Vehicle Dynamics in Non-Collinear Low-Velocity, Rear End Collisions

The vehicle dynamics of non-collinear, low-velocity front-to- rear collisions have received little formal study. The twenty-three angled collisions conducted for this project revealed significant vehicle dynamic differences when compared with similar-energy collinear rear-end collisions. Two recent model year vehicles were used to conduct non-collinear collisions at a nominal 12 km/h impact velocity. The pre-collision angles between the test vehicles were established so that the striking vehicle's line of action through its CG was either 15 or 30 degrees from the stationary struck vehicle's initial heading. Both vehicles had accelerometers at their CG's measuring longitudinal and lateral accelerations. The struck vehicle also had sensors to measure CG vertical accelerations, yaw rates, and longitudinal and lateral velocities. Film from three high-speed 16-mm [film] cameras was digitized and analyzed for each collision. The ΔV at various points within the struck vehicle was studied. The time-history of the center of rotation of the struck vehicle was analyzed and correlated to tire slippage. The ΔV of the struck vehicle decreased as the angle between vehicles increased from 15 to 30 degrees with energy dissipated by suspension motion and scrubbing of the struck vehicle's tires. For the struck vehicle, collisions at 15-degree angles were more akin to pure collinear rear-end collisions; collisions at 30-degree angles showed a more pronounced curvilinear-translation of the CG of the struck vehicle with rotation about a point near its left-front tire. Variations in translational and rotational vehicle dynamics with respect to impact angle were sufficient to alter the resulting occupant motion.