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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. [ABSTRACT FROM AUTHOR]

Bone fracture, formation and adaptation are related to mechanical strains in bone. Assessing bone stiffness and strain distribution under different loading conditions may help predict diseases and improve surgical results by determining the best conditions for long-term functioning of bone-implant systems. In this study, an experimentally wide range of loading conditions (56) was used to cover the directional range spanned by the hip joint force. Loads for different stance configurations were applied to composite femurs and assessed in a material testing machine. The experimental analysis provides a better understanding of the influence of the bone inclination angle in the frontal and sagittal planes on strain distribution and stiffness. The results show that the surface strain magnitude and stiffness vary significantly under different loading conditions. For the axial compression, maximal bending is observed at the mid-shaft, and bone stiffness is also maximal. The increased inclination leads to decreased stiffness and increased magnitude of maximum strain at the distal end of the femur. For comparative analysis of results, a three-dimensional, finite element model of the femur was used. To validate the finite element model, strain gauges and digital image correlation system were employed. During validation of the model, regression analysis indicated robust agreement between the measured and predicted strains, with high correlation coefficient and low root-mean-square error of the estimate. The results of stiffnesses obtained from multi-loading conditions experiments were qualitatively compared with results obtained from a finite element analysis of the validated model of femur with the same multi-loading conditions. When the obtained numerical results are qualitatively compared with experimental ones, similarities can be noted. The developed finite element model of femur may be used as a promising tool to estimate proximal femur strength and identify the best conditions for long-term functioning of the bone-implant system in future study. [ABSTRACT FROM AUTHOR]