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.
𝐹 𝑥 = 𝐴𝑆𝑖𝑛(𝜔𝑡)
A Sine Sweep Signal Input
Types of Sine Sweeps
Typical Sine Sweep is a linear input
• The Sinusoidal Signal input can
be customized:
•
𝑓1(−1+2𝑅𝑡 )
Y(t)=Sin{2𝜋{
}}
𝑅 ln(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.
𝝎
𝐴𝒄𝒄𝒆𝒍𝒆𝒓𝒂𝒕𝒊𝒐𝒏 = 𝑽𝒆𝒍𝒐𝒄𝒊𝒕𝒚 ( 𝒌 )
Acceleration=Displacement
𝜔2
(𝑘)
Velocity= 𝒌*
𝑨𝒄𝒄
𝝎
Displacement=k*
𝐴𝑐𝑐𝑒𝑙
𝜔2
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 Response
Calculated 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)
Dwell Area
MAX G Allowed
• 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
Sine Sweep Signal Response
Test Response of Two metal bars at
different Lengths
Response at
Resonance
• Knowing this we can set a predetermined 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.
Sine Sweep Product Response
Vibration Test Set-Slip Table
One 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
Software by Unholtz-Dickie
Corporation
VWIN II Vibration Control &
Analysis System
Warning Limits
+/- 30% of Expected Response
Abort Limits
+/- 40% of Expected Response
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.
References
1.
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
5.
6.
7.
Unholtz-Dickie Corporation, Fixture Design Notes
Unholtz-Dickie Corporation, VWIN II / VWIN XL / VWIN VIBRATION CONTROLLER OPERATING MANUAL
Tom Irvine, http://www.vibrationdata.com/tutorials.htm
,
ch.3 Page 54
Auxiliary Slides
Table 1 Sine Sweep Rate Parameters
Auxiliary Slides-Sine Sweep Equations
Linear Sine Sweep input
Sweep Rate in terms of Octaves
Number of Octaves (cycles) in the Frequency
Range to be swept
Y(t)=Sin{2𝜋{
𝑓1(−1+2𝑅𝑡 )
}}
𝑅 ln(2)
𝑁
𝑡2 − 𝑡1
𝑓2
ln
𝑓1
𝑁=
ln(2)
𝑅=
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/0
4%20Chapter.pdf