Characterization of the mechanical behaviour of Tempcore 500C rebar steel during tensile test necking: experimentation and simulation

The calculation of the true stress and strain values during the tensile test necking phase of smooth ductile metals specimens has been extensively pursued by several authors. A symmetrical neck profile, which leads to axial-symmetrical behaviour, is usually considered. In this study, the neck geometry of Temp-core ribbed bars, the most commonly used steel in reinforced concrete today, is analysed. Knowledge of the true stress and strain values up to failure of this steel is vital since these describe the real behaviour of the steel under extreme conditions. Due to the limited effectiveness of the previously reported theories, an experimental methodology is proposed in order to analyze ribbed bar neck 3D geometry. The results obtained are compared to those of smooth bars of similar steel, both of which are then validated through Finite Element analysis. As a result, the influence of ribbed geometry is found to involve a reduction of true strain values on failure, due to stress concentration occurring in proximity to the root of the transverse ribs affected by necking.