Eiichi Nishida, Professor Mem', ASME

1
Title
Designing Broad-band Vibration Absorbers for
Structural Noise Control
Eiichi Nishida, Professor Mem., ASME Department
of Mechanical System Engineering, Shonan
Institute of Technology G.H. Koopmann,
Professor, Fellow, ASME Center for Acoustics and
Vibration, Department of Mechanical
Engineering, Pennsylvania State University
2
Subjects of Presentation

• 1 Background
• What is BBVA ?
• Function of BBVA
• Issues to be solved
• Derivation of BBVA Impedance
• Experimental Validation
• 5 Conclusions

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1 Background
What is BBVA ? Function of BBVA Issues to
be solved
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What is BBVA ?
Fig. 1. Photo of BBVA (Broad Band Vibration
Absorber)
Reduce radiated acoustic power by vibration
suppression
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Function of BBVA
V velocity F reaction force
shell structure
Impedance ZF/V (Scalar)
natural freq. of elements
Impedance Z ( Ns/m)
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Issue 1 rotational behavior
Impedance ZF/V (Scalar)
Transverse Excitation
33 Impedance Matrix
Rotational Excitation added
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Example data of rotational effect
Experiment
FE Model including BBVA
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Effect of rotational component
FE with rotational terms
Experiment
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Structural - Acoustic Optimization II Sound Power
Optimization Program
FEM(NASTRAN) or Experiment Eigenvectors
?nEigenvalues ?n
Issue 2 Computationally light model of BBVA
FE Model is not suitable
Initialize Mass Distributionmj(xr) or
Dynamicabsorbere
Solve the Eigenvalue Problem for ??n and ??n
Tuning and Relocation of BBVA
Calculate Velocity Distribution
NO
Get Optimal Point Mass Values mj
YES
Calculate Radiated Sound Power using
POWER (High performance calculation algorithm)
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2 Derivation of BBVA Impedance
Target of the study Logic flow of formula
derivation
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Target of study
To derive analytical 33 Impedance Matrix Zij f(
structural parameters of BBVA)
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Logic flow of impedance formula derivation
local flexibility
(Detail of formula equations are shown in the
proceedings)
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Experimental Validation
Issues to identify BBVA impedance Experimental
setup Results of experiment Comparison between
experiment simulation
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Issues to identify BBVA impedance
Issues for design of experimental device How to
achieve rotational excitation ? How to measure
moment data ? How much information is enough to
identify the impedance matrix ? ? 3 input 3
output data
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Experimental setup for identification of impedance
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Equation for data processing
Hub (Polystyrene, rh113mm, lh12m)
y
2
1
Spring
3
12mm
x
Equation of motion
Equation for data processing
Z BBVA impedance matrix H FRF matrix
achieved by experiment Mp, Cp, Kp mass,
damping, stiffness matrices for plate xp
displacement of plate TY, TL transformation
matrices
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Measured frequency response spectra of BBVA
prototype impact tests
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Comparison of Impedance of experimental
identification and analytical model
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Comparison of experimental identification and
analytical model
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An example of BBVA impedance in the actual
applications
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Conclusion
broadband vibration absorbers (BBVA), both
analytical and experimental modeling method were
investigated.
7 Conclusion
Emphasis was directed to the rotational behavior
which is important for noise control of shell
structures.
E.Nishida, Vib04-1070
Both methods were applied to a BBVA prototype
and for a comparative study and showed good
agreement