A steel bolt of diameter 10 mm passes through a brass tube of internal diameter 15 mm and external diameter 25 mm. The bolt is tightened by a nut so that the length of tube is reduced by 1.5 mm. If the temperature of the assembly is raised by 400C, estimate the axial stresses in the bolt and the tube before and after heating. Material properties for steel and brass are : ES = 2 × 105 N/mm2, $\alpha _{S}$= 1.2 × 10-5/0C and Eb = 1 × 105 N/mm2, $\alpha _{b}$ = 1.9 × 10-5/0C.