Current And Recent
Research Projects
in the Integrated Acoustics Laboratory
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- Developement of the Integrated Acoustics
Laboratory
- Phase
II & III: Qualification
studies for a semi-anechoic chamber, reverberation room, and
associated instrumentation
- Sponsor: Ford Motor
Company
- Status: In progress
- Student: Tina Famighetti,
Patrick Saussus (Graduated, 2003)
- As part of a larger grant, The Georgia
Institute of Technology has received a commitment of an additional
$1,080,000 from the Ford Motor Company to construct Phase II
and III of the the Integrated Acoustics Laboratory. These phases
added a semi-anechoic and a reverberation room and associated
instrumentation to the existing resources of the lab. The instrumentation
foundation matches that of Phase I, using VXI-based systems.
The chambers have been built, and are now undergoing qualification!
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- Click here for a
more detailed description and images related to the qualification
component of this project
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- Active Control of Automotive Disc Brake
Squeal (In Progress)
- Sponsor: Integrated Acoustics
Laboratory, General Motors, Trelleborg
Students: Jeff Badertscher, Michael Michaux
- The objective of this project is to investigate
the use of dither control for the suppression of automotive disk
brake squeal. A brake dynamometer consisting of a 40 hp speed
controlled electrical motor, speed reducer and automotive 'floating'
brake caliper system. The dither signal is applied to the system
using a piezo-electric stack located in the brake piston. The
data acquisition system in place has the ability to measure the
braking pressure, brake pad temperature, the normal force on
the brake pads, braking torque, in-plane velocity of brake pads
and rotor and acoustic measures using a microphone. These parameters
will be used to determine the effect of dither control on the
effective braking torque and to better understand the system's
modal characteristics at the onset of brake squeal. Additional
experimental work will address improvements in the actuator control,
placement, power supply and control signals.
- Funding has recently been committed from
the National Science Foundation to conduct more fundamental investigations
into the mechanisms for dither suppression of brake squeal. The
project will involve significant theoretical and modeling activities
directed toward developing an improved comprehension of the dynamics
involved.
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- Click here for a
more detailed description and images related to the experimental
portion of this project
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- Click here for a
more detailed description and images related to the theoretical
portion of this project
- Structural Acoustic Optimization of
Complex Structures (In progress)
- Sponsor: NASA Langley
Structural Acoustics Branch, GSRP Program
Student: Wayne Johnson
The tailoring of composite material
properties for maximum strength, stiffness, and the like has
been addressed quite often in the literature. However, the design
of structures for optimal acoustic properties has been limited--and
even more so for composite structures. Of the few works addressing
structural acoustic optimization of composites, none fully explain
how or why certain designs of the properties lead to an improved
acoustic environment enclosed by structures such as cylindrical
shells. Further, it is unclear as to what mechanisms and design
trends control the interior acoustic environment. In light of
these uncertainties, this work intends to examine how the design
of a laminated composite cylindrical shell can be used to tailor
the structural acoustic coupling and acoustic environment of
the enclosed acoustic volume. For example, is there some particular
set of ply orientation and thus some stiffness distribution of
the cylinder leading to lower levels interior noise? Furthermore,
what is the best way to characterize the structural acoustic
coupling between the cylinder and the enclosed cavity? The approach
employed in this study consists of performing structural acoustic
optimizations of a composite cylindrical shell subject to external
harmonic monopole excitation, and with various ply angle design
variable formulations. The results of these analyses will then
be interpreted based on the decomposition of the interior acoustic
potential energy.
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- Click here for a more detailed description and images
- Investigations into state-switched
devices (In progress)
- Sponsor: Army Research
Office
Participants: Prof. Chris Lynch, Dr. Gregg Larson
- Student: Mark Holdhusen
A State-Switched Absorber (SSA) is
a device capable of instantaneously changing its stiffness, thus
it can switch between resonance frequencies, increasing its effective
bandwidth as compared to classical tuned vibration absorbers
for vibration control. In my masters thesis I considered the
experimental performance of the SSA for vibration suppression
of an elastically mounted lumped mass base. State switching was
achieved using magneto-rheological fluid to connect or disconnect
a coil spring in parallel with other coil springs by applying
or removing a magnetic field across of the MR fluid. Experiments
were performed over a range of forcing and tuning frequencies.
The SSA system, optimally tuned, outperformed the optimal classical
TVA system for all combinations of forcing frequencies. The thesis
also considered the role of damping in the state-switching concept
for a simple one-degree of freedom system and for a two-degree
of freedom system. Certain values of damping in the system
improve performance, while other values hinder the performance
of the state-switched absorber, as compared to classical absorbers.
In general, a state-switched absorber with optimized tuning and
damping is more effective at vibration suppression as compared
to a classical vibration absorber with optimized tuning and damping.
Currently, I am researching the performance of the state-switched
absorber in continuous systems. I am optimizing the performance
of the SSA using theoretical models that find the optimal tuning
frequencies and location along a continuous beam. Once the theoretical
optimization has been determined, an experimental study of the
performance of the SSA on continuous beams will be performed.
Continuous plates will be considered after the study of beams
has concluded.
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- Click here for a
more detailed description and images
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- Investigations of a Magnetorgheological
State-Switched Absorber (In progress)
- Sponsor: Army Research
Office and NSF
Participants: Prof. Chris Lynch, Dr. Gregg Larson
- Student: Anne-Marie Albanese
- This project involves the development
of a state-switched vibration absorber (SSA) with a magneto-rheological
(MR) silicone gel as a switchable spring element. When a magnetic
field is applied across the MR gel, its stiffness properties
change, thereby providing the means to switch the stiffness state
of the gel. The MR-based SSA considered here was developed to
operate at frequencies below 100 Hz, and to be of a size and
mass equivalent to classical tuned vibration absorbers (TVA),
with a mass of less than 100 g, and with no length dimension
larger than 10 cm. SSAs are single-degree-of-freedom mass-spring-damper
systems that have a controllably changeable element. Stiffness-switched
SSAs, with appropriate control algorithms, have been shown to
improve vibration control as compared to classical tuned vibration
absorbers, which are comprised of strictly passive elements.
An SSA with an appropriate control scheme is advantageous over
a TVA because it can attenuate vibration over a much larger bandwidth.
The research here focuses on developing an SSA that operates
in a low frequency range (<100 Hz), has a small volume, and
has a mass on the order of 100 g, and using MR silicone gels
as the switchable element.
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- Click here for a
more detailed description and images
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- Trabecular Bone (In progress)
- Participant:Kenneth Cunefare,
Robert Guldberg
Student: Gaylon Hollis
Sponsor: Georgia Tech
The objective of this project is to experimentally assess the
acoustic emission from trabecualar bone. The project
will incorparate a digital signal procressing system with a material
testing system to simultaneously acquire acoustic emission and
stress/strain data. The trabeculuar bone specimens
are cylindrical in shape and extracted from bovine femurs.
The motivation for the project is to further develop a non-invasive
technique for analyzing and reporting microdamage in trabecular
bone. Trabecular bone is the region most affected
by osteoporosis.
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- Click here for a
more detailed description and images
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- Past Projects
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