Vibration Monitoring of Defective Shaft Bearing System

Abstract

AbstractThe most challenging task in a condition monitoring of a shaft bearing system is to identify a bearing fault and a shaft fault in presence of compound faults. In the present experimental study, the vibrations generated by the shaft rotor bearing system in presence of shaft crack(s) and bearing races fault(s) have been analyzed. Vibration signals of healthy and defective shaft bearing system have been captured using of National Instrumentation (NI) data acquisition module and LabVIEW software. The captured vibration signals were analyzed in time domain and frequency domain for the defect detection using MATLAB software. The critical speed of the shaft rotor system has been computed using Dunkerley’s equation and also verified experimentally. The presence of peaks at critical frequency (Fcr) and its harmonics, while shaft rotates in subcritical speed (1/3, 1/2) range, admit the presence of shaft crack. Moreover, the change in regular shape of orbit plots at the subcritical speed also identifies the cracked shafts. The wavelet transformation has been implemented to reduce the noise from the raw signal used for orbit plots. Six different shafts of 16 mm diameter having 0.2 mm wide and 4 mm or 6 mm depth open crack near to rotor or bearing end or cracks at both locations were used to study the effect of crack location and size on vibration amplitude and frequency. The maximum vibration amplitude has been noticed for the shaft having crack near to bearing end in presence of bearing defect.KeywordsVibration analysisFrequency analysisFault identificationWavelet transformation