东大机械洋卷2

(1)       The center distance separability of a pair of involute spur cylindrical gears implies that a change in center distance does not affect the     . d
J{q}U  
N/78Ub  
A. radii of the pitch circles     B. transmission ratio     C. working pressure angle *WfQi8  
$wC'qV *  
(2)       The main failure form of the closed gear drives with soft tooth surfaces is the       . DY\~O  
=O
3)tm;  
A. pitting of tooth surfaces     B. breaking of gear tooth &grqRt  
1:!H`*DU&  
C. wear of tooth surfaces     D. agglutination of tooth surfaces Eh*(N(`  
NfWL3"&X  
(3)       The tooth form factor in calculation of the bending fatigue strength of tooth root is independent of the       . 2ck0k,WP  
2ZEDyQM  
A. tooth number   B. modification coefficient   C. module sC A  
H?rCIS0  
D. helix angle of helical gear Y5c[9\'\  
5z&>NI  
(4)       The contact fatigue strength of tooth surfaces can be improved by way of     . O-huC:zZh  
{&J~P&,k  
A. adding module with not changing the diameter of reference circle Sm{> 8e}UE  
&->ngzg  
B. increasing the diameter of reference circle pzZ+!d  
O7p=N8V  
C. adding tooth number with not changing the diameter of reference circle THARr#1b};  
w+wtr[;wwL  
D. decreasing the diameter of reference circle 7pou(U  
>g m  
(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.) r sq?4+\  
}[R-)M  
A. equalize strengths of the two gears         B. smooth the gear drive H'JU5nE  
dyk(/#*7W  
C. improve the contact strength of the smaller gear '/)qI.  
\VA*3U^@  
D. compensate possible mounting error and ensure the length of contact line #IJeq0TVB  
lF_"{dS_6(  
(6)       For a pair of involute spur cylindrical gears, if z1 < z2 , b1 > b2 , then     . YN+vk}8 <  
)_1 GPS  
A.     B.     C.     D. s_a jA  
^,,}2dsb>  
(7)       In a worm gear drive, the helix directions of the teeth of worm and worm gear are     the same. rOz1tY)l0d  
x|O^#X(,  
A. certainly       B. not always       C. certainly not N/ f7"~+`  
Sg4{IU  
(8)       Because of       , the general worm gear drives are not suitable for large power transmission. hf^<lJh~=  
;1s+1G}_z  
A. the larger transmission ratios   B. the lower efficiency and the greater friction loss kY @(-  
wYg!H>5  
C. the lower strength of worm gear   D. the slower rotating velocity of worm gear zh| 9\lf  

FJ-H ;  
(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       . 'E+"N'M|  
~MBPN4r  
A.   B.   C.   D. R(`:~@3\6  
tAF?.\x"g  
(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     . wD=]U@t`,  
ZZ7qSyBs?  
A. into the driving sheave       B. into the driven sheave i'7+ ?YL  
kQ lU.J>^  
C. out of the driving sheave       D. out of the driven sheave *<\K-NSL  
@phVfP"M  
(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°. mL =d EQ  
SkE<V0  
A. greater than     B. equal to     C. less than     D. not less than sVK?sBs]  
lQ-<T<g  
(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. L23}{P  
l2qvYNMw  
A. slack side   B. tight side D2?H"PH  
=c'4rJ$+  
(13)   In order to     , the larger sprocket should normally have no more than 120 teeth. d=PX}o^  
80Dn!9j*  
A. reduce moving nonuniformity of a chain drive l!F$V;R  
;^5k_\  
B. ensure the strength of the sprocket teeth     C. limit the transmission ratio Zgo~"G  
f9W:-00QD  
D. reduce the possibility that the chain falls off from the sprockets due to wear out of the Q$c6l[(g  
7C|!Wno[;  
chain
cm(*F0<  
sD:o 2(G*  
(14)   In order to reduce velocity nonuniformity of a chain drive, we should take       . kh5a>OX  
WVdV:vJ-  
A. the less z1 and the larger p     B. the more z1 and the larger p P.'.KZJ:WD  
3m1(l?fp  
C. the less z1 and the smaller p     D. the more z1 and the smaller p JaCX}[R  
"lI-/G  
(Where z1 is the tooth number of the smaller sprocket, p is the chain pitch) ;
:P4~R  
BDB*>y7(  
(15)   In design of a chain drive, the pitch number of the chain should be     . d:@+dS  
>R+-mP!nj  
A. even number   B. odd number   C. prime number wq$$. .E  
  zm"  
D. integral multiple of the tooth number of the smaller sprocket eV[{c %wN:  
&h-_|N  
2:*15RH3  
/4
G1,T_,  
2. (6 points) Shown in the figure is the simplified fatigue limit stress diagram of an element. H9mNnZ_k  
;W,* B.~  
If the maximum working stress of the element is 180MPa, the minimum working stress is -80MPa. Find the angle q between the abscissa and the line connecting the working stress point to the origin. x>yqEdR=o  
r#sg5aS7O|  
aZN?V}^+  
jHFjd'  
)|~& (+Q?]  
8{>|%M  
3. (9 points) Shown in the figure is the translating follower velocity curve of a plate cam mechanism. (HAdr5  
lQIg0G/3  
(1)   Draw acceleration curve of the follower schematically. vPnS`&  
:` SIuu~@  
(2)   Indicate the positions where the impulses exist, and determine the types of the impulses (rigid impulse or soft impulse). OLG)D#m(4/  
z 0?MeH#  
(3)   For the position F, determine whether the inertia force exists on the follower and whether the impulse exists. v[$e{Dz(  
aj?ZVa6  
4 $k{,  
4rhHvp  
RPX.?;":  
w"v96%"Y  
{L$$"r,  
zTue(Kr  
4zs0+d+  
?8753{wk  
YMo8C(  
IR"C ?  
4. (8 points) Shown in the figure is a pair of external spur involute gears. nzbVI  
ftn10TO*  
  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 , . ?<J~SF Tt  
Af\@J6viF7  
);HhV,$n  
O}C*weU  
z&9ljQ iF  
,tXI*R  
5. (10 points) For the elastic sliding and the slipping of belt drives, state briefly: /Igz[P^\9  
blomB2vQ  
(1)   the causes of producing the elastic sliding and the slipping. g8/ ,E-u  

qbc=kP  
(2)   influence of the elastic sliding and the slipping on belt drives. ,./n@.na  
e>_a (  
(3)   Can the elastic sliding and the slipping be avoided? Why? y /vc\e  
MHp:".1  
#)L}{mHLM-  
I>8_gp\1  
$J4)z&%dr  
3K||(  
id,'+<  
bR}fj
.gP  
"kFNOyj3\  
7`7M4  
J>M9t%f@  
W$7H "tg  
o;DK]o>kH  
Ugo!  
|oOAy  
p5"pQeS  
B&7:=t,m(  
gKQs:25  
1.N2!:&G|  
:
&n F>  
#%%!r$UL  
a~R.">>$  
gB%"J
Dn8  
_KtV`bF  
NB44GP1-@  
-awG14%  
a*}>yad  
Cb|1Jtb
 
m8 _yorz  
,cS_687o  
? [5>
!   
rtbV*@Z  
6. (10 points) A transmission system is as shown in the figure. AEx VKy  
x)Zm5&"Gg  
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. X!ldL|Ua%  
\b6{u6?+  
(1)   Label the rotating direction of the worm 1. KJS-{ed  
FG!hb?_1  
(2)   Label the helix directions of the teeth of the helical gears 3, 4 and the worm gears 2, 6. F&+qd`8J  
&w`DF,k|  
/s+I
stW  
RL\?i~'KH  
K1R?Qt,qDF  
Ahba1\,N$  
_!vy|,w@e  
f52P1V]  
$`%Om WW{  
dKD:mU",M  
7. (12 points) A planar cam-linkage mechanism is as shown in the figure with the working resistant force Q acting on the slider 4. -&]!ig5v  
v.4G>00^  
  The magnitude of friction angle j (corresponding to the sliding pair and the higher pair) and the dashed friction circles (corresponding to all the revolute pairs) are as shown in the figure. The eccentric cam 1 is a driver and rotates clockwise. The masses of all the links are neglected. vGPsjxk&  
ZQ*Us*9I  
(1)   Label the action lines of the resultant forces of all the pairs for the position shown. kw#-\RR_c  
Fsx<Sa  
(2)   Label the rotation angle d of the cam 1 during which the point C moves from its highest position to the position shown in the figure. Give the graphing steps and all the graphical lines. 7Nk|9t  
Uey'c1  
Y.tT#
J^=  
QX<x2U  
vp*+Ckd  
dT?3Q;>B?  
nu~]9~)I  
g3{UP]Z71  
jf)l; \u  
&|RTLGwX  
8. (15 points) In the gear-linkage mechanism shown in the figure, the link 1 is a driver and rotates clockwise; the gear 4 is an output link. y@LiUe5  
xh9$ZavB*  
(1)   Calculate the DOF of the mechanism and give the detailed calculating process. XGC\6?L~  
f^u-Myk  
(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 . K5XW&|tY!  
C&*1H`n  
(3)   Replace the higher pair with lower pairs for the position shown. J,u-)9yBA<  
2u!&Te(!9  
(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. pPo xx"y  
a\}MJ5]  
r@Jy*2[-Jq  
9`
Fw}yAt  
?7LvJ8  
T:m" eD;  
V(DY!f_%  
C}Kl!  
[?KGLUmTAI  
v*=P   
$$&.}}.,  
MsP6C)dz  
\i%mokfbc  
* zyik[o  
xLO Qu.  
a6e{bAuq  
Ihf :k_;  
F!0iM)1o  
JDE_*xaUV  
_"yA1D0d_  
FC,=g`Q!  
}P fAf  
rHX^bcYK  
0zq'Nf?#3  
V<I(M<Dj  
AO|9H`6U6F  
9. (15 points) An offset crank-slider mechanism is as shown in the figure. #Q^".#  
 )&7.E  
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. "ya xHd
 
4r1 \&sI$~  
(1)   Find a, b, e (the offset). 3 J04 $cD  
jBw)8~tYm  
(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. FHSoj=  
gtA34iw  
(3)   Find the minimum transmission angle gmin of the mechanism, and indicate the corresponding position of the crank 1.