Negative volume and complex speed of sound termination
Negative volume and complex speed of sound termination
(OP)
Hello everyone!
I have a problem to simulate an impact onto soil ground (Material Model 5 Soild and Foam) with LS-Dyna, because I am getting negative volumes which lead to complex speed of sound in the material.
My model consists of two layer of soil (Automatic_Surface_To_Surface) and an round impactor. Does anyone have any advice how to solve this problem?
What I tried so far:
- Reduce the timestep scale factor to 0.67 --> no change
- Improve the hourglas formulation (I used type 2,3 and 5) --> same problem, but later error termination.
I am glad for any help and advices!
Greetings
Ed93
I have a problem to simulate an impact onto soil ground (Material Model 5 Soild and Foam) with LS-Dyna, because I am getting negative volumes which lead to complex speed of sound in the material.
My model consists of two layer of soil (Automatic_Surface_To_Surface) and an round impactor. Does anyone have any advice how to solve this problem?
What I tried so far:
- Reduce the timestep scale factor to 0.67 --> no change
- Improve the hourglas formulation (I used type 2,3 and 5) --> same problem, but later error termination.
I am glad for any help and advices!
Greetings
Ed93





RE: Negative volume and complex speed of sound termination
- Identify the region where elements are turning inside out -> can you improve the mesh in that region to prevent the issue?
- If not, then you could look into 'adaptive re-meshing' to try to avoid this.
RE: Negative volume and complex speed of sound termination
RE: Negative volume and complex speed of sound termination
This would also make sense for impact studies on soft foam materials.
RE: Negative volume and complex speed of sound termination
RE: Negative volume and complex speed of sound termination
thanks for your answers!
Normaly negative volumes in foams are caused by massive compression. In my case the compression was not that big, so I have been looking for another reason and solved it by enlarging the mesh of the second soil. I think the problem was the contact between the two soils. The nodes where directly above each other and maybe some errors accured cause I used a nodes to surface contact. Now everything works fine, because I have now a little offset between the nodes.
Thanks again for your help and fast replies!