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Fatigue Analysis

I did the analysis using the hyperworks tutorial file for fatigue loading using the load time history file which was already there for the control arm.

Although I read the theory which was given in the tutorial before exercise but I am unable to understand the subcases, Load collector etc to be made before doing a fresh analysis and the meaning of the terms which are used for the same in given analysis. ie FATPARM, MATFAT, FATLOAD etc..

Thanks and regards

Bhavna

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Altair Forum User

Hi Bhavna,

FATPARM is used to define Fatigue analysis parameters like analysis type (strain life or stress life), fatigue strength formualtion (goodman, gerber, etc..)

MATFAT defines the fatigue material properties and the paramters are based on S-N curve

FATLOAD associates a static load with load-time history curve.

Altair Forum User

Hi Prakash

thanks for the explanation.

One more thing I am unable to decipher the variables which are used while defining material. I tried to find them out but couldn't. The variables are as follows:

SF, B,C EF, NP, KP, NC, SEE, SEP.

It is mentioned that the value of these variables can be obtained from materials EN curve.

Thanks and regards

Bhavna

Altair Forum User

Hi Bhavna,

EN curves are defined in Strain amplitudes. The total Strain is a sum of elastic and plastic components of the strain.

Please refer to the equation below on how fatigue strength coefficient, fatigue ductility coefficient, fatigue strength and ductility exponents are related. This will be useful if you are performing low-cycle fatigue analysis.

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

Rahul_P1

Bhavna,

Could you let us know where you encounter these variables and the name of the material you are using?

There is useful information about fatigue analysis in the HyperWorks student guide, chapter 2 - analysis types, page 25 onwards

Altair Forum User

Hi Rahul

I have enclosed the link as well as the path from where I encountered the same. I used aluminium as this was mentioned in the help file example.

Also I am unable to find the chapter you have mentioned. I have hyper mesh 13 Core tutorial.

HyperWorks Solvers > RADIOSS > Advanced Small Displacement Finite Element Analysis > RD-2080: Fatigue (Strain - Life) Method:
http://www.altairhyperworks.com/(S(3fu2zyrlbyi03xcofiue25jd))/hwhelp/Altair/hw11.0/help/hwtut/hwtut.htm?fatigue_en_strain.htm

thanks and regards

Bhavna

Rahul_P1

Bhavna,

HyperWorks help is comprehensive, You can always look up the definition of any material and its inputs in the help, the definitions for these variables are in the reference guide > inputs section,

Please see - Altair OptiStruct > Reference Guide > Input Data > Bulk Data Section > MATFAT

http://www.altairhyperworks.com/hwhelp/Altair/hw12.0/help/hwsolvers/hwsolvers.aspx?rd_theorymanual.htm

Altair Forum User

Hi Rahul

Thanks a lot I got what I needed.

Regards

Bhavna Uttamchandani

Altair Forum User

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