Head and Neck Dynamics in an Automobile Rollover
Mathematical and Computer Modelling
The purpose of the study was to investigate the effect of roof deformation and head clearance on the dynamic forces transmitted to the head and neck of a restrained occupant in an automobile rollover. A modified version of the Total Articulated Body three-dimensional model was used. The occupant was modeled using fifteen segments connected by fourteen joints. These segments represented the lower torso, center torso, upper torso, neck, head, right upper leg, right lower leg, right foot, left upper leg, left lower leg, left foot, right upper arm, right lower arm, left upper arm, and left lower arm. The automobile was modeled as primary and secondary vehicle segments. The primary vehicle was modeled by 16 contact planes representing the seat cushion, seat back, floor-board, toe-board, left header, windshield, lower dash, mid-dash, instrument panel, left door, right door, fire-wall, footwell, upper dash, header, and latch. The secondary vehicle simulated the intrusion of the roof into the occupant compartment. A lap belt and a shoulder harness were used to hold the occupant in the driver seat. The components of the vehicle and the ground were represented by planes with specified contacts with body segments. Occupant motions indicated various dynamic contacts with the vehicle interior. Higher forces were generally associated with increased accelerations between the occupant's segments (e.g., head) and the vehicle planes (e.g., roof). Increased roof crush increased the forces transmitted to the head-neck region of the occupant. Increased head clearance for a given roof deformation decreased the forces transmitted to the occupant's head and neck. Without roof crush minimal forces were produced. These simulations indicate that for a restrained non-ejected occupant, there is a critical combination of roof crush and head clearance for a given roll velocity that limits the dynamic forces transmitted to the occupant's head and neck. Beyond this threshold an increase in transmitted forces may lead to injury.