Showing papers by "A. S. Sekhar published in 2003"

Identification of a Crack in a Rotor System using a Model-based Wavelet Approach

Abstract: The dynamics and diagnostics of a cracked rotor have been gaining importance in recent years. Vibration monitoring during start-up or shut-down is as important as during steady-state operations to detect cracks especially for machines such as aircraft engines which start and stop quite frequently and run at high speeds. In the present study, a model-based method is proposed for the on-line identification of cracks in a rotor while it is passing through its flexural critical speed. The fault-induced change of the rotor system is taken into account by equivalent loads in the mathematical model. The equivalent loads are virtual forces and moments acting on the linear undamaged system to generate a dynamic behaviour identical to the measured one of the damaged system. The rotor has been modelled using FEM, while the crack is considered through local flexibility change. The crack has been identified for its depth and location on the shaft for different rotor accelerations. The nature and symptoms of the fault ...

Dynamics of cracked composite shafts

Abstract: The dynamics of cracked rotors has been the study for the last three decades. However, considering the importance in the practical fields, the vibration characteristics of cracked rotors are still under active investigation. It needs more attention, particularly with the emerging of new materials such as composites for shafts. The present study aims at the analysis of the cracked composite shafts. The composite shaft has been modelled based on first order shear deformation theory using finite element method with shell elements. Different materials such as, boron-epoxy, carbon-epoxy and graphite-epoxy have been tried for various stacking sequences. The influences of crack parameters, fibre orientation (stacking sequences) and material properties on the vibration characteristics of composite shafts have been studied.