Mechanical Engineering

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    MINIMIZING THE ACOUSTIC COUPLING OF FLUID LOADED PLATES USING TOPOLOGY OPTIMIZATION
    (2009) Almitani, Khalid Haza; Baz, Amr M; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Optimization of the topology of a plate coupled with an acoustic cavity is investigated in an attempt to minimize the fluid-structure interactions at different structural frequencies. A mathematical model is developed to simulate such fluid-structure interactions based on the theory of finite elements. The model is integrated with a topology optimization approach which utilizes the Moving Asymptotes Method. The obtained results demonstrate the effectiveness of the proposed approach in simultaneously attenuating the structural vibration and the sound pressure inside the acoustic domain at several structural frequencies by proper redistribution of the plate material. Prototypes of plates with optimized topologies are manufactured at tested to validate the developed theoretical model. The performance characteristics of plates optimized for different frequency ranges are determined and compared with the theoretical predictions of the developed mathematical model. A close agreement is observed between theory and experiments. The presented topology optimization approach can be an invaluable tool in the design of a wide variety of critical structures which must operate quietly when subjected to fluid loading.
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    The Equilibrium Geometry Theory for Bone Fracture Healing
    (2008-04-29) Yew, Alvin Garwai; Hsieh, Adam H; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Models describing the impact of mechanical stimuli on bone fracture healing can be used to design improved fixation devices and optimize clinical treatment. Existing models however, are limited because they fail to consider the changing fracture callus morphology and probabilistic behavior of biological systems. To resolve these issues, the Equilibrium Geometry Theory (EGT) was conceptualized and when coupled with a mechanoregulation algorithm for differentiation, it provides a way to simulate cell processes at the fracture site. A three-dimensional, anisotropic random walk model with an adaptive finite element domain was developed for studying the entire course of fracture healing based on EGT fundamentals. Although a coarse cell dispersal lattice and finite element mesh were used for analyses, the computational platform provides exceptional latitude for visualizing the growth and remodeling of tissue. Preliminary parameter and sensitivity studies show that simulations can be fine-tuned for a wide variety of clinical and research applications.
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    Microbridge Formation for Low Resistance Interline Connection Using Pulsed Laser Techniques
    (2005-12-13) Chung, Kuan-Jung; Bernstein, Joseph B; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    MakeLink® technology has been applied in many semiconductor devices to achieve high performance. Sometimes one-type-link design doesn't make desirous links for all IC manufacturing processes. In this work, four new structures, called microbridge, were designed to form all types of link. Laser processing experiments were performed to verify the designs. The results show that two-lower-level-metal-line design has higher performance (low link resistance), higher productivity (broad energy window), and higher yield than the three-lower-level-metal-line design. Therefore, it can be considered as the optimal design from the processing point of view. Two-lower-level-metal-line with lateral gap structure provides better scalability and it can be used in next generation ICs. If high-speed is the primary concern, an advanced-lateral structure is best, corresponding to its much lower resistance. The reliability tests indicate that the median-times-to-failure of all test structures are greater than nine years in operating condition, presenting reasonable lifetimes for integrated circuits used in the market. A two-dimensional finite element plane models for microbridge formation is developed. Results are compared to the experiments with process windows to present their consistence. The model allowed for using different geometric parameters and metal-dielectric combinations optimizing the design. An optimal design diagram for the Al/SiO2 system is created to provide the designer with criteria to avoid the failure of structure. Trade-off requirements, such as process window and structure size, are also provided. Guidelines are obtained for the Cu/Low-K dielectric system.