Constitutive modelling and mechanical properties of a nitrogen alloyed steel

Abstract
The mechanical behaviour of a nitrogen alloyed steel has been investigated. Tensile tests have been done at nominal strain rates from 10^-3to 800 s^-1. The results are discussed in terms of material rnodelling and constitutive parameters for the Johnson and Cook model are proposed. At large strain rates the effect of adiabatic heating complicates the evaluation of the model constants. It is shown that significant errors in the predicted flow stress may occur if parameters determined under adiabatic conditions are used for isothermal deformation modes, or vice versa. The effect of temperature increase during the uniform part of the deformation is further discussed, and a simple finite element model for calculation of the temperature evolution with strain and strain rate is presented. The results are incorporated in the Johnson and Cook model, thus improving the agreement between model prediction and experimental data.