Pierre-Alain Guidault

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.

Stranded cables, composed of multiple twisted wires, exhibit high tensile strength and flexibility, making them essential in numerous industrial applications, such as mooring lines for offshore structures, overhead conductors, and cable-stayed bridges. The complex interactions between individual wire strands - primarily fretting-induced frictional contact and fatigue - pose significant challenges for numerical modeling. In this context, point-wise contact interactions between wires of different layers are often critical. This study presents a new beam-to-beam small-sliding point-wise contact element tailored for modeling stranded cables under small relative sliding conditions. Unlike traditional contact formulations, the proposed approach eliminates the need for repetitive, computationally expensive contact searches by assuming small sliding amplitudes between beams, which allows for predefined node pairing. The method, implemented within a large rotation wireframe finite element framework, offers enhanced computational efficiency and maintains robustness through a smooth evolution of the contact normal, thanks to nodal cross-sectional rotations. Numerical examples demonstrate the model’s effectiveness in handling arbitrary small sliding cases.

In this paper, we provide the quantification of the linear and non-linear elastic mechanical properties of graphene based upon the judicious combination of molecular mechanics simulation results and homogenization methods. We clarify the influence on computed results by the main model features, such as specimen size, chirality of microstructure, the effect of chosen boundary conditions (imposed displacement versus force) and the corresponding plane stress transformation. The proposed approach is capable of explaining the scatter of the results for computed stresses, energy and stiffness and provides the bounds on graphene elastic properties, which are quite important in modeling and simulation of the virtual experiments on graphene-based devices.

A bridging domain method for coupled atomistic–continuum models is proposed that enables to compare various coupling terms. The approach does not require the finite element mesh to match the lattice spacing of the atomic model. It is based on an overlapping domain decomposition method that makes use of Lagrange multipliers and weight functions in the coupling zone in order to distribute the energy between the two competing models. Two couplings are investigated. The L² coupling enforces the continuity of displacements between the two models directly. The H¹ coupling involves the definition of a strain measure. For this purpose, a moving least‐square interpolant of the atomic displacement is defined. The choice of the weight functions is studied. Patch tests and a graphene sheet with a crack are studied. It is shown that both continuous and discontinuous weight functions can be used with the H¹ coupling whereas the L² coupling requires continuous weight functions. For the examples developed herein, the L² coupling produces less error in the zone of interest. The flexibility of the H¹ coupling with constant weight function may be beneficial but the results may be affected depending on the topology of the bridging zone. Copyright © 2008 John Wiley & Sons, Ltd.