Delta-V, Barrier Equivalent Velocity and Acceleration Pulse of a Vehicle During an Impact

Delta-V and Barrier Equivalent Velocity (BEV) are terms that have been used for many years to describe aspects of what happened to a vehicle when an impact occurred. That is, they are used to describe some physical change in the vehicle state before the impact as compared to after the impact. Specifically, the Delta-V describes the change in the vehicle velocity vector from just before the impact until just after the impact. The BEV attempts to quantify the energy required to cause the damage associated with an impact.

In order to understand what happens to a vehicle and its occupants during an impact, it is necessary to examine the acceleration pulse undergone by the vehicle during the impact. The acceleration pulse describes, in detail, how the Delta-V occurs as a function of time, and is related with the deformation of the vehicle as well as the object contacted by the vehicle during an impact. While Delta-V and BEV are often used to describe the thresholds at which a passive restraint system will function, it is the acceleration pulse that the sensors of a restraint system measure, and that ultimately determines if, when, and how passive vehicle restraints will be deployed in an impact. This paper examines this issue and gives examples illustrating that the shape and duration of the acceleration pulse experienced by a vehicle in an impact depends on many variables.