Browsing by Author "Tesfaye, Tamirat (PhD)"

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    Design of Cotton Spinning Machine for Middle Textile Industries
    (Addis Ababa University, 2014-10) Setegne, Chalachew; Tesfaye, Tamirat (PhD)
    Micro and Small Scale Enterprises (MSE’s) are widely implementing and developing in all sectors in Ethiopia. When we see one of the major sectors in which MSE’s are involved is in textile sector and when we observe the commonly used cotton spinning machines used by weavers organized in MSE’s and in home to home is made of wood. It only spines on one takeup shaft from a supply of cotton and consumes large amount of man-work hours to get so many spun yarn. But, cotton spinning is the main operation in the production of clothes by micro and small scale owners. Therefore, it is important to improve the spinning system that can be operated by small and middle scale industry level. Understanding this reality, this thesis focuses on designing cotton spinning machine. In this thesis, theoretical background and development of spinning is discussed; different characteristics of yarn are studied and spinning systems with their economic ranges are explained. On the product planning stage, different mechanisms and components are compared and selected properly. Based on the selection a spinning machine that can spin cotton in to yarn similar to hand spun yarn is designed. The machine will be operated by motor; spools are feed to the machine manually.
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    Dynamic Analysis and Improving Crashworthiness of Side-Impact Beam for Saloon type Vehicles
    (Addis Ababa University, 2017-06) Amare, Bililign; Tesfaye, Tamirat (PhD)
    Side impact collision of vehicle is one of the awfully hazardous crashes causing injuries and death annually around the word. In this paper, the most important parameters including material, geometry and rib arrangement were studied to improve the crashworthiness during vehicle-to-vehicle side collision. In the side impact, the side door impact structure is responsible to absorb the most possible kinetic energy. Different side impact structures are designed as alternative structure and are modeled with CAD software (CATIA V5) and then analyzed with FEM software (LS-DYNA with ANSYS R15). This research had taken the present geometry and material for side impact beam structure of Lifan-520 model as saloon car type. The side impact collision structure analysis accomplished for different materials to compare the weight and impact behavior. In this study, a side impact beam made of different materials and geometries were studied by impact modeling to determine the deflection, acceleration and energy-absorption behavior. The mentioned characteristics were compared to each other to find appropriate material and geometry. Finally, side impact beam with crossed rib arrangement (-type) and implication of Carbon/PEEK composite material having better specific internal energy absorption, more stable and acceptable deflection within a limited crumple zone are founded for improvement of crashworthiness. Key Words: Crashworthiness, Energy Absorption, Maximum Deflection, Acceleration, Composite Materials