Please find the torsional yield strength, the yield strength, the spring index, and the mean diameter. Use: E = 28.6 Mpsi, G = 11.5 Mpsi, A = 140 kpsi·in, m = 0.190, and relative cost= 1.

A viscoelastic column is made of a material with a creep compliance of D(t)= 0.75+0.5log10t+0.18(log10t)^2 GPA^-1 for t in s. If a constant compressive stress of σ0 = –100 MPa is applied at t = 0, how long will it take (= t1/2) for the height of the column to decrease to ½ its original value? Note: You will obtain multiple answers for this problem! One makes sense physically and one does not.

A group of 23 power transistors, dissipating 2 W each, are to be cooled by attaching them to a black-anodized square aluminum plate and mounting the plate on the wall of a room at 30°C. The emissivity of the transistor and the plate surfaces is 0.9. Assuming the heat transfer from the back side of the plate to be negligible and the temperature of the surrounding surfaces to be the same as the air temperature of the room, determine the length of the square plate if the average surface temperature of the plate is not to exceed 50°C. Start the iteration process with an initial guess of the size of the plate as 43 cm.   The properties of air at 1 atm and the film temperature of (Ts + T)/2 = (50 + 30)/2 = 40°C are k = 0.02662 W/m·°C, ν = 1.702 × 10–5 m2 /s, Pr = 0.7255, and β = 0.003195 K–1.         Multiple Choice   0.473 m   0.284 m   0.513 m   0.671 m