课程名称︰机械设计 课程性质︰机械系大三必修 课程教师︰陈湘凤 开课学院：工学院 开课系所︰机械工程学系 考试日期（年月日）︰2017.1.12 考试时限（分钟）：100min 试题 : 1. The dimensions of the bracket are: l = 100mm, a = 400mm, t = 10mm, h = 20mm, F = 50N, od = 20mm, id = 14mm. Material is SAE 1015 CD. (1) Find the Von Mises stress at point B. (2) Find the safety factor at point B using the distortion-energy method.(20%) http://i.imgur.com/PE7Yplt.jpg 2. An unpeened helical compression spring made of hard drawn round wire with squared and ground ends has spring rate k, diameter d, and spring index C = 9. The allowable force associated with a solid length is P_all = 45N. The number of active coils is 18. The safety factor based on yielding is 1.8. The maximum percent of tensile strength for maximum allowable torsional stress is 0.45. (20%) (a) Find wire diameter d and the mean diameter D for the case in which the spring is compressed solid. (b) Find the yield strength in the shear of the wire. (c) Find the spring rate k. (d) Find the deflection. (e) Find the solid length. (f) Find the pitch of the spring. (g) Whether the spring will buckle, if the spring is supported between flat parallel surfaces. 3. For s spring same as above experiences, a load varies between 10N and 40N. Determine the safety of factor (a) using the Goodman criterion with Zimmerli data, (b) using the Sines torsional fatigue criterion (steady stresscomponent has no effect) with Zimmerli data. 4. A clamping force of 100kN is provided between two components. There is only M10 × 1.25 thread of bolts available. The material is steel, metric Grade 5.8. The stiffness of the clamped members is four times greater than the bolts.Assume that the load is equally shared by each bolt, (a) if each bolt is stressed to 75% of its proof strength, at least how many bolts are needed? (b) if 10 bolts were used to provide the required clamping force, and assume an external load 5kN was applied to each bolt, find the safety factors in yielding and seperation. (16%) 5. The joint is subjected to a load that varies between 0 and 8 kips. The bolt is 5/8-11 UNC SAE graed 5. The joint constant C = 0.188. (a) whether the bolt fails when no preload is present (the bolt is loosely held). (b) if with preloaded to 75% of its proof strength, find the fatigue safety of factor based on the Goodman fatigue criterion. (c) find the static load factor. (24%) http://i.imgur.com/SVapMcP.jpg --

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