Page 36 - ASME_IMECE_2019_Program

Track 1: Acoustics, Vibration, and Phononics
1-14-1: ACOUSTICS, VIBRATION, AND PHONONICS
Wednesday, November 13, 9:45AM–10:30AM
Room 155C, Bio: William Parnell is a Professor of Applied Mathematics in
Calvin L. Rampton Salt Palace Convention Center
Hyperelastic Metamaterials and Phononic Media:
Stretching the Truth?
(IMECE2019-11006)
William Parnell
University of Manchester (UK)
xxxiv Abstract: Transformation theory is an established mechanism
for the design of metamaterials. It gives rise to the required
material properties of the medium in order to direct waves in
the manner desired. This talk will focus on the mathematical
theory underpinning the design of both acoustic and
elastodynamic metamaterials and phononic media, based on
transformation theory, and some aspects of the experimental
confirmation of these designs. In the acoustics context it is well
known that the governing equations are transform invariant and
therefore a whole range of microstructural options are available
for material design; although in reality, fabricating materials
that can harness incoming acoustic energy in air is difficult
due to the usual sharp impedance contrast between air and
the metamaterial in question. In the elastodynamic context
the situation is even worse, because the governing equations
are not even transform invariant and therefore a new class of
materials is required. In the acoustics context we will describe
a new microstructure consisting of an array of rigid rods that is
closely impedance matched to air and slows down sound in air.
This is shown to be useful in a number of configurations, and in
particular, it can be employed to halve the resonant frequency
of the standard quarter-wavelength resonator. Alternatively,
it can halve the size of the resonator for a specified resonant
frequency. Extensions to three-dimensional configurations will
also be discussed. In the elastodynamics context we will
show that, although the equations are not transformation
invariant, one can employ the theory of waves in pre-stressed,
hyperelastic materials in order to create natural elastodynamic
metamaterials whose inhomogeneous anisotropic material
properties are generated naturally by an appropriate pre-stress.
In particular, it is shown that a certain class of hyperelastic
materials exhibits this so-called invariance property permitting
the creation of, e.g., hyperelastic cloaks and invariant
metamaterials. This has significant consequences for the
design of, e.g, phononic media: it is a well-known and
frequently exploited fact that pre-stress and large deformation
of hyperelastic materials modifies the linear elastic wave speed
in the deformed medium. In the context of periodic materials,
this renders materials whose dynamic properties are “tunable”
under pre-stress and, in particular, this permits tunable band
gaps in periodic media. However, the invariant hyperelastic
materials described above can be employed in order to design
a class of phononic media whose band gaps are invariant to
deformation. Finally, we describe the accommodation of
viscoelasticity in the theory of hyperelastic metamaterials.
Incorporating this effect into models is crucial given that soft
materials, capable of large deformation, are inherently lossy.
the School of Mathematics at the University of Manchester
(UK) and holds an EPSRC Research Fellowship. He received a
First Class degree in Applied Mathematics from the University
of Bristol (UK) in 1999, before moving to the University of
Oxford (UK) to study for a Masters in Mathematical Modelling
and Scientific Computing, graduating with distinction in 2000.
After a year travelling he began a Ph.D. in 2001 at the
University of Manchester under the supervision of I. David
Abrahams (now Director of the Isaac Newton Institute at the
University of Cambridge), completing this in 2004. Parnell’s
research interests reside principally in the development of
new mathematical techniques to understand the mechanical
properties of inhomogeneous materials and the dynamic
behaviour of particulate media. More recently his work has
involved linking theory with experiments in order to develop
new composites and metamaterials. He has a particular
interest in understanding the constitutive behaviour of complex
soft solids and tuning this via novel fillers. He leads the
Mathematics of Waves and Materials (MWM) research group
at Manchester, which consists of a thriving group of Postdocs,
Ph.D. students and Master’s students. Parnell has held visiting
positions at Universite Paris 6 and 12 (France), University of
Trento (Italy), University of Oxford (UK), and Colorado School
of Mines and Rutgers (USA). He has published more than
60 research papers and two book chapters. He is a Fellow
of the Institute of Mathematics and its Applications (UK),
is the founding director of the Manchester Materials Modelling
Centre, and became Editor in Chief of the journal Wave Motion
in 2017.
Track 2: Advanced Manufacturing
2-1-1: ADVANCED MANUFACTURING
Monday, November 11, 9:45AM–10:30AM
Room 155C,
Calvin L. Rampton Salt Palace Convention Center
Finishing Freeform Surfaces, a New Surface
Characterization Approach, and Future Trends in
Manufacturing
(IMECE2019-13991)
Brigid Mullany
National Science Foundation
Abstract: Dr. Brigid Mullany will provide insights on the
challenges of fabricating and finishing freeform surfaces.
Specifics will focus on a novel fiber-based tool capable of
eliminating tool path marks from earlier process steps in the
fabrication of optical quality components. She will also provide
insights on how common statistical metrics can be used
to provide spatial information regarding surface texture,
and defect detection. Based on her time as a program director