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Fatigue Load case i/p

Hello everyone,

For defining load in fatigue can I give displacement as in input in the static load case which is defined. I need to give certain amount of displacement for 1 lac cycles which is sinusoidal in nature.

Also,how can I give this 1 lac cycles as input? Do I have to manually do it in the .csv file and import it or can I define one sine wave have some kind of repeat command which will repeat the pattern of sine wave for rest of 99999 cycles? (like what is the tab 'repeat' is in fatigue manager?)

Regards,

Bharat

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Altair Forum User

Hi Bharat,

I dont think it is possible to have displacement based fatigue as the life prediction methods are stress based.

Do you see NC in MATFAT card?

hiranwale_bharat

Hello Prakash,

Yes I have seen NC in matfat card. But I am still curious about my second question regarding No. of cycles which are to be defined in load case(100000 no of sine waves are to be applied.)

Altair Forum User

Hi Baharat,

I dont see another way or work around to repeat the load except via excel file.

hiranwale_bharat

Ok prakash,

Thanks for the help.

Regards,

Bharat

hiranwale_bharat

Hello Prakash,

I guess we can do it in :FATSEQ' card.

Regards,

Bharat

Altair Forum User

Bharat,

Yes, but comment 2 says ' Repeat number (N#) has no effect on the results of a Factor of Safety (FOS) analysis'

Altair Forum User

If you are not interested in results you can go ahead for only life prediction.

hiranwale_bharat

Yes Prakash,

Now there is a catch there.

Thanks and regards,

Bharat.

Altair Forum User

@Prakash Pagadala

I did not get this point:

Yes, but comment 2 says ' Repeat number (N#) has no effect on the results of a Factor of Safety (FOS) analysis'

If you are not interested in results you can go ahead for only life prediction.

I did fatigue analysis on a component by both methods:

1. By increasing the number of cycles in .csv file

2. By changing N# (number of repeats in FATSEQ)

Results by both the methods are same i.e. Life and damage o/p is same.

Optistruct fatigue does not give any other o/p except these two stated above. How do we calculate FOS analysis?

Altair Forum User

Hi @bhumkaromkar

Goto Control cards>> Global output request>> FOS. This should output FoS for fatigue when you have a fatigue subcase.

Altair Forum User

@Prakash PagadalaThank you for the reply.

Can you also tell me if we can get other outputs too from this card for fatigue sub case?

Like stress , strain?

Altair Forum User

@Prakash Pagadala I created control card of Global output request for FOS. But when i review results in Hyperview it only shows Life and damage option. Where can i see FOS?

TIA

Altair Forum User

Hi,

Can you share the .out file?

Altair Forum User

@Prakash Pagadala I have sent you .out file on your File Transfer link. Kindly review the file.

TIA

Altair Forum User

@bhumkaromkar

Have you included torision fatigue limit, hydrostatic stress sensitivity value which are required for FOS in MATFAT?

Also, include the Dang Van criteria under FATPARAM. You need to add this manually in text editor.

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

Altair Forum User

@Prakash PagadalaWill do that....Thank you! /emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20' />