Dynamic Crush
Definition
The maximum deformation depth at the moment of peak force during impact, before any elastic recovery. Dynamic crush is larger than residual crush by a restitution factor; the CRASH3 model includes a correction for this.
- Field
- Vehicle crash reconstruction
- Definition point
- Peak force during impact
- Compared to
- Residual crush, larger by a restitution factor
- Used in
- CRASH3 damage model
Common questions
Why is dynamic crush always larger than the residual crush measured after the crash?+
Some of the deformation recovers elastically once the peak impact force passes, similar to a spring partially rebounding, so the crush depth visible during post-crash inspection is less than the maximum deformation that actually occurred at the moment of highest force.
How does the restitution factor get applied in CRASH3 to correct for this difference?+
CRASH3 applies a coefficient of restitution appropriate to the impact speed and vehicle stiffness to scale the measured residual crush back up toward the dynamic crush value, which is what feeds into the crush-energy calculation used to estimate impact speed.
Related terms
- CRASH3
- Calspan Reconstruction of Accident Speeds on the Highway version 3: a mathematical model that relates permanent crush depth to absorbed energy through...
- Energy Equivalent Speed (EES)
- The speed at which a vehicle would strike a rigid fixed barrier to absorb the same amount of energy as observed from...
- Residual Crush
- The permanent, non-recoverable deformation depth remaining after the elastic springback of the vehicle structure. This is what is measured at the scene...
- SMAC
- Simulation Model of Automobile Collisions: a trajectory and damage simulation that uses CRASH3-type stiffness data to model full collision kinematics, including vehicle...
- Stiffness Coefficients a and B
- Vehicle-specific constants derived from staged barrier crash tests. A is the force threshold below which no permanent crush occurs (N/m width). B...