held between two supports as shown in Fig. 13.53.The bars are stress free at a temperature of \(38^{\circ} \mathrm{C}\). What will be the stresses in the two bars when the temperature is \(21^{\circ} \mathrm{C}\), if \((a)\) the supports are rigid, and \((b)\) the supports come nearer to each other by \(0.1 \mathrm{~mm}\).

For steel : \(\propto=11.7 \times 10^{-6} /^{\circ} \mathrm{C}, E=210 \mathrm{GPa}\).
For aluminium: \(\propto=23.4 \times 10^{-6} /{ }^{\circ} \mathrm{C}, E=74 \mathrm{GPa}\).

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50 mm Steel 0.6 m 25 mm Fig. 13.53 0.3 m-