The Effect of Incorporating Lüders Plateau into a Plasticity Model in Predicting the Ballistic Impact Responses of 40CrNiMoA Steel Projectiles and Plates

Lüders plateau, a frequently observed phenomenon in uniaxial tensile tests of 40CrNiMoA high-strength steel, significantly influences material fracture behavior but is often neglected in characterizing metal plasticity and fracture properties. This study aims to develop a modified Johnson–Cook-2 (MJC-2) plasticity model incorporating Lüders plateau effects and evaluate its predictive capability for impact response. A series of mechanical tests were conducted and the plasticity model was calibrated through an experimental–numerical approach. Taylor impact and ballistic impact tests were conducted using a single-stage gas gun, with corresponding numerical simulations performed in finite element (FE) software. The results demonstrate that the MJC-2 model provides superior accuracy in predicting the fracture behavior of both targets and Taylor rods, as well as ballistic limit velocities (BLVs). Compared to models neglecting Lüders plateau, MJC-2 significantly enhances prediction precision.