(1) The Figure below shows the creep rate as a function of stress, for a certain alloy. (a) Determine the working stress at 1100 F and 1500 F using creep strength as the design criteria, based on 1 percent extension in 1000 h. Use a safety factor of 3. (b) Determine the activation energy for creep stress of 10,000 psi Stress (ksi) 100 10 5 1 0.00001 1100F 0.0001 1500F 1300F 0.001 0.01 0.1 Minimum creep rate (percent per hour) 1 10 100

(1) The Figure below shows the creep rate as a function of stress, for a certain alloy. (a) Determine the working stress at 1100F and 1500F using creep strength as the design criteria, based on 1 percent extension in 1000h. Use a safety factor of 3. (b) Determine the activation energy for creep stress of 10,000psi