http://yetl.yabesh.ir/yetl1/handle/yetl/4255482 2026-05-02T17:49:11Z http://yetl.yabesh.ir/yetl1/handle/yetl/4310506 A Framework to Integrate Performance of Helmet Systems for Blast Overpressure, Blunt Impact, and Thermal Loading Khine, Yu Yu; Tan, X. Gary; Bagchi, Amit; Mott, David R. Helmets have evolved through improvements in shell and suspension materials, and better designs that can absorb ballistic and blunt impact energy. In the past 20 years, threats to U.S. Warfighters have increased with the prevalence of buried improvised explosive devices simultaneously producing overpressure, blunt and ballistic impact effects, as well as thermal loading in extreme desert conditions. The literature to date does not show any research that integrates multiple types of loading in helmet system design and performance analysis. The scope of this paper is to integrate such loadings into a design framework that enables trade space analysis across multiple threats. Blunt impact and blast overpressure loadings are simulated using computational fluid dynamics (CFD) and structural mechanics approaches presented by the authors earlier. The thermal loading and its effects are modeled as forced convection due to ambient directional winds to assess each design's efficiency in facilitating evaporative cooling via perspiration and quantified by transport of moisture-laden air away from the head. Blast overpressure and blunt impact loadings, along with thermal loading, are used for multiple configurations of the helmet suspension system as representative cases. The results from the simulated cases are integrated within a framework combining the effects of the loadings to assess helmet system design. We consider two different configurations of helmet systems in this paper and present the results in detail. 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4310505 A Novel Methodology for Improving Understanding of the Multiplanar Kinematics of the Human Cervical Spine Coltoff, Emma C.; Hezrony, Benjamin S.; Marcet, Paul A.; Wilson, Jonathan L.; Brown, Philip J. The biomechanics of the spine are naturally multiplanar, but their experimental characterization remains primarily conducted in pure moment bending in anatomical planes: Flexion-Extension (FE) in the sagittal plane, Lateral Bending (LB) in the coronal plane, and Axial Rotation (AR) in the transverse plane. This leaves the biomechanical behavior between anatomical planes under-characterized. Computational tools for evaluating spinal implants and surgical treatments, like finite element models, are validated by comparison to experimental spinal loading. Thus, they are only able to represent spine behavior that is characterized through testing. A novel testing protocol was developed using a six-axis industrial robot to apply multiplanar experimental loading trajectories to characterize the spine's multiplanar behavior. One postmortem cervical spinal specimen was loaded in combined FE and LB bending about the craniocaudal axis, capturing its multidimensional stiffness behavior at several hundred unique joint kinematic “poses” throughout the spine's physiologic range of motion. The multiplanar trajectories are designed to enable parameterization of spinal stiffness behavior at each pose to the joint kinematic pathway taken to achieve the pose. Visualizing the multiplanar behavior of the spine also reveals spinal movement patterns that are not visible in planar bending alone. This method has elucidated that spinal stiffness under multiplanar loading cannot be inferred exclusively from behavior in planar loading, and that directionality of spinal loading has an impact on stiffness behavior. This information can be incorporated into finite element models and other tools for more robust predictions for spinal health. 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4310504 Quantifying Real-Time Dynamic Responses and Damage Mechanics of Human Tympanic Membranes Exposed to Blast Waves Oliveira Luiz, Jonathan; Alipanahi, Anahita; Rosowski, John J.; Furlong, Cosme; Cheng, Jeffrey Tao Understanding the tympanic membrane's (TM, or eardrum) response to high-intensity acoustical events, such as blasts, is crucial for preventing and treating blast-induced auditory injuries. Despite its importance, there remains a gap in methodologies and measurements of the TMs rapid dynamic responses to these events. This study investigates the behavior of human TMs exposed to blasts using a novel system that integrates high-speed quantitative imaging techniques with a custom shock tube (ST). High-speed three-dimensional-digital image correlation (DIC) and high-speed Schlieren imaging techniques are applied in synchronization with high-frequency pressure sensors to quantify generation and propagation of shock wave (SW) and its interaction with the TM during the tests. Additionally, digital microscopy and optical coherence tomography (OCT) are utilized to characterize the TM's morphology pre- and postblast exposure. The full-field high-speed dynamic responses of cadaveric human TMs and their fluid–solid interactions with different levels of blast overpressures are presented, and the rupture of the TMs is described in real-time. These measurements are employed to assess whether the TM behaves as a thin shell under exposure to high acoustical events. The findings from these studies enhance the comprehension of the TMs biomechanics and damage mechanics under harsh conditions, thereby advancing prevention and treatment strategies for blast-induced auditory damage. 2025-01-01T00:00:00Z http://yetl.yabesh.ir/yetl1/handle/yetl/4310503 Exploring the Connection Between Brain Strain and Cognitive Changes: A Protocol Study Menghani, Ritika Raj; Bardall, Clayton; Tanaka, Martin L.; Kraft, Reuben H. Given the rise of head injury in the youth, much focus has been directed toward predicting brain injury using simulation tools such as finite element analysis. Various brain strain measures are proposed as indicators of concussion. However, the clinical connection between brain strain and cognitive changes has not been fully established. In this study, we develop a framework to compare strains and other metrics obtained from finite element brain simulations with sideline cognitive testing results. We conducted a preliminary study for ten college football players. The players were equipped with custom fit mouthguards and were monitored for one season. A total of 2185 impacts were collected, and eight cognitive tests were conducted that were triggered when acceleration measurement exceed a threshold of 30Gs. Axonal injury metrics were examined while considering cognitive scores. This study represents a protocol investigation with preliminary findings, as it explores the correlation between brain strain metrics and cognitive deficits in a sample of ten football players over one season. 2025-01-01T00:00:00Z