Crack Detection in a Rotating Disk
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Date
2007-07
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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.
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Mechanical Engineering