Shell structure modeling from 3d step files

[trainguy]

Hi all.

I am curious about what most of you stressed skin (i.e. airframe?) analysts do with regard to producing plate element models from the 3d (non zero skin thickness)data, e.g from a step file.

My current thinking on this is that it is quicker to generate the geometry as native FEMAP emtities such as surfaces, etc. as opposed to importing the step file and midsurfacing, etc.

What do you guys/gals do?

tg

 

[trainguy]

Anyone...?

 

[Onda]

Hi,

I use Patran, not Femap. But I think the process could be the same.
Anyway, Usually I import the model generated from High end 3d Software as SolidWorks or Proe to a non parametric software like Rhinoceros (but I think many others can do same work).
Then:
1- I simplify the solid model deleting fillets and small surfaces and rebuilding the surfaces to have coincident edges.
2- I make the mid surface or I delete the inner/outer skin depending of what I want to model.
3- I extend the frames to the outer/mid surface.
4- I split the surfaces in way of T joint to have coincidents grids.
5- I subdivide the surfaces in differents layers in functions of shell property.
Once the model is ready I export the surfaces as Iges and import to Patran to mesh it.
I work with model up to 200000 elements and hundred of property and the process is straightforward.
More time you spend in the cad system easyer will be your job in Patran (Femap) and better will be the model.
If by the way You have access to a Hypermesh license and you can do the mesh generation in Hypermesh then you have the best way to make your model. The mesh generated by Hypermesh is long way superior on that made by Patran and the process is way much faster.
I never design my model directly in patran except if they are so simple that I spend more time in conversion than in building directly in Patran.

Regards

Onda

 

[rb1957]

i'd bet it's 50/50 (importing a step model or starting from scratch) ... both have pros and cons.

i'd also bet that 1/2 way thru you'd wish you'd've chosen the other !