Parameter Study for Child Injury Mitigation in Near-Side Impacts Through FE Simulations

Abstract

Objective: The objective of this study is to investigate the effects of crash-related car parameters on head and chest injury measures for 3- and 12-year-old children in near-side impacts.

Methods: The evaluation was made using a model of a complete passenger car that was impacted laterally by a barrier. The car model was validated in 2 crash conditions: the Insurance Institute for Highway Safety (IIHS) and the US New Car Assessment Program (NCAP) side impact tests. The Small Side Impact Dummy (SID-IIs) and the human body model 3 (HBM3) (Total HUman Model for Safety [THUMS] 3-year-old) finite element models were used for the parametric investigation (HBM3 on a booster). The car parameters were as follows: vehicle mass, side impact structure stiffness, a head air bag, a thorax–pelvis air bag, and a seat belt with pretensioner. The studied dependent variables were as follows: resultant head linear acceleration, resultant head rotational acceleration, chest viscous criterion, rib deflection, and relative velocity at head impact. The chest measurements were only considered for the SID-IIs.

Results: The head air bag had the greatest effect on the head measurements for both of the occupant models. On average, it reduced the peak head linear acceleration by 54 g for the HBM3 and 78 g for the SID-IIs. The seat belt had the second greatest effect on the head measurements; the peak head linear accelerations were reduced on average by 39 g (HBM3) and 44 g (SID-IIs). The high stiffness side structure increased the SID-IIs’ head acceleration, whereas it had marginal effect on the HBM3. The vehicle mass had a marginal effect on SID-IIs’ head accelerations, whereas the lower vehicle mass caused 18 g higher head acceleration for HBM3 and the greatest rotational acceleration. The thorax–pelvis air bag, vehicle mass, and seat belt pretensioner affected the chest measurements the most. The presence of a thorax–pelvis air bag, high vehicle mass, and a seat belt pretensioner all reduced the chest viscous criterion (VC) and peak rib deflection in the SID-IIs.

Conclusions: The head and thorax–pelvis air bags have the potential to reduce injury measurements for both the SID-IIs and the HBM3, provided that the air bag properties are designed to consider these occupant sizes also. The seat belt pretensioner is also effective, provided that the lateral translation of the torso is managed by other features. The importance of lateral movement management is greater the smaller the occupant is. Light vehicles require interior restraint systems of higher performance than heavy vehicles do to achieve the same level of injury measures for a given side structure.

Keywords:

• Child safety
• Side impact
• Restraints
• Near-side
• Rear seat
• Finite elements
• Evaluations

ACKNOWLEDGMENTS

Henrik Svanberg, Saab Automobile AB, Sweden, contributed with his great experience during the analysis of the simulations and by giving feedback regarding the article.

The financial support by Fordonsstrategisk Forskning och Innovation (FFI), part of VINNOVA, Sweden, and by the Vehicle and Traffic Safety Center at Chalmers (SAFER), Gothenburg, Sweden, is gratefully acknowledged.