FEA: Pro/Mechanica versus Nastran

[PaulMailloux]

Hello everyone

I am about to start and investigation on FEA software and was wondering
which package is best; Pro/Mechanica or Nastran's package, or any other
package for that matter. At NyproMold, we design and build injection
molds and often require FEA to understand stresses and loads applied on
steel components during the injection cycle and mold closing.

I was at the PTC/User Conference and was impressed with the Nastran
package, however I have very little knowledge of FEA (only
knowledgeable in CFD) and was hoping for some input from all those
experienced users out there.

I would appreciate any input in regards to;

* Accuracy of results

* Comparison of capabilities

* Ease of meshing

* Cost comparisons

* Learning curve

* Ease of use

* Quality and availability of technical support

* And anything else that I may be missing, I'm sure there's more.



Thanks in advance

Paul





Paul Mailloux

Cad/Cam Applications Engineer

NyproMold Inc

144 Pleasant Street

Clinton MA 01510

Phone: (978) 368 - 4598

Fax: (978) 365 - 4548



www.NyproMold.com ____________________________________________________________________________________________________...



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[mjenkins]

I think the big advantage of Mechanica is that you can do optimization studies to say:

What must these 20 dimensions be to achieve this level of stress and then it will automatically change

the part for you and run the study. Other non-native packages must do some kind of geometry import,

set up the conditions run the study and then you must manually go back and change the proe model

for another iteration.

That being said, I like ANSYS.

[JonathanHodgson]

I can't help feeling that this has been covered before, but...

- Accuracy of results in both packages depends on the user. Both can
produce reliable numbers if the model is set up correctly.

- Mechanica has an upper size / complexity limit, due to memory.
Nastran will just keep on grinding, using bigger and bigger swap files,
no matter what (even if it takes days).

- Ease of meshing: Mechanica wins hands-down. The meshing is completely
automatic - although see the above point about accuracy, and my
footnote.

- The learning curve is shallower to begin with in Mechanica, but gets
steep as you get into complex models, or ones where you need to start
using mesh controls and the like to achieve the accuracy. Nastran takes
more learning initially, but then you're more or less set up for
everything.

- Mechanica's biggest asset is seamless integration with Pro/E. Once
you've attached loads and constraints to your model, you can alter
parameters (and even geometry) as much as you like, and just re-run the
analysis.
Other than that, Mechanica is generally quicker to use, certainly for
simple models, although for analyses with multiple load cases the
ability to edit the load deck for Nastran is nice. On occasion I've
imported IGES files into Pro/E to analyse using Mechanica, because it
seemed like the easiest way.


With either package, be aware that you really need an understanding of
FEA principles to guarantee reliable, accurate results. The biggest
risk with Mechanica is probably that it's too easy, and too automated -
users can get complacent, and trust the results without checking
carefully. Nastran is probably better for training up good users...

This should probably be on the proecae list, btw - I've cross-posted to
there, and future replies should ideally be trimmed to that list only.

HTH,
Jonathan

[iceblink1]

What I miss in this list is that Mechanica is limited in a number of ways, for instance in contact behaviour and non-linear materials. If you plan on using such features, Mechanica isn't really an option.

And finally: as far as I know Nastran is a lot more expensive than Mechanica, this might also be an important consideration in your choice.

Best regards,

Patrick Asselman

---- "Hodgson schreef:
> I can't help feeling that this has been covered before, but...
>
> - Accuracy of results in both packages depends on the user. Both can
> produce reliable numbers if the model is set up correctly.
>
> - Mechanica has an upper size / complexity limit, due to memory.
> Nastran will just keep on grinding, using bigger and bigger swap files,
> no matter what (even if it takes days).
>
> - Ease of meshing: Mechanica wins hands-down. The meshing is completely
> automatic - although see the above point about accuracy, and my
> footnote.
>
> - The learning curve is shallower to begin with in Mechanica, but gets
> steep as you get into complex models, or ones where you need to start
> using mesh controls and the like to achieve the accuracy. Nastran takes
> more learning initially, but then you're more or less set up for
> everything.
>
> - Mechanica's biggest asset is seamless integration with Pro/E. Once
> you've attached loads and constraints to your model, you can alter
> parameters (and even geometry) as much as you like, and just re-run the
> analysis.
> Other than that, Mechanica is generally quicker to use, certainly for
> simple models, although for analyses with multiple load cases the
> ability to edit the load deck for Nastran is nice. On occasion I've
> imported IGES files into Pro/E to analyse using Mechanica, because it
> seemed like the easiest way.
>
>
> With either package, be aware that you really need an understanding of
> FEA principles to guarantee reliable, accurate results. The biggest
> risk with Mechanica is probably that it's too easy, and too automated -
> users can get complacent, and trust the results without checking
> carefully. Nastran is probably better for training up good users...
>
> This should probably be on the proecae list, btw - I've cross-posted to
> there, and future replies should ideally be trimmed to that list only.
>
> HTH,
> Jonathan
>
>
>