Energy Equivalent Speed
The Energy Equivalent Speed ( EES for short ) is the speed of a vehicle with a total mass m, the kinetic energy of which corresponds exactly to a given deformation energy.
After an accident, the deformation energy can be estimated from the deformation pattern of the vehicle and tabulated comparison values. The deformation energy is the energy that is converted under the assumption of fully plastic deformation . Reversible parts are therefore not taken into account.
If a vehicle actually hits a deformable obstacle, the kinetic energy is not only converted into deformation work on the vehicle, but also into deformation work on the obstacle. There are also reversible parts. The actual collision speed must therefore really be greater than the EES. The EES estimated from the deformation image of the vehicle is approximately the speed of the vehicle that would have caused the same damage in the event of a collision with a rigid obstacle. Since the reversible components were not taken into account (elastic properties of the vehicle structure), the kinetic energy of the vehicle would have to be higher by this proportion in this case too. In the past, the terms EBS (Equivalent Barrier Speed) or BEV (Barrier Equivalent Velocity) were used to compensate for this effect.