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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]

Coach rollover is one of the most dangerous accidents with respect to fatalities and injuries. The superstructure of a coach has an essential and vital impact on the rollover crashworthiness. To design the optimal superstructure of a coach requires that the effects of superstructure configuration on rollover crashworthiness are thoroughly understood. In order to find the design guidelines for superstructure configurations, this paper studied the influence of coach superstructure configuration on rollover resistance performance. A baseline finite element (FE) model of an intercity coach with semi-integral body is developed. Seven FE models are derived on the basis of the baseline model considering different superstructure configurations, such as closed rings, joints between the side-wall and floor, side window pillar structure as well as distances between the window rails and waistrail. Numerical simulations of rollover test are performed in accordance with the technical prescriptions in ECE Regulation 66. Performance indices, including residual space intrusion amount, energy absorption of each assembly, deformation mode and impact force are calculated and investigated. Results show that the closed rings, the joints between the side-wall and floor assembly as well as structural configurations of the side window pillars have significant effects on the rollover crashworthiness, but the rollover resistance is not sensitive to the distance between the window rail and waistrail. Design guidelines are proposed for coach superstructure to improve rollover crashworthiness based on comparative analysis on performance indices. [ABSTRACT FROM AUTHOR]