Need help with assemblies in Mechanica

[headrush]

As an experienced FEA analyst (although many years ago) I am very impressed with Mechanica. It is incredibly easy to use and seems to be accurate in spite of it's inherentdesire to make elements the size of Rhode Island.


I am using the integrated version. I have had no formal training in Mechanica, but we have CadTrain. Everytime I try to analyze an assembly it fails. I believe this is because the components are not connected. Being polite, I would say both CadTrain and ProE helpare vague on the subject of connections.


Starting simple, I am under the impression that a rigid connection between two component surfaceswill be made (or surface nodes merged) automatically as long as the two surfaces are of the same size or overlapping. Is this true?


If true, doesthe creation of a rigidconnection depend on the specific type of "mate" used to orient the parts in the assembly model?


Anyhelpwill be greatly appreciated.
Edited by: headrush

 

[Natewebb]

1. Avoid overlapping parts in general. Also avoid packaged components. For component surfaces to connect, they don't need to be the same size, just need to be touching.


2. It's really independent of the type of "mate". The parts just need to touch. This can be done with any type of constraint, for example coordinate system placement would work the same as a mate, assuming same positioning.


3. Regarding rhode island, this is due to the p-element solver. Everbody feels awkward when using mechanica causethey learn on h-codes first. If you have another solver, you can use the FEM mode pre and post processor for h-elements.

As an experienced FEA analyst (although many years ago) I am very impressed with Mechanica. It is incredibly easy to use and seems to be accurate in spite of it's inherentdesire to make elements the size of Rhode Island.


I am using the integrated version. I have had no formal training in Mechanica, but we have CadTrain. Everytime I try to analyze an assembly it fails. I believe this is because the components are not connected. Being polite, I would say both CadTrain and ProE helpare vague on the subject of connections.


Starting simple, I am under the impression that a rigid connection between two component surfaceswill be made (or surface nodes merged) automatically as long as the two surfaces are of the same size or overlapping. Is this true?


If true, doesthe creation of a rigidconnection depend on the specific type of "mate" used to orient the parts in the assembly model?


Anyhelpwill be greatly appreciated.

 

[headrush]

Thanks Nate! Iwas able to geta2 part assembly to run by setting the interface between the two parts to exactly the same size. This is a big step forward. I also discovered the plane cut/display feature in the results window. I can smell success now.

 

[ice_man]

As long as you dont have global intereference in your assemblies, it should work. Not exactly, Pro/M is a little stupid, it will still mesh the assembly if the global intereference volume is very very low, upto three decimal places (0.0002cubic in.)

It doesn't make a rigid connection between two solid surfaces mating. It will make a link element if you have shells and that link element as read somewhere is a rigid connection. (Enough documentation on that is not found yet)

Depending upon your mate, the mesh is gonna behave. You might wanna turn your re-entrant corners off, if you have two plates mated to each other perpendicularly. It doesn't really matter how you mate it, its still gonna mesh, as long as you satisfy the min/max element criteria.

 

[jabbadeus]

Actually, even if the two parts in the assembly aren't touching, as long as each independent body is constrained and loaded, the analysis will work.


Of course, if they are not touching, then there is no way loads, stresses, etc. will be transferred from one component to another.