zhangzaili45 |
2007-11-14 20:47 |
不会吧? 1mix+.d e=L*&X d' OGVN (1) The center distance separability of a pair of involute spur cylindrical gears implies that a change in center distance does not affect the . ]!faA\1 8i[LR#D) A. radii of the pitch circles B. transmission ratio C. working pressure angle wASX\D } ?Sw /(}|m (2) The main failure form of the closed gear drives with soft tooth surfaces is the . O2lIlCL U(Z!J6{c A. pitting of tooth surfaces B. breaking of gear tooth z7k$0& 2LZS|fB9o C. wear of tooth surfaces D. agglutination of tooth surfaces bl$j%gI%, *(Ro;?O,pi (3) The tooth form factor in calculation of the bending fatigue strength of tooth root is independent of the . [4\aYB 9N AK;^9b-}q: A. tooth number B. modification coefficient C. module )#PtV~64 -=sf}4A D. helix angle of helical gear y@aKNWy}$ 0Az/fzJlz (4) The contact fatigue strength of tooth surfaces can be improved by way of . }<&d]N ;j!UY.i A. adding module with not changing the diameter of reference circle i7s\CY l?<q
YjI B. increasing the diameter of reference circle ThiN9! Y D:)~%wu Lt C. adding tooth number with not changing the diameter of reference circle :~erh}~ps m_$JWv\|\ D. decreasing the diameter of reference circle r@Nl2 F1J#Y$q~L
(5) In design of cylindrical gear drives, b1 = b2 +(5~10)mm is recommended on purpose to . (Where b1, b2 are the face widths of tooth of the smaller gear and the large gear respectively.) ? oc+ 1e
^}@`!ON A. equalize strengths of the two gears B. smooth the gear drive OW#_ty_ul }7Jp :. qk C. improve the contact strength of the smaller gear g<\>; }e 6i-*
N[!U D. compensate possible mounting error and ensure the length of contact line G:DSWW} ng
9NE8F (6) For a pair of involute spur cylindrical gears, if z1 < z2 , b1 > b2 , then . 7JS#a=D# CC>($k" A. B. C. D. ?uig04@3 ET3,9+Gj (7) In a worm gear drive, the helix directions of the teeth of worm and worm gear are the same. Y&:/~&' r.?+gW!C A. certainly B. not always C. certainly not wR(ttwxK3 "h$D7 mL (8) Because of , the general worm gear drives are not suitable for large power transmission. w~]}acP X~%IM1+L; A. the larger transmission ratios B. the lower efficiency and the greater friction loss s<,"Hsh^CR 6# R;HbkO C. the lower strength of worm gear D. the slower rotating velocity of worm gear Rd0?zEKV g&P9UW>qS (9) In a belt drive, if v1, v2 are the pitch circle velocities of the driving pulley and the driven pulley respectively, v is the belt velocity, then . CM"s9E8y ON
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8qP h ;jsH! (10) In a belt drive, if the smaller sheave is a driver, then the maximum stress of belt is located at the position of going . ]Px:d+wX: 4">84,-N A. into the driving sheave B. into the driven sheave ^T=5zqRD 27$\sG|g C. out of the driving sheave D. out of the driven sheave D8W(CE^} UX?X]ZYVR (11) In a V-belt drive, if the wedge angle of V-belt is 40°,then the groove angle of V-belt sheaves should be 40°. RR8U
Cv 7~:>WMv9 A. greater than B. equal to C. less than D. not less than H_v/}DEG Y/#:)(&@ (12) When the centerline of the two sheaves for a belt drive is horizontal, in order to increase the loading capacity, the preferred arrangement is with the on top. p{w}
|I4D(#w. A. slack side B. tight side l8eT{!4 ~rp.jd 0l (13) In order to , the larger sprocket should normally have no more than 120 teeth. +W!'B
r Q^\{Zg)p A. reduce moving nonuniformity of a chain drive TZ)(ZKX*R _$~ex ~v B. ensure the strength of the sprocket teeth C. limit the transmission ratio 3~#Z E;># "~B~{ _<j D. reduce the possibility that the chain falls off from the sprockets due to wear out of the h4B+0 ,!xz*o+#@ chain 3
XM Bu* Aigcq38 (14) In order to reduce velocity nonuniformity of a chain drive, we should take . HE8'N=0 +F#=`+V A. the less z1 and the larger p B. the more z1 and the larger p uMljH@xBc :5q^\xmmq C. the less z1 and the smaller p D. the more z1 and the smaller p 9J't[(
u|u Ih9O Rp7 (Where z1 is the tooth number of the smaller sprocket, p is the chain pitch) My`josJ`Pb ~GsH8yA_P (15) In design of a chain drive, the pitch number of the chain should be . w-{#6/<kI5 AIIBd A. even number B. odd number C. prime number 7=9A_4G! *RUd!]bh D. integral multiple of the tooth number of the smaller sprocket N?Z+zN&P 8Iqk%n~( VyBJIzs0 R(n0!h4 2. (6 points) Shown in the figure is the simplified fatigue limit stress diagram of an element. ]DL>
.<]d =PeW$q+ If the maximum working stress of the element is 180MPa, the minimum working stress is -80MPa. Find the angle q between the abscissa and the line connecting the working stress point to the origin. S|z( ~ ]m@k'n MfZ}xu vh:UXE lm [xp~@5r' GT1 X 3. (9 points) Shown in the figure is the translating follower velocity curve of a plate cam mechanism. ?$`1%Y9 { 8|Z}?I (1) Draw acceleration curve of the follower schematically. wKeSPs{x =_H*fhXS (2) Indicate the positions where the impulses exist, and determine the types of the impulses (rigid impulse or soft impulse). JXZ:Wg 0YsN82IDD (3) For the position F, determine whether the inertia force exists on the follower and whether the impulse exists. !@]h@MC$7 S3JygN* OA8b_k~ ^QHMN 7r/ sL[(cX?;2 8t^;O! .ON$vn7 _,-M8=dL%* O}\"$n> *M**h-p2' bju,p"J1-E 80l3.z,: 4. (8 points) Shown in the figure is a pair of external spur involute gears. lG^mW\O q}76aa0e The driving gear 1 rotates clockwise with angular velocity while the driven gear 2 rotates counterclockwise with angular velocity . , are the radii of the base circles. , are the radii of the addendum circles. , are the radii of the pitch circles. Label the theoretical line of action , the actual line of action , the working pressure angle and the pressure angles on the addendum circles , . nH3b<k;S uzn))/" >=q!!'$: /\Y%DpG$ Ul~}@^m]4} @SMy0:c: 5. (10 points) For the elastic sliding and the slipping of belt drives, state briefly: %+OPas8C kHIQ/\3?Q (1) the causes of producing the elastic sliding and the slipping. 3E2.v5* 9QM"JEu@ (2) influence of the elastic sliding and the slipping on belt drives.
KL_}:O68 2W-NCE%K)T (3) Can the elastic sliding and the slipping be avoided? Why? u C8T!z /
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wLE jc`',o'[+ 6. (10 points) A transmission system is as shown in the figure. $s!meg@s cHct|Z
u The links 1, 5 are worms. The links 2, 6 are worm gears. The links 3, 4 are helical gears. The links 7, 8 are bevel gears. The worm 1 is a driver. The rotation direction of the bevel gear 8 is as shown in the figure. The directions of the two axial forces acting on each middle axis are opposite. {# _C ]arskmB] (1) Label the rotating direction of the worm 1. 0J</`/g H ;CBdp-BUj (2) Label the helix directions of the teeth of the helical gears 3, 4 and the worm gears 2, 6. DQnWLC"u Bz~h- ?M(Wx Y\\nJuJo uelTsn b<7qmg3 TvwIro >f8,YisH >L4$DKO h!GixN? 7. (12 points) A planar cam-linkage mechanism is as shown in the figure with the working resistant force Q acting on the slider 4. k<qH<<r* 5C?1`-&65V The magnitude of friction angle j (corresponding to the sliding pair and the higher pair) and the dashed friction circles (corresponding to all the revolute pairs) are as shown in the figure. The eccentric cam 1 is a driver and rotates clockwise. The masses of all the links are neglected. 0VPa;{i/ e84TLU?~ (1) Label the action lines of the resultant forces of all the pairs for the position shown. iK:]Q8b >FNt*tX<0 (2) Label the rotation angle d of the cam 1 during which the point C moves from its highest position to the position shown in the figure. Give the graphing steps and all the graphical lines. L9)&9
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~= 4[q *7m p6)UR~9Rs l?[DO?m+R v2V1&- 8. (15 points) In the gear-linkage mechanism shown in the figure, the link 1 is a driver and rotates clockwise; the gear 4 is an output link. Y~xZ{am B"v=Fr[ (1) Calculate the DOF of the mechanism and give the detailed calculating process. nj$K4_ X;NTz75 (2) List the calculating expressions for finding the angular velocity ratios and for the position shown, using the method of instant centers. Determine the rotating directions of and . `fyAV@X }o4Cd$,8 (3) Replace the higher pair with lower pairs for the position shown. }d(6N&;"zN ,+&j/0U (4) Disconnect the Assur groups from the mechanism and draw up their outlines. Determine the grade of each Assur group and the grade of the mechanism. s-B\8&^C n6f|,D!? R7i*f/m n C^'2z <
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RA6D dqT~ !4E:IM63 .\VjS^o&Z& M Pt7 / K +~ 9. (15 points) An offset crank-slider mechanism is as shown in the figure. 6]Jv3Re'(I Y%faf.$/9 If the stroke of the slider 3 is H =500mm, the coefficient of travel speed variation is K =1.4, the ratio of the length of the crank AB to the length of the coupler BC is l = a/b =1/3. j-
A|\: tT 7$2 9 (1) Find a, b, e (the offset). Ur`v*LT}~ u7
mj (2) If the working stroke of the mechanism is the slower stroke during which the slider 3 moves from its left limiting position to its right limiting position, determine the rotation direction of the crank 1. "rXGXQu M(|gfsD (3) Find the minimum transmission angle gmin of the mechanism, and indicate the corresponding position of the crank 1.
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