Sensitivity of THOR and Hybrid III dummy lower neck loads to belt systems in frontal impact

To determine head-neck biomechanics with a focus on lower neck injury metrics in frontal impact. The mid- and large-size Hybrid III dummies and the mid-size Test device for Human Occupant Restraint (THOR) were positioned on a buck. Tests were conducted at low, medium, and high (3.3, 6.7, and 15.7 m/s) change in velocities using 3 restraint types: normal 3-point belt with no pretension (type A), 10-cm pretension (type B), and 200 N pretension (type C). Repeat tests were conducted. Measured vertical and shear forces and sagittal bending moments were evaluated at the upper and lower regions of the neck to different types of belt systems and at different change in velocities. Peak values normalized with respect to the belt type A were used in the comparative analysis. Metrics transformed to the occipital condyles and T1 were also evaluated.

All dummies showed good repeatability. Peak measured and transformed upper and lower neck moments were greatest in the large-size dummy. The mid-size Hybrid III dummy responded with greater forces and moments than the THOR. Regardless of dummy type, anthropometry, and velocity, peak lower neck moments were more sensitive to belt types than peak lower neck forces. A similar pattern was apparent for upper neck data. Moments in the THOR were more sensitive than moments in the mid-size Hybrid III dummy.

This study offers quantitative generic restraint-based data and addresses response differences between dummies and dummies of the same family. Because of increased sensitivity to belt types at the upper and lower necks for both forces and moments, the THOR appears to be an improvement to better assess injury potential to rear seat occupants wherein frontal impact air bags do not exist.