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Mean stress correction

Hi,

I have a question about FKMMMS in MATFAT. It said that this number is used to calculate the fully reserved fatigue strength and then corrected value is used to choose the SN curve.

Does it mean that the SN curve is defined again after the stress calculation??? I really don't get it so well

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Altair Forum User

Hi @Toan Nguyen

Yes, the corrected value is used to choose the SN curve for damage and life.

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Hi Prakash,

this is where I am not really clear about. If I already have SRI1, b1, and NC1 (for 1 segment SN curve), why do I need FKMMMS. In my opinion, Those three parameters are enough to define an SN curve, right ???

Altair Forum User

@Toan Nguyen

You can use FKMMS to correct the curve when experimental data is not available by providing a mean correction factor.

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Hi Prakash,

If I defined the GOODMAN as my mean stress correction method in FATPARM and also define FKMMS in MATFAT, does that mean both these correction methods are used during the analysis ??

Altair Forum User

Hi,

I will check regarding this and update you soon.

Beta

Hi Prakash,

Any update on this??

Altair Forum User

Hi,

Sorry for a late reply. In that case, GOODMAN will be used and FKMMS will be ignored.

FKM mean stress correction is supported for Seam Weld Fatigue. Stress sensitivity can be defined on the MATFAT Bulk Data Entry via the FKMMSS_SM field. Mean stress correction for Seam Weld fatigue is disabled by default and can be enabled via the corresponding CORRECT field on the FATPARM Bulk Data Entry .

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Thank you, Prakash