Stress Analysis in CATIA

[NicSte]

I a new to CATIA and just getting my head around stress analysis in catia. Could someone explain the reason behind creating meshes? Can stress analysis be done from a solid model once material has been applied or must it be a surface model?

Any responses will be appreciated

 

[rb1957]

i think CATIA models work from solids.

the mesh creates the points on the structure where FE does it's calcs ... more points, better resolution of the stresses.

the CATIA manual should explain this, and provide references for more explanation.

 

[NicSte]

makes sense, what difference would different meshes makes. is the difference just the amount of points that define the accuracy.

 

[rb1957]

yes ... finer mesh better answers. i think CATIA solves onece with the mesh you define, then again with double the mesh, and checks to see if the answers are the same. but that is my memory of about 10 years ago ...

 

[SWComposites]

"finer mesh better answers" > well, different answers, not necessarily better. And the finer mesh result may be just as wrong as the initial mesh result.

NicStr - if you have no experience/knowledge with finite element analysis (and your question strongly suggests that), then you should not be using the stress analysis in CATIA or anything else. Get proper training, and hopefully get someone local there to mentor you.

 

[NicSte]

Thanks for the replies. i am going to work with a "pro" tomorrow, i was just spending time on it today and wanted to get the basics down.

 

[ESPcomposites]

The real training is to learn to be a structural analysis, which is a long term goal (years). Learning how to use the software is relatively simple (weeks).

Your overall capability will only be as good as your ability to provide the correct input, understand, interpret, and correlate the results from the FEM. Most (all) people who are good at FEM have a solid background with the various element types with a standard FEM solution (beyond solid meshing of a CAD model). They are also qualified analysts.

There are many people who believe that you should not touch a FEM unless you are a qualified structural analyst. Otherwise, the likely GIGO scenario is expected. Though I won't go that far, it is hard to argue with that mentality when you see the rampant poor use/abuse of FEM...especially when it comes to CAD based FEM.


Brian

http://www.espcomposites.com

 

[dwallace1971]

Integrating FEA tools into CAD software is having the undesirable effect of encouraging people to think that anyone who can drive CAD can conduct stress analysis. These "black box" tools lull the ignorant into believing that just because they've built a pretty model, and gotten out pretty plots that they've conducted a stress analysis.

 

[rb1957]

"forgive them, for they know not what they do"

 

[GregLocock]

Incidentally I could add the same comment with physical testing. It takes years to learn to reliably measure real things accurately. Anyone who is running FEA who doesn't have real data to correlate with is kidding themselves, their customers and the authorities. In practice I find that roughly 75% of the time the test is right, the FEA is wrong, worryingly 25% of the time it is the other way round.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[AtlanticCoast]

NicSte,

The CATIA FEM utilities support both solid and surface meshes, as well as beam elements. What options are available depends on your licensing. You may be limited to only solid tet meshes. Which type of mesh is appropriate depends on many factors such as geometry.

I highly recommend you become familiar with the CATIA FEM tools if you have the opportunity to work with an experienced stress analyst. It really is a great utility.

Good luck.

John

http://www.AtlanticCoastAerospace.com