FEA programs

[nero]

Can anyone give advice as to Finite Element Anaylsis (FEA) programs. I need to engineer the main beam for a 14 meter catamaran. Preferably, something that runs on a Mac.

thanks

[MikeJohns]

I find Strand7 otherwise known as Straus7 to be excellent. There are a few limited freebies that are good highly featured and easy to use such as Cadre Pro. However we use Windows 2000 PC's so you would have to find out from the vendors what runs on what.
PowerPC chips can run nonnative software in emulation mode, not sure what you have.

Herm Bussemaker has written some FEA code and may be worth contacting for help and advice he used to be found at "cobus@csi.com"

[Karsten]

Very common and easy to use is NASTRAN for Windows. This is a program that lets you create the FE model, crunch the numbers and then view the result. It's a bit of a scaled down version from the PATRAN/NASTRAN combination. In this case PATRAN is used to create the model and view the results and NASTRAN is the program that actually crunches the numbers. PATRAN has a few more options to create the numbers and view the results than the NASTRAN for Windows version.

There is another way doing FE- analysis. The better CAD- programs come with a inbuilt FE program these days. Look at ProEngineer. There is a student version that is available for a few hundred bucks and works very well. You don't have to be a student to get it. I got it for some professional devellopment.

If your beams are made from composites it can be quite tricky to come up with the stiffness values for the laminate. You can do the calculations with an excel spreadsheet if you know what you are doing or get a FE- program that does it for you. If you want the FE- program to be able to do it for you make sure it has such an option. Most programs are able to cope with solid laminates but have problems with sandwich laminates.

Not quite sure what the MAC situation is. Most of the programs run on Windows, UNIX or Linux.

Good luck,
Karsten

[nero]

Just a quick thank you for y'alls replies. I will research your suggestions. Mac OSX runs linuix and unix ... because the core of Mac is a unix kernel now.

will post my results soon.

thanks again.

[nero]

What a strange learning experience! Did some searches and looked up what programs you have mentioned. My first reflexion is that there are too many FEA programs. There are several free and old versions available for UNIX/Linux. Downloaded several of these. I am not sure how, but I got several to run under X11 shell. (Amazing since I just dragged and dropped files at random into the window)

Most did not have a GUI. This is not for me. The only one that did, GiD, has a terrible interface. It is supposed to import .dxf files. I have not got that to happen yet.

There is another program Z88, that has a lot of potential. It is supposed to work back and forth with a CAD program. ... If you do it thru command lines. (again not for me)

Not any acceptable results so far.

For the professional programs, sit down when you read the price tags. They make marine design programs look inexpensive! (TouchCAD excluded)
NASTRAN is the standard. (must be great) There are 20 or more flavors of this by many vendors. I have emailed a few and they are working on "acceptable offers" for my one or two time use. Well we'll see.

The other shock to me is that the nurb surfaces created in design, draw, and CAD programs are not very acceptable to FEA programs. Meshing for them is more complicated then model rendering setups. It seems depressing that 3D design out of a modeling/rendering or CAD program does not flow all the way thru to nice rainbow colored models with the yellow and red colored parts describing unacceptable structures zones.

It kinda does for some of the highend FEA programs but the cost is prohibitive for an individual.

Then there is the Mathmatica approach. There is a FEA extention module for this. The price is correct ... if you already own Mathmatica. Not sure it this is has a GUI.

So, I think, I will make some test examples and break them to find out how thick to make things. It would take some of the fun out it, if I was to set out for a cruise knowing my boat could resist anything. smile

Of interest is something called Dr.Beam3D. Does not do shells. But handles space frames in real time. Kind of an educational program.

thanks everybody

[Ilan Voyager]

I have downloaded a few days ago the freeware Structurix ( http://membres.lycos.fr/yannickc/index.html ) and it looks nice with a good GUI. Good manual in PDF. I have no idea of its validity as I have not made any serious calculation with this soft. There are versions for Mac OS classic and X in english.

I would be very cautious of the use of a FEA by a non-specialist of composites. FEA work well with metals and concrete, but with composites you'll need to check and recheck comparing with classic calculations. Composites may be tricky and good data is not easy to find. Thus you have to make some wild guessings.

Life is to short to spend hours trying to import the F....g DXF, to mesh it, reading manuals and arriving to an uncontrolable result.

If the cat is not a racer shaved until the last ounce, FEA will be too long to use and with too many possibilities of big mistakes. I have seen beautiful but very expensive miscalculations even with so called specialists.

So I leave the very detailed FEA calculations to the high tech structural engineers working all day with their programs and having a long experience of the material. I prefer to pay the guy. It's less expensive than a broken boat.

For a cruiser, a classic calculation, with local verifications within the composite, is largely enough. Just a excel sheet...