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composite failure index

Altair Forum User

Hello,

for my model, the composite failure index is around 0.6 but plys with maximum FI varies from 10 in some places to 1.

Does that mean my model/structure composite will fail.As far I know if the composite failure index is <1 then the composite should not fail.

Just a bit worried about the ply(s) with maximum FI.

could someone help me with this.

Thanking you in advance.

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Altair Forum User

Hi Sritej,

can you output Strength Ratio instead and check the values?

Use PARAM,SRCOMPS,YES to output strength ratios. If SR is less than one then this indicates failure.

Altair Forum User

I did try out what you said above.

But for a particular case my composite failure index is 7.98(which should be actually less than <1 to avoid failure) and my composite strength ratio is 28.17(greater than 1 in order to avoid failure).

What does this indicate?

if we go with the composite failure index the model is failing but at the same time if we go with the composite strength ration the model doesn't.

Altair Forum User

Hi Sritej,

If you look at the FI, FI is usually a non linear function. It is recommended to look at SR which is similar to the safety margin.

SR= allowable load/actual load

Altair Forum User

Prakash: I am getting failure index of 9.72 (Max) and strength ratio is 1e8. What stress does it use (Normal, Principle, Von Mises for orthotropic material??). I also have honeycomb and a coating layer. In post processing, how can I look at these separately ?

Altair Forum User

Hi Sajid,

Different failure theories uses different stress types. For instance, Hill ply failure theory is deduced from VonMises theory. a failure index above 1.0 indicates that the allowable stress/strain has been exceeded.

Please refer to any theory book regarding failure indices for different failure theories.

Altair Forum User

Thank you Prakash. BTW, The reason for 1e8 index was due to RBE2 connections fyi.

Also, SR sometimes shows up in the output and when I make changes, it does not. Any thoughts I will appreciate. I have been manually putting-in CFAILURE=YES. I can't find a place in Hypermesh to specify it. Do you know ? Thanks again.

Altair Forum User

Hi Sajid,

CFAILURE is not available through GUI for now. You have to input it manually by editing the deck file.

Please let us know what are the changes you have made before SR turns off?

Altair Forum User

Hy Prakash,

I Have the same problem concerning composite failure calculation. Can show how this is edited Manually? This would be great.

Thanks in advance

Dean

Altair Forum User

Hi Dean3589,

Open the solver deck in notepad or any editor and add CFAILURE as shown in the image below:

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Thank you Prakash!

Altair Forum User

Hi Prakash,

I have changed the soolver deck, but I still can't choose the failure tab in the Hyperview.

Is there anything I have missed?

Kind regards for you help again

Dean

Altair Forum User

Dean,

Can you add DEBUG, COMPOUT, 3.0 in your solver deck and check if you are able to see any results?

Altair Forum User

Hi Prakash,

I have added DEBUG, COMPOUT, 3.0 in the solver deck but I still can't see any result unfortunately. I have attached the solver deck, so you can see for yourself.

Is it wrong if I am adding the missing commands after the first run of analysis in the solver deck. I am doing so because in my analysis there is no solver deck otherwise.

Again I would be very thankful for your help /emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20'>

Kind regards

Dean

Unable to find an attachment - read this blog

Altair Forum User

Hi Dean,

I will check and update to you soon.

thanks for sharing the file.

Altair Forum User

Hi Dean,

Is this the correct .fem deck?

I am asking because, I don't see any property in the solver deck.

Can you please check?

Altair Forum User

Hi Prakash,

this is the only fem.-file the analysis generates. If you open it with Microsoft notepad you see the following in the attached file.

Is the .fem file the right file you mean, the solver.deck?

Kind regards

Dean

<?xml version="1.0" encoding="UTF-8"?>

Altair Forum User

Dean,

Yes .fem is the solver deck. But when I open this in OptiStruct I dont see any property (PCOMPP) in your model or am I missing something?

Altair Forum User

Hi Prakash,

After I have optimized my structure, I analysed it, so I got a solver deck. After that I made my adjustments by inserting the needed code into the solver deck. now when I try to import the solver deck I get the following process message. 568d59ab3038d_ImportantProcessMessages.P

Could you explain the process after I have finished my optimization and before I start the analysis?

Thank you so much.

Dean

Altair Forum User

Anybody else who can help?

Rahul Rajan_21763

Hi,

You need to add cfailure as case unsupported card in hw 13 110

We changed the output request

Regards

Rahul R

Altair Forum User

Hi Dean,

Looks like the designvariables have same serial ID. HyperMesh has taken care of this by renumbering the designvariables when you import.

Altair Forum User

Thanks guys, now I get a failure solution in my anaylsis calculation.

Altair Forum User

i am facing the same problem.. neither i am getting the failure index values (plot is zero for all values) and SR.. i tried to input the CFAILURE in deck as you have shown above.. I am unable to get the FI and SR.. kindly help me with this

error message when i import solver deck:

Warning: Unsupported cards found in the I/O options section have been written as unsupported control card.
Summary:Feinput finished with 0 errors and 1 warnings.

Unable to find an attachment - read this blog

Rahul Rajan_21763

Composite ply failure indices output are controlled by CFAILURE keyword since v13.0 version. I see you are using 12.0 Version. Please give a try with latest version 14.0

Altair Forum User

ok sir.. but i am unable to obtain failure index and strength ratios atleast..

even they are compatible with only versions since v13?

Altair Forum User

Hi Nitish,

You need to request Composite FAILURE and Strength ratio through control cards.

To get Strength ratio output, Go to Control cards>> Global output request>> PARAM>> SRCOMPS.

Since you are using 13.0 you need to add CFAILURE manually. Edit the .fem file using any text editor and input as shown in the image:

<?xml version="1.0" encoding="UTF-8"?>