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Vehicle frontal crashworthiness analysis is an important topic in the field automotive community, as it relates to legislative requirements. Frontal crash models contain a large number of elements and therefore present a high computational cost, especially when performing crashworthiness structural performance optimisations. A new numerical methodology is proposed in this paper with the aim to increase computation speed by implementing a sub-modelling approach on the frontal structure-rear wheels (FSRW) method. In this new method, the vehicle body structure behind the rear seats is replaced by a point mass, with an equivalent mass to the rear structure removed, and attached to the rear frame of the front structure and its wheels. This new method was rigorously tested against validated full size vehicle computer models of different classes provided by NHTSA, and included MPV, SUV, van, and sedan, against fixed rigid barrier (FRB), small overlap and a mobile progressive deformable barrier (MPDB) tests. The research has demonstrated that this new sub-modelling approach correlated against all the full size NHTSA computer models in deformations, intrusions, velocities, and accelerations, as well as providing a runtime average reduction between 7% and 23%. This new simplified method, which can be easily implemented, is innovative and will have an important impact vehicle design, as it will allow an easier use of optimisation techniques, which will lead to safer vehicles. [ABSTRACT FROM AUTHOR]

The objective of this study was to explore the relevance between Autonomous Emergency Braking (AEB) control strategy and occupant pre-impact kinematics among a typical real-world cut-in impact scenario. First, the accident scenario was built with PreScan software after accident analysis. Second, a MADYMO simulation model with Active Human Model (AHM) was built and validated with the volunteer test carried out by our team. Finally, the AEB module and related control strategies were introduced into the main vehicle, and the effects of different strategies on the occupant kinematic were evaluated. The simulation results indicated that it was efficient to evaluate the occupant kinematics during pre-impact phase through vehicle and occupant integrated simulation method. The main vehicle's velocity could be reduced between 5 km/h and 14 km/h respectively after introducing different AEB control strategies, which was less than the one manoeuvred by driver (22 km/h). Earlier activation of the AEB and heavier braking could result in larger up-body displacement, but less final impact velocity, and the maximum head displacement reached 172.56 mm due to the AEB control. Comparing partial braking with detection angle 9° case with 100% braking with detection angle 18° case, the head, thorax and shoulder displacements were increased by 94.8%, 104.1%, and 48.7%. This research is beneficial for the subsequent integrated safety analysis. [ABSTRACT FROM AUTHOR]

The causes of fatal and serious injuries in rollover accidents have yet to be fully identified. This study aimed to reconstruct a complex accident, based on both video analysis and vehicle coupling simulation. Besides, the major fatal injury causation and curtain airbag's effectiveness were analyzed. The coupling model, including finite element tire and multi-body vehicle body, was developed to estimate the vehicle trajectory. A validated curtain airbag (CAB) module, was introduced for occupant protection effectiveness evaluation. The vehicle trajectory from the simulation correlated well with that from video recordings and simulation result indicated that passenger's head contact with road (maximum contact force 9834.9 N) was assumed to be the main reason of the victim death. After introducing the CAB, the maximum head acceleration was reduced from 129.1 g to 24.9 g, and the neck Fz was reduced by 80.0% as well. The coupling simulation method turned out to be efficient to reconstruct certain complex accident case. Such study is beneficial for further similar accident reconstruction and restraint system evaluation. [ABSTRACT FROM AUTHOR]

The biofidelity is an essential requirement of the application of human head finite element (FE) models to investigate head injuries under mechanical loadings. However, the influence of the foramen magnum boundary condition (FMBC) on intracranial dynamic responses under head impacts has yet to be fully identified until now. This study aimed to investigate the effect of different modeling methods of the FMBC on intracranial dynamic responses induced by forehead impact, especially the axonal injury associated dynamic responses. The total human model for safety (THUMS) was applied in this study. Two FE models with different FMBC modeling methods were developed from the THUMS model. Then, three forehead impact FE models were established respectively, including the original THUMS model. Further FE simulations were conducted to investigate the influence of FMBC modeling methods on intracranial dynamic responses. Though, difference between the intracranial dynamic responses (relative skull-brain motion and strain responses) at areas far from the foramen magnum were slightly, the corresponding difference at the brain stem area were distinctly. Meanwhile, the predicted axonal injury risk of the brain stem white matter was varying among each other. Different modeling methods of FMBC could result in different intracranial dynamic responses of the brain stem, and affect the axonal injury prediction. Therefore, the modeling of the FMBC should be further evaluated for the study of brain stem injury using human head FE models. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the brain-strain-based thresholds for better prediction of the diffuse axonal injury (DAI) induced by a rotational acceleration on the rat brain. A previously developed and validated rat head finite element model was used to reconstruct 26in vivorat head impact experiments. DAI was produced via the high rotational acceleration applied to the rat head on the sagittal plane. Intracranial strain and strain-based injury indexes were calculated, including the maximum principal strain (MPS), the product of strain and strain rate, and the cumulative strain damage measure (CSDM). The region-specific conservative thresholds for DAI were estimated in terms of strain and strain-based injury indexes in the frontal, middle, and occipital regions of the corpus callosum. The axonal injuries observed in the experiments were used to formulate the injury risk functions, and the DAI risks were analysed via binary logistic regressions in terms of the calculated injury indexes. The logistic regression analysis demonstrated that the MPS, the product of strain and strain rate, as well as the CSDM were significantly correlated with DAI in the frontal corpus callosum. For the 50% probability of DAI in the frontal corpus callosum, it is suggested that the strain-based threshold is 0.12 for the MPS, 110 s−1for the product of strain and strain rate, and 17% for the CSDM. [ABSTRACT FROM PUBLISHER]

Purpose: The purpose of this study was to evaluate the capability of the Total Human Model for Safety (THUMS) - pedestrian model in predicting pedestrian injuries, and to investigate pedestrian injury mechanisms in minivan collisions via numerical reconstruction of a real world minivan-to-pedestrian impact case., Methods: A typical minivan-to-pedestrian collision case was selected from the In-depth Investigation of car Accidents in Changsha (IVAC) database. The THUMS middle-size adult male FE model and a minivan front FE model were then employed to represent the case participants and injuries to the pedestrian's lower limb, thorax and head were reconstructed. Finally, the capability of the THUMS model in predicting pedestrian injuries and pedestrian injury mechanisms in minivan collisions were analyzed through comparisons between predictions and the accident data., Results: The results show that the THUMS has a good capability in predicting pedestrian thorax injuries, but a lower prediction of leg bending moment and brain strain. The extra bull bar concentrates crash load to pedestrian's leg and raises tibia/fibula fracture risk, thorax injuries in the struck side are mainly from direct contact at the lower chest level, lung injury in the non-struck side could be caused by inertia force from the heart. Rotational acceleration shows good match with brain strain and could be the key mechanism for concussion., Conclusions: The results suggest that further improvement in biofidelity of the THUMS model is still needed. The findings also offer basic understanding on pedestrian injury mechanisms in minivan collisions.

The objective of this study was to determine the visco-hyperelastic constitutive law of brain tissue under dynamic impacts. A method combined by finite element simulations and optimization algorithm was employed for the determination of material variables. Firstly, finite element simulations of brain tissue dynamic uniaxial tension, with a maximum stretch rate of 1.3 and strain rates of 30 s -1 and 90 s -1 , were developed referring to experimental data. Then, fitting errors between the engineering stress-strain curves predicted by simulations and experimental average curves were assigned as objective functions, and the multi-objective genetic algorithm was employed for the optimation solution. The results demonstrate that the brain tissue finite element models assigned with the novel obtained visco-hyperelastic material law could predict the brain tissue's dynamic mechanical characteristic well at different loading rates. Meanwhile, the novel material law could also be applied in the human head finite element models for the improvement of the biofidelity under dynamic impact loadings.