Material modelling of tensile steel component under impulsive loading

Characterization and modelling of the material properties, as well as the fracture simulation needed for the numerical analysis of bolted T-stub connection under impulsive loads. The strain rate effects are considered on the material law; fracture simulation is explored following “element deletion” technique for a given level of ductile damage.

The T-stub model is used in Eurocode 3 – part 1.8 as part of the “component method” for the representation of steel connection’s tension zone and is usually responsible for providing ductility to the connection. Looking forward to establish the “T-stub’s” maximum displacement capacity under impact loading, i) fracture simulation of steel elements is here explored following “element deletion” technique for a given level of ductile damage; ii) material softening and triaxial stress state dependency are assessed by finite element analysis of common uniaxial tension tests, and iii) strain rates effects are used based on results from Split-Hopkinson Bar tests, through the incorporation of the Johnson-Cook’s elevated strain rate law for material strain-hardening description. Numerical predictions of the model describing the “T-stub” behaviour and displacement capacity are compared against experimental results.

The FE model developed was found reliable in the description of the T-stub response subject to static and impact loads. Particularly, the strain rate sensitive material hardening following a calibrated Johnson-Cook law proved accurate in the description of the enhancement of the material strength. It was observed that when subject to impact loading regimes, the force-displacement response of T-stubs is: i) enhanced due to elevated strain rate effects, avoiding rupture when subject to a load equal the maximum static; ii) less ductile plastic failure modes in deformable T-stubs are expected, whilst the development of higher strains in the bolt may lead to a reduction in its ductility capacity.

A non-linear dynamic FE model of simple T-stub configuration using a strain rate effect on the material law and fracture simulation, providing insight of stress, strain, strain rate and damage contours developments, when exposed to impact loading.