Structural similitude for a scaled rotor system considering stiffness characteristics of bolted joints

Abstract

Rotor system with bolted joints is widely used in aero-engine, and has the features of large axial span, high-degrees of freedom, and nonlinearity. There exist several researches on similitude of rotor systems, but these studies mainly focus on the simple and linear systems. The similitude investigation for the rotor system considering bolted joints has not been conducted. To fill this gap, a method to obtain the scaling laws for low-pressure (LP) compressor are presented based on the generalized and fundamental equations of substructures (bolted joint, shaft, and disk), which considers the nonlinearity of bolted joints and different materials. The dynamic model of the LP compressor considering the nonlinearity produced by bolted joints is established. Moreover, the effect of bolted joints on the LP compressor is investigated to illustrate the necessity for considering bolted joints in similitude procedure. In order to ensure the similitude of nonlinear dynamic characteristics, the scaling factors are divided into the linear and nonlinear scaling factors, where the nonlinear scaling factors are used to put the bolted joint into similitude. The results show that the natural frequencies, vibration responses, frequency components, and stability can be predicted accurately by scaled models, even the models are made of relatively cheap materials.