Shaft crack detection during shut-down using continuous wavelet transform

Prabhakar Sathujoda,Alistair Dastgir

doi:10.21595/vp.2018.19864

Abstract

Shaft cracks in a rotor system may lead to destructive failure, if not detected at right time. The transient vibrations of a rotor system with a transverse breathing crack during rotor shut-down has been analyzed using Finite Element Method (FEM) for flexural vibrations. Since the vibration signals during shut-down are non-stationary, continuous wavelet transform (CWT) has been used to extract the crack feature when the rotor is decelerating through critical speed during shut-down. A parametric study for different crack depths has been studied for different decelerations and it is found that CWT can be effectively used to detect the crack during rotor shut-down.

Highlights

Unbalance in a rotor-bearing system induces bending fatigue loads on the shaft, which may cause cracking of the shaft during operation
Previous works [3,4,5] have been reported on the detection and monitoring of crack through transient vibration analysis while the rotor system is passing through the critical speed
Vibration analysis of rotor-bearing system during shut-down has been studied by using finite element method (FEM) for flexural vibrations to detect a shaft crack

Summary

Introduction

Unbalance in a rotor-bearing system induces bending fatigue loads on the shaft, which may cause cracking of the shaft during operation. Previous works [3,4,5] have been reported on the detection and monitoring of crack through transient vibration analysis while the rotor system is passing through the critical speed. Prabhakar et al [6], successfully used the wavelet transform to detect the shaft cracks while the rotor-bearing system passes through the critical speed during start-up. Sekhar [7] extended the use of wavelet transform to detect crack during startup and shut-down of the rotor system mounted on the fluid film bearings. Since the detection of shaft cracks using wavelet transforms when the rotor is decelerating through the critical speed are rarely found in literature especially when the rotor system is mounted on rolling element bearings, the present work has been considered to detect shaft crack during the rotor coast-down.

Crack modeling

Continuous wavelet transform

Results and discussion

Conclusions