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Published on: September 21, 2017
Parameter study for child injury mitigation in near-side impacts through FE simulations
Marianne Andersson1, Bengt Pipkorn, Per Lövsund
1Chalmers University of Technology, Applied Mechanics, SE-412 96 Göteborg, Sweden. Marianne.andersson@chalmers.se
Insights
Head and thorax-pelvis airbags significantly reduce head and chest injuries in children during side impacts. Seatbelt pretensioners also aid injury reduction, especially when managing lateral movement for smaller occupants.
Area of Science:
- Automotive Safety Engineering
- Biomechanical Injury Analysis
- Child Occupant Protection
Background:
- Near-side impacts pose significant risks to child occupants.
- Understanding the influence of vehicle parameters on child injury is crucial for safety system design.
Purpose of the Study:
- To investigate the impact of crash-related vehicle parameters on head and chest injury metrics for 3- and 12-year-old children in near-side impacts.
- To evaluate the effectiveness of specific safety features in mitigating child injuries.
Main Methods:
- Finite element models of a 3-year-old (HBM3/THUMS) and a 12-year-old (SID-IIs) were used in a validated car model.
- Parametric investigation included variations in vehicle mass, side structure stiffness, head airbag, thorax-pelvis airbag, and seatbelt pretensioner.
- Key injury metrics analyzed were head acceleration, head rotation, chest viscous criterion, and rib deflection.
Main Results:
- Head airbags demonstrated the greatest reduction in head linear acceleration for both child models.
- Seatbelts also significantly reduced head accelerations.
- Thorax-pelvis airbags, vehicle mass, and seatbelt pretensioners most effectively reduced chest injury metrics (viscous criterion and rib deflection) in the SID-IIs.
Conclusions:
- Head and thorax-pelvis airbags are effective in reducing child occupant injuries in side impacts, with design considerations for occupant size.
- Seatbelt pretensioners are beneficial, particularly when combined with systems that manage lateral torso movement, which is more critical for smaller children.
- Lighter vehicles may necessitate higher-performing interior restraint systems to achieve comparable injury reduction to heavier vehicles.
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.
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