The "No Damage Intercept" of CRASH

[MSI]

As part of a response to a question on Truck Crush properties and an error in the referenced SAE paper, we added this topic with important information on the "no damage intercept' and CRASH in general

One thing to note/always check on Crush Coefficients:

• What is the 'no damage intercept'? Calculate the CRASH inputs A/2B 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.
      • They spent the majority of the contract dollars apparently trying to understand what Ray McHenry/Calspan had created with CRASH/CRASH2
      • They then 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, and 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.
    • exercise extreme caution when applying CRASH to very low speed collisions
  Be sure to check!
  • See the topic Truck Crush properties for a sample check.
  For additional information on CRASH please see the original CRASH references listed here:

  

  CRASH references in CRASH3 doc.png (298.94 KiB) Viewed 1186 times

  Many of the listed papers are available online:
  • Please see Over 50 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

[MSI]

Some article related to the 'no damage intercept':

• Why don't you use the A & B Coefficients in mSMAC?
• Does SMAC underreport the impact duration?

[MSI]

Realized we hadn't posted up HOW to calculate the "no damage intercept of crash"
from post on Truck Crush Properties
Here's a quick summary

• be sure to make this calculation for whatever crush coefficients you use!
• For most you will get 4-5 mph "no damage intercept"
• First verify what the 'no damage intercept is' as far as DeltaV and then ALSO deflection.
• "no damage intercept" represents the amount of damage in showroom cars if evaluated with damage analysis
• Keep that in mind...particularly in low speed impacts...when using damage analysis!

we are in the process of a writeup on the process

stay tuned!
Here's data from the Truck coefficients page

Truck A,B No Damage INtercepts.jpg (80.75 KiB) Viewed 864 times

[MSI]

Realized we hadn't included this link related to this forum topic

• HOWTO Calculate CRASH3 A & B Coefficients, AKV (for SMAC)