LS-Dyna DATABASE_CROSS_SECTION_SET – Incorrect Force Calculation

[Jalaj Maheshwari]

I am trying to simulate an explicit simulation of a frontal car crash using a belted occupant. I've setup *DATABASE_CROSS_SECTION_SET outputs on the seatbelts to calculate the shoulder belt and lap belt forces. For this, I've defined a node set, shell set (for 2D elements of the seatbelt), and a local coordinate system at the cross section. Some of my simulations that have been setup the same way are calculating the seatbelt forces correctly. However, I have a couple of simulations where the force starts at 0, and then jumps to about 13000N within 5 milliseconds, which is unrealistic. Not sure why this is happening because all the setup and contacts are exactly the same between the simulations - only the occupant positioning is different. I've attached plots for what the shoulder and lap belt should look like, and what the error loads look like.

Any help on debugging this would be great!

Thanks!

[James M. Kennedy]

Dear Jalaj,

 

Some general notes on seat belt contact modeling:

 

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Please see the following note:

Yeh, I. , "LS-DYNA Seat Belt Modeling Guideline", June, 2007.

http://www.scribd.com/doc/ 67405039/Seat-Belt-Guideline-1

http://ftp.lstc.com/anonymous/outgoing/jday/SeatBeltGuideline1.pdf

 

Yeh, I. , "LS-DYNA 2D Seat Belt Modeling Guideline", June, 2009.

 

http://ftp.lstc.com/anonymous/outgoing/jday/SeatBelt2DGuideline.pdf

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Kang, S., Chen, C., Guha, S., Paladugu, M., Ramasamv, M.S., Gade, L., and Zhu, F.,

“LS-DYNA Belted Occupant Model", 15th International LS-DYNA Users Conference, Dearborn,

Michigan, June, 2018.

 

https://www.dynalook.com/conferences/15th-international-ls-dyna-conference/occupant-protection/ls-dyna-r-belted-occupant-model

 

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Introduction to Seat Belt Modelling

 

https://www.youtube.com/watch?v=yte6Do91E7A

 

Introduction to Dummy Positioning

 

https://www.youtube.com/watch?v=MewIEzBVSpc

 

Advanced Seatbelt Modelling in Oasys PRIMER

 

https://www.youtube.com/watch?v=dZcpkd4wKxA

 

4 Pt Harness LS-DYNA Files

 

https://wehasem.blogg.se/2022/may/4-pt-harness-ls-dyna-files.html

 

-----------------------------------------------

 

Sincerely,

James M. Kennedy

KBS2 Inc.

June 18, 2022

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