Applying SOLID285 in Workbench

[livna]

Hi all,

I have a mesh of 4-node tet elements which ANSYS automatically uses SOLID185 for. I have tried using the command "et,1,285" but I keep getting this error;

*** ERROR *** CP = 3.198 TIME= 18:01:58
Element type 1 is not the same shape as SOLID285. Switching to a
different shape is not allowed while elements of type 1 exist.

I don't understand this error, I know I have tetrahedral elements with no mid-side nodes so how can they not be the same shape? How do I get it to use SOLID285? (The only way I have found so far is to use non-linear adaptivity but that stops my simulation from converging) Any help would be fantastic, this has been driving me crazy for weeks.

 

[Dave442]

I haven't used ansys in some time - but are you sure you have 4 node tets and not degenerated tets? From the documentation:

SOLID185 is used for the three-dimensional modeling of solid structures. The element is defined by eight nodes having three degrees of freedom at each node: translations in the nodal x, y, and z directions. All elements must have eight nodes. Degenerated triangular prism elements may be formed from eight-noded 3-D solid elements by defining duplicate node numbers for the third and fourth (K and L) and the seventh and eighth (O and P) node locations. A degenerated tetrahedral element may also be formed from a triangular prism element by a further condensation of face 6 to a point.

 

[livna]

How would I check?
I've made them my using a mesh control, I selected tetrahedrons for method with patch conforming algorithm and I've dropped midside nodes?
There's a different mesh too that I'm importing from matlab that is definitely tetrahedral and I even save it as a prep7 command which specifies SOLID285 and workbench still converts it to SOLID185 and gives me that same error if I try the "et,1,285" command.

 

[macieksl]

Hi,

Try insert command "et,matid,285".

EDIT:
In workbench you dont have to write anything to matid if you are inserting commands into geometry. It works for me if I have to switch to rigid beams (184) of a line body.

Regards,
Maciej.

 

[livna]

Hi,

Thanks but I have tried that before and it didn't work.
I have accidentally managed to get it to use 285 by using a hyperelastic material model as opposed to a normal hookean. Not sure why this would make a difference though.