中国石油大学(北京)机械04级机械原理模拟测验答案.doc

China University Petroleum, Beijing, 2006-2007, Semester 1Test paper (A) of Mechanisms and machine Theory. (Closed book) No.1234567Total ScoreScoreClass Name Student ID No. 1. In a crank-slider mechanism shown in the figure, the crank is the driving link. the stroke H of the slider is 50mm, the coefficient of travel of travel speed variation K =1.5, the offset e=20mm. Please calculate : (20%)1) The crank acute angle between the two limiting positions，2) The dimensions of crank a, coupler b，3) The maximum pressure angle aMAX. of the mechanism，4) Will the dead-point occur if the slider is driving link?评分标准：本题每小题５分１） 图画对二极限位置之夹角可得3分，写出公式k=(180+θ)/( 180-θ) 可得４分。

结果1分２） 计算方法可不同，必要公式和中间过程4分，结果１分３） 写对表达式即可得５分，位置对，但结果错误扣１分４） 答对得分，错不得分2. Draw the kinematic diagram of the mechanism.(8%) 评分标准：每错一处运动副扣２分，未按比例画图不扣分3. In the combined gear train shown below, Z1=17, Z2=68, Z3=23, Z4=19. Z4’ =20, Z5=24. Find the train ratio i15. (10%)Solution:In the ordinary gear train 1-2： ①In the planetary gear train 3-4=4’-5-2: ② ③评分标准：１） 公式①４分，公式中丢“—”扣1分，２） 公式②5分３） 结果1分4. The fig. shown is an involute spur gear set: the driving gear 1 rotates at angular velocity ω1, ra1 and ra2 are the radii of both addendum circle of gear1 and gear 2 respectively, rb1 and rb2 are the radii of both base circle of gear1 and gear 2. module m＝4mm，pressure angleα＝20，μl＝0.001m/mm . Draw in the figure and point out the following: (20%)1) The actual line of action B1B2 graphically, 2) The theoretical line of action N1N2 graphically, 3) Measure the actual line of action B1B2,,Calculate the contact ratioεα according the definition of contact ratioεα ea=B1B2/Pb pb=pmcosa评分标准： １） 找对B1B2即可得６分，否则不得分。

２） 找对N1N2可得6分，N1N2方向反扣２分３） 量得B1B2 可得2分，写出εα的定义式得６分5. Calculate the degree of freedom of the mechanism shown( the formula should be given). Add the serial numbers to the links and indicate compound hinge, passive DOF, redundant constraint before the calculation of the DOF. What is the condition for the mechanisms to have determined motion?(10%)评分标准n=8 １分 pL=11 １分 pH=1 １分F=3n－2pL－pH=38-211-1 ４分＝1 １分 机构有确定运动的条件为：原动件数与机构的自由度数相等。

１分 指示对 compound hinge, passive DOF, redundant constraint 共１分6. A mechanical system runs at a periodic fluctuated speed with a angular period of φT=2π,a rotating link is selected as an equivalent link. The equivalent driven moment Mr on the equivalent link are given functions of the rotating angle j as shown in the figure. and the equivalent input moment Md on the equivalent link is constant. The equivalent moment of inertia Je can be neglected. The average speed is nm =1000 r/min. The allowable coefficient of speed fluctuation is [d]=0.01（12%） 1) Find the equivalent input moment Md,2) Calculate the maximum increment of work DWmax,3) Calculate the minimum moment of inertia of the flywheel JF .Suppose E0=E0Ea=E0-F1= E0+0.50.25p30=E0+15p/4 Eb=Ea+F2= E0－15p/4Ec=Eb-F3= E0+15p/4 Ed=Ec+F4= E0－15p/4Ef= E0 Emax= Ea = E0+15p/4Emin= Eb = E0－15p/4 评分标准：本题每小题4分1） 计算对Md=30Nm得４分. 写出Wd=Wr但结果算错扣１分2） 计算对DWma得４分. 解题方法对或画能量示意图方法对仅计算结果算错扣１分3） 写对JF的表达式且计算结果全对得4分，写对JF的表达式且计算结果错扣１分。

7. The fig. shown is a plate cam with a translating offset roller follower. The cam contour consists of four arcs. Using a graphical method, indicate: (20%) 1) The pitch curve of the cam and 2) The radius of prime circle rP, 3) The cam angle for rise δ0, the cam angle for outer dwell δS , the cam angle for return δ0, the cam angle for inner dwell δS，4) The lift h of the follower , 5) Find the maximum pressure angle of the cam mechanism amax in the rise.评分标准：每小题全对４分1) 画对理论廓线得４分，错不得分.2) 画对基圆得４分，错不得分3) 标对d０，ds，d0’ ，ds’每一项得1分，错不得分。

4) 画对升程h得４分，错不得分5) 图示对amax发生位置和大小得4分，位置对但大小错扣1分7。