Particle dampers provide a mechanism for diverting energy away from resonant structural vibrations. This experimental study provides data from trials to determine how effective use of these dampers might be for equipment mounted to a curved orthogrid vehicle panel. Trends for damping are examined for variations in damper fill level, component mass, and excitation energy. A significant response reduction at the component level would suggest that comparatively small, thoughtfully placed, particle dampers might be advantageously used in vehicle design. The results of this test will be compared with baseline acoustic response tests and other follow-on testing involving a range of isolation and damping methods. Instrumentation consisting of accelerometers, microphones, and still photography data will be collected to correlate with the analytical results

Craigmyle, Ben

Hunt, Ron

Knight, Brent

LaVerde, Bruce

Parsons, David

Smith, Andrew

NASA Technical Reports Server

 
American Institute of Aeronautics and Astronautics 
 
 
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Effect of Particle Damping on an Acoustically Excited 
Curved Vehicle Panel Structure with varied Equipment 
Assemblies 
 
David Parsons 1, Andrew Smith 2, and Brent Knight 3 
NASA, Marshall Space Flight Center, Huntsville, AL, 35612, USA 
Ron Hunt 4 
Triumph, ESTS Group, Huntsville. AL, 35612, USA 
Bruce LaVerde 5  
ERC, Huntsville, AL, 3561, USA 
Ben Craigmyle 6 
Jacobs ESTS Group, P.O. Box 9030, Huntsville, Alabama, 35812, USA 
Particle dampers provide a mechanism for diverting energy away from resonant 
structural vibrations.  This experimental study provides data from trials to determine how 
effective use of these dampers might be for equipment mounted to a curved orthogrid 
vehicle panel. Trends for damping are examined for variations in damper fill level, 
component mass, and excitation energy.  A significant response reduction at the component 
level would suggest that comparatively small, thoughtfully placed, particle dampers might be 
advantageously used in vehicle design. The results of this test will be compared with baseline 
acoustic response tests and other follow-on testing involving a range of isolation and 
damping methods. Instrumentation consisting of accelerometers, microphones, and still 
photography data will be collected to correlate with the analytical results.  
Nomenclature 
ESTS = Engineering, Science, and Technical Services 
MSFC = Marshall Space Flight Center 
NESC = NASA Engineering and Safety Center 
I. Introduction 
 
Highly energetic structural responses of lightly damped aerospace structures to acoustic fields present significant 
problems for the survivability of electronic equipment and the structural integrity of structural members.  For these 
structures, even a slight increase in available damping at the right location, could make a critical difference, by 
reducing the response at resonance.  Validating vibration environments estimates for equipment assembled to 
vehicle panels and refining analytical approaches used to estimate these environments, based on ground or flight 
tests, is of major importance to new vehicle programs.  The data from this experimental series should permit critical 
evaluation of the usefulness of particle dampers and suggest estimation methodology useful to the aerospace 
community.   
Marshall Space Flight Center (MSFC) completed a series of ground test cases using acoustic noise to excite a 
flight-like vehicle panel during December 2010.  Follow on tests are now under way that are intended to illustrate 
                                                          
1 Engineer, Thermal and Mechanical Analysis Branch (ES22), NASA Marshall Space Flight Center, Huntsville, Alabama, 35812 
2 Vibroacoustics Specialist, Loads and Strength Branch (EV31), NASA Marshall Space Flight Center, Huntsville, Alabama, 35812. 
3 Structural Dynamics Analyst, Thermal and Mechanical Analysis Branch (ES22), NASA Marshall Space Flight Center, Huntsville, Alabama, 
35812. 
4 Structural Dynamics Analyst, Triumph Aerospace, Supporting MSFC/ES22, Huntsville, AL. 
5 Vibroacoustics Lead Engineer, ERC, Supporting MSFC/EV31, Huntsville, AL. 
6 Structural Dynamics Analyst, Jacobs Engineering, 1500 Perimeter Parkway, Huntsville, AL, AIAA Member. 
https://ntrs.nasa.gov/search.jsp?R=20120014371 2019-08-30T22:13:52+00:00Z
 
American Institute of Aeronautics and Astronautics 
 
 
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differences in damping that may be expected when particle dampers are added to the configurations under test.  This 
paper will report on the damping trends observed from response measurements for several different test 
configurations and varying particle damper fill levels.  As well as answering the question of efficacy, the test has 
been designed to investigate the variation with excitation energy and the ratio of particle mass to component mass.  
Since the very configurations and levels under test are also being subjected to other damping/isolation methods, the 
collected data should inform analysts as to the relative merits of these methods. 
 
II. Test Overview 
 
The flight like test article used in acoustic ground testing at MSFC is constructed as an aluminum orthogrid rib 
stiffened panel.  It has a curved outer mold line that approximately represents a 45⁰ section comprising 1/8th of the 
cylindrical exterior shell of a launch vehicle.  The panel is clamped in a baffled condition separating the reverberant 
chamber from an anechoic room (i.e. a flight like condition where the exterior side of the panel is excited by the 
high energy acoustic field).  The panel is subjected to acoustic noise excitation energies simulating the liftoff and 
more roughly approximating the ascent flight events.  Note that fixing the baffled panel so that it is excited by 
source room energies on one side only, approximates the loading in service on the launch vehicle. Accelerometer, 
microphone, and strain gage data recorded the response of the panel as well as the transmission loss. 
 
The acoustic field was generated in the MSFC Reverberant Chamber using conditioned air which was driven 
using up to four parallel WAS 3000 Modulators which feed sound into the room through a single horn.  The acoustic 
field will be monitored using an array of microphones in front of the test article.  The standard configuration of 
microphones was to center them in each of six sectors 30 inches in front of the test article. This acoustic power 
source was utilized to approximate a diffuse acoustic field in a reverberant chamber.  A sketch of the test chamber 
showing the source and receiver rooms set up with the approximate location of the microphone sensor array is 
presented as Figure 1. 
 
 
 
 
Figure 1. Test Chamber Plan View. 
 
 
 
 
 
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The panel has a smooth outer surface with small orthogrid construction on the interior surface.  The material type 
is an aluminum 2219 alloy.  It is approximately 81 inches in height. The outer surface is described by a diameter of 
216.5 inches.  The arc length is approximately equivalent to one eighth of the full cylinder circumference, which is 
approximately 85 inches.  Pictures of the reverberant chamber showing the outer surface and the anechoic chamber 
showing the interior surface is presented as Figure 2 and Figure 3. 
 
 
 
 
Figure 2. Reverb-Side Integration of Test Article.   Figure 3. Anechoic-Side Integration of Test Article. 
 
III. Test Configurations 
 
Configurations for the test series include mass simulators that can be added to the orthogrid panel.  During the 
original rounds of testing, three major configurations were explored; bare panel, variations based on a small mass 
simulator, and variations based on a larger (28” x 36”) mass simulator. For the particle damping test series, the 
larger mass simulator was used.  The basic configurations include: 
 
1. Bare panel without particle dampers 
2. Panel with brackets and 4 particle dampers 
3. Panel with brackets, large mass simulator, and 4 particle dampers 
4. Panel with brackets, large mass simulator, one mass increment plate, and 4 particle dampers 
 
A picture of the large mass simulator configuration is presented in Figures 4.  Particle damper installation and 
assembly details can be seen in Figures 5 and 6.   
 
Within each basic test configuration, the fill level of the particle dampers was set to 0%, 30%, 60%, and 90% 
full.  Particle (steel shot) fill was achieved via an opening at the top of the damper housing, which was sealed via a 
bolt.  Additionally, each basic configuration, at each fill level, was exposed to four excitation levels wherein data 
was taken and recorded. 
 
 
 
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Figure 4. Anechoic-Side Integration of Test Article. 
 
 
 
 
 
 Figure 5. Installed Particle Damper on Mass Simulator 
 
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Figure 6. Particle Damper Assembly 
 
IV. Supporting Characterization of Measurements 
 
MSFC has used this test set up to produce significant sound pressure levels that elicit flight like levels of 
response in the test article system.  Figure 7 shows a plot of the average sound pressure spectrum recorded by the six 
microphones in the reverberant chamber.  Figure 8 presents response level for 5 configurations of the test article 
hardware that were tested without particle dampers.  These serve as a baseline response which will help to illustrate 
the attenuation of response provided when the particle dampers are included during the follow on test series. 
 
 
American Institute of Aeronautics and Astronautics 
 
 
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Figure 7. Example Average Liftoff Sound Pressure Level Repeated for Configurations with/without 
Particle Dampers. 
 
 
 
Figure 8. Reference Vibration Levels Prior to Addition of Particle Dampers- Response for Liftoff 
Acoustic Spectrum 
 
 
 
 
 
 
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V. Conclusions 
 
 
The results of this development test will examine the effect of particle damping on the vibro-acoustic response of 
a mounted panel and the surrounding support structure to the specified acoustic environments. The test data obtained 
will be used as a point of reference for different methods of reducing vibro-acoustic response.  
 
 
Acknowledgments 
The authors would like to acknowledge the fine support provided by the test organization at Marshall Space 
Flight Center.  The dedicated and capable staff of the ET40 department has provided outstanding support to 
complete an earlier set of ambitious acoustic response tests.  They have also been actively developing opportunities 
to leverage the test article and test setup toward valuable follow on tests.  The authors would also like to thank our 
Test integrator Mr. Anthony Kelley.  
 
References 
1 Rodgers, C., Brewster, S., Smith, A., et al., “Test and Checkout Procedure - ARES 1 Upper Stage - AD01-01 Instrument 
Unit and Aft Skirt Skin Section - Development Acoustic Test,” ARES 1-DEV-10-043, NASA-MSFC, September  2010. 
2 Smith, A., Harrison, P., LaVerde, B., Hunt, R., Teague, D., “AD01 Ground Acoustic Development Test, Initial Assessment 
Report, - Orthogrid Curved Panel Response To Acoustic Excitation - With/Without Mass Loading” NASA-MSFC-EV31, April, 
2011. 
3 Smith, A., Harrison, P., LaVerde, B., Hunt, R., Teague, D., “Preliminary Evaluation of Mass Loaded Vehicle Panel 
Response Estimates and Approaches Based on Acoustic Ground Test Results,” Proceedings of 2011 Aerospace Testing Seminar, 
March, 2011. 
4 Driskill, T., Rodgers, C., Brewster, S., et.al, “ARES 1 Upper Stage AD01 Instrument Unit and Aft Skirt Skin Section 
Development Acoustic Test, ARES 1-DEV-10-043A”, Memorandum ET40 (ET40-11-006), NASA, MSFC, ET40, February 23, 
2011. Kelley, A., Harrison, P., Smith, A., et al., “Test Plan - AD01-01 Instrument Unit (IU) and Aft Skirt (AS) Skin Section 
Acoustic Response Test,” CxP Ares-USO-TE-25142, NASA-MSFC, March 2011 
5 Peck, J., Smith, A., Fulcher, C.., LaVerde B., Hunt, R.., “Development of Component Interface Loads on a Cylindrical 
Orthogrid Vehicle Section from Test-Correlated Models of a Curved Panel,”  Proceedings of 2011 Spacecraft and Launch 
Vehicle Dynamic Environments Workshop, June 2011. 
 
 
 
 
 


Effect of Particle Damping on an Acoustically Excited Curved Vehicle Panel Structure with varied Equipment Assemblies

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