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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/1596

Authors: Haileleoul, Sahle
Advisors: Dr. Alem Bazezew
Copyright: Jul-2007
Date Added: 1-Nov-2008
Publisher: Addis Ababa University
Abstract: The aim of this thesis is to investigate techniques and parameters that could be used to identify crack if it exist in a rotating disk. Many researches discovered formation or propagation of a crack in a rotating disk will cause a catastrophic failure. Thus, health monitoring for a rotating disk due to crack using crack detection techniques will minimize or reduce the failure that probably to occur. Among few methods of detecting crack components and due to its feasibility of detection of fatigue crack, vibration-based crack detection techniques are applied in this thesis. This method is based on the fact that change of physical properties (stiffness, mass and damping) due to crack that will manifest themselves as changes in component modal parameters (natural frequency, mode shape and modal damping). Thus, monitoring the selected indicator derived from modal parameters helps to distinguish between crack or uncrack existence and its state in the model. This thesis demonstrates the change of the vibration characteristic of a rotating disk before and after it is exposed to crack. A mathematical modeling for a rotating disk with crack is derived using conservation of energy. That is, the energy gain of the rotating disk due to inertia load is analyzed by modeling the rotating disk as plate. And, the energy release due to crack formation and propagation is added to the system to approximate the mathematical simulation fully. Then, a numerical equation is derived for finite element analysis. A powerful finite element analysis software ANSYS is used to simulate the numerically derived equations for the models and to find solutions. Besides, the geometric model which simulate the real rotating disk without and with crack are modeled by commercial software SOLIDWORK for its benefit of modeling complex geometry for the rotating disk with different crack models The vibration characteristic and physical changes i.e. distribution of deformation and stress of the rotating disk is studied in relation to different crack orientation and a range of inertia loads for the system. As the result obtained, their relationship and output of the rotating disk without and with crack are discussed. And few recommendations are made for the future study.
Description: A thesis submitted to the School of Graduate Studies of Addis Ababa University in partial fulfillment of the requirement of the Degree of Masters of Science in Mechanical Engineering (Applied Mechanics Stream)
URI: http://hdl.handle.net/123456789/1596
Appears in:Thesis - Mechanical Engineering

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