sine sweep vibration testing primer
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Sine Sweep Vibration Testing Primer
Eric Sauther OPT521 Optomechanics Fall 2013
Why do we do a Sine Sweep Vibration Test?• Part Responses to a Sine Wave Input are important to characterize a
part/assembly for several reasons:• Characterize Model Response • Endurance Limits of Part(s)• Actual characterized response under test, instead of Calculated• Characterize response of Test Equipment so it can be “backed out” of the
performance data• General Investigation. If we don’t understand how a part will perform, or life
of the part (related to Endurance) we can characterize it. A more well Known Phrase would be “Destructive Testing”
What is Sine Sweep Vibration?• Wikipedia describes vibration as a Oscillatory motion about an equilibrium
point.• For a Sine Sweep Vibration it is a movement back in forth usually in one DOF.
The movement is in a controlled oscillatory motion that can be defined as a sinusoidal function. • The Sine Wave Amplitude, and rate at which you wish to “Sweep” through the
range of frequencies of interest are programmed inputs into the Vibration Table you’ll be using for testing.
A Sine Sweep Signal Input
Types of Sine Sweeps Typical Sine Sweep is a linear input• The Sinusoidal Signal input can be
customized:• Y(t)=Sin{2}}• Non-Linear Sine frequency
Change inputs are used if you want to spend less time testing at a certain frequency or range of frequencies for pragmatic reasons
A Sine Sweep Signal Input• For a test engineer the parameters for a Sine Sweep input are already
provided to you by an Analyst or exists as an industry standard input profile. Some materials, Parts, and Environments have been already well characterized• It is Relevant to have an understanding that Displacement, Velocity,
and Acceleration are related due to first Order Harmonic Oscillation in a Single DOF
Sine Sweep Signal Input• In a single DOF we can derive
the relationships to find our test parameters for Displacement, Velocity and Acceleration at any given frequency input.
) Velocity= *
Acceleration=Displacement ( Displacement=k*
Sine Sweep Signal Input
Displacement, Velocity, Help define your input signal normally shown as Acceleration
Sine Sweep Signal Response from Force Input• As we’ve investigated through SolidWorks in HW 8 for class we found
that there is a complex motion response of a part in all Degrees of freedom with a directed input at a coordinate axes.
Sine Sweep Signal ResponseCalculated Response (Transmissibility) Relative to Q factor Sine Sweep Signal Response
• Digging further we know that Part under test will have a response through a range of frequencies through the Transmissibility relationship
Sine Sweep Signal Input (Actual)• Previously we showed the way
the Ramping of acceleration is determined.• The area of inspection for the
expected response about resonance is found In the Dwell area
Dwell Area
Ram
ping o
f
Acce
lerati
on
MAX G Allowed
Sine Sweep Signal ResponseTest Response of Two metal bars at different Lengths
• Knowing this we can set a pre-determined Sine Sweep signal Input to the part under test. • We “Plateau” the area of
interest in order to better further investigate the response area, and to have a Factor of Safety for the Acceleration input.
LET US NOT BREAK OUR PART
Response at Resonance
Sine Sweep Product Response
Vibration Test Set-Slip TableOne Example of Vibration table offering a Single DOF vibration
Axis
Vibration Test Set-Slip Table
Example of a Slip Table Things to note in Table setup• Control accel should be on the
farthest edge of the table and as close as possible to the product.• Multiple Control Accels can be used
and Averaged.• Accel should be Tri-axial in
configuration• Table should already be
characterized with support fixture
Vibration Test Set-Control Accel
Warning Limits Abort Limits+/- 30% of Expected Response +/- 40% of Expected Response
Software by Unholtz-Dickie Corporation VWIN II Vibration Control & Analysis System
Vibration Test Set-Control Accel
VibrationTest Set-Measurement Accels
• Parameters for individual Accel performance
VibrationTest Set-Measurement Accels
Additional Homework• The audience should take note that this is the simplest of vibration
tests. It is worth your energy to dig further in and understand how other tests are performed and why.• One in particular is called Random Testing. This is more
representative of what the product will see In the real environment.
References1. Kevin Napolitano, and Daniel Linehan [Multiple Sine Sweep Excitation for Ground Vibration Tests],
Proceedings of the IMAC-XXVII Society for Experimental Mechanics Inc, February 9-12, (2009).2. Connection Technology Center “Learn Basic Vibration Monitoring with CTCs Vibration University,” <
https://www.ctconline.com/__ctc_university.aspx?one=1 > (2012). 3. Dr. Paul Ibanez ANCO Engineers, Inc., "An Introduction to Shake Tables for Seismic Testing of Equipment And
Glossary of Vibration Terminology," ancoengineers.com, October 1st,(2008).
4. http://shodhganga.inflibnet.ac.in/bitstream/10603/2274/11/11_chapter%203.pdf, ch.3 Page 545. Unholtz-Dickie Corporation, Fixture Design Notes6. Unholtz-Dickie Corporation, VWIN II / VWIN XL / VWIN VIBRATION CONTROLLER OPERATING MANUAL7. Tom Irvine, http://www.vibrationdata.com/tutorials.htm
Auxiliary Slides
Auxiliary Slides-Sine Sweep Equations
Linear Sine Sweep input Y(t)=Sin{2}}Sweep Rate in terms of Octaves
Number of Octaves (cycles) in the Frequency Range to be swept
Table 1 Sine Sweep Rate Parameters
Auxiliary Plot Units/Slope
Simply an Octave is a doubling of the Frequency limits (think musical instruments).
Auxiliary Plot Response Example -Acceleration
Auxiliary Plot Response Example-Dislacement
http://nptel.iitm.ac.in/courses/105101004/downloads/04%20Chapter.pdf
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