1993-08-01

Vehicle Restitution Response in Low Velocity Collisions 931842

The restitution or rebound that occurs as the final phase of a vehicle-to-vehicle collision is quantified by the coefficient of restitution, which is the ratio of the closing velocity to the post-impact separating velocity of the two colliding vehicles. The coefficient of restitution of medium and high velocity collisions is low, [approximately 0.1] since these collisions are quite inelastic, whereas collisions at extremely low velocities are relatively elastic with the coefficient of restitution theoretically approaching 1.0. However, the actual collision restitution magnitude in the low velocity range has not been adequately established. A series of vehicle-to-vehicle and vehicle-to-barrier collisions resulting in velocity changes in the 2 to 5 miles per hour range was conducted in which vehicles with various bumper configurations [factory standard equipment] were utilized to study the coefficient of restitution at low closing velocities. Data from each vehicle-to-vehicle collision in which a stationary vehicle was struck from the rear by another vehicle were recorded with high-speed photography and vehicle-mounted accelerometers. Coefficients of restitution measured from this series of collisions were clustered in the 0.2 to 0.4 range which is significantly lower than previous extrapolations and testing have indicated. A qualitative analysis of the dynamics responsible for this lower than expected restitutive response is described. An analytical method to determine vehicle-to-barrier derived restitutive values is also presented.

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