Reconstruction of Low-Speed Crashes using the Quasi-Static Force vs. Deformation Characteristics of the Bumpers Involved in the Crashes

The purpose of this study was to determine if quasi-static (QS) bumper force-deformation (F-D) data could be used in a low-speed bumper-to-bumper simulation model (1) in order to reconstruct low-speed crashes. In the simulation model, the bumpers that make contact in a crash are treated as a system. A bumper system is defined as the two bumpers that interact in a crash positioned in their orientation at the time of the crash. A device was built that quasi-statically crushes the bumpers of a bumper system into each other and measures the compression force and the deformation of the bumper system. Three bumper systems were evaluated. Two QS F-D measurements were performed for each bumper system in order to demonstrate the repeatability of the QS F-D measurement. These measurements had a compression phase and a rebound phase. A series of crash tests were performed using each bumper system. In each crash test, a stationary target vehicle was struck on the rear bumper by the front bumper of a bullet vehicle. Both vehicles were instrumented with accelerometers. The bullet vehicle had load cells at the front that measured crash forces and a displacement sensor that measured the deformation of the bumper system during the crash. The crash tests were performed over a range of impact speeds for the bullet vehicle. The compression QS F-D data were used as an input to the simulation model in order to reconstruct the vehicle motions in the crash tests. The other inputs required to simulate a crash test were the impact speed of the bullet vehicle, the vehicle masses and the coefficient of restitution measured in the crash test. The study demonstrated that the simulation model with the QS F-D data accurately recreated the velocities of the target and bullet vehicle in the crash tests.