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

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Acce

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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