Concrete is a widely implemented material in simulation codes and understanding its response in different loading scenarios is of interest to researchers. Notably, concrete is an extremely versatile material for many different types of applications due to its ability to withstand high compressive loading conditions at an affordable cost. For this reason, it is of a strong interest to many researchers. Specifically, understanding the response of the concrete materials in ballistic loading conditions is of importance for scenarios such as military and defense applications. Furthermore, computational models have been developed to simulate the response of contentious materials in these loading conditions. In our study, a computational finite element analysis is conducted to evaluate the response of the high strength concrete denoted as BBR9. The mechanical response of this concrete is captured using two constitutive material models denoted as the Concrete Damage and Plasticity Model 2 (CDPM2) and the Holmquist-Johnson-Cook (HJC) concrete model. In this study, the material parameters of these concrete models are calibrated using existing experimental data found in literature. Specifically, confined triaxial compression and uniaxial compressive experiments (for multiple strain rates) are used to determine the parameters which are implemented to define the response of the BBR9 concrete for each material model. These calibrated material models are implemented to conduct finite element simulations to capture the ballistic impact response of the BBR9 concrete. The finite element simulations are conducted using impact velocities ranging from 300m/s to 1300m/s to present a wide ranged assessment of the energy transfer between the projectile and the BBR9 concrete targets due to the impact. Additionally, for our study a BBR9 target thickness of 25.4mm and a simple spherical projectile is considered. A numerical assessment of the material models is presented by comparing the impact velocity against the residual velocity for each simulation point considered in this study. These results present an assessment of the concrete models and also provides a conceptual validation of their responses. The material models are also qualitatively compared through crater and scabbing diameter results of the targets. The CDPM2 model presents scabbing on the front and rear surfaces of the concrete target, while the HJC model shows cratering of the impact site. Additional experimental studies are warranted to assess the response of this concrete under ballistic loads. Further, future experimental studies can be used to validate these finite element constitutive material models in the appropriate referent of the ballistic impacts.
In this study, we employ a finite element analysis to determine brain injury risks resulting from impacts caused by a soccer ball to the player’s head at various ball inflations. The repetitive ball-head impacts in soccer are a cause for concern considering the literature showing neurodegeneration in soccer pressures. Standard soccer ball inflation pressurizations for a size 5 ball are in-between approximately 60kPa and 110kPa; the effect of these pressurizations on injury risks has not been widely studied. This finite element analysis implements previously validated finite element models of an adult 50th percentile human head and regulation size 5 soccer ball. The results of the simulations are evaluated using existing kinematic injury metrics (HIC15 and BrIC) and peak pressure, Von Mises stress, and maximum principal strain values throughout the brain. The results of our simulations show increasing HIC15, peak pressure, and peak maximum principal strain values for increased ball pressurizations. It is found that increasing the ball pressure increases the rate of energy transfer from the soccer ball to the head, which translates to higher injury metrics and brain stresses and strains. Additionally, the peak contact area between the soccer ball and the head is inversely proportional to the ball pressurizations. Increasing soccer ball inflation pressures can lead to increased brain injury risks due to soccer heading.
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