New model to predict the dynamic strain aging in Q235B steel

Dynamic strain aging (DSA) is a phenomenon influenced by both time and temperature, found in various metallic alloys such as steel, aluminum, nickel, titanium, and high entropy alloys. The main goal of this study is to develop a new constitutive model for Q235B steel that explicitly incorporates the effects of DSA within a Johnson-Cook type framework. The model is able to capture the coupled influence of strain rate and temperature on flow stress with high accuracy. The parameter identification procedure, based on differential evolution optimization, ensured a robust calibration against experimental data in a wide range of strain rates (0.001–7000 1/s) and temperatures (93–1173 K). The model was implemented in Abaqus/Explicit using the VUHARD subroutine, which calculates yield stress and its derivatives with respect to strain, strain rate, and temperature. The resulting model accurately reproduces the nonlinear strain rate sensitivity, the bell-shaped stress-temperature response characteristic of the DSA, and the shift of the peak DSA peak with increasing strain rate. The proposed model is therefore well suited for the implementation of finite elements and enhances predictive capability in simulations of structures subjected to dynamic loading and elevated temperatures.