A: NO!
- Restitution is not included in the fundamental equations of CRASH.
- Restitution is NOT included in any commercial version of CRASH.
- A partial dimensional recovery and
- A partial restoration of kinetic energy.
Subsequent to the peak dynamic deformation, the collision partners begin a restitution phase as the deformed structures restore kinetic energy, or "spring" back.
The restitution force level and duration determine the impulse that acts on the collision partners during the restitution phase.
At the present time, crush coefficients for vehicle collision analysis are predominantly based on impact speeds and damage measurements from rigid, fixed barrier crash tests.
- The residual damage is correlated with the impact speed by means of fitted linear relationships.
- In general, there is no consideration given to the effects of restitution in applications of the fitted crush coefficients.
- corresponding to a given amount of residual crush,
- are compounded by the fact that restitution acts to reduce the amount of residual deformation, for a given maximum dynamic crush,
- while also acting to increase the total impact speed change.
- NOTE: Why such simplifications? See Why was the CRASH program created?, which includes:
- As a pre-processor for SMAC! NHTSA liked it and since ONLY for statistical studies, NHTSA didn't mind the possibility of large errors, they'd be insignificant as they were looking for a uniform collision reconstruction procedure to determine trends in injuries vs impact types
- Effects of Restitution in the Application of Crush Coefficients",
which initially encountered misguided erroneous criticism apparently to try to thwart publication
- in a recent SAE book Crash Reconstruction Research: 20 Years of Progress (1988-2007).
- We have not created a commercial version of CRASH with our restitution enhancements partially because of the joyous reception the paper received these past 10+ years. ,
and secondly because we have numerous other research projects that are keeping us busy.
Yep. Seen it in testimony wherein they relayed
- "that since the measurements to determine the crush stiffness values are the restituted crush measurements then obviously CRASH includes restitution!"
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FOOTNOTE
Restitution is NOT included in any commercial version of CRASH.
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For additional information on damage analysis & CRASH, please see:
- The Algorithms of CRASH, paper presented at 2001 SECCC, Aug 2001
- NHTSA CRASH3 Technical Manual - 1986 NHTSA collection/summary of CRASH papers
- From the McHenry Forum Topic on CRASH:
- Why was the CRASH program created?
- What Speed Should I Use to Calculate CRASH3 A&B Coeff?
- Is CRASH damage analysis a virtual relationship?
- Should a CRASH type damage analysis include induced damage?
- What is the "No Damage Intercept" of CRASH
- Can You Use Maximum Crush For CRASH A&B Crush Coefficients?
- Effects of Restitution in the Application of Crush Coefficients
- Crush Coefficients Conversions: CRASH (McHenry), Campbell, WinSMASH (Prasad)
..and more, see the McHenry Forum and specifically the McHenry Forum topic CRASH and Damage Analysis