+publisher:"Brown University" +contributor:("Kim, Kyung-Suk")

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)

Subjects/Keywords: high-temperature

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APA (6^th 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 (16^th Edition):

Grunschel, Stephen E. “Pressure-Shear Plate Impact Experiments on High-Purity Aluminum at Temperatures Approaching Melt.” 2009. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:73/.

MLA Handbook (7^th Edition):

Grunschel, Stephen E. “Pressure-Shear Plate Impact Experiments on High-Purity Aluminum at Temperatures Approaching Melt.” 2009. Web. 29 Mar 2020.

Vancouver:

Grunschel SE. Pressure-Shear Plate Impact Experiments on High-Purity Aluminum at Temperatures Approaching Melt. [Internet] [Doctoral dissertation]. Brown University; 2009. [cited 2020 Mar 29]. 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 (6^th 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 (16^th Edition):

Gerbig, Daniel Edward. “Measuring and Modeling the Behavior of High-Strength Steels.” 2016. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:674361/.

MLA Handbook (7^th Edition):

Gerbig, Daniel Edward. “Measuring and Modeling the Behavior of High-Strength Steels.” 2016. Web. 29 Mar 2020.

Vancouver:

Gerbig DE. Measuring and Modeling the Behavior of High-Strength Steels. [Internet] [Doctoral dissertation]. Brown University; 2016. [cited 2020 Mar 29]. 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 (6^th 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 (16^th Edition):

Waters, Julie F. “Contact mechanics of biologically-inspired interface geometries.” 2009. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:122/.

MLA Handbook (7^th Edition):

Waters, Julie F. “Contact mechanics of biologically-inspired interface geometries.” 2009. Web. 29 Mar 2020.

Vancouver:

Waters JF. Contact mechanics of biologically-inspired interface geometries. [Internet] [Doctoral dissertation]. Brown University; 2009. [cited 2020 Mar 29]. 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)

Subjects/Keywords: contacts

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APA (6^th 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 (16^th Edition):

Torres , Jahn Ramon. “Adhesion in Hydrogel Contacts.” 2015. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:419414/.

MLA Handbook (7^th Edition):

Torres , Jahn Ramon. “Adhesion in Hydrogel Contacts.” 2015. Web. 29 Mar 2020.

Vancouver:

Torres JR. Adhesion in Hydrogel Contacts. [Internet] [Doctoral dissertation]. Brown University; 2015. [cited 2020 Mar 29]. 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 (6^th 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 (16^th 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 March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:320465/.

MLA Handbook (7^th Edition):

Teller, Sean S. “High Frequency Viscoelasticity of Soft Materials at Low to Moderate Strains with Implications for Vocal Fold Tissue Engineering.” 2013. Web. 29 Mar 2020.

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 2020 Mar 29]. 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 (6^th 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 (16^th 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 March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:11181/.

MLA Handbook (7^th Edition):

Shi, Xinghua. “Theoretical and Molecular Dynamics Simulation Studies on the Mechanics of Carbon Nanomaterials-Based Nano/Bio-Systems.” 2011. Web. 29 Mar 2020.

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 2020 Mar 29]. 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 (6^th 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 (16^th Edition):

Zhao, Ruike. “A Mechanics Study on Surface Ruga Morphologies of Soft Materials.” 2016. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:674263/.

MLA Handbook (7^th Edition):

Zhao, Ruike. “A Mechanics Study on Surface Ruga Morphologies of Soft Materials.” 2016. Web. 29 Mar 2020.

Vancouver:

Zhao R. A Mechanics Study on Surface Ruga Morphologies of Soft Materials. [Internet] [Doctoral dissertation]. Brown University; 2016. [cited 2020 Mar 29]. 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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APA (6^th 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 (16^th Edition):

Wang, Chien-Kai. “Grain Boundary Field Projection Method and Atomic Lattice Interferometer for Nanometrology.” 2014. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:386259/.

MLA Handbook (7^th Edition):

Wang, Chien-Kai. “Grain Boundary Field Projection Method and Atomic Lattice Interferometer for Nanometrology.” 2014. Web. 29 Mar 2020.

Vancouver:

Wang C. Grain Boundary Field Projection Method and Atomic Lattice Interferometer for Nanometrology. [Internet] [Doctoral dissertation]. Brown University; 2014. [cited 2020 Mar 29]. 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)

Subjects/Keywords: nanocrystalline

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APA (6^th 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 (16^th Edition):

Chinthapenta, Viswanath R. “Theoretical Modeling of Lattice Strain Partitioning in Nanocrystalline FCC Metals.” 2012. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:297639/.

MLA Handbook (7^th Edition):

Chinthapenta, Viswanath R. “Theoretical Modeling of Lattice Strain Partitioning in Nanocrystalline FCC Metals.” 2012. Web. 29 Mar 2020.

Vancouver:

Chinthapenta VR. Theoretical Modeling of Lattice Strain Partitioning in Nanocrystalline FCC Metals. [Internet] [Doctoral dissertation]. Brown University; 2012. [cited 2020 Mar 29]. 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 (6^th 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 (16^th Edition):

Haft Baradaran, Hamed. “Modeling Diffusion, Deformation and Fracture in Thin Film Electrodes.” 2013. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:320551/.

MLA Handbook (7^th Edition):

Haft Baradaran, Hamed. “Modeling Diffusion, Deformation and Fracture in Thin Film Electrodes.” 2013. Web. 29 Mar 2020.

Vancouver:

Haft Baradaran H. Modeling Diffusion, Deformation and Fracture in Thin Film Electrodes. [Internet] [Doctoral dissertation]. Brown University; 2013. [cited 2020 Mar 29]. 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 (6^th 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 (16^th Edition):

Ishii, Yohei. “Self-organized ripple formation during ion bombardment: Relation to stress, viscous flow and defect kinetics.” 2013. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:320547/.

MLA Handbook (7^th Edition):

Ishii, Yohei. “Self-organized ripple formation during ion bombardment: Relation to stress, viscous flow and defect kinetics.” 2013. Web. 29 Mar 2020.

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 2020 Mar 29]. 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)

Subjects/Keywords: RF MEMS

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APA (6^th 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 (16^th Edition):

Yang, Yinxuan. “A Phenomenological Investigation of Metal-Metal Contacts at the Nanoscale for RF MEMS Switch Applications.” 2015. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:419544/.

MLA Handbook (7^th Edition):

Yang, Yinxuan. “A Phenomenological Investigation of Metal-Metal Contacts at the Nanoscale for RF MEMS Switch Applications.” 2015. Web. 29 Mar 2020.

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 2020 Mar 29]. 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)

Subjects/Keywords: cell mechanics

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APA (6^th 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 (16^th Edition):

Toyjanova, Jennet. “The Effect of Confinement on Neutrophil Force Generation.” 2015. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:419365/.

MLA Handbook (7^th Edition):

Toyjanova, Jennet. “The Effect of Confinement on Neutrophil Force Generation.” 2015. Web. 29 Mar 2020.

Vancouver:

Toyjanova J. The Effect of Confinement on Neutrophil Force Generation. [Internet] [Doctoral dissertation]. Brown University; 2015. [cited 2020 Mar 29]. 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 (6^th 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 (16^th 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 March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:386120/.

MLA Handbook (7^th Edition):

chen, peng. “Microscale Modeling of Deformation Response of Advanced High Strength Steels and Mechanical Behavior of Active Biopolymer Networks.” 2013. Web. 29 Mar 2020.

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 2020 Mar 29]. 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 (6^th 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 (16^th Edition):

Wu, Hsiao-Mei. “Collective Behavior at the Interface of Lithium-Ion Batteries under Cyclic Lithiation.” 2014. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:386243/.

MLA Handbook (7^th Edition):

Wu, Hsiao-Mei. “Collective Behavior at the Interface of Lithium-Ion Batteries under Cyclic Lithiation.” 2014. Web. 29 Mar 2020.

Vancouver:

Wu H. Collective Behavior at the Interface of Lithium-Ion Batteries under Cyclic Lithiation. [Internet] [Doctoral dissertation]. Brown University; 2014. [cited 2020 Mar 29]. 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 (6^th 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 (16^th Edition):

Li, Qunyang. “Micromechanics of pseudo-single-asperity friction: effects of nanometer-scale roughness.” 2008. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:252/.

MLA Handbook (7^th Edition):

Li, Qunyang. “Micromechanics of pseudo-single-asperity friction: effects of nanometer-scale roughness.” 2008. Web. 29 Mar 2020.

Vancouver:

Li Q. Micromechanics of pseudo-single-asperity friction: effects of nanometer-scale roughness. [Internet] [Doctoral dissertation]. Brown University; 2008. [cited 2020 Mar 29]. 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 (6^th 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 (16^th Edition):

Xia, Shuman. “Micromechanics of solid-surface contact suspension and its role in friction.” 2008. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:305/.

MLA Handbook (7^th Edition):

Xia, Shuman. “Micromechanics of solid-surface contact suspension and its role in friction.” 2008. Web. 29 Mar 2020.

Vancouver:

Xia S. Micromechanics of solid-surface contact suspension and its role in friction. [Internet] [Doctoral dissertation]. Brown University; 2008. [cited 2020 Mar 29]. 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)

Subjects/Keywords: roughness evolution

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APA (6^th 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 (16^th Edition):

Burke, Brian C. “Experimental Analysis of Surface Deformations Caused By Residual Stresses In Complex Solid Structures.” 2008. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:60/.

MLA Handbook (7^th Edition):

Burke, Brian C. “Experimental Analysis of Surface Deformations Caused By Residual Stresses In Complex Solid Structures.” 2008. Web. 29 Mar 2020.

Vancouver:

Burke BC. Experimental Analysis of Surface Deformations Caused By Residual Stresses In Complex Solid Structures. [Internet] [Doctoral dissertation]. Brown University; 2008. [cited 2020 Mar 29]. 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

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APA (6^th 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 (16^th Edition):

Ward, Donald K. “Atomistic Modeling of Deformation at the Nanoscale.” 2008. Doctoral Dissertation, Brown University. Accessed March 29, 2020. https://repository.library.brown.edu/studio/item/bdr:88/.

MLA Handbook (7^th Edition):

Ward, Donald K. “Atomistic Modeling of Deformation at the Nanoscale.” 2008. Web. 29 Mar 2020.

Vancouver:

Ward DK. Atomistic Modeling of Deformation at the Nanoscale. [Internet] [Doctoral dissertation]. Brown University; 2008. [cited 2020 Mar 29]. 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/

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