Some EDRs have max accel limits, msmac3D can mimic that for direct comparison

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MSI
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Some EDRs have max accel limits, msmac3D can mimic that for direct comparison

Post by MSI »

A new option has been added to msmac3D to permit evaluation of crashes and calculations of Impact Speed Change with the Option to limit the maximum amount of acceleration recorded by the EDR aka accelerometer.
Here's why:
  • In some recent investigations and articles some issues have occurred due to a 50g (or other) limit in some EDRs.
    As an example, from the 2021 NAPARS Crash test2 of a head-on collision between a 6973 lb 2003 GMV Savana Van at 34 MPH into a 2946 lb 1999 Pontiac Grand Am at 68 MPH.
    The EDR traces for the Grand Am definitely showed the limit in the traces which affects the Impact Speed Change/DeltaV calulations.
    ACM limit Napars 2021 crash2 GrandAM.jpg
    ACM limit Napars 2021 crash2 GrandAM.jpg (272.83 KiB) Viewed 445 times
    And the DeltaV for the Savana Van was lost (EDR issues)
    so how to resolve?
    (and note they also had 1300 lbs of sand in the van to see the effects of a 'secondary impact' as the sand bags ruptured etc, more on that later)
    Running the crash with msmac3D produced the following results:
    Prelim msmac3D Results NAPARS 2021 Crash2.jpg
    Prelim msmac3D Results NAPARS 2021 Crash2.jpg (142.72 KiB) Viewed 456 times
    The option we added was for the post processing calculations of DeltaV at CG and/or any locations on the vehicle
    we NOW have added the ability to limit the maximum acceleration used in the DeltaV caluclation.
    When you run smacthp it now has an option limit:
    smacthp inputs.png
    smacthp inputs.png (90.44 KiB) Viewed 456 times
    And running for with and without a 50 G limit you see the difference:
    smacthp comparison DeltaV.png
    smacthp comparison DeltaV.png (337.81 KiB) Viewed 452 times
    And the following are the msmac3D acceleration time histories with and without the limit
    • and note, the limit is ONLY for post processing purposes since although the EDR is limited, the vehicle is THE SAME!!
    time hostories accel and deltav with and wo EDR limit.png
    time hostories accel and deltav with and wo EDR limit.png (87.44 KiB) Viewed 456 times

More to come, stay tuned!
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MSI
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Posts: 1922
Joined: Thu Jun 18, 2009 12:37 pm

Re: msmac3D Option to mimic EDRs with max accel limits in DeltaV calcs

Post by MSI »

Here is a direct comparison of a digitized acceleration measurements from the tests and the msmac3D simulation with and without 50 g limit.
  • I did a quick digitixze of the image from the NAPARS presentation as don't have the raw data,
  • i used Digitizeit: great tool been using for years!
It appears that the 50 g limit is really 53.5 gs per the digitization...we will revisit soon.
Direct Compare msmac3D and accel data.png
Direct Compare msmac3D and accel data.png (12.85 KiB) Viewed 429 times
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MSI
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Posts: 1922
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Re: msmac3D Option to mimic EDRs with max accel limits in DeltaV calcs

Post by MSI »

OK since instantly can address
here's comparison with EDR 53.5 g-unit limit
time hostories accel and deltav with and wo EDR 53.5 limit.png
time hostories accel and deltav with and wo EDR 53.5 limit.png (11.26 KiB) Viewed 430 times
and a summary
msmac3D DeltaV summary w EDR 53.5 g unit limit.png
msmac3D DeltaV summary w EDR 53.5 g unit limit.png (13.01 KiB) Viewed 430 times
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MSI
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Posts: 1922
Joined: Thu Jun 18, 2009 12:37 pm

Re: Some EDRs have max accel limits, msmac3D can mimic that for direct comparison

Post by MSI »

We've modified the output slightly to indicate If the max acceleration option was used.
  • Here's the complete output page from smacthp program with explanation of the various outputs.
    • note arrows added to figure below but not a part of the normal output
smacthp output with EDR max limit.png
smacthp output with EDR max limit.png (63.83 KiB) Viewed 343 times
Update/Upgrade/Enhance your tools with msmac3D! Lease it, Try it!
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