261A steel rod with a cross sectional area of 150 mm2 is stretched between two fixed points. The tensile load at 20 C is 5000 N. What will be the stress at -20 C? At what temperature will the stress be zero? Assume = 11.7 um/cm and E = 200 x 109 N/m2.

Solution: S = 126.9 MPa. T = 34.2 C 262A steel rod is stretched between two rigid walls and carries a tensile load of 5000 N. at 20 C. If the allowable stress is not exceed 130 MN/m2 at -20 C, what is the minimum diameter of the rod? Assume = 11.7 um/ (m C) and E = 200 GPa.

Solution

263Steel railroad rail 10m long are laid with a clearance of 3mm at a temperature of 15 C. At what temperature will the rails just touch? What stress will be induced in the rails at the temperature if there were no initial clearance? Assume = 11.7 x 10-6 m/ (m C) and E =200 GPa.Solution

264At temperature of 90 C, a steel tire 10 mm thick and 75 mm wide that is to be shrunk onto a locomotive driving wheel 1.8 m in diameter just fits over the wheel, which is at temperature of 20 C. Determine the contact pressure between the fire and the wheel after the assembly cools to 20 C. Neglect the deformation of the wheel caused by the pressure of the tire. Assume = 11.7um/ (m C) and E = 200 x 109 N/m2.

Solution

265.At 130, a bronze hoop 20 mm thick whose inside diameter is 600 mm just fits snugly over a steel hoop 15 mm thick. Both hoops are 100 mm wide. Compute the contact pressure between the hoops when the temperature drops to 20 C. Neglect the possibility that the inner ring may buckle. For steel, E = 200 GPa and = 11.7 um/(m C). For Bronze, E = 83 GPa and = 19 um/(m C)

266.At 20 C, a rigid slab having a mass of 55 Mg is placed upon two bronze rods and one steel rod as shown. At what temperature will the stress in the steel rod be zero? For the steel rod, A = 6000 mm2, E = 200 x 109 N/m2, and = 19.0um/( m C ) Solution