Theoretical prediction modeling of residual pre-tightening force of bolt group of aerospace engine casing system considering gap and coaxiality deviation

Bolt connections are fundamentally important in aerospace engineering due to elastic interaction phenomena. However, bolt preload exhibits significant variations during assembly and service. Establishing a reliable theoretical model for predicting residual preload in bolt groups is therefore essential. Manufacturing-induced assembly deviations, particularly gap and coaxiality deviations, directly compromise preload formation and may lead to functional impairment. This study develops a comprehensive prediction model for residual preload during single-step and multi-step tightening of bolt groups. The model integrates gap and coaxiality deviations through spring-node modeling and elastic interaction theory, enabling prediction of residual preload distribution under arbitrary initial loads and tightening sequences. Validation through finite element analysis and experimental testing demonstrates excellent agreement with theoretical predictions. Further analysis systematically quantifies the substantial influence of clearance and coaxiality deviations on residual preload behavior. The model provides critical insights for optimizing bolted joint design in aerospace engine casing systems.