Numerical and experimental investigations on dynamic behaviors of a bolted joint rotor system with pedestal looseness

Abstract

Pedestal looseness is a common fault in rotating machines. To enhance the economy and convenience of the assembly of the aero-engine rotor system, the bolted joint structures are a useful tool for fastening multiple parts of different materials into an integrated system. To our knowledge, the time-varying bending stiffness and looseness fault at the pedestal significantly influence rotor dynamics. The present work aims to gain insight into the dynamic behaviors and mechanical behaviors of a rotor-bearing system with a bolted joint structure subjected to a pedestal looseness fault. Firstly, the dynamic model of a bolted joint rotor-bearing system supported by pedestals was set up taking into account the time-varying bending stiffness of bolted joint and the pedestal looseness fault. The feature of the pedestal looseness fault that occurs in a bolted joint rotor system was investigated by comparing the variation ranges of bending stiffness and dynamic responses. An experimental study was then performed using a rotor-bearing test rig equipped with a bolted joint and pedestals. Finally, dynamic phenomena such as offset of the equilibrium position of the vibration waveform, appearance of continuous frequency spectra, and irregular shaft orbits can be known as the dynamic features for the pedestal looseness fault.