The aim of this thesis is to investigate techniques and parameters that could be used tornidentify crack if it exist in a rotating disk. Many researches discovered formation orrnpropagation of a crack in a rotating disk will cause a catastrophic failure. Thus, healthrnmonitoring for a rotating disk due to crack using crack detection techniques will minimizernor reduce the failure that probably to occur.rnAmong few methods of detecting crack components and due to its feasibility of detectionrnof fatigue crack, vibration-based crack detection techniques are applied in this thesis. Thisrnmethod is based on the fact that change of physical properties (stiffness, mass andrndamping) due to crack that will manifest themselves as changes in component modalrnparameters (natural frequency, mode shape and modal damping). Thus, monitoring thernselected indicator derived from modal parameters helps to distinguish between crack or uncrackrnexistence and its state in the model.rnThis thesis demonstrates the change of the vibration characteristic of a rotating disk beforernand after it is exposed to crack. A mathematical modeling for a rotating disk with crack isrnderived using conservation of energy. That is, the energy gain of the rotating disk due torninertia load is analyzed by modeling the rotating disk as plate. And, the energy release duernto crack formation and propagation is added to the system to approximate thernmathematical simulation fully. Then, a numerical equation is derived for finite elementrnanalysis.rnA powerful finite element analysis software ANSYS is used to simulate the numericallyrnderived equations for the models and to find solutions. Besides, the geometric modelrnwhich simulate the real rotating disk without and with crack are modeled by commercialrnsoftware SOLIDWORK for its benefit of modeling complex geometry for the rotating diskrnwith different crack models.