Browsing by Author "Dr. Denis Cormier, Committee Co-Chair"

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    Analysis of Non-Stochastic Lattice Structure Design for Heat Exchanger Applications
    (2009-12-07) Manogharan, Guha Prasanna; Dr. Ola Harrysson , Committee Chair; Dr. Denis Cormier, Committee Co-Chair; Dr. Stefan Seelecke, Committee Member
    MANOGHARAN, GUHA PRASANNA. Analysis of Non-Stochastic Lattice Structure Design for Heat Exchanger Applications. (Under the directions of Dr. Ola Harrysson and Dr. Denis Cormier.) Non-stochastic lattice structures are cellular solids with periodically repeating array of cells formed by interconnected struts. Conventional manufacturing limits cellular solid structures to stochastic foams and honeycombs. The recent advancement of Solid Freeform Fabrication (SFF) enables the manufacturing of spatially controlled non-stochastic cellular solids engineered for the requirements of a particular application. Recent developments led to the application of metal cellular solids for air heating applications. This research proposes to optimize the cellular solid structure design for efficient heat transfer with minimum fluidic pressure loss. The novel concept is to design cellular solids with thicker struts in the direction along the fluid flow and thinner struts perpendicular to the flow with appropriate current supply for optimum performance. The model analyzed has a resistive cellular solid at a fixed temperature. The geometries examined include hexagonal lattice and rhombic dodecahedron. The heat transfer can be enhanced by thicker struts in the core of the structures and subsequently, by increasing the current across the cells. With corresponding experimental validation, the analysis indicates that by varying the cell length at the entry and exit along the flow direction, pressure loss can be significantly reduced. The pressure loss can be minimized by thinner struts in the entry and exit of the cellular solid. The study indicates that there is no significant effect of the angle between the edges on the performance of the system in the length scale considered.
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    Development and Experimental Evaluation of a Novel Annuloplasty Ring with a Shape Memory Alloy Core
    (2009-04-27) Purser, Molly Ferris; Dr. Denis Cormier, Committee Co-Chair; Dr. Gregory Buckner, Committee Co-Chair; Dr. Ola Harrysson, Committee Member; Russell King, Committee Member
    A novel annuloplasty ring with a shape memory alloy core has been developed to facilitate minimally invasive mitral valve repair. In its activated (Austenitic) phase, this prototype ring provides comparable mechanical properties as commercial semi-rigid rings. In its pre-activated (Martensitic) phase, this ring is flexible enough to be introduced through an 8 mm trocar and easily manipulated with robotic instruments within the confines of a left atrial model. The core is constructed of 0.508 mm diameter NiTi, which is maintained below its Ms temperature (24 °C) during deployment and suturing. After suturing, the stiffener is heated above its Af temperature (37 °C, slightly below normal human body temperature) enabling the NiTi to retain its optimal geometry and stiffness characteristics indefinitely. The NiTi core is shape set in a furnace to the appropriate size and optimal geometry during fabrication. The ring is cooled in a saline bath prior to surgery, making it compliant and easy to manipulate. Evaluation of the ring included mechanical testing, robotic evaluation, static pressure testing, dynamic flow testing and fatigue testing. Experimental results suggest that the NiTi core ring could be a viable alternative to flexible bands in robot-assisted mitral valve repair.
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    Electron Beam Fabrication of Injection Mold Tooling with Conformal Cooling Channels
    (2005-04-29) Villalon, Ada Venus; Dr. Ola Harrysson, Committee Chair; Dr. Denis Cormier, Committee Co-Chair; Dr. Jeffery Joines, Committee Member
    Injection molding is the most common mass production process for plastic parts. All thermoplastics and some thermosets can be injection molded to achieve a wide variety of sizes and intricate shapes. Injection molded parts can be found everywhere, from electronics and power tools to appliances and automobiles. Due to the large impact that injection molding has on the manufacturing industry, companies constantly strive to shorten both cycle and product development time. Rapid Tooling is a manufacturing technique used to produce injection mold tools in a short period of time. A new process for manufacturing rapid tools is proposed. With the Electron Beam Melting (EBM) process the fabrication of fully dense, net shape tools is now feasible. Using the EBM process, certain features in the mold tool can be optimized such as the cooling system that is of critical importance in the part cycle time of a tool. A heat transfer simulation study was carried out to find the effect of conformal cooling channels in the heat dissipation within a mold. Extensive experimentation was performed to obtain valuable guidelines for the design of conformal cooling channels in injection molds manufactured via EBM technology.