*CONTACT_AIRBAG_SINGLE_SURFACE

[Akshay Dahiya]

Hi all!

I am looking for insights on defining contact between airbag fabric parts using *CONTACT_AIRBAG_SINGLE_SURFACE. In the figure attached, I am currently running only airbag simulation with an acceleration pulse along x-axis prescribed to the rigid airbag box. As we can see, there are penetrations in the fabric shell elements during the initial motion of the box which later affects how the airbag deploys.

I used the following contact parameters for the simulation:

The airbag thickness curve is provided. The thickness before the deployment time is very less (0.05 mm) as compared to the thickness after the deployment time (0.32 mm).

 

Any help/insight would be highly appreciated.

Thanks,

Akshay.

[James M. Kennedy]

Dear Akshay,

 

Some simple notes I found.

 

For modeling the deployment of airbags the following contact option is recommended:

 

*CONTACT_AIRBAG_SINGLE_SURFACE (a13)

 

With *AIRBAG_SINGLE_SURFACE, contact between nodes and multiple segments is

considered. Much more searching is done than in the normal contact option and, consequently,

this contact option is much more expensive.

 

During the past several years, the soft constraint option, on optional card A, in the contact

definition, set to 2 has proved to deploy airbags very accurately. We currently recommend

this option for airbag deployment. The latter option is currently being implemented for MPP

usage.

 

Standard Penalty-Based or Soft Constraint Stiffness Method

 

When several parts of dissimilar mesh sizes and/or dissimilar material properties are included

into one global slave set for *AUTOMATIC_SINGLE_SURFACE, the soft constraint stiff-

ness method (SOFT=1) is recommended.

 

The following are examples where contact behavior may benefit from use of the soft constraint

method:

 

Airbag to Steering Wheel

Airbag to Occupant

Front Tire to SIL

Spare tire to neighboring components

Foam to structural components

 

Using a combination of both contact stiffness methods may promote good contact behavior

without having to reduce the global time step

 

Sincerely,

James M. Kennedy

KBS2 Inc.

September 7, 2021

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[James M. Kennedy]

p.s.

 

https://www.dynasupport.com/tutorial/contact-modeling-in-ls-dyna/airbag-contact

 

https://www.google.com/search?q=CONTACT_AIRBAG_SINGLE_SURFACE+ls-dyna&oq=CONTACT_AIRBAG_SINGLE_SURFACE+ls-dyna&aqs=chrome..69i57.6348j0j15&sourceid=chrome&ie=UTF-8

 

https://www.scielo.br/j/jatm/a/BH6sdhN4HYf7Ys9vqDyrbvk/?lang=en&format=pdf

Hi all!

--

[Akshay Dahiya]

Thank you James for a

 prompt reply.

You said "The latter option is currently being implemented for MPP usage." Does this mean that SOFT = 2 card can be used only with LSDYNA SMP and not MPP. Is that correct?

[James M. Kennedy]

Dear Akshay,

 

The following note is found in several presentations:

 

If the airbag simulation is run using an MPP executable, note that SOFT=2 is not yet available

and so SOFT=0 or 1 must be used.

 

At the time this note was written (WHO KNOWS WHEN?), SOFT=2 did not work with airbag

simulations using an MPP executable.

 

Please contact your local distributor for better information.

 

Sincerely,

James M. Kennedy

KBS2 Inc.

September 9, 2021

To view this discussion on the web visit https://groups.google.com/d/msgid/ls-dyna2/19f4fecf-1041-4aa9-b158-61ea9ce10e2cn%40googlegroups.com.