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Blast Simulation

Altair Forum User

Dear community

I have to run blast simulations.

I use the Eulerian Lagrange Approach with material Law51, Iform 11. (Drucker Prager yield surface used to model soil)

The FS-Interaction is modelled by contact type 18.

I got the failure: id 167 negative rho.

How do I avoid this error?

Where do I find deeper explanations about the contact type18 and the material law51?

Is there a bench mark or example regarding detonation in soil with interface to structure?

Thanks in advance for sharing experiences.

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Altair Forum User

Hi Kellkai,

Can you share the .out files of the simulation. Please check the interface created in the model.

More details on materials and contact type can be found in the Theory Manual of RADIOSS which can be accessed from the Help Menu.

You can find the examples Example 46 - TNT Cylinder Expansion Test and Example 50 - INIVOL and Fluid Structure Interaction (Drop Container) in Help menu.

Altair Forum User

Hi George,

I checked the example. Also I checked the help menu. These do not give an idea about what might be wrong and how can I avoid the error neg. roh.

I went now to the local distributer to get help.

May you have a general idea about this or some more information?

Thanks in advance.

Altair Forum User

Hi Kellkai,

Can you share the files (_0000.rad,0001.rad,_0000.out and _0001.out files) to my drop box.

Altair Forum User

I changed the parameter for the boundary condition to : law 51; Iform=3; Iopt=1 and it worked regarding neg. rho.

Do not know why.

The impulse and energy which is transferred to the structure is very depending on the contact type18 parameters.

The manual gives some ideas about modeling the parameter.

May there is a common understanding for improving the transport to the structure by type 18.

Altair Forum User

Hi Kellkai,

The ALE Multi-Material formulation is a method allowing the finite element mesh to move independently from the material flow and where each element in the mesh can contain a mixture of two or more different materials. In ALE approach, after moving the mesh, a remapping of state variables to the new mesh locations is performed. (Iform 3 formulation handles outlet conditions for Multi-Material ALE domain).

Negative volume error happens when solid elements are very deformed and their characteristic length goes to 0. This can be avoided by switching to small strain.