Experimental Investigation of Vibration Analysis of Multi-Crack Rotor Shaft

Abstract

In recent years, the dynamic behaviour and diagnostic of cracked rotor have been gained momentum. In literature, several studies are available for cracked rotor systems, however very few authors have addressed the issue of multi-cracked rotor system. This paper deals with the nonlinear dynamic behaviour of multi cracked rotor system, which is analyzed experimentally and analytically with the considerations of the effects of the crack depth, crack location and the shaft's rotational speed. A new extension of Lagrangian method is used for analyzing the dynamic behaviour of a multi-cracked rotor system through Umbra Lagrangian formalism. The effects of crack depth on the shaft's stiffness and natural frequencies are analyzed experimentally. Natural frequencies have been obtained through vibration analyzer using impact hammer test under static conditions. This analysis also includes the dynamic response of rotor with breathing crack by using data acquisition system called OROS. It has been noticed that the stress concentration on the first crack has increased due to the presence of the second crack. Another interesting phenomenon is the influence of one crack over the other crack for mode shapes and for threshold speed limits. All such analysis has been carried out on experimental test rig consist of a symmetrical system, which has mild steel shaft between a pair of identical self-aligned double groove high speed bearings. The experimental results can be further validated with the analytical results.