(1) For a tight bolted connection with transverse load, the bolt is carried by . Hg] r5Fe/c
~MOIrF
A. shear stress B. tensile stress =oBV.BST u
4v; /"4)'
C. shear stress and tensile stress D. shear stress or tensile stress bi QDupTz
s q_
f [!
(2) For a tight bolted connection with axial tensile load F and preload , the resultant tensile force in the bolt is . aPR
F
LBTf}T\
A. B. C. D. BPW2WSm@<
0y*8;7-|r)
(3) If the performance grade of a bolt is 6.8, then the yield limit stress of the bolt material is MPa. L:7%W dyh
~OXPn9qPp
A. 600 B. 800 C. 680 D. 480 vLq_l 4l
[:Sl^ Z&6M
(4) The lubricating method of a journal bearing is dependent on . rOX\rI%0+
i!
(u4wTFF
A. average intensity of pressure p B. circle velocity of journal v C. pv D. +Y-Gp4 "
ta %yQd7
(5) For a hydrodynamic radial journal bearing, the valid method for increasing is to . 12.|E d*72
idEhxvAo
A. increase relative clearance B. increase oil supply S/V%<<[>p]
K 9]L>Wj
C. decrease D. replace lubricating oil with lower viscosity 1
Qln|b8<
qf;x~1efC4
(6) For a hydrodynamic radial journal bearing, the relative clearance is the ratio of . 4S5U|n
+87|gC7B
A. diametral clearance and journal diameter B. radial clearance and journal diameter ]V^ >aUlj
KSz;D+L \
C. minimal clearance and diametral clearance \8g'v@$wG
~wvu7
D. minimal clearance and journal diameter _\;0E!=p
T\q:
(7) The axial preloading for rolling bearings is for _______. }p5_JXBV
$t0o*i{
A. increasing loading capacity B. decreasing noise 0fu*}v"
?.Q$@Ih0
C. improving running precision D. avoiding shaft displacement F/V -@SF
Np7+g`nG
(8) The inner ring and outer ring of the bearing are separable. pmRm&VgE.
GHY+q{'#V_
A. deep-groove ball B. self-aligning ball C. tapered roller D. self-aligning roller ,R. rx oO
(@m/j2z
(9) In an important application, if the reliability of rolling bearings is increased to 95%, then the relation between the dynamic load rating relative to 95% reliability to the basic dynamic load rating C is _______. w p\-LO~
1J( [*)
A. B. C. D. uncertain Qo32oT[DM
1oe,>\\
(10) For a cylindrical helical compressive spring, the maximal shear stress on spring wire happens at the ______. I3HO><o f
\HXq~Y
A. inner side of spring coil B. outer side of spring coil ,p{naT%R
KRz~3yH{ c
C. center of spring wire D. arbitrary position on spring wire .' }jd#
nrHC; R.nE
(11) For a cylindrical helical compressive spring with working coils being 12, if the number of working coils is decreased by 3, then spring stiffness is _____. ! c`&L_ "!
+5S>"KAUt0
A. decreased to 3/4 of the original value B. decreased to 9/16 of the original value VCfHm"'E8
v4< W57oH
C. not changed D. increased to 4/3 of the original value 2xf #@`U
( <YBvpt4>
(12) For a static balanced rigid rotor, its mass center is located at the rotating axis. L&c
&
<+0T
Qo)Da}uo20
A. certainly B. not always C. certainly not 3CgID6[Sy
r1}^\ C
(13) Shown in the figure is a cylindrical cam with uniform material, accurate manufacture and installation. When it rotates round the axis A-A, the cam is under the state of _________. cI P.5)Ca
h;,1BpbM
A. static imbalance B. static balance C. complete imbalance D. dynamic balance 6#7hMQ0&;O
[3"F$?e5
>MJ#|vO
+q'\rpt
(14) The installation of flywheel in machinery is to . 'y\Je 7
KF
zI27r
A. eliminate speed fluctuation B. realize steady running E/g"}yR
w%.hALN5-C
C. decrease speed fluctuation D. balance the inertia forces )i}j\";>L
tBbOxM m0
(15) In order to decrease the flywheel weight, the flywheel should be installed on the 。 ]o8]b7-
`mzlOB
A. equivalent link B. crankshaft with lower rotating speed Vx(*OQ
=n HKTB>
C. crankshaft with higher rotating speed D. spindle of machinery <Cv(@A->
h{gFqkDoTI
ao2 ^3e
i
qvLu{
2. (7 points) In a tight bolted connection with axial tensile load, both the preload and the axial working load are constant. If the metal gasket between the connected components is replaced by a leather one, explain, with force-deformation diagram, the changes of the resultant tensile force in the bolt and residual compressive force on the connected components. Up{[baWF
=..Bh8P71!
B:T s_9*
B W<Dmn
se\f be ^0
N[p o)}hp
hI'WfF!X
<Z]#v r q
o/ w3b 8
au{) 5W4~
=#2c
r:1
YI g(^>sq
{Sf[<I
ob \-OMNs@
2#>;cn\
ri Db !oC
^.6[vmmq
@@AL@.*
Zz0bd473k?
xqt?z n
2!{D~Gfl=
w\)K0RN
ib=)N)l
gQ_<;'m)2
+<a\0FsD
x4WCAqi/2
\N9=13W<lK
q&25,zWD
/65YHXg,
WC#6(H5t$
3. (10 points) Shown in the figure are the four structure schemes of the moving pulley shaft system in a lifting device. In each structure scheme, the lifting load is constant; the shaft diameter, shaft material and method of heat treatment are the same, respectively. \ %Mcvb.?
V$?6%\M^*
(1) Determine the loads carried by the shaft and shaft types in each structure scheme. d4| )=
x3q^}sj%
(2) Determine the stresses on the shaft and their changing characteristics in each structure scheme. Gy
q 6?
W'C>Fn}lO?
(3) Compare the strength difference of the four shafts. $
VT)
_4by3?<c
l77 -I:
{KG}m'lx
(a) (b) (c) (d) EpS/"adI-!
if*V-$[I
K2xB%m1LK
L^JU{\C
L]=]/>jQ6
~O}r<PQ
zDvV%+RW)
.RroO_H
SY,ns*>1F
\rr"EAk]
d:'{h"M6
QNb
Z)
YuhfPa
R>bg3j
TzKM ~a#
_
s 3aaOL
4. (8 points) Shown in the figure is a transmission layout for a belted conveyer. The arrangement for speed reduction is as follows: 1(motor)→2(chain drive)→3(gear reducer)→4(belt drive)→5(conveyer). Point out the unreasonable aspects of the arrangement and give a correct order represented with the drive number. < WUgH 6"
jRsl/dmy
p*<Jg l
cxR.:LD}
5. (15 points) Shown in the figure, a helical gear shaft is supported by a pair of angular contact ball bearings (7208AC) with ; the radial loads acting on the bearings are , ; the externally axial load on the shaft is ; the rotating speed of the shaft is . k+"];
]WMzWt: L
(1) Find the axial forces on the two bearings: , . LH54J;7 Y
a j4ZS
(2) If , find the equivalent dynamic loads of the two bearings: , . !$NK7-
H^'%$F?Ss
(3) Find the bearing lives: , . Ry +?#P+
:Quep-:fy<
]WNY"B>+
?GX@&_
^P,Pj z
q]1p Q)\'p
m ^FKE:
?$`kT..j,u
@KM?agtlbl
GJWGT`"
@q!T,({kx
8pEA3py
1Xi>&;],
m$C1Ea-wnT
*ELU">!}G
#6a!OQj
sPc}hG+N
.RmFYV0,
P84YriLo
[f:&aS+
6. (15 points) In a gear train shown in the figure, , , , , , , , , , the rotating direction of the gear 1 is as shown in the figure. Find both the magnitude and the direction of . R1 SFMI
4"|3 pMr
wdt2T8`I/
-'O|D}
(Zx--2l c
#do %u"q
sCJ|U6Q-
iz^a Qx/
Q\z aa9P
9:g A0 Z
9BP'[SM%),
3{.]!
7. (15 points) Shown in Fig. (a) is the dynamically equivalent model of a mechanical system. The equivalent resistant moment of force is a given function of the rotating angle shown in Fig. (b) with the period . The equivalent driving moment of force is constant. The equivalent moment of inertia of the system is (constant). The average rotating speed of the equivalent link is . 4r83;3WXs
M._E$y,5
(1) Find the equivalent driving moment of force. C T_tJ
Kn3Xn`P?
(2) Find the coefficient of speed fluctuation , maximal rotating speed and minimal rotating speed of the equivalent link. OmkJP
G11KAq(
(3) If the allowable coefficient of speed fluctuation is , find the minimum moment of inertia of the flywheel on the crankshaft A of the equivalent link. wEq&O|Vj
P7T'.|d
TDZ==<C
I@z@s}x>
q {}5w M
_\yR/W~
&HLG<ISw
b 1.S21
M
hW9^?
L'a+1O1q&i
h}'H st
UAz^P6iQ`~
|AE{rvP{@
|J`v
w
jP/Vqe%%8
rSt5 @f?
` ;mQ"lO
#%ld~dgz-
6/3E !8
%{IgY{X
:zo5` [P
f*"T]AX0
-z .
wAp
Xu~N97\G
n6,YA2yZO
;{
H Dz$
bJ
6iv z
N2 3:+u<)E
fnr8{sr.2Z
%U}6 (~
t\QLj&h}E
@8`I !fZ
MC,Qv9
m
b'SP, }s5"
aB (pdW4
w (`g)`
mE{QT ZS
T ?[;ej:
mX.mX70|J
Ebj0
{ZL
S9$, .aq
ayn aV
8. (15 points) Point out all the mistakes in the shaft system shown in the figure and explain them with brief words.
