A numerical ballistic performance investigation of Armox 500T steel through ductile damage models

In this work, the ballistic response of an armor steel, Armox 500T, is numerically investigated through finite element (FE) analysis by utilizing the Johnson-Cook (JC) and modified Mohr–Coulomb (MMC) damage models, with a focus on emphasizing the consequences of different modeling approaches. Although Lode-dependent failure models are considered to increase the accuracy of numerical predictions for ductile failure, there remains a complete lack of clarity as to whether all conditions and materials necessitate the adoption of such models for ballistic impact simulations. In this context, MMC and JC model parameters are calibrated through tensile test data available in the literature enabling direct comparison between them. Damage models are then validated using ballistic impact tests of Armox 500T performed with 7.62 API projectiles. The results indicate that the MMC model outperforms the JC model at predicting the failure modes while both models demonstrate strong performance in anticipating the residual velocity. The influence of projectile nose shape, target plate thickness, and impact angle are further investigated, and the effect of incorporating the Lode parameter is discussed in detail. Impact simulations with the blunt projectile nose shape is found to be highly sensitive to the effect of Lode angle on failure, with differences of up to 20% between models, while 7.62 API shows the lowest sensitivity. The difference between the models’ predictions is observed to increase at lower impact velocities and higher impact angles demonstrating the necessity of a Lode-dependent failure model for such cases. The JC model consistently yields smaller residual velocities compared to the MMC model in all cases indicating that the MMC is more conservative in terms of predicting protective performance of Armox 500T. •Johnson-Cook (JC) and modified Mohr–Coulomb (MMC) damage model parameters are calibrated for armor steel Armox 500T using a wide range of tensile tests.•Plasticity and damage models are validated through the ballistic impact test data.•The effect of Lode-dependent failure is studied for various configurations of ballistic impact with Armox 500T targets.•The difference between the two models is studied using different projectile nose shapes, target plate thickness, and impact angle.•At higher impact velocities, failure is dominated by strain rate effects reducing the influence of stress state.•Failure with blunt projectiles is found to be highly sensitiv