Airbag Simulation using LS-DYNA: start from filled airbag

  • #1
ArianaFenris
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How do I start my LS-DYNA impact simulation from a filled airbag?
Hello! I'd like to model the impact of an object on an inflated air cushion (effectively an airbag) at rest in LS-DYNA, however all the tutorials I see start from a deflated airbag. I would like to skip this computation if possible to save computing time, since I would have to run the simulation until the bag stops oscillating.

Also, could I place the cushion on a solid surface so that the cushion's deformation is restricted from below?

Can I inflate the cushion to differing fill fractions other than a completely filled bag?

I'm not very familiar with LS-DYNA, any help is much appreciated. Thanks!
 
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  • #2
I'm not familiar with the mechanical simulator LS-DYNA, but for the electrical circuit simulator SPICE (available in various vendor packages), you can set "Initial Conditions" with the .IC command line or though other mechanisms in the GUI interfaces. Does LS-DYNA have anything like that (look in the Help pages)?

Also, another strategy with SPICE is to run one simulation to get to the initial conditions, and save that state to use as the starting state for multiple subsequent simulations. Can you save a state at the end of filling up your airbag?

https://resources.pcb.cadence.com/b...itial-conditions-and-interpreting-the-results
 

FAQ: Airbag Simulation using LS-DYNA: start from filled airbag

How do I set up an initial condition for a filled airbag in LS-DYNA?

To set up an initial condition for a filled airbag in LS-DYNA, you need to define the airbag's initial geometry and internal pressure. This involves using the *INITIAL_VOLUME_FRACTION_GEOMETRY keyword to specify the initial volume and shape of the airbag. Additionally, you must define the initial internal pressure using the *INITIAL_AIRBAG_PRESSURE keyword, which sets the starting pressure inside the airbag.

What material model should I use for simulating the fabric of the airbag?

For simulating the fabric of the airbag, the *MAT_FABRIC material model is commonly used. This model is specifically designed to capture the anisotropic and nonlinear behavior of fabric materials. It allows you to define properties such as tensile and shear strengths, as well as the fabric's response to stretching and folding.

How do I model the interaction between the airbag and the occupant in LS-DYNA?

To model the interaction between the airbag and the occupant, you need to define contact interfaces. The *CONTACT_AUTOMATIC_SURFACE_TO_SURFACE keyword is typically used to define the contact between the airbag surface and the occupant's body. This contact definition ensures that the airbag can interact with the occupant, applying forces and deformations as needed during the simulation.

What are the key parameters to consider when simulating airbag deployment?

Key parameters to consider when simulating airbag deployment include the initial internal pressure of the airbag, the material properties of the airbag fabric, the venting characteristics (if any), and the interaction between the airbag and the surrounding environment or occupants. Additionally, the deployment time and the gas flow characteristics are critical for accurately capturing the dynamics of the airbag inflation process.

How can I validate the results of my airbag simulation in LS-DYNA?

To validate the results of your airbag simulation, you should compare the simulation data with experimental data or real-world crash test results. Key aspects to compare include the airbag deployment time, the pressure distribution within the airbag, the force exerted on the occupant, and the overall deformation and behavior of the airbag. Ensuring that your simulation closely matches experimental observations is crucial for validating its accuracy.

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