Learning Forum

[steigerjun]

Hi, everyone. I would like to ask a question about the setting control volume in the keyword Simple_airbag_model. There is a shell box and a solid box in my model(They have similar Elastic modulus). The solid box is smaller and inside the shell box. What I want to do is:
(1) apply gas into the space between the shell box and solid box
(2) apply thermal expansion on the solid box==> to check the influence of solid thermal expansion on the gas and shell box
However, I don't know how to set the space between the shell box and solid box as the closed control volume. I tried the segment which combined both solid and shell box surface, but the result was not correct. Can anyone help me with the problem? Thank you so much in advance!
 

[Alex R.]

Hi, 

1) The airbag needs to be defined using a single *SET_SEGMENT containing shell part and outer surface of the solid box. The normal vectors of this segment should be facing outwards from the AIRBAG. Please look at this similar problem containing a sphere in a cylinder. The sphere normals are pointing to the center while the cylinder normals are pointing outwards. The control volume of the airbag will be between the cylinder and sphere.

2) The thermal expansion (no heat transfer between the structure and the airbag) can be added using *MAT_ADD_THERMAL_EXPANSION and *LOAD_THERMAL_LOAD_CURVE. Please see the example https://www.dynaexamples.com/thermal/thermal-expansion/thermal-load

Please let us know how it goes,
Thank you,

Alex