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The advent of rapid manufacturing has enabled the realization of countless products that have heretofore been infeasible. From customized clear braces to jet fighter ducts and one-off dental implants, rapid manufacturing allows for increased design complexity and decreased manufacturing costs. The manufacturing capabilities of this process have evolved to the point that they have surpassed current design capabilities. Meso-scale lattice structures can now be built that contain more lattice struts than it is reasonable to efficiently define. This work has attempted to create a method for designing such lattice structures that is efficient enough to allow for the design of large or complex problems. The main hindrance to the design of complex meso-scale lattice problems is essentially the need to define the strut diameters. While it is obvious that a large design would contain more struts than can be specified by hand, designs also quickly surpass the current capabilities of computational optimization routines. To overcome this problem, a design method has been developed that uses a unit-cell library correlated to finite element analysis of the bounding geometry to tailor the structure to the anticipated loading conditions. The unit-cell library is a collection of base lattice primitives, or unit-cells, that have been specialized for certain applications. In this case, primitives have been created that perform best under the types of stress analyzed by finite element analysis. The effectiveness of this process has been demonstrated through several example problems. In all cases, the unit-cell library approach was able to create structures in less time than current methods. The resulting structures had structural performance slightly lower than similar models created through optimization methods, although the extent of this degradation was slight. The method developed in this work performs extremely well, and is able to create designs for even the most complex lattice structures. There is room for future development, however, in the streamlining of the design process and consideration of higher-order affects within unit-cells.

Solid-state amorphization of a crystalline solid to an amorphous phase is extensively studied as a first order phase transition at low temperature for almost thirty years. In this dissertation, we report the recent progress on phenomenological models employed for thermodynamic description of macroscopic systems and fluctuations and nucleation of mesoscopic inhomogeneous systems in binary solid solutions under polymorphic constraints with no long-range diffusion involved. Based on our understanding on atomic picture of solid-state amorphization in binary solid solutions, we propose a Landau free energy to describe amorphization as the first order phase transition. The order parameter is defined which represents the loss of long-range translational order. The elastic strain field induced by composition disorder plays the important role through the bilinear coupling with the order parameter. Elastic softening and amorphization happen simultaneously. From the similarity between the melting and amorphization, we use the temperature and composition as two external variables and treat solid-state amorphization as low temperature melting under polymorphic constraints. For homogeneous system, the phase diagrams for endothermic melting and exothermic melting are built separately and the corresponding thermodynamic quantities are presented. A microscopic homogeneous nucleation mechanism is proposed conceptually in binary solid solutions under polymorphic constraints. The formation of an amorphous embryo is initiated from the composition modulation in the crystal state and a subsequent polymorphous nucleation within the as-formed heterophase fluctuation. This homogeneous nucleation path is thought to be associated with the nonlinear energy localization mechanism connected with the localized large-amplitude excitations of atoms, which are induced by nonlinear and disorder. A Landau-Ginzburg free energy is constructed to describe the critical nucleus and the growth of the new phase in one-dimensional systems. Analytical and numerical methods contribute to the understanding the fluctuations and nucleation processes. Size-dependent melting and amorphization in nanosolids are investigated. Two models are proposed for nanocrystalline solid solutions to glass transformations. Based on the thin film model with finite thickness, we build one-dimensional Landau-Ginzburg approach, which includes surface contribution and size dependence, and numerical results do show similarity with experimentsâ results qualitatively.

Storage of granular solids in silos has been the practice for many years. Engineers have been faced with the problem of making the silos empty more efficiently and minimising the forces acting on the walls of the silo during material discharge. To this end the anti-dynamic tube was invented. The tube has a smaller diameter than the silo and consists of several portholes along its height and around its circumference. When the discharge gate of the silo is opened the granular material enters the tube through the portholes, flows down the inside of the tube and exits the silo through the discharge gate. Most tubes have been installed such that there was sufficient space between the base of the tube and silo bottom for the granular material to flow simultaneously through the discharge gate. The flowing material causes a down drag on the tube from the friction of the granular material on the walls of the tube. Previous research has underestimated the magnitude of these frictional forces resulting in catastrophic buckling failure of the tubes, blocking the discharge gate of the silo. A blockage of the discharge gate requires top emptying of the silo resulting in financial losses and down time of equipment. A steel model silo with an anti-dynamic tube was set up in the laboratory to measure the friction on the tube during material flow. From the results of these experiments, an equation has been derived to estimate the magnitude of the down-drag force. Furthermore, an empirical expression was developed for the effects of the speed of the flowing material on the magnitude of the down-drag force. To keep construction costs down, it is necessary to optimise the wall thickness of the tube. There is currently no theory for the buckling capacity of a thin walled cylindrical shell with multiple perforations around its height and circumference. Therefore additional experiments were undertaken on a cylindrical shell with multiple perforations subjected to a combination of an axial as well as an external lateral pressure. Following on from the experiments, finite element analyses were undertaken to compare with the experimental results. For each finite element analysis an out-of-roundness was introduced as an initial wall imperfection. From these analyses and the cylinder experiments, a method of producing interaction curves for tubes with varying ratios of open area has been developed.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Additional advisors: Richard Brown, Ioulia Karpechina, Ryoichi Kawai, Boris Kunin. Description based on contents viewed Feb. 5, 2008; title from title screen. Includes bibliographical references (p. 73-75).

Thesis (Ph.D.)--Northwestern University, 2002. / Includes bibliographical references (leaves 191-202).

Thesis (Ph.D.)--University of Western Australia, 2003.

Thesis (Ph.D.)--University of Melbourne, Center for Quantum Computing Technology,School of Physics, 2007. / Typescript. Includes bibliographical references (leaves 237-257).

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 189-198).

Thesis (M.S.)--Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.