Newbie Question
Newbie Question
(OP)
I have hardly ever done FE and have a basic question about finite element software, just out of curiosity. We have RISA and RAM Advanse which have finite element capability. But how would these compare to a program like Nastran or Abaqus? I have always heard about these programs...Besides the number of elements available, what makes these programs so much better than RISA or RAM?





RE: Newbie Question
As an example - if you have a bolted joint with 3 bolts, in clearnace holes, in the beam, and six in the column, you can probably specify that for a building FEA in about 3 seconds flat (guessing).
Whereas if we were to analyse it the way we do car structures we'd use an element size of about 1mm and would need a supercomputer, given that you've got clearance holes and contact. There is a joint pretty much like that in a car, some poor bugger's life work is meshing it.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Newbie Question
Fun, but useless, for buildings. Not much fun, but very useful, when we crash cars into barriers.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Newbie Question
Some friends of mine (civil engineers...I mix with a bad crowd :) recently had an issue where they had designed a non-traditional joint in a building and someone questioned the accuracy of their RISA analysis. This building was extremely complicated, but their beam model did a good (and very fast) job of calculating reactions in the beams...shear and moment diagrams, etc. It was, as Greg mentions, the joints that were the area of concern.
In the joints, they had connected several beams by welding "boxes" with multiple faces that lined up to where the beams would come in. I extracted their loads from RISA and modeled the detailed joint using very refined plate elements to get a detailed load path. It showed some issues and how to quickly and easily resolve them.
I love FEA...bit of a fanatic...play with software in my off hours after the children go to bed. NEVER FORGET...it is a tool. Don't bring a rack to dig a hole...don't bring a knife to a gun fight. I support three different packages that, in my opinion, are useful for three different functions. One is very inexpensive with great tools for importing and cleaning up CAD models. One I've used for over a decade...I'm very fast with it and it handles most of the problem types that I may need. The third has very powerful contact algorithms and an explicit solver and runs a good bit more efficiently than most softwares (don't need a supercomputer to run significant contact).
Make sure you know what types of problems your tool can address, and learn the right way to use it to its fullest capabilities. Don't try to use it for something that it isn't designed to do, and make sure you are using it correctly by periodically running a problem that you CAN hand calculate and comparing to your results.
RE: Newbie Question
Also, the non-linear, time-history, analysis features are much more sophisticated. Some programs allow you to define you stress-strain curve for a given material.
ANSYS, ABAQUS, etc... all have capabilities that help you build highly refined models in more automated fashions.
The structural programs like RAM and RISA are more geared toward design (and they do a great job!) with the implementation of code checks and section optimization features. They also have better GUI's imho.
RE: Newbie Question
As a response to the initial question about what makes one better than the other - try triming your fingernails with a bolt cutter or splitting firewood with a scalpel - its about choosing the right tool for the job.
RE: Newbie Question
You wrote that
"The third has very powerful contact algorithms and an explicit solver and runs a good bit more efficiently than most softwares (don't need a supercomputer to run significant contact)."
Could you please mention the name of the code you are using for contact analysis? And, if it is possible please mention what kind of structure you are dealing with?
From my personal experience, doing the contact analysis efficiently is usually a good challenge.
A.A.Y.
RE: Newbie Question
http://www.ampstech.com/ampstech/Asp/Solvers.asp
It's the one on the left.
RE: Newbie Question
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.