Granular aggregates of quartz subjected to triaxial compression under constant effective pressures (Pe) undergo macroscopic failure at critical stress states that depend on the effective mean stress. Although the mode of failure and mechanical response vary systematically with mean stress at failure, prefailure loading at subcritical stress states may induce yielding, and subcritical load paths may influence behavior at failure. Here, I investigate how the failure of quartz aggregates at conditions favoring compaction depends on consolidation history and load path in the transitional and ductile deformation regimes in terms of strain localization and microfracture fabric. Three distinct non-standard triaxial compression load paths were employed; the paths involve different preconsolidation of the aggregates at subcritical isotropic stress followed by differential loading with increasing or decreasing confining pressure. Deformed aggregates were injected with epoxy and studied using optical microscopy techniques to determine microscopic damage evolution for the different load paths. Microfracture data show that preconsolidation at subcritical isotropic loads facilitates formation of campaction bands during subsequent triaxial compression in the transitional regime. The preferred orientation of intragranular cracks evolves from near random fabrics for isotropic loading to strongly preferred orientations parallel to the maximum principal compression direction for differential loading, with the strongest preferred orientation within the compaction bands. Aside from the preconsolidation, different load paths have only a minor effect on the mechanical response during macroscopic failure.

Theory and experiment show that the rate and geographic distribution of erosion control the rate and pattern of deformation in collisional mountain belts. Enhanced erosion reduces the mass of material that must be moved up and over ramps and uplifted in large folds. In order to test this and related ideas in a natural example, we have compared modeled rainfall to measured thrust sheet displacement, geometry, and internal deformation in the Appalachian fold and thrust belt. We use mean annual precipitation from a global climate model (GCM) as a proxy for rate of erosion. Deformation measurements were made on a portfolio of regional cross sections from Alabama to New England. During the Carboniferous Allegheny orogeny the Southern Appalachians moved from -30 ° to 0° latitude whereas the Central and Northern Appalachians lay between -15° and 5° latitude. Mean annual precipitation determined from the GENESIS 2 GCM (Grossman, per. comm.) varied from tropical to arid conditions as the collision both moved north and grew in breadth and height. The Southern Appalachians, which experienced more net rainfall than other regions, generally show more displacement, deeper present day exhumation, and shallower ramps than regions to the north. The vicinity of the Pine Mountain thrust sheet in the Southern Appalachians experienced the most displacement (~1.5X the Central Appalachian average) and bulk shortening (~1.6X the Central Appalachians) and produced the most eroded material (~1.5X the Central Appalachians). The latitude of the Pine Mountain thrust sheet in the Southern Appalachians received ~20% more rainfall than the Central Appalachians. Although the number of regional detachments and lithologies change from Southern to Central and Northern Appalachians, the change in rainfall both regionally at any one time and as the collision progressed may explain part of the change in structural style from south to north.

The San Andreas Fault (SAF) near Parkfield, CA moves by a combination of aseismic creep and micro-earthquake slip. Measurements of in situ stress orientation, stress magnitude, and heat flow are incompatible with an average shear stress on the SAF greater than approximately 20 MPa. To investigate the micro-mechanical processes responsible for the low strength and creeping behavior, gouge samples from the 3 km-deep scientific borehole near Parkfield (the San Andreas Fault Observatory at Depth, SAFOD) are sheared in a triaxial rock deformation apparatus at conditions simulating those in situ, specifically a temperature of 100°C, effective normal stress of 100 MPa, pore fluid pressure of 25 MPa, and a Na-Ca-K pore fluid chemistry. The 2 mm-thick gouge layers are sheared to 4.25 mm at shear rates of 6.0, 0.6, 0.06, and 0.006 mu m/s. The mechanical data are corrected for apparatus effects and the strength of the jacketing material that isolates the sample from the confining fluid. Experiments indicate that gouge is extremely weak with a coefficient of friction of 0.14, and displays velocity and temperature strengthening behavior. The frictional behavior is consistent with the inferred in situ stress and aseismic creep observed at SAFOD. The low frictional strength likely reflects the presence of a natural fabric characterized by microscale folia containing smectite and serpentinite.

In motion planning, high clearance paths are favorable due to their increased visibility and reduction of collision risk such as the safety of problems involving: human- robot cooperation. One popular approach to solving motion planning problems is the Probabilistic Roadman Method (PRM), which generates a graph of the free space of an environment referred to as a roadmap. In this work we describe a new approach to making high clearance paths when using PRM The medial axis is useful for this since it represents the set of points with maximal clearance and is well defined in higher dimensions. However it can only be computed exactly in workspace. Our goal is to generate roadmaps with paths following the medial axis of an environment without explicitly computing the medial axis. One of the major steps of PRM is local planning: the planning of motion between two nearby nodes PRMs have been used to build roadmaps that have nodes on the medial axis but so far there has been no local planner method proposed for connecting these nodes on the medial axis. These types of high clearance motions are desirable and needed in many robotics applications. This work proposes Medial Axis Local Planner (MALP), a local planner which attempts to connect medial axis configurations via the medial axis. The recursive method takes a simple path between two medial axis configurations and attempts to deform the path to fit the medial axis. This deformation creates paths with high clearance and visibility properties. We have implemented this local planner and have tested it in 2D and 3D rigid body and 8D and 16D fixed base articulated linkage environments. We compare MALP with a straight-line local planner (SL), a typical local planer used in motion planning that interpolated along a line in the planning space. Our results indicate that MALP generated higher clearance paths than SL local planning. As a result, MALP found more connections and generated fewer connected components as compared to connecting the same nodes using SL connections. Using MALP connects noes on the medial axis, increasing the overall clearance of the roadmap generated.

Aluminum (1050) was deformed by plane strain compression (PSC) up to 75% reduction. The total deformation conditions include four temperatures (from 150oC to 300oC) and two strain rates (5¡Ñ10-2s-1 and 5¡Ñ10-4s-1). After the deformation, the specimens were examined by TEM for observing the morphology of the microstructures and measuring various parameters, which includes the sizes and aspect ratios of dislocation cells, as well as the distribution of misorientation angles for dislocation walls.

The liquid crystal displays itself has a lot of advantages, such as thin thickness, slight weight and high brightness, etc. It is an important target for many engineers to develop the high brightness, uniformity, low power consumption and thin backlight module. Due to the temperature raising of the cold cathode fluorescence lamp (CCFL) in a backlight module of a LCD under long-term lighting state, the micro-optic-structure will deform and cause an uneven luminance phenomenon. In this research, was provided a method of creating a model with thermal deformation and how to draw this model by using PRO/EINGINEER. Then, one can transform the model into the optical software, ASAP, to make optical analysis. Finally, the thermal module can be studied.

In this study, sharp/gradual converging-diverging microchannels with contraction/ expansion ratio of 4:1/1:4 was designed to generate elongational flow with uniform velocity in the centerline. The £f-DNA stained with YOYO-1 was observed in the flow. MPIV was built to measure the velocity distribution and local strain rate was estimated by MPIV measurements. The deformation and conformation of individual DNA molecules in the flow was visualized with confocal laser scanning microscopy (CLSM). The goal of the present work was to develop a method for stretching DNA molecules, in order to perform analysis of coil-stretch transition of DNA. By measuring dynamic properties and relaxation time of DNA molecules stretched by pressure driven at various flow rate and viscosity, we have shown how one could investigate the influence of hydrodynamic interactions in the case of stretching of DNA molecules.

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The energy absorbing behavior of stainless steel 304L during the pulsed Nd:YAG laser welding is investigated in this thesis. The equivalent absorptivity is estimated from the comparison of measured and finite element method (FEM) results simulated melting pool shape parameters, e.g. pool width, pool depth, cross-section area and total volume of the pool. To simulate the actual pulsed laser beam, the energy density of heating source is performed as a Guassian distribution in the transection of a circular laser beam. For evaluating the feasibility and the accuracy of the estimated equivalent absorptivity, the multi-pulsed Nd:YAG laser welding is simulated by using the estimated absorptivities. A good agreement between this simulated and measured melting pool shapes are found in the multi-pulsed laser welding. The equivalent absorptivity can be interpolated from different parameters of the molten pool. However, absorptivity curve fitted from the cross-section area and total volume of the melting pool provide a more stable value. Results also indicate that the absorptivity and the pulse energy are in inverse proportion. The thermal-elastic-plastic FEM model is employed to simulate the fusion and solidification process of the pulsed laser welding. A complicate residual stress distribution introduced from the shrinkage in the solidification process is also calculated and presented. The distribution of post-weld-deformation near the melting pool has also been studied in this thesis. This post-weld-deformation may be a key factor in high precision laser welding, e.g. laser packaging for the optoelectronic components. The absorptivity estimated in this thesis may be helpful to simulate the laser welding process accurately.

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