Study on the influence of tightening sequence on the axial stiffness of bolted joints

To plan a tightening sequence that meets the structural axial stiffness requirements during the product design phase, this paper proposes a digital design method for assembly processes focused on bolted joints. Addressing the deficiencies in the existing research on the mechanism by which the contact stiffness of bolted structures is influenced by tightening sequence, this study constructs an axial stiffness calculation model for a single bolted joint based on stress distribution theory. Employing contact nonlinear finite element technology and the theory of elastic interaction, a finite element model for a group of bolted joints is established to investigate the relationship between bolt pre-tightening sequence, pre-tightening force level, and joint performance. The study reveals that, compared to other tightening sequences, the diagonal crisscross tightening sequence can increase the pre-tightening force to 96.05% of the designed pre-tightening force, thereby improving dynamic performance. The calculated values of equivalent pre-tightening force and static stiffness for rectangular jointed members extracted from the finite element model exhibit high consistency with those from the theoretical calculation model established in this paper. This research provides valuable theoretical and practical guidance for the optimal design and application of bolted joints in various engineering fields.