Numerical and experimental study of the preload induced period-1 and chaotic vibration of a rotor system considering contact effects

Contact effects are one of the primary nonlinear sources of vibrations in the gas turbine rotor systems. Specifically, the nonlinear stiffness between the disk interface from the contact effects has an important influence on the vibration characteristics. In this study, a contact model that accounts for the elastoplastic deformation of asperity is established based on the contact theory. To improve the macroscopic contact model of the bolted structure, we integrate the tested morphology results and modified the skewed distribution function. Subsequently, a dynamic model of the rod fastened rotor-bearing system that incorporates the nonlinear oil film force is established. The influence of the preload on the vibration characteristics of the rotor bearing system is analyzed. The results demonstrate that the improved contact model accurately describes the distribution of asperities on rough surface. The contact effects weaken the rotor lateral stiffness to a certain extent. According to the numerical results and experimental results, it can be found that changes in preload significantly affects the occurrence conditions from periodic vibration to chaotic vibration, a higher preload is conducive to maintaining the stable period-1 motion state at high speed. Additionally, as the preload is decreased, the speed range with obvious periodic-doubling frequencies gradually increases and the amplitude of vibration response decreases. This work provides a practical guidance for the dynamic design and preload adjustment of gas turbine rod-fastened rotor considering contact effects.