A plastic bar ACB having two different solid circular cross sections is held between rigid supports as shown in the figure. The diameters in the left- and right-hand parts are 50 mm and 75 mm, respectively. The corresponding lengths are 225 mm and 300 mm. Also, the modulus of elasticity E is 6.0 GPa, and the coefficient of thermal expansion a is 100 ×10 -6 /°C. The bar is subjected to a uniform temperature increase of 30°C.
(a) Calculate the following quantities:
(1) the compressive force N in the bar;
(2) the maximum compressive stress sc; and
(3) the displacement dC of point C.
(b) Repeat (a) if the rigid support at A is replaced by an elastic support having spring constant k 50 MN/m (see figure part b; assume that only the bar ACB is subject to the temperature increase).