Analytical Modelling of the Mechanical Behavior of Bolted Joint Subjected to Transverse Loading

Abstract

An analytical model for describing the mechanical behavior of a bolted joint subjected to a transverse load has been theoretically formulated. This paper focuses on the load-displacement relation. The transverse displacement is separated into five factors: (a) bolt bending due to a transverse force acting on the thread surface, (b) bolt bending due to the thread-surface reaction moment, (c) inclination of the bolt head, (d) thread surface slip, and (e) bearing surface slip. Contact force and slip displacement are newly modeled in order to describe (d) and (e). Contact surfaces are discretized into meshes. The contact force acting on each mesh is formulated by taking into account the helical profile of the thread. The slip criterion is judged according to the Coulomb friction law. In order to maintain a mechanical equilibrium, the contact force and contact state are calculated in a self-consistent manner. As for the interaction between the thread and bearing surfaces, torque induced on the thread surface is transmitted to the bearing surface in a model of bolt torsion, relevant to the loosening rotation. The mechanism by which the reaction moment, which affects (b) to (e), is induced on the thread and bearing surfaces is also investigated. We found that the inclination of the bolt affects the reaction moment during localized thread-surface slip, while the transverse displacement of the bolt affects that during the complete thread-surface slip. The reaction moment is formulated to be proportional to the stiffness of the thread and bearing surfaces. Finally, our analytical model is applied to an M16 bolted joint and confirmed that our model agree well with the FEM result.