Modeling of bolted connection characteristics and nonlinear response analysis of a rotor system under the effect of bolted connection and maneuver loads

Bolted connections have the advantages of simple structure, strong operability, convenient installation, and good connection rigidity, making them widely used in rotor connection structures of aircraft engines. This paper first thoroughly analyzes the transmission path of internal forces in bolted connection structures, calculates the stiffness of the connected parts, thread stiffness, bolt stiffness, and contact surface stiffness, and establishes an equivalent stiffness model for bolted connections. Then, considering the maneuver loads of horizontal yaw and the nonlinear Hertz contact force of rolling bearings, a dynamic model of the rotor system under the coupling effect of bolted connection and maneuver loads was proposed. Finally, the Newmark- β numerical method was used to solve the system response, and the effects of equivalent connection stiffness and maneuver loads of bolted connections on the overall system were studied. The research results indicate that: The equivalent stiffness of bolted connection reduces the overall stiffness of the shaft to a certain extent, and nonlinear response occurs near the critical speed. When the speed exceeds the critical speed, the system enters complex nonlinear motion. The system with equivalent stiffness of bolted connections enters twice the cycle later than the system without equivalent stiffness of bolted connections. As the equivalent stiffness of bolted connection increases, the nonlinearity of the system weakens. At the same time, it is accompanied by the following changes: the period doubling bifurcation point shifts backward. The critical speed of the system increases. The low-frequency component decreases and the frequency decreases. In the horizontal yaw maneuver flight state, the system generates rich nonlinear dynamic phenomena such as period doubling, quasi period, and chaotic motion near twice the critical speed. As the maneuver loads G increases, the main resonance speed increases, indicating that the presence of the maneuver loads increases the stiffness of the shaft. The vibration of the rotor significantly increases, which may cause friction between the rotor and stator in the horizontal direction. This paper provides a basis for predicting the nonlinear response of bolted rotor system under maneuver loads, in order to provide reference for efficient and accurate research on the dynamic characteristics of bolted structures.