This thesis studies the in-hand manipulation problem of repositioning finger contacts on an object by controlled sliding. In this thesis we investigate two versions of the problem. First for a multifingered hand with circle patch contacts, we present a framework for planning the motion of the hand to create an...
Stringent demands in the sheet forming industry related to rapid and customized part realization coupled with rigorous requirements on geometric accuracy and product properties have outpaced the capabilities of traditional forming processes. As an emerging novel technology, Double-Sided Incremental Forming (DSIF) offers much higher flexibility with the complete elimination of...
Demands in the aerospace, automotive and biomedical sectors for low-volume sheet metal parts made from materials with high specific strength are growing due to the needs imposed by rapid product development cycles, and personalized products to mention a few. However, high strength-to-weight ratio materials, such as Ti6Al4V, are usually difficult...
Segregation of granular materials with different particle properties (e.g.,~size and density) is a ubiquitous phenomenon in nature and industry. In this thesis, different segregation mechanisms are studied in steady granular heap flows. Flow kinematics and segregation in transient granular flows are also explored. ', '\t', 'First, this thesis studies segregation...
Research on rat whiskers offers knowledge in neuroscience analogous to humans\' sense of touch and inspiration for efficient sensing robotics. The present work investigates the rat whisker system from a mechanical engineering perspective. First, key quasi-static and dynamic properties were quantified in Chapter 2 for individual whiskers in an array,...
Harbor seal whiskers exhibit a tapering elliptical geometry uniquely suited to detect wakes (trails of water produced by upstream bodies) in ways a regular, tapering, or elliptical cylinder cannot. Previous studies into the matter have relied on idealized representations of the geometry the whiskers seem to take on and have...
Hybrid polymer-peptide conjugates are receiving increasing attention as a promising class of biomaterials. Polymer conjugated coiled-coil peptides are a new addition to these designer macromolecules. Even though a variety of experiments and computational simulations have shown stabilization of helices upon polymer conjugation, there are still many questions regarding the conformations...
The aim of this dissertation is to make sense of nearly a century and a half's worth of observations concerning skin based electroadhesion phenomena. While this is a noble goal in and of itself, further motivation of this work is drawn from fact that the electroadhesive effect is increasingly being...
Greater interest in self-directed professions, like entrepreneurship, have led to a growth in informal workplace communities and social technologies that support new ways of working. However, we have little understanding of how these socio-technical environments support opportunities for professional skill development. The goal of this dissertation is to understand how...
Mechanisms for sensing fluid flow are well studied in arthropods and in some aquatic mammals, but we know very little about how terrestrial mammals detect and localize airflow (Chapter 1). In this thesis, I will describe a series of studies in rodents that investigate the behavioral, mechanical, and neural basis...
Most lubricants contain a series of additives that reduce friction and wear, and protect contacting surfaces. The design of these additives must be modernized to meet the challenges involved with high operating temperatures, extreme environmental conditions, and increasingly stringent environmental regulations. This research demonstrates three novel lubricant additive strategies that...
When granular materials with different properties (size, shape, density, etc.) flow, they tend to segregate. This research addresses a specific form of segregation (axial segregation) that occurs when size bidisperse granular mixtures flow inside a rotating cylindrical tumbler. Axial segregation is the formation of alternating bands of different particle species...
In this presented study, rolling in micro scale level, termed as microrolling, has been advanced and extended its application to surface texturing and roll bonding. Meanwhile, continuous direct current (DC) is introduced to the processes to establish two new microrolling processes: the Electrically-assisted Roll Bonding (EARB) and the Electrically-assisted Microrolling-based...
Intelligent behavior in humans is largely associated with encoding information to discrete symbols. However, symbolic behavior in robotic systems is not widespread, mainly due to lack of tools that constitute symbol-based automation implementable in real time. This thesis proposes real-time algorithms that facilitate and promote symbol-based action and sensing. In...
In recent times, there has been a transition away from traditional engineering materials to more advanced materials that are multi-functional and exhibit improved thermomechanical properties. Much of the inspiration for these advanced materials comes from natural biological systems that fulfill the needs of diverse organisms through clever material organization and...
Predictive modeling has emerged as a new research subject that studies a broad range of modeling techniques to provide confident prediction of the phenomenon of interest by integrating scientific principles together with both computer models and observed physical experiments. Motivated by overcoming the existing challenges, the objective in this dissertation...
This thesis contributes in two ways. First it describes a new framework for the systematic design of collective behaviors and solves a key stability issue under this design framework. In this thesis we apply this framework to solve three tasks in the swarm robotics field: connectivity maintenance, formation control and...
The goal of this dissertation was to elucidate the coalescence of vacancies in the cubic polytype of silicon carbide in a nuclear reactor relevant system. Large-scale empirical potential atomistic simulations were employed and the exploration of long time-scale behavior was performed through a new application of the parallel replica dynamics...
Micro/nanoscale friction behavior has drawn a great deal of attention because it can reveal friction behavior at the interface level and ultimately lead to the discovery of the origin or real mechanism of friction. Surface wettability is an important property of solid surfaces and has been widely used in fundamental...
This thesis deals with three problems encountered in micro- and nano-fluidics: linear stability analysis of electrokinetic mixing in icrochannels, development of a general purpose numerical technique for fully resolved simulation of electrohydrodynamic particulate flows, and studying the phenomenon of molecular scale slip next to boundaries in micro- and nano-channels.
Mixing...
In this thesis we study protein folding with external force. In Part I we simulate the folding or unfolding procedure based on the two-state model. For constant-velocity experiments, the simulation results fit the experimental results. For constant-force experiments, we introduce cooperativity between domains to explain the different behavior between single...
The need for low-cost robust meso-scale "smart" robots (manipulators) that have no discrete parts (monolithic), no sensors ("self-sensing") and can be used in space-constrained systems, e.g., in microfactories, biomedical applications, etc., was the motivation for the current research. This study describes the design, fabrication and analysis of such a smart...
A comprehension of the complex dynamics of gaseous combustion requires an understanding of the underlying fundamentals. In this dissertation, I examine planar diffusion flames from both an experimental and numerical perspective.
In the first part of this thesis, I study the extinction of unstrained, planar counter-diffusion flames. The theoretical model...
The "Z-width" of a haptic display is the dynamic range of impedances that can be passively rendered. Haptic displays with larger Z-width generally render more realistic feeling virtual environments. The maximum passive impedance a haptic display can render is directly related to the quantity of physical damping in the mechanism,...
The finite element method is used to investigate failure mechanisms in pin-hanger connections in aging highway bridges. Bridge pins and hangers are typically considered as critical elements whose failure may result in partial or entire collapse of the structure. The primary function of a pin-hanger connection is to allow for...
The rat whisker (vibrissal) system provides rats with an exquisitely acute tactile sense that has helped allow them to thrive all over the world. By actively rotating their whiskers back-and-forth ("whisking") against objects, rats can extract a rich variety of information including position, size, shape, orientation and texture. Today, however,...
In the last two decades the number of innovative applications for advanced materials has been rapidly increasing. Shape memory alloys (SMAs) are an exciting class of these materials which exhibit large reversible stresses and strains due to a thermoelastic phase transformation. SMAs have been employed in the biomedical field for...
Novel materials and nanostructures with superior electro-mechanical properties are emerging in the development of novel devices. Engineering application of these materials requires accurate electro-mechanical characterization, which in turn requires development of novel experimental techniques. This dissertation outlines the investigation of the mechanical and electrical properties of one-dimensional nanomaterials.
One-dimensional nanomaterials...
A dynamic model of the rolling process that includes the material strain-hardening and work roll flattening effects was developed based on homogeneous deformation theory. By coupling this new dynamic rolling process model with a structural model for a mill stand, a single-stand chatter model expressed through a state-space representation was...
A major challenge in the field of Structural Health Monitoring (SHM) of safety-critical structures is how to effectively and efficiently detect fatigue damage, especially before there is macrocrack initiation. In this dissertation, a local ultrasonic technique is developed to assess pre-crack fatigue damage in structures. The novel feature of this...
We present several multiscale quantum mechanical (QM), molecular mechanical (MM), and continuum mechanical (CM) schemes to study the strength properties of carbon nanotubes (CNTs) and graphene sheets. A bridging domain method based on overlapping domain-decomposition schemes using the Lagrange multipliers field is developed to couple an atomistic domain with a...
The addition of nanoparticles into polymer materials has been observed to dramatically change the mechanical, thermal, electrical, and diffusion properties of the host polymers, promising a novel class of polymer matrix composite materials with superior properties and added functionalities that are ideal candidates in many applications, including aerospace, automobile, medical...
In this research, the optical and electrical properties of graphene-based materials are investigated. In particular, "graphene oxide", which is an individual layer of graphite oxide, and its chemically reduced form, is probed in terms of its properties, and the properties of graphene oxide and chemically modified graphene oxide are compared...
Cells are known to respond to external stimuli such as chemical, physical and mechanical cues from their microenvironments. In this work, we developed the technology to to complement the previously reported studies that deal with substrates' mechanical property by developing thin polydimethlysiloxane (PDMS) membrane microdevices using microfabrication technology. Typically, multiples...
Various methods for solving the partial contact of surfaces with regularly periodic profiles-- which might arise in analyses of asperity level contact, serrated surfaces or even curved structures--have previously been employed for elastic materials. A new approach based upon the summation of evenly spaced Flamant's solution is presented here to...
In a highly competitive market, it is becoming increasingly important to view product design as an enterprise-level profit-driven activity. Demand models have become central to enterprise-driven design approaches since they help estimating the economic impact (e.g., revenues, profits, and cost) of a product's design. The primary contribution of this dissertation...
The macroscale mechanical and physical properties of materials are inherently linked to the underlying microstructure. Traditional continuum mechanics theories have focused on approximating the heterogeneous microstructure as a continuum, which is conducive to a partial differential equation mathematical description. Although this makes large scale simulation of material much more efficient...
There is a need for cyclic robots that interact with lower limbs. Such robots will bring new programmability to exercise, rehabilitation, psychophysiology, and physiology, allowing for complete customization of the foot pedal path and dynamics. These robots are novel to the robotics research ¯eld as well, since conventional robotic designs...
The combined trends of decreasing application size and increasing requirements for energy efficiency have driven a need for improved understanding and better predictive tools for thin film lubricated systems. Research on such systems is complicated by the involvement of both larger scale phenomena such as fluid flow, material deformation, and...
Motivated by applications to microfluidic separation systems like Capillary Electrophoresis (CE) and Capillary Electrochromatography (CEC), the research described in this dissertation analyzes through numerical and asymptotic methods the effect of variation in the wall zeta potential (or surface charge) on the electroosmotic flow field in a microchannel and the effect...
An understanding of how two people anticipate, adapt, and react to each other's forces and motions could aid in designing machines to work cooperatively with humans and further explain how a single human interacts with the world. Tasks, such as lifting and moving a bulky object, teaching manual skills, dancing,...
Spectral elements are p-type element which can provide better accuracy
and faster convergence. However, applications of these elements make
conformation to discontinuities in the function or its derivative
difficult. The eXtended Finite Element Method (XFEM) recently
developed at Northwestern University can easily treat the arbitrarily
aligned discontinuities, i.e. independent of...
Three critical problem areas pertinent to the development of precision high-speed spindles for meso-scale machine tools (mMTs), driven by air turbines, constitute the focus of this work. These are the development of the spindle, of a new tool clamping device, and of a measurement system for spindle error motions.
For...
Effective and reliable material and structure as bone implant have been a continuing challenge for scientists from bioengineering, material science and mechanical engineering. Porous titanium has reduced stiffness comparable to bone and open pores to allow complete bone infiltration, thus making it attractive for bone-replacement implants in biomedical engineering. To...
With the advances in electronics and communication devices over the last several decades, radio-frequency antennas have miniaturized from externally mounted “rabbit ears” on our grandma’s televisions to devices small enough to be concealed within the body of the cellphone itself, corresponding to the carrier frequencies used from on the order...
Tribological behaviors of lubricated interfaces are strongly affected by the interactions between mating surfaces and the rheological properties of the lubricant between them. This research aims to improve lubrication through two approaches: 1) designing surface textures for lubrication enhancement and adhesion reduction, and 2) developing lubricants of desired rheology.
Molecular...