Damage analysis measurement detail requirements

Questions/Topics related to Damage and Crush Analysis
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MSI
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Joined: Thu Jun 18, 2009 12:37 pm

Damage analysis measurement detail requirements

Post by MSI »

Nov 2020: From June 2020 some posts to the thread Should a CRASH type damage analysis include induced damage? now made separate posts:

Saw a post on Facebook in June 2020 NAPARS page about damage measurement:
damage measurement.png
damage measurement.png (361.26 KiB) Viewed 216 times
  • Measuring Crush.
    • An investigator for NHTSA came to an inspection of this car which experienced a serious frontal impact. He brought a pair of folding music stands, and set them at a common distance from the undamaged rear axle to serve as a reference baseline. He tied a string at bumper height and used tape on the string to flag the locations for his 6 crush measurements (equidistant on the original face, now distorted on the car). Low tech, but also low cost, easily transportable on a plane, highly adjustable, easy to explain, and repeatable enough for the task of measuring crush. He let me take a picture of it. Thanks, NHTSA-guy!
      • (i just browsed down to the page...LOTS of informative posts by Wade on that Facbook thread...here's the specific thread on Facebook to Measuring Crush)
OUR RESPONSE:
  • Love it! I'll take on ANY cloud scan in damage analysis with my plumb bob and ruler! There have been tests/papers on comparing different measurement techniques when applying damage analysis and it all boils down to that a cloud scan for data in crush analysis is like using an electron microscope to measure something to the nearest inch!! what's the point? Whole lotta gigabytes for a crude technique.(yea they sure make purdy looking pictures which has jury appeal!!)

    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 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 as primary reconstruction techniques for individual cases...sure the convenience of ONLY needing to look at the damage.
    Be sure to check Smith/Noga SAE 880072 paper on measurement techniques to accommodate the crudeness of damage analysis addressing things like: what about induced damage, etc.
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