A two-node nonlinear connector for simulating simplified models of bolted joints under extreme loads

Abstract In industrial applications, fine-scale simulations of bolted joints are often impractical due to the numerous nonlinearities in the vicinity of the bolt, which result in computationally expensive calculations, particularly during the early design stages. To address this, engineers typically replace detailed bolt models with simplified models built from a connector library available in commercial finite element (FE) solvers. This paper presents a nonlinear FE connector model, along with an identification methodology, designed to capture the full behaviour of a bolted assembly. The model is driven by key design parameters, such as bolt preload, friction coefficients, or elastoplastic properties of the materials used. The connector formulation separates the various mechanisms that influence the macroscopic behaviour of bolted assemblies. Axial behaviour is modelled by accounting for the effects of preload and axial stiffness, while tangential behaviour incorporates friction between the assembled plates, under the bolt head or nut, as well as plasticity in the bolt and potential contact between the screw and bore in case of extreme loads. The parameters for this connector are identified using a generic overlap joint. The connector model is implemented through a user-defined element subroutine in Abaqus/Standard ™. Comparative analysis of quasi-static responses from fine-scale full 3D simulations and those using the proposed connector across different bolted assemblies shows close agreement, with a significant reduction in computational time.