ME 323 MACHINE DESIGN I HOMEWORK 1-For a bolted assembly, two plates of cast iron are clamped together. Each cast iron assembly part has 0.75 inch thickness. The bolt is in - 16UNF 2 in SAE grade 5. (UNF-Fine Series). The bolt material is steel. A fluctuating external load is applied to the entire joint with Pmax=120 kips and Pmin=60 kips. (70 POINTS) a) Calculate the minimum number of bolts necessary to avoid joint seperation. b) In the same bolted assembly, assume 15 bolts are used and calculate the fatigue factor of safety using the Goodman theory. c) Using the Frustum Method, determine the member spring rate km if the top plate is steel and the bottom plate is cast iron. Assume that a steel washer is used under the bolt head. The thickness of each assembly plate is 0.75 inch and the washer has 0.01 inch thickness. (standard washer face diameter is 1.5d, d is bolt diameter) Given Data: -Esteel: 30 Mpsi, Ecast iron: 14 Mpsi -Applied preload is 75 percent of the proof load (F=0.75F) and Fp=At-Sp -Endurance strength of bolt is 18.6 kpsi -Sut (ultimate tensile strength), A: (tensile stress area) and Sp (proof strength) of bolt should be found from the corresponding tables in your textbook. 2-Explain self-locking condition and determine the roles of lead angle and friction coefficient in self locking. (30 POINTS)