CRASH Damage Analysis Estimations at Higher DeltaVs?

[MSI]

Q: I am attempting to determine what research exists into how the CRASH algorithm may/may not overestimate DV at higher levels (i.e. 75mph).

• In my research I have found
  • 1982 DOT HS 806 152 Accuracy & Sensitivity of CRASH by Smith and Noga which appears to show good correlation in the mid 60's DV.
  • However, SAE 870045 Overview of the way [url=https://www.mchenrysoftware.com/board/viewtopic.php?t=585]CRASH/EDCRASH Computes DeltaV[/url] (Day and Hargens) states :
    • "it (CRASH) overestimates the Delta V for major crashes (delta-V greater than 50mph" (no reference given).
  • I have also found SAE 890738 Application & Misapplication of Computer Programs for Accident Reconstruction (also Day and Hargens) which states that
    • Delta V outside of 10-40 mph "may be suspect" (no reference given).
    I have put far more effort than I can reasonably bill to find testing on this matter. If possible, I would greatly appreciate any reference you may be aware of.
    

A: One of the papers you cite, SAE 890738, states the following referring to CRASH (and also IMPAC):

• "These programs are best-suited for studying collisions in the tested range for DeltaV, approximately 10-40 mph. Results outside this range may be suspect
  • And i expect WHY they stated "10-40 mph" that is because CRASH (and IMPAC) virtual damage analysis are based on full-scale crash tests, and the coefficients for these programs are based on generally the following:
    • a single crash test at 35-40 MPH and
    • an assumption for the 'no residual damage intercept' of 4-5 MPH.
      And most crash tests (NCAP) are at around 35-40 MPH
      sooooooo....
      10 mph is (maybe?) in recognition of the 'no residual damage threshold were at 8-10 mph with no damage!
      
      • See SAE 88-0223 Elastic Properties of Selected Vehicles by Navin, MacNabb & Miyasaki )
      • Also see our 1997 SAE paper
        • The Effects of Restitution in the Application of Crush Coefficients

Look through the many topics in the Damage Analysis, CRASH forum topic.

• First you will note that we have a topic related to your question, see:
  • Damage Analysis for High Speed Impacts?
  and then also please note from our topic
  • More Questions on CRASH: Accuracy, DeltaV
  and
  • Damage analysis measurement detail requirements
    Which includes:
    
    • CRASH (on which all damage analyses techniques are based) was invented by Ray McHenry as a quick/fast way to get starting speeds for NHTSA to start a SMAC analysis!
      • ...and yea, NHTSA decided crude was OK and good enough for their NASS statistical studies mainly because they simply wanted/needed uniform interpretation of crash evidence for their NASS statistical studies so they could look for trends, etc. etc.
        • See our many papers on CRASH
        ...now fast forward 40+ years and software vendors and others peddle CRASH and CRASH clones, using ONLY damage analysis, as a primary reconstruction technique for individual cases!!...sure the convenience of ONLY needing to look at the damage...
        • and let us importantly add...
          • many 'instantaneous momentum exchange' analysis program vendors now try to bolster their results by including damage analysis results.
            • Please exercise caution when using these (or ANY) techniques for crash reconstruction.
            • Be sure to perform sensitivity tests on any results. See:
              • The Major Shortcoming of Simplified Momentum Simulation and Analysis
      Be sure to also check Smith/Noga SAE 880072 paper on measurement techniques to accommodate the crudeness of damage analysis addressing things like: what about induced damage, etc.

Please let use know if any additional questions.


___________________________________________________
For additional information, 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?
  • Crush Coefficients Conversions: CRASH (McHenry), Campbell, WinSMASH (Prasad)
    ..and more, see the McHenry Forum and specifically the McHenry Forum topic CRASH and Damage Analysis