Energy Dissipation in High Speed Frontal Collisions

One element of primary interest in the analysis and reconstruction of vehicle collisions is an evaluation of impact severity. The severity of an impact is commonly quantified using vehicle closing speeds and/or velocity change (delta-V). One fundamental methodology available to determine the closing speed and corresponding velocity change is an analysis of the collision based on a combination of the principles of Conservation of Momentum and Conservation of Energy. A critical element of this method is an assessment of the amount of kinetic energy that is dissipated during plastic structural deformation (crush) of the involved vehicles. This crush energy assessment is typically based on an interpolation or an extrapolation of data collected during National Highway Traffic Safety Administration (NHTSA) sponsored crash testing at nominal speeds of 30 or 35 mph.

In this study, the frontal impact force-deformation and energy-deformation properties for a single vehicle platform were compared over a wide range of impact speeds up to 100 mph (Figure 1). The vehicle's dynamic structural deformation and the corresponding forces produced were evaluated, and the vehicle's energy dissipation properties were examined regarding speed dependence. The predictive ability of various crush energy models that have been previously presented in the technical literature was evaluated using data from frontal barrier crash testing at various speeds ranging from 21 to 50 mph.