Influence of Bolt Pretension on the Analytical Design of an Aeronautical Bolt under Shear Loading

Abstract

This work investigates the influence of bolt pretension on the analytical sizing of an aeronautical bolted joint subjected to transverse loading. The in-house MHBOLT method, used for preliminary design, predicts an earlier failure and a different failure mode from those observed experimentally. An experimental campaign and a three-dimensional non-linear finite-element model were used to investigate the origin of this discrepancy. The study highlights the role of the axial contact interfaces beneath the bolt head and the nut, whose resultants become eccentric as the transverse load increases. This eccentricity generates an additional bending-moment contribution that is not represented in the original analytical formulation. Based on these observations, two improvements to MHBOLT are proposed: a more realistic description of the radial contact-pressure distributions and an analytical correction based on a Winkler-type model. For the investigated configuration, these modifications significantly reduce the deviation from the numerical reference while retaining a formulation suitable for industrial preliminary sizing. Further parametric validation is nevertheless required before generalisation to the complete family of joints.