Poulard David, Subit Damien, Nie Bingbing, Donlon John-Paul, Kent Richard W
a University of Virginia, Center for Applied Biomechanics , Charlottesville , Virginia.
b Institut de Biomécanique Humaine Georges Charpak, Arts et Métiers ParisTech , Paris , France.
Traffic Inj Prev. 2015;16 Suppl 2:S87-95. doi: 10.1080/15389588.2015.1064529.
The objective of this study was to discuss the influence of the pre-impact posture to the response of a finite element human body model (HBM) in frontal impacts.
This study uses previously published cadaveric tests (PMHS), which measured six realistic pre-impact postures. Seven postured models were created from the THUMS occupant model (v4.0): one matching the standard UMTRI driving posture as it was the target posture in the experiments, and six matching the measured pre-impact postures. The same measurements as those obtained during the cadaveric tests were calculated from the simulations, and biofidelity metrics based on signals correlation (CORA) were established to compare the response of the seven models to the experiments.
The HBM responses showed good agreement with the PMHS responses for the reaction forces (CORA = 0.80 ± 0.05) and the kinematics of the lower part of the torso but only fair correlation was found with the head, the upper spine, rib strains (CORA= 0.50 ± 0.05) and chest deflections (CORA = 0.67 ± 0.08). All models sustained rib fractures, sternal fracture and clavicle fracture. The average number of rib fractures for all the models was 5.3 ± 1.0, lower than in the experiments (10.8 ± 9.0). Variation in pre-impact posture greatly altered the time histories of the reaction forces, deflections and the rib strains, mainly in terms of time delay, but no definite improvement in HBM response or injury prediction was observed. By modifying only the posture of the HBM, the variability in the impact response was found to be equivalent to that observed in the experiments. The postured HBM sustained from 4 to 8 rib fractures, confirming that the pre-impact posture influenced the injury outcome predicted by the simulation.
This study tries to answer an important question: what is the effect of occupant posture on kinematics and kinetics. Significant differences in kinematics observed between HBM and PMHS suggesting more coupling between the pelvis and the spine for the models which makes the model response very sensitive to any variation in the spine posture. Consequently, the findings observed for the HBM cannot be extended to PMHS. Besides, pre-impact posture should be carefully quantified during experiments and the evaluation of HBM should take into account the variation in the predicted impact response due to the variation in the model posture.
本研究旨在探讨撞击前姿势对有限元人体模型（HBM）在正面碰撞中响应的影响。
本研究采用先前发表的尸体试验（PMHS），该试验测量了六种实际撞击前姿势。从THUMS乘员模型（v4.0）创建了七个姿势模型：一个与标准UMTRI驾驶姿势匹配，因为它是实验中的目标姿势，另外六个与测量的撞击前姿势匹配。从模拟中计算出与尸体试验期间获得的相同测量值，并建立基于信号相关性（CORA）的生物逼真度指标，以比较七个模型对实验的响应。
HBM的响应在反作用力（CORA = 0.80 ± 0.05）和躯干下部的运动学方面与PMHS的响应显示出良好的一致性，但在头部、上脊柱、肋骨应变（CORA = 0.50 ± 0.05）和胸部变形（CORA = 0.67 ± 0.08）方面仅发现中等相关性。所有模型均出现肋骨骨折、胸骨骨折和锁骨骨折。所有模型的平均肋骨骨折数为5.3 ± 1.0，低于实验中的（10.8 ± 9.0）。撞击前姿势的变化极大地改变了反作用力、变形和肋骨应变的时间历程，主要体现在时间延迟方面，但未观察到HBM响应或损伤预测有明显改善。仅通过修改HBM的姿势，发现撞击响应的变异性与实验中观察到的相当。姿势化的HBM出现4至8根肋骨骨折，证实撞击前姿势影响了模拟预测的损伤结果。
本研究试图回答一个重要问题：乘员姿势对运动学和动力学有何影响。HBM和PMHS之间观察到的运动学显著差异表明，模型中骨盆与脊柱之间的耦合更强，这使得模型响应对脊柱姿势的任何变化都非常敏感。因此，HBM的研究结果不能推广到PMHS。此外，在实验过程中应仔细量化撞击前姿势，并且在评估HBM时应考虑由于模型姿势变化而导致的预测撞击响应的变化。
