In Phase I, 35 Hybrid III, 26 THOR, and 212 human volunteer tests were chosen to validate the Humanetics 50th percentile Hybrid III, NASA version of the 50th percentile THOR-K, and the Global Human Body Models Consortium (GHBMC) simplified 50th percentile male (GHBMC M50-OS) finite element (FE) models, respectively. Seat and restraint configuration models matching chosen test configurations were developed. Each unique test condition was simulated and model response was evaluated. The sled pulse from each configuration was applied to the appropriate model and instrumented acceleration and force signals were extracted. Each simulated metric was compared to the matched physical responses of the ATD or human volunteer to quantitatively compare physical and simulated signals. The CORA (CORrelation and Analysis) comprehensive score metric was used to evaluate the model response against the matched physical test across several signals and ranged from 0 to 1, with unity being a perfect match, and 0 representing no correlation.

In Phase II, the Humanetics 50th percentile Hybrid III, NASA version of the 50th percentile THOR-K, and the Global Human Body Models Consortium simplified 50th percentile male (GHBMC M50-OS) FE models were used to examine the effects of loading condition and environmental parameters on injury metric response. Boundary conditions were parameterized and categorized as loading condition variables or environmental variables, the latter of which are expected to be less controllable than the former. Loading condition parameters included acceleration pulse shape, relative magnitude, and peak resultant acceleration. Environmental variables included belt forces, seat orientation with respect to gravity at impact time, and initial positioning on the model with respect to the seat vertex. Parameters were varied using a Latin Hypercube Design of Experiments to generate 455 simulations per model. A total of 1365 simulations were developed for this study, 97.9% of which reached termination without error. Ten injury metrics were compared using statistical methods detailed above.

In Phase III, the Humanetics 50th percentile Hybrid III, NASA version of the 50th percentile THOR-K, and the Global Human Body Models Consortium simplified 50th percentile male (GHBMC M50-OS) FE models were positioned and belted in FE representations of three spacecraft-like seat and restraint systems as well as the simplified seat model from Phase I and II. The Latin hypercube design (LHD) designed in Phase II of this study was developed based on a factorial matrix of loading direction, and acceleration pulse rise time, consisting of 20 unique acceleration profiles. However, these profiles were never directly simulated.

RESULTS:

Phase 1

In respect to the overall average comprehensive CORA score, both the Hybrid III and THOR models had a CORA score of at least 0.8, as hypothesized for this phase. The THOR had the highest score of the 3 models with all directional average scores scoring at least 0.8; however, the THOR lacked data for the +X-direction. The Hybrid III had the second highest overall average comprehensive CORA score, with only the +X-direction loading group scoring under 0.8. On the other hand, the GHBMC model had only a single direction group, +Z, that scored above 0.8. Active bracing of the human volunteers may have contributed to the low CORA scoring.

Phase 2

It was determined for each region that the loading condition variables generally were more predictive of injury metric outcome compared the environmental variables. In some regions, including the neck, lumbar spine, and lower extremities, the GHBMC response more closely resembled the THOR. In the head, thorax, and pelvis, the GHBMC had results closer to that of the Hybrid III. It was determined that discrepancies exist in injury prediction fidelity of both ATDs when comparing to human volunteer response that vary by body region and specific metrics. Further work should examine these potential differences using more vehicle-specific seats, harnesses, and helmets.

Phase 3

A total of 915 simulations were run for this study, 97% of which reached termination without error. The Hybrid III and GHBMC exhibited higher rotational head injury metric distributions when equipped with a helmet compared to the simplified seat model. However, for the THOR, median BrIC decreased compared to the simplified seat. For each occupant model, pelvis acceleration tended to be pretty similar across the loading seat models. With the Hybrid III model, there was no statistically significant difference in matched pelvis accelerations between any of the spaceflight-like configurations and the simplified seat. However, with GHBMC the pelvis acceleration in each seat model was decreased compared to the simplified seat.