Small Strain Formulation

Altair Forum User

Hi There,

I am Simulation an AirBag with MONVOL_GAS option with CardImage PresLoadCurve Option with material Rubber and Foam.

At the start a huge ERR% is occurring (-99%). Later some elements are undergone small strain formation with

such message: 

** WARNING ZERO OR NEGATIVE SUB-VOLUME : 3D-ELEMENT ID : 41274
   ELEMENT IS SWITCHED TO SMALL STRAIN OPTION

Later there is a huge drop in time step ( in order of 3.0484E-67) with zero energy error and gradually time step increased and fixed at 1.1377E-06 and simulation running smoothly.

But in animation file the volume of AirBed becomes Zero with gradual increase in pressure.

 

Prop used:

P14Solid

ISOLID: 14 (with 12 run automatically killed due to exceeding energy error limit)

Ismstr: 0 (used 2 with DT/BRICK/CST but same effect)

Icpre: 1

 

Please suggest some modifications.

I would like to share model file through Secure File DropBox if needed.

 

Altair Forum User

Hi Pritam,

Please share the starter and engine out files.

Altair Forum User

Dear George,

I shared the file.

Please review and suggest.  

 

Thanking You.

Altair Forum User

Hi Pritam,

Received the files. Which unit system you are following in this model?

I doubt this error is related with the material parameters. Please check the same.

 

Altair Forum User

Hi George,

Unit System: mm   Mpa    Ton   N

 

I tried with possible alternative options with the material models as per my knowledge.

But couldn't figure out the error.

So seeking for your help.

 

thanking you.

Altair Forum User

Hi Pritam,

This is clearly an issue with the material parameters. I just varied the material curve with the one in the Help Menu of /MAT/LAW69 and the same ran without any issues.

I strongly recommend to recheck the rubber material parameters.

Altair Forum User

Hi george,

The model is running properly without any error

Thanks for your suggestion and support.

 

Thanking You.