FEA - Ansys, can anyone help???

[men0wjv]

Does anyone know any good message boards for Ansys or is anyone a dab hand at the programme that might be able to help?

Regards

Will

 

[pheon]

I have used ANSYS for acoustic transducer design. A very good general forum for ANSYS technical questions is the xansys group on Yahoo.

http://groups.yahoo.com/group/xansys/

What is your specific question?

 

[men0wjv]

Cheers, I'll have a look. I'm trying to model an isolation captive mounting. I'm looking at how rubber cross sections deform and so try and come up with a design that will stop the captive arragement inteferring with the stiffness of the rubber. Our dept has reacently changed all the cpu's to Ansys, but everyone only knows how to use Abacus and the library is being moved so I can't get the manual! FEA is not my strong point and I've been bashing away at this for months. My main problems are trying to apply a series of dynamic displacements and thus draw a force against deflection graph. Any ideas?
Regards

Will

 

[pheon]

If you are a registered ANSYS customer you can access the manuals online. See

http://www.ansys.com/education/resources.htm.

or try

http://www1.ansys.com/customer/content/documentation/60/index.html

Your problem sounds like something an ANSYS expert could put together in a few hours. Do you need to do a non-linear analysis? Have you got a good set of material properties for the rubber? (As with all modeling exercises the data out is only as good as the data in).

I would start by finding the tutorial or verification test case that is closest to what you want and build up from there.





Broad Arrow Acoustics

http://home.attbi.com/~pheon

 

[men0wjv]

Cheers, I'll have a look at them. I've got a feeling I've seen them before, but thanks anyway. There is something in the help called VM201 and it's a rubber cylinder between two steel plates. I've looked at the .dat file which lists in a rather crytic way the processes. However, after trying all day I haven't really got much further than I was already.
I think an expert would find this pretty easy... but I don't want him/her to do it for me... only problem is, that time is so short they might have to. Don't suppose you know any?

Regards

Will

PS: Yep non linear, got some values for rubber, but not sure how good. Any expert suggestions?

 

[pheon]

I don't know anyone that has experience of the non-linear stress analysis. You might contact your ANSYS rep for a recommendation.

I see that you have posted on the ANSYS board here too. You might get some response there. If you are really stuck, I might be able to help.




Broad Arrow Acoustics

http://home.attbi.com/~pheon

 

[WIM32]

men0wjv:
About applying the dynamic displacements part:
If you apply dynamic forces, these would result in (dynamic) displacements and then could be used for plotting.
Dynamic forces may be applied using harmic analysis type, which is a harmonic analysis.

About the plotting part:
Define a path with PATH,NAME,2,,100
Define de position of both points of the line (start and end):
PPATH,1,,-10,0,0
PPATH,2,,10,0,0
Interpollate de results along the defined line:
PDEF,sigx,S,X
Review the results with e.g. PLPATH,... of PRPATH,...


If you have some more info, I may be able to give you more detailed help.
rgrds
Wim

 

[men0wjv]

Thank-you very much for your reply Wim, it was useful. Basically my biggest problem with the graph is getting a force out from a applied displacement. A similar graph is done in VM201.dat, which can be found below:

http://dmt

http://www.epfl.ch/ims/micsys/ANSYS/verif/vm201.dat

The section from it in question is:
"/POST26
/AXLAB,Y,FORCE ! LABEL Y
/AXLAB,X,DISPLACEMENT ! LABEL X
NSOL,2,NCEN,U,Y
RFORCE,3,NCEN,F,Y
PROD,2,2,,,,,,-2
PROD,3,3,,,,,,-2
XVAR,2
PLVAR,3 ! PLOT DISPLACEMENT VS FORCE
PRVAR,2,3 ! PRINT DISPLACEMENT, FORCE"
Could you possibly elaborate on it more?

In terms of the variable displacement, do I apply a diplacement, then set to harmonic Analysis type to make it a sinusoidal displacement? So if I apply 1mm the it varies between 0 and 1mm sinusoidally?

I'm using element Hyper56 and the same values from the .dat file, is this a good approximation of natural rubber?

Where does damping come in to it?

These are my main questions, if you could answer any or direct me in any way I'd be most grateful.

 

[WIM32]

The .dat file is a good start, but the material properties are in someway tuneable, i.e. you may have to try to fit your calculations with an experiment. I'm not familiar with the way the .dat file is set-up, we use a little bit different approach; also I must add that doing non-linear calculations requires quite some experience.

About the displacement:
If you have built your model, then you have to do a modal analysis (antype, modal). This creates a .rfrq file. This file can be used for the harmonic analysis (using hropt, msup)
Then you apply the dynamic force, at this point, the damping also comes into the story.

I think if you use the ansys help file, you should finally find all the answers.
The exact answer to your problem is, I guess, difficult to post here...

Short summary of approach:
- built model using the constants in the .dat file
- Perform modal analysis (important= to have at least ten elements in each mode-shape)
- Perform harmonic analys

I think that the full answer to your problem may be a little to complex to get here...but good luck anyhow
rgrds
Wim



good luck
Wim

 

[srinivasanpuri]

Hello All,

At the moment, Iam using an ANSYS Educational Version
to conduct a Harmonic Acoustic Analysis on
closed cavities (Eg. Simple Rectangular cavity).

I would like to apply a velocity amplitude on pne face of the 2-d rectangular cavity.

I have read through the ANSYS User Guide to perform a harmonic
acoustic analysis, but Iam still not able to apply a 'Velocity
Amplitude' on any face of the cavity (Rather, there seems to be
no options in the GUI to apply a velocity amplitude). #

I would be glad if anyone can help me out


Regards,

Srini