Residual Crush
Definition
The permanent, non-recoverable deformation depth remaining after the elastic springback of the vehicle structure. This is what is measured at the scene or from post-crash photographs; it is always less than the maximum dynamic crush that occurred during impact.
- Domain
- Vehicle crash reconstruction
- Measured
- Post-crash, at scene or photos
- Distinct from
- Maximum dynamic crush
- Relationship
- Always less than dynamic crush
Common questions
Why is residual crush always smaller than the dynamic crush that occurred during impact?+
Vehicle structures have some elastic component, so part of the deformation recovers, or springs back, immediately after the peak of the collision, leaving only the permanent portion visible afterward.
Why does this distinction matter for speed estimation?+
Crush-based speed formulas need the actual energy absorbed during impact, so using residual crush without accounting for springback can understate the true 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...
- Dynamic Crush
- The maximum deformation depth at the moment of peak force during impact, before any elastic recovery. Dynamic crush is larger than residual...
- 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...
- 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...