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Citation
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Maehara K, Dokko Y, Ohhashi K. 27th International Technical Conference on the Enhanced Safety of Vehicles (ESV); April 3-6, 2023; Abstract #: 23-0228, pp. 13p. Washington, DC USA: US National Highway Traffic Safety Administration, 2023 open access. |
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Abstract
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27th International Technical Conference on the Enhanced Safety of Vehicles (ESV): Enhanced and Equitable Vehicle Safety for All: Toward the Next 50 Years
https://www-esv.nhtsa.dot.gov/Proceedings/27/27ESV-000228.pdf
In Japan, the ratio of the elderly in traffic accident fatalities has been increasing, and the thorax is the most frequently injured body region. Therefore, preventing chest injury to the elderly is one of the key issues to achieve zero fatalities. For this reason, several detailed analyses of the chest injury mechanism have been performed using elderly human body models (HBM). In a previous study, under frontal crash condition, it was observed that the forward motion of the internal organ and the forward rotation of the upper torso push up the lower ribs, potentially leading to rib fractures. In this study, a novel occupant restraint concept was devised that could reduce chest injury due to the mechanism above, and its effectiveness was verified using an elderly HBM and THOR. On the devised restraint system, a pair of shoulder belts that pass from left and right sides of the occupant shoulder to the same sides of flank were placed. The aim of them was dispersing the restraint force applied to the thorax of an occupant. A membrane was placed wrapping the abdomen between the two shoulder belts, which aimed to reduce the protrusion of the internal organ during a frontal crash. For the devised restraint system, a series of CAE calculation using the elderly HBM was performed in the two crash conditions of FR56K and OMDB in comparison with the conventional 3P belt, and the effect for reducing the number of fractured ribs (NFR) was confirmed. Then, another series of CAE calculation using the THOR FE model was performed in the same conditions, and several chest injury criteria such as Rmax, PC Score, TIC_NFR, and TIC_NSFR were calculated. Finally, injury probabilities for these criteria of THOR and NFR of the HBM were compared. Comparing the devised restraint system with the 3P belt, NFRs of the elderly HBM were significantly reduced, and all chest injury criteria of THOR were reduced, under both load cases. In the OMDB condition using the devised system and THOR, The chest deflection at inner lower was the largest, and Rmax was relatively high than other chest injury criteria. In the same condition, TIC_NSFR showed the best correlation with the NFR of the elderly HBM. It was considered the reason why Rmax was high on OMDB was that THOR had a more protruded ribcage around the lower region than the elderly HBM, which caused higher concentrated load on this region pushed by the shoulder belt. The reason why the TIC_NSFR on OMDB was low was considered to be that the devised system restrained the chest evenly on the left and right, and the value of the term that indicates the left-right difference of the upper chest deflection in the TIC_NSFR formula became smaller. It was found that the devised chest restraint system could significantly reduce rib fractures of the elderly HBM in a frontal crash. It was also found that when the devised system was evaluated with THOR, every chest injury criterion was reduced.
Language: en |