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...
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...
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...
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...
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...
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...
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...
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...
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 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...