Download - Final Exam MD2016 Final
8/20/2019 Final Exam MD2016 Final
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Faculty Of Engineering 3rd Year Time : 3 hours
Mechanical Engineering Department 5/2/2016 2nd Term
Design of Machine Elements I FINAL EXAM
Questions: Answer only tree !uestions Poin
ts
Q Figure P! sho"s a portion of a high#pressure $oiler accumulator ha%ing&at head' The end plates are a()ed using a num$er of $olts of
M 16×2−UNC ! grade *'+! "ith rolled threads' ,i%en: Se=100 Mpa
!
e)ternal load P varies¿0¿12
kips
bolts -andk p=5k b "here the connection is
permanent' Determine:
I' The factor of safety n of the $olt against fatigue failure "ith and
"ithout preload'
II' The load factor ns against .oint separation'
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Q/ a1 2 ri%eted .oint is under an inclined eccentric load P! as indicated in
Fig'P/#a' alculate the ma)imum shear stress in the #in diameter
ri%ets'
0
$1 2 steel side plate is to $e "elded to a %ertical steel column
according to the speci4cations in Fig'P/#$' 5eglecting stress
concentrations e6ects! calculate the magnitude and clearly
indicate the direction of the resultant shearing stress at the critical
point' In selecting the critical point is sure to consider e6ects of
$oth torsion#li7e shear and direct shear'
0
Q3 2 helical#coil spring "ith plain ends and ground is to $e used as a return
spring on the cam#dri%en %al%e mechanism sho"n in Fig'P3' The '*0#in
diameter rod must pass freely through the spring' The cam eccentricity is
0'8* inch 9the total stro7e is '*0 inches1' The height of the compressed
spring "hen the cam is at the head#end#dead#center 9ED1 position is
;'8* in as sho"n' The spring must e)ert a force of 300 l$ "hen at the
ED position sho"n in the s7etch! and must e)ert a force of *0 l$ "hen
the cran7#end#dead#center 9ED1 at the $ottom of the stro7e' That is!
the spring is preloaded into the machine' The spring is to $e made of a
patented spring steel "ire that has a /00!000#psi ultimate tensile
strength! <0!000#psi tension yield strength! and <0!000#psi fatigue
endurance limit' =ased on in4nite life design a safety factor of '/* and
Springindex ,C =8 are desired' Determine the follo"ing:
' Mean coil radius! > !/' ?ire diameter! d!
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8/20/2019 Final Exam MD2016 Final
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3' 5um$er of acti%e coils! 5!@' Apring rate! 7! and*' Free length of the spring! Bf'
Q@ 2 /0#mm po"er scre" for a hand#cran7ed ar$or press is to ha%e a single#
start sCuare thread "ith a pitch of @#mm' The scre" is to $e su$.ected to
an a)ial load of * 75' The coe(cient of friction for $oth threads and
collar is estimated to $e a$out 0'0<' The mean friction diameter for the
collar is to $e 30#mm' Find :
' The nominal thread "idth! thread height! mean thread diameter!
and the lead'/' Estimate the torCue reCuired to raise the load'3' Estimate the torCue reCuired to lo"er the load'@' Estimate the e(ciency of this po"er scre" system'
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