الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
The ability of any system 10 perform its required function without failure remains a challenging concern for design engineers.
Fatigue is considered as the largest cause of failure in industrial components. Consequently, fatigue life can be satisfactorily considered as a measure that expresses reliability of mechanical components.
The need of a nondestructive tool able to predict the fatigue life, and hence, the reliability of components and structures is growing by time.
The objective of this thesis is to study the capability of modal testing, as a nondestructive test, to characterize the fatigue behavior of mechanical components. In this study, the microstructure characteristic, as a factor affecting fatigue life, is the main factor investigated in order to correlate modal parameters to microstructure changes. This is achieved by using ductile and grey cast iron, that differ in graphite shape and Austempered Ductile Iron (ADI) specimens treated al different conditions to obtain different microstructure.
The experiments are earned out into three sets to achieve the mentioned objective. First set is performed on ductile and grey cast iron specimens. The results show a good correlation between modal parameters and fatigue life.
Second set is performed on ADI specimens to correlate modal parameters to changes in microstructure measures (i.e. % Retained Austenite, Graphite count/mm2, and graphite size). Correlation between fatigue life and damping ratio is also investigated. Empirical formula to estimate the material damping in terms of microstructure measures
is established. Meanwhile, significant relation between fatigue life and damping ratio is
found.
Third sel of experiments aimed to monitor the decay in component’s life when subjected
to progressive fatigue by means of damping ratio.
This work illustrate that the damping ratio | shows the most noticeable response to
both microstructure changes, and fatigue life. An increase in damping ratio will improve
the fatigue behavior of mechanical components. Additionally, damping ratio as well as
fatigue behavior of ADI, are shown to be strongly dependent on the phases of
microstructure.