Should a CRASH type damage analysis include induced damage?

Questions/Topics Related to the CRASH computer program
#CRASH #EDCRASH #PC-CRASH
MSI
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Should a CRASH type damage analysis include induced damage?

Post by MSI »

2 words of wisdom on CRASH type damage analysis (whatever flavor: EDCRASH, WinCRASH, etc):
  • Be Careful!
In 1988, Tumbus and Smith wrote SAE paper 880072:
  • In the paper they presented some ideas for a standardized protocol to measure damaged vehicles which included special cases like bowing, etc. I recommend the paper for any and all who use damage analysis techniques, whatever flavor of CRASH or damage analysis you use. The standardization of technique is so that anyone measuring a damaged vehicle should produce the same crush measurements.
    For example, in cases of bowing, some extra energy was required to bow the vehicle so the damage measurement protocol should include consideration for the extra energy (or a 'did the vehicle bow?' and 'how much' question should be added and considered in the analysis).
Since publication of the paper there have been some efforts to create a standardized protocol for damage measurement but so far there have been no results.

And note: CRASH was originally created as a preprocessor for SMAC.
  • The mathematical formulation for CRASH is that damage measurements were to be of the direct contact damage only. When NHTSA adopted CRASH damage analysis for the NASS statistical studies they found it was underestimating the DeltaV so they changed the protocol to include the induced damage.
Today, the CRASH clones use the same mathematics and simplifying assumptions as CRASH3 but also include customized crush coefficients. The cottage industry that has grown out of damage analysis has generally continued the use of induced damage in the measurement 'protocol' however remember this is an indication of the limitations of damage analysis.
Be sure to use other techniques such as momentum analysis, simulation, etc. in addition to damage analysis to check and refine your damage analysis results.

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