华北水利水电学院试题纸A

1、华 北 水 利 水 电 学 院 试 题 纸 模拟二 20 20 学年 第 学期 级 专业 Machinery Design 试题学号： 姓名： 密封线一二三四五六七八九总 分1. Decide which is the best answer and fill your answer in the table. (30 points)The main functions of couplings and clutches are to transmit movement and .A. radial force B. axial force C. moment D. power The typ

2、e of V-belt is determined by .A. power and rotate speed of big pulley B. calculated power and rotate speed of big pulleyC. power and rotate speed of small pulley D. calculated power and rotate speed of small pulley The tooth form factor in bending fatigue strength is independent of the .A. tooth num

3、ber B. base diameter C. module D. pressure angleThe necessary conditions to form full-film hydrodynamic lubrication bearings are A. There must be a wedge-shaped space between two relative moving platesB. There must be a relative sliding velocity between two plates and the lubricant must be flow from

4、 big entrance to small exit in the direction of the moving plate.C. The lubricant has sufficient viscosity, and the supply of the lubricant is abundant. D. The bearing must be made of Babbit. Which condition is not correct? Which bearing can subject to axial force only? _ A. 6310 B.7310 C. 30310 D.

5、51310In a V-belt drive, if and are the pitch circle velocities of the driving pulley and the driven pulley respectively, is the belt velocity, then .A. B. C. D. 第 1 页 共 5 页华 北 水 利 水 电 学 院 试 题 纸 A2006 2007 学年 第 1 学期 2004 级 机自 专业 Machinery Design 试题学号： 姓名： 密封线In the design of a roller chain drive, the

6、 number of the chain link should be an _. A. even number B. odd number If the strength class of a bolt is 6.8, then the yield stress of the bolt material is_MPa.A. B. C. D. In order to reduce velocity nonuniformity (不均匀)of a chain drive, we should take .A. the less and the larger B. the more and the

7、 larger C. the less and the smaller D. the more and the smaller (Where is the tooth number of the smaller sprocket, is the chain pitch)For a tight bolted fastening with external axial tensile load and preload , the resultant tensile force in the bolt is .A. B. C. D. If contact fatigue strength of ge

8、ars is undercapacity (强度不足), we should increase parameter _.A., but remains the same B., but remains the same C. The requirements for gear materials are usually _ core and _ tooth surface.A. soft, hard B.soft, soft C. hard, soft D. hard, hard Ball bearings can transmit _ speed and _ load capacity th

9、an roller bearings.A. higher, greater B.higher, smaller C. lower, smaller D. lower, greaterTaper key may be used in the case of _.A. high speed and high precision B.low speed and high precision C. low speed and low precision D. high speed and low precisionIn chain drive, the mean speed ratio is _, a

10、nd the instantaneous speed ratio is _.A. constant, not constant B.not constant, constant C. constant, constant D. not constant, not constant 第 2 页 共 5 页华 北 水 利 水 电 学 院 试 题 纸 A2006 2007 学年 第 1 学期 2004 级 机自 专业 Machinery Design 试题学号： 姓名： 密封线If the rigidity of shaft is insufficiency, we should _.A. repl

11、ace the carbon steel by alloy steel B.improve heat-treatment C. enlarge the diameter of the shaft D.enlarge the length of the shaft Fastening thread should be _.A. right-hand, single metric thread B.left-hand, single metric thread C. right-hand, double metric thread D.left-hand, double metric thread

12、 If the contact angle of small belt pulley is too small, we should _.A. increase the belt length B.decrease the belt length Which heat-treatment of steel result in soft tooth surface. _A. quenched B.normalized C. nitrided D. carburized_ gasket can improve the fatigue strength of bolt fastening.A. Me

13、tal B.Leather C. Rubber D.Paper2. Decide which sentence is correct. (15 points)Square thread has higher efficiency than trapezoidal thread.Both slip and elastic creep can be avoided.Worm gearing has higher efficiency than helical gearing.The thinner the minimum film thickness, the greater the load-c

14、arrying capacity of sliding bearing.The bolt fastening should consider anti-loose, because the bolt fastening is not self-locking.Both clutches and coupling cannot be disengaging during operation.In order to reduce unevenly distributed (不均匀分布)load along the gear face width, the gear should be center

15、ed between bearings. The standard value of module of bevel gear is big end module.If the load acting on ball bearing reduces to half, the life of bearing will be multiplied 2 times (增大到2倍).Cast iron and bronze are often materials of worm gear. 第 3 页 共 5 页华 北 水 利 水 电 学 院 试 题 纸 A2006 2007 学年 第 1 学期 20

16、04 级 机自 专业 Machinery Design 试题学号： 姓名： 密封线3. Force analysis. (18 points)A transmission system is as shown in the figure. Gear 1 is the driving gear. Ensuring the axial forces acting on shaft can cancel partly each other, draw in the figure:The hand of spiral of gear 1, gear 2 and gear 4. The rotating

17、 direction of gear 2, gear 3 and gear 4.Three component forces acting on each gear. 4. A bolt fastening subjects to external axial force and preload. We known: external axial force ，preload ，relative rigidity , Try to compute: The maximum axial load in the bolt Residual preload (7 points) 第 4 页 共 5 页华 北 水 利 水 电 学 院 试 题 纸 A2006 2007 学年 第 1 学期 2004 级 机自 专业 Machinery Design 试题学号： 姓名： 密封线5. Point out all the mistakes in the shaft system shown in the figure and draw the correct structure beneath the figure. (10 points)6. (20 point