Modelling method for bending stiffness of bolted flange joint with spigot and analysis of rotor vibration characteristics

To meet the rapid iteration demands of the bolted rotor system for the next-generation aero-engine in the conceptual design phase, the bending stiffness model of the bolted joint is required to have the characteristics of high accuracy and easy solvability. A new analytical model of bending stiffness for bolted flange joint with spigot considering all parameters is established based on the theory of plates and shells, and the effects of preload and preload unevenness on the bending stiffness are analyzed. By performing a comparison study with the finite element contact model, the maximal calculation error of the bending stiffness is approximately 6.83%, and the time required to calculate the bending stiffness once is reduced from 7 min to 5e-5 s, the accuracy and efficiency of the proposed model are validated. After that, an equivalent method for characterizing bolted joint using virtual shaft segment is proposed, and a dynamic model of the bolted rotor system is developed, in which the proposed bending stiffness model is introduced. The influence of preload and preload unevenness on the vibration characteristics of the bolted rotor system is analyzed by combining numerical calculation and experimental investigation. The results show that increasing preload can narrow the non-synchronous response interval of the bolted rotor system and reduce the proportion of strain energy for the bolted joint, the amplitude of subcritical self-excited vibration decreases with the reduction of preload unevenness.