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Modelling inflated body

Altair Forum User

Sir,

I need an inflated airbag model without showing the deployment. It should have the material properties and property card similar to airbag but the infation should be constant. So can I use monvol-gas for the same purpose. Or is it incorrect to use airbag material and properties without defining the injectors,Vents and mass flow curves

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Radioss

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Altair Forum User

Hi,

You can do with /MONVOL/GAS for this purpose.

Please refer the below video training in which monitored volume is covered (Chapter 5)

https://www.youtube.com/watch?v=kCSRFss6GDE&list=PLQ7KUGFuVz4u5y3SvIEIU07427-gATaG6&index=5&t=0s

Altair Forum User

Sir,

My airbag material is not withstanding the impact force. I beleive I have to move to rubber based material or a foam material that is inflatable since airbag fabric is not withstanding the impact. Sir do you have any suggestion other than fabrics for inflatable structures for eg.rubber or even foam. I have attached the failure of my airbag fabric

Sir Im also attaching the engine out file for the airbag failed model

When I used rubber also I am getting a similar type of failure using mat42

Unable to find an attachment - read this blog

Altair Forum User

Hi,

From the .avi it seems like some modelling issue.

For this impact absorption you can model it with foam material. Do you have all the parameters for Ogden material law (/MAT/LAW42)?.

You can try with /MAT/LAW70, which is a simple material model for visco-elastic foam tabulated material. User should have the loading curve for the same so that the proper behavior can be simulated. Please note that this law is compatible with solid elements only.

A sample foam material model is attached along, please go through it so that you will understand the concept.

Unable to find an attachment - read this blog

Altair Forum User

Hi sir,

Currently I dont have all properties of OGDEN material. I was completely focussed on airbags till now, sadly its not working. Today I did try a simulation with foam also using the below attached curve. But the results were not satisfactory. One doubt I have is whether the curve is to be converted to true stress strain as the curve below

is a result of experiment and one more doubt is that should I only give loading curve? Last doubt is that Can I justify a foam as inflatable?(Im really sorry to shower you with such doubts)

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Hi,

Regarding hyper-elastic materials you can use either /MAT/LAW42 or /MAT/LAW69. For /MAT/LAW42 you should have all the material inputs (like material exponents, shear hyperelastic modulus...etc) whereas for Law69 user has to directly input the engineering stress-strain curve and material parameters like above are automatically computed by the solver. Comparatively modelling using Law69 is easy as you have the curve. Ya one loading curve is fine, the material will behave accordingly.

Please go through https://altairuniversity.com/learning-library/radioss-door-small-example/ which is a door slam example (model file is available at this link) where we have modeled a joint with similar approach, a monitored volume is defined and the material used is rubber (Law42).