Magnification Factor v Energy Corection Factor

General Questions related to the CRASH Program and clones
Damage Analysis & Momentum Based Analysis programs
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MSI
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Joined: Thu Jun 18, 2009 12:37 pm

Magnification Factor v Energy Corection Factor

Post by MSI » Mon Oct 22, 2012 11:16 am

Q: October 21, 2012: If you have a moment can you help me understand angle theta reference the crush magnification factor (1 + tangent theta2)? For example, if my PDOF is 150-degrees (right, passenger side) would the magnification factor theta be tangent 30? (Example: 150-90=60 degrees and since 60 is larger than 45-degrees, subtract it from 90-degrees resulting in 30). I can think fine out to a PDOF of 135 because that does exceed a 45-degree theta (which I know we can’t exceed the limit of magnification factor of 2). But what about theta angles greater than 45-degrees?

A: The 'Magnification Factor' and 'Theta' angle apparently are from Daily book 'Fundamentals of Traffic Crash Reconstruction'.
For some reason Daily changed
  • 'Energy Correction factor' from the CRASH program to 'Magnification factor'
  • The angle Alpha from CRASH to Theta.
No biggie except this can add to confusion surrounding such questions since one would have to know that these are the same terms and that Daily merely changed them from the 1970's CRASH related documentation by Raymond R McHenry The inquiry seems to be simply a request for the definition of the angle alpha (which is called 'theta' by Daily).
Further information:
Question? Comment? Please email forum@mchenrysoftware.com. Also see the McHenry Forum Index
Visit McHenrySoftware.com for technical information & software.
(c) McHenry Software, Inc ALL Rights Reserved.

MSI
Site Admin
Posts: 1311
Joined: Thu Jun 18, 2009 12:37 pm

Re: Magnification Factor v Energy Corection Factor (ECF)

Post by MSI » Thu Oct 25, 2012 3:53 pm

Q: Thanks for the reply. I appreciate all the information posted on your website. If I read the ECF information correctly, there is no limit on the Alpha angle. However, the maximum ECF is limited to 2.0. So if the angle produces an ECF greater than 2.0, use 2.0 in the crush formula. I believe I understand this means to use “2” (max) if the alpha angle relative to the vehicle surface is equal to or greater than 45-degrees. Correct? Trying to make sense as there seems to be a difference.

A: Yes, the ECF is limited to 2 for maximum correction factor. The value of 2.0 is somewhat arbitrary 'maximum' and we have published some additional discussion on the whole ‘ECF’ concept however I don’t currently have that handy while on the road. I will try to remember to post once i return to the office (please rattle my cage if i don't!).
Since CRASH3 is the generally accepted technique and on which most, if not all, Damage Analysis techniques are based, I’d suggest you familiarize yourself with the concepts of CRASH3.
I believe Daily in his book is merely presenting the CRASH3 formulation with slightly different nomenclature. If he presents something different let me know (currently I do not have his book with me)
On a related topic, if you are working with Damage Analysis we recently covered a related topic on our forum, which also refers to the book by Daily:
Question? Comment? Please email forum@mchenrysoftware.com. Also see the McHenry Forum Index
Visit McHenrySoftware.com for technical information & software.
(c) McHenry Software, Inc ALL Rights Reserved.

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