Study of Vehicle Dynamics and Occupant Response in Side Impact Crash Tests
Side impact crash is a leading cause of fatalities on the roadways of the industrialized world. In the mid 1990's NHTSA implemented a new car assessment program testing the lateral crashworthiness of vehicles entering the market with a moving deformable barrier. Previous work has been done in an attempt to distill these tests into finite element simulations using specific vehicle test results; however there has not been a comprehensive study attempting to develop a model that includes a large number of tests to evaluate trends in vehicle kinematics and how they affect the occupants coupled with finite element simulations. To this end, a study of side NCAP tests was performed on all sedan cars based on the test results reported in the NHTSA Vehicle Crash Test Database since the introduction of the 2005 model year. This data was used to evaluate typical motion of the target vehicle during a regulatory crash test, and the corresponding occupant response. This sample consisted of new models entering the market and nameplates with major redesigns with a sample size of 72 vehicles. From these tests a series of velocity profiles were developed including time versus average velocity plots for vehicle center of gravity, door sill, driver's seat and driver door. These parameters have been shown to be important in occupant response and injury. There was significant variability in the response at several accelerometer locations. It was also found that rotation of the vehicle did not become significant until after 100 ms, after the maximum injury was predicted by the dummy. A parametric finite element analysis was performed using the both the USSID and ES-2re models to study the response of a restrained occupant during a typical crash test. These simulations showed that the velocity of the intruding door had a large effect on the thoracic injury predicted by the side impact dummy models. The full text of this paper may be found at: http://www-nrd.nhtsa.dot.gov/pdf/esv/esv21/09-0016.pdf For the covering abstract see ITRD E145407.
Detrimental thoracoabdominal interaction with lateral airbag restraints
DETRIMENTAL THORACOABDOMINAL INTERACTION WITH LATERAL AIRBAG RESTRAINTS Jason John Hallman Marquette University, 2010 Side impact motor vehicle crashes pose unique challenges for occupant protection, particularly with regard to torso injury mitigation. The minimal cr ush distance between the vehicle exterior and the occupant torso has necessitated adva nced passive safety technologies in response to tightened regulatory requirements a nd increased public awareness of safety issues. In particular, lateral ai rbag restraints (side airbags) have undergone a rapid and unregulated introduction in recent years, wit h US availability increasing to over 90% of new vehicles in 2010. As with frontal airbag restraints, the propensity for injury to occupants in close proximity to side air bag deployment remains a concern. Test protocols have been proposed to evaluate occupant injury risk from airbag deployment with mechanical occupant surrogates. Ye t few studies have attempted to characterize thoracoabdominal responses to close-prox imity airbag contact in actual crashes, leaving unaddressed the relevance of test pr tocols and occupant surrogates currently employed. To address this issue, the present study sought to identify and characterize inj u y and biomechanical responses of the thoracoabdominal region to torso-interacting s ide airbag restraints. A novel biological experimental approach was developed fr m a multibody analysis and from an evaluation of documented restraint performance. Biomechanical responses of deflection, deflection rate, the Viscous Crite rion, and deformation obliquity with respect to subject anatomy were quantified. Further, t issuelevel material response was examined through a comparative finite element analysis of subject-specific loading. Results indicated that traumatic visceral inj ury specific to the posterolateral region was associated with close-proximity airbag inte raction. Deformation response was uniquely oblique with respect to anatomy, necessitati ng the refinement of existing injury metrics. Biomechanical tolerances were also determined for risk of trauma to posterolateral viscera. These results are useful for the de velopment of mechanical occupant surrogates and reductions to injury risks from close-proximi ty side airbag loading.
Design and Development of an In Vitro Tear Replenishment System
Understanding the cellular and molecular mechanisms of the corneal tissue and translating them into effective therapies requires organotypic culture systems that can better model the physiological conditions of the front of the eye. Human corneal in vitro models currently exist, however, the lack of tear replenishment limits corneal in vitro models’ ability to accurately simulate the physiological environment of the human cornea. The tear replenishment system (TRS), a micro-fluidic device, was developed to mimic the in vivo tear replenishment in the human eye in an in vitro corneal model. The TRS is capable of generating adjustable intermittent flow from 0.1 µL in every cycle. The TRS is a sterilizable device that is designed to fit standard 6-well cell culture plates. Experiments with the corneal models demonstrated that exposure to the TRS did not damage the integrity of the stratified cell culture. Contact lenses “worn” by the in vitro corneal model also remained moist at all times and the cytotoxicity of BAK could also be verified using this model. These in vitro results confirmed that the TRS presents novel avenues to assess lens-solution biocompatibility and drug delivery systems in a physiologically relevant milieu.