Door velocity and occupant distance affect lateral thoracic injury mitigation with side airbag

The relationship between thoracic injury risk and parameters of door velocity and occupant distance was delineated in blunt lateral impact with side airbag deployment. A sled impact model was exercised with the validated MADYMO fiftieth percentile facet occupant model and a generalized finite element torso side airbag. Impact velocity was incremented from 4.0 to 9.0m/s; occupant-airbag distance (at time of airbag activation) was incremented from 2.0 to 24.0 cm; simulations without airbag were also examined. Using compression, deflection rate, and the Viscous Criterion, airbag performance was characterized with respect to occupant injury risk at three points of interest: occupant distance of most protection, distance of greatest injury risk, and the newly defined critical distance. The occupant distance which demonstrated the most airbag protection, i.e., lowest injury risk, increased with increasing impact velocity. Greatest injury risk resulted when the occupant was nearest the airbag regardless of impact velocity. The critical distance was defined as the farthest distance at which airbag deployment exacerbated injury risk. This critical distance only varied considering chest compression, between 3 and 10 cm from the airbag, but did not vary when the Viscous Criterion was evaluated. At impact velocities less than or equal to 6m/s, the most protective occupant location was within 2 cm of the critical distance at which the airbag became harmful. Therefore, injury mitigation with torso airbag may be more difficult to achieve at lower ΔV.

Biomechanical and injury response to posterolateral loading from torso side airbags

This study characterized thoracoabdominal response to posterolateral loading from a seat-mounted side airbag. Seven unembalmed post-mortem human subjects were exposed to ten airbag deployments. Subjects were positioned such that the deploying airbag first contacted the posterolateral thorax between T6 and L1 while stationary (n = 3 x 2 aspects) or while subjected to left lateral sled impact at ΔV = 6.7 m/s (n = 4). Chestband contours were analyzed to quantify deformation direction in the thoracic x-y plane (zero degrees indicating anterior and 180° indicating posterior), magnitude, rate, and viscous response. Skeletal injuries were consistent with posterolateral contact; visceral injuries consisted of renal (n = 1) or splenic (n = 3) lacerations. Deformation direction was transient during sled impact, progressing from 122 ± 5° at deformation onset to 90° following maximum deflection. Angles from stationary subjects progressed from 141 ± 9° to 120°. Peak normalized deflections, peak rates, and VCmax ranges were 0.075 - 0.171, 3.7 - 12.7 m/s, and 0.3 - 0.6 m/s with stationary airbag, respectively; ranges were 0.167 - 0.297, 7.4 - 18.3 m/s, and 0.7 - 3.0 m/s with airbag sled impact, respectively. Peak deflections were measured at angles between 99° - 135° and 98° - 125° for stationary and dynamic conditions, respectively. Because of deflection angle transience and localized injury response, both posterolateral and lateral injury metrics may be required for this boundary condition. Contrasted with flat rigid or anterolateral loading, biomechanical response to side airbag interaction may be augmented by peak normalized deflection or VCmax at 130°.

Thoracic injury metrics with side air bag: stationary and dynamic occupants

OBJECTIVE

Injury risk from side air bag deployment has been assessed using stationary out-of-position occupant test protocols. However, stationary conditions may not always represent real-world environments. Therefore, the objective of the present study was to evaluate the effects of torso side air bag deployment on close-proximity occupants, comparing a stationary test protocol with dynamic sled conditions.

METHODS

Chest compression and viscous metrics were quantified from sled tests utilizing postmortem human specimens (PMHS) and computational simulations with 3 boundary conditions: rigid wall, ideal air bag interaction, and close-proximity air bag deployment. PMHS metrics were quantified from chestband contour reconstructions. The parametric effect of DeltaV on close-proximity occupants was examined with the computational model.

RESULTS

PMHS injuries suggested that close-proximity occupants may sustain visceral trauma, which was not observed in occupants subjected to rigid wall or ideal air bag boundary conditions. Peak injury metrics were also elevated with close-proximity occupants relative to other boundary conditions. The computational model indicated decreasing influence of air bag on compression metrics with increasing DeltaV. Air bag influence on viscous metric was greatest with close-proximity occupants at DeltaV = 7.0 m/s, at which the response magnitude was greater than linear summation of metrics resulting from rigid impact and stationary close-proximity interaction.

CONCLUSIONS

These results suggest that stationary close-proximity occupants may not represent the only scenario of side air bag deployment harmful to the thoraco-abdominal region. The sensitivity of the viscous metric and implications for visceral trauma are also discussed.

Lateral impact injuries with side airbag deployments--a descriptive study

The present study was designed to provide descriptive data on side impact injuries in vehicles equipped with side airbags using the United States National Automotive Sampling System (NASS). The database was queried with the constraint that all vehicles must adhere to the Federal Motor Vehicle Safety Standards FMVSS 214, injured occupants be in the front outboard seats with no rollovers or ejections, and side impacts airbags be deployed in lateral crashes. Out of the 7812 crashes in the 1997-2004 weighted NASS files, AIS > or = 2 level injuries occurred to 5071 occupants. There were 3828 cases of torso-only airbags, 955 cases of torso-head bag combination, and 288 inflatable tubular structure/curtain systems. Side airbags were not attributed to be the cause of head or chest injury to any occupant at this level of severity. The predominance of torso-only airbags followed by torso-head airbag combination reflected vehicle model years and changing technology. Head and chest injuries were coupled for the vast majority of occupants with injuries to more than one body region. Comparing literature data for side impacts without side airbag deployments, the presence of a side airbag decreased AIS=2 head, chest, and extremity injuries when examining raw data incidence rates. Although this is the first study to adopt strict inclusion-exclusion criteria for side crashes with side airbag deployments, future studies are needed to assess side airbag efficacy using datasets such as matched-pair occupants in side impacts.