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In vehicle side collisions, traumatic brain injury caused by the impact between occupant's head and the interior parts of A or B pillar is a major reason of death and disability. In order to analyze the biomechanical response and injury mechanism of occupant's brain in side collisions, a refined finite element head model representing the 50th percentile Chinese male was developed. Its improvements of biofidelity comparing to the original head model were illustrated through model simulation against the same post mortem human subjects test. Based on the refined head model, the brain biomechanical responses and injuries in the side impact with interior parts of A pillar and B pillar were analyzed according to FMVSS 201U, and the influences of different impact locations and directions were investigated. The results showed that the brain tissues on impact side sustained positive pressure and those on the opposite side experienced negative pressure. The transmission of pressure wave was easy to cause brain concussion and other diffuse brain injuries. The intracranial pressure distribution exhibited a typical pattern of contrecoup injury. The extreme stress concentration in the junction area of the cerebrum, cerebellum and brain stem could lead to focal injury such as brain contusion and laceration. Moreover, the impact injury of A pillar was more serious than that of B pillar, which was consistent with the traffic injury statistics that the head injury in oblique side collisions was more serious than that of vertical side collisions. Therefore, the interior parts of A pillar should be designed to absorb more energy than those of B pillar under the same conditions. In addition, the severity of brain injury is more sensitive to the variation of the horizontal angle than that of the vertical angle. Both the peak values of the occipital fossa pressure in effect simulations of the horizontal and vertical angles were three to four times of the peak values of the forehead pressure. When the impact horizontal angle was up to 255, or the vertical angle was up to 45, the head HIC(d) values would be up to 1320.45 and 1101.06, respectively, which indicated a AIS 3 injury risk of the head. [ABSTRACT FROM AUTHOR]

Objective:The occupant's pelvis is very vulnerable to side collision in road accidents. Finite element (FE) studies on pelvic injury help to design occupant protection devices to improve vehicle safety. This study was aimed to develop a highly biofidelic pelvis model of Chinese adults and assess its sensitivity to variations in pelvis cortical bone thickness, bone material properties, and loading conditions. Methods:In this study, 4 different FE models of the pelvis were developed from the computed tomography (CT) data of a volunteer representing the 50th percentile Chinese male. Two of them were meshed using entirely hexahedral elements with variable and constant cortical thickness distribution (the V-Hex and C-Hex models), and the others were modeled with hexahedral elements for cancellous bone and variable or constant thickness shell elements for cortical bone (the V-HS and C-HS models). In model developments, the semi-automatic multiblock meshing approach was employed to maintain the pelvis geometric curvature and generate a high-quality hexahedral mesh. Then, several simulations with postmortem human subjects (PMHS) tests were performed to obtain the most accurate model in predicting pelvic injury. Based on the most accurate model, sensitivity studies were conducted to analyze the effects of the cortex thickness, Young's modulus of the cortical and cancellous bone, impactor velocity, and impactor with or without padding on the biomechanical responses and injuries of pelvis. Results:The results indicate that the models with variable cortical bone thickness can give more accurate predictions than those with constant cortical thickness. Both the V-Hex and V-HS models are favorable for simulating pelvic response and injury, but the simulation results of the V-Hex model agree with the tests better. The sensitivity study shows that pelvic response is more sensitive to alterations in the Young's modulus of cortical bone than cancellous bone. Compared to failure displacement, peak force is more sensitive to the cortical bone thickness. However, displacement is more sensitive to the Young's modulus of cancellous bone than peak force. The padding attached on the impactor plays a significant role in absorbing the impact energy and alleviating pelvic injury. Conclusions:The all-hex meshing method with variable cortical bone thickness has the highest accuracy but is time-consuming. The cortical bone plays a determining role in resisting pelvic fracture. Peak impact force appears to be a reasonable injury predictor for pelvic injury assessment. Some appropriate energy absorbers installed in the car door can significantly reduce pelvic injury and will be beneficial for occupant protection. [ABSTRACT FROM AUTHOR]

The occupant's pelvis is most susceptible to injuries in side collision accidents. To further investigate the pelvis biomechanical responses and injury mechanisms in side impacts, a biofidelic pelvis finite element (FE) model was created. In contrast to previous studies, the model was based directly on the CT data of a volunteer representing the 50th percentile Chinese male. Both cortical and cancellous bone were modeled with hexahedral elements. Through model validations against Post Mortem Human Subjects (PMHS) tests, the pelvis responses and injuries under side impacts were analyzed. Meanwhile, additional simulations were carried out utilizing the validated model to study the effects of the femoral head, impactor pad and impactor velocity on pelvic injuries. The results indicated that the most frequent injury type of the pelvis is pubic rami fracture, followed by fractures of the femoral head, greater trochanter and acetabulum. In validation against the test of Guillemot et al., the critical load of pelvic fracture was 3.8 kN. In validation against the tests of Beason et al., the peak impact force under unpadded load and padded load was 4.3 kN and 3.1 kN, respectively, while the (VC)max was 0.25 m/s and 0.16 m/s, respectively. Peak impact force appears to be a reasonable criterion to assess pelvic injury. Moreover, the femoral head and impactor pad play an important role in absorbing impact energy, distributing impact load, and alleviating pelvic injury. [ABSTRACT FROM AUTHOR]