Occupant motion in a vehicle rollover accident is a function of many factors. Some important ones are vehicle kinematics, position of the occupant in the vehicle, occupant size, ground topology and restraint usage. The far side belted occupants are more vulnerable than the near side occupants in a rollover accident as they have more energy as a result of their trailing and higher side of the vehicle. This outcome is attributable to the inadequate safety performance of the conventional single loop; B-pillar mounted D-ring restraints. Roof crush tends to displace the vehicle's B-pillar, resulting in D-Ring displacement which causes slack in the lap portion of the restraint. This slack enables centrifugal loads to move the far side occupant further away from the vehicle's instantaneous point of rotation. In this scenario, the presence of any ejection portal can result in an occupant becoming partially or fully ejected.
The coupling technique is used between the Finite Element (FE) LS-DYNA and Multibody-MADYMO code to demonstrate the slack generation in the lap belt during vehicle roof to ground contact. The MADYMO FMVSS 208 driver side rollover simulation is conducted to compare and evaluate seat integrated restraints with the B-pillar mounted D-ring restraints. The head excursion is quantified and used as a response to compare the performance of these two types of restraints. The effectiveness of the buckle pretensioner in a rollover accident is also analyzed by comparing the performance of the restraint with and without the pretensioner.
This study is performed using occupant anthropometry from a real world accident involving a far side belted female occupant who was fully ejected. This study revealed the inadequate performance and failure of the conventional single loop restraint to prevent the far side occupant's excessive head excursion and ejection. This study also demonstrates the superior performance and added advantages of the seat integrated restraint with and without the buckle pretensioner over the B-pillar mounted D-ring restraint.