Theoretical modeling and tightening strategy analysis of single bolt and double bolts pre-tightening in the casing connection system

Bolted connections are widely used in the assembly of aeroengine casings, and the uniformity of residual pretension of bolts is considered one of the important criteria for evaluating the structural performance of bolted connections. This paper is based on the theory of elastic interaction between bolts, and constructs theoretical models of bolt group pre-tightening force for single bolt and double bolts pre-tightening during the pre-tightening process. This model can obtain the residual preload distribution of each bolt with known initial preload force, and re solve the initial preload force. During the analysis process, the influence of different pre-tightening sequences and pre-tightening steps on residual pre-tightening was analyzed. It was found that using specific pre-tightening sequences and increasing pre-tightening steps can effectively reduce the impact of elastic interaction on residual pre-tightening force of bolt groups. At the same time, the difference correction method is used instead of the reverse solution method to solve the initial pre-tightening force for the double bolts pre-tightening model, making the residual pre-tightening force of the bolt group more evenly distributed. In addition, this paper also conducted single step and multi-step bolt pre-tightening experiments and compared them with the theoretical model, fully proving the correctness of this model. The method of constructing the bolt pre-tightening theoretical model of the bolt group connection system in this paper can be widely applied to other aerospace bolted connection systems, effectively guiding the assembly process design, optimization, and improving the performance of the connection structure of actual aerospace engine casings in engineering.