Pediatric head contours and inertial properties for ATD design

Comparison of Upper Neck Loading in Young Adult and Elderly Volunteers During Low Speed Frontal Impacts

Cervical pain and injuries are a major health problem globally. Existing neck injury criteria are based on experimental studies that included sled tests performed with volunteers, post-mortem human surrogates and animals. However, none of these studies have addressed the differences between young adults and elderly volunteers to date. Thus, this work analyzed the estimated axial and shear forces, and the bending moment at the craniocervical junction of nine young volunteers (18–30 years old) and four elderly volunteers (>65 years old) in a low-speed frontal deceleration. Since the calculation of these loads required the use of the mass and moment of inertia of the volunteers' heads, this study proposed new methods to estimate the inertial properties of the head of the volunteers based on external measurements that reduced the error of previously published methods. The estimated mean peak axial force (Fz) was −164.38 ± 35.04 N in the young group and −170.62 ± 49.82 N in the elderly group. The average maximum shear force (Fx) was −224.42 ± 54.39 N and −232.41 ± 19.23 N in the young and elderly group, respectively. Last, the estimated peak bending moment (My) was 13.63 ± 1.09 Nm in the young group and 14.81 ± 1.36 Nm in the elderly group. The neck loads experienced by the elderly group were within the highest values in the present study. Nevertheless, for the group of volunteers included in this study, no substantial differences with age were observed.

The Large Omnidirectional Child (LODC) ATD: Biofidelity Comparison with the Hybrid III 10 Year Old

When the Hybrid III 10-year old (HIII-10C) anthropomorphic test device (ATD) was adopted into Code of Federal Regulations (CFR) 49 Part 572 as the best available tool for evaluating large belt-positioning booster seats in Federal Motor Vehicle Safety Standard (FMVSS) No. 213, NHTSA stated that research activities would continue to improve the performance of the HIII-10C to address biofidelity concerns. A significant part of this effort has been NHTSA's in-house development of the Large Omnidirectional Child (LODC) ATD. This prototype ATD is comprised of (1) a head with pediatric mass properties, (2) a neck that produces head lag with Zaxis rotation at the atlanto-occipital joint, (3) a flexible thoracic spine, (4) multi-point thoracic deflection measurement capability, (5) skeletal anthropometry representative of a seated child, and (6) an abdomen that can directly measure belt loading. The objective of this study was to evaluate the LODC by comparing its body region and full-body responses to both standard HIII-10C responses and pediatric biomechanical data. In body region tests, the LODC (BioRank = 1.21) showed improved biofidelity over the HIII-10C (BioRank = 2.70). The LODC also exhibited kinematics more similar to pediatric PMHS kinematics in a reconstruction test. In FMVSS No. 213 tests, the LODC was observed to have lower HIC values with the absence of hard chin-to-chest contacts, indicating that chin-to-chest contact severity is mitigated in the LODC design. LODC abdomen pressures and belt penetrations discriminated between restraint conditions. These results suggest the LODC has biofidelic characteristics that make it a candidate for improved assessment of injury risk in restraint system development.