Dynamic Constitutive Model for a Martensitic Precipitation-Hardening Steel Considering Adiabatic Shear Damage and Non-uniform Gradient Stress Change: Modeling and Applications

For the adiabatic shear behavior of metal materials at high strain rates, a compression test of the FV520B martensitic precipitation-hardened stainless steel was conducted in a wide range of strain rates (1.0 × 10 −3 s −1 -8 × 10 3 s −1 ), temperatures (20-800 °C), and hardness values (HRC32-HRC40). The effects of strain rate, temperature, and hardness on the plastic flow behavior of the materials and microstructural characteristics of the dynamic compression materials were analyzed. The mechanism of adiabatic shear damage (ASD) dissipation on the plastic flow stress (PFS) was revealed. The stress gradient change factor was proposed, and an analytical equation for the non-uniform gradient change in the PFS with respect to temperature and hardness was established. Therefore, based on the adiabatic shear microvoid evolution mechanism, strain equivalence principle, high-temperature softening effect, and hardness hardening effect, a novel dynamic constitutive model considering ASD and non-uniform gradient stress changes was established. The results showed that ASD caused a loss of PFS under high strain rate loading and even the phenomenon of strain rate inverse strengthening. ASD gradually became significant with the increase in hardness and disappeared when the temperature exceeded 600 °C. The PFS of the FV520B steel was characterized by a significant non-uniform gradient decrease with increasing temperature. The prediction error of the PFS in the dynamic constitutive model was reduced from 5-74.8 to 1.1-7.3%. The application of novel dynamic constitutive model in high-speed machining is further discussed.