ATD (Anthropomorphic Test Dummy) Injury Metric Development

1 Lower Neck Injury in Rearward Loading. A total of 18 post mortem human surrogates (PMHS) were selected for this phase of the study. Each PMHS was exposed to accelerations inducing a combination shear force and extension moment of the neck. Matched pair testing of the Hybrid III and THOR Anthropomorphic Test Devices (ATDs) were also conducted in the same loading conditions, allowing direct comparison of the ATD responses and injury outcomes reported in the PMHS tests. A lower neck injury criteria (LNij) was calculated using parametric survival analysis for the PMHS, Hybrid III, and THOR using a critical intercept for both the shear force and extension moments. The resulting injury risk curves (IRCs) were calculated along with confidence intervals. The quality of the fit for each injury assessment reference values (IARVs) was evaluated using the normalized confidence interval size (NCIS). The LNij was evaluated at the 5% risk level (consistent with NASA standards for injury risk during dynamic phases of flight). For the PMHS and THOR ATD, the LNij was found to be a good fit. For the Hybrid III ATD, the LNij fit was found to be fair.

2 Vertical Neck Loading. A total of 36 PMHS were selected for this phase of the study. There were 2 groups used for testing, a group that was tested in an upright orientation, and the other tested in an inverted orientation. Each PMHS head-neck was loaded axially inducing a compression force. Because of the nature of the loading, and because ATD responses are not biofidelic, matched pair testing of the Hybrid III and THOR ATDs could not be conducted. As with the previous phase, the injury metric (axial force) was calculated using parametric survival analysis for the PMHS. The resulting IRCs were calculated along with confidence intervals with the same quality assessment used. The axial force was evaluated at the 5% risk level and found have a good fit quality in both the upright and inverted tests, as well as with the combined female data set of all ages.

3. Upper and Lower Neck under Lateral Loading. A total of 11 PMHS were selected for this phase of the study. There were 3 groups used for testing, with varying torso restraint used. Each PMHS was accelerated laterally, inducing a combined lateral moment, lateral shear force, and axial tension force in the neck of the PMHS. Matched pair testing of the Hybrid III and THOR ATD were also conducted in the same loading conditions, allowing direct comparison of the ATD responses and injury outcomes reported in the PMHS tests. As with the previous phase, the injury metric (lower lateral neck injury criteria, lower LatNij) was calculated using parametric survival analysis for the PMHS. The resulting IRCs were calculated along with confidence intervals with the same quality assessment used. The lower LatNij was evaluated at the 5% risk level. For the PMHS and THOR ATD, the lower LatNij was found to be an excellent fit. For the Hybrid III ATD, the lower LatNij fit was found to be a good.

4. Thorax in Lateral Loading. A total of 17 PMHS were selected for this phase of the study. Each PMHS was accelerated laterally, inducing chest deflection in the torso of the PMHS. Matched pair testing of the THOR ATD was also conducted in the same loading conditions; however, the instrumentation in the THOR chest did not respond significantly to the lateral deflections. The Hybrid III lacks lateral instrumentation required to respond to lateral loading and was not tested. As with the previous phase, the injury metric (lateral chest deflection) was calculated using parametric survival analysis for the PMHS. The resulting IRCs were calculated along with confidence intervals with the same quality assessment used. The lateral chest deflection was evaluated at the 5% risk level on the PHMS and was found to be an excellent fit.

5. Pelvis in Lateral Loading. A total of 22 PMHS were selected for this phase of the study. Each PMHS was loaded directly with a pendulum mass centered on the greater trochanter. Matched pair testing of the THOR ATD was also conducted in the same loading conditions; however, the instrumentation in the THOR acetabulum load cells reached their maximum range before reaching the injury conditions in the PMHS and thus the results were not able to be used to create IARVs. The Hybrid III lacks lateral instrumentation required to respond to lateral loading and was not tested. As with the previous phase, the injury metric (lateral greater trochanter force) was calculated using parametric survival analysis for the PMHS. The resulting IRCs were calculated along with confidence intervals with the same quality assessment used. The lateral greater trochanter force was evaluated at the 5% risk level on the PHMS and was found to be a good fit.