Dynamic Compressive Behavior and Deformation-Failure Characteristics of a Medium-Carbon Cr-Ni-Mo High-Strength Steel

To investigate the dynamic compressive behavior and deformation characteristics of medium-carbon Cr-Ni-Mo high-strength steel under different strain rates and temperatures, quasi-static tensile and compression tests, together with Split Hopkinson Pressure Bar (SHPB) dynamic compression tests, were conducted. The Johnson-Cook flow stress and damage model parameters were calibrated based on the experimental results under the investigated loading conditions. Combined with macroscopic morphologies of recovered specimens, SEM fracture observations, and finite element simulations, the deformation and damage behavior of the material was investigated. The results show that the material exhibits pronounced strain-rate strengthening and thermal softening characteristics. At 298 K, increasing the strain rate from 1000 to 5000 s^-1 increases the mean maximum compressive stress from 2263.1 to 2500.9 MPa, while expanding the plastic deformation range. At 1000 s^-1, increasing the temperature from 298 to 698 K decreases the mean maximum compressive stress from 2263.1 to 1722.2 MPa. The calibrated Johnson-Cook model reasonably describes the stress response and deformation characteristics at different strain rates at 298 K, with relative errors of simulated maximum compressive stresses below 4% for the representative experimental curves used in the numerical comparison. The macroscopic and microscopic observations reveal that increasing strain rate promotes the localized shear deformation, inclined cracking, and partial fragmentation after plastic compression, with enhanced shear deformation features reflected by elongated dimples, fracture steps, and tear ridges. Increasing temperature reduces fragmentation under high strain-rate loading and promotes the formation of coarse dimples and plastic flow features. Numerical analysis further indicates that increasing strain rate promotes the localization of equivalent plastic strain, leading to inclined shear bands and crack formation.