EDR MAX Accel Limits: msmac3D can mimic for direct comparison

[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 (272.83 KiB) Viewed 2509 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 (142.72 KiB) Viewed 2520 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 (90.44 KiB) Viewed 2520 times

  And running for with and without a 50 G limit you see the difference:

  

  smacthp comparison DeltaV.png (337.81 KiB) Viewed 2516 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 (87.44 KiB) Viewed 2520 times

More to come, stay tuned!

[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 (12.85 KiB) Viewed 2493 times

[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 (11.26 KiB) Viewed 2494 times

and a summary

msmac3D DeltaV summary w EDR 53.5 g unit limit.png (13.01 KiB) Viewed 2494 times

[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 (63.83 KiB) Viewed 2407 times

[MSI]

changed the title since find it is needed in many crashes
the 50G limit makes the output for deltaV from EDRs less than actual.
Be sure to see

• 109 MPH Crash, Collision Magazine Article, msmac3D Recon

where we investigate the effects of the 50G (or other) limits of EDR