What is best practice for FEA of assemblies?

Hi

I am rater new to Creo Elements, using release 5 from 2009. On a regular basis, we need to do standard static analysis on welded details, such as the one shown on the screenshot. The heigth is about 360mm and weigth 4.4kg material steel. The item is fixed by bolts in the horizontal plates and load is applied at the boltholes in the vertical plate.

My question is, what is the best practice to build a FEM model based on an assembly?

I have considered the following issues by different methods:

• The design might be changed so a new FEM model i required
• It is nice to have the FEM model for a specific version of the assembly for later reference
• preparing the FEM model from the assembly should be simple and not too time consuming

I have tried and/or considered different approaches:

1. Make a copy of the assembly using the backup option, so that I dont have to work on the original file
   1. In Mechanica, add rigid links so that the parts are connected or
   2. In mechanica add welds  so that the parts are connected
2. Transform the assembly into a part by -File -Save as:
   1. shrink wrap (will often remove too many details)
   2. via IGES
   3. Via SAT
   4. Via Step (I lost the reference between the parts :-( )
3. to remove gaps between welded parts and remove unneeded details i then add
   1. rounds,
   2. chamfers
   3. extrusions
4. Alternativly I could remodel the item as a part so that i get a good base for the FEM from the start.

Especially step 3 and method 4 is time consuming, but I am more sure to get a usable model than when I make calculations on an assembly (1)

Method 1 also has the disadvantage that surface regions cannot be used together with assembly cut, which is a good tool for simplifying (mirroring)

What are your experiences? which method is the best? Did I overlook some smart way of doing it?

I have earlier worked with Inventor where I typically would use schrinkwrap and with SolidWorks, where i often made a shell model based on the original one, but that was in my previous job where i often worked whit large thinwalled vessels.

Best regards
Torkil Bladt, M.Sc. Eng TCA-Lift, Denmark