Fatigue analysis used ANSYS Workbench 2

[Chaabain]

Hello everybody,

I'm a newbie user of ANSYS Workbench. I must do a fatigue analysis of three piezoelectric ceramics placed between two plates. The lower plate is fixed in all DOF and the upper plate has the possibility to move up/down and forward/backword and there is a force applied on the upper surface of this plate. What is the best way to do this analysis using ANSYS Workbench. Anybody can help°, please?

°: Even by giving me some manual or book to read about Fatigue Analysis.


Best Regards,
Chaabain

 

[Chaabain]

Hi Again,

No reply yet?

 

[Chaabain]

OK thanks anyway ...

 

[kellnerp]

You would start by figuring out how many cycles of each intensity of force were applied to your device.

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[Chaabain]

Hi Kellnerp,

First of all, I would like to thank you for your reply. I have a time-varying load that I would like to apply 5e+6 times on my device. The problem after I've done the simulation with ANSYS Workbench, I got this message:
"An error occurred inside the FATIGUE module: Missing stress life curve"

and I don't know how to get this problem solved.

Thank you in advance if you have any solution.

 

[kellnerp]

Do you have fatigue curves for the material you are analyzing? It doesn't sound like a common material.

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[Chaabain]

I have used the materials provided by ANSYS Engineering data such as Titanium alloy and aluminum alloy and I suppose that the stress life curves for these materials are given.

 

[kellnerp]

Did you check that the data is there and that it is correct for the alloys you are using?

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[cvan42]

Chaabain,
The fatigue module needs fatigue data for each material. You could use the standard aluminum and steel, but these will not be even close to the ceramics you are talking about.
We're in biomed and working on fatigue of nitinol filter wires during vena cava cycles, and we had a contract P.E. run a study for us. The word is nitinol (possibly your ceramics as well) need strain based fatigue vs. stress based, so I don't believe Goodman will work.
Aside from all this, you will probably need to tell your supervisors about getting actual fatigue data of your material from 3rd party testing. We have a couple of Bose machines doing fatigue, and usually they are run for about a month at 1000 Hz to get the data. If your company is like ours, they just wrote the check on the fatigue module and expect a report in two weeks.
So I'd recommend doing some research on the type of fatigue curve you will be modeling (stress or strain), find a 3rd party company to test your samples. Also, we use PADT Inc. for support, and they have a biomed division. Just ask for Ted Harris.
Hope this helps.

 

[Chaabain]

Dear cvan42,

Thank you a lot for your reply. All what you have said is very valuable for me and helps a lot. Actually I don't have this data for my ceramics and I think that I'll do as you have said. But to verify the source of error I've replaced this material by another that exists in ANSYS Engineering Data. However, I got the same error. The fatigue type I would like to model is Stress Life. Anyway, I'll do some research and if I get any solution, I'll back to close the discussion. By the way, is it possible to get such data for free?

Finally, I would like to thank Kellnerp and Cvan42 for their valuable help.

Thank you in advance for any further information

 

[cvan42]

You could look for published papers online, most places you'll have to pay a small fee to get the pdf. Also, if you're still connected with your university, ask around with the professors and such, although a lot of biomed is on Abaqus. Just go through the help files to find out what data you'll need for each fatigue model.

Plus, if your company bought the seat, you could go to the ANSYS website and download all the manuals.

Good luck.

 

[Chaabain]

Hi cvan42,

We have a license ANSYS Workbench for the whole laboratory where I work and all my colleagues try to learn this software for biomedical applications and concerning the university, we never used this program because it costes a lot but concerning the data, I may ask about that. Anyway, I'm trying to learn and work alone. That's why I posted a lot of threads through this forum and I'm sorry for all these (sometimes stupid) questions.

Finally, thank you cvan42 for your help.

Chaabain