RESUMEN
Pedestrians are one of the most vulnerable road users. In 2019, the USA reported the highest number of pedestrian fatalities number in nearly three decades. To better protect pedestrians in car-to-pedestrian collisions (CPC), pedestrian biomechanics must be better investigated. The pre-impact conditions of CPCs vary significantly in terms of the characteristics of vehicles (e.g., front-end geometry, stiffness, etc.) and pedestrians (e.g., anthropometry, posture, etc.). The influence of pedestrian gait posture has not been well analyzed. The purpose of this study was to numerically investigate the changes in pedestrian kinematics and injuries across various gait postures in two different vehicle impacts. Five finite element (FE) human body models, that represent the 50th percentile male in gait cycle, were developed and used to perform CPC simulations with two generic vehicle FE models representing a low-profile vehicle and a high-profile vehicle. In the impacts with the high-profile vehicle, a sport utility vehicle, the pedestrian models usually slide above the bonnet leading edge and report shorter wrap around distances than in the impacts with a low-profile vehicle, a family car/sedan (FCR). The pedestrian postures influenced the postimpact rotation of the pedestrian and consequently, the impacted head region. Pedestrian posture also influenced the risk of injuries in the lower and upper extremities. Higher bone bending moments were observed in the stance phase posture compared to the swing phase. The findings of this study should be taken into consideration when examining pedestrian protection protocols. In addition, the results of this study can be used to improve the design of active safety systems used to protect pedestrians in collisions.
Asunto(s)
Vehículos a MotorRESUMEN
The pedestrian is one of the most vulnerable road users and comprises approximately 23% of the road crash-related fatalities in the world. To protect pedestrians during Car-to-Pedestrian Collisions (CPC), subsystem impact tests are used in regulations. These tests provide insight but cannot characterize the complex vehicle-pedestrian interaction. The main purpose of this study was to develop and validate a detailed pedestrian Finite Element (FE) model corresponding to a 50th percentile male to predict CPC induced injuries. The model geometry was reconstructed using a multi-modality protocol from medical images and exterior scan data corresponding to a mid-sized male volunteer. To investigate injury response, this model included internal organs, muscles and vessels. The lower extremity, shoulder and upper body of the model were validated against Post Mortem Human Surrogate (PMHS) test data in valgus bending, and lateral/anterior-lateral blunt impacts, respectively. The whole-body pedestrian model was validated in CPC simulations using a mid-sized sedan and simplified generic vehicles bucks and previously unpublished PMHS coronal knee angle data. In the component validations, the responses of the FE model were mostly within PMHS test corridors and in whole body validations the kinematic and injury responses predicted by the model showed similar trends to PMHS test data. Overall, the detailed model showed higher biofidelity, especially in the upper body regions, compared to a previously reported simplified pedestrian model, which recommends using it in future pedestrian automotive safety research.
Asunto(s)
Peatones , Accidentes de Tránsito , Fenómenos Biomecánicos , Análisis de Elementos Finitos , Humanos , Extremidad Inferior , MasculinoRESUMEN
Pedestrians are the most vulnerable road user and represent about 23% of the road traffic deaths in the world. A finite element (FE) model corresponding to a 5th percentile female pedestrian (F05-PS) was developed by morphing the Global Human Body Models Consortium (GHBMC) 50th percentile male pedestrian (M50-PS) model to the reconstructed geometry of a recruited small female subject. The material properties of the pedestrian model were assigned based on GHBMC M50-PS model. In model validation, the knee lateral stiffness and force time histories of F05-PS upper body showed similar trends, but softer responses than the corresponding data recorded in post mortem human surrogate (PMHS) tests and linearly scaled to average male anthropometry. Finally, the pedestrian model was verified in a Car-to-Pedestrian Collison (CPC) simulation. The marker trajectories recorded in simulation were close to the data recorded on small PMHS in testing and the model predicted typical knee ligament ruptures. Therefore, we believe the F05-PS model, the first FE model developed based on a female reconstructed geometry, could be used to improve vehicle front-end design for pedestrian protection and/or to investigate various pedestrian accidents.
Asunto(s)
Simulación por Computador , Análisis de Elementos Finitos , Peatones , Accidentes de Tránsito , Fenómenos Biomecánicos , Femenino , Cuerpo Humano , Humanos , Articulación de la Rodilla/fisiología , Vehículos a Motor , Factores de Tiempo , Adulto JovenRESUMEN
Objective: Finite element human body models (HBMs) must be certified for use within the EuroNCAP pedestrian safety assessment protocol. We demonstrate that the Global Human Body Model Consortium (GHBMC) simplified pedestrian series of HBMs meet all criteria set forth in Technical Bulletin (TB) 024 (v 1.1 Jan. 2019) for model certification. We further explore variation in head contact time (HIT) and location by HBM size and impact speed across 48 full body impact simulations.Methods: The EuroNCAP Pedestrian Protocol (v. 8.5, Oct. 2018) assesses the overall safety of adult and child pedestrians by outlining a variety of physical tests and finite element simulations using HBMs. These tests are designed to assess the efficacy of vehicle safety technology such as active bonnets. The 50th percentile male simplified pedestrian model (M50-PS, H:175 cm, W:74.5 kg), six-year-old (6YO-PS, H:117 cm, W:23.4 kg), 5th percentile female (F05-PS, H:150 cm, W:50.7 kg), and 95th percentile male (M95-PS, H:190 cm, W:102 kg) were simulated through the suite of cases totaling 48 simulations (12 each). The process gathers three kinematic trajectories and contact force data from designated anatomical locations. The impacting vehicles include a family car (FCR), multi-purpose vehicle (MPV), roadster (RDS), and sports utility vehicle (SUV), all provided by TU Graz, Vehicle Safety Institute as part of the Coherent Project, each simulated at 30 kph, 40 kph, and 50 kph. Each simulation underwent a 23-point pre-simulation check and post-simulation model response comparison. The posture of all HBMs met criteria consisting of 15 measures. All simulations were conducted in LS-Dyna R. 7.1.2.Results and Conclusions: All simulations normal terminated. For each of the simulations, sagittal plane coordinate histories of the center of the head, 12th thoracic vertebrae, and center of acetabulum were compared with standard corridors and did not exceed the tolerance of 50 mm deviation. Head contact time was also compared with the reference values and did not exceed the tolerance interval of +3.5% and -7%. Comparison of contact forces was required for monitoring purposes only. The head contact time of the models for each simulation was recorded and compared by model size, impact speed, and vehicle geometry. Head contact times varied by roughly 3-fold, were lowest for the child model, and showed the greatest sensitivity for the tallest stature model (M95-PS). As stated in the certification process, other body sizes within a model family qualify for certification if the 50th percentile male model passes, provided that model sizes meet the required posture.
Asunto(s)
Accidentes de Tránsito/prevención & control , Análisis de Elementos Finitos , Vehículos a Motor , Peatones , Seguridad , Adulto , Fenómenos Biomecánicos , Tamaño Corporal , Niño , Simulación por Computador , Europa (Continente) , Femenino , Cabeza/fisiología , Cuerpo Humano , Humanos , Masculino , Modelos Biológicos , PosturaRESUMEN
Pedestrians represent one of the most vulnerable road users and comprise nearly 22% the road crash-related fatalities in the world. Therefore, protection of pedestrians in car-to-pedestrian collisions (CPC) has recently generated increased attention with regulations involving three subsystem tests. The development of a finite element (FE) pedestrian model could provide a complementary component that characterizes the whole-body response of vehicle-pedestrian interactions and assesses the pedestrian injuries. The main goal of this study was to develop and to validate a simplified full body FE model corresponding to a 50th male pedestrian in standing posture (M50-PS). The FE model mesh and defined material properties are based on a 50th percentile male occupant model. The lower limb-pelvis and lumbar spine regions of the human model were validated against the postmortem human surrogate (PMHS) test data recorded in four-point lateral knee bending tests, pelvic\abdomen\shoulder\thoracic impact tests, and lumbar spine bending tests. Then, a pedestrian-to-vehicle impact simulation was performed using the whole pedestrian model, and the results were compared to corresponding PMHS tests. Overall, the simulation results showed that lower leg response is mostly within the boundaries of PMHS corridors. In addition, the model shows the capability to predict the most common lower extremity injuries observed in pedestrian accidents. Generally, the validated pedestrian model may be used by safety researchers in the design of front ends of new vehicles in order to increase pedestrian protection.
Asunto(s)
Accidentes , Tamaño Corporal , Análisis de Elementos Finitos , Peatones , Adulto , Anciano , Automóviles , Calibración , Femenino , Humanos , Vértebras Lumbares/anatomía & histología , Vértebras Lumbares/fisiología , Masculino , Persona de Mediana Edad , Modelos Anatómicos , Soporte de PesoRESUMEN
Child pedestrian protection deserves more attention in vehicle safety design since they are the most vulnerable road users who face the highest mortality rate. Pediatric Finite Element (FE) models could be used to simulate and understand the pedestrian injury mechanisms during crashes in order to mitigate them. Thus, the objective of the study was to develop a computationally efficient (simplified) six-year-old (6YO-PS) pedestrian FE model and validate it based on the latest published pediatric data. The 6YO-PS FE model was developed by morphing the existing GHBMC adult pedestrian model. Retrospective scan data were used to locally adjust the geometry as needed for accuracy. Component test simulations focused only the lower extremities and pelvis, which are the first body regions impacted during pedestrian accidents. Three-point bending test simulations were performed on the femur and tibia with adult material properties and then updated using child material properties. Pelvis impact and knee bending tests were also simulated. Finally, a series of pediatric Car-to-Pedestrian Collision (CPC) were simulated with pre-impact velocities ranging from 20km/h up to 60km/h. The bone models assigned pediatric material properties showed lower stiffness and a good match in terms of fracture force to the test data (less than 6% error). The pelvis impact force predicted by the child model showed a similar trend with test data. The whole pedestrian model was stable during CPC simulations and predicted common pedestrian injuries. Overall, the 6YO-PS FE model developed in this study showed good biofidelity at component level (lower extremity and pelvis) and stability in CPC simulations. While more validations would improve it, the current model could be used to investigate the lower limb injury mechanisms and in the prediction of the impact parameters as specified in regulatory testing protocols.