Fatigue analysis in Abaqus

[eric2010]

Hi

I am focusing my attention on the fatigue analysis in Abaqus. And in fact I am new to this section. There are 3 questions I want to ask some one do me a favor.

In the fatigue analysis section, the so called" direct cyclic method" has a limit on contact condition. I am a little confused about related scripting in "Abaqus analysis Manual 6.2.7 overview". It says the direct cyclic method
"assumes fixed contact conditions within each loading cycle."

1.Does this mean contact pairs in the FEM model will connect to each other rigidly in the direct cyclic analysis or something?

2. Actually, in "abaqus theory manual 2.2.3", it points out that convergence difficulty may happen if contact is included in the direct cyclic analysis, because of its severe nolinearity. Ironically, if the contact pairs are fixed as discribed in my first question, where does this severe nolinearity come from?

3. if I just neglect the above two questions, I want to use python to write my analysis file, however, I can not find the related sectence to activate the direct cyclic anaysis.It seems that the this direct cyclic analysis only exists in abaqus keywords such as"*direct cyclic", at least I am quite sure it is not supproted in Abaqus/CAE:
is this true?

Kindly regards! I really appreicate that if someone can give me an explanation!

ERIC

 

[amubashar]

The direct cyclic procedure is supported in Abaqus/CAE 6.10 where a direct cyclic step can be defined in step module. In previous versions, direct cyclic procedure has to be defined using keywords.

 

[eric2010]

Hi,
Thank you again.

And, if the "direct fatigue analysis" can not be supported in CAE in the versions before " abaqus 6.10", Does it mean that wrting python files in the previous version also can not realize the direct fatiuge analysis?

kindly regards!