Effect of crack on natural frequency in rotor system

The first rotor-dynamic system have witness its failure due to vibration cause by various factors such as crack, unbalance of mass, poor quality of material, misalignment etc. As in many cases failure of system was due to presence of crack, detecting a crack before it occur or replacing the crack system with new system is helpful to avoid large scale destruction. In the present study effect of crack on natural frequency in a rotor shaft is analyzed. Crack of known depth and location have been developed in a shaft and analysis is carried out using Dynamic signal analyzer and then evaluating the Fast Fourier Transform (FFT) to analyze the system behavior in presence of crack. The effects of acceleration rate, various size of depth of crack and change of location of crack on vibration behavior of a dynamics system has been studied. By analyzing the spectrums of amplitude verses frequency for healthy and cracked shaft, it was identified that the change in spectrum behavior is due to the possible appearance of crack in shaft. Changes in frequency amplitude was studied and found that increase in amplitude of the synchronous frequency 1X and an appearance of its second multiple frequency 2X indicates the presence of crack in a shaft.