Identification of material parameters at high strain rates using ballistic impact tests and inverse finite element analysis

Material models play a crucial role in finite element analysis, especially for evaluating deformations under high strain rates. This study introduces a straightforward method that combines experiments, numerical simulations, and optimization to identify the parameters of a ductile material model at high strain rates. We conduct ballistic impact tests using a single-stage light gas gun and spherical projectiles on Q235 steel at velocities ranging from 160 to 476 m/s to determine its properties. An iterative inverse finite element analysis helps to refine the Johnson-Cook material model constants, aligning them with the observed crater dimensions on the specimens caused by impacts at various speeds. The model's predictions for the crater profiles show a good match with the experimental findings across all tested velocities. Simulation outcomes reveal high strain values up to 3.81 and strain rates reaching 41 872 s(-1). Moreover, we assess the model's failure behavior under high strain rates through both perforation resistance tests and simulations on Q235 steel plates of varying thicknesses under ballistic impacts. The successful validation of the Johnson-Cook model for Q235 steel at these rates confirms the efficacy and reliability of our characterization method. This approach can be applied to develop model parameters for different materials under similar strain conditions.