One thing to note/always check on Crush Coefficients:
- What is the 'no damage intercept'?
- Calculate the CRASH inputs A/B to get the value
- A lot of folks who sell coefficients force a 4-5 mph intercept
- Some published crush coefficients are a mess:
- For example the CRASH3 update by Monk/Guenther
- They did not understand the science behind CRASH
- They won the contract for the CRASH3 update on a competitive bid against Calspan (who invented CRASH!).
- They spent the majority of the contract dollars apparently trying to understand what Ray McHenry/Calspan had created with CRASH/CRASH2
- Monk/Guenther tried to 'cover their tracks' by
- arbitrary and subjective 'adjustments' of their crazy values for the crush coefficients A & B and corresponding > 5mph 'no damage intercept' to try to better match Ray's/Calspan's CRASH work better
- And i say crazy since
- they had data points from their 'CRASH3' crash test information,
- the Ray/Calspan/CRASH2 fits had data points,
- they should have taken the DATA into consideration for the virtual crush coefficient slope line while also recognizing the need to have a lower, more reasonable 'no damage' intercept.
- Then they could have found a more scientific basis instead of their arbitrary and subjective adjustments.
- And i say crazy since
- arbitrary and subjective 'adjustments' of their crazy values for the crush coefficients A & B and corresponding > 5mph 'no damage intercept' to try to better match Ray's/Calspan's CRASH work better
- Use exercise extreme caution when applying CRASH, aka Damage Analysis, particularly to very low speed collisions
- For example the CRASH3 update by Monk/Guenther
For additional information,
- See the topic Truck Crush properties for a sample check.
- Please see Over 60 years of McHenry Highway Safety Publications
- Not all the documents are online
- We have all the documents,
- if you want/need one not yet online, let us know and we can see about scanning it an posting online
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