Determining accelerations/DeltaV for locations other than the CG

General questions on the SMAC, msmac3D and other Collision Simulation programs
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MSI
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Joined: Thu Jun 18, 2009 12:37 pm

Determining accelerations/DeltaV for locations other than the CG

Post by MSI »

Determining accelerations/DeltaV for locations other than the Center of Gravity (CG) When evaluating either measurements made with accelerometers not located at the CG or occupant exposure, we recommend using the msmac3D Tool smacthp to assist in your evaluation.
  • From Help->Getting Started
    • ->Demos and tutorials section
      ->Smacthp with ricsac2
    In the discussion you will see the important items you should consider when evaluating accelerometer or occupant information when not at the CG:
    • Be sure to rerun the msmac3D simulation during the collision with 0.001 output time increment and then you can run:
      • Tools->smacthp
        Select veh1 or veh2
        Indicate an X,Y location
        And start/end times (or use automatic)
      All items are discussed in the Smacthp with ricsac2demo presentation
    smacthp provides a direct way to compare the accelerations/deltaV’s for accelerometers at locations other than the CG
    • And FYI if you don’t know the exact location of either the accelerometer or the occupant you can try different locations and see how much it changes the max acceleration and the deltaV
    smacthp is a great tool to demonstrate the differences in accelerations and deltaV’s due to location
    • It can help demonstrate why occupants (or accelerometers) see different DeltaVs for different locations (and therefore different possible injuries)
      • Different people experience different issues for the SAME accelerations
      • Due to positional differences, the accelerations may be different, so the differences in injuries might be more dramatic.
      • Of course there is a HUGE difference in accelerations/deltaVs in the event an occupant is in the crush zone, link a near side occupant in a side impact, where the deltaV for the occupant can be approaching the closing speed
    And one aside about SMAC:
    • SMAC initially used the threshold of acceleration > 1 G to start DeltaV calculations and once it came back down below 1 G to end the DeltaV calculations.
    • In initial development logic had to be added to handle momentary blips in the acceleration! Etc.
    • Now that we’re working in 3D and we may have to rethink that logic
      • weight transfer after a collision may extend the acceleration > 1 G longer
      • What about the 1G threshold? Might we revisit that and make it lower? Or higher?
    We are in the process of reconsideration of the default thresholds but in the meantime simply use the msmac3D Tool smacthp to consider different thresholds.
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MSI
Site Admin
Posts: 1815
Joined: Thu Jun 18, 2009 12:37 pm

Re: Determining accelerations/DeltaV for locations other than the CG

Post by MSI »

After reading the write-up, a user asked: What does smacthp stand for?

SMAC Time History Program.
Update/Upgrade/Enhance your tools with msmac3D! Lease it, Try it!
LINKS:LEASE pricing!, McHenryForum Index, LATEST TOPICS
Question? Comment? Please email forum@mchenrysoftware.com
(c)McHenry Software ALL Rights Reserved.
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