Upper and lower neck loads in belted human surrogates in frontal impacts.

The upper and lower neck loads in the restrained Hybrid III dummy and Test Device for Human Occupant Restraint (THOR) were computed in simulated frontal impact sled tests at low, medium, and high velocities; repeatability performance of the two dummies were evaluated at all energy inputs; peak forces and moments were compared with computed loads at the occipital condyles and cervical-thoracic junctions from tests using post mortem human surrogates (PMHS). A custom sled buck was used to position the surrogates. Repeated tests were conducted at each velocity for each dummy and sufficient time was allowed to elapse between the two experiments. The upper and lower neck forces and moments were determined from load cell measures and its locations with respect to the ends of the neck. Both dummies showed good repeatability for axial and shear forces and bending moments at all changes in velocity inputs. Morphological characteristics in the neck loading responses were similar in all surrogates, although the peak magnitudes of the variables differed. In general, the THOR better mimicked the PMHS response than the Hybrid III dummy, and factors such as neck design and chest compliance were attributed to the observed variations. While both dummies were not designed for use at the two extremes of the tested velocities, results from the present study indicate that, currently the THOR may be the preferred anthropomorphic testing device in crashworthiness research studies and full-scale vehicle tests at all velocities.

Kinematic analysis of flailing injuries of lower extremities in side impacts.

The objective of the study was to determine the biomechanics of post mortem human subjects (PMHS) in lateral impact with a focus on lower extremity trauma and aviation safety for side-facing seat applications. Four male three-point belted intact PMHS were seated upright with the Frankfurt plane horizontal on a custom seat, covered with aircraft cushion. The seat had an armrest. The change in velocity from the Federal Aviation FAR25.562 standards was input to two specimens, and a lower energy input was used in the other two specimens. Pre-test and posttest x-rays were obtained, and autopsies were conducted. Sled and pelvic acceleration signals were digitally gathered and processed according to the Society of Automotive Engineers specifications. A high-speed digital video camera was used to track the frontal plane kinematics with targets placed at appropriate lower extremity landmarks. Fractures of the left distal femur-knee complex in one and proximal sub-capital femur in the other specimen occurred in tests using the simulated FAR pulse. Tests at the lower energy input in the other specimens did not result in trauma. Coronal motions in PMHS occurred from initial flailing of the lower leg-knee-upper leg complex initiating after the onset of the side-impact pulse with the armrest acting as a limiting/boundary condition for the left femur-pelvis-region. These motions were attributed to be a causal agent for the observed lower extremity injuries. Although from a limited sample size, the present findings indicate that lower extremities may sustain trauma, and side-facing seats in aviation environments may need to be evaluated for occupant safety in the lateral mode.

Demographics, Velocity Distributions, and Impact Type as Predictors of AIS 4+ Head Injuries in Motor Vehicle Crashes.

The objective of the study was to determine differences between the United States-based NASS and CIREN and Australia-based ANCIS databases in occupant-, crash-, and vehicle-related parameters for AIS 4+ head injuries in motor vehicle crashes. Logistic regression analysis was performed to examine roles of the change in velocity (DV), crash type (frontal, far-side, nearside, rear impact), seatbelt use, and occupant position, gender, age, stature, and body mass in cranial traumas. Belted and unbelted non-ejected occupant (age >16 years) data from 1997-2006 were used for the NASS and CIREN datasets, and 2000-2010 for ANCIS. Vehicle model year, and occupant position and demographics including body mass index (BMI) data were obtained. Injuries were coded using AIS 1990-1998 update. Similarities were apparent across all databases: mean demographics were close to the mid-size anthropometry, mean BMI was in the normal to overweight range, and representations of extreme variations were uncommon. Side impacts contributed to over one-half of the ensemble, implying susceptibility to head trauma in this mode. Odds of sustaining head injury increased by 4% per unit increase in DV (OR: 1.04, 95% CI: 1.03-1.04, p<0.001; adjusted for other variables); one-half for belted compared to unbelted occupants (OR: 0.48, 95% CI: 0.37-0.61, p<0.001); nearside, then far-side had significantly higher odds than frontal, and no difference by gender or position (front-left, front-right). Similar crash- and occupant-related outcomes from the two continents indicate a worldwide need to revise the translation acceleration-based head injury criterion to include the angular component in an appropriate format for improved injury assessment and mitigation.