Numerical study of the tensile behaviour of threaded steel fasteners at elevated rates of strain

The tensile behaviour of threaded steel fasteners is investigated numerically at elevated rates of strain using the finite element code LS-DYNA. A two-dimensional axisymmetric non-linear finite element model, adopting a thermoelastic–thermoviscoplastic constitutive model and a ductile fracture criterion, is used to predict the behaviour of the threaded steel fasteners. The material parameters are identified from inverse modelling using data from an experimental study previously published by the authors. The finite element model of the threaded assemblies, representing previously published tests, is used to predict the behaviour during loading at elevated rates of deformation, and, in particular, to determine the maximum load and the failure mode observed during testing. Based on the experimental parametric range the finite element model is capable of representing the experimentally observed failure modes and the measured load–deformation curves with good accuracy. The validated finite element model is also used to study how the behaviour of the assembly is affected by the test geometry, the grip length and the thermal softening. It is found that the threaded assembly represents with reasonable accuracy the behaviour of a real bolt–nut connection. Furthermore, it was found that the number of threads in the grip length could change the failure mode for the same loading rate and length of the thread engagement, and that thermal softening due to adiabatic heating seems to have no effect on the maximum load of the threaded rod assembly.