不会吧? V3O<l}ak
/PbN!r<1
h~rSM#7m
(1) The center distance separability of a pair of involute spur cylindrical gears implies that a change in center distance does not affect the . ]YcM45xg
^<fN
A. radii of the pitch circles B. transmission ratio C. working pressure angle c`w YQUg(
ml$"C
(2) The main failure form of the closed gear drives with soft tooth surfaces is the . yrO\\No#H
?5d7J,"<h
A. pitting of tooth surfaces B. breaking of gear tooth OM,-:H,
W%@L7 xh
C. wear of tooth surfaces D. agglutination of tooth surfaces ,B]kX/W
QEIu}e6b
(3) The tooth form factor in calculation of the bending fatigue strength of tooth root is independent of the . ng$`<~=)\
yD6lzuk{X
A. tooth number B. modification coefficient C. module !"{+|heU9p
>q0c!,Ay
D. helix angle of helical gear ^i}*$ZC72
<t[WHDO`
(4) The contact fatigue strength of tooth surfaces can be improved by way of . cX'&J_T+
v^_OX$=,
A. adding module with not changing the diameter of reference circle dQ+{Dv3A
l
TOO`g
B. increasing the diameter of reference circle %j9'HtjEa
xB=~3
C. adding tooth number with not changing the diameter of reference circle h\GlyH~
u'"VbW3u n
D. decreasing the diameter of reference circle GY9CU=-
NIn#
(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.) RM2<%$
J{Fu 8
A. equalize strengths of the two gears B. smooth the gear drive afEhC0j
kI5`[\
C. improve the contact strength of the smaller gear ]AjDe]
cnfjOg'\{
D. compensate possible mounting error and ensure the length of contact line x O`
#a=
G[7Z5)2B
(6) For a pair of involute spur cylindrical gears, if z1 < z2 , b1 > b2 , then . OmO/x
$@y<.?k>UP
A. B. C. D. A*)G. o:
;E? Z<3{
(7) In a worm gear drive, the helix directions of the teeth of worm and worm gear are the same.
[0v`E5
.32]$vx
A. certainly B. not always C. certainly not 0Q]@T@F.
5c*kgj:x
(8) Because of , the general worm gear drives are not suitable for large power transmission. |7G+O+j
fhCMbq4T
A. the larger transmission ratios B. the lower efficiency and the greater friction loss z:C
VzK,
)%D2JC
C. the lower strength of worm gear D. the slower rotating velocity of worm gear x^_(gve:
tz0_S7h
(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 . EC*rd
E3bS Q
A. B. C. D. vb 2mY
px!lJtvgo
(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 . R7xKVS_MP
zNe>fZ
A. into the driving sheave B. into the driven sheave pF~[
L`v7|! X
C. out of the driving sheave D. out of the driven sheave DQ'yFPE
*_Y{wNF*
(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°. 1\GS"4~P
di^E8egR$
A. greater than B. equal to C. less than D. not less than {pEay|L_
\4;}S&` k
(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. l;TWs_N
obYXDj2
A. slack side B. tight side ]Puu: IG
W(
O)J$j
(13) In order to , the larger sprocket should normally have no more than 120 teeth. yb)!jLnH
&j4 1<A
A. reduce moving nonuniformity of a chain drive !JZ)6mtlr
`~${fs{-`/
B. ensure the strength of the sprocket teeth C. limit the transmission ratio _T,X z_
P.G`ED|K!Y
D. reduce the possibility that the chain falls off from the sprockets due to wear out of the "u#T0
4~;x(e@S
chain F(jvdq
{*EA5;
(14) In order to reduce velocity nonuniformity of a chain drive, we should take . lPA:
aHcj
/5@4}m>Z@
A. the less z1 and the larger p B. the more z1 and the larger p dEz7 @T
~N2<-~=si
C. the less z1 and the smaller p D. the more z1 and the smaller p gQXB=ywF
0taopDi;d
(Where z1 is the tooth number of the smaller sprocket, p is the chain pitch) i+`N0!8lY
xp+Z%0D
(15) In design of a chain drive, the pitch number of the chain should be . xMck A<E
^cQTRO|
A. even number B. odd number C. prime number $kc*~V~
0~.OMG:=
D. integral multiple of the tooth number of the smaller sprocket Ne6]?\Z
<,r(^Ntz
6xLLIby,
kZ8+ev=
2. (6 points) Shown in the figure is the simplified fatigue limit stress diagram of an element. F\Qukn
KJ/
*BBf
If the maximum working stress of the element is 180MPa, the minimum working stress is -80MPa. Find the angle q between the abscissa and the line connecting the working stress point to the origin. I-=H;6w7
*)+K
+J
'?WKKYD7N
fu}ZOPu
6jdNQC$#B
qB%?t.k7
3. (9 points) Shown in the figure is the translating follower velocity curve of a plate cam mechanism. z?9vbx
u0Nag=cU
(1) Draw acceleration curve of the follower schematically. 5]c'n
]VarO'
(2) Indicate the positions where the impulses exist, and determine the types of the impulses (rigid impulse or soft impulse). ?3X(`:KB
?b}d"QsmU
(3) For the position F, determine whether the inertia force exists on the follower and whether the impulse exists. =TTk5(m
,};UD
W
sBsf{%I[{
$i:wS=
w'
9e`.H0
}ZP;kM$g
FCk4[qOp7
st|;]q9?
R]s\s[B
A,P_|
#Tr>[ZC
I04GQq
l
4. (8 points) Shown in the figure is a pair of external spur involute gears. }D/O cp~o
fV 6$YCf
The driving gear 1 rotates clockwise with angular velocity while the driven gear 2 rotates counterclockwise with angular velocity . , are the radii of the base circles. , are the radii of the addendum circles. , are the radii of the pitch circles. Label the theoretical line of action , the actual line of action , the working pressure angle and the pressure angles on the addendum circles , . VE
<p,IO
E3p3DM0F$
XAn{xNpz
qIO<\Yl
H[cHF
\0{g~cU4
5. (10 points) For the elastic sliding and the slipping of belt drives, state briefly: 72YL
}I1A4=d
(1) the causes of producing the elastic sliding and the slipping. QNGICG-
YY&3M
(2) influence of the elastic sliding and the slipping on belt drives. 0%K/gd#S<
~If{`zWoC
(3) Can the elastic sliding and the slipping be avoided? Why? $>72 g.B
[f_4%Now
`u. /2]n
S%+
$
&8l4A=l$
#6jdv|fu
7]i=eD8
Rk1B \L|M
s+=JT+g
!<ae~#]3P
Z[(V0/[]
P3due|4M
FY^#%0~
uSAb
uV\ _j3,2
*jBn
^
v(HCnC
i$Rlb5RU
4. &t
cY}Nr#%s@U
Oy @vh>RY
$U uSrX&
[jOvy>2K]
?z:Xdx\l
c{iF
?~mw
GM5s~,
m[@7!.0=
P]Hcg|&
\2rCT~x
HxC_nh
\Z +O9T%
6. (10 points) A transmission system is as shown in the figure. 5UFR^\e
/r4QDwu
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. =5JTVF
nly`\0C
(1) Label the rotating direction of the worm 1. Lv;R8^n
V9v80e {n4
(2) Label the helix directions of the teeth of the helical gears 3, 4 and the worm gears 2, 6. Z/z(P8#U\
EW* 's(
LnN6{z{M
oSb,)k@
Wr \rruH6
x5Sc+5?*
erG;M! 9\
^#H%LLt
UMg*Yv%
-{
Ng6ntS
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. 49o5"M(
-U6" Ce
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. QyJ2P{z
axTvA(k9
(1) Label the action lines of the resultant forces of all the pairs for the position shown. &
yKUf
a@&^t( 1
(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. @"*8nV#
@"jV^2oY1
_)q,:g~fu
[u_-x3`
ZJotg*I
Qrt[MJ+#
I'URPj:t
b"+J8W
r5!I|E
su~_l[6
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. MB,;HeP!
Y'NQt?h
(1) Calculate the DOF of the mechanism and give the detailed calculating process. mlgw0
~]71(u2
(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 . lNSB "S
h"S+8Y:1{k
(3) Replace the higher pair with lower pairs for the position shown. Re <G#*^
>$]SYF29
(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. <~BheGmmy
z5CZ!"&v
X0X!:gX
gt3;Xi
.!kqIx*3
n/_cJD\
Az2HlKF"L
>r7{e:~q
xN\PQ,J
|q?I(b4 Q@
p<