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1.
Grunschel, Stephen E.
Pressure-Shear Plate Impact Experiments on High-Purity
Aluminum at Temperatures Approaching Melt.
Degree: PhD, Division of Engineering. Mechanics of
Solids, 2009, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:73/
► High-temperature, pressure-shear plate impact experiments were conducted in order to measure the plastic response of high-purity aluminum at high strain rates (106 s-1) and at…
(more)
▼ High-temperature, pressure-shear plate impact
experiments were conducted in order to measure the plastic response
of high-purity aluminum at high strain rates (106 s-1) and at
temperatures approaching melt. In similar experiments by Frutschy
and Clifton (JMPS 46, 1998, 1723-1743) on OFHC copper, the flow
stress decreases with increasing temperature and increases with
increasing strain rate over the full range of temperatures and
strain rates examined. No conclusive evidence of a change in
rate-controlling mechanism was obtained. In the current study,
temperatures that are larger fractions of the melting temperature
were accessible because of the lower melting point of aluminum.
Because the melting temperature of aluminum is pressure dependent,
and a typical pressure-shear plate impact experiment subjects the
sample to large pressures (2 GPa ? 7 GPa), a pressure-release type
experiment was used to reduce the pressure in order to measure the
shearing resistance at temperatures up to 95% of the current
melting temperature. Again, no conclusive evidence of a change in
rate-controlling mechanism was obtained. The measured shearing
resistance was remarkably large (~50 MPa at a shear strain of 2.5)
for temperatures this near melt. Numerical simulations of the
high-temperature plate impact experiments show that heat conduction
can affect the sample temperature significantly, despite the short
duration of the test (~2 µs). Simulations conducted using a version
of the Nemat-Nasser/Isaacs constitutive equation (Acta Materialia
45(3), 1997, 907-919), modified to model the mechanism of geometric
softening, appears to capture adequately the hardening/softening
behavior observed experimentally.
Advisors/Committee Members: Clifton, Rodney (director), Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (reader),
Briant, Clyde (reader).
Subjects/Keywords: high-temperature
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MLA ·
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APA (6th Edition):
Grunschel, S. E. (2009). Pressure-Shear Plate Impact Experiments on High-Purity
Aluminum at Temperatures Approaching Melt. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:73/
Chicago Manual of Style (16th Edition):
Grunschel, Stephen E. “Pressure-Shear Plate Impact Experiments on High-Purity
Aluminum at Temperatures Approaching Melt.” 2009. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:73/.
MLA Handbook (7th Edition):
Grunschel, Stephen E. “Pressure-Shear Plate Impact Experiments on High-Purity
Aluminum at Temperatures Approaching Melt.” 2009. Web. 20 Apr 2021.
Vancouver:
Grunschel SE. Pressure-Shear Plate Impact Experiments on High-Purity
Aluminum at Temperatures Approaching Melt. [Internet] [Doctoral dissertation]. Brown University; 2009. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:73/.
Council of Science Editors:
Grunschel SE. Pressure-Shear Plate Impact Experiments on High-Purity
Aluminum at Temperatures Approaching Melt. [Doctoral Dissertation]. Brown University; 2009. Available from: https://repository.library.brown.edu/studio/item/bdr:73/
2.
Gerbig, Daniel Edward.
Measuring and Modeling the Behavior of High-Strength
Steels.
Degree: PhD, Mechanics of Solids, 2016, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:674361/
► The automobile industry drives a great deal of research towards understanding the mechanical behavior of high-strength steels. Two important behaviors exhibited by these materials are…
(more)
▼ The automobile industry drives a great deal of
research towards understanding the mechanical behavior of
high-strength steels. Two important behaviors exhibited by these
materials are plastic deformation and failure by fracture.
Measuring and modeling these behaviors accurately is critical for
the design of safe and lightweight vehicles. Measuring the plastic
stress-strain behavior of a material traditionally relies on
tensile testing of straight-gauge dogbone specimens and is limited
to cases where the strains are uniform and the stress can be
directly calculated from the measured load and the nominal
cross-sectional area of the specimen. An investigation is presented
which studies the use of nonuniform strain measurements in the
necking region to approximate the true stress-strain behavior. A
new analytical method combining digital image correlation with
finite element analysis is then presented which is used for
extracting stress-strain behavior from necking tensile specimens.
The approach is to minimize the difference between measured and
computed displacement fields and external forces applied to the
specimen by iteratively correcting the material parameters in the
chosen constitutive model. In the case of failure by fracture, the
behavior of multiphase high-strength steels is controlled by the
properties of the constituent phases, and microstructural features,
such as the volume fraction of the phases, their size and
morphology. The analysis of two steels that have significantly
different microstructures, but very similar uniaxial tensile
stress-strain response is presented. Finite element simulations are
used to compute the evolution of damage due to void nucleation,
growth, and coalescence, leading to ductile fracture. The role of
individual phases in controlling the fracture resistance of these
steels is analyzed using a set of "virtual" microstructures with
varying volume fractions and flow behavior of the two phases in the
steels.
Advisors/Committee Members: Bower, Allan (Director), Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (Reader),
Kumar, K. Sharvan (Reader).
Subjects/Keywords: finite element analysis
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Gerbig, D. E. (2016). Measuring and Modeling the Behavior of High-Strength
Steels. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:674361/
Chicago Manual of Style (16th Edition):
Gerbig, Daniel Edward. “Measuring and Modeling the Behavior of High-Strength
Steels.” 2016. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:674361/.
MLA Handbook (7th Edition):
Gerbig, Daniel Edward. “Measuring and Modeling the Behavior of High-Strength
Steels.” 2016. Web. 20 Apr 2021.
Vancouver:
Gerbig DE. Measuring and Modeling the Behavior of High-Strength
Steels. [Internet] [Doctoral dissertation]. Brown University; 2016. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:674361/.
Council of Science Editors:
Gerbig DE. Measuring and Modeling the Behavior of High-Strength
Steels. [Doctoral Dissertation]. Brown University; 2016. Available from: https://repository.library.brown.edu/studio/item/bdr:674361/
3.
Waters, Julie F.
Contact mechanics of biologically-inspired interface
geometries.
Degree: PhD, Division of Engineering. Mechanics of
Solids, 2009, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:122/
► The mechanics of biological contact are important in many natural processes, motivating extensive study of biological adhesive systems as well as attempts at biomimickry through…
(more)
▼ The mechanics of biological contact are important in
many natural processes, motivating extensive study of biological
adhesive systems as well as attempts at biomimickry through
microfabricated adhesive surfaces. Improved understanding of the
physical mechanisms of biological adhesion is essential for further
progress in the design of advanced adhesive systems so that natural
systems are not just copied, but are ultimately improved upon. The
work presented here focuses on two broad classes of biological
contact problems related to the key design variables of surface
topography and material properties: geometric adhesion enhancement,
where the force and/or work required to separate two surfaces are
increased solely through the surface geometry, and mixed mode
adhesive contact, i.e., combined normal and tangential loading or
straining, of viscoelastic or otherwise dissipative adhesive
interfaces. An analytical contact model for axisymmetric concave
surfaces is shown to predict higher adhesive pull-off forces for a
range of these geometries than for flat punches of equal size, and
experiments on gelatin validate the predictions of the model.
Axisymmetric sinusoidal wavy surfaces are also studied
analytically, and it is shown that low-amplitude waviness can
enhance adhesion through both strengthening and toughening of the
interface. A model is developed for the wavy surface so that the
adhesive pull-off forces in the JKR-DMT transition regime can be
studied, and significant adhesion enhancement due to surface
topography is seem to be limited to the JKR regime. Mixed mode
adhesive contact is studied by introducing a phenomenological model
for increased effective work of adhesion with increasing phase
angle of mode mixity, allowing the energy dissipation due to
viscoelasticity or irreversible interfacial processes seen in
contact experiments of glass spheres on PDMS to be captured. This
phenomenological model is incorporated into an analysis of mixed
mode contact of axisymmetric wavy surfaces, and the mechanisms
which enhance adhesion are shown to be linked to enhanced static
sliding resistance. These results highlight the importance of
surface topography and material behavior in adhesive
contact.
Advisors/Committee Members: Guduru, Pradeep (director), Gao, Huajian (reader), Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (reader).
Subjects/Keywords: concave surfaces
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Waters, J. F. (2009). Contact mechanics of biologically-inspired interface
geometries. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:122/
Chicago Manual of Style (16th Edition):
Waters, Julie F. “Contact mechanics of biologically-inspired interface
geometries.” 2009. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:122/.
MLA Handbook (7th Edition):
Waters, Julie F. “Contact mechanics of biologically-inspired interface
geometries.” 2009. Web. 20 Apr 2021.
Vancouver:
Waters JF. Contact mechanics of biologically-inspired interface
geometries. [Internet] [Doctoral dissertation]. Brown University; 2009. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:122/.
Council of Science Editors:
Waters JF. Contact mechanics of biologically-inspired interface
geometries. [Doctoral Dissertation]. Brown University; 2009. Available from: https://repository.library.brown.edu/studio/item/bdr:122/
4.
Torres , Jahn Ramon.
Adhesion in Hydrogel Contacts.
Degree: PhD, Mechanics of Solids, 2015, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:419414/
► A generalized thermoelastic model for adhesion was developed to elucidate the mechanism of dissipation within the viscoelastic bulk of a hydrogel. Results show that in…
(more)
▼ A generalized thermoelastic model for adhesion was
developed to elucidate the mechanism of dissipation within the
viscoelastic bulk of a hydrogel. Results show that in addition to
the expected energy release rate of interface formation as well as
the viscoelastic drag and viscous flow dissipation, the bulk
composition exhibit dissipation due to phase inhomogeneity motion.
The mixing thermodynamics of the matrix and solvent composition
determine the dynamics of the phase inhomogeneities, which can
enhance or disrupt adhesion. The model also accounts for the time
dependent behavior since, given enough time, these inhomogeneities
can be influenced by image forces at the interface causing
migration, which may in turn, affect the dissipation at the
interface. A nondimensional parameter is proposed to discern the
dominant dissipation mechanism in hyperelastic contact
detachment.
Advisors/Committee Members: Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (Director),
Jay, Gregory (Reader),
Franck, Christian (Reader).
Subjects/Keywords: contacts
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Torres , J. R. (2015). Adhesion in Hydrogel Contacts. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:419414/
Chicago Manual of Style (16th Edition):
Torres , Jahn Ramon. “Adhesion in Hydrogel Contacts.” 2015. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:419414/.
MLA Handbook (7th Edition):
Torres , Jahn Ramon. “Adhesion in Hydrogel Contacts.” 2015. Web. 20 Apr 2021.
Vancouver:
Torres JR. Adhesion in Hydrogel Contacts. [Internet] [Doctoral dissertation]. Brown University; 2015. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:419414/.
Council of Science Editors:
Torres JR. Adhesion in Hydrogel Contacts. [Doctoral Dissertation]. Brown University; 2015. Available from: https://repository.library.brown.edu/studio/item/bdr:419414/
5.
Teller, Sean S.
High Frequency Viscoelasticity of Soft Materials at Low to
Moderate Strains with Implications for Vocal Fold Tissue
Engineering.
Degree: PhD, Solid Mechanics, 2013, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:320465/
► Vocal folds are driven in a shear-dominated, wave-like motion at high frequencies (100-1000 Hz) at strains up to 30% during phonation. Damage to the vocal…
(more)
▼ Vocal folds are driven in a shear-dominated, wave-like
motion at high frequencies (100-1000 Hz) at strains up to 30%
during phonation. Damage to the vocal folds may cause significantly
stiffer scar tissue to form, impairing voice function. Due to the
biomechanically active nature of the tissue, candidate
tissue-engineered replacement materials must have mechanical
properties (i.e. viscoelastic shear modulus) that are similar to
those of native tissues. The torsional wave experiment (TWE), a
stress-wave based resonance test, was used to determine the linear
viscoelastic complex shear modulus of human and porcine vocal folds
up to low audio frequencies, while histology investigated the
structure-property relationship. Human tissues were harvested from
adult males and females between 39 and 93 years of age, while
porcine tissues were from fetal, newborn, adolescent, and adult
pigs. Adult porcine tissues had an average storage modulus of
2207+1440 Pa with a loss tangent of 0.38+0.10, while human vocal
folds had an average storage modulus and loss tangent of 824+479 Pa
and 0.42+0.10, respectively. Viscoelastic moduli did not exhibit
gender dependence in either human or porcine vocal folds, although
age dependence was found in porcine tissues. Histology of porcine
tissues similarly showed a dependence on age.
A finite strain torsional wave experiment was developed that
superposes high-frequency, infinitesimal deformations on a
low-frequency, finite-strain deformation. This experiment enables
the determination of a complex viscoelastic tangent shear modulus
at a known pre-strain. In addition to enabling measurements at
finite strain, the new experiment increased the resonance frequency
of the system― allowing for measurements at higher frequencies than
those obtained in the TWE. Experiments were performed on 0.45%
(w/v) agarose gels at pre-strains up to 80%; the storage modulus
did not change with applied pre-strain while the loss tangent
increased. Future work includes reducing the time to perform the
experiments, extending the strain and frequency test ranges, and
collecting data on natural tissues.
Advisors/Committee Members: Clifton, Rodney (Director), Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (Reader),
Tripathi, Anubhav (Reader).
Subjects/Keywords: vocal folds
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Teller, S. S. (2013). High Frequency Viscoelasticity of Soft Materials at Low to
Moderate Strains with Implications for Vocal Fold Tissue
Engineering. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:320465/
Chicago Manual of Style (16th Edition):
Teller, Sean S. “High Frequency Viscoelasticity of Soft Materials at Low to
Moderate Strains with Implications for Vocal Fold Tissue
Engineering.” 2013. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:320465/.
MLA Handbook (7th Edition):
Teller, Sean S. “High Frequency Viscoelasticity of Soft Materials at Low to
Moderate Strains with Implications for Vocal Fold Tissue
Engineering.” 2013. Web. 20 Apr 2021.
Vancouver:
Teller SS. High Frequency Viscoelasticity of Soft Materials at Low to
Moderate Strains with Implications for Vocal Fold Tissue
Engineering. [Internet] [Doctoral dissertation]. Brown University; 2013. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:320465/.
Council of Science Editors:
Teller SS. High Frequency Viscoelasticity of Soft Materials at Low to
Moderate Strains with Implications for Vocal Fold Tissue
Engineering. [Doctoral Dissertation]. Brown University; 2013. Available from: https://repository.library.brown.edu/studio/item/bdr:320465/
6.
Shi, Xinghua.
Theoretical and Molecular Dynamics Simulation Studies on the
Mechanics of Carbon Nanomaterials-Based Nano/Bio-Systems.
Degree: PhD, Solid Mechanics, 2011, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:11181/
► Through coarse grained molecular dynamics (CGMD) simulations and theoretical models, we show that, depending on the radius, a carbon nanotube can enter a cell either…
(more)
▼ Through coarse grained molecular dynamics (CGMD)
simulations and theoretical models, we show that, depending on the
radius, a carbon nanotube can enter a cell either by wrapping into
the cell membrane or by directly piercing through the membrane. We
find that MWCNTs tend to enter the cell via a tip entry mechanism
with the final entry angle determined by the curved membrane
induced torque that tends to rotate the nanotube to a large entry
angle, which may lead to frustrated endocytosis and even cell
death. We also conduct MD simulations to understand the stiffness
effect in adhesive wrapping of an elastic vesicle by a membrane.
Generally, stiffer particles require lower adhesion strength to
achieve full wrapping and it is more difficult for a cell to engulf
softer vesicles. Through theoretical model and MD simulations, we
investigate the basic structure of a carbon nanoscroll and derived
an analytical relation between the surface energy, the bending
stiffness, the interlayer spacing, the length of the basal graphene
sheet, the pressure difference between the inner and outer core of
CNS and the core radius of the resulting CNS. We develop a
theoretical model to describe the "breathing" oscillatory motion of
a CNS, and have validated the theory with MD simulations. It is
found that the gigahertz oscillation of CNS can be controlled by
tuning the effective surface energy of the system via an applied
DC/AC electric field. A controllable translational nanoactuator
based on the rolling and unrolling motion of CNS on a substrate is
proposed and investigated by both theoretical modeling and MD
simulations. It is suggested that CNS based linear nanoactuator can
be controlled by tuning the effective surface energy of the system
via an applied DC/AC electric field. We conduct MD simulations of a
novel class of tunable water channels based on CNSs and show that
it is possible to use dipole-dipole interaction induced by an
externally applied electric field to reduce the effective surface
energy of a CNS, so as to controllably increase its core size and
the associated water flow rate.
Advisors/Committee Members: Gao, Huajian (Director), Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (Reader),
Hurt, Robert (Reader).
Subjects/Keywords: carbon nanoscrolls
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Shi, X. (2011). Theoretical and Molecular Dynamics Simulation Studies on the
Mechanics of Carbon Nanomaterials-Based Nano/Bio-Systems. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:11181/
Chicago Manual of Style (16th Edition):
Shi, Xinghua. “Theoretical and Molecular Dynamics Simulation Studies on the
Mechanics of Carbon Nanomaterials-Based Nano/Bio-Systems.” 2011. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:11181/.
MLA Handbook (7th Edition):
Shi, Xinghua. “Theoretical and Molecular Dynamics Simulation Studies on the
Mechanics of Carbon Nanomaterials-Based Nano/Bio-Systems.” 2011. Web. 20 Apr 2021.
Vancouver:
Shi X. Theoretical and Molecular Dynamics Simulation Studies on the
Mechanics of Carbon Nanomaterials-Based Nano/Bio-Systems. [Internet] [Doctoral dissertation]. Brown University; 2011. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:11181/.
Council of Science Editors:
Shi X. Theoretical and Molecular Dynamics Simulation Studies on the
Mechanics of Carbon Nanomaterials-Based Nano/Bio-Systems. [Doctoral Dissertation]. Brown University; 2011. Available from: https://repository.library.brown.edu/studio/item/bdr:11181/
7.
Zhao, Ruike.
A Mechanics Study on Surface Ruga Morphologies of Soft
Materials.
Degree: PhD, Mechanics of Solids, 2016, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:674263/
► The surface morphologies of different soft material systems comprise various ruga phases (wrinkle, crease, fold or ridge). In the past a few decades, despite that…
(more)
▼ The surface morphologies of different soft material
systems comprise various ruga phases (wrinkle, crease, fold or
ridge). In the past a few decades, despite that one-phase specific
studies have revealed certain intrinsic properties of some ruga
phases, their evolutions and transitions between each other are
still unclear. In this thesis, finite element analysis (FEA) is
used to study soft-material surface deformation of a homogeneous
half space, and one or multilayer thin film(s) on a substrate,
every component of which is represented by an incompressible
neo-Hookean solid. Furthermore, experiments are carried out by a
self-tightening loading device to verify the distinct morphologies.
Based on the simulation results, we construct the primary bilayer
(PB) ruga-phase diagram which guides manipulation of various ruga
configurations in bilayer systems. On the PB ruga-phase diagram,
various phase boundaries represent bifurcation sites of ruga
structures caused by lateral compression of the bilayer. All the
ruga phases eventually evolve to a limit phase of either global
crease or global fold localization, depending on the stiffness
ratio of the bilayer, when compressed up to the Biot critical
strain of 0.456. Moreover, the substrate pre-stretch promotes
ridging of bilayers and ruga mode-period multiplications during
loading. The ridging is intrinsically growth limited and highly
dependent on both substrate pre-stretch and modulus ratio of the PB
system. Configuration-mobility bifurcation of ridges, caused by
symmetry breaking of individual ridge configuration, leads to
order-disorder transition in the system. We pointed out two
irreversibility types for a bilayer system with a stiff film.
Irreversibility is typically exhibited through either mode locking
or primary period switching. The former leads to cyclic hysteresis
of ruga configurations during a loading/unloading cycle of the PB
system without strain mismatch. The latter exhibits snap jumps in
the PB ruga-phase transitions, enhanced by substrate pre-stretch
and sufficient viscoelastic loss tangent. With multi-layered or
graded modulus structure, ridging can be suppressed, and hierarchal
wrinkle wavelengths can be observed during loading. Along this
line, we summarize the ruga morphology control aspects and
corresponding controlling factors.
Advisors/Committee Members: suk%22%29&pagesize-30">
Kim,
Kyung-
suk (Director),
Gao, Huajian (Reader),
Franck, Christian (Reader).
Subjects/Keywords: ruga-phase diagram
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Zhao, R. (2016). A Mechanics Study on Surface Ruga Morphologies of Soft
Materials. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:674263/
Chicago Manual of Style (16th Edition):
Zhao, Ruike. “A Mechanics Study on Surface Ruga Morphologies of Soft
Materials.” 2016. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:674263/.
MLA Handbook (7th Edition):
Zhao, Ruike. “A Mechanics Study on Surface Ruga Morphologies of Soft
Materials.” 2016. Web. 20 Apr 2021.
Vancouver:
Zhao R. A Mechanics Study on Surface Ruga Morphologies of Soft
Materials. [Internet] [Doctoral dissertation]. Brown University; 2016. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:674263/.
Council of Science Editors:
Zhao R. A Mechanics Study on Surface Ruga Morphologies of Soft
Materials. [Doctoral Dissertation]. Brown University; 2016. Available from: https://repository.library.brown.edu/studio/item/bdr:674263/
8.
Wang, Chien-Kai.
Grain Boundary Field Projection Method and Atomic Lattice
Interferometer for Nanometrology.
Degree: PhD, Mechanics of Solids, 2014, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:386259/
► The aim of this thesis is to investigate how grain boundary (GB) strength and separation mechanisms affect strength and ductility of nanocrystalline materials. Such nanoscale…
(more)
▼ The aim of this thesis is to investigate how grain
boundary (GB) strength and separation mechanisms affect strength
and ductility of nanocrystalline materials. Such nanoscale
materials are highly nonlinear and thus have different energy
profiles in different atomic configurations. Therefore, failure of
GBs under straining is highly cooperative and process-dependent in
nano-granular materials. To ascertain the strength and toughness of
GBs, accurate and quantitative assessments of GB field descriptions
with atomic features are required. Two new means of establishing
connections between global loadings to nanoscale GB traction
distributions are developed: the interior and exterior field
projection methods of GBs for computation and experiment
respectively. Three mechanisms of Cu symmetric tilt GB deformation
are introduced through the GB field projection methods. First,
symmetric atomic rearrangement reduces concentrated compression of
the GB tractions due to the ease of intergranular incompatibility.
Second, asymmetric atomic rearrangement or dislocation emission
decreases the concentrated tension leading GB opening and triggers
the shear traction fluctuations as a new strain energy reservoir.
Thus the GB separation toughness is enhanced. Third, Pb impurities
at the GBs maintain the tension peaks of normal traction
fluctuations and then retard the traction transformation. Hence,
the GB becomes brittle. In addition to the GB field projection
methods, we introduce an invention of an experimental instrument –
atomic lattice interferometer, which can give us sub-angstrom scale
resolution of deformation measurement. The corresponding
calibration experiments were implemented on highly ordered
pyrolytic graphite (HOPG), and the atomic-scale strain fields of a
crinkle structure in HOPG were successfully measured. The
measurement results show that the crinkle ridge line has a highly
concentrated surface curvature involving localized atomic-scale
deformations. With the help of simulation-assisted data analyses,
the experimental data reveal that the typical width, the kink angle
and the minimum radius of the ridge as 1.76 nm, 6.2° and 8.51 nm,
respectively. In summary, this thesis develops novel scientific
computational projection methods and experimental metrology
instrument for investigating unexplored global physical phenomena
of materials associated with minute and localized atomic
deformation at nanometer scales.
Advisors/Committee Members: Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (Director),
Gao, Huajian (Reader),
Kumar, Sharvan (Reader).
Subjects/Keywords: Grain boundary
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Export
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APA (6th Edition):
Wang, C. (2014). Grain Boundary Field Projection Method and Atomic Lattice
Interferometer for Nanometrology. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:386259/
Chicago Manual of Style (16th Edition):
Wang, Chien-Kai. “Grain Boundary Field Projection Method and Atomic Lattice
Interferometer for Nanometrology.” 2014. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:386259/.
MLA Handbook (7th Edition):
Wang, Chien-Kai. “Grain Boundary Field Projection Method and Atomic Lattice
Interferometer for Nanometrology.” 2014. Web. 20 Apr 2021.
Vancouver:
Wang C. Grain Boundary Field Projection Method and Atomic Lattice
Interferometer for Nanometrology. [Internet] [Doctoral dissertation]. Brown University; 2014. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:386259/.
Council of Science Editors:
Wang C. Grain Boundary Field Projection Method and Atomic Lattice
Interferometer for Nanometrology. [Doctoral Dissertation]. Brown University; 2014. Available from: https://repository.library.brown.edu/studio/item/bdr:386259/
9.
Chinthapenta, Viswanath R.
Theoretical Modeling of Lattice Strain Partitioning in
Nanocrystalline FCC Metals.
Degree: PhD, Solid Mechanics, 2012, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:297639/
► In nanocrystalline materials it is well postulated that the grain boundary phenomena such as dislocation emission/annihilation, partial nucleation, grain-boundary (GB) sliding, and GB diffusion dominate…
(more)
▼ In nanocrystalline materials it is well postulated
that the grain boundary phenomena such as dislocation
emission/annihilation, partial nucleation, grain-boundary (GB)
sliding, and GB diffusion dominate the deformation behavior of
nanocrystalline materials. State of art TEM observations Kumar et
al. 2003. only provide qualitative information on deformation
mechanism and hence difficult to compare with simulations.
Alternative techniques like synchrotron x-ray and neutron
diffraction provide quantitative assessment of deformation
mechanisms by measuring the evolution of lattice and intergranular
strain. Recent studies Li et al. 2008,Cheng et al. 2009 used these
techniques to determine the evolution of intergranular strain.
Using our continuum mechanistic modeling of nc-materials we
provided insights to these neutron diffraction experiments by
studying the evolution of lattice strain systematically over all
the possible deformation regimes in nc materials. From our studies
we observe that intergranular strain exhibits tensile shift in
dislocation dominated regime which is in agreement with experiments
Li et al. 2008. In GBS regime we observed intergranular strain
vanishes due to fall in flow stress whereas experiments Cheng et
al. 2009 show vanishing intergranular strain even in a mixed
regime. Using our studies we show that the intergranular strain can
be used to determine the underlying deformation mechanism including
the presence of partial dislocation activity in nc-materials.
Further using statistical average we quantified the deformation
mechanism by measuring the lattice strain so that a better
comparison between theoretical determination and experimental
observations of deformation mechanisms can be made.
Advisors/Committee Members: Bower, Allan (Director), Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (Reader),
Kumar, Sharvan (Reader).
Subjects/Keywords: nanocrystalline
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Chinthapenta, V. R. (2012). Theoretical Modeling of Lattice Strain Partitioning in
Nanocrystalline FCC Metals. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:297639/
Chicago Manual of Style (16th Edition):
Chinthapenta, Viswanath R. “Theoretical Modeling of Lattice Strain Partitioning in
Nanocrystalline FCC Metals.” 2012. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:297639/.
MLA Handbook (7th Edition):
Chinthapenta, Viswanath R. “Theoretical Modeling of Lattice Strain Partitioning in
Nanocrystalline FCC Metals.” 2012. Web. 20 Apr 2021.
Vancouver:
Chinthapenta VR. Theoretical Modeling of Lattice Strain Partitioning in
Nanocrystalline FCC Metals. [Internet] [Doctoral dissertation]. Brown University; 2012. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:297639/.
Council of Science Editors:
Chinthapenta VR. Theoretical Modeling of Lattice Strain Partitioning in
Nanocrystalline FCC Metals. [Doctoral Dissertation]. Brown University; 2012. Available from: https://repository.library.brown.edu/studio/item/bdr:297639/
10.
Haft Baradaran, Hamed.
Modeling Diffusion, Deformation and Fracture in Thin Film
Electrodes.
Degree: PhD, Solid Mechanics, 2013, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:320551/
► It is well known that diffusion induced stresses are responsible for capacity fading of electrodes in lithium-ion batteries. Here, we develop an atomistic-based continuum model…
(more)
▼ It is well known that diffusion induced stresses are
responsible for capacity fading of electrodes in lithium-ion
batteries. Here, we develop an atomistic-based continuum model for
atomic diffusion within solid electrodes, accounting for the effect
of the interplay between stress field, diffusivity and chemical
potential, effect of the solution binding energy, and the maximum
attainable stoichiometry. Our model is then validated using
molecular dynamics simulations of hydrogen diffusion in nickel. The
model is shown to give predictions in excellent agreement with
atomistic simulations. It is shown that the stress-diffusivity
coupling introduced here could give rise to a surface locking
instability under constant charging flux. This instability, which
happens only when the product of the electrode’s characteristic
size and charging current exceeds a critical value, replaces the
typical diffusion process and causes the inserted atoms to
accumulate within a boundary layer near the surface without
allowing them to get inside the electrode.
We will then particularly focus on the mechanical failure in
silicon (Si) thin film electrodes on metallic substrates. It is a
common observation that emergence of a variety of mechanical
failure modes is responsible for capacity loss in such electrodes
after only a few cycles. Recently, it has been proposed that
patterning could provide a way to improve the mechanical stability
of thin film electrodes. In this study, we present a theoretical
study of fracture, interfacial delamination and fatigue in
patterned thin film electrodes, with reference to the available
experimental observations. It is shown that sliding at the
interface between the Si thin film and underlying metallic
substrate could explain why fracture spacing in continuous thin
films is orders of magnitude larger than the film thickness. Based
on the idea of interfacial sliding, it is also explained why
interfacial delamination of Si island electrodes manifests a size
effect about the size of the fracture spacing in a continuous film.
Moreover, it is shown that variations in yield stress and/or
interfacial shear resistance during lithium cycling could
potentially activate a ratcheting failure mode in Si islands,
leading to incremental accumulation of deformation.
Advisors/Committee Members: Gao, Huajian (Director), Sheldon, Brian (Reader), Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (Reader).
Subjects/Keywords: lithium-ion batteries
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Haft Baradaran, H. (2013). Modeling Diffusion, Deformation and Fracture in Thin Film
Electrodes. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:320551/
Chicago Manual of Style (16th Edition):
Haft Baradaran, Hamed. “Modeling Diffusion, Deformation and Fracture in Thin Film
Electrodes.” 2013. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:320551/.
MLA Handbook (7th Edition):
Haft Baradaran, Hamed. “Modeling Diffusion, Deformation and Fracture in Thin Film
Electrodes.” 2013. Web. 20 Apr 2021.
Vancouver:
Haft Baradaran H. Modeling Diffusion, Deformation and Fracture in Thin Film
Electrodes. [Internet] [Doctoral dissertation]. Brown University; 2013. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:320551/.
Council of Science Editors:
Haft Baradaran H. Modeling Diffusion, Deformation and Fracture in Thin Film
Electrodes. [Doctoral Dissertation]. Brown University; 2013. Available from: https://repository.library.brown.edu/studio/item/bdr:320551/
11.
Ishii, Yohei.
Self-organized ripple formation during ion bombardment:
Relation to stress, viscous flow and defect kinetics.
Degree: PhD, Materials Science, 2013, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:320547/
► Self-organized pattern formation can be produced by low energy ion bombardment. A continuum theory explains the ion-induced surface morphology evolution in terms of a balance…
(more)
▼ Self-organized pattern formation can be produced by
low energy ion bombardment. A continuum theory explains the
ion-induced surface morphology evolution in terms of a balance
between roughening (by sputtering) and smoothing (by surface
transport). Although this approach accounts for many experimental
features, it does not provide good quantitative agreement with
observed ripple formation kinetics and structure. Additional
physical mechanisms such as the effect of ion-induced stress,
ion-enhanced viscous flow, mass redistribution due to ion impact
and Ehrlich-Schwoebel barriers to interlayer diffusion have been
proposed to extend the original model. To explore the effect of
ion-induced stress, we studied stress evolution in silicon during
ion bombardment and relaxation after the ion bombardment was
stopped. We developed a model to explain the stress evolution and
relaxation behavior in terms of stress generation by ion
implantation and relaxation by ion-enhanced viscous flow. By
comparing the model with experimental results, we determined that a
bimolecular annihilation process (annihilation of dangling bonds)
is the dominant process controlling the concentration of flow
defects during and after ion bombardment. This analysis also
enabled us to directly determine the dependence of the inverse
viscosity on the defect concentration. We applied this model to the
ripple formation theory to show that stress is not playing a
significant role in enhancing ripple growth in amorphous Si. We
also used a Kinetic Monte Carlo simulation of self-organized ripple
formation during sputtering. We incorporated multiple defect
production by each ion impingement and an Ehrlich-Schwoebel (ES)
barrier into the simulation. The results show that these effects
change the ion-induced surface evolution but not enough to explain
the discrepancy between the model and experiments. Therefore, in
this dissertation, we showed both theoretical and experimental
approaches to understanding self-organized ripple formation during
ion bombardment.
Advisors/Committee Members: Chason, Eric (Director), Paine, David (Reader), Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (Reader).
Subjects/Keywords: self-organized
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Ishii, Y. (2013). Self-organized ripple formation during ion bombardment:
Relation to stress, viscous flow and defect kinetics. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:320547/
Chicago Manual of Style (16th Edition):
Ishii, Yohei. “Self-organized ripple formation during ion bombardment:
Relation to stress, viscous flow and defect kinetics.” 2013. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:320547/.
MLA Handbook (7th Edition):
Ishii, Yohei. “Self-organized ripple formation during ion bombardment:
Relation to stress, viscous flow and defect kinetics.” 2013. Web. 20 Apr 2021.
Vancouver:
Ishii Y. Self-organized ripple formation during ion bombardment:
Relation to stress, viscous flow and defect kinetics. [Internet] [Doctoral dissertation]. Brown University; 2013. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:320547/.
Council of Science Editors:
Ishii Y. Self-organized ripple formation during ion bombardment:
Relation to stress, viscous flow and defect kinetics. [Doctoral Dissertation]. Brown University; 2013. Available from: https://repository.library.brown.edu/studio/item/bdr:320547/
12.
Yang, Yinxuan.
A Phenomenological Investigation of Metal-Metal Contacts at
the Nanoscale for RF MEMS Switch Applications.
Degree: PhD, Materials Science, 2015, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:419544/
► RF MEMS contact switches play a very important role in mobile devices due to their low insertion losses and high on-off ratios. Gold has been…
(more)
▼ RF MEMS contact switches play a very important role in
mobile devices due to their low insertion losses and high on-off
ratios. Gold has been used as the primary contact material for its
beneficial physical and electrical properties such as negligible
insulating oxide formation on the surface and very low resistance.
In general, however, the performance and the reliability of the
nano-size contacts in MEMS switches are very difficult to predict
because the contact resistance is a strong function of the contact
force, current and voltage, and surface chemistry (contamination).
In this study, we investigate the nature of electrical and
mechanical contact behaviors in nanoscale contacts. Atomic Force
Microscope was used to perform experiments systematically to
understand the behaviors of the contaminant layer on gold surfaces
using the voltage, the current, the contact force, and the
mechanical changes in the gold surface resulting from tip-substrate
currents and voltage. Particular attention is focused on the
hydrocarbon contamination on the gold surface and its interaction
with the probe under low bias and low force conditions. To address
and to model this hydrocarbon layer, we applied a uniform
self-assembled-monolayer on the surface of the gold-based sample
for comparison. In addition, similar study was conducted on
Au-AuNi_(2 phases) alloy to characterize its mechanical and
electrical properties. The role of oxide layer due to the added
nickel were discussed, and compared with the carbonaceous
layers.
Advisors/Committee Members: Kingon, Angus (Director), Chason, Eric (Reader), Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (Reader).
Subjects/Keywords: RF MEMS
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Yang, Y. (2015). A Phenomenological Investigation of Metal-Metal Contacts at
the Nanoscale for RF MEMS Switch Applications. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:419544/
Chicago Manual of Style (16th Edition):
Yang, Yinxuan. “A Phenomenological Investigation of Metal-Metal Contacts at
the Nanoscale for RF MEMS Switch Applications.” 2015. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:419544/.
MLA Handbook (7th Edition):
Yang, Yinxuan. “A Phenomenological Investigation of Metal-Metal Contacts at
the Nanoscale for RF MEMS Switch Applications.” 2015. Web. 20 Apr 2021.
Vancouver:
Yang Y. A Phenomenological Investigation of Metal-Metal Contacts at
the Nanoscale for RF MEMS Switch Applications. [Internet] [Doctoral dissertation]. Brown University; 2015. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:419544/.
Council of Science Editors:
Yang Y. A Phenomenological Investigation of Metal-Metal Contacts at
the Nanoscale for RF MEMS Switch Applications. [Doctoral Dissertation]. Brown University; 2015. Available from: https://repository.library.brown.edu/studio/item/bdr:419544/
13.
Toyjanova, Jennet.
The Effect of Confinement on Neutrophil Force
Generation.
Degree: PhD, Mechanics of Solids, 2015, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:419365/
► Generation of forces is essential for the migration of neutrophils to the sites of infection or injury. The mechanical properties and local confinement of the…
(more)
▼ Generation of forces is essential for the migration of
neutrophils to the sites of infection or injury. The mechanical
properties and local confinement of the surrounding
microenvironment play a significant role in regulating these
forces. However, it is challenging to decouple each of these
features experimentally without inherently changing the
microstructure of the cell environment. Presented here is an
experimental method that is used to isolate confinement and
substrate stiffness as single variables in the neutrophil
environment. Using a combination of fast iterative digital volume
correlation and traction force microscopy techniques, this
dissertation demonstrates that neutrophils induce finite
displacements on their surroundings. Furthermore, the findings show
that neutrophil-generated forces are highly affected by confinement
and stiffness of their microenvironment.
Advisors/Committee Members: Franck, Christian (Director), Bower, Allan (Reader), Hammer, Daniel (Reader), Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (Reader),
Reichner, Jonathan (Reader).
Subjects/Keywords: cell mechanics
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Toyjanova, J. (2015). The Effect of Confinement on Neutrophil Force
Generation. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:419365/
Chicago Manual of Style (16th Edition):
Toyjanova, Jennet. “The Effect of Confinement on Neutrophil Force
Generation.” 2015. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:419365/.
MLA Handbook (7th Edition):
Toyjanova, Jennet. “The Effect of Confinement on Neutrophil Force
Generation.” 2015. Web. 20 Apr 2021.
Vancouver:
Toyjanova J. The Effect of Confinement on Neutrophil Force
Generation. [Internet] [Doctoral dissertation]. Brown University; 2015. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:419365/.
Council of Science Editors:
Toyjanova J. The Effect of Confinement on Neutrophil Force
Generation. [Doctoral Dissertation]. Brown University; 2015. Available from: https://repository.library.brown.edu/studio/item/bdr:419365/
14.
chen, peng.
Microscale Modeling of Deformation Response of Advanced High
Strength Steels and Mechanical Behavior of Active Biopolymer
Networks.
Degree: PhD, Mechanics of Solids, 2013, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:386120/
► The nonlinear deformation response of two distinct materials was studied using finite element simulations. One is the hard Advanced High Strength Steels (AHSS) widely used…
(more)
▼ The nonlinear deformation response of two distinct
materials was studied using finite element simulations. One is the
hard Advanced High Strength Steels (AHSS) widely used in automobile
vehicles. Another is the soft active biopolymer networks in plant
and animal cells. For the hard AHSS, our proposed approach has
successfully modeled the deformation response of two types of AHSS:
fully martensitic steel and dual-phase steels. The measured flow
curves for the martensite micropillars in the size-independent
regime were used to determine material parameters in a
dislocation-density-based crystal plasticity model of individual
martensite blocks. The crystallographic orientation dependence of
the flow strength in the ferritic micropillars was predicted
successfully by a crystal plasticity model that accounts for the
non-Schmid behavior. Full 3D crystal plasticity simulations, with
material properties determined from micropillar compression tests,
were then used to predict the macroscopic uniaxial stress–strain
curves of the fully martensitic steel and dual-phase steels, which
were in excellent agreement with experimental measurements. For the
soft active biopolymer networks, we have studied the elastic
response of actin networks with both compliant and rigid crosslinks
by modeling molecular motors as force dipoles. Our finite element
simulations show that for compliant crosslinkers such as filamin A,
the network can be stiffened by two orders of magnitude while
stiffening achieved with incompliant linkers such as scruin is
significantly smaller, typically a factor of two, in excellent
agreement with recent experiments. We show that the differences
arise from the fact that the motors are able to stretch the
compliant crosslinks to the fullest possible extent, which in turn
causes to the deformation of the filaments. With increasing applied
strain, the filaments further deform leading to a stiffened elastic
response. When the crosslinks are incompliant, the contractile
forces due to motors do not alter the network morphology in a
significant manner and hence only small stiffening is
observed.
Advisors/Committee Members: Bower, Allan (Director), Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (Reader),
Kumar, Sharvan (Reader),
Hector, Louis (Reader).
Subjects/Keywords: Low-carbon martensite
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
chen, p. (2013). Microscale Modeling of Deformation Response of Advanced High
Strength Steels and Mechanical Behavior of Active Biopolymer
Networks. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:386120/
Chicago Manual of Style (16th Edition):
chen, peng. “Microscale Modeling of Deformation Response of Advanced High
Strength Steels and Mechanical Behavior of Active Biopolymer
Networks.” 2013. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:386120/.
MLA Handbook (7th Edition):
chen, peng. “Microscale Modeling of Deformation Response of Advanced High
Strength Steels and Mechanical Behavior of Active Biopolymer
Networks.” 2013. Web. 20 Apr 2021.
Vancouver:
chen p. Microscale Modeling of Deformation Response of Advanced High
Strength Steels and Mechanical Behavior of Active Biopolymer
Networks. [Internet] [Doctoral dissertation]. Brown University; 2013. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:386120/.
Council of Science Editors:
chen p. Microscale Modeling of Deformation Response of Advanced High
Strength Steels and Mechanical Behavior of Active Biopolymer
Networks. [Doctoral Dissertation]. Brown University; 2013. Available from: https://repository.library.brown.edu/studio/item/bdr:386120/
15.
Wu, Hsiao-Mei.
Collective Behavior at the Interface of Lithium-Ion
Batteries under Cyclic Lithiation.
Degree: PhD, Mechanics of Solids, 2014, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:386243/
► This thesis presents experimental measurements and modeling of multi-scale collective behaviors characteristics of hierarchical interfaces in lithium-ion batteries (LIBs) during cycling. Two interfacial mechanisms are…
(more)
▼ This thesis presents experimental measurements and
modeling of multi-scale collective behaviors characteristics of
hierarchical interfaces in lithium-ion batteries (LIBs) during
cycling. Two interfacial mechanisms are introduced: One is in-plane
sliding between lithiated electrodes (a-SiLix) and current
collectors (Cu). The other is normal contact between the internal
interfaces of pouch battery cells. To estimate the interfacial
properties at a-SiLix//Cu interfaces, a new apparatus, named
“Self-Adjusting Liquid Linnik Interferometer (SALLI)”, has been
invented to perform in situ whole field deformation measurements
with µm resolution in lateral direction and nm resolution in
out-of-plane direction. Our result clearly demonstrates Li
segregation at the interface initially which leads to 200 µm
shrinkage of the Si film in the first cycle due to relaxation of
residual tensile stress. A mechanical model system, plate bending
distribution sensor (PBDS), which incorporates substrate bending
and interfacial sliding in its calibration has been developed. By
bridging the deformation estimated from PBDS and that measured from
the SALLI experiment, the interfacial properties are extracted
quantitatively. The critical energy release rate is estimated as
0.075 J/m2 and 0.34 J/m2 for the receding and growing shear crack
fronts respectively. A remarkable discovery is that the interfacial
shear strength of the actively segregating lithium at the interface
is measured only 1.15 kPa. It is due electro-chemically active
lithium-ion segregation process that allows slip processes of
hopping through a series of meta-stable atomic configurations.
Finally, two sets of in situ experiments have been performed and a
mechanical model has been developed to explain the internal contact
mechanism and its relationship with interface bubble-gas evolution.
Through these techniques, the degradation mechanism of the pouch
cells are explained. It shows that applying 4–5 psi prestressed
pressure to the cell can better control the bubble-gas formation
and increase the electrode contact area. Therefore, the battery
life is efficiently elongated. It is hoped that the thesis work can
contribute to optimal design of battery cells and maximize cell
capacity and life of LIBs.
Advisors/Committee Members: Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (Director),
Guduru, Pradeep R. (Reader),
Sheldon, Brian W. (Reader).
Subjects/Keywords: lithium-ion battery
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wu, H. (2014). Collective Behavior at the Interface of Lithium-Ion
Batteries under Cyclic Lithiation. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:386243/
Chicago Manual of Style (16th Edition):
Wu, Hsiao-Mei. “Collective Behavior at the Interface of Lithium-Ion
Batteries under Cyclic Lithiation.” 2014. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:386243/.
MLA Handbook (7th Edition):
Wu, Hsiao-Mei. “Collective Behavior at the Interface of Lithium-Ion
Batteries under Cyclic Lithiation.” 2014. Web. 20 Apr 2021.
Vancouver:
Wu H. Collective Behavior at the Interface of Lithium-Ion
Batteries under Cyclic Lithiation. [Internet] [Doctoral dissertation]. Brown University; 2014. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:386243/.
Council of Science Editors:
Wu H. Collective Behavior at the Interface of Lithium-Ion
Batteries under Cyclic Lithiation. [Doctoral Dissertation]. Brown University; 2014. Available from: https://repository.library.brown.edu/studio/item/bdr:386243/
16.
Li, Qunyang.
Micromechanics of pseudo-single-asperity friction: effects
of nanometer-scale roughness.
Degree: PhD, Division of Engineering. Mechanics of
Solids, 2008, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:252/
► Nanometer-scale roughness on a solid surface has significant effects on friction, since inter-surface forces operate predominantly within a nanometer-scale gap distance in frictional contact. This…
(more)
▼ Nanometer-scale roughness on a solid surface has
significant effects on friction, since inter-surface forces operate
predominantly within a nanometer-scale gap distance in frictional
contact. This thesis presents two novel atomic force microscope
friction experiments, each using a gold surface sliding against a
flat mica surface as the representative friction system. A
diamagnetic lateral force calibrator (D-LFC) was invented to enable
the accurate quantitative force measurements. In one of the
experiment, a disk-shaped single nano-asperity of gold was used to
measure the molecular level frictional behavior. The adhesive
friction stress was measured to be 264 MPa and the molecular
friction factor 0.0108 for a direct gold-mica contact in 30% humid
air. The capillary force from the condensed water meniscuses was
found to play an important role in magnifying the contact pressure
to plastically deform the nano-asperities leading to the dramatic
evolution of frictional responses. In the second experiment, the
frictional response of a micrometer-scale asperity with
nanometer-scale roughness exhibited a pseudo-single-asperity
frictional behavior. However, the apparent friction stress, 40.5
MPa, fell well below the Hurtado-
Kim model prediction for a
smooth-single-asperity friction, exhibiting an apparent size-scale
dependence of the friction stress. An interfacial roughness (IR)
layer model was then developed to investigate the effects of
roughness on pseudo-single-asperity friction. The model calculation
shows that the nanometer-scale surface roughness is the major
mechanism that explains the apparent size-scale dependence of the
friction observed in the experiments. Furthermore, the analysis
shows that the apparent friction stress as well as the apparent
pressure-dependent fiction factor relies on the surface roughness.
Both experimental and theoretical results suggest that the
evolution status of surface roughness is one of the important
internal variables for the macroscopic friction laws.
Advisors/Committee Members: Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (director),
Guduru, Pradeep (reader),
Gao, Huajian (reader).
Subjects/Keywords: micromechanics of friction
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Li, Q. (2008). Micromechanics of pseudo-single-asperity friction: effects
of nanometer-scale roughness. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:252/
Chicago Manual of Style (16th Edition):
Li, Qunyang. “Micromechanics of pseudo-single-asperity friction: effects
of nanometer-scale roughness.” 2008. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:252/.
MLA Handbook (7th Edition):
Li, Qunyang. “Micromechanics of pseudo-single-asperity friction: effects
of nanometer-scale roughness.” 2008. Web. 20 Apr 2021.
Vancouver:
Li Q. Micromechanics of pseudo-single-asperity friction: effects
of nanometer-scale roughness. [Internet] [Doctoral dissertation]. Brown University; 2008. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:252/.
Council of Science Editors:
Li Q. Micromechanics of pseudo-single-asperity friction: effects
of nanometer-scale roughness. [Doctoral Dissertation]. Brown University; 2008. Available from: https://repository.library.brown.edu/studio/item/bdr:252/
17.
Xia, Shuman.
Micromechanics of solid-surface contact suspension and its
role in friction.
Degree: PhD, Division of Engineering. Mechanics of
Solids, 2008, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:305/
► Solid-surface contact suspension is governed by asperity contact strength and multi-frequency surface roughness. Both of these two aspects are examined in this thesis for tribological…
(more)
▼ Solid-surface contact suspension is governed by
asperity contact strength and multi-frequency surface roughness.
Both of these two aspects are examined in this thesis for
tribological application of the solid-surface suspension technique.
The research is divided into three parts. Part I focuses on the
size-dependent contact strength of nano-asperities. Contact
strength of nano-asperities is proposed to be mainly governed by
heterogeneous dislocation nucleation due to the contact edge
singularity. The dislocation model predicts that a single crystal
gold pyramid with [114] facets has a contact strength scaling
exponent of -0.497, which is in good agreement with the existing MD
simulation result. In Part II, a novel hybrid method of
nanoindentation and finite element analysis is used to characterize
the silicon particle suspension resistance and the mechanical
properties of Al/Si interface in an aluminum matrix composite. The
suspension resistance is found to be strongly dependent on the
aspect ratio, up to 2, of the buried portion of cylindrically
shaped particles. The resistance comes from the plastic-flow
strength of the matrix and the slip strength of the interface. The
interface is found to be separated during unloading. An
element-size dependent FEM cohesive-zone law is used to extract the
interface properties; the results compare well with atomistic
calculations. The final part of this thesis is an experimental
study on micro-slip friction laws of rough surface contact with a
direct quantitative measurement of the interfacial slip zone using
electronic speckle pattern interferometry (ESPI). A slip precursor
displacement of about 3 microns is measured before the onset of
macro-slip of two contact PMMA surfaces with 1 micron RMS
roughness. An apparent penetration depth under normal pressure is
further observed with a contact stiffness of about 6
MPa/micron.
Advisors/Committee Members: Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (director),
Bower, Allan (reader),
Guduru, Pradeep (reader).
Subjects/Keywords: solid-surface contact suspension
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Xia, S. (2008). Micromechanics of solid-surface contact suspension and its
role in friction. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:305/
Chicago Manual of Style (16th Edition):
Xia, Shuman. “Micromechanics of solid-surface contact suspension and its
role in friction.” 2008. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:305/.
MLA Handbook (7th Edition):
Xia, Shuman. “Micromechanics of solid-surface contact suspension and its
role in friction.” 2008. Web. 20 Apr 2021.
Vancouver:
Xia S. Micromechanics of solid-surface contact suspension and its
role in friction. [Internet] [Doctoral dissertation]. Brown University; 2008. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:305/.
Council of Science Editors:
Xia S. Micromechanics of solid-surface contact suspension and its
role in friction. [Doctoral Dissertation]. Brown University; 2008. Available from: https://repository.library.brown.edu/studio/item/bdr:305/
18.
Burke, Brian C.
Experimental Analysis of Surface Deformations Caused By
Residual Stresses In Complex Solid Structures.
Degree: PhD, Division of Engineering. Mechanics of
Solids, 2008, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:60/
► Described here are a set of experiments whose aim is to correlate the residual stress in a complex solid structure to a measurement of surface…
(more)
▼ Described here are a set of experiments whose aim is
to correlate the residual stress in a complex solid structure to a
measurement of surface deformations resulting from an intervention
with the residual stress field residing in the solid. First, an
enhancement to the surface roughness evolution spectroscopy (SRES)
technique used for the measurement of residual stresses on the
scale of micrometers is presented. The enhancement incorporates the
effects of anisotropic elasticity into the measurement method.
Verification experiments were performed on a single crystal sample
to illustrate the effects of anisotropic elasticity on the measured
results. Next, a new method appropriate for parts on the length
scale of millimeters and up is described. The method, titled
partial polar decomposition (PPD), is formulated in terms of an
inverse problem and seeks to create an image of the residual
traction on a sectioned plane by using displacement measurements
resulting from a stress-relieving sectioning operation. A sample
experiment was performed to illustrate the practicality of the
method. Additionally, an enhancement to electronic speckle pattern
interferometry (ESPI) is proposed for large deformation
measurements using kinematic relations to correct partially
decorrelated interferograms. A two-dimensional rotation experiment
is executed to illustrate the effectiveness of the
method.
Advisors/Committee Members: Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (director),
Blume, Janet (reader),
Bower, Allan (reader).
Subjects/Keywords: roughness evolution
Record Details
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Burke, B. C. (2008). Experimental Analysis of Surface Deformations Caused By
Residual Stresses In Complex Solid Structures. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:60/
Chicago Manual of Style (16th Edition):
Burke, Brian C. “Experimental Analysis of Surface Deformations Caused By
Residual Stresses In Complex Solid Structures.” 2008. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:60/.
MLA Handbook (7th Edition):
Burke, Brian C. “Experimental Analysis of Surface Deformations Caused By
Residual Stresses In Complex Solid Structures.” 2008. Web. 20 Apr 2021.
Vancouver:
Burke BC. Experimental Analysis of Surface Deformations Caused By
Residual Stresses In Complex Solid Structures. [Internet] [Doctoral dissertation]. Brown University; 2008. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:60/.
Council of Science Editors:
Burke BC. Experimental Analysis of Surface Deformations Caused By
Residual Stresses In Complex Solid Structures. [Doctoral Dissertation]. Brown University; 2008. Available from: https://repository.library.brown.edu/studio/item/bdr:60/
19.
Ward, Donald K.
Atomistic Modeling of Deformation at the Nanoscale.
Degree: PhD, Division of Engineering. Mechanics of
Solids, 2008, Brown University
URL: https://repository.library.brown.edu/studio/item/bdr:88/
► Studies of two nanoscale systems with important engineering applications, Al-Si nanocomposites and Au nanoasperities, are investigated using molecular dynamics. The first system is studied in…
(more)
▼ Studies of two nanoscale systems with important
engineering applications, Al-Si nanocomposites and Au
nanoasperities, are investigated using molecular dynamics. The
first system is studied in order to investigate improvements to
nanocrystalline Al coating by introducing Si particles. In
composite systems, the role of bimaterial interfaces can dominate
material properties so the study begins with an examination of
tensile strengths and toughness for various Al/Si interfaces and
shows a general interface will have high strength and toughness.
The study then turns to Al-Si composites with three major results:
i) the deformation and fracture mechanisms are different in the
Al-Si composites relative to the all-Al materials with Al-Si
plasticity and failure predominately localized at Al/Si interfaces,
ii) the Al-Si nanocomposites have a higher yield stress than the
all-Al nanocrystals, consistent with recent experimental data, and
iii) with different failure modes, the tensile strengths of the
Al-Si and all-Al materials are similar with the Al-Si strengths
correalating well with the Al/Si interface strengths. These results
show that Al-Si interfaces control the mechanical behavior in the
nanocomposites and indicate that Al-Si nanocomposites can be
engineered for enhanced hardness over all-Al nanocrystals. Au
nanoasperities are perfect for studying the scaling of hardness at
a length scale which current models fail to predict. Large-scale
molecular dynamics model the compression of the smallest of surface
asperities or nanopyramids to predict the magnitude and scaling of
hardness, H, versus contact size. Three major results emerge: i)
regimes of near-power-law size scaling of the hardness exist, with
size-scaling exponent of -0.32 and -0.75 for MD and experiments
respectively; ii) unprecedented quantitative and qualitative
agreement between MD and experiments is achieved, with with MD
hardness ~4 GPa at a length of 36 nm and at experimental hardness
~2.5 GPa at 100 nm, and iii) an analytic model that incorporates
the energy costs of forming energetically favorable defect
structures to accommodate the deformation predicts the magnitude
and scaling of the hardness in good agreement with the MD. The
model predictions indicate a transition from a nucleation-dominated
regime to dislocation-interaction-dominated regime at larger sizes,
with a change in scaling exponent to ~-0.5-0.7. These results
provide a basic framework for predicting size-dependent plasticity
of realistic engineered surfaces.
Advisors/Committee Members: Curtin, William (director), Suk%22%29&pagesize-30">
Kim,
Kyung-
Suk (reader),
Kumar, Sharvan (reader).
Subjects/Keywords: atomistics
Record Details
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Ward, D. K. (2008). Atomistic Modeling of Deformation at the Nanoscale. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:88/
Chicago Manual of Style (16th Edition):
Ward, Donald K. “Atomistic Modeling of Deformation at the Nanoscale.” 2008. Doctoral Dissertation, Brown University. Accessed April 20, 2021.
https://repository.library.brown.edu/studio/item/bdr:88/.
MLA Handbook (7th Edition):
Ward, Donald K. “Atomistic Modeling of Deformation at the Nanoscale.” 2008. Web. 20 Apr 2021.
Vancouver:
Ward DK. Atomistic Modeling of Deformation at the Nanoscale. [Internet] [Doctoral dissertation]. Brown University; 2008. [cited 2021 Apr 20].
Available from: https://repository.library.brown.edu/studio/item/bdr:88/.
Council of Science Editors:
Ward DK. Atomistic Modeling of Deformation at the Nanoscale. [Doctoral Dissertation]. Brown University; 2008. Available from: https://repository.library.brown.edu/studio/item/bdr:88/
.