A Study Of Head Biomechanical Response And Injury Mechanisms In Vehicle Traffic Accidents

Head injuries are often sustained in traffic accidents and head traumas are most likely to result in severe injury and death. Medical treatment, compensation, and deaths related to head injuries lead to significant social costs. In 1997, approximately 40 percent of head injuries occurred in traffic accident in U.K. In China, economic development and rapid increases in the number of vehicles have resulted in an increased accident rate, with head injuries making up a significant proportion of injuries suffered in traffic accidents (about 22.5~41%). Therefore, it is vital to conduct research about types of head injuries, injury mechanisms, injury tolerance, and protective measures in China. This study focused on the modeling and validation of a finite element head model based on real human anatomical structures; the resulting model was subsequently used in the reconstruction of a typical pedestrian accident and the analysis of head injury. Finally, a protective measure for head injury was suggested.The human head has an extremely complex structure that includes the most vital organ of the central nervous system, yet methods for studying the human head and brain are quite limited. During the past several decades, many hypotheses have been presented, but an entire systemic theory to explain the head injury mechanism remains lacking. The current work first reviewed previous studies of head mechanical loads and injury mechanisms as well as the application of the finite element method. A study of head injury using software based on the explicit finite element method and multi-body dynamics method was then carried out, ultimately developing a new 3D finite element head model based on the anatomical structure of a real human body. This model was named the Human Body Model-head (or HBM-head). The main structures of the head include the scalp, skull, dura, cerebral spinal fluid, pia mater, cerebrum, cerebellum, brain stem, falx, and tentorium. The entire model consisted of 66,624 nodes, 49,607 solid elements, and 11,514 shell elements and weighed 4.4 kilograms. The material properties of the brain tissue were defined based on the literature.Various classical cadaver experiments were simulated to validate the HBM-head model. The head dynamical parameters and intracranial pressures of simulation were compared with the test results of Nahum (1976) and Trosseille (1992). The pressure gradient distribution of coup and contercoup injury was presented, and the intracranial stress and strain were calculated. In addition, using the Hardy test, the capability of simulating the skull-brain relative motion was validated with the setting. The mechanical properties of skull fracture were validated using foreign skull impact experiments. The results of these simulations fit well with those of previous tests, suggesting that this model has good biofidelity and can be used in the parameter study of intracranial stress and pressure of brain injury and skull fracture.Vulnerable road users—namely, pedestrians and bicyclers—often suffer severe and fatal injuries in car collisions. Head injuries are a high proportion of such traffic accidents. In this study, three typical pedestrian accidents were analyzed and reconstructed using the multi-body pedestrian model and HBM-head FE model, incorporating data from the Accident Research Unit of the Medical University in Hanover, Germany. The method of accident investigation, reconstruction, and injury analysis was presented, discussed, and improved upon. Pedestrians'dynamic responses were reconstructed, and the injury criterion indices calculated from these reconstructions were compared with diagnosis reports, demonstrating that this model has the capability to predict injuries while the calculated injury indices indicate a good ability to predict corresponding injury types and severity.Moreover, pedestrian-windshield impact is a popular study topic in pedestrian safety. A study focused on skull fractures in pedestrian-windshield collisions was implemented based on accident cases. The corresponding vehicle models were established, and the head-windshield impact processes of the accidents were reconstructed. The human skull's contact force and injury condition were simulated in various conditions. The results fit well with the diagnosis reports.The HBM-head model and pedestrian headform model were used to impact different areas of the car windshield. An injury risk distribution figure was presented. The design of a double-side L-shape airbag for pedestrian protection was suggested based on the results of this study, and a multi-body dynamic analysis was carried out to evaluate the protective capability of this airbag. The results indicated that this L-shape airbag can significantly reduce the head impact force in pedestrian-windshield impact as well as the injury risk of skull fractures; it also serves as a cushion to the human head, neck, and shoulders, reducing head injury related to head rotation. Thus, such an airbag is an effective protection device for head injury.China's rapid development in the automotive industry means the prevention of traffic accidents and injuries involving the head are an important problem that requires more attention. The current study developed a human body head model, carried out accident reconstruction and injury analysis to understand traffic injury mechanisms, which provided background knowledge for studies of protective measurements. As such, this work has important practical meaning to the development of vehicle safety and the prevention of traffic injuries.