Two bars are joined together and attached to supports as in the figure below. The left bar is brass for which E = 90 GPa, α = 20x10–6/°C, and the right bar is aluminium for which E = 70 GPa, α = 25x10–6/°C. The cross-sectional area of the brass bar is 750 mm2, and that of the aluminum bar is 950 mm2. Let us suppose that the system is initially stressed free and that the temperature then drops by 50°C.

a. If the supports are unyielding, find the normal stress in each bar.

b. If the right support yields 0.15 mm, find the normal stress in each bar.

Brass Aluminum 1250mm 850mm