08-11-2016, 10:12 AM
1466479226-VibrationReport.pdf (Size: 9.67 MB / Downloads: 5)
Abstract
In!this!experiment!four!eccentric!masses!are!used!in!conjunction!with!four!springs!and!one!
damper!to!simulate!the!vibration.!Masses!are!aligned!in!different!orders!to!simulate!in@
phase!and!out@phase!situation.!Acceleration,!frequency!and!phase!shift!of!the!system!is!
measure,!which!then!are!used!to!do!calculations!and!generating!graphs!to!describe!the!
simple!harmonic!motion.!For!in@phase!situation!natural!frequency!is!measured!to!be!9.16!Hz!
and!calculated!to!be!9.6!Hz.!This!is!a!fairly!good!result!since!in!real!life!nothing!is!perfect!and!
it!is!not!possible!to!generate!theoretical!results.!As!expected!the!calculated!natural!
frequency!is!slightly!larger!due!to!the!fact!that!damping!is!assumed!to!be!zero!using!
theoretical!calculation,!where!the!system!really!is!slightly!damped.!For!out@phase!situation!
natural!frequency!happens!at!frequency!of!12.81!Hz!and!also!at!6.13!Hz,!however!at!12.81!
Hz!the!amplitude!is!much!larger.
1.0 INTRODUCTION
Vibration!due!to!rotating!eccentric!masses!is!a!common!phenomenal!that!one!sees!in!everyday!life!
such!as!vibration!of!automobile!engine!or!the!washing!machine.!This!phenomenal!is!really!important!because!
if!not!dealt!with!promptly!one!could!have!catastrophic!failures!due!to!the!fatigue!caused!by!the!vibration.!As!
observed!in!this!lab!at!natural!frequency!vibration!force!could!get!really!big!which!could!lead!into!an!unstable!
system!and!causing!failure.!
2.0!METHODS
As!shown!in!figure!1,!this!experiment!consists!of:
Engine!Model:!The!box!that!contains!the!shaft!and!
essentric!masses
Optical!Encoder:!used!to!generate!an!optical!pulse!per!
rotation!of!essentric!mass
Speed!Control:!used!to!control!the!speed!of!rotation
Accelerometer:!a!piezoelectric!element!that!produces!
an!electric!charge!when!subject!to!a!load,!it!is!used!to!
measure!the!vertical!acceleration.
There!is!one!rectangular!box!which!could!model!
a!cars!engine.!The!front!and!back!of!the!system!contains!
two!rotating!shaft!which!have!two!essentric!masses!
attached!to!!them.!In!total!there!are!four!essentric!masses!that!
rotate.!For!in@phase!all!the!masses!are!pointing!in!the!same!
direction!to!start!with,!for!our@phase!masses!point!opposite!of!the!
masses!on!the!other!side.!Figure!2!is!the!front!view!of!the!
experiment!which!is!really!simular!to!the!back!view.!Figure!3!shows!
the!arrangments!of!the!4!springs!and!the!damper!from!the!side.
The!values!that!are!measured!with!hand!in!this!lab!are!the!
radious!of!the!eccentric!mass,!the!distance!of!the!masses!from!the!
center,!which!is!where!the!damper!is!located.!The!values!that!are!
measured!with!computer!are!frequency,!acceleration!and!the!phase!
shift.