Veering and merging analysis of nonlinear resonance frequencies of an assembly bladed disk system

Abstract

This paper presents an investigation of the eigenvalues of veering and merging phenomena of a bladed disk system with contact features (an assembly bladed disk system). Of particular interest are the vibrational characteristics at rotational speed intervals at which the eigenvalue loci exhibit veering and merging phenomena. Furthermore, the current work attempts to investigate the interactions between the disk-dominated and blade-dominated families of modes in an assembly bladed disk system. In this regard, a representative model of an assembly bladed disk system is proposed, implementing an improved Euler-Bernoulli beam to model the rotating blade. The coupled equations of the bladed disk system are discretized using the modal functions which satisfy the eigenvalue problem. The change in modal properties of a blisk system with rotational speed is initially depicted to provide a reference for the analysis of a nonlinear system. Thereafter, the modal spectrum of the assembly bladed disk system is computed and analyzed by a frequency-domain method. Numerical analysis reveals that coupling interaction induces a series of eigenvalue veering and merging phenomena and that the modal frequencies at low rotational speeds are significantly affected by the nonlinearity of contact features. In particular, corresponding analysis of the mechanisms of these phenomena is presented. Furthermore, the present work also investigates the sensitivity of a low rotational speed interval and merging phenomena to several parameters.