Why don't you use the A & B Coefficients in mSMAC?

Topics related to collision & Trajectory analysis formerly on our 'Registrants only' area however which we get asked about frequently so believe shoud be in the open forum too
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MSI
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Why don't you use the A & B Coefficients in mSMAC?

Post by MSI » Sat Jan 23, 2016 10:50 am

Q: Why do we not input both A and B for the stiffness information? I am sure there is something fundamental to this approach!

A: SMAC dynamically models the loading and unloading of the vehicle structure so the CRASH 'A coefficient' is not needed. Secondly the AKV (crush stiffness input for SMAC) is similar to the CRASH 'B coefficient' however it is generally less since the CRASH 'B coefficient' includes the reduction in crush due to restitution for the given speed(s). The SMAC input AKV is the loading stiffness of the vehicle structure.
  • We currently have a working version of msmac which makes use of CRASH A & B coefficients for automatic calculation of restitution coefficients (we haven’t announced/activated it yet (we have a lot of research going on on various aspects of all our simulation modeling and reconstruction techniques).
The CRASH A & B coefficients represent a ‘virtual crush stiffness’ since the crush and the force do not exist at the same time:
  • The CRASH A & B Coefficients are based on measurements made to damaged vehicle (s) after crash tests at a known impact speed. CRASH equates the impact speed and the residual crush with no consideration for the resitution.
  • The SMAC AKV crush stiffness input is the structural crush stiffness that is observed and measured in crash tests.
    For additional information please see our Review of CRASH Damage Analysis
Please also see Does SMAC underreport the impact duration? for additional information including the HVE EDSMAC4 misuse of CRASH A & B coefficients
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