A non-linear finite element connector model with friction and plasticity for the simulation of bolted assemblies

Accurate simulation of bolted joints is not always consistent with industrial requirements, since numerous nonlinearities in the vicinity of the bolt can lead to overly expensive calculations. For this reason, commercial finite element (FE) codes preferentially use substitutes for bolts, such as simplified models or connectors. In this paper, a nonlinear FE connector with its identification methodology is proposed to model the behavior of a bolted assembly. The connector model is based on practical design parameters, such as bolt preload, friction coefficients, or plastic material parameters. The connector is based on a separation of the different phenomena governing the macroscopic behavior of a bolted assembly. The axial behavior of the connector reflects the preload effect and the axial stiffness of the assembly, while the tangential behavior of the connector takes into account the friction phenomena that occur in the vicinity of the bolt. At the same time, a plastic behavior law with isotropic hardening for the bolt is proposed. The identification of the connector parameters is performed on a generic elementary one-bolt assembly. The connector is implemented in ABAQUS through a user-element subroutine. Comparisons of quasi-static responses between large-scale full 3D calculations and simulations with connectors on different bolted assemblies are provided. The results obtained are very similar, while observing a significant reduction in CPU time.