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  1. During high-speed rear impacts with delta-V > 25 km/h, the front seats may rotate rearward due to occupant and seat momentum change leading to possibly large seat deflection. One possible way of limiting this may be by introducing a structure that would restrict large rotations or deformations, however, such a structure would change the front seat occupant kinematics and kinetics. The goal of this study was to understand the influence of seat back restriction on head, neck and torso responses of front seat occupants when subjected to a moderate speed rear-impact. This was done by simulating a rear impact scenariomore »with a delta-V of 37.4 km/h using LS-Dyna, with the GHBMC M50 occupant model and a manufacturer provided seat model. The study included two parts, the first part was to identify worst case scenarios using the simplified GHBMC M50-OS, and the second part was to further investigate the identified scenarios using the detailed GHBMC M50-O. The baseline condition included running the belted GHBMC on the seat at the specified pulse. This was followed by including a seatback constraint, a restriction bar, at 65 mm from the seat back to restrict rearward movement. Four different scenarios were investigated using the GHBMC M50-OS for the first part of the study both in the baseline and inclusion of a restriction bar behind the seatback: occupant seated normally; occupant offset on the seat; occupant rotated on the seat; and occupant seated normally but at a slightly oblique rear impact direction. The oblique condition was identified as the worst-case scenario based on the inter-vertebral kinematics; therefore, this condition was further investigated in the simulations with GHBMC M50-O. In the oblique rear impact scenario, the head missed the head restraint leading to inter-vertebral rotations exceeding the physiological range of motions regardless of the restriction bar use. However, adding a restriction bar behind the seat back showed a higher HIC and BrIC in both normal and oblique pulses due to the sudden stop, although the magnitudes were below the threshold.« less
  2. Objective: Assess strength in adult females using multiple positions, motions, and contraction types, to better understand strength production of young and non-symptomatic of adult female subjects to help assess and improve the biofidelity of anthropomorphic test devices and human body models. Methods: Fifteen adult females (25.4 ± 6.3 years) were recruited for this study. Strength measurements were collected for the sagittal and coronal planes during isometric, concentric, and eccentric muscle contractions in neutral and mid-range of motion anatomical positions. Results: For both planes, subjects were strongest during eccentric muscle contractions and weakest in concentric muscle activations. In the sagittal plane,more »subjects were stronger in extension for all muscle activation types and anatomical positions. In the coronal plane, there were no side differences in isometric nor concentric strength. Conclusions: Neck strength of adult females depends on muscle activation type and anatomical positions. Future computational models should account for muscle activation type when quantifying responses of female subjects.« less