A Novel Method to Predict the Concentricity of Aero-Engine Rotor Considering the Assembly Process of Bolted Flange Joints

The concentricity of the aero-engine rotor is an important parameter to evaluate the quality of final assembly and directly affects the vibration characteristics, especially for high-speed rotation. The use of a bolted flange joint is the basic type of connection in aero-engine rotors. During the initial tightening of the bolts, large deformation usually occurs in the flange because its thickness is small. The deformation in the flange has a major impact on the concentricity and consequently the dynamic behavior of the aero-engine rotor. This paper proposes a novel stack-build assembly method to predict the concentricity of multi-stage rotors considering the deformation of the flange. The Small Displacement Torsor (SDT) method is employed to construct the mathematical model of part errors. The homogeneous coordinate transformation method is used to analyze the deviation propagation in the bolted flange joint of each stage part. A finite element (FE) model is built to obtain the deformation of the bolted flange joints by simulating the assembly process. The deformation of the flange is involved in the stack-build assembly model as an error matrix. Furthermore, the influence of the assembly process such as interference and preload, tightening sequence on the concentricity is investigated. The results show that bolted flange joints have a significant effect on concentricity, especially for the complex geometry at the flange interface. The developed approach is validated by experimental tests conducted on a multi-stage rotor. This study can provide guidance and enhance the dynamic performance of bolted joints for aero-engine rotors.