Study of flow behavior of armor steel material at high temperatures and various strain rates: a phenomenological modeling approach

Abstract The mechanical behaviour of Rolled Homogeneous Armour (RHA) steel under varying strain rates and temperatures is critical for its application in defence and structural industries. This study develops a phenomenological constitutive model to characterize the flow characteristics of RHA steel over a strain rate range of 0.0001 s −1 to 0.1 s −1 and a temperature range of 25 °C to 500 °C. The research is divided into two primary domains: experimental analysis and finite element simulation. In the experimental phase, tensile tests were conducted under controlled conditions to establish distinct flow curves based on strain rate and temperature variations. The flow behaviour was captured using an exponential equation, with its coefficients determined as functions of strain rate and temperature. A key feature of the proposed model is its ability to accurately predict the stress-strain response across a wide range of loading conditions. Unlike conventional models, the proposed equation introduces fitting parameters explicitly defined in terms of strain rate and temperature ratios, ensuring both simplicity and adaptability. To validate the proposed constitutive model, a user-defined material subroutine (UMAT) was developed and integrated into a finite element framework. The simulation results demonstrated excellent agreement with experimental data, confirming the accuracy and robustness of the model. The proposed approach provides a computationally efficient tool for predicting the mechanical response of RHA steel, which can be beneficial for applications involving impact-resistant structures, armour design, and high-strain-rate material modelling.